阅读说明：本技术 发动机 (Engine ) 是由 坂口祐生 合田茂生 井谷昌裕 于 2020-03-05 设计创作，主要内容包括：发动机具备发动机主体和ECU。ECU构成为：在启动时满足了规定条件的情况下,能够执行高怠速限制。在执行高怠速限制时,ECU基于启动时的发动机温度,求取作为高怠速转速的上限值的第一上限转速和作为高怠速限制的持续时间的第一限制时间。ECU基于环境温度,求取作为高怠速转速的上限值的第二上限转速和作为高怠速限制的持续时间的第二限制时间。ECU基于所求取到的第一上限转速及第二上限转速中的任一者和第一限制时间及第二限制时间中的任一者,执行高怠速限制。(The engine includes an engine main body and an ECU. The ECU is configured to: when a predetermined condition is satisfied at the time of startup, the high idle speed limitation can be executed. When the high idle speed limitation is executed, the ECU obtains a first upper limit rotating speed as an upper limit value of the high idle speed and a first limiting time as a duration of the high idle speed limitation based on an engine temperature at the time of starting. The ECU obtains a second upper limit rotation speed as an upper limit value of the high idle rotation speed and a second limit time as a duration of the high idle rotation speed limit based on the ambient temperature. The ECU executes the high idle speed limitation based on any one of the first upper limit rotation speed and the second upper limit rotation speed and any one of the first limitation time and the second limitation time.)

1. An engine comprising an engine body and a control unit for controlling the engine body,

the engine is characterized in that it is provided with a motor,

the control unit is configured to: when a predetermined condition is satisfied at the time of start, high idle speed limitation can be performed,

when the high idle speed limitation is executed, the control unit obtains a first upper limit rotation speed as an upper limit value of the high idle speed and a first limit time as a duration of the high idle speed limitation based on an engine temperature at the time of startup, obtains a second upper limit rotation speed as an upper limit value of the high idle speed and a second limit time as a duration of the high idle speed limitation based on an ambient temperature, and executes the high idle speed limitation based on any one of the obtained first upper limit rotation speed and the second upper limit rotation speed and any one of the first limit time and the second limit time.

2. The engine of claim 1,

the control unit sets, as a rotation speed limit value in the high idle speed limit, the rotation speed of which is smaller than the first upper limit rotation speed and the second upper limit rotation speed.

3. The engine according to claim 1 or 2,

the control unit sets the longer of the first limit time and the second limit time as the duration of the high idle speed limit.

4. The engine according to any one of claims 1 to 3,

the control portion uses a lowest temperature of at least a cooling water temperature, a fuel temperature, an exhaust gas temperature as the engine temperature.

5. The engine according to any one of claims 1 to 4,

the engine includes an exhaust gas purification device configured to: the urea water supplied from the urea water tank can be mixed with the exhaust gas to remove nitrogen oxides contained in the exhaust gas,

the control portion uses a lowest temperature among a fresh air temperature, a fuel temperature, and a urea water temperature as the ambient temperature.

6. The engine according to any one of claims 1 to 5,

as the predetermined condition for executing the high idle speed limitation at the time of startup, at least all of the cooling water temperature, the fuel temperature, and the exhaust gas temperature are lower than respective threshold values.

Technical Field

The invention relates to high idle speed limiting during engine starting.

Background

Conventionally, in order to prevent seizure due to insufficient lubrication during high-speed rotation at the time of engine start, a method of limiting high-idle rotation is known. Patent document 1 discloses a method of controlling such an engine at the time of starting.

Patent document 1 discloses a problem that, at the time of engine start, since the temperature and viscosity of the lubricating oil are low and the lubricating oil does not completely enter the rotating portion, when the accelerator pedal is depressed to rapidly increase the engine rotation, the abrasion of the rotating portion of the engine becomes severe. In the method for controlling the engine at the time of starting proposed in patent document 1, when the temperature of the engine cooling water or the engine lubricating oil is lower than a predetermined temperature, the increase amount of the fuel injection amount from the fuel injection nozzle is limited even if the engine rotation-up operation is performed.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-57804

Disclosure of Invention

However, the configuration of patent document 1 requires a separate temperature sensor for detecting the temperature of the engine lubricating oil, which increases the cost. In the configuration of patent document 1, the execution time of the high idle speed limit is not set. Therefore, when the execution time is short, the engine lubricating oil may not be sufficiently heated. On the other hand, if the execution time is long, the startability of the engine is reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine capable of maintaining good startability and appropriately performing high idle speed limitation.

The problems to be solved by the present invention are as described above, and means for solving the problems and effects thereof will be described below.

According to an aspect of the present invention, an engine configured as follows is provided. That is, the engine includes an engine main body and a control unit that controls the engine main body. The control unit is configured to: when a predetermined condition is satisfied at the time of startup, the high idle speed limitation can be executed. When the high idle speed limitation is executed, the control unit obtains a first upper limit rotation speed as an upper limit value of the high idle speed and a first limitation time as a duration of the high idle speed limitation based on an engine temperature at the time of startup. The control unit obtains a second upper limit rotation speed as an upper limit value of the high idle rotation speed and a second limit time as a duration of the high idle rotation speed limit based on the ambient temperature. The control unit executes the high idle speed limitation based on any one of the first upper limit rotation speed and the second upper limit rotation speed and any one of the first limitation time and the second limitation time.

This can restrict high-speed rotation when the engine temperature is low. Therefore, the occurrence of seizure in the supercharger or the like due to insufficient lubrication can be prevented.

In the engine, it is preferable that the control unit sets, as the rotation speed limit value in the high idle speed limit, a rotation speed at which the number of rotations of the first upper limit rotation speed and the second upper limit rotation speed is smaller.

This enables the limited rotation speed during the high idle speed limitation to be set more appropriately.

In the engine, it is preferable that the control unit sets a longer one of the first limit time and the second limit time as the duration of the high idle speed limit.

This enables the duration of the high idle speed restriction to be set more appropriately.

In the engine, it is preferable that the control unit uses, as the engine temperature, a lowest temperature of at least a cooling water temperature, a fuel temperature, and an exhaust gas temperature.

As a result, the first upper limit rotation speed and the first limit time can be calculated using the strictest temperature condition among the temperatures of the respective portions related to the engine temperature. Therefore, the high idle speed restriction more suitable for the operating state of the engine can be executed.

In the engine, the following configuration is preferably adopted. That is, the engine is provided with an exhaust gas purification device. The exhaust gas purification device is configured to: the urea water supplied from the urea water tank can be mixed with the exhaust gas to remove nitrogen oxides contained in the exhaust gas. The control portion uses a lowest temperature among a fresh air temperature, a fuel temperature, and a urea water temperature as the ambient temperature.

Thus, by adopting the most severe conditions, the second upper limit rotation speed and the second limit time that appropriately reflect the operating environment of the engine can be obtained. Therefore, high-speed rotation at low temperatures can be avoided more reliably.

In the engine, the following configuration is preferably adopted. That is, as the predetermined condition for executing the high idle speed limitation at the time of startup, at least all of the cooling water temperature, the fuel temperature, and the exhaust gas temperature are lower than the respective threshold values.

Thereby, unnecessary execution of the high idle speed restriction can be avoided. Therefore, the startability of the engine can be improved.

Drawings

Fig. 1 is a perspective view showing a configuration of an engine according to an embodiment of the present invention.

Fig. 2 is a schematic diagram showing a schematic configuration of the engine.

Fig. 3 is a functional block diagram showing the configuration of the ECU.

Fig. 4 is a block diagram illustrating the high idle speed limitation at the time of startup.

Fig. 5 is a graph showing control relating to the high idle speed limit when the high idle speed limit is released.

Detailed Description

Next, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing a configuration of an engine 100 according to an embodiment of the present invention. Fig. 2 is a schematic diagram showing a schematic configuration of engine 100.

An engine 100 shown in fig. 1 is a diesel engine, and is mounted on, for example, an agricultural machine such as a tractor, a construction machine such as an excavator, or the like. The engine 100 is configured to: such as a series four cylinder engine having 4 cylinders. The number of cylinders is not limited to 4. The engine 100 of the present embodiment mainly includes: an engine body 1, an ATD (exhaust gas purification device) 43, and an ECU90 as a control unit. ATD is an abbreviation of post-processing Device (After Treatment Device). The ECU is an Engine Control Unit (Engine Control Unit) for short.

First, a basic structure of the engine body 1 provided in the engine 100 will be briefly described. As shown in fig. 1 and the like, the engine main body 1 mainly includes: an oil pan 11, a cylinder block 12, a cylinder head 13, and a head cover 14, which are arranged in this order from the lower side.

The oil pan 11 is provided at a lower portion (lower end portion) of the engine 100. The oil pan 11 is formed in a container shape with an open upper portion. Oil for lubricating engine 100 is stored in oil pan 11.

The oil stored in the oil pan 11 is sucked by an oil pump, not shown, provided in the engine main body 1, supplied to each part of the engine main body, lubricates the engine main body 1, and then returned to the oil pan 11 to be stored.

The cylinder block 12 is mounted on the upper side of the oil pan 11. A recess for accommodating a crankshaft, not shown, and the like, and a plurality of cylinders 30 are formed in the cylinder block 12.

The cylinder head 13 is mounted on the upper side of the cylinder block 12. A combustion chamber 31 shown in fig. 2 is formed through the cylinder head 13 and the cylinder block 12 so as to correspond to each cylinder 30.

Each cylinder 30 accommodates a piston. The piston is connected to the crankshaft via a connecting rod, not shown. The crankshaft is rotated by the reciprocating motion of the piston.

A water jacket, not shown, for cooling the engine body 1 is formed in the cylinder head 13. The engine 100 of the present embodiment is provided with a cooling water circulation system, not shown, so that the engine body 1 does not become overheated due to combustion of fuel. Note that, instead of being formed in the cylinder head 13, the water jacket may be formed in the cylinder block.

The cooling water circulation system is constituted by: the cooling water is returned to the water jacket formed in the cylinder head 13 of the engine body 1, and the heat exchange is performed between the engine body 1 and the water jacket. A cooling water temperature sensor 91 for detecting the temperature of the cooling water is provided at an appropriate position of the cooling water path in the cooling water circulation system. The cooling water temperature detected by the cooling water temperature sensor 91 is output to the ECU 90.

A head cover 14 is mounted on the upper side of the cylinder head 13. A valve mechanism including a not-shown pushrod and a rocker arm for operating an exhaust valve, not shown, and a throttle valve 22, described later, is housed in the head cover 14.

Next, focusing on intake air flow and exhaust gas flow, the configuration of engine 100 of the present embodiment will be briefly described with reference to fig. 2 and the like.

As shown in fig. 2, engine 100 includes an intake unit 2, a power generation unit 3, and an exhaust unit 4 as main components.

The intake portion 2 takes in air from the outside. The intake unit 2 includes: an intake pipe 21, a throttle valve 22, an intake manifold 23, and a supercharger 24.

The intake pipe 21 constitutes an intake passage and can flow air taken in from the outside. A fresh air temperature sensor 92 for detecting the temperature of air (fresh air) taken in from the outside is provided in the intake pipe 21 on the upstream side of an outlet of an EGR pipe 53 described later. The temperature of the fresh air detected by the fresh air temperature sensor 92 is output to the ECU 90.

The throttle valve 22 is disposed in the middle of the intake passage. The throttle valve 22 is constituted by: the cross-sectional area of the intake passage is changed by changing the opening degree in accordance with a control command from the ECU 90. This enables adjustment of the amount of air supplied to the intake manifold 23 (i.e., the intake air amount).

The intake manifold 23 is connected to a downstream-side end portion of the intake pipe 21 in the direction in which intake air flows. The intake manifold 23 distributes the air supplied through the intake pipe 21 according to the number of cylinders 30, and supplies the air to the combustion chambers 31 formed in the respective cylinders 30.

The power generation unit 3 is constituted by a plurality of (4 in the present embodiment) cylinders 30. The power generation unit 3 is configured to: the power for reciprocating the piston is generated by burning fuel in a combustion chamber 31 formed in each cylinder 30.

Specifically, in each combustion chamber 31, air supplied from the intake manifold 23 is compressed, and then fuel supplied from the fuel tank 71 is injected. This causes combustion in the combustion chamber 31, and the piston can be reciprocated up and down. The power thus obtained is transmitted to an appropriate device on the power downstream side via a crankshaft or the like.

As shown in fig. 2, the supercharger 24 includes: a turbine 25, a shaft 26, and a compressor 27. The compressor 27 is connected to the turbine 25 via a rotating shaft 26. As the turbine 25 rotated by the exhaust gas discharged from the combustion chamber 31 rotates, the compressor 27 rotates, and the air purified by the air cleaner, not shown, is compressed and forcibly sucked. Each part of the supercharger 24 is lubricated by the oil supplied from the oil pan 11.

The exhaust unit 4 discharges the exhaust gas generated in the combustion chamber 31 to the outside. The exhaust unit 4 includes: exhaust pipe 41, exhaust manifold 42, and ATD 43.

The exhaust pipe 41 constitutes an exhaust gas passage, and can flow the exhaust gas discharged from the combustion chamber 31 to the inside thereof.

The exhaust manifold 42 is connected to an upstream-side end portion of the exhaust pipe 41 in the direction in which exhaust gas flows. The exhaust manifold 42 leads the exhaust gas generated in each combustion chamber 31 to the exhaust pipe 41 together.

An exhaust gas temperature sensor 93 for detecting the temperature of exhaust gas is provided in the exhaust manifold 42. The exhaust temperature detected by the exhaust temperature sensor 93 is output to the ECU 90. The exhaust temperature sensor 93 may be provided at another position in the exhaust passage formed by the exhaust pipe 41.

The engine body 1 is provided with an EGR device 50 for recirculating a part of the exhaust gas to the intake side. The EGR device 50 includes: an EGR cooler 51, an EGR valve 52, and an EGR pipe 53.

The EGR pipe 53 is a path for guiding EGR gas, which is exhaust gas recirculated to the intake side, to the intake pipe 21, and is provided so as to communicate the exhaust pipe 41 (or the exhaust manifold 42) with the intake pipe 21.

The EGR cooler 51 is provided in a middle portion of the EGR pipe 53, and cools the EGR gas recirculated to the intake side.

The EGR valve 52 is provided at a middle portion of the EGR pipe 53, is provided downstream of the EGR cooler 51 in the EGR gas recirculation direction, and is configured to be capable of adjusting the amount of EGR gas recirculation.

ATD43 is: an apparatus for performing an exhaust gas aftertreatment. ATD43 purifies exhaust gas by removing harmful components such as NOx (nitrogen oxides), CO (carbon monoxide), HC (hydrocarbons), and Particulate Matter (PM) contained in the exhaust gas. ATD43 is disposed in the middle of exhaust pipe 41. The ATD43 may be disposed above the engine body 1 or may be disposed separately from the engine body 1.

The ATD43 includes: a DPF device 44 and an SCR device 45. The DPF is a short name for a Diesel Particulate Filter (Diesel Particulate Filter). SCR is an abbreviation for Selective Catalytic Reduction (Selective Catalytic Reduction).

The DPF device 44 removes carbon monoxide, nitrogen monoxide, particulate matter, and the like contained in the exhaust gas through an oxidation catalyst and a filter, which are not shown. The oxidation catalyst is composed of platinum or the like, and is a catalyst for oxidizing (combusting) unburned fuel, carbon monoxide, nitrogen monoxide, and the like contained in the exhaust gas. The filter is disposed on the exhaust gas downstream side of the oxidation catalyst, and is configured as a wall-flow type filter, for example. The filter traps particulate matter contained in the exhaust gas treated by the oxidation catalyst.

The exhaust gas passing through the DPF device 44 is sent to the SCR device 45 through a urea mixing pipe 46 connecting an outlet pipe of the DPF device 44 and an inlet pipe of the SCR device 45.

A urea solution injection unit 47 is attached near the upstream end of the urea mixing pipe 46. The urea solution injection unit 47 injects the urea solution supplied from the urea solution tank 48 into the urea mixing pipe 46. Thereby, the exhaust gas is mixed with the urea water in the urea mixing pipe 46 and guided to the SCR device 45.

The urea water tank 48 is provided separately from the engine main body 1. The urea water tank 48 is provided with a urea water temperature sensor 94 for detecting a urea water temperature. The urea water temperature detected by the urea water temperature sensor 94 is output to the ECU 90. Instead of the urea water temperature sensor 94, a urea water tank temperature sensor may be provided to indirectly detect the urea water temperature.

The SCR device 45 removes NOx contained in the exhaust gas by means of an SCR catalyst, a slip catalyst (slip catalyst). The SCR catalyst is made of a material such as ceramic that adsorbs ammonia. NOx contained in the exhaust gas is reduced by contacting the SCR catalyst adsorbed with ammonia, and is converted into nitrogen gas and water. The escape catalyst serves to prevent ammonia from being released to the outside. The fugitive catalyst is a catalyst such as platinum for oxidizing ammonia, and oxidizes the ammonia to nitrogen gas and water.

The exhaust gas passing through the SCR device 45 is discharged to the outside through a discharge pipe connected to an outlet of the exhaust gas of the SCR device 45.

Next, a configuration for supplying and injecting fuel in engine 100 of the present embodiment will be briefly described.

As shown in fig. 2, engine 100 includes: a fuel filter 72, a fuel pump 73, a common rail 74, and an injector 75.

The engine 100 draws fuel from a fuel tank 71 for storing fuel by means of a fuel pump 73. The fuel tank 71 is provided separately from the engine body 1.

The fuel sucked by the fuel pump 73 passes through the fuel filter 72, and thereby the dust and dirt mixed in the fuel are removed. Then, the fuel is supplied to the common rail 74. The common rail 74 stores fuel at high pressure and distributes the supply fuel to a plurality of (4 in the present embodiment) injectors 75.

The injector 75 injects fuel into the combustion chamber 31. The injector 75 is provided with an injector solenoid valve 76 shown in fig. 3. The ECU90 is electrically connected to the injector solenoid valve 76. The injector solenoid valve 76 opens and closes at a timing corresponding to a signal from the ECU 90. Thereby, the injector 75 injects fuel into the combustion chamber 31.

A fuel temperature sensor 95 for detecting the fuel temperature is provided at an appropriate position in the fuel path from the fuel tank 71 to the injector 75. The fuel temperature detected by the fuel temperature sensor 95 is output to the ECU 90. In order to reflect the fuel temperature in a good manner to the ambient temperature in which engine 100 is operated, fuel temperature sensor 95 is preferably provided in fuel tank 71.

The ECU90 is configured to include: a CPU that executes various arithmetic processing and control, and a ROM and a RAM as storage units are disposed in or near the engine main body 1.

The ECU90 stores various programs and a plurality of pieces of control information (for example, control maps and temperature thresholds) preset in association with control of the engine main body 1. Examples of the control map stored in the ECU90 include: and a map showing the upper limit of the rotation speed and the duration of the high idle speed limit corresponding to the temperature of each part. Examples of the temperature threshold stored in the ECU90 include: a cooling water lower limit temperature, a fuel lower limit temperature, an exhaust lower limit temperature, and the like for determining whether to execute the high idle speed limitation.

Referring to fig. 3, the ECU90 will be described in detail. Fig. 3 is a functional block diagram showing the configuration of the ECU 90.

As shown in fig. 3, the ECU90 can obtain information such as the urea water temperature, the rotation speed of the engine main body 1, the intake air temperature (fresh air temperature), the fuel temperature, the cooling water temperature, and the exhaust gas temperature based on the detection results output from various sensors. The ECU90 performs control related to the operation of the engine main body 1 based on the information reflecting the state of the engine main body 1 acquired from various sensors.

Examples of the various sensors include: the cooling water temperature sensor 91, the fresh air temperature sensor 92, the exhaust gas temperature sensor 93, the urea water temperature sensor 94, and the fuel temperature sensor 95 described above. In addition, for example, the rotation speed sensor 96 may be used.

The rotation speed sensor 96 is configured as a crank sensor for detecting the rotation of the crankshaft, for example, and detects the rotation speed of the engine 100. The rotation speed detected by the rotation speed sensor 96 is output to the ECU 90.

Next, control of the rotation speed of engine 100, that is, high idle speed limitation, by ECU90 at the time of startup will be described with reference to fig. 4. Fig. 4 is a block diagram illustrating the high idle speed limitation at the time of startup.

In engine 100 of the present embodiment, ECU90 limits the high idle speed of engine 100 when a predetermined condition is satisfied at the time of starting engine 100. The high idle speed limit is: control such that the rotational speed of engine 100 does not exceed the set limit rotational speed. When the high idle speed limitation is executed, the rotation speed of engine 100 does not further increase after reaching the set limit rotation speed even if the accelerator is depressed.

The purpose of this high idle speed limitation is to: in particular, when the temperature in the operating environment of engine 100 is extremely low and the operating state of engine 100 at the time of starting is not suitable for high-speed rotation, high-speed rotation is avoided and various parts (e.g., supercharger 24 and the like) of engine body 1 are protected.

Specific examples of the operation state unsuitable for high-speed rotation are as follows. That is, if the temperature of the engine body 1, i.e., the engine temperature, does not sufficiently rise at the time of starting, the oil is not sufficiently heated, and the fluidity is poor. Therefore, the oil does not sufficiently enter the respective portions of the engine main body 1 at once. As a result, the respective parts of the engine body 1 are not sufficiently lubricated, and therefore, there is a possibility that seizure or the like occurs at the time of high-speed rotation.

In the engine 100 of the present embodiment, as shown in fig. 4, after the engine 100 is started, the ECU90 acquires the cooling water temperature, the fuel temperature, and the exhaust gas temperature from the cooling water temperature sensor 91, the fuel temperature sensor 95, and the exhaust gas temperature sensor 93, respectively, and determines whether to execute the high idle speed restriction based on the acquired cooling water temperature, fuel temperature, and exhaust gas temperature.

Specifically, the ECU90 compares the acquired cooling water temperature, fuel temperature, and exhaust gas temperature with the cooling water lower limit temperature, fuel lower limit temperature, and exhaust gas lower limit temperature of the respective thresholds. When any one of the cooling water temperature, the fuel temperature, and the exhaust gas temperature is equal to or higher than a corresponding threshold value, the ECU90 causes the engine 100 to perform a normal operation. That is, the rotation speed of engine 100 for which the high idle speed restriction is not executed is made to follow the accelerator instruction value, which is the rotation speed corresponding to the accelerator opening degree after the driver operation. This can avoid the execution of the high idle speed restriction when the operating state of engine 100 is normal, and therefore, the startability of engine 100 can be maintained good.

On the other hand, the ECU90 executes the high idle speed restriction in the case where the cooling water temperature is lower than the cooling water lower limit temperature, the fuel temperature is lower than the fuel lower limit temperature, and the exhaust gas temperature is lower than the exhaust gas lower limit temperature. That is, ECU90 controls the rotation of engine 100 by controlling, for example, the fuel injection amount, the intake air amount, and the like so that the rotation speed of engine 100 does not exceed the set limit rotation speed.

Note that the execution of the high idle speed limit may be set not to be executed by a special operation by a serviceman or the like. For example, as shown in fig. 4, in the above-described execution determination of the high idle speed limit, an execution flag (e.g., 0/1) set by a special operation is used as a condition.

That is, when the execution flag is set to "1" by an operation of the driver or the like, the execution determination is valid, and when the predetermined condition (that is, when all of the cooling water temperature, the fuel temperature, and the exhaust gas temperature are lower than the threshold values) is satisfied, the high idle speed restriction is executed.

On the other hand, when the execution flag is set to "0" by an operation of the driver or the like, the execution determination is invalidated, and even when the predetermined condition is satisfied, the high idle speed restriction is set not to be forcibly executed.

When it is determined that the predetermined condition is satisfied and the fast idle speed limitation is executed, the ECU90 obtains a first upper limit rotation speed, a first limitation time, a second upper limit rotation speed, and a second limitation time, respectively.

The first upper limit rotational speed and the second upper limit rotational speed are limit rotational speeds used for high idle speed limit. The first and second limit times are durations of high idle speed limits.

The first upper limit rotation speed and the first limit time are determined based on the current operating state of engine 100 (further, the temperature of engine body 1, that is, the engine temperature). The second upper limit rotation speed and the second limit time are determined based on the ambient temperature in the operating environment of engine 100.

When the first upper limit rotation speed and the first limit time are obtained, the ECU90 uses, as the engine temperature, the lowest temperature among the cooling water temperature, the fuel temperature, and the exhaust gas temperature that can reflect the temperature state of the engine main body 1. As a result, the first upper limit rotation speed and the first limit time can be obtained under the most severe temperature conditions, and therefore the engine body 1 can be protected more reliably.

In the ECU90, the following settings may be set: at least one of the cooling water temperature, the fuel temperature, and the exhaust gas temperature is not used when the first upper limit rotation speed and the first limit time are obtained. This configuration is represented by the selector switch of fig. 4. As for the temperature set not to be used for calculation, as shown in fig. 4, the upper limit value of the desirable range of the temperature is output as the dummy temperature. Since the minimum value of the temperature is adopted as described above, the dummy temperature is not substantially used for calculation.

The ECU90 obtains the first upper limit rotation speed and the first limit time using the first limit rotation speed map and the first limit time map stored in advance, based on the engine temperature obtained as described above. The first limit rotational speed map and the first limit time map may be expressed as, for example, a two-dimensional table that correlates the limit rotational speed or the limit time with the engine temperature.

The ECU90 uses the fresh air temperature, the fuel temperature, and the urea water temperature as the temperature (ambient temperature) of the operating environment that is the external environment in which the engine 100 operates.

The fresh air is air newly taken in from the outside via the supercharger 24, and therefore, the temperature of the fresh air reflects the temperature of the outside air at least to some extent.

As described above, since fuel tank 71 and urea water tank 48 are disposed away from engine body 1, they are less susceptible to heat generated during operation of engine 100. Therefore, the fuel temperature and the urea water temperature detected in fuel tank 71 and urea water tank 48 reflect the temperature of the external environment of engine 100 at least to some extent.

The ECU90 uses, as the ambient temperature, the lowest temperature among the fresh air temperature, the fuel temperature, and the urea water temperature that can reflect the ambient temperature of the external environment in which the engine 100 is operating. As a result, the second upper limit rotation speed and the second limit time can be obtained under the most severe environmental temperature conditions, and therefore, the respective portions of the engine body 1 can be protected more reliably.

In the ECU90, the following settings may be set: at least one of the fresh air temperature, the fuel temperature, and the urea water temperature is not used when the second upper limit rotation speed and the second limit time are obtained. This configuration is represented by the selector switch of fig. 4. As for the temperature set not to be used for calculation, as shown in fig. 4, the upper limit value of the desirable range of the temperature is output as the dummy temperature. Since the minimum value of the temperature is adopted as described above, the dummy temperature is not substantially used for calculation.

The ECU90 obtains the second upper limit rotation speed and the second limit time using the second limit rotation speed map and the second limit time map stored in advance, based on the engine temperature obtained as described above. The second limit rotational speed map and the second limit time map may be expressed as, for example, a two-dimensional table that correlates the limit rotational speed or the limit time with the ambient temperature.

As described above, after the first upper limit rotational speed and the first limit time and the second upper limit rotational speed and the second limit time are obtained, the ECU90 sets the smaller one of the obtained first upper limit rotational speed and the second upper limit rotational speed (i.e., the smaller one of the obtained rotational speeds) as the limit rotational speed in the high idle speed limit to control the rotation of the engine main body 1.

The ECU90 sets the larger of the first and second limit times (the longer of the first and second limit times) as the duration (execution time) of the high-idle speed limit.

After the duration of the high idle speed limit is reached, the high idle speed limit may be automatically released, or may be released according to a driver's throttle instruction as shown in fig. 5.

When the driver instructs to cancel the high idle speed restriction, for example, as shown in fig. 5, after the duration of the high idle speed restriction is ended, the ECU90 compares the accelerator instruction value, which is the engine speed corresponding to the accelerator opening acquired from an accelerator opening detecting unit, not shown, with the restricted speed of the high idle speed restriction. When determining that the accelerator instruction value is equal to or less than the limited rotation speed, the ECU90 sets the limited rotation speed to gradually increase for a predetermined time. After a predetermined time has elapsed, the limited rotation speed is made to follow the accelerator instruction value.

As described above, engine 100 of the present embodiment includes engine body 1 and ECU 90. The ECU90 controls the engine body 1. The ECU90 is configured to: when a predetermined condition is satisfied at the time of startup, the high idle speed limitation can be executed. When the fast idle speed limitation is executed, the ECU90 obtains a first upper limit rotation speed as an upper limit value of the fast idle speed and a first limitation time as a duration of the fast idle speed limitation based on the engine temperature at the time of startup. The ECU90 obtains a second upper limit rotation speed as an upper limit value of the fast idle rotation speed and a second limit time as a duration of the fast idle limit based on the ambient temperature. The ECU90 executes the high idle speed limitation based on any one of the first and second upper rotation speeds and any one of the first and second limitation times.

This can restrict high-speed rotation when the engine temperature is low. Therefore, the occurrence of seizure in the supercharger or the like due to insufficient lubrication can be prevented.

In engine 100 of the present embodiment, ECU90 sets the rotation speed limit value for the fast idle speed limit, which is the smaller of the first and second upper rotation speeds obtained.

This enables the limited rotation speed during the high idle speed limitation to be set more appropriately.

In engine 100 of the present embodiment, ECU90 sets the longer of the calculated first and second limiting times as the duration of the high-idle speed limitation.

This enables the duration of the high idle speed restriction to be set more appropriately.

In engine 100 of the present embodiment, ECU90 uses at least the lowest temperature among the cooling water temperature, the fuel temperature, and the exhaust gas temperature as the engine temperature.

As a result, the first upper limit rotation speed and the first limit time can be calculated using the strictest temperature condition among the temperatures of the respective portions related to the engine temperature. Therefore, the high idle speed restriction more suitable for the operating state of the engine can be executed.

The engine 100 of the present embodiment includes an ATD 43. ATD43 is configured to: the urea water supplied from the urea water tank 48 can be mixed with the exhaust gas to remove nitrogen oxides contained in the exhaust gas. The ECU90 uses the lowest temperature among the fresh air temperature, the fuel temperature, and the urea water temperature as the ambient temperature.

Thus, by adopting the most severe conditions, the second upper limit rotation speed and the second limit time that appropriately reflect the operating environment of engine 100 can be obtained. Therefore, high-speed rotation at low temperatures can be avoided more reliably.

In engine 100 of the present embodiment, as the predetermined condition for executing the high idle speed limitation at the time of startup, at least all of the cooling water temperature, the fuel temperature, and the exhaust gas temperature are lower than the respective threshold values.

Thereby, unnecessary execution of the high idle speed restriction can be avoided. Therefore, startability of engine 100 can be improved.

Although the preferred embodiments of the present invention have been described above, the above configuration may be modified as follows.

The engine 100 may not be provided with the EGR device 50. In this case, the cooling water temperature sensor 91 may be disposed at any position of the intake passage formed by the intake pipe 21, or may be disposed in the intake manifold 23.

The exhaust gas temperature sensor 93 may not be provided. In this case, for example, the EGR gas temperature detected by an unillustrated EGR gas temperature sensor provided in the EGR device 50 may be employed as the exhaust gas temperature.

The fuel temperature used when the first upper limit rotation speed is obtained and the fuel temperature used when the second upper limit rotation speed is obtained may be detected by different temperature sensors, respectively. For example, the fuel temperature used when the first upper limit rotation speed is obtained is detected by a fuel temperature sensor provided at a position close to the injector 75, and the fuel temperature used when the second upper limit rotation speed is obtained is detected by a fuel temperature sensor provided in the fuel tank 71.

As the engine temperature, the temperature of the engine oil may also be used. In this configuration, the lowest temperature among the cooling water temperature, the fuel temperature, the exhaust gas temperature, and the temperature of the engine oil is used as the engine temperature.

Description of the reference numerals

1 Engine body

90ECU (control unit)

100 engine