阅读说明：本技术 液压能量处理系统、液压并联混合动力传动系和作业机 (Hydraulic energy processing system, hydraulic parallel hybrid powertrain and work machine ) 是由 卡尔·于贝尔 罗伯特·莫雷柳斯 埃里克·诺林 于 2018-10-18 设计创作，主要内容包括：本发明涉及一种用于作业机(10)的液压能量处理系统(16)。液压能量处理系统(16)包括高压侧(54)；低压侧(56)；液压机(58),该液压机用于机械驱动作业机(10)的机械传动系(14)并且由该机械传动系机械驱动；至少一个高压液压能量存储器(64),所述至少一个高压液压能量存储器被连接到高压侧(54)；液压马达(76),该液压马达具有入口侧(80)和出口侧(82)；液压泵(74),该液压泵被布置成向液压马达(76)的入口侧(80)供应液压流体；和返回管线(70),该返回管线用于将液压流体传导至液压箱(68)。液压能量处理系统(16)进一步包括卸压阀(72),该卸压阀被连接在高压侧(54)与返回管线(70)之间,该卸压阀(72)被布置成将多余的液压能量从高压侧(54)排放到返回管线(70),以便在机械传动系(14)上提供制动力；和优先阀装置(86),该优先阀装置(86)被连接到液压马达(76)的出口侧(82),该优先阀装置(86)被构造成将液压流体的优先流导向至低压侧(56)。(The present invention relates to a hydraulic energy handling system (16) for a work machine (10). The hydraulic energy processing system (16) includes a high pressure side (54); a low pressure side (56); a hydraulic machine (58) for mechanically driving a mechanical drive train (14) of a work machine (10) and being mechanically driven by the mechanical drive train; at least one high-pressure hydraulic energy store (64) connected to the high-pressure side (54); a hydraulic motor (76) having an inlet side (80) and an outlet side (82); a hydraulic pump (74) arranged to supply hydraulic fluid to an inlet side (80) of a hydraulic motor (76); and a return line (70) for conducting hydraulic fluid to the hydraulic tank (68). The hydraulic energy handling system (16) further comprises a pressure relief valve (72) connected between the high pressure side (54) and the return line (70), the pressure relief valve (72) being arranged to discharge excess hydraulic energy from the high pressure side (54) to the return line (70) in order to provide a braking force on the mechanical drive train (14); and a priority valve arrangement (86), the priority valve arrangement (86) being connected to the outlet side (82) of the hydraulic motor (76), the priority valve arrangement (86) being configured to direct a priority flow of hydraulic fluid to the low pressure side (56).)

1. A hydraulic energy processing system (16) for a work machine (10), the hydraulic energy processing system (16) comprising:

a high pressure side (54);

a low pressure side (56);

a hydraulic machine (58), the hydraulic machine (58) being for mechanically driving a mechanical drive train (14) of the work machine (10) and being mechanically driven by the mechanical drive train (14);

at least one high-pressure hydraulic energy storage (64), the at least one high-pressure hydraulic energy storage (64) being connected to the high-pressure side (54);

a hydraulic motor (76), the hydraulic motor (76) having an inlet side (80) and an outlet side (82);

a hydraulic pump (74), the hydraulic pump (74) being arranged to supply hydraulic fluid to the inlet side (80) of the hydraulic motor (76); and

a return line (70), the return line (70) for conducting hydraulic fluid to a hydraulic tank (68);

characterized in that the hydraulic energy processing system (16) further comprises:

a pressure relief valve (72), the pressure relief valve (72) being connected between the high pressure side (54) and the return line (70), the pressure relief valve (72) being arranged to discharge excess hydraulic energy from the high pressure side (54) to the return line (70) in order to provide a braking force on the mechanical drive train (14); and

a priority valve arrangement (86), the priority valve arrangement (86) being connected to the outlet side (82) of the hydraulic motor (76), the priority valve arrangement (86) being configured to direct a priority flow of hydraulic fluid to the low pressure side (56).

2. The hydraulic energy processing system (16) of claim 1, wherein the pressure relief valve (72) is hydro-mechanical.

3. The hydraulic energy processing system (16) of claim 1 or 2, further comprising a fan (78), and wherein the hydraulic motor (76) is arranged to drive the fan (78).

4. The hydraulic energy treatment system (16) of any one of the preceding claims, wherein the priority valve arrangement (86) is configured to direct a surplus flow of hydraulic fluid from the outlet side (82) of the hydraulic motor (76) to the return line (70).

5. The hydraulic energy processing system (16) of any one of the preceding claims, wherein the priority valve arrangement (86) includes a hydro-mechanical priority valve.

6. The hydraulic energy processing system (16) of any one of the preceding claims, further comprising an anti-cavitation valve (100), the anti-cavitation valve (100) being configured to allow hydraulic fluid to flow from the high pressure side (54) to the low pressure side (56) when hydraulic pressure on the low pressure side (56) falls below a cavitation threshold.

7. The hydraulic energy processing system (16) of any one of the preceding claims, wherein each of the at least one high pressure hydraulic energy storage (64) is a hydraulic accumulator.

8. The hydraulic energy processing system (16) of any one of the preceding claims, further comprising at least one low pressure hydraulic energy storage (66), the at least one low pressure hydraulic energy storage (66) being connected to the low pressure side (56).

9. The hydraulic energy processing system (16) of claim 8, wherein each of the at least one low pressure hydraulic energy storage (66) is a hydraulic accumulator.

10. The hydraulic energy processing system (16) of any one of the preceding claims, further comprising a control valve arrangement (84), the control valve arrangement (84) being configured to selectively connect the hydraulic machine (58) to the high pressure side (54).

11. The hydraulic energy processing system (16) of claim 10, wherein said control valve arrangement (84) is further configured to selectively connect said high pressure side (54) to said low pressure side (56).

12. The hydraulic energy processing system (16) according to any one of the preceding claims, wherein the hydraulic energy processing system (16) is for a hydraulic parallel hybrid powertrain (12).

13. A hydraulic parallel hybrid powertrain (12) for a work machine (10), the hydraulic parallel hybrid powertrain (12) comprising a mechanical driveline (14) and a hydraulic energy processing system (16) according to any one of the preceding claims.

14. The hydraulic parallel hybrid powertrain (12) of claim 13, wherein the mechanical drive train (14) includes a gearbox (44), the gearbox (44) having a gearbox output shaft (52), and wherein the hydraulic machine (58) is arranged to mechanically drive the gearbox output shaft (52) and is mechanically driven by the gearbox output shaft (52).

15. The hydraulic parallel hybrid powertrain (12) of claim 13 or 14, further comprising an internal combustion engine (42), and wherein the hydraulic pump (74) is driven by the internal combustion engine (42).

16. A work machine (10) comprising a hydraulic energy processing system (16) according to any one of claims 1 to 12 or a hydraulic parallel hybrid powertrain (12) according to any one of claims 13 to 15.

Technical Field

The present disclosure relates to a hydraulic energy handling system for a work machine, a hydraulic parallel hybrid powertrain for a work machine, and a work machine.

The invention is suitable for working machines in the field of industrial construction machines, material handling machines or construction equipment, in particular wheel loaders. Although the invention will be described in relation to a wheel loader, the invention is not limited to this particular machine, but may be used in any work machine where regenerative braking is possible, such as wheel excavators, articulated or rigid haulers and backhoe loaders.

Background

When transporting heavy loads, for example in construction work, work machines are often used. The working machine may be operated with large and heavy loads in areas without roads, for example for transport in connection with road or tunnel construction, sand pits, mines and similar environments.

To improve the fuel efficiency of the work machine, a hydraulic energy handling system may be used. Such a hydraulic energy handling system may include a hydraulic machine (operable both as a hydraulic pump and as a hydraulic motor) attached to a mechanical drive train of the work machine, and a hydraulic energy store, such as one or more hydraulic accumulators. When excess energy is available, the hydraulic energy handling system may be charged, for example, by driving a hydraulic machine that acts as a pump and charging a hydraulic accumulator with hydraulic fluid during braking of the work machine. The stored energy may then be returned to the mechanical drive train by driving the hydraulic machine as a motor with hydraulic fluid from the hydraulic accumulator in order to add drive torque to the mechanical drive train. In this way, kinetic energy from the work machine may be recovered and used later to add power to the mechanical drive train. Thus, it can be said that the hydraulic energy handling system constitutes a hydraulic flywheel.

US 2014087916 a1 discloses a hydraulic regeneration device for a motor vehicle having an engine, a transmission and a drive shaft. The regeneration device includes two fixed displacement hydraulic pump/motors, a low pressure hydraulic accumulator, a high pressure hydraulic accumulator, a multi-functional hydraulic manifold, and an electronic control system for receiving pressure information from the accumulators.

Since the capacity of the hydraulic energy store is usually relatively low, the hydraulic energy store will quickly fill up to a maximum when braking the work machine from high speed or during a long downhill slope. When the hydraulic energy store is full, braking with the hydraulic energy processing system must be discontinued to avoid over-pressurization. This no longer enables the work machine to be braked by charging the hydraulic energy store. Therefore, it is necessary to start using alternative braking systems, for example to avoid dangerous situations. One solution is to control the service brakes by means of an electronic valve arrangement, so that the service brakes are faded in at the same time as the hydraulic energy management system is faded out. However, this solution requires continuous monitoring of the hydraulic energy store and an electronically controlled valve system for the service brakes, which is complex and expensive. Furthermore, the brake blending control algorithm is difficult to adjust, since the service brakes typically have a rather stiff behavior, i.e. it is difficult to provide a smooth transition from braking with the hydraulic energy handling system to braking with the service brakes.

Disclosure of Invention

It is an object of the present invention to provide a hydraulic energy management system for a work machine which has a simple, inexpensive, efficient and/or reliable design and/or operation.

This object is achieved by a hydraulic energy handling system for a work machine according to claim 1. The hydraulic energy processing system includes: a high pressure side; a low pressure side; a hydraulic machine for mechanically driving a mechanical drive train of a work machine and mechanically driven by the mechanical drive train; at least one high pressure hydraulic energy store connected to the high pressure side; a hydraulic motor having an inlet side and an outlet side; a hydraulic pump arranged to supply hydraulic fluid to an inlet side of the hydraulic motor; and a return line for directing hydraulic fluid to the hydraulic tank. The hydraulic energy processing system further comprises a pressure relief valve connected between the high pressure side and the return line, the pressure relief valve being arranged to discharge excess hydraulic energy from the high pressure side to the return line for providing a braking force on the mechanical drive train; and a priority valve device connected to an outlet side of the hydraulic motor, the priority valve device being configured to direct a priority flow of the hydraulic fluid to a low pressure side.

During braking of the work machine, braking energy may be stored by pumping hydraulic fluid from a low pressure side to a high pressure side by the hydraulic machine, wherein the hydraulic fluid is initially stored in the high pressure hydraulic energy storage. When the high-pressure hydraulic energy store is full and the braking of the work machine continues, the hydraulic pressure in the high-pressure side rises until the pressure relief valve automatically opens and hydraulic fluid flows from the high-pressure side to the return line. The flow of hydraulic fluid through the pressure relief valve allows the work machine to maintain braking torque even when the high pressure hydraulic energy storage is fully charged, and no electronically controlled valve is required to activate the service brakes of the work machine.

Due to the braking force provided by the pressure relief valve when the high-pressure hydraulic energy store is full, the pressure relief valve constitutes, so to speak, a retarder valve. The invention allows a simple and seamless transition from regenerative braking by charging the high pressure hydraulic energy store to non-regenerative braking by throttling the hydraulic fluid through the pressure relief valve without the need for additional software control and monitoring.

During a longer retarder braking sequence, in which the hydraulic fluid is throttled by the pressure relief valve, the supply to the suction side of the hydraulic machine may be reduced, for example, as the low pressure hydraulic energy store is consumed. The priority valve arrangement handles the distribution of hydraulic fluid flow from the hydraulic motor to the low pressure side or return line, where flow to the low pressure side is prioritized. If the hydraulic pressure in the low pressure side is below a threshold value, the priority valve arrangement directs a priority flow of hydraulic fluid to the low pressure side, rather than unconditionally directing an outlet flow of hydraulic fluid from the hydraulic motor to the return line. Thereby, the supply of pressurized hydraulic fluid to the suction side of the hydraulic machine is ensured.

Since the priority valve arrangement is positioned in series with the hydraulic motor, i.e. downstream of the hydraulic motor, it is possible to use the already existing hydraulic pump for supplying hydraulic fluid to the low pressure side. Thus, the costs associated with dedicated hydraulic pumps may be avoided. Since the priority valve device is arranged downstream of the hydraulic motor, the supply of pressurized hydraulic fluid to the suction side of the hydraulic machine can be achieved without impairing the function of the hydraulic motor.

Furthermore, the hydraulic motor can be operated at full speed even when the hydraulic machine requires a large hydraulic fluid supply flow. The present invention thus effectively addresses the challenge of supplying pressurized hydraulic fluid to a hydraulic machine while fulfilling the full functionality of the hydraulic motor and hydraulic energy management system. It can be said that the hydraulic pump, the hydraulic motor and the priority valve means constitute the supply system of the hydraulic energy processing system.

When accelerating the vehicle, hydraulic fluid is released from the high pressure hydraulic energy storage to drive the hydraulic machine, which then acts as a motor. In this state, the hydraulic machine adds drive torque to the mechanical drive train so that drive torque from the internal combustion engine of the work machine can be supplemented or replaced.

The hydraulic machine may be coupled to the mechanical drive train via a clutch. By disengaging the clutch, the hydraulic energy handling system may be isolated from the mechanical drive train. Alternatively, the hydraulic machine may be permanently coupled to the mechanical drive train such that the hydraulic machine is always driven by (and always drives) the mechanical drive train.

The hydraulic energy processing system according to the present disclosure may be configured for use with a hydraulic parallel hybrid powertrain of a work machine, wherein the hydraulic parallel hybrid powertrain includes a mechanical driveline. In this case, the hydraulic machine may be configured to mechanically drive and be mechanically driven by a mechanical drive train of the hydraulic parallel hybrid powertrain. Parallel means that the hydraulic energy handling system is complementary to the mechanical drive train and does not interfere with the normal operation of the mechanical drive train. Throughout this disclosure, the terms high pressure side and low pressure side mean that the pressure in the high pressure side is higher than the pressure in the low pressure side during operation of the hydraulic energy processing system.

The pressure relief valve may be configured to open automatically when a certain set pressure is reached on the high pressure side, e.g. to operate based on the set pressure on the high pressure side only. According to one embodiment, the pressure relief valve is hydro-mechanical. Since the pressure relief valve is not actively controlled, no additional software control is required. Switching to retarder braking via the pressure relief valve is seamless to the driver, since there is no complex control.

According to an embodiment, the hydraulic energy handling system further comprises a fan, and the hydraulic motor is arranged to drive the fan. The preferential flow of hydraulic fluid to the low pressure side according to the invention is particularly advantageous during high power operation, in which a large supply flow of hydraulic fluid needs to be provided to the hydraulic machine at the same time as high fan power is required.

The hydraulic pump for the fan constitutes one of several suitable existing pumps which can be used for supplying hydraulic fluid to the hydraulic energy treatment system according to the invention. By using an already existing hydraulic pump in the working machine, a dedicated fluid supply pump can be avoided.

According to one embodiment, the priority valve arrangement is configured to direct a surplus flow of hydraulic fluid from the outlet side of the hydraulic motor to the return line. The priority valve means may comprise a hydro-mechanical priority valve. Thus, the priority valve arrangement may operate independently and may not require control from, for example, a central control unit of the work machine. Alternatively, however, the priority valve arrangement may be electrically controlled, for example based on signals from an electronic sensor for sensing the set pressure on the low pressure side. As another alternative, the priority valve arrangement may comprise two on/off valves connected to the outlet side of the hydraulic motor, one on/off valve being connected to the low pressure side and one on/off valve being connected to the return line.

According to one embodiment, the hydraulic energy processing system further comprises an anti-cavitation valve configured to allow hydraulic fluid to flow from the high pressure side to the low pressure side when the hydraulic pressure on the low pressure side is below a cavitation threshold. Thus, if the hydraulic pressure on the low pressure side becomes very low despite the supply from the priority valve device (e.g., during a long downhill slope), the anti-cavitation valve ensures the recirculation of hydraulic fluid from the high pressure side to the low pressure side. Each of the at least one high pressure hydraulic energy store may be a hydraulic accumulator, such as a hydropneumatic accumulator.

According to an embodiment, the hydraulic energy handling system further comprises at least one low pressure hydraulic energy storage connected to the low pressure side. The low pressure hydraulic energy store may ensure sufficient pressure on the low pressure side to avoid cavitation before the priority valve arrangement directs the priority flow of hydraulic fluid to the low pressure side.

The low pressure hydraulic energy store on the low pressure side also enables the high pressure side and the low pressure side to be reversed. Each of the at least one low-pressure hydraulic accumulator may also be a hydraulic accumulator, such as a hydropneumatic accumulator.

According to one embodiment, the hydraulic energy processing system further comprises a control valve arrangement configured to selectively connect the hydraulic machine to the high pressure side. According to one embodiment, the control valve arrangement may further be configured to selectively connect the high pressure side to the low pressure side. However, the control valve arrangement may be omitted, for example where the hydraulic machine is a four quadrant hydraulic machine.

According to one embodiment, the hydraulic energy processing system is for a hydraulic parallel hybrid powertrain, and thus, the hydraulic energy processing system may be configured for use in a hydraulic parallel hybrid powertrain.

The invention also relates to a hydraulic parallel hybrid powertrain for a work machine, wherein the hydraulic parallel hybrid powertrain comprises a mechanical drive train and a hydraulic energy processing system according to the invention. In this case, the hydraulic machine may be arranged to mechanically drive and be mechanically driven by a mechanical drive train of the hydraulic parallel hybrid powertrain. Although not described in detail herein, the hydraulic energy processing system of the hydraulically parallel hybrid powertrain may alternatively form a portion of the hydrostatic transmission.

According to one embodiment, the mechanical drive train comprises a gearbox having a gearbox output shaft, and the hydraulic machine is arranged to mechanically drive and be mechanically driven by the gearbox output shaft. However, the hydraulic machine may be driven by and drive an alternative component of the mechanical drive train. The hydraulic parallel hybrid powertrain may further include an internal combustion engine. In this case, the hydraulic pump may be driven by the internal combustion engine.

The invention also relates to a working machine comprising a hydraulic energy handling system according to the invention or a hydraulic parallel hybrid powertrain according to the invention. The work machine may be a wheel loader. Alternatively, the work machine may be a wheeled excavator, an articulated or rigid transporter, or a backhoe loader.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.

Drawings

The following is a more detailed description of embodiments of the invention, reference being made to the accompanying drawings by way of example.

In the drawings:

fig. 1 is a schematic illustration of a work machine according to the present disclosure, including a hydraulic parallel hybrid powertrain,

fig. 2 is a block diagram of a hydraulic parallel hybrid powertrain according to an embodiment of the present invention, including a mechanical driveline and a hydraulic energy processing system,

FIG. 3 is a block diagram of a priority valve apparatus according to an embodiment of the invention, an

FIG. 4 is a block diagram of a hydraulic parallel hybrid powertrain including a mechanical driveline and an additional hydraulic energy processing system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Hereinafter, a hydraulic energy processing system for a working machine, a hydraulic parallel hybrid powertrain for a working machine, and a working machine will be described. The same reference numerals will be used to refer to the same or similar structural features.

Fig. 1 is a schematic illustration of a work machine 10 according to the present disclosure. The work machine 10 includes a hydraulic parallel hybrid powertrain 12, which hydraulic parallel hybrid powertrain 12 in turn includes a mechanical driveline 14 and a hydraulic energy processing system 16. The hydraulically parallel hybrid powertrain 12 constitutes a propulsion system for the work machine 10.

The work machine 10 is here illustrated as a wheel loader, comprising a front body section 18 and a rear body section 20, both having an axle for driving a pair of wheels 22. The rear body section 20 includes a cab 24. The body sections 18, 20 are connected to one another in such a way that they can be pivoted relative to one another about a vertical axis by means of two first actuators in the form of hydraulic cylinders 26, 28 arranged between the two body sections 18, 20. Hydraulic cylinders 26, 28 are thus arranged one on each side of a horizontal center line in the direction of travel of work machine 10 in order to turn work machine 10.

Work machine 10 further includes an apparatus 30 for handling objects or materials 32. The apparatus 30 includes a load-arm unit 34 (also referred to as a linkage) and a tool in the form of a bucket 36 mounted on the load-arm unit 34. A first end of the load-arm unit 34 is pivotally connected to the front body section 18. The bucket 36 is pivotally connected to a second end of the load-arm unit 34. The load-arm unit 34 may be raised and lowered relative to the front body section 18 of the work machine 10 by means of two second actuators in the form of two hydraulic cylinders 38, 40, each of which cylinders 38, 40 is connected at one end to the front body section 18 and at the other end to the load-arm unit 34.

Fig. 2 is a block diagram of the hydraulic parallel hybrid powertrain 12 of fig. 1, including the mechanical driveline 14 and the hydraulic energy processing system 16. The mechanical drive train 14 includes an internal combustion engine 42 and a gearbox 44. In this example, the mechanical drive train 14 further includes a torque converter 46, the torque converter 46 being between the internal combustion engine 42 and the gearbox 44. A power take-off (PTO)48 is also provided between the internal combustion engine 42 and the torque converter 46 for driving a hydraulic work function 50, such as the hydraulic cylinders 26, 28, 38, 40 of the work machine 10. The wheels 22 of the work machine 10 are driven via a gearbox output shaft 52.

The hydraulic energy processing system 16 is connected to the mechanical drive train 14 for the purpose of storing and releasing energy to propel the mechanical drive train 14. The hydraulic energy processing system 16 includes a high pressure side 54, a low pressure side 56, and a hydraulic machine 58. In this example, the hydraulic machine 58 is a four quadrant hydraulic machine. Thus, the high pressure side 54 and the low pressure side 56 may be reversed.

The hydraulic machine 58 includes a first side 60 and a second side 62. Where the hydraulic machine 58 is operating as a pump (e.g., during braking of the work machine 10), the first side 60 is the suction side and the second side 62 is the discharge side. Throughout this disclosure, the high pressure side 54 and the low pressure side 56 may be comprised of high pressure lines and low pressure lines, respectively.

The hydraulic energy processing system 16 further comprises a high pressure hydraulic energy storage 64, which high pressure hydraulic energy storage 64 is connected to the high pressure side 54. In this example, the high pressure hydraulic energy store 64 is a hydraulic accumulator. The exemplary hydraulic energy processing system 16 further includes an optional low pressure hydraulic energy store 66, which low pressure hydraulic energy store 66 is also comprised of a hydraulic accumulator connected to the low pressure side 56.

The hydraulic energy processing system 16 further comprises a hydraulic tank 68 and a return line 70 for conducting hydraulic fluid to the hydraulic tank 68. Although two separate hydraulic tanks 68 are shown in fig. 2, the hydraulic tanks 68 may be a common tank.

The hydraulic energy treatment system 16 further includes a pressure relief valve 72. A pressure relief valve 72 is connected between the high pressure side 54 and the return line 70. The pressure relief valve 72 is normally closed and is configured to automatically open when a set pressure in the high pressure side 54 is reached. In this example, the pressure relief valve 72 is hydro-mechanical.

The hydraulic energy processing system 16 further includes a hydraulic pump 74 and a hydraulic motor 76. In this example, the hydraulic motor 76 is arranged to drive a fan 78 of the hydraulic energy processing system 16. The hydraulic motor 76 includes an inlet side 80 and an outlet side 82. The hydraulic pump 74 is arranged to supply hydraulic fluid to an inlet side 80 of the hydraulic motor 76. In the example of fig. 2, the hydraulic pump 74 is an auxiliary pump of the internal combustion engine 42, driven by an additional PTO of the internal combustion engine 42. However, the hydraulic pump 74 may be driven in an alternative manner.

The hydraulic energy treatment system 16 of this example further includes a control valve arrangement 84. The control valve arrangement 84 is configured to selectively connect the hydraulic machine 58 to the high pressure side 54. Control valve arrangement 84 is also configured to selectively connect high pressure side 54 to low pressure side 56. The control valve arrangement 84 may be implemented in various ways. The control valve device 84 may also be omitted. The hydraulic energy treatment system 16 may, for example, operate without the ability to connect the high pressure side 54 to the low pressure side 56.

The hydraulic energy processing system 16 further includes a priority valve arrangement 86. A priority valve arrangement 86 is connected to the outlet side 82 of the hydraulic motor 76. The hydraulic motor 76 and the priority valve arrangement 86 are thus arranged in series. In the example of fig. 2, the outlet side 82 of the hydraulic motor 76 is directly connected to an inlet 88 of a priority valve arrangement 86. However, one or more additional hydraulic consumers (not shown) may be provided between hydraulic motor 76 and priority valve arrangement 86.

The priority valve arrangement 86 is configured to direct a priority flow of hydraulic fluid to the low pressure side 56. The priority valve arrangement 86 is also configured to direct a surplus flow of hydraulic fluid from the outlet side 82 of the hydraulic motor 76 to the return line 70. To this end, the priority valve arrangement 86 includes a priority flow outlet 90 connected to the low pressure side 56 and a surplus flow outlet 92 connected to a bypass line 94. Downstream of the pressure relief valve 72, a bypass line 94 is connected to the return line 70. Thus, the priority valve arrangement 86 handles the distribution of the flow of hydraulic fluid from the hydraulic motor 76 to the low pressure side 56 or return line 70.

A check valve 96 is provided on the bypass line 94 that only allows hydraulic fluid to flow to the return line 70. Fig. 2 further shows an oil cooler 98 arranged on the return line 70. Throughout this disclosure, hydraulic pump 74, hydraulic motor 76, and priority valve arrangement 86 may be referred to as a supply system.

The hydraulic machine 58 is arranged to mechanically drive the mechanical drive train 14 and is mechanically driven by the mechanical drive train 14. The hydraulic machine 58 may, for example, always be driven by rotation of the gearbox output shaft 52. The discharge of hydraulic fluid from the hydraulic machine 58 may be varied by varying the displacement. Alternatively, the hydraulic machine 58 may be driven by (and drive) a shaft attached to the gearbox output shaft 52 via planetary gears (not shown) and a clutch (not shown).

When storing energy from the mechanical drive train 14, the hydraulic machine 58 operates as a pump and converts mechanical power from the mechanical drive train 14 into pressurized hydraulic fluid that is fed to the high pressure hydraulic energy storage 64 via the control valve arrangement 84. This is done, for example, when capturing braking energy from work machine 10.

When the hydraulic machine 58 is operating to pump hydraulic fluid to the high pressure side 54, a first side 60 (in this case the suction side) of the hydraulic machine 58 requires a supply of pressurized hydraulic fluid. Some supply of pressurized hydraulic fluid to the hydraulic machine 58 may be provided by an optional low pressure hydraulic energy store 66. Thus, when energy is stored in the high-pressure hydraulic energy store 64, the low-pressure hydraulic energy store 66 is drained. When the energy stored in the high-pressure hydraulic energy storage 64 is released, the high-pressure hydraulic energy storage 64 is drained and the hydraulic machine 58, now operating as a hydraulic motor, converts hydraulic power to mechanical power to propel the mechanical drive train 14. During this process, the low pressure hydraulic energy store 66 is refilled.

A pressure relief valve 72 is connected to the high pressure side 54 to act as a "retarder valve" to maintain braking torque on the mechanical drive train 14 when the high pressure hydraulic energy storage 64 is full. That is, the pressure relief valve 72 is arranged to vent excess hydraulic energy from the high pressure side 54 to the return line 70 in order to provide braking force on the mechanical drive train 14.

As shown in fig. 2, a pressure relief valve 72 is connected between the high pressure side 54 and the return line 70. When the set pressure on the high pressure side 54 is exceeded, the pressure relief valve 72 opens and vents pressurized hydraulic fluid from the high pressure side 54 to the return line 70. The hydraulic fluid is thereby throttled by the pressure relief valve 72. This throttling provides a braking force on the mechanical drive train 14. The hydraulic energy processing system 16 can thus maintain the braking torque by throttling of the hydraulic fluid flow via the pressure relief valve 72, even when the high pressure hydraulic energy storage 64 is full. This transition does not require additional software control because the pressure relief valve 72 opens automatically when a certain pressure is reached.

One challenge with this type of retarder braking with the pressure relief valve 72 is that hydraulic fluid leaves the hydraulic circuit comprising the high pressure side 54 and the low pressure side 56, as compared to circulating back and forth between the high pressure side 54 and the low pressure side 56. The hydraulic fluid is also heated as it passes through the pressure relief valve 72. Thus, during retarder braking, it is necessary to supply the first side 60 (in this case the suction side) of the hydraulic machine 58 with cold pressurized fluid, at least when the optional low pressure hydraulic energy storage 66 is emptied. During retarder braking by the pressure relief valve 72, the priority valve arrangement 86 connected in series with the hydraulic motor 76 feeds cold pressurized hydraulic fluid to the first side 60 of the hydraulic machine 58. When the pressure on the low pressure side 56 increases after the pressure relief valve 72 closes and the hydraulic machine 58 has stopped pumping, the priority valve arrangement 86 directs hydraulic fluid from the hydraulic motor 76 to the return line 70, in this example via the bypass line 94 to the return line 70.

Hydraulic pump 74 may function as a supply pump for hydraulic energy treatment system 16 and does not impair the function of fan 78. Since the hydraulic pump 74 already present is used not only to drive the hydraulic motor 76 for the fan 78, but also to supply pressurized hydraulic fluid to the low pressure side 56, costs associated with components that would otherwise be dedicated to this supply may be reduced or avoided. Furthermore, the series arrangement of hydraulic motor 76 and priority valve arrangement 86 allows fan 78 to operate at full speed, even when hydraulic machine 58 requires a maximum hydraulic fluid supply flow.

In fig. 2, a hydraulic motor 76 is arranged to drive a fan 78. However, the hydraulic motor according to the present disclosure (i.e., the hydraulic motor arranged in series with priority valve arrangement 86) may be comprised by an alternative hydraulic motor of work machine 10, such as a hydraulic motor used for axle oil cooling, differential lock actuation, lubrication, and the like.

Fig. 3 is a block diagram of a priority valve arrangement 86 according to an embodiment of the invention. In this embodiment, the priority valve arrangement 86 is a hydro-mechanical priority valve.

As long as the set pressure on the low pressure side 56 is below the threshold, the inlet 88 is in fluid communication with the priority flow outlet 90 and hydraulic fluid is directed from the outlet side 82 of the hydraulic motor 76 to the low pressure side 56. When the set pressure on the low pressure side 56 exceeds a threshold, the inlet 88 is in fluid communication with the surplus flow outlet 92, and hydraulic fluid is directed from the outlet side 82 of the hydraulic motor 76 to a bypass line 94. The priority valve arrangement 86 is thus configured to reduce the supply pressure of the hydraulic fluid on the low pressure side 56 to the appropriate level required by the hydraulic machine 58 and to direct the flow of hydraulic fluid to the bypass line 94 when that pressure level is reached. The priority valve arrangement 86 may be implemented without software control and is therefore simpler and less expensive.

The priority valve arrangement 86 of fig. 3 is only one of several possible embodiments of the priority valve arrangement 86 according to the present invention. Alternative types of priority valve arrangement 86 that also do not require software control are possible.

Fig. 4 is a block diagram of a hydraulic parallel hybrid powertrain 12 according to an embodiment of the present invention, the hydraulic parallel hybrid powertrain 12 including a mechanical driveline 14 and an additional hydraulic energy processing system 16. The main differences with respect to the embodiment in fig. 2 will be described.

The hydraulic energy treatment system 16 of this embodiment further includes an anti-cavitation valve 100. The anti-cavitation valve 100 is disposed on a line 102 between the high pressure side 54 and the low pressure side 56. The anti-cavitation valve 100 is configured to allow hydraulic fluid to flow from the high pressure side 54 to the low pressure side 56 when the hydraulic pressure on the low pressure side 56 drops below a cavitation threshold.

When the pressure relief valve 72 is used as a retarder valve (e.g., during braking of the work machine 10) and the pressure on the low pressure side 56 becomes very low, the anti-cavitation valve 100 opens such that hydraulic fluid is directed from the high pressure side 54 to the low pressure side 56. Despite the hydraulic motor 76 and the priority valve arrangement 86, the reason for such a pressure drop on the low pressure side 56 may be that the pressure relief valve 72 is used for retarder braking for a long time (e.g. during a long downhill slope) and/or that the flow from the hydraulic pump 74 is limited and cannot supply the same amount of hydraulic fluid as the amount of hydraulic fluid pumped by the hydraulic machine 58. If such a pressure drop on the low pressure side 56 occurs, the anti-cavitation valve 100 will open and a portion of the hydraulic fluid flow on the high pressure side 54 will be recycled directly to the low pressure side 56.

Fig. 4 further illustrates the positioning of two additional optional hydraulic consumers 104, 106 to which the hydraulic energy processing system 16 can feed hydraulic fluid. A hydraulic consumer 106 is located on the outlet side 82 of the hydraulic motor 76, i.e., between the hydraulic motor 76 and the priority valve arrangement 86. A hydraulic consumer 104 is located on the return line 70 upstream of the oil cooler 98.

It is to be understood that the invention is not limited to the embodiments described above and shown in the drawings; rather, one of ordinary skill in the art appreciates that various modifications and changes can be made within the scope of the claims set forth below.