阅读说明：本技术 变速器、以及工作车辆的控制系统 (Transmission and control system for work vehicle ) 是由 南贵信 于 2019-01-21 设计创作，主要内容包括：本发明提供一种变速器以及工作车辆的控制系统。第二要素固定离合器切换为分离状态和卡合状态。第二要素固定离合器在分离状态下,将行星齿轮机构的第二要素可旋转地分离。第二要素固定离合器在卡合状态下,将行星齿轮机构的第二要素不可旋转地固定。变速器通过将第二要素固定离合器切换为分离状态和卡合状态,而切换为第一无级变速模式、第二无级变速模式、以及直接模式之中的至少两种模式。(The invention provides a transmission and a control system for a work vehicle. The second element fixed clutch is switched between a disengaged state and an engaged state. The second element fixed clutch rotatably separates the second element of the planetary gear mechanism in a disengaged state. The second element fixed clutch fixes the second element of the planetary gear mechanism in a non-rotatable manner in an engaged state. The transmission is switched to at least two modes among a first continuously variable transmission mode, a second continuously variable transmission mode, and a direct mode by switching the second element fixed clutch between a disengaged state and an engaged state.)

1. A transmission that transmits a rotational force from an engine, comprising:

a first rotating shaft;

a second rotation shaft;

a first path arranged between the first rotating shaft and the second rotating shaft on a transmission path of a rotational force from the engine;

a second path that includes a continuously variable transmission having a motor and a power source that drives the motor, and that is connected in parallel with respect to the first path;

a planetary gear mechanism comprising: a first element connected to the first path, a second element connected to the second path, and a third element connected to the first rotating shaft or the second rotating shaft;

a second element fixed clutch that is switched between a disengaged state in which the second element is rotatably disengaged and an engaged state in which the second element is non-rotatably fixed;

the transmission is switched to at least two modes among a first continuously variable transmission mode, a second continuously variable transmission mode, and a direct mode by switching the second element fixed clutch between the disengaged state and the engaged state,

in the first stepless speed change mode, the rotational force from the engine is transmitted from the first rotational shaft to the second rotational shaft not via the first path but via the second path,

in the second continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft via both the first path and the second path,

in the direct mode, the rotational force from the engine is transmitted from the first rotational shaft to the second rotational shaft not via the second path but via the first path.

2. The transmission of claim 1,

the transmission transmits the rotational force from the engine in the second continuously variable transmission mode with the second element fixed clutch disengaged,

the torque from the engine is transmitted in the direct mode in a state where the second element fixed clutch is engaged.

3. The transmission of claim 1 or 2,

the first path includes: a first shaft portion, a second shaft portion, and a first path cutoff clutch disposed between the first shaft portion and the second shaft portion,

the first path cutoff clutch disconnects the first shaft portion and the second shaft portion in a disengaged state and connects the first shaft portion and the second shaft portion in an engaged state,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where both the second element fixed clutch and the first path-cutoff clutch are disengaged,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where the second element fixed clutch is disengaged and the first path cutoff clutch is engaged,

the direct mode transmits the rotational force from the engine in a state where both the second element fixed clutch and the first path cutoff clutch are engaged.

4. The transmission of claim 3,

further comprising a first element fixed clutch which is switched between a disengaged state in which the first element is rotatably disengaged and an engaged state in which the first element is non-rotatably fixed,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the second element fixed clutch and the first path-cutoff clutch are both disengaged and the first element fixed clutch is engaged,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where both the second element fixed clutch and the first element fixed clutch are disengaged and the first path cutoff clutch is engaged,

the direct mode transmits the rotational force from the engine when both the second element fixed clutch and the first path cutoff clutch are in the engaged state and the first element fixed clutch is in the disengaged state.

5. The transmission of claim 3,

further comprising an element coupling clutch that switches between an engaged state in which any two elements among the first element, the second element, and the third element are coupled and a disengaged state in which the first element, the second element, and the third element are not coupled,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the second element fixed clutch and the first path cutoff clutch are both disengaged and the element connection clutch is engaged,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where both the second element fixed clutch and the element coupling clutch are disengaged and the first path cutoff clutch is engaged,

the direct mode transmits the rotational force from the engine when both the second element fixed clutch and the first path cutoff clutch are in the engaged state and the element connection clutch is in the disengaged state.

6. The transmission of claim 1,

the first path includes: a first shaft portion, a second shaft portion, and a first path cutoff clutch disposed between the first shaft portion and the second shaft portion,

the first path cutoff clutch disconnects the first shaft portion and the second shaft portion in a disengaged state and connects the first shaft portion and the second shaft portion in an engaged state,

further comprising:

a bypass path that connects the second path with the first rotation shaft or the second rotation shaft without via the planetary gear mechanism;

a bypass clutch that switches connection and disconnection between the first rotating shaft or the second rotating shaft and the bypass path;

in the first continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the first path and the planetary gear mechanism but via the second path and the bypass path,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the second element fixed clutch and the first path cutoff clutch are both disengaged and the bypass clutch is engaged,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where the second element fixed clutch and the bypass clutch are both disengaged and the first path cutoff clutch is engaged,

the direct mode transmits the rotational force from the engine when both the second element fixed clutch and the first path cutoff clutch are in the engaged state and the bypass clutch is in the disengaged state.

7. A transmission that transmits a rotational force from an engine, comprising:

a first rotating shaft;

a second rotation shaft;

a first path arranged between the first rotating shaft and the second rotating shaft on a transmission path of a rotational force from the engine;

a second path that includes a continuously variable transmission having a motor and a power source that drives the motor, and that is connected in parallel with respect to the first path;

a planetary gear mechanism comprising: a first element connected to the first path, a second element connected to the second path, and a third element connected to the first rotating shaft or the second rotating shaft;

an element connection clutch that switches between an engaged state in which any two elements among the first element, the second element, and the third element are connected and a disengaged state in which the first element, the second element, and the third element are not connected;

the transmission is switched to at least two modes among a first continuously variable transmission mode, a second continuously variable transmission mode, and a direct mode by switching the element connection clutch between the disengaged state and the engaged state,

in the first stepless speed change mode, the rotational force from the engine is transmitted from the first rotational shaft to the second rotational shaft not via the first path but via the second path,

in the second continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft via both the first path and the second path,

in the direct mode, the rotational force from the engine is transmitted from the first rotational shaft to the second rotational shaft not via the second path but via the first path.

8. The transmission of claim 7,

the transmission transmits the rotational force from the engine in the second continuously variable transmission mode with the element coupling clutch disengaged,

the torque from the engine is transmitted in the direct mode in a state where the element coupling clutch is engaged.

9. The transmission of claim 7 or 8,

the first path includes: a first shaft portion, a second shaft portion, and a first path cutoff clutch disposed between the first shaft portion and the second shaft portion,

the first path cutoff clutch disconnects the first shaft portion and the second shaft portion in a disengaged state and connects the first shaft portion and the second shaft portion in an engaged state,

further comprising a first element fixed clutch which is switched between a disengaged state in which the first element is rotatably disengaged and an engaged state in which the first element is non-rotatably fixed,

the transmission transmits the rotational force from the engine in the first stepless shift mode when the element connection clutch and the first path disconnection/connection clutch are both in the disconnected state and the first element fixed clutch is in the engaged state, or transmits the rotational force from the engine in the first stepless shift mode when the first element fixed clutch and the first path disconnection/connection clutch are both in the disconnected state and the element connection clutch is in the engaged state,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where both the first element fixed clutch and the element coupling clutch are disengaged and the first path cutoff clutch is engaged,

the direct mode transmits the rotational force from the engine in a state where the first path cutoff clutch and the element connection clutch are both engaged and the first element fixed clutch is disengaged.

10. The transmission of claim 7 or 8,

the first path includes: a first shaft portion, a second shaft portion, and a first path cutoff clutch disposed between the first shaft portion and the second shaft portion,

the first path cutoff clutch disconnects the first shaft portion and the second shaft portion in a disengaged state and connects the first shaft portion and the second shaft portion in an engaged state,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the first path cutoff clutch is disengaged and the element coupling clutch is engaged,

the torque from the engine is transmitted in the second continuously variable transmission mode in a state where the element coupling clutch is in a disengaged state and the first path cutoff clutch is in an engaged state.

11. The transmission of claim 10,

the transmission transmits the rotational force from the engine in the direct mode in a state where both the first path cutoff clutch and the element coupling clutch are engaged.

12. The transmission of claim 7 or 8,

the first path includes: a first shaft portion, a second shaft portion, and a first path cutoff clutch disposed between the first shaft portion and the second shaft portion,

the first path cutoff clutch disconnects the first shaft portion and the second shaft portion in a disengaged state and connects the first shaft portion and the second shaft portion in an engaged state,

further comprising:

a bypass path that connects the second path to the first rotating shaft or the second rotating shaft without passing through the planetary gear mechanism;

a bypass clutch that switches connection and disconnection between the first rotating shaft or the second rotating shaft and the bypass path;

in the first continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the first path and the planetary gear mechanism but via the second path and the bypass path,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the element connection clutch and the first path disconnection clutch are both in a disengaged state and the bypass clutch is in an engaged state,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where both the element coupling clutch and the bypass clutch are disengaged and the first path cutoff clutch is engaged,

the direct mode transmits the rotational force from the engine when both the element coupling clutch and the first path cutoff clutch are in the engaged state and the bypass clutch is in the disengaged state.

13. The transmission of claim 7 or 8,

the first path includes: a first shaft portion, a second shaft portion, and a first path cutoff clutch disposed between the first shaft portion and the second shaft portion,

the first path cutoff clutch disconnects the first shaft portion and the second shaft portion in a disengaged state and connects the first shaft portion and the second shaft portion in an engaged state,

further comprising:

a bypass path that connects the second path to the first rotating shaft or the second rotating shaft without passing through the planetary gear mechanism;

a bypass clutch that switches connection and disconnection between the first rotating shaft or the second rotating shaft and the bypass path;

in the first stepless speed change mode, the rotational force from the engine is transmitted from the first rotational shaft to the second rotational shaft not via the first path but via the second path and the planetary gear mechanism,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the bypass clutch and the first path cutoff clutch are both disengaged and the element connection clutch is engaged,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where both the element coupling clutch and the bypass clutch are disengaged and the first path cutoff clutch is engaged,

the direct mode transmits the rotational force from the engine when both the element coupling clutch and the first path cutoff clutch are in the engaged state and the bypass clutch is in the disengaged state.

14. A transmission that transmits a rotational force from an engine, comprising:

a first rotating shaft;

a second rotation shaft;

a first path arranged between the first rotating shaft and the second rotating shaft on a transmission path of a rotational force from the engine;

a second path that includes a continuously variable transmission having a motor and a power source that drives the motor, and that is connected in parallel with respect to the first path;

a planetary gear mechanism comprising: a first element connected to the first path, a second element connected to the second path, and a third element connected to the first rotating shaft or the second rotating shaft;

the first path includes: a first shaft portion, a second shaft portion, and a first path cutoff clutch disposed between the first shaft portion and the second shaft portion,

the first path cutoff clutch disconnects the first shaft portion and the second shaft portion in a disengaged state and connects the first shaft portion and the second shaft portion in an engaged state,

the transmission is switched to at least two modes among a first continuously variable transmission mode, a second continuously variable transmission mode, and a direct mode by switching the first path cutoff clutch to the disengaged state and the engaged state,

in the first stepless speed change mode, the rotational force from the engine is transmitted from the first rotational shaft to the second rotational shaft not via the first path but via the second path,

in the second continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft via both the first path and the second path,

in the direct mode, the rotational force from the engine is transmitted from the first rotational shaft to the second rotational shaft not via the second path but via the first path.

15. The transmission of claim 14,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the first path-cutoff clutch is disengaged,

the second continuously variable transmission mode transmits the rotational force from the engine in the engaged state of the first path cutoff clutch.

16. The transmission of claim 14 or 15,

further comprising a first element fixed clutch which is switched between a disengaged state in which the first element is rotatably disengaged and an engaged state in which the first element is non-rotatably fixed,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the first path cutoff clutch is disengaged and the first element fixed clutch is engaged,

the torque from the engine is transmitted in the second continuously variable transmission mode in a state where the first path cutoff clutch is in an engaged state and the first element fixed clutch is in a disengaged state.

17. The transmission of claim 13 or 14, further comprising:

a bypass path that connects the second path to the first rotating shaft or the second rotating shaft without passing through the planetary gear mechanism;

a bypass clutch that switches connection and disconnection between the first rotating shaft or the second rotating shaft and the bypass path;

in the first continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the first path and the continuously variable transmission but via the second path and the bypass path,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the first path cutoff clutch is disengaged and the bypass clutch is engaged,

the second continuously variable transmission mode transmits the rotational force from the engine in a state where the first path cutoff clutch is in an engaged state and the bypass clutch is in a disengaged state.

18. The transmission of claim 13 or 14, further comprising:

a direct path that connects the first rotating shaft and the second rotating shaft without passing through the first path, the second path, and the planetary gear mechanism;

a direct clutch that switches connection and disconnection of the first rotation shaft or the second rotation shaft with and from the direct path,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where both the first path cutoff clutch and the direct clutch are disengaged,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where the first path-cut clutch is in an engaged state and the direct clutch is in a disengaged state,

the direct mode transmits the rotational force from the engine in the direct mode in a state where the direct clutch is engaged.

19. The transmission of claim 18,

further comprising a first element fixed clutch which is switched between a disengaged state in which the first element is rotatably disengaged and an engaged state in which the first element is non-rotatably fixed,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the first path cutoff clutch and the direct clutch are both disengaged and the first element fixed clutch is engaged,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where the first path cutoff clutch is in an engaged state and both the direct clutch and the first element fixed clutch are in a disengaged state,

the direct mode is a mode in which the direct clutch is engaged while the first element fixed clutch or the first path cutoff clutch is disengaged.

20. The transmission of claim 18,

further comprising an element coupling clutch that switches between an engaged state in which any two elements among the first element, the second element, and the third element are coupled and a disengaged state in which the first element, the second element, and the third element are not coupled,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the first path cutoff clutch and the direct clutch are both in a disengaged state and the element connection clutch is in an engaged state,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where the first path-cutoff clutch is in an engaged state and both the direct clutch and the element connection clutch are in a disengaged state,

the direct mode transmits the rotational force from the engine when the element connection clutch or the first path disconnection clutch is in a disengaged state and the direct clutch is in an engaged state.

21. The transmission of claim 18, further comprising:

a bypass path that connects the second path to the first rotating shaft or the second rotating shaft without passing through the planetary gear mechanism;

a bypass clutch that switches connection and disconnection between the first rotating shaft or the second rotating shaft and the bypass path;

in the first continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the first path and the planetary gear mechanism but via the second path and the bypass path,

the transmission transmits the rotational force from the engine in the first continuously variable transmission mode in a state where the first path cutoff clutch and the direct clutch are both in a disengaged state and the bypass clutch is in an engaged state,

transmitting a rotational force from the engine in the second continuously variable transmission mode in a state where the first path cutoff clutch is in an engaged state and both the direct clutch and the bypass clutch are in a disengaged state,

the direct mode is a mode in which the rotational force from the engine is transmitted when the bypass clutch or the first path cutoff clutch is in a disengaged state and the direct clutch is in an engaged state.

22. A control system for a work vehicle, comprising:

the engine;

the transmission of any one of claims 1 to 21;

a rotational speed sensor that outputs a signal representing an output rotational speed of the transmission;

a controller that receives a signal from the rotational speed sensor and controls the transmission;

the controller switches at least two modes among the first continuously variable mode, the second continuously variable mode, and the direct mode according to an output rotational speed of the transmission.

Technical Field

The invention relates to a transmission and a control system of a work vehicle.

Background

As one of the transmissions, there is an HST (hydrostatic transmission). The HST includes a hydraulic pump and a hydraulic motor. The hydraulic pump is driven by the engine and discharges hydraulic oil. The hydraulic motor is driven by working oil from the hydraulic pump. In the HST, the reduction ratio can be steplessly changed by controlling the displacement of the hydraulic pump and the displacement of the hydraulic motor.

Since the HST is a continuously variable transmission, there is less concern that articles may fall off due to shift shock, and it is desired to obtain high efficiency in a low speed region. However, since the hydraulic motor operates at a high speed in a high speed region, more engine output is used, and therefore, efficiency is reduced.

Therefore, in recent years, a transmission combining an HST and a mechanical transmission is known. For example, in the transmission described in patent document 1, HST is used in a low speed region, and direct transmission by a mechanical transmission is used in a high speed region. This can improve the efficiency in the high-speed region.

In the transmission described in patent document 2, an HMT (hydro-mechanical continuously variable transmission) and a mechanical transmission can be switched. Alternatively, an EMT (electro-mechanical transmission) using a continuously variable transmission including a generator and an electric motor instead of the HST is also known.

Disclosure of Invention

Technical problem to be solved by the invention

In the transmission, a first continuously variable mode using the HST and a direct mode using the mechanical transmission are switched. Or switching between the second continuously variable mode using HMT and the direct mode. Therefore, a transmission capable of easily and smoothly switching between a plurality of modes is required.

Technical solution for solving technical problem

The transmission of the first mode includes: the planetary gear mechanism includes a first rotating shaft, a second rotating shaft, a first path, a second path, a planetary gear mechanism, and a second element fixed clutch. The first path is disposed between the first rotation shaft and the second rotation shaft on a transmission path of the rotational force from the engine. The second path includes a continuously variable transmission having a motor and a power source that drives the motor, and is connected in parallel with respect to the first path. The planetary gear mechanism includes: a first element connected to the first path, a second element connected to the second path, and a third element connected to the first rotating shaft or the second rotating shaft.

The second element fixed clutch is switched between a disengaged state and an engaged state. The second element fixed clutch rotatably separates the second element in a separated state. The second element fixed clutch fixes the second element in a non-rotatable manner in an engaged state.

The transmission is switched to at least two modes among a first continuously variable transmission mode, a second continuously variable transmission mode, and a direct mode by switching the second element fixed clutch between a disengaged state and an engaged state. In the first stepless speed change mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the first path but via the second path. In the second continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft via both the first path and the second path. In the direct mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the second path but via the first path.

The transmission of the second mode includes: the planetary gear mechanism includes a first rotating shaft, a second rotating shaft, a first path, a second path, a planetary gear mechanism, and an element coupling clutch. The first path is disposed between the first rotation shaft and the second rotation shaft on a transmission path of the rotational force from the engine. The second path includes a continuously variable transmission having a motor and a power source that drives the motor, and is connected in parallel with respect to the first path. The planetary gear mechanism includes: a first element connected to the first path, a second element connected to the second path, and a third element connected to the first rotating shaft or the second rotating shaft.

The element connection clutch is switched between a disengaged state and an engaged state. The element connection clutch connects any two elements of the first element, the second element, and the third element in an engaged state. The element connection clutch disconnects the first element, the second element, and the third element in the disengaged state.

The transmission is switched to at least two modes among a first continuously variable transmission mode, a second continuously variable transmission mode, and a direct mode by switching the clutching clutch to a disengaged state and an engaged state. In the first stepless speed change mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the first path but via the second path. In the second continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft via both the first path and the second path. In the direct mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the second path but via the first path.

The transmission of the third mode includes: a first rotation shaft, a second rotation shaft, a first path, a second path, and a planetary gear mechanism. The first path is disposed between the first rotation shaft and the second rotation shaft on a transmission path of the rotational force from the engine. The second path includes a continuously variable transmission having a motor and a power source that drives the motor, and is connected in parallel with respect to the first path. The planetary gear mechanism includes: a first element connected to the first path, a second element connected to the second path, and a third element connected to the first rotating shaft or the second rotating shaft.

The first path includes: the clutch includes a first shaft portion, a second shaft portion, and a first path cutoff clutch disposed between the first shaft portion and the second shaft portion. The first path cutoff clutch is switched between a disengaged state and an engaged state. The first path cutoff clutch disconnects the first shaft portion and the second shaft portion in the disengaged state. The first path cutoff clutch connects the first shaft portion and the second shaft portion in the engaged state.

The transmission is switched to at least two modes among a first continuously variable mode, a second continuously variable mode, and a direct mode by switching the first path cutoff clutch to the disengaged state and the engaged state. In the first stepless speed change mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the first path but via the second path. In the second continuously variable transmission mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft via both the first path and the second path. In the direct mode, the rotational force from the engine is transmitted from the first rotary shaft to the second rotary shaft not via the second path but via the first path.

A control system for a work vehicle according to a fourth aspect includes: the engine, the transmission, the rotational speed sensor, and the controller. The rotational speed sensor outputs a signal indicative of an output rotational speed of the transmission. The controller receives a signal from the rotational speed sensor and controls the transmission. The controller switches at least two modes among the first continuously variable mode, the second continuously variable mode, and the direct mode according to an output rotation speed of the transmission.

Effects of the invention

In the transmission according to the present invention, switching between a plurality of modes can be easily and smoothly performed.

Drawings

Fig. 1 is a side view of a work vehicle of the embodiment.

Fig. 2 is a block diagram showing the configuration of a control system of the work vehicle.

Fig. 3 is a schematic diagram showing the configuration and control of the transmission of the first embodiment.

Fig. 4 is a schematic diagram showing the configuration and control of a transmission according to a first modification of the first embodiment.

Fig. 5 is a schematic diagram showing the configuration and control of a transmission according to a second modification of the first embodiment.

Fig. 6 is a schematic diagram showing the configuration and control of a transmission according to a third modification of the first embodiment.

Fig. 7 is a schematic diagram showing the configuration and control of a transmission of the second embodiment.

Fig. 8 is a schematic diagram showing the configuration and control of a transmission according to a first modification of the second embodiment.

Fig. 9 is a schematic diagram showing a configuration and control of a transmission according to a second modification of the second embodiment.

Fig. 10 is a schematic diagram showing the configuration and control of a transmission according to a third modification of the second embodiment.

Fig. 11 is a schematic diagram showing the configuration and control of a transmission of the third embodiment.

Fig. 12 is a schematic diagram showing the configuration and control of a transmission according to a first modification of the third embodiment.

Fig. 13 is a schematic diagram showing the configuration and control of a transmission according to a second modification of the third embodiment.

Fig. 14 is a schematic diagram showing a configuration and control of a transmission according to a third modification of the third embodiment.

Fig. 15 is a schematic diagram showing the configuration and control of a transmission according to a fourth modification of the third embodiment.

Fig. 16 is a schematic diagram showing the configuration and control of a transmission according to a fifth modification of the third embodiment.

Fig. 17 is a schematic diagram showing the structure and control of a transmission according to another embodiment.

Fig. 18 is a schematic diagram showing the structure and control of a transmission of another embodiment.

Fig. 19 is a schematic diagram showing the structure and control of a transmission of another embodiment.

Fig. 20 is a schematic diagram showing the structure and control of a transmission of another embodiment.

Fig. 21 is a schematic diagram showing the structure and control of a transmission according to another embodiment.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 is a side view of a work vehicle 1 according to an embodiment of the present invention. Fig. 2 is a block diagram showing the configuration of the control system of the work vehicle 1. As shown in fig. 1, the work vehicle 1 includes: vehicle body frame 2, running wheels 4, 5, work implement 3, cab 6, engine 7, and transmission 8 a.

The vehicle body frame 2 has a front frame 28 and a rear frame 29. The front frame 28 is mounted forward of the rear frame 29. The front frame 28 is rotatably coupled to the rear frame 29. The running wheels 4, 5 comprise front wheels 4 and rear wheels 5. The front wheel 4 is rotatably mounted to the front frame 28. A rear wheel 5 is rotatably mounted to the rear frame 29.

The work vehicle 1 can perform work such as excavation using the work implement 3. The working device 3 is driven by working oil from a working device pump 15 shown in fig. 2. The work device 3 has an arm 11 and a bucket 12. The working device 3 has hydraulic cylinders 13, 14. The hydraulic cylinders 13 and 14 extend and contract by hydraulic oil from a work implement pump 15, thereby operating the arm 11 and the bucket 12.

The cab 6 is mounted on the vehicle body frame 2. A seat on which an operator sits, an operation device 21 shown in fig. 2, and the like are disposed in the cab 6. The operation device 21 includes, for example, a joystick, a pedal, a switch, and the like. The engine 7 and the transmission 8a are mounted on the vehicle body frame 2. The engine 7 is, for example, a diesel engine. The transmission 8a transmits the rotational force from the engine 7 to the running wheels 4, 5. Thus, the work vehicle 1 travels by rotationally driving the running wheels 4 and 5.

As shown in fig. 2, the work vehicle 1 includes a work implement control valve 16. The work implement control valve 16 controls the flow rate of the working oil supplied from the work implement pump 15 to the hydraulic cylinders 13 and 14. The control system of the work vehicle 1 includes a controller 20. The controller 20 includes: a processor such as a CPU, and storage devices such as RAM and ROM. The controller 20 controls the working device 3 by controlling the working device control valve 16 according to the operation of the operation device 21. The controller 20 controls the engine 7 and the transmission 8a according to the operation of the operation device 21.

Next, the transmission 8a will be described in detail. The transmission 8a of the present embodiment is a transmission in which an HST and a mechanical transmission are combined.

Fig. 3A is a schematic diagram showing the structure of a transmission 8a of the first embodiment. As shown in fig. 3A, the transmission 8a includes: the input shaft 31, the first rotation shaft 32, the second rotation shaft 33, the output shaft 37, the first path 34, the second path 35, the planetary gear mechanism 36, and the second element fixed clutch CL 1.

The rotational force from the engine 7 is input to the input shaft 31. The first rotation shaft 32 is connected to the input shaft 31. The first rotation shaft 32 may be integrated with the input shaft 31. Alternatively, the first rotating shaft 32 may be connected to the input shaft 31 via a gear or a clutch. The second rotation shaft 33 is connected to an output shaft 37. The second rotation shaft 33 may be integrated with the output shaft 37. Alternatively, the second rotary shaft 33 may be connected to the output shaft 37 via a gear or a clutch.

The first path 34 is disposed between the first rotating shaft 32 and the second rotating shaft 33 on a transmission path of the rotational force from the engine 7. The first path 34 is connected to the first rotation shaft 32.

The second path 35 is connected in parallel with respect to the first path 34. The second path 35 includes a continuously variable transmission 38. Continuously variable transmission 38 has a motor 41 and a power source 42. In the present embodiment, the continuously variable transmission 38 is an HST, the motor 41 is a hydraulic motor, and the power source 42 is a hydraulic pump. The motor 41 is driven by the working oil discharged from the power source 42. The power source 42 is connected to the first rotary shaft 32 via a gear.

The planetary gear mechanism 36 includes: a sun gear as a first element 43, an external gear as a second element 44, a carrier as a third element 45, and a plurality of planetary gears 46. The first element 43 is connected to the first path 34. The second element 44 is connected to the second path 35. Specifically, the second element 44 is connected to the motor 41. The third element 45 is connected to the second rotation shaft 33. The first element 43, the second element 44, and the third element 45 are not limited to the sun gear, the external gear, and the carrier, and may be modified.

The second element fixed clutch CL1 is connected to the second element 44. The second element fixed clutch CL1 is switched between the disengaged state and the engaged state. The second element fixed clutch CL1 rotationally separates the second element 44 in the disengaged state. The second element fixed clutch CL1 fixes the second element 44 in an engaged state, so as not to rotate. For example, the second element fixed clutch CL1 fixes the second element 44 to the case of the transmission 8a in the engaged state, thereby making the second element 44 non-rotatable.

The transmission 8a is switched to at least two modes among the first continuously variable mode, the second continuously variable mode, and the direct mode. In the first stepless shift mode, the rotational force from the engine 7 is transmitted from the first rotary shaft 32 to the second rotary shaft 33 not via the first path 34 but via the second path 35. In the second continuously variable transmission mode, the rotational force from the engine 7 is transmitted from the first rotary shaft 32 to the second rotary shaft 33 via both the first path 34 and the second path 35. In the direct mode, the rotational force from the engine 7 is transmitted from the first rotation shaft 32 to the second rotation shaft 33 not via the second path 35 but via the first path 34.

In the first embodiment, the transmission 8a is switched between the second continuously variable transmission mode and the direct mode by switching the engagement state and the disengagement state of the second element fixed clutch CL 1. Fig. 3B is a table showing the relationship between the mode of the transmission 8a and the state of the second element fixed clutch CL 1. As shown in fig. 3B, the transmission 8a transmits the rotational force from the engine 7 in the second continuously variable transmission mode with the second element fixed clutch CL1 disengaged. The transmission 8a transmits the rotational force from the engine 7 in the direct mode with the second element fixed clutch CL1 engaged.

As shown in fig. 2, the work vehicle 1 includes a rotational speed sensor 17. The rotational speed sensor 17 outputs a signal indicating the output rotational speed of the transmission 8 a. The controller 20 receives a signal from the rotational speed sensor 17 and controls the transmission 8 a.

In detail, the work vehicle 1 includes a transmission pump 18 and a clutch control valve 19. The transmission pump 18 discharges the working oil by being driven by the engine 7. The second element fixed clutch CL1 is a hydraulic clutch, and the clutch control valve 19 controls the hydraulic pressure supplied from the transmission pump 18 to the second element fixed clutch CL 1. However, the second element fixed clutch CL1 may be electrically controlled.

The controller 20 controls the clutch control valve 19 to switch the engagement state and the disengagement state of the second element fixed clutch CL 1. The controller 20 switches the second continuously variable transmission mode and the direct mode according to the output rotational speed of the transmission 8 a. For example, when the output rotational speed of the transmission 8a is less than a predetermined threshold value, the controller 20 sets the second element fixed clutch CL1 to the disengaged state. Thereby, the transmission 8a transmits the rotational force from the engine 7 in the second continuously variable transmission mode.

When the output rotational speed of the transmission 8a is equal to or higher than a predetermined threshold value, the controller 20 brings the second element fixed clutch CL1 into an engaged state. Thereby, the transmission 8a transmits the rotational force from the engine 7 in the direct mode.

In the transmission 8a of the first embodiment as described above, the mode of the transmission 8a can be switched between the second continuously variable transmission mode and the direct mode by switching between the fixing and releasing of the second element 44 of the planetary gear mechanism 36 by the second element fixing clutch CL 1. This allows easy and smooth switching between modes.

In the direct mode, the second element 44 of the planetary gear mechanism 36 is fixed by the second element fixing clutch CL 1. Therefore, the second element 44 can be prevented from rotating together with the motor 41. This can improve the transmission efficiency of the rotational force in the transmission 8 a.

Further, since switching between the modes can be realized with a simple configuration, the transmission 8a can be downsized.

Next, a first modification of the first embodiment will be described. Fig. 4A is a schematic diagram showing a configuration of a transmission 8b according to a first modification of the first embodiment. Fig. 4B is a table showing the relationship between the mode of the transmission 8B and the state of the clutch.

The transmission 8b further includes a first path cutoff clutch CL2 and a first element fixed clutch CL 3. The first path 34 includes a first shaft portion 34a and a second shaft portion 34b, and the first path cutoff clutch CL2 is disposed between the first shaft portion 34a and the second shaft portion 34 b. The first shaft portion 34a is connected to the first rotation shaft 32. The second shaft portion 34 is connected to the first element 43. The first path cutoff clutch CL2 disconnects the first shaft portion 34a and the second shaft portion 34b in the disconnected state. The first path cutoff clutch CL2 connects the first shaft portion 34a and the second shaft portion 34b in an engaged state.

The first element fixed clutch CL3 is switched between the disengaged state and the engaged state. The first element fixed clutch CL3 rotationally separates the first element 43 in the separated state. The first element fixed clutch CL3 fixes the first element 43 in an engaged state, but not rotatably. For example, the first element fixed clutch CL3 fixes the first element 43 to the case of the transmission 8b in a non-rotatable manner in the engaged state.

As shown in fig. 4B, the transmission 8B transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where the second element fixed clutch CL1 and the first path cutoff clutch CL2 are both in the disengaged state and the first element fixed clutch CL3 is in the engaged state. The transmission 8b transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the second element fixed clutch CL1 and the first element fixed clutch CL3 are both in the disengaged state and the first path cutoff clutch CL2 is in the engaged state. The transmission 8b transmits the rotational force from the engine 7 in the direct mode in a state where the second element fixed clutch CL1 and the first path cutoff clutch CL2 are both engaged and the first element fixed clutch CL3 is disengaged.

The controller 20 controls the first element fixed clutch CL3 and the first path cutoff clutch CL2 in the same manner as the second element fixed clutch CL 1. The controller 20 can switch the transmission 8b to the first continuously variable shift mode, the second continuously variable shift mode, and the direct mode by controlling the first element fixed clutch CL3, the second element fixed clutch CL1, and the first path cutoff clutch CL2 as described above.

When the output rotational speed of the transmission 8b is less than a predetermined first threshold value, the controller 20 puts the transmission 8b into the first continuously variable mode. When the output rotational speed of the transmission 8b is equal to or higher than a predetermined first threshold value and lower than a predetermined second threshold value, the controller 20 sets the transmission 8b in the second continuously variable transmission mode. When the output rotational speed of the transmission 8b is equal to or higher than a predetermined second threshold value, the controller 20 puts the transmission 8b into the direct mode. The other structures are the same as those of the transmission 8a of the first embodiment described above.

Next, a second modification of the first embodiment will be described. Fig. 5A is a schematic diagram showing a configuration of a transmission 8c according to a second modification of the first embodiment. Fig. 5B is a table showing the relationship between the mode of the transmission 8c and the state of the clutch.

The transmission 8c includes an element coupling clutch CL4 instead of the first element fixed clutch CL3 in the first modification. The element connection clutch CL4 is connected to the second element 44 and the third element 45 of the planetary gear mechanism 36. The element connection clutch CL4 connects the second element 44 to the third element 45 in the engaged state. Thereby, the second element 44 and the third element 45 are integrally rotated. The element connection clutch CL4 disconnects the second element 44 from the third element 45 in the disengaged state.

As shown in fig. 5B, the transmission 8c transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where the second element fixed clutch CL1 and the first path cutoff clutch CL2 are both in the disengaged state and the element connection clutch CL4 is in the engaged state. The transmission 8c transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the second element fixed clutch CL1 and the element coupling clutch CL4 are both in the disengaged state and the first path cutoff clutch CL2 is in the engaged state. The transmission 8c transmits the rotational force from the engine 7 in the direct mode in a state where the second element fixed clutch CL1 and the first path cutoff clutch CL2 are both engaged and the element connection clutch CL4 is disengaged.

The controller 20 controls the element connection clutch CL4 in the same manner as the second element fixed clutch CL1 and the first element fixed clutch CL 3. The controller 20 can switch the transmission 8c to the first continuously variable transmission mode, the second continuously variable transmission mode, and the direct mode by controlling the second element fixed clutch CL1, the first path cutoff clutch CL2, and the element connection clutch CL4 as described above. The other configurations and mode switching control are the same as those of the transmissions 8a and 8 b.

Next, a third modification of the first embodiment will be described. Fig. 6A is a schematic diagram showing a configuration of a transmission 8d according to a third modification of the first embodiment. Fig. 6B is a table showing the relationship between the mode of the transmission 8d and the state of the clutch.

The transmission 8d includes a bypass clutch CL5 instead of the first element fixed clutch CL3 of the first modification. In addition, the transmission 8d includes a bypass path 48. The bypass path 48 connects the second path 35 to the second rotation shaft 33 without passing through the planetary gear mechanism 36. Specifically, the bypass passage 48 is provided in parallel with the first passage 34. The bypass path 48 is connected to the motor 41 via a gear. The bypass passage 48 is connected to the second rotary shaft 33 via a gear and a bypass clutch CL 5. The bypass clutch CL5 connects the second rotation shaft 33 and the bypass passage 48 in the engaged state. The bypass clutch CL5 disconnects the second rotating shaft 33 from the bypass path 48 in the disengaged state.

As shown in fig. 6B, the transmission 8d transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where the second element fixed clutch CL1 and the first path cutoff clutch CL2 are both in the disengaged state and the bypass clutch CL5 is in the engaged state. In the first stepless shift mode, the rotational force from the engine 7 is transmitted from the first rotary shaft 32 to the second rotary shaft 33 via the second path 35 and the bypass path 48, not via the first path 34 and the planetary gear mechanism 36.

The transmission 8d transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the second element fixed clutch CL1 and the bypass clutch CL5 are both in the disengaged state and the first path cutoff clutch CL2 is in the engaged state. The transmission 8d transmits the rotational force from the engine 7 in the direct mode in a state where the second element fixed clutch CL1 and the first path cutoff clutch CL2 are both engaged and the bypass clutch CL5 is disengaged.

The controller 20 controls the bypass clutch CL5 in the same manner as the second element fixed clutch CL1 and the first element fixed clutch CL. The controller 20 can switch the transmission 8d to the first continuously variable transmission mode, the second continuously variable transmission mode, and the direct mode by controlling the second element fixed clutch CL1, the first path cutoff clutch CL2, and the bypass clutch CL5 as described above. The other configurations and mode switching control are the same as those of the transmissions 8a to 8c described above.

Next, the transmission 8e of the second embodiment will be described. Fig. 7A is a schematic diagram showing the structure of a transmission 8e of the second embodiment. Fig. 7B is a table showing the relationship between the mode of the transmission 8e and the state of the clutch.

As shown in fig. 7A, the transmission 8e includes an element coupling clutch CL 4. The element coupling clutch CL4 is the same as the second modification of the first embodiment. However, the transmission 8e does not include the second element fixed clutch CL1 and the first path cutoff clutch CL 2.

As shown in fig. 7B, the transmission 8e transmits the rotational force from the engine 7 in the second continuously variable transmission mode with the element coupling clutch CL4 disengaged. In the engaged state of the element coupling clutch CL4, the transmission 8e transmits the rotational force from the engine 7 in the direct mode. The other configurations and mode switching control are the same as those of the transmissions 8a to 8 d.

Next, a transmission 8f according to a first modification of the second embodiment will be described. Fig. 8A is a schematic diagram showing the structure of the transmission 8 f. Fig. 8B is a table showing the relationship between the mode of the transmission 8f and the state of the clutch.

As shown in fig. 8A, the transmission 8f further includes a first path cutoff clutch CL2 in comparison with the transmission 8e of the second embodiment. The first path cutoff clutch CL2 is the same as the first modification of the first embodiment.

As shown in fig. 8B, the transmission 8f transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the engaged state of the element coupling clutch CL4 and the disengaged state of the first path cutoff clutch CL 2. The transmission 8f transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the element coupling clutch CL4 is disengaged and the first path cutoff clutch CL2 is engaged. In the engaged state of both the first path cutoff clutch CL2 and the element coupling clutch CL4, the transmission 8f transmits the rotational force from the engine 7 in the direct mode. The other configurations and mode switching control are the same as those of the transmissions 8a to e.

Next, a transmission 8g according to a second modification of the second embodiment will be described. Fig. 9A is a schematic diagram showing the structure of the transmission 8 g. Fig. 9B is a table showing the relationship between the mode of the transmission 8g and the state of the clutch.

As shown in fig. 9A, the transmission 8g further includes a first element fixed clutch CL3 in comparison with the transmission 8f according to the first modification of the second embodiment. The first element fixed clutch CL3 is the same as the first modification of the first embodiment.

As shown in fig. 9B, the transmission 8g transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where both the element coupling clutch CL4 and the first path cutoff clutch CL2 are disengaged and the first element stationary clutch CL3 is engaged. Further, even when the first element fixed clutch CL3 and the first path cutoff clutch CL2 are both in the disengaged state and the element connecting clutch CL4 is in the engaged state, the transmission 8g transmits the rotational force from the engine 7 in the first continuously variable mode.

The transmission 8g transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the first element fixed clutch CL3 and the element coupling clutch CL4 are both in the disengaged state and the first path cutoff clutch CL2 is in the engaged state. The transmission 8g transmits the rotational force from the engine 7 in the direct mode in a state where the first path cutoff clutch CL2 and the element coupling clutch CL4 are both engaged and the first element stationary clutch CL3 is disengaged. The other configurations and mode switching control are the same as those of the transmissions 8a to 8 f.

Next, a transmission 8h according to a third modification of the second embodiment will be described. Fig. 10A is a schematic diagram showing the structure of the transmission 8 h. Fig. 10B is a table showing the relationship between the mode of the transmission 8h and the state of the clutch.

As shown in fig. 10A, the transmission 8h further includes a bypass path 48 and a bypass clutch CL5, in comparison with the transmission 8f according to the first modification of the second embodiment. The bypass path 48 and the bypass clutch CL5 are the same as those in the third modification of the first embodiment.

As shown in fig. 10B, the transmission 8h transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the case where both the element coupling clutch CL4 and the first path cutoff clutch CL2 are in the disengaged state and the bypass clutch CL5 is in the engaged state. Further, even when the bypass clutch CL5 and the first path cutoff clutch CL2 are both in the disengaged state and the element connection clutch CL4 is in the engaged state, the transmission 8h transmits the rotational force from the engine 7 in the first continuously variable mode.

The transmission 8h transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the case where both the element coupling clutch CL4 and the bypass clutch CL5 are in the disengaged state and the first path cutoff clutch CL2 is in the engaged state. The transmission 8h transmits the rotational force from the engine 7 in the direct mode in a state where both the element connecting clutch CL4 and the first path cutoff clutch CL2 are engaged and the bypass clutch CL5 is disengaged. The other configurations and mode switching control are the same as those of the transmissions 8a to 8 g.

Next, a transmission 8i according to a third embodiment will be described. Fig. 11A is a schematic diagram showing the structure of the transmission 8 i. Fig. 11B is a table showing the relationship between the mode of the transmission 8i and the state of the clutch.

As shown in fig. 11A, the transmission 8i includes a first path cutoff clutch CL2 and a first element fixed clutch CL 3. The first path cutoff clutch CL2 and the first element fixed clutch CL3 are the same as those of the first modification of the first embodiment. However, the transmission 8i does not include the second element fixed clutch CL 1.

As shown in fig. 11B, the transmission 8i transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where the first path cutoff clutch CL2 is disengaged and the first element fixed clutch CL3 is engaged. The transmission 8i transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the first path cutoff clutch CL2 is in the engaged state and the first element fixed clutch CL3 is in the disengaged state. The other configurations and mode switching control are the same as those of the transmissions 8a to 8 h.

Next, a transmission 8j according to a first modification of the third embodiment will be described. Fig. 12A is a schematic diagram showing the structure of the transmission 8 j. Fig. 12B is a table showing the relationship between the mode of the transmission 8j and the state of the clutch.

As shown in fig. 12A, the transmission 8j includes an element connecting clutch CL4 instead of the first element fixed clutch CL3, in comparison with the transmission 8i of the third embodiment. The transmission 8j has the same configuration as the transmission 8f of the first modification of the second embodiment. However, as shown in fig. 12B, the controller 20 may switch the transmission 8j into the first continuously variable shift mode and the second continuously variable shift mode. The other configurations and mode switching control are the same as those of the transmissions 8a to 8 i.

Next, a transmission 8k according to a second modification of the third embodiment will be described. Fig. 13A is a schematic diagram showing the structure of the transmission 8 k. Fig. 13B is a table showing the relationship between the mode of the transmission 8k and the state of the clutch.

As shown in fig. 13A, the transmission 8k further includes a bypass path 48 and a bypass clutch CL5 instead of the first element fixed clutch CL3, in comparison with the transmission 8i of the third embodiment. The bypass path 48 and the bypass clutch CL5 are the same as those in the third modification of the first embodiment.

As shown in fig. 13B, the transmission 8k transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where the first path cutoff clutch CL2 is disengaged and the bypass clutch CL5 is engaged. The transmission 8k transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the first path cutoff clutch CL2 is in the engaged state and the bypass clutch CL5 is in the disengaged state. The other structures and the mode switching control are the same as those of the transmissions 8a to 8 j.

Next, a transmission 8l according to a third modification of the third embodiment will be described. Fig. 14A is a schematic diagram showing the structure of the transmission 8 l. Fig. 14B is a table showing the relationship between the mode of the transmission 8l and the state of the clutch.

As shown in fig. 14A, the transmission 8l further includes a direct path 49 and a direct clutch CL6, in comparison with the transmission 8i of the third embodiment. The direct path 49 connects the first rotation shaft 32 to the second rotation shaft 33 without passing through the first path 34, the second path 35, and the planetary gear mechanism 36. The direct path 49 is provided in parallel with the first path 34, and is connected to the first rotation shaft 32 via a gear. The direct path 49 is connected to the second rotary shaft 33 via a gear and a direct clutch CL 6.

The direct clutch CL6 can switch the connection and disconnection of the second rotation shaft 33 and the direct path 49. The direct clutch CL6 connects the second rotation shaft 33 and the direct path 49 in the engaged state. The direct clutch CL6 disconnects the second rotating shaft 33 from the direct path 49 in the disengaged state. The controller 20 controls the direct clutch CL6 in the same manner as the first path cutoff clutch CL2 and the first element fixed clutch CL 3.

As shown in fig. 14B, the transmission 8l transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where both the first path cutoff clutch CL2 and the direct clutch CL6 are disengaged and the first element fixed clutch CL3 is engaged. The transmission 8l transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the first path cutoff clutch CL2 is in the engaged state and both the direct clutch CL6 and the first element fixed clutch CL3 are in the disengaged state.

In fig. 14B, "-" indicates that any one of the disengaged state and the engaged state is possible. Therefore, the transmission 8l transmits the rotational force from the engine 7 in the direct mode in the state where the first path cutoff clutch CL2 is in the disengaged state or the engaged state, the first element fixed clutch CL3 is in the disengaged state, and the direct clutch CL6 is in the engaged state. Further, even when the first path cutoff clutch CL2 is in the disengaged state, the first element fixed clutch CL3 is in the disengaged state or the engaged state, and the direct clutch CL6 is in the engaged state, the transmission 8l transmits the rotational force from the engine 7 in the direct mode.

The other structures and the mode switching control are the same as those of the transmissions 8a to 8 k.

Next, a transmission 8m according to a fourth modification of the third embodiment will be described. Fig. 15A is a schematic diagram showing the structure of the transmission 8 m. Fig. 15B is a table showing the relationship between the mode of the transmission 8m and the state of the clutch.

As shown in fig. 15A, the transmission 8m includes an element coupling clutch CL4 instead of the first element fixed clutch CL3, in comparison with the transmission 8l according to the third modification of the third embodiment. The element coupling clutch CL4 is the same as the second modification of the first embodiment.

As shown in fig. 15B, the transmission 8m transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where both the first path cutoff clutch CL2 and the direct clutch CL6 are disengaged and the element coupling clutch CL4 is engaged. The transmission 8m transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the first path cutoff clutch CL2 is in the engaged state and both the direct clutch CL6 and the element coupling clutch CL4 are in the disengaged state.

The transmission 8m transmits the rotational force from the engine 7 in the direct mode in a state where the first path cutoff clutch CL2 is in the disengaged state or the engaged state, the element connection clutch CL4 is in the disengaged state, and the direct clutch CL6 is in the engaged state. Further, even when the first path cutoff clutch CL2 is in the disengaged state, the element connection clutch CL4 is in the disengaged state or the engaged state, and the direct clutch CL6 is in the engaged state, the transmission 8m transmits the rotational force from the engine 7 in the direct mode.

The other structures and the mode switching control are the same as those of the transmissions 8a to 8 l.

Next, a transmission 8n according to a fifth modification of the third embodiment will be described. Fig. 16A is a schematic diagram showing the structure of the transmission 8 n. Fig. 16B is a table showing the relationship between the mode of the transmission 8n and the state of the clutch.

As shown in fig. 16A, the transmission 8n further includes a direct path 49 and a direct clutch CL6, in comparison with the transmission 8k according to the second modification of the third embodiment. The direct path 49 and the direct clutch CL6 are the same as the transmission 8l of the third modification of the third embodiment.

As shown in fig. 16B, the transmission 8n transmits the rotational force from the engine 7 in the first continuously variable transmission mode in the state where both the first path cutoff clutch CL2 and the direct clutch CL6 are in the disengaged state and the bypass clutch CL5 is in the engaged state. The transmission 8n transmits the rotational force from the engine 7 in the second continuously variable transmission mode in the state where the first path cutoff clutch CL2 is in the engaged state and both the direct clutch CL6 and the bypass clutch CL5 are in the disengaged state.

The transmission 8n transmits the rotational force from the engine 7 in the direct mode in a state where the first path cutoff clutch CL2 is in the disengaged state or the engaged state, the bypass clutch CL5 is in the disengaged state, and the direct clutch CL6 is in the engaged state. Further, even when the first path cutoff clutch CL2 is in the disengaged state, the bypass clutch CL5 is in the disengaged state or the engaged state, and the direct clutch CL6 is in the engaged state, the transmission 8n transmits the rotational force from the engine 7 in the direct mode.

The other configurations and the mode switching control are the same as those of the transmissions 8a to 8 m.

While one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention.

The work vehicle 1 is not limited to a wheel loader, and may be another type of work vehicle such as a motor grader, a hydraulic excavator, or a bulldozer.

The work vehicle 1 is not limited to having an HMT, and may have another type of continuously variable transmission such as an EMT. That is, the motor 41 of the continuously variable transmission 38 may be an electric motor, and the power source 42 may be a generator. Alternatively, the electric power generated by the generator may be stored in a power storage device such as a battery, and the motor 41 may be driven by the electric power from the power storage device.

In the above embodiment, the transmissions 8a to 8n are so-called output-split type transmissions in which the output side of the continuously variable transmission 38 is connected to the input side of the planetary gear mechanism 36. However, the transmission may be a so-called input-split type transmission in which the input side of the continuously variable transmission 38 is connected to the output side of the planetary gear mechanism 36.

For example, fig. 17 is a modification in which the configuration of the transmission 8a of the first embodiment is applied to an input-split type transmission. Fig. 18 is a modification of the configuration of the transmission 8e of the second embodiment applied to an input-split transmission. Fig. 19 is a modification of the configuration of the transmission 8i of the third embodiment applied to an input-split transmission. As shown in fig. 17 to 19, the third element 45 of the planetary gear mechanism 36 may be connected to the first rotating shaft 32, as in the input-split transmissions 8a ', 8e ', and 8i '. The second element 44 of the planetary gear mechanism 36 may also be connected to the power source 42. The motor 41 may be connected to the second rotating shaft 33 via a gear.

Fig. 20 is a modification in which the configuration of a transmission 8d according to a third modification of the first embodiment is applied to an input-split transmission. As shown in fig. 20, in the input-split transmission 8 d', the bypass passage 48 may be connected to the first rotating shaft 32. The bypass clutch CL5 can also switch the connection and disconnection between the first rotating shaft 32 and the bypass path 48.

Fig. 21 is a modification in which the configuration of a transmission 8l of a third modification of the third embodiment is applied to an input-split type transmission. As shown in fig. 21, in the input-split transmission 8 l', the direct clutch CL6 can also switch between connection and disconnection between the first rotating shaft 32 and the direct path 49.

The same applies to other modifications as well, and can be applied to the input-split type transmission 8.

Industrial applicability

In the present invention, the transmission can be switched between a plurality of modes easily and smoothly.

Description of the reference numerals

7, an engine; 8a-8n, 8a ', 8d ', 8e ', 8i ', 8l ' transmissions; 17 a rotational speed sensor; 20 a controller; 32 a first rotation axis; 33 a second rotation axis; 34a first path; 34a first shaft portion; 34b a second shaft portion; 35 a second path; 36 a planetary gear mechanism; 38 a continuously variable transmission; 41 a motor; a 42 power source; 43 a first element; 44 a second element; 45 a third element; 48 bypass path; 49 direct path; the CL1 second element fixed clutch; CL2 first path cutoff clutch; the CL3 first element fixed clutch; a CL4 element connection clutch; CL5 bypass clutch; CL6 direct clutch.