JPH08218929A - Overheat preventing device for diesel engine - Google Patents

Abstract

PURPOSE: To provide an overheat preventing device in a diesel engine which is operated properly according to an operating condition of an engine. CONSTITUTION: In a diesel engine 1, a referential temperature THWOV is calculated on the basis of an engine rotating speed and an acceleration opening degree ACCP which are read-in respectively by an ECU 60. The temperature THW of cooling water which is read-in is compared with a referential temperature THWOV, and judgement is carried out, and then it is judged whether the engine 1 is in an overheat condition or not. In case where overheat is judged, an air conditioner 52 is stopped and the fuel injection amount is reduced. Since the referential temperature THWOV is changed (calculated) according to the operating condition of the engine, the overheat condition of the engine 1 can be judged properly in a differential operating condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine overheat prevention device.

[0002]

2. Description of the Related Art As a device of this type, when the cooling water temperature of a diesel engine (hereinafter referred to as an engine) exceeds a preset reference temperature, the fuel injection amount is reduced or auxiliary equipment such as an air conditioner or an alternator is used. There is one that reduces the load on the engine by stopping the engine and prevents overheating.

More specifically, the reference temperature is the temperature of the cooling water with respect to the temperature of a thermally harsh portion (for example, around the combustion chamber) in the engine operating condition under a certain condition. It is set based on whether to indicate the value.
That is, the reference temperature is set based on the correlation between the two temperatures. Then, assuming the temperature around the combustion chamber from the detected water temperature, and if the detected water temperature exceeds the reference temperature, the temperature around the combustion chamber is over the value indicating the overheat state, and the engine is in the overheat state. Make a decision.

[0004]

However, at high engine speed and high load of the engine, the temperature rise around the combustion chamber is more rapid than that at low engine speed and low load. It is necessary to take measures against overheat early. That is, the reference temperature must be set lower than that at the time of low rotation and low load.

Further, when the flow velocity of the cooling water changes due to the change of the engine speed or the temperature distribution around the combustion chamber changes due to the engine load, the correlation between the temperature around the combustion chamber and the cooling water temperature changes. . In other words, as the engine becomes higher in rotation and load, the driving force of the pump that is drivingly connected to the engine and circulates the cooling water becomes larger (the flow speed of the cooling water becomes faster). The temperature will rise. Therefore, the temperature difference between the cooling water temperature around the combustion chamber in which the temperature state of the engine directly appears and the cooling water temperature in the detection portion becomes large, and the temperature state around the combustion chamber cannot be accurately estimated from the detected water temperature.

Therefore, it is not appropriate to use the reference temperature for determining the overheat state in all operating states. For this reason, the following problems have occurred in the prior art.

For example, when the reference temperature is set according to the state of the engine under high rotation and high load, even if the detected water temperature exceeds the reference temperature when the engine is under low rotation and low load, the surroundings of the combustion chamber The temperature may be an allowable temperature for overheating. For this reason, the overheat prevention device is operated at an allowable value, which causes a disadvantage such as an unnecessary decrease in engine performance due to a reduction in the fuel injection amount.

On the contrary, when the reference temperature is set according to the state of low engine speed / low load, overheating is prevented even if the temperature around the combustion chamber exceeds the allowable value at high engine speed / high load. The device did not operate and there was a risk of engine blow due to overheating.

The present invention has been made by paying attention to the problems existing in the above-mentioned prior art, and an object thereof is to provide an overheat prevention device for a diesel engine which operates properly according to an operating state of the diesel engine. To provide.

[0010]

In order to achieve the above object, the invention of claim 1 is, as shown in FIG. 1, a temperature detecting means M2 for detecting the temperature of the coolant of the diesel engine M1.
And an overheat judging means M3 for judging the overheat state of the diesel engine M1 based on whether or not the value detected by the temperature detecting means M2 is equal to or higher than the reference temperature.
And an engine load limiting means M5 for limiting the load element M4 of the diesel engine M1 when the diesel engine M1 is determined to be overheated by the overheat determination means M3. In the prevention device, a diesel engine including an operating state detecting means M6 for detecting an operating state of the diesel engine M1 and a reference temperature changing means M7 for changing the reference temperature based on a detection value by the operating state detecting means M6. Is an overheat prevention device.

According to a second aspect of the present invention, the load element M4 is the fuel injection amount, and the engine load limiting means M5 reduces the fuel injection amount M4. In the invention of claim 3, the load element M4 is an auxiliary machine driven by the diesel engine M1, and the engine load limiting means M5 dissociates the drive transmission system between the auxiliary machine M4 and the diesel engine M1. is there.

[0012]

[Function] Diesel engine (hereinafter referred to as engine)
During operation of M1, the temperature of the coolant of the engine M1 is detected by the temperature detecting means M2. The overheat determination means M3 determines the overheat state of the engine M1 based on whether or not the value detected by the temperature detection means M2 is equal to or higher than the reference temperature. Then, the engine load limiting means M5 limits the load element M4 of the engine M1 when the overheat determining means M3 determines that the engine M1 is overheated.

However, the reference temperature is the temperature of the coolant in a certain operating state of the engine M1 and the engine M1.
It is set on the basis of the correlation with the thermally harsh condition of No. 1, for example, the temperature around the combustion chamber. Therefore, as described in "Problems to be Solved by the Invention", when the operating state of the engine M1 at the time of setting the reference temperature and the actual operating state are different, the coolant temperature and the temperature around the combustion chamber are Correlation breaks down. That is, if the overheat state is determined using the same reference temperature in different operating states, the overheat state of the engine M1 is not properly determined, and as a result, the overheat prevention device operates unnecessarily or is necessary. Nevertheless, it is not operated.

Therefore, in the invention of claim 1, the operating state detecting means M6 detects the operating state of the engine M1. Further, the reference temperature changing means M7 changes the reference temperature based on the value detected by the operating state detecting means M6.
Therefore, the overheat determination means M3 determines whether the engine M1 is based on the reference temperature changed according to the operating state.
Appropriately determine the overheat state of. Then, the engine load limiting means M5 limits the load element M4 of the engine M1 based on the result of the proper determination. In other words, the overheat prevention device of the present invention is used in the engine M1.
It is operated properly according to the operating state of.

In the second aspect of the invention, when the overheat determining means M3 determines that the engine M1 is in the overheat state, the engine load limiting means M5 reduces the fuel injection amount M4. Therefore, the load on the engine M1 is reduced, and the engine M1 can escape from the overheated state.

In the third aspect of the present invention, when the overheat determining means M3 determines that the engine M1 is in an overheated state, the engine load limiting means M5 causes the drive transmission system for the auxiliary machinery M4 and the engine M1. Is dissociated. Therefore, the load on the engine M1 is reduced, and the engine M1 can escape from the overheated state.

[0017]

EXAMPLE An example embodying the present invention will be described below.
FIG. 2 shows an automobile diesel engine (hereinafter referred to as an engine) 1 equipped with an overheat prevention device of this embodiment.
2 is a schematic configuration diagram showing a distribution type fuel injection pump (hereinafter, referred to as a fuel injection pump) for injecting fuel into the engine 1.
Fuel injection pump). The fuel injection pump 2 includes a drive pulley 4 drivingly connected to a crankshaft 3 of the engine 1 via a belt or the like (not shown). Then, the fuel injection pump 2 is driven by the rotation of the drive pulley 4, and the fuel is pressure-fed to the fuel injection nozzle 5 provided for each cylinder of the engine 1 to inject the fuel.

In the fuel injection pump 2, the drive pulley 4 is attached to the tip of the drive shaft 6. The fuel feed pump 7, which is a vane type pump,
It is connected in the middle of the drive shaft 6. The disc-shaped pulsar 8 is attached to the base end side of the drive shaft 6. The base end of the drive shaft 6 is connected to the cam plate 9 via a coupling (not shown). The roller ring 10 is interposed between the pulsar 8 and the cam plate 9, and the cam roller 11 is attached to the roller ring 10 so as to face the cam face 9α of the cam plate 9. The cam plate 9 is constantly urged and engaged with the cam roller 11 by the spring 12.

The fuel pressurizing plunger 13 is integrally rotatably attached to the cam plate 9, and the rotational force of the drive shaft 6 is transmitted to the cam plate 9 through a coupling. While the cam plate 9 and the plunger 13 rotate, they are reciprocally driven in the left-right direction in FIG. The plunger 13 is fitted into a cylinder 15 formed in the pump housing 14, and a high-pressure chamber 16 is formed between the tip end surface (the right end surface in the drawing) of the plunger 13 and the inner bottom surface of the cylinder 15. The suction groove 17 and the distribution port 18 are provided in the plunger 13
As many as the number of cylinders of the engine 1 are formed on the outer periphery of the front end side of. Distribution passage 19 and suction port 20
Are formed in the pump housing 14 so as to correspond to the suction groove 17 and the distribution port 18.

When the fuel feed pump 7 is driven based on the rotation of the drive shaft 6, fuel from a fuel tank (not shown) is supplied into the fuel chamber 22 through the fuel supply port 21. Further, during the intake stroke in which the plunger 13 moves (returns) to the left in the drawing and the high pressure chamber 16 is decompressed, one of the intake grooves 17 communicates with the intake port 20 to move from the fuel chamber 22 to the high pressure chamber 16. Fuel is introduced into. On the other hand, the plunger 13 moves to the right in the figure (forward movement).
Then, in the compression stroke in which the high pressure chamber 16 is pressurized, fuel is pressure-fed from the distribution passage 19 to the fuel injection nozzle 5 of each cylinder and injected.

The spill passage 23 for fuel overflow is formed in the pump housing 14 and connects the high pressure chamber 16 and the fuel chamber 22. The electromagnetic spill valve 24 is provided in the middle of the spill passage 23. The electromagnetic spill valve 24 is a normally open valve, and when the coil 25 is in the non-energized (off) state, the valve body 26 is opened and the fuel in the high pressure chamber 16 overflows into the fuel chamber 22. In addition, the coil 25 is energized (ON)
As a result, the valve body 26 is closed and the overflow of fuel from the high pressure chamber 16 to the fuel chamber 22 is stopped.

Therefore, by controlling the energization time of the electromagnetic spill valve 24, the electromagnetic spill valve 24 is controlled to open / close, and the overflow amount of fuel from the high pressure chamber 16 to the fuel chamber 22 is adjusted. . Then, by opening the electromagnetic spill valve 24 during the compression stroke of the plunger 13, the high pressure chamber 1
The fuel in 6 is depressurized and the fuel injection from the fuel injection nozzle 5 is stopped. In other words, even if the plunger 13 moves forward, the high pressure chamber 16 remains open while the electromagnetic spill valve 24 is open.
The fuel pressure inside does not rise, and fuel injection from the fuel injection nozzle 5 is not performed. Further, the fuel injection amount from the fuel injection nozzle 5 is controlled by adjusting the timing of closing / opening the electromagnetic spill valve 24 during the forward movement of the plunger 13.
In the present embodiment, this fuel injection amount is one load element of the engine 1.

Next, the engine 1 will be described.
As shown in FIG. 2, the cylinder 27 constituting each cylinder is
A piston 30, which is formed on a cylinder block 28 and is supported by the crankshaft 3 via a rod 29, is inserted and arranged in the cylinder 27. Cylinder head 3
1 is attached to the upper part of the cylinder block 28. The main combustion chamber 32 is formed by being surrounded by the cylinder 27, the piston 30, and the cylinder block 28. In the figure, reference numeral 33 denotes an auxiliary combustion chamber, and the auxiliary combustion chamber 33 is connected to the main combustion chamber 32. The combustion injection nozzle 5 is mounted so as to face the sub combustion chamber 33, and the fuel injected from the combustion injection nozzle 5 is supplied to the sub combustion chamber 33.

The cooling water passage 34 is formed on the outer circumference of the cylinder 27 in the cylinder block 28, and constitutes a cooling system for the engine 1 together with the water passage 34, a radiator, a cooling water pump and the like (not shown). The cooling water pump is driven by the engine 1, and therefore the cooling water passage 34-
Cooling water as an engine coolant is circulated between the radiators.

The intake pipe 35 and the exhaust pipe 36 are provided in the cylinder head 31, and the main combustion chamber 32 and the auxiliary combustion chamber 33 are provided.
Be communicated to. Turbocharger 37 compressor 3
8 is provided in the intake pipe 35, and the turbine 39 integrally rotated with the compressor 38 is provided in the exhaust pipe 36. The waste gate valve 40 is attached to the exhaust pipe 36 and adjusts the supercharging pressure by the turbocharger 37. The throttle valve 41 is provided in the middle of the intake pipe 35 and is opened / closed in conjunction with the accelerator pedal 42.

An air conditioning device (hereinafter, referred to as an air conditioner) 52, which is an auxiliary machine, as another load element for the engine 1, has its refrigerant compressor 5
3 is an electromagnetic clutch 54 and a belt 5 as a drive transmission system.
It is drivingly connected to the crankshaft 3 of the engine 1 via 5. Then, by connecting the electromagnetic clutch 54, the refrigerant compressor 53 is driven by the engine 1 to compress the refrigerant. Further, when the electromagnetic clutch 54 is disengaged, the refrigerant compressor 53 is stopped.

The following sensors are provided as sensors for detecting the operating state of the engine 1. An intake air temperature sensor 44 that detects the intake air temperature of the air taken into the intake pipe 35 via the air cleaner 43, and is mounted on the upper part of the roller ring 10 so as to face the outer peripheral surface of the pulsar 8 and corresponds to the engine speed. Signal (hereinafter,
Revolution speed sensor 4 for detecting engine revolution speed NE)
5, accelerator opening sensor 46 for detecting accelerator opening ACCP from the opening / closing position of throttle valve 41, intake pipe 3
Intake pressure sensor 47 for detecting supercharging pressure in 5, cooling water passage 3
A reed switch 51 is turned on by a water temperature sensor 48 for detecting the water temperature THW of the cooling water flowing in 4 and a magnet 50 rotated by the rotation of a gear in a transmission (not shown).
Vehicle speed sensor 49 that detects the traveling speed (vehicle speed) by turning off
Is provided.

The rotation speed sensor 45 and the accelerator opening sensor 46 constitute an operating condition detecting means in this embodiment. Further, the water temperature sensor 48 constitutes a temperature detecting means.

Next, an electronic control unit (hereinafter referred to as ECU) 60 constituting the overheat judging means, the engine load limiting means and the reference temperature changing means in this embodiment will be explained.

As shown in FIG. 3, the ECU 60 includes a central processing unit (CPU) 61, a read-only memory (ROM) 6 which stores a predetermined control program, maps and the like.
2. The theoretical operation circuit is composed of a readable / writable memory (RAM) 63 for temporarily storing operation results and the like.

The sensors 44 to 49 and the air conditioner operating device 56 are connected to the ECU 60 via an external input circuit 65. In addition, the electromagnetic spill valve 24 and the air conditioner 5
2 (electromagnetic clutch 54) via the external output circuit 64
It is connected to the CU 60.

Then, the ECU 60 uses the sensors 44-4.
The detection signal from 9 and the operation signal from the air conditioner operation device 56 are read as input values. In addition, each sensor 44-4
The electromagnetic spill valve 24 is controlled based on the input value from 9.
Adjust the fuel injection amount. Furthermore, the air conditioner operating device 56
Based on the operation signal from the
The control of the air conditioner 52 including turning off is performed. Moreover, the overheat state of the engine 1 is determined based on the input values from the sensors 44 to 49, and the countermeasure against overheat is taken.

Next, the operation and effect of this embodiment constructed as described above will be described. The flowchart of FIG. 4 shows an “overheat countermeasure routine” of the engine 1 among the respective processes executed by the ECU 60, which is executed by a regular interruption every predetermined time. Further, the flow chart of FIG. 5 shows a “fuel injection amount calculation routine”, and the calculation of the fuel injection amount QFIN is performed by the process of FIG.
The result of overheat determination according to the flowchart of FIG. It is assumed that the air conditioner 52 is in the “on” state at the start of this routine.

First, the "overheat countermeasure routine" of FIG. 4 will be described. When you move to this routine,
In step 101, the engine speed NE and the accelerator opening ACCP are read based on the respective detected values from the rotation speed sensor 45 and the accelerator opening sensor 46, and the routine proceeds to step 102.

In step 102, the reference temperature THWOV is set based on the read engine speed NE and the accelerator opening ACCP. Same reference temperature T
HWOV is the engine speed NE and accelerator opening AC
It is calculated from a map (not shown) using CP as a parameter. In the region where the engine speed NE and the accelerator opening ACCP indicate the high load / high speed state of the engine 1 in the same map, there is a rapid temperature increase compared to during normal operation and there is a temperature difference in each part of the cooling water temperature. Considering that the reference temperature THWOV becomes higher (that is, the actual temperature around the combustion chamber becomes higher than that in normal operation even if the detected water temperature is the same as in normal operation). It is set lower than the comparison. Further, in the region showing the low load / low rotation state, the reference temperature THWOV is set higher than in the normal operation, contrary to the high load / high rotation state.

Next, at step 103, the cooling water temperature THW is read based on the detection value from the water temperature sensor 48. Then, the process proceeds to step 104, where the read water temperature THW is the previously calculated reference temperature THWO.
It is determined whether or not it is V or more.

In step 104, the detected water temperature T
If HW is lower than the reference temperature THWOV, that is, if it is determined that the engine 1 is not in the overheat state, the process proceeds to step 105. In step 105, the "ON" state of the air conditioner 52 is continued. Then, the routine proceeds to step 106, where "0" is reset to the fuel injection amount reduction flag F, and this routine is ended.

On the other hand, if it is determined in step 104 that the detected water temperature THW is equal to or higher than the reference temperature THWOV, that is, if the engine 1 is in the overheat state, the process proceeds to step 107 to take measures against overheat.

That is, in step 107, the "off" signal is issued to the air conditioner 52 in the "on" state. That is, the electromagnetic clutch 54 is forcibly disengaged. Further, the routine proceeds to step 108, the fuel injection amount reduction flag F is set to "1", and this routine is ended.

In this routine, step 1
If it is determined that the air conditioner 52 is overheated in 04 and the air conditioner 52 is forcibly stopped in step 107, the air conditioner 52 will not operate at the start of the next routine.
Is in the off state even though is in the "on" position. Therefore, in the next routine, if it is determined in step 104 that it is not overheated, step 10
In No. 5, the air conditioner operating device 56 is in the forced stop state.
Is on, the electromagnetic clutch 54 is connected and the air conditioner 52 is returned to the on state.

Next, the "fuel injection amount calculation routine" of FIG.
Will be described. In the same routine, the fuel injection amount QFI
In calculating N, the overheat determination result of the engine 1 by the "overheat countermeasure routine" of FIG. 4, specifically, the fuel injection amount reduction flag F is affected.

First, at step 201, the engine speed NE, throttle opening ACCP, vehicle speed, intake air temperature and intake air pressure are read, and the routine proceeds to step 202. In step 202, the basic fuel injection amount QBASE is calculated based on the read engine speed NE and the accelerator opening ACCP. The basic fuel injection amount QBASE is the engine speed NE and the accelerator opening degree ACC.
It is obtained by referring to a map having P as a parameter.

Next, the routine proceeds to step 203, where the maximum fuel injection amount QFULL is calculated. This maximum fuel injection amount QFU
LL means the upper limit value of the fuel injection amount with respect to the intake air of the engine 1, and the engine speed N read previously.
It is calculated based on E, intake air pressure, intake air temperature, and the like.

Then, the routine proceeds to step 204, where it is judged in the above-mentioned "overheat countermeasure routine" whether or not the fuel injection amount reduction flag F is "1".
If it is determined in step 204 that the fuel injection amount reduction flag F is not "1", the process proceeds to step 205 and the fuel injection amount is not reduced. That is, in step 205, the final fuel injection amount QFIN is calculated by the formula: MIN [QBASE, QFULL]. This formula is based on the previously calculated basic fuel injection amount QBASE and maximum fuel injection amount Q.
This means that the smaller one of FULL is selected (validated) as the final fuel injection amount QFIN.

On the other hand, if it is determined in step 204 that the fuel injection amount reduction flag F is "1", the fuel injection amount is reduced. That is, the routine proceeds to step 206, where the fuel injection amount correction amount ΔQ is calculated from the read throttle opening ACCP and vehicle speed. Next, the process proceeds to step 207, and the formula: MIN [QBASE, QFULL]
The final fuel injection amount QFIN is calculated from −ΔQ.

Then, the ECU 60 adjusts the fuel injection amount by controlling the electromagnetic spill valve 24 based on the calculated final fuel injection amount QFIN. When the detected cooling water temperature THW becomes equal to or higher than the reference temperature THWOV calculated according to the operating state (overheat state), the air conditioner is turned off and the fuel injection amount is reduced.
Therefore, when the air conditioner 52 is in operation, the electromagnetic clutch 54 is disengaged so that the air conditioner 52 is forcibly stopped. Further, the electromagnetic spill valve 24 is controlled by the final fuel injection amount QFIN after subtracting the reduced amount ΔQ, so that the fuel injection amount is reduced as compared with the case where it is not in the overheat state. As a result, the load on the engine 1 is reduced and the overheated state can be escaped.

As described above, in the present embodiment, the reference temperature THWOV is changed (calculated) in accordance with the operating state of the engine 1 in step 102, and the cooling water temperature THW detected in step 104 and the calculated reference temperature. T
It is designed to compare and judge with HWOV. Therefore, even if the operating state of the engine 1 is different, the overheat state can be accurately determined, and as a result, the present overheat prevention device is operated properly. That is, unlike the conventional case, there is no problem that the device is operated at an allowable value and the engine performance is unnecessarily lowered, or that the device is not operated in the overheated state.

Further, the diesel engine 1 of this embodiment is equipped with the turbocharger 37, and has a larger output than the naturally aspirated engine of the same type and the same displacement, that is,
Thermally harsh. On the other hand, by mounting the turbocharger 37, the space in the engine room is restricted, the space of the cooling system is reduced, and the cooling performance is deteriorated. As described above, in the engine 1 having a condition in which overheat is likely to occur, it is particularly effective to properly determine the overheat state of the engine 1 even if the operation is performed efficiently (even if the engine performance is not unnecessarily reduced or the engine is overheated). It does not cause engine blow etc. without operating the device). Therefore, the installation of the overheat prevention device of this embodiment is particularly effective in this type of engine 1.

The following embodiments can be carried out without departing from the spirit of the present invention. (1) In the above embodiment, the cooling water temperature determination is performed in two stages of the reference temperature and the limit temperature (> reference temperature), and the detected water temperature T
If HW exceeds the reference temperature, reduce the fuel injection amount,
If the temperature exceeds the limit temperature, stop fuel injection. (2) As a measure against overheating, only stopping the auxiliary equipment,
Alternatively, only reduce the fuel injection amount. (3) When calculating the reference temperature, reflect the traveling environment of the vehicle (airspeed, humidity, rain, snow, high and lowlands, etc.), vehicle speed, intake air temperature, etc. (4) As an auxiliary device other than the air conditioner 52, for example, it should be embodied in an alternator. (5) In the above embodiment, the fuel feed pump 7 was a vane type pump, but other pumps such as a swash plate type piston pump may be used. (6) The turbocharger 37 configuration of the engine 1 is deleted to make it a naturally aspirated engine. It may also be embodied in an engine with a supercharger. (7) In FIG. 2, 70 shows a timer device for controlling the fuel injection timing. The timer device 70 changes the position of the roller ring 10 with respect to the rotation direction of the drive shaft 6 to change the timing at which the cam face 9α engages with the cam roller 11, that is, the reciprocating drive timing of the cam plate 9 and the plunger 13. It is a thing. Then, in accordance with the reduction of the fuel injection amount in the above embodiment,
Control the timer device 70 so as to advance the fuel injection timing. In this way, overheating of the engine 1 can be prevented without reducing the engine output. (8) In the above examples, the coolant was embodied in cooling water. That is, the diesel engine 1 was a water-cooled engine. Change this and embody it in an oil-cooled engine that uses cooling oil as the coolant.

The technical idea which can be understood from the above embodiment will be described below. In claim 2, the diesel engine is configured so that the fuel injection timing is advanced in accordance with the reduction of the fuel injection amount by the engine load limiting means. Overheat prevention device.

In this way, overheating of the engine 1 can be prevented without reducing the engine output. -Decreasing amount ... In the present specification, reducing amount includes, for example, not only reducing the fuel injection amount but also stopping the fuel injection.

[0052]

According to the present invention having the above structure, the operating condition detecting means detects the operating condition of the diesel engine. Further, the reference temperature changing means changes the reference temperature based on the value detected by the operating state detecting means. Therefore, the overheat determination means appropriately determines the overheat state of the engine based on the reference temperature changed according to the operating state. Then, the engine load limiting means limits, for example, the fuel injection amount or the operation of the auxiliary machinery as a load element of the engine based on the result of the proper determination. That is, the present overheat prevention device is properly operated according to the operating state of the engine.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram illustrating a basic conceptual configuration of the present invention.

FIG. 2 is a schematic configuration diagram of a diesel engine and its overheat prevention device.

FIG. 3 is a block diagram showing a configuration of an ECU and the like.

FIG. 4 is a flowchart showing an overheat countermeasure routine.

FIG. 5 is a flowchart showing a fuel injection amount calculation routine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 24 ... Electromagnetic spill valve which controls the fuel injection amount as a load element of an engine, 34 ... Cooling water channel in which the cooling water as a coolant flows, 45 ... Rotation speed sensor as an operating state detection means, 46 ... An accelerator opening sensor as an operating state detecting means, a water temperature sensor as a temperature detecting means 48, an air conditioner as a load element of the engine 52, an overheat determining means, an engine load limiting means and a reference temperature changing means. ECU.

Claims (3)

[Claims] 1. Overheat determination for determining an overheat state of a diesel engine based on temperature detection means for detecting the temperature of a coolant of a diesel engine and whether or not a value detected by the temperature detection means is a reference temperature or higher. Means, by the overheat determination means, when it is determined that the diesel engine is in an overheat state, in the diesel engine overheat prevention device comprising an engine load limiting means for limiting the load element of the diesel engine, An overheat prevention device for a diesel engine, comprising: an operating state detecting means for detecting an operating state of the diesel engine; and a reference temperature changing means for changing the reference temperature based on a value detected by the operating state detecting means. 2. The overheat prevention device for a diesel engine according to claim 1, wherein the load element is a fuel injection amount, and the engine load limiting means reduces the fuel injection amount. 3. The diesel engine according to claim 1, wherein the load element is an auxiliary machine driven by a diesel engine, and the engine load limiting means separates a drive transmission system between the auxiliary machine and the diesel engine. Overheat prevention device.