JPH09209816A - Heating state detection device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly detect a heating state of an engine. SOLUTION: A water temperature sensor 48 is installed on a cylinder block 28 of a diesel engine 1, and temperature of cooling water in a block side cooling water passage 34a is detected by the sensor 48. A CPU of an electronic control device (ECU) 60 judges whether cooling water temperature detected by the water temperature sensor 48 becomes higher than threshold value temperature or not, and it decreases fuel injection quantity in the case when the cooling water temperature is higher than the threshold value temperature. The CPU renews the threshold value temperature by reading the threshold value temperature corresponding to the lowest temperature from an ROM of the ECU 60 when the cooling water temperature is changed from dropping over to rising and becomes the minimum temperature. The threshold value temperature stored in the ROM is set at the lower temperature, the lower the minimum temperature is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating state detecting device for detecting the heating state of an engine in order to avoid overheating.

[0002]

2. Description of the Related Art Heretofore, various techniques aimed at preventing overheating in a diesel engine have been proposed. For example, in a fuel injection control device for a diesel engine disclosed in Japanese Patent Laid-Open No. 59-39942, a temperature sensor for detecting the temperature of engine cooling water is attached to a cylinder block and based on a detection signal from the sensor. The amount of fuel injection is reduced.

That is, in the control device, when the engine cooling water temperature exceeds a preset threshold temperature, the amount of fuel injection is reduced to reduce the engine load, thereby suppressing the occurrence of overheat. There is.

Conventionally, the threshold temperature is set as follows. 10, L1 in FIG. 10 indicates the cylinder head side cooling water temperature (hereinafter referred to as “head side temperature”) THWH and the cylinder block side cooling water temperature (hereinafter referred to as “block side temperature”) when the engine load is increased. ) It shows the temperature change with THWB.

The cylinder head normally receives a larger amount of heat because it is located closer to the combustion chamber of the engine, which is a heat source, and has a smaller heat capacity because its volume is smaller than that of the cylinder block. Therefore, as shown in the figure, the head-side temperature THWH is always higher than the block-side temperature THWB, and it rapidly follows the change in the amount of heat generated from the combustion chamber. It is larger than that at the temperature THWB.

Conventionally, the block side temperature THWB when the head side temperature THWH, which becomes higher, becomes the allowable upper limit temperature (hereinafter referred to as "allowable upper limit temperature") THWHMAX is set as the threshold temperature THWBTH, Block side temperature TH detected by the sensor
When WB reaches this threshold temperature THWBTH, it is determined that the head side temperature THWH has reached the upper limit temperature THWHMAX and the fuel injection amount is reduced.

[0007]

However, the above-mentioned prior art has the following problems. In FIG. 10, L
Reference numeral 2 denotes a head side temperature THWH and a block side temperature THWB when the engine load is rapidly increased from a state where the engine is at a low temperature (for example, immediately after the engine is started).
Shows the change.

In such a case, the temperature of the cylinder head rapidly rises with an increase in the amount of heat generated from the combustion chamber, but the temperature of the cylinder block does not rise in accordance with the increase in the amount of heat, resulting in the cylinder head. Was sometimes locally high in temperature.

That is, as shown in FIG. 10, the block side temperature THWB has not reached the threshold temperature THWBTH even though the head side temperature THWH has already exceeded the allowable upper limit temperature THWHMAX (in the same figure). The timing t2) may occur. As a result, in the above-mentioned conventional technique, the overheat avoidance measure such as the reduction of the fuel injection amount is delayed, and there is a possibility that the engine may overheat.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine capable of appropriately detecting the heating state of the engine in order to reliably prevent the occurrence of overheat. The present invention is to provide a heating state detecting device.

[0011]

In order to achieve the above object, the invention according to claim 1 is, in an engine heating condition detecting device, a temperature detecting device for detecting a temperature on a cylinder block side of the engine, and Cylinder block side temperature detected from the temperature detecting means and the threshold temperature are compared, and when the cylinder block side temperature is equal to or higher than the threshold temperature, the determining means determines that the engine is in a heating state leading to overheating. The gist of the present invention is to include threshold temperature changing means for changing the threshold temperature based on the cylinder block side temperature detected by the temperature detecting means.

The "cylinder block side temperature" includes not only the temperature of the cylinder block but also the temperature of the coolant for cooling the block. According to a second aspect of the present invention, in the engine heating state detecting device according to the first aspect, the threshold temperature changing means changes the threshold temperature at a predetermined timing so that the threshold temperature becomes lower as the cylinder block side temperature becomes lower. It is what makes it a summary.

According to a third aspect of the present invention, in the engine heating state detecting device according to the first aspect, the threshold temperature changing means, when the temperature on the cylinder block side becomes a minimum temperature at which the temperature is switched from falling to rising, The gist is that the threshold temperature is changed based on the minimum temperature.

(Operation) According to the invention described in claim 1, the determining means compares the cylinder block side temperature detected by the temperature detecting means with a threshold temperature, and the cylinder block side temperature is equal to or higher than the threshold temperature. If it becomes, it is determined that the engine is in a heating state leading to overheating. The threshold temperature used in this determination is changed by the threshold changing means based on the cylinder block side temperature.

As described above, according to the present invention, the threshold temperature which is conventionally fixed at a constant value is changed based on the cylinder block side temperature. Therefore, the threshold temperature for determining whether or not the engine is in a heating state leading to overheating reflects the temperature state of the cylinder block side temperature, and therefore the determining unit appropriately detects the engine heating state. It

According to the invention described in claim 2, in addition to the operation of the invention described in claim 1, the temperature on the cylinder block side is low, and the temperature on the cylinder head side (the temperature of the cylinder head) is increased by the rapid increase in the engine load thereafter. Alternatively, when it is assumed that the temperature difference between the temperature of the coolant for cooling the head and the temperature on the cylinder block side is large, the threshold temperature is changed to a lower temperature. Then, the determination unit determines whether or not the engine is in a heating state leading to overheating based on the threshold temperature changed to a low temperature until the next change timing.

As a result, it is possible to suppress the occurrence of the problem that the temperature on the cylinder head side exceeds the allowable upper limit temperature before the heating state is detected. Further, the threshold temperature is changed to a higher temperature as the cylinder block side temperature becomes higher. Therefore, in the case where the cylinder block side temperature slowly changes as the engine load increases, whether or not the engine is in a heating state leading to overheat is determined based on the threshold temperature sequentially changed to a high temperature. To be judged. As a result, unnecessary overheat processing operation is suppressed.

According to the invention described in claim 3, in addition to the operation of the invention described in claim 2, when the temperature on the cylinder block side reaches a minimum temperature at which the temperature on the cylinder block side is switched from falling to rising, The threshold temperature is changed based on the minimum temperature.

By making the threshold temperature change timing when the temperature on the cylinder block side becomes the minimum value, the threshold temperature is constantly changed when the temperature on the cylinder block side rises. Therefore, the threshold temperature is not changed to a higher temperature while the cylinder block side temperature is increasing. Since the determining means determines the temperature state of the engine based on the threshold temperature changed at the time of starting the rise of the cylinder block side temperature, the heating state leading to overheating can be detected more reliably.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. FIG. 1 shows an automobile diesel engine (hereinafter referred to as “engine”) 1 and a distribution type fuel injection pump (hereinafter referred to as “fuel injection pump”) 2 including an engine heating state detection device according to the present invention. It is a schematic block diagram.

The structure of the fuel injection pump 2 will be described below. The fuel injection pump 2 includes a drive shaft 6, and a drive pulley 4 is attached to the tip end side (left side in FIG. 1) of the shaft 6. The drive pulley 4 is
It is drivingly connected to the crankshaft 3 of the engine 1 via a belt or the like not shown.

A fuel feed pump 7 (developed by 90 ° in FIG. 1) consisting of a vane type pump is provided in the middle of the drive shaft 6. The disk-shaped pulsar 8 is
It is attached to the base end side (right side in FIG. 1) 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 includes the cam face 9 of the cam plate 9 in the roller ring 10.
It is attached so as to face α. The cam plate 9 is constantly urged and engaged with the cam roller 11 by the spring 12.

The fuel pressurizing plunger 13 is attached to the cam plate 9 so as to be rotatable integrally therewith, and the rotational force of the drive shaft 6 is transmitted to the cam plate 9 via a coupling, whereby the cam plate 9 is rotated. Plate 9
While the plunger 13 is rotating, the plunger 13 is reciprocally driven in the left-right direction in FIG. Plunger 13 is pump housing 1
It is fitted in a cylinder 15 formed in No. 4, and a high-pressure chamber 16 is formed between the tip end surface (the right end surface in FIG. 1) of the plunger 13 and the inner bottom surface of the cylinder 15.

The suction grooves 17 and the distribution ports 18 are formed on the outer periphery of the plunger 13 on the front end side in the same number as the number of cylinders of the engine 1. The distribution passage 19 and the suction port 20 correspond to the suction groove 17 and the distribution port 18,
It is formed on the pump housing 14.

When the fuel feed pump 7 is driven by the rotation of the drive shaft 6, fuel is supplied from a fuel tank (not shown) 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, in the compression stroke in which the plunger 13 moves to the right in the figure (forward movement) to pressurize the high-pressure chamber 16, fuel is pressure-fed from the distribution passage 19 to the fuel injection nozzle 5 of each cylinder. Fuel is injected from the nozzle 5 into the auxiliary combustion chamber 33.

The fuel overflow spill passage 23 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.

By controlling the energization time of the electromagnetic spill valve 24, the electromagnetic spill valve 24 is controlled to open / close.
The overflow rate 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 fuel in the high pressure chamber 16 is depressurized and the fuel injection from the fuel injection nozzle 5 is stopped. That is, even if the plunger 13 moves forward, the fuel pressure in the high-pressure chamber 16 does not rise while the electromagnetic spill valve 24 is open, and fuel injection from the fuel injection nozzle 5 is not performed. In addition, during the forward movement of the plunger 13, the electromagnetic spill valve 24
The fuel injection amount from the fuel injection nozzle 5 is controlled by adjusting the timing of closing and opening the valve. In the present embodiment, this fuel injection amount is one load element of the engine 1.

Next, the structure of the engine 1 will be described. As shown in FIG. 1, a cylinder 27 that constitutes each cylinder
Is formed in the cylinder block 28, and the cylinder 27
A piston 30 supported by the crankshaft 3 via a rod 29 is inserted therein. The cylinder head 31 is attached to the upper portion of the cylinder block 28.

The main combustion chamber 32 is formed so as to be surrounded by the cylinder 27, the piston 30 and the cylinder block 28. A sub combustion chamber 33 is formed inside the cylinder head 31, and the sub combustion chamber 33 is connected to the main combustion chamber 32. The combustion injection nozzle 5 is the auxiliary combustion chamber 3
The fuel is installed so as to face the inside of the fuel cell 3, and the fuel injected from the combustion injection nozzle 5 is injected and supplied to the auxiliary combustion chamber 33.

Inside the cylinder block 28, a block side cooling water passage 34a is formed in the outer peripheral portion of the cylinder 27. A head side cooling water passage 34b is formed inside the cylinder head 31 at a position corresponding to the upper portion of the main combustion chamber 32, and the water passage 34b communicates with the block side cooling water passage 34a. The block side cooling water passage 34a is connected to a water pump (not shown), and the head side cooling water passage 34b is connected to the water pump via a radiator and a thermostat (not shown). The head side cooling water passage 34b is connected to a heater (not shown), and the heater is further connected to the water pump. Each cooling water passage 34a,
A cooling system of the engine 1 is constituted by 34b, a water pump, a radiator, a thermostat, a heater and the like.

The engine cooling water discharged from the water pump sequentially flows through the block side cooling water passage 34a and the head side cooling water passage 34b. During operation of the engine, the cylinder block 28 and the cylinder head 31 are cooled by the cooling water flowing through the cooling water passages 34a and 34b. The cooling water flowing in the head side cooling water passage 34b is introduced into the radiator. Then, the cooling water is cooled by the heat exchange action of the radiator, and then discharged again from the water pump into the block side cooling water passage b via the thermostat. A part of the cooling water whose temperature has risen due to the heat of the cylinder head 28 is branched from the head side cooling water passage 34b and introduced into the heater to be used for heating the vehicle interior.

A turbocharger 37 is mounted on the engine 1. The turbocharger 37 includes a turbine 39 arranged in the middle of the exhaust pipe 36, a compressor 38 arranged in the middle of the intake pipe 35, and a shaft connecting the turbine 39 and the compressor 38. The exhaust pipe 36 is provided with a wastegate valve 40 for adjusting the boost 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.

In an air conditioning device (hereinafter referred to as "air conditioner") 52, which is an auxiliary machine, as another load element for the engine 1, its refrigerant compressor 53 is an electromagnetic clutch 54 and a belt 55 as a drive transmission system. Is connected to the crankshaft 3 of the engine 1 via. 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 engine 1 is provided with the following sensors 44 to 49 as sensors for detecting its operating condition. An intake air temperature sensor 44 for detecting the intake air temperature is attached to the intake pipe 35 near the air cleaner 43. A rotation speed sensor 45 is attached to the upper portion of the roller ring 10 so as to face the outer peripheral surface of the pulsar 8. The rotation speed sensor 45 is composed of an electromagnetic pickup coil, detects the passage of the projections formed on the outer peripheral surface of the pulsar 8 when they cross, and outputs a timing signal (engine rotation pulse) corresponding to the engine rotation speed NE. To do.

The intake pipe 35 is provided with an accelerator opening sensor 46 for detecting the accelerator opening ACCP from the opening / closing position of the throttle valve 41. The intake pipe 35 is provided with an intake pressure sensor 47 that detects the intake pressure after being supercharged by the turbocharger 37.

Further, the cylinder block 28 is provided with a water temperature sensor 48 as a temperature detecting means, and the water temperature of the cooling water in the block side cooling water passage 34a (hereinafter referred to as "block side temperature") is provided by the sensor 48. THW
B is detected. In addition, a transmission (not shown) includes a magnet 50 that rotates in association with the rotation of the gear.
There is provided a vehicle speed sensor 49 for detecting the traveling speed (vehicle speed) by turning on / off the reed switch 51.

The rotation speed sensor 45 and the accelerator opening sensor 46 constitute an operating condition detecting means. Next, the electrical configuration of the present embodiment will be described with reference to the block diagram shown in FIG.

As shown in FIG. 2, an electronic control unit (EC
U) 60 is a central processing unit (CPU) 61, a read-only memory (ROM) 62 that stores a predetermined control program, maps, etc., and a readable / writable memory (RAM) 63 that temporarily stores calculation results and the like. It is composed of a theoretical operation circuit including the above.

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.

The CPU 61 reads the signals from the sensors 44 to 49 input via the external input circuit 65 as input values, and based on these input values, performs heating state detection processing, fuel injection amount control, ignition timing control, and the like. To do. The CPU 61
Constitutes the determining means and the threshold temperature changing means in the present invention as described later. Further, the CPU 61 which is the judging means and the threshold temperature changing means, and the water temperature sensor 48 which is the temperature detecting means constitute the engine heating state detecting device of the present invention.

Next, the "heating state detection routine" and the "fuel injection amount calculation routine" in the present embodiment will be described. The flowcharts shown in FIG. 3 and FIG. 4 show a “heating state detection routine” of the respective processes executed by the CPU 61, and the routine is executed by a regular interrupt every predetermined time.

The flowchart of FIG. 5 shows a "fuel injection amount calculation routine", which calculates the fuel injection amount QFIN based on the engine heating state determination result in the heating state detection routine. It is a thing.

The heating state detection routine will be described below. Each step 101 to 120 in this heating state detection routine is executed by the CPU 61.

When the operation of the engine is started, an initial value determination routine is executed by the CPU 1, and a water temperature lowering flag XTHWB and a counter C, which will be described later, are "0".
In addition, the minimum temperature THWBMIN (n-1) and the block side temperature THWB (n-1) are the initial values THWBMIN.
0 and THWB0 (for example, both are “70 ° C.”). In the same routine, the minimum temperature T
The threshold temperature THWBTH corresponding to HWBMIN0 is RO
It is read from M62 and stored in the RAM 63.

Here, the water temperature lowering flag XTHWB
Indicates whether or not the change in the block side temperature THWB (n) is in the process of falling.
When HWB (n) is changing downward, the flag XTH
If WH is set to "1" and there is no downward change,
It is set to "0".

Further, the minimum temperature THWBMIN indicates the temperature when the change of the block side temperature THWB is changed from the decrease to the increase, and the minimum temperature THWBMIN (n-
1) indicates the value set in the previous process, and the minimum temperature THWBMIN (n) indicates the value set in the current process.

The counter C has a minimum temperature THWBMIN.
After (n) is set, the minimum temperature THWBMIN (n)
Indicates the time until is reset. Upon shifting to the heating state detection routine, the CPU 61 executes step 10
At 1, the block side temperature THWB (n) detected by the water temperature sensor 48 is read.

Subsequently, the CPU 61 proceeds to step 102, and the block side temperature THWB (n) read in step 101 is the judgment temperature THWBJ (for example, "7").
0 ° C. ”) or higher. And CPU
In 61, the block side temperature THWB (n) is the judgment temperature TH.
If it is less than WBJ (step 102: [NO]), the process proceeds to step 119, and the minimum temperature THWBMIN
(N) is set equal to the determination temperature THWBJ. On the other hand, the block side temperature THWB (n) is equal to the determination temperature TH.
When it is WBJ or more (step 102 is "YES")
Then, the CPU 61 proceeds to step 103.

The CPU 61, in step 103,
The block-side temperature THWB (n) read this time and the block-side temperature THWB (n) read in the previous processing
-1) is compared to determine whether the current block-side temperature THWB is equal to or higher than the previous block-side temperature THWB. Then, the CPU 61 determines that the current block side temperature TH is
WB (n) is the previous block side temperature THWB (n-1)
If the block-side temperature THWB (n) is smaller than the above value (step 103 is “NO”), the process proceeds to step 120. In the present embodiment, the CPU 61 that executes the process of step 103 is
It constitutes a water temperature determination means.

On the other hand, the current block side temperature TH
WB (n) is the previous block side temperature THWB (n-1)
If the block side temperature THWB (n) is being increased or is not changing (step 10)
If 3 is "YES"), the process proceeds to step 104.

Subsequently, the CPU that has moved to step 104.
Reference numeral 61 determines whether or not the water temperature lowering flag XTHWB is "1", and when the water temperature lowering flag XTHWB is set to "1" (when step 104 is "YES"), the CPU 61 determines the block side. When it is determined that the change in the temperature THWB (n) has changed from the decrease to the increase, the processes of step 105 and step 106 are sequentially performed.

The CPU 61 having moved to step 105
The water temperature lowering flag XTHWB is set to "0". Furthermore,
The CPU 61 proceeds to step 106 and sets the block side temperature THWB (n) read this time to the minimum temperature THWB.
After setting as MIN (n), the process proceeds to step 107.

The CPU 61 having moved to step 107
It is determined whether or not the counter C exceeds the determination value CJ. The determination value CJ is set so that the time from when the counter C reaches “0” to the determination value CJ corresponds to 120 seconds. Then, when the counter C is less than the determination value CJ (step 107 is “NO”), the CPU 61 proceeds to step 108.

The CPU 61 having moved to step 108
The annealing process is performed on the minimum temperature degree THWBMIN (n). That is, the CPU 61 calculates the arithmetic average value of the minimum temperature THWBMIN (n) set this time in step 106 and the minimum cooling temperature THWMIN (n) set before the previous process: (THWMIN (n) + THWMIN
(N-1)) / 2 as the new minimum cooling temperature THWMIN
Set as (n). In the present embodiment, the CPU 61 that performs the process of step 108 constitutes a correction unit.

After executing the processing in step 119 or step 108, or when the counter C exceeds the judgment value CJ in step 107 (step 1
07 is “YES”), and the CPU 61 shifts to step 109. Then, the CPU 61 causes the steps 106 and 1 to be executed.
08,119 new minimum cooling temperature THWMIN
Since (n) has been set, the counter C is reset to "0" and then the process proceeds to step 110.

The CPU 61 having moved to step 110
The threshold temperature THWBTH for determining whether or not the engine is in a heating state leading to overheating is changed. Here, the "heating state leading to overheating" refers to a state in which it is necessary to limit the load because there is a risk of overheating when the engine load is maintained as it is. In the mode, the cooling water in the head side cooling water passage 34b, which has the highest temperature in the engine cooling system, has reached the allowable upper limit temperature (for example, “105 ° C.”).

Further, the ROM 62 has a minimum temperature THW.
The relationship between BMIN (n) and the threshold temperature THWBTH is stored as a map as shown in FIG. CPU6
1 is the minimum temperature THWBMIN based on this map
The value corresponding to (n) is read and set as a new threshold temperature THWBTH, and the process proceeds to step 111 to set the new threshold temperature THWBTH to the RAM 6
3 is stored. In the present embodiment, step 1
10 and CP that executes the threshold value changing process of step 111
U61 constitutes a threshold temperature changing means.

After performing the threshold temperature changing processing in steps 110 and 111, the CPU 61 proceeds to step 112. Further, the CPU 61 sets the water temperature lowering flag XTHWB to "1" in step 120, or, in step 104, the water temperature lowering flag XTHWB.
Is set to “0” (step 104 returns “N
O ”) does not perform the threshold temperature changing process, and proceeds to step 112.

The CPU 61, which has proceeded to step 112,
After reading the threshold temperature THWBTH from the RAM 63, the process proceeds to step 113. In step 113, the CPU 61 performs a heating state determination process for determining whether or not the engine is in a heating state leading to overheating.
That is, the CPU 61 compares the threshold temperature THWBTH read in step 112 with the block side temperature THWB (n) read in step 101, and the block side temperature THWB (n) is equal to or higher than the threshold temperature THWBTH. In this case, it is determined that the engine 1 is in a heating state leading to overheating, and the routine proceeds to step 114, where the fuel injection amount reduction flag XDEF is set to "1".

On the other hand, the block side temperature THWB
If (n) is less than the threshold temperature THWBTH, the CPU
61 shifts to step 115 and sets the fuel injection amount reduction flag XDEF to "0". In the present embodiment, the heating state determination process in step 113 is performed C
The PU 61 constitutes a judgment means.

The CPU 61 sets the fuel injection amount reduction flag XDEF to a predetermined value in steps 114 and 115, and then prepares for the subsequent calculation processing in steps 116 and 117.
Are sequentially performed.

At step 116, the current minimum temperature TH
WBMIN (n) is set to the last minimum temperature THWBMIN (n
-1) is stored in the RAM 63. Also, step 11
In 7, the current block side temperature THWB (n) is stored in the RAM 63 as the previous block side temperature THWB (n-1).

Then, the CPU 61 proceeds from step 117 to step 118, adds "1" to the counter C, and then ends this routine. Next, the “fuel injection amount calculation routine” of FIG. 5 will be described. In calculating the fuel injection amount QFIN in the routine, the fuel injection amount reduction flag X set in the heating state detection routine is set.
DEF is used.

When shifting to the fuel injection amount calculation routine, CP
In step 201, U61 detects each of the sensors 44 to 44.
Based on the detection signals of 47 and 49, the engine speed NE,
The throttle opening ACCP, the vehicle speed, the intake air temperature, and the intake air pressure are read, respectively, and step 202
Move to

In step 202, the CPU 61 calculates the basic fuel injection amount QBASE based on the engine speed NE and the accelerator opening ACCP. This basic fuel injection amount QBASE is determined by the engine speed NE and the accelerator opening ACC.
It is obtained by referring to a map (not shown) stored in the ROM 62 with P as a parameter.

Next, the CPU 61 proceeds to step 203 to calculate the maximum fuel injection amount QFULL. The maximum fuel injection amount QFULL means the upper limit value of the fuel injection amount with respect to the intake air of the engine 1, and is calculated based on the engine speed NE, the intake air pressure, the intake air temperature, etc., which have been read previously. Then, the CPU 61 shifts to step 204.

In step 204, the CPU 61 determines whether or not the fuel injection amount reduction flag XDEF set in the above-mentioned heating state detection routine is "1". When the fuel injection amount reduction flag XDEF is not "1" (step 204 is "NO"), the CPU 61 proceeds to step 205.

In step 205, the CPU 61 selects the smaller one of the previously calculated basic fuel injection amount QBASE and maximum fuel injection amount QFULL, and sets this as the final fuel injection amount QFIN. Therefore, the CPU 61 does not set the fuel injection amount reduction in step 205.
On the other hand, when the fuel injection amount reduction flag F is "1" in step 204 (step 204 is "YE").
S ”), the CPU 61 sets the reduction amount of the fuel injection amount. That is, the CPU 61 proceeds to step 206 and calculates the fuel injection amount correction amount ΔQ from the throttle opening ACCP, the vehicle speed and the like. Further, the CPU 61 shifts to step 207,
The smaller one of the basic fuel injection amount QBASE and the maximum fuel injection amount QFULL is selected and the final fuel injection amount QFIN is set by subtracting the fuel injection amount correction amount ΔQ from the selected injection amount.

The CPU 61 adjusts the electromagnetic spill valve 24 to match the fuel injection amount with the final fuel injection amount QFILL calculated in steps 205 and 207. Hereinafter, the operation of this embodiment will be described.

As described above, in the heating state detection routine according to the present embodiment, in order to change the threshold temperature THWBTH, the temperature at which the temperature change in the block side temperature THWB (n) is switched from falling to rising, that is, the minimum temperature. The temperature THWBMIN (n) is detected, and the threshold temperature THWBTH corresponding to this is read from the ROM 62. Further, the threshold temperature THWBTH is not a constant value, and as shown in FIG. 6, the minimum temperature THWBMIN (n)
The lower is, the lower the temperature is set.

As described above, the minimum temperature THWBMIN (n) is used as a parameter for determining the threshold temperature THWBTH.
And the threshold temperature THWBTH is set to the minimum temperature THWB
The reason why the lower the MIN (n), the lower the temperature will be described below.

The engine temperature of the engine 1 is the threshold temperature THWBTH.
This is for determining whether or not the load has reached a heating state that requires overheating. Therefore,
In order to reliably detect the heating state, the threshold temperature THWBTH may be set in consideration of the case where the temperature of the engine 1 is at least rising. Since the temperature of the engine 1 does not decrease while the temperature is decreasing, it is sufficient to consider only the case where the temperature increases.

Further, the cooling water temperature in the block side cooling water passage 34a, that is, the block side temperature THWB and the cooling water temperature in the head side cooling water passage 34b (hereinafter, referred to as "head side temperature THW").
H)), both temperatures THWB, THW
H has the following characteristics [1] to [5].

[1] The cylinder head 31 is located closer to the main and auxiliary combustion chambers 32 and 33, which are heat sources, as compared with the cylinder block 28. Therefore, as shown by L3 to L5 in FIG. 7, the head side temperature THWH is equal to the block side temperature TH.
It is always hotter than WB.

In FIG. 7, L4 and L5 respectively show changes in the head side temperature THWH and the block side temperature THWB when the engine load is increased from the state where the engine 1 is at a low temperature. Further, L4 indicates a temperature change when the engine load is large, and L5 indicates a temperature change when the engine load is smaller than that in the case of L4. Further, in the same figure, L3 shows changes in the head side temperature THWH and the block side temperature THWB when the load is increased from the state where the engine 1 is at a high temperature.

[2] Since the cylinder block 31 has a smaller volume than the cylinder block 28, the heat capacity is small. Therefore, as shown by L3 to L5 in FIG. 7, the head side temperature THWH has a higher temperature rising speed than the block side temperature THWB.

[3] As indicated by L3 and L4 in FIG. 7, the temperature difference ΔTHW1, ΔTHW2 between the head side temperature THWH and the block side temperature THWB when the head side temperature THWH reaches the allowable upper limit temperature THWHMAX. Becomes larger as the minimum temperature THWBMIN at the time when the block side temperature THWB is switched from lowering to rising is lower. This is because there is a difference in the temperature rising rate as shown in the above characteristic [2] between the head side temperature THWH and the block side temperature THWB.

[4] There is a difference in heat capacity between the cylinder head 31 and the cylinder block 28. Therefore, L in FIG.
4 and L5, the temperature difference ΔTHW2, ΔTH
W3 is the head side temperature THW as the engine load increases.
It increases as the temperature rising rate of H and the block side temperature THWB increases.

[5] When the head-side temperature THWH and the block-side temperature THWB decrease, both temperatures THWH, THWH
The temperature decrease rate of B is substantially equal as shown in FIG. The cylinder head 31 has the property of lowering its temperature earlier than the cylinder block 28 due to its small heat capacity, while the cylinder head 31 is located close to the main and auxiliary combustion chambers 32, 33, so that the cylinder block 28 Both rooms compared to 3
Receive more heat from 2,33. Therefore, the temperature lowering speeds at the head side temperature THWH and the block side temperature THWB become substantially equal.

In the present embodiment, the characteristics of the head side temperature THWH and the block side temperature THWB described above [1].
~ In consideration of [5], the threshold temperature T
HWBTH is decided.

In order to reliably detect the heating state leading to overheat of the engine 1, as can be seen from the characteristic [1], the block side temperature when the head side temperature THWH which becomes higher becomes the allowable upper limit temperature THWHMAX. TH
It is necessary to set WB as the threshold temperature THWBTH. Furthermore, as can be seen from the characteristics [2] to [4],
When determining the threshold temperature THWBTH, the minimum temperature THWBMI at which the block side temperature THWB starts to rise.
N and the temperature rise rate of the block side temperature THWB must be taken into consideration.

From the above, in order to reliably detect the heating state of the engine 1 when the temperature of the engine 1 rises, the block side temperature THWB is set to the minimum temperature THWBMIN.
, The threshold temperature THWBTH is calculated as follows.
Is set, and the subsequent temperature state of the engine 1 may be determined based on the threshold temperature THWBTH.

That is, it is assumed that the engine load becomes the maximum load after the block side temperature THWB reaches the minimum temperature THWBMIN. In that case, the head side temperature THWH
The block temperature THWB when the temperature reaches the allowable upper limit temperature THWHMAX is set as the threshold temperature THWBTH corresponding to the minimum temperature THWBMIN.

Here, the case where the engine load becomes the maximum load is assumed, in which case the temperature rising speeds of the head side temperature THWH and the block side temperature THWB are the largest, and as described in the characteristic [3]. Both temperature TH
This is because the temperature difference between WH and THWB becomes maximum.

As described above, by setting the threshold temperature THWB, the temperature difference between the head side temperature THWH and the block side temperature THWB is larger than expected, and the head side temperature THWH exceeds the allowable upper limit temperature THWHMAX. Regardless, the block side temperature THWB is the threshold temperature THW
It is possible to avoid the situation where BTH is not reached.

FIG. 9 shows experimentally obtained temperature changes of the block side temperature THWB and the head side temperature THWH when the engine load is maximized after the block side temperature THWB reaches the minimum temperature THWBMIN. In this embodiment, the block side temperature THWB is shown in FIG.
Threshold temperature THWB corresponding to the minimum temperature THWBMIN of
TH is required.

For example, taking L6 in the figure as an example, after the block side temperature THWB reaches the minimum temperature THWBMIN, the block side temperature TH is increased as the engine load increases.
The WB and the head side temperature THWH increase. Then, the head side temperature THWH reaches the upper limit allowable temperature THWHMAX, but the block side temperature THWB at that time becomes the threshold temperature THWBTH. In the figure, the minimum temperature THWBMI
Each minimum temperature THWBMI when N is changed
The threshold temperatures THWBTH corresponding to N are shown.

FIG. 6 described above shows the relationship between the minimum temperature THWBMIN obtained as described above and the threshold temperature THWBTH corresponding to the temperature THWBMIN. As shown in the figure, the threshold temperature THWBTH is lower as the minimum temperature THWBMIN is lower. This is because there is a difference in temperature rising rate between the head side temperature THWH and the block side temperature THWB, as described in the above characteristic [2].

As described above, in this embodiment, the minimum temperature T is used as a parameter for determining the threshold temperature THWBTH.
HWBMIN is used, and the lower the minimum temperature THWBMIN, the lower the threshold temperature THWBTH.

Next, with reference to the timing chart shown in FIG. 8, the change in the threshold temperature THWBTH when the block side temperature THWB changes as shown in the figure will be described.

First, at timing t0, the operation of the engine 1 is started, the water temperature lowering flag XDEF and the counter C are both set to "0", and the minimum temperature THWBMIN (n
-1) and the block side temperature THWB (n-1) are set to initial values THWBMIN0 and THWB0. In addition, the threshold temperature THWBTH corresponding to the minimum temperature THWBMIN0
Is read from the ROM 62 and stored in the RAM 63. Next, at the timing t1, the heating state detection routine is started. Between the timings t1 and t3, the threshold temperature THWBTH is not changed, and the step 1
13, the initial value THW of the minimum temperature THWBMIN
The heating state of the engine 1 is determined based on the threshold temperature THWBTH0 corresponding to BMIN0. Further, during the period from timing t1 to t3, the block side temperature THWB does not reach the threshold temperature THWBTH0, so the fuel injection amount reduction flag XDEF is held at "0".

At the timing t2, the block side temperature TH
WB switches from rising to falling, and the above step 120
In, the water temperature lowering flag XTHWB is set from "0" to "1". Further, the counter C is incremented in step 118 until the threshold temperature THWBTH is changed from the timing t1 to the timing t3.

Next, at the timing t3, when the temperature change of the block side temperature THWB switches from decrease to increase, in step 105, the water temperature decrease flag XTHWB.
Is set to "0", and the current block side temperature THWB is set to the minimum temperature THWBM in step 106.
It is set as IN3. Here, since the counter C exceeds the judgment value CJ after a predetermined time elapses from the timing t1 to the timing t3 when the process of changing the threshold temperature THWBTH, the smoothing process in step 108 is not executed. Further, in step 109, the counter C is reset to "0".

Then, in steps 110 and 111, the threshold temperature THWBTH is changed. That is, in step 110, the current minimum temperature THWBMIN3
The threshold temperature THWBTH3 corresponding to is read from the ROM 62, and the threshold temperature THWBTH3 is newly stored in the RAM 63 in step 111. Since the current minimum temperature THWBMIN3 is higher than the previous minimum temperature THWBMIN0, the threshold temperature THWBTH is changed to the threshold temperature THWBTH3 which is higher than the previous value THWBTH0. After the timing t3, the heating state of the engine 1 in step 113 is determined based on the threshold temperature THWBTH3. Further, at step 118, the counter C is sequentially incremented.

At the timing t4, the block side temperature THW
When the temperature change of B is switched from rising to falling, the water temperature lowering flag XTH is determined in step 120 as at timing t2.
WB is set to "1".

Next, at the timing t5, the change of the block side temperature THWB switches from the decrease to the increase again. Then, as in the case of timing t3, step 105
In, the water temperature lowering flag XTHWB is set to “0” and the current block side temperature THWB is set as the minimum temperature THWMIN5 in step 106.

Here, since the predetermined time has not elapsed since the last time (timing t3) the changing process of the threshold temperature THWBTH was performed and the counter C has not reached the determination value CJ, the minimum temperature THWBMIN in step 108 is reached.
The moderating process of 3 is executed. Therefore, the minimum temperature THWBMIN3 set last time and the minimum temperature T set this time are set.
Arithmetic mean value with HWBMIN5: (THWBMIN3 +
THWBMIN5) / 2 is the new minimum temperature THWBMI
It is set as N5. Further, in step 109, the counter C is reset to "0".

Then, step 110 and step 11
In 1, the process of changing the threshold temperature THWBTH is performed again. That is, in step 110, the current minimum temperature T
The threshold temperature THWBTH5 corresponding to HWBMIN5 is R
The threshold temperature THWBTH5 read from the OM 62 and read in step 111 is stored in the RAM 63.

After timing t5, the heating state of the engine 1 in step 113 is determined based on the newly set threshold temperature THWBTH5. In the present embodiment, in step 108, the minimum temperature THW is reached.
Since the BMIN annealing process is performed, the temperature THWB on the block side rises while pulsating, and even if a slight temperature decrease is included in the course of the increase, the threshold temperature TH
WBTH can be changed to an appropriate value.

More specifically, the block side temperature T
Since the time when the HWB falls (timing t4 to t5) is short and the previous threshold value changing process (timing t3) is executed, the minimum temperature THWBMIN is set (timing t3).
When the time until 5) is performed is short, the temperature state of the block side temperature THWB and the head side temperature THWH is similar to the case where the block side temperature THWB rises as shown by the chain double-dashed line L7 in FIG. It is considered to be in a state.
Therefore, at the timing t5, not only the minimum temperature THWBMIN5 set this time but also the previous minimum temperature THWB
It is necessary to change the threshold temperature THWBTH in consideration of MIN3 as well.

Therefore, in the present embodiment, the arithmetic mean value of the minimum temperature THWBMIN5 set this time and the minimum temperature THWBMIN3 set last time is set as a new minimum temperature THWBMIN5, and the minimum temperature THWMIN is set to a lower temperature.
BMIN5 is set. Therefore, step 1
In 13, the threshold temperature THWBTH5 corresponding to this minimum temperature THWBMIN5, that is, the threshold temperature TH set to a lower temperature as compared with the case where the arithmetic mean processing is not performed.
Since the heating state of the engine 1 that causes overheating is determined based on the WBTH5, the determination becomes reliable.

At the timing t6, the block side temperature T
HWB changed threshold temperature THWB at timing t5
When it becomes equal to or higher than TH5, it is determined in step 113 that the engine 1 is in a heating state leading to overheating, and in step 114, the fuel injection amount reduction flag XD
EF is set to "1". As a result, the fuel injection amount is set to be reduced in the fuel injection amount calculation routine described above,
Reduction of the fuel injection amount is executed.

The present embodiment described above has the following features. (A) According to the present embodiment, the threshold temperature THWBTH is changed based on the block side temperature THWB, so that the temperature state of the engine is detected based on the threshold temperature fixed to a constant value. Compared with, it is possible to perform more appropriate detection according to the temperature change of the block side temperature THWB.

(B) In the present embodiment, the threshold temperature THWBTH is changed to a lower temperature as the block side temperature THWB is lower. Therefore, when the block side temperature THWB is low, the threshold temperature THWBTH
Is set to a lower temperature, and thereafter, even if the engine load suddenly increases and the temperature difference between the block temperature THWB and the head side temperature THWH becomes large, the engine temperature is changed based on the threshold temperature changed to a low temperature. The heating state leading to the overheating of 1 is detected. As a result, it is possible to suppress the occurrence of a problem in which the head side temperature THWH exceeds the allowable upper limit temperature THWHMAX before the heating state is detected, and the overheat avoidance procedure is delayed.

Also, the threshold temperature THWBTH is changed to a higher temperature as the block side temperature THWB becomes higher. Therefore, when the block side temperature THWB changes slowly as the engine load increases,
It is determined whether the engine 1 is in a heating state leading to overheat based on the threshold temperature that is sequentially changed to a high temperature.

In order to more reliably detect that the engine 1 has reached the overheated heating state, for example, the threshold temperature is fixed to a lower temperature as shown by the one-dot chain line in FIG. It is possible to determine the heating state based on the above. However, in this case, the fuel injection amount is often reduced before the head side temperature THWH reaches the allowable upper limit temperature THWHMAX, and the original output of the engine 1 cannot be obtained.

In this embodiment, the block side temperature THW is
Since the threshold temperature THWBTH is changed to a higher temperature as B becomes higher, it is possible to suppress an unnecessary reduction operation of the fuel injection amount and secure the power performance of the engine 1. it can.

(C) In this embodiment, the threshold temperature THWBTH is changed when the block side temperature THWB reaches the minimum temperature THWBMIN. Therefore,
When the block side temperature THWB rises, the threshold temperature THWBTH is constantly changed. That is, the threshold temperature THW is increased while the block side temperature THWB is increasing.
BTH is not changed to a higher temperature,
The heating state of the engine 1 is determined based on the low threshold temperature THWBTH changed at the time of starting the increase. Therefore, the heating state leading to overheating can be detected more reliably, and the fuel injection amount can be appropriately reduced based on the detection result.

(D) In this embodiment, as described above, the engine load becomes the maximum load and the block side temperature T
Assuming that the temperature of HWB changes, the minimum temperature THWB
The threshold temperature THWBTH corresponding to MIN is determined. That is, the threshold temperature THWBTH is set lower in consideration of the case where the temperature difference between the block side temperature THWB and the head side temperature THWH is the largest. Therefore, even when the temperature rising speed of the engine 1 is large and the temperature difference between the block side temperature THWB and the head side temperature THWH is large, the head side temperature THWH is equal to the allowable upper limit temperature T.
When it reaches HWHMAX, it can be reliably detected that it is in a heating state leading to overheating.

(E) In this embodiment, the threshold temperature THW
If the time interval for executing the BTH changing process, that is, the time interval at which the block side temperature THWB reaches the minimum temperature THWBMIN is shorter than the predetermined time, the minimum temperature TH
WBMIN is annealed to obtain a minimum temperature THW
By setting BMIN to a lower temperature, the threshold temperature THWBTH is changed to a lower temperature. Therefore, even when the temperature rises while pulsating, including a slight temperature decrease change (timing t4 to t5) in time like the change of the block side temperature THWB at the timing t3 to t6 in FIG. It is possible to detect a heating state leading to overheating of the engine 1.

(F) Since the engine 1 according to the present embodiment is equipped with the turbocharger 37, the space of the cooling system in the engine room is restricted and the cooling performance thereof is deteriorated. Therefore, it is effective from the viewpoint of surely preventing overheating that the heating state leading to overheating in such an engine 1 can be properly detected.

Although the embodiment in which the present invention is embodied has been described above, this embodiment may be embodied as follows. (1) In the above embodiment, the diesel engine 1 is provided with the heating state detecting device according to the present invention, but the gasoline engine may be provided with the heating state detecting device.

(2) In the above embodiment, the fuel injection amount is reduced when a heating state leading to overheat is detected. However, for example, a warning lamp or a warning buzzer is used to notify the driver of the heating state. May be notified, and a measure for limiting the engine load (decrease in accelerator opening, etc.) may be prompted. Further, another engine load, for example, auxiliary equipment such as an air conditioning device may be stopped.

(3) In the above embodiment, when the time interval at which the block side temperature THWB becomes the minimum temperature THWBMIN is shorter than the predetermined time, the current minimum temperature THWBMIN.
For (n), the annealing process, that is, the previous minimum temperature TH
WBMIN (n-1) and current minimum temperature THWBMIN
The arithmetic mean value of (n) and the new minimum temperature THWBMIN
Although the processing set as (n) is performed, for example, a new minimum temperature THWBMIN (n) is set as follows.
May be set.

(3-1) TWBMIN (n) = [TH
WBMIN (n) + THWBMIN (n-1) + THW
BMIN (n-2)] / 3 Here, THWBMIN (n-2) is the minimum temperature of the previous two times.

(3-2) THWBMIN (n) = [T
HWBMIN (n) + 2 * THWMIN (n-1)] /
3 (3-3) THWBMIN (n) = THWBMIN
(N-1) (4) In the above embodiment, the determination of the heating state is performed by determining the threshold temperature THWBTH and the limit temperature (> threshold temperature THWBT).
H) in two stages, the fuel injection amount may be reduced when the block side temperature THWB becomes equal to or higher than the threshold temperature THWBTH, and the fuel injection may be stopped when the block temperature THWB becomes equal to or higher than the limit temperature. .

(5) In the above embodiment, the cooling water temperature in the block side cooling water passage 34b, that is, the block side temperature T.
Although the heating state is detected by comparing the HWB with the threshold temperature THWBTH, the temperature of the cylinder block 28 itself is measured, and the threshold temperature THWBT is measured based on the temperature.
The heating state of the engine 1 may be determined by changing the value of H and comparing the temperature of the cylinder block 28 with the threshold temperature THWBTH. In the case of an oil-cooled engine, the cooling oil temperature may be detected.

(6) The structure of the turbocharger 37 in the engine 1 may be deleted and embodied as a naturally aspirated engine. It may also be embodied in an engine with a supercharger.

(7) In the present embodiment, the time from when the counter C reaches "0" to the judgment value CJ is set to correspond to 120 sec., But this time depends on the specifications of the engine 1 and the like. It can be changed appropriately. Alternatively, the judgment value CJ is variable instead of a fixed value, and each of the sensors 44 to 49 is
You may make it change according to the driving | running state of the engine 1 detected by.

(8) In the present embodiment, as described above, the engine load becomes the maximum load and the block side temperature T
Assuming that HWB rises, the minimum temperature THWBMI
Since the threshold temperature THWBTH corresponding to N is determined, the heating state leading to overheating can be detected more reliably, but the engine load at this time does not necessarily have to be the maximum load.

The technical idea that can be understood from the above-described embodiment will be described below along with its effects. (A) In the engine heating state detecting device according to claim 3, when the block temperature reaches the minimum temperature, the threshold temperature changing means does not elapse a predetermined time from the time when the temperature reaches the minimum temperature last time. In this case, when changing the threshold temperature, the threshold temperature should be changed to a lower temperature.

(B) The temperature detecting means for detecting the temperature on the cylinder block side of the engine is compared with the temperature on the cylinder block side detected by the temperature detecting means and the threshold temperature, and the temperature on the cylinder block side is the threshold temperature. In the case of above, the determining means for determining that the engine is in a heating state leading to overheating, and the determining element for the load element of the engine when it is determined that the engine is in a heating state leading to overheating. An engine overheat prevention device having an engine load limiting means for applying a limit, having threshold temperature changing means for changing the threshold temperature based on a cylinder block side temperature detected by the temperature detecting means, Further, the threshold temperature changing means sets the threshold temperature to a lower temperature as the cylinder block side temperature is lower. It should be changed at the timing of.

According to the engine heating state detecting device described in (a) above, the temperature THWB on the cylinder block side includes a slight temperature decrease change with time, and even if the temperature rises while pulsating, the temperature is surely increased. It is possible to detect a heating state leading to overheating of the engine 1.

According to the engine overheat prevention device described in (b) above, the threshold temperature changing means changes the threshold temperature to a lower temperature as the cylinder block side temperature becomes lower. Therefore, even if the engine load suddenly increases and the temperature difference between the cylinder cylinder block temperature and the cylinder head side temperature increases, the determination means heats up to overheat the engine based on the threshold temperature changed to a low temperature. The state can be properly determined. And
Since the engine load limiting means limits the engine load element based on the determination result, it is possible to prevent the occurrence of overheat more reliably.

Further, since the threshold temperature is changed to a higher temperature as the temperature on the cylinder block side becomes higher, it is possible to suppress the unnecessary operation of reducing the fuel injection amount, and to reduce the power of the engine. Performance can be secured.

In the above embodiment, the engine load limiting means is composed of the CPU 61 which executes the process of step 207 of the fuel injection amount calculation routine.

[0128]

According to the invention described in claim 1, the threshold temperature, which has been conventionally fixed at a constant value, is changed based on the cylinder block side temperature, and the temperature state of the cylinder block side temperature is reflected. Since this is done, the heating state of the engine can be properly detected.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, when the temperature on the cylinder block side is low, the threshold temperature is set to a lower temperature.

Therefore, even if the engine load suddenly increases and the temperature difference between the cylinder head side temperature and the cylinder block side temperature increases, it is possible to reliably determine whether or not the engine is in a heating state leading to overheating. Therefore, it is possible to suppress the occurrence of a problem in which the temperature on the cylinder head side exceeds the allowable upper limit temperature before the heating state is detected and the overheat avoidance procedure is delayed.

In addition, the threshold temperature is changed to a higher temperature as the temperature on the cylinder block side becomes higher. Therefore, when the load of the engine increases from a high temperature, the threshold temperature changed to a high temperature. Based on the temperature, it is determined whether or not the engine is in a heating state leading to overheating. Therefore, it is possible to suppress an unnecessary overheat processing operation.

According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, since the threshold temperature is not changed while the temperature on the cylinder block side is rising, the temperature condition of the engine is not changed. Is determined on the basis of the lower threshold temperature changed at the start of the rise in the cylinder block side temperature. Therefore, the heating state leading to overheating can be detected more reliably.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a diesel engine or the like.

FIG. 2 is a block diagram showing a configuration of an ECU and the like.

FIG. 3 is a flowchart showing a heating state detection routine.

FIG. 4 is a flowchart showing a heating state detection routine.

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

FIG. 6 is a diagram showing a relationship between a minimum temperature and a threshold temperature.

FIG. 7 is a diagram showing temporal changes in head-side temperature and block-side temperature.

FIG. 8 is a timing chart for explaining the operation of the embodiment.

FIG. 9 is a diagram for explaining a method of determining a threshold temperature.

FIG. 10 is a diagram showing temporal changes in head-side temperature and block-side temperature.

[Explanation of symbols]

1 ... Diesel engine (engine), 48 ... Water temperature sensor (temperature detecting means), 61 ... CPU (determining means, threshold temperature changing means).

Claims (3)

[Claims] 1. A temperature detecting means for detecting a temperature of a cylinder block side of an engine, a cylinder block side temperature detected by the temperature detecting means and a threshold temperature are compared, and the cylinder block side temperature is equal to or higher than a threshold temperature. In the case of, the determining means for determining that the engine is in a heating state leading to overheating, and the threshold temperature changing means for changing the threshold temperature based on the cylinder block side temperature detected by the temperature detecting means, An engine heating state detection device characterized by being provided. 2. The engine according to claim 1, wherein the threshold temperature changing unit changes the threshold temperature at a predetermined timing such that the threshold temperature becomes lower as the cylinder block side temperature becomes lower. Heating state detection device. 3. The threshold temperature changing means executes the change of the threshold temperature based on the minimum temperature when the temperature on the cylinder block side becomes a minimum temperature at which the temperature is switched from falling to rising. The engine heating state detection device according to claim 2.