JPH08218928A - Engine over-rotation prevention device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an engine over-rotation preventing device capable of more reliably determining the fact of racing and preventing over-rotation more reliably. When all the basic conditions for executing the fuel cut control are satisfied and it is determined that the current operating state of the engine 1 is not running the vehicle based on the engine speed and intake pressure, The control device (ECU) 30 is
Basically, it is assumed that the vehicle speed sensor 28 has not failed. In addition to this requirement, when the amount of change in the number of revolutions with respect to the intake pressure is larger than the threshold value, the ECU 30 determines that the vehicle is not running and is in a racing state. When the basic conditions are satisfied and the vehicle is currently traveling, it is determined that the vehicle speed sensor 28 has failed, and fuel cut is not executed.
When it is finally determined that the racing state,
When it is determined that the vehicle speed sensor 28 has not failed and the engine speed exceeds the fuel cut speed, fuel cut is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine over-rotation preventing device, and more particularly to an engine over-rotation preventing device provided with, for example, an electronically controlled fuel supply means.

[0002]

2. Description of the Related Art Conventionally, as this type of technique, for example, one disclosed in Japanese Patent Application Laid-Open No. 5-240100 is known. Generally, in this engine and the engine over-rotation prevention device, the vehicle speed, whether it is in the neutral state,
The cooling water temperature, whether the vehicle speed sensor has failed (failed), and the like are detected. Further, it is determined whether or not these detection results satisfy a predetermined condition. That is, whether the vehicle speed input to the electronic control unit is almost "0", is in a neutral state, whether the cooling water temperature is equal to or higher than a predetermined temperature and warming up is completed, or whether the vehicle speed sensor has failed. Is judged. Then, when all of these conditions are satisfied, the fuel cut is executed when the detected engine speed exceeds the preset set speed.
Due to this fuel cut, an excessive increase in engine speed is suppressed, which in turn prevents damage to engine parts, overheats the exhaust system, improves fuel efficiency, and the like.

By the way, among the above conditions, the vehicle speed input to the control device may be "0" even if the vehicle speed sensor fails. In this case, the vehicle speed is really "0"
It is unknown whether it is actually running or not. Therefore, it is possible to determine the racing state (the state in which the accelerator pedal is greatly depressed in the neutral state) by using the neutral switch or the shift switch, and thereby determine whether or not the vehicle speed sensor has failed. However, if the neutral switch or the like has a switch failure such as disconnection, short circuit, or position shift, it is not possible to properly determine the racing state, and it is not possible to properly determine the failure of the vehicle speed sensor. Therefore, conventionally, the following control has been performed.

That is, the engine speed and intake pressure (engine load) are detected, and based on these detection results,
By referring to a predetermined map as shown in FIG. 6, it is determined whether or not the current driving state is that the vehicle is traveling. When it is in the shaded area in the figure, it is determined that the vehicle is traveling. When such a determination is made, it has been determined that the vehicle speed sensor that has output to the control device has failed if the vehicle speed is "0". In this case, one of the above conditions is not satisfied because the vehicle speed sensor has failed. Therefore, the fuel cut was not performed.

[0005]

However, in the above technique, even when racing, the engine load is close to the engine load when the air conditioner electric load is on. In addition, when the accelerator pedal is slowly depressed, the engine load is
It tends to shift to higher prices. Therefore, even during racing, there is a possibility that the driver may actually enter the shaded area of the map and determine that the vehicle is running.
In such a case, despite racing
The fuel cut may not be executed properly, and as a result, the engine may not be reliably prevented from over-rotating.

The present invention has been made in view of the above-described circumstances, and an object thereof is to prevent over-rotation of an engine capable of more reliably determining the fact of racing and more reliably preventing over-rotation. To provide a device.

[0007]

In order to achieve the above object, in the present invention, as shown in FIG.
Fuel supply means M2 for supplying fuel to the engine, rotation speed detection means M3 for detecting the rotation speed of the engine M1, and the rotation speed detection means M when the vehicle is stopped.
When the rotation speed detected by 3 exceeds the set rotation speed,
A device for preventing excessive rotation of an engine while the vehicle is stopped, comprising: a fuel cut device M4 for controlling the fuel supply device M2 to cut off fuel supply; and a load detection device for detecting a load on the engine M1. Means M5, at least the rotation speed detection means M3 and the load detection means M5
On the basis of the detection result of the above, the operating state determination means M6 for determining whether the current operating state of the engine M1 is the vehicle traveling state, and the rotational speed change amount are calculated based on the detection result of the rotational speed detecting means M3. Rotational speed change amount calculation means M7, the load detection means M5 and the rotational speed change amount detection means M7
Based on the detection result, the racing state determination means M8 for determining whether the current operating state of the engine M1 is in the racing state, and the operating state determination means M6 change the current operating state of the engine M1 to the vehicle running state. Even if it is determined that there is, the racing state determination means M
When it is determined by 8 that the current operating state of the engine M1 is the racing state, it is determined that the vehicle is currently stopped, and the fuel cut compensating means M9 for executing the fuel cut by the fuel cut means M4 is provided. The gist of the establishment is.

[0008]

According to the above construction, as shown in FIG. 1, fuel is supplied to the engine M1 by the fuel supply means M2.
In addition, the rotation speed detection means M3 detects the rotation speed of the engine M1. Then, when the vehicle is stopped and the rotation speed detected by the rotation speed detection means M3 exceeds the set rotation speed, the fuel cut means M4 controls the fuel supply means M2 to cut off the fuel supply. It

Further, the load of the engine M1 is detected by the load detecting means M5. Further, based on at least the detection results of the rotation speed detection means M3 and the load detection means M5, the driving state determination means M6 determines whether the current driving state of the engine M1 is the vehicle running state. On the other hand,
The rotation speed change amount calculation means M7 causes the rotation speed detection means M3.
The rotation speed change amount is calculated based on the detection result of. Further, based on the detection results of the load detection means M5 and the rotational speed change amount detection means M7, the racing state determination means M8
It is determined whether the current operating state of the engine M1 is the racing state. Then, even when the driving state determination unit M6 determines that the current operating state of the engine M1 is in the vehicle traveling state, the racing state determination unit M8 determines that the current operating state of the engine M1 is in the racing state. When the determination is made, the fuel cut compensating means M9 determines that the vehicle is currently stopped, and the fuel cut means M4 executes the fuel cut.

In this way, the racing state judging means M8
Thus, the load detecting means M5 and the rotational speed change amount detecting means M
Based on the detection result of No. 7, whether or not the current operating state of the engine M1 is the racing state can be determined more reliably. Therefore, even when the actual driving state is the racing state, even if the driving state determination means M6 determines that the current operating state of the engine M1 is the vehicle traveling state, the fuel cut compensating means M9 does. It is certified that the vehicle is currently stopped. Then, the fuel cut by the fuel cut means M4 is executed. That is, it is possible to prevent the erroneous determination that the vehicle is running even though the actual driving state is the racing state.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the engine over-rotation preventing device according to the present invention will be described in detail below with reference to FIGS.

FIG. 2 is a schematic configuration diagram showing a device for preventing over-rotation of an engine mounted on a vehicle in this embodiment. Outside air is taken into an engine 1 as an internal combustion engine having a plurality of cylinders (four cylinders in this embodiment) from an air cleaner 3 through an intake passage 2. Simultaneously with the intake of the outside air, the fuel injected from the injector 4 as the fuel supply means provided for each cylinder near the intake port 1a is taken into the engine 1. However, in this embodiment, each cylinder independent injection method is adopted, and the fuel injection from the injector 4 is performed at an independent timing for each cylinder. Then, the mixture of the taken-in fuel and the external air is introduced into the combustion chamber 1b through the intake valve 5a provided for each cylinder. The air-fuel mixture is exploded / combusted in the combustion chamber 1b, a crankshaft (not shown) is rotated, and a driving force is obtained for the vehicle. After that, the exhaust gas after the explosion / combustion is led out to the exhaust passage 6 where the exhaust manifold for each cylinder gathers through the exhaust valve 5b, and is exhausted to the outside.

A throttle valve 8 which is opened and closed in conjunction with an accelerator pedal (not shown) is provided in the intake passage 2. And this throttle valve 8
The amount of intake air to the intake passage 2 is adjusted by opening and closing. A surge tank 9 for smoothing the pulsation of intake air is provided downstream of the throttle valve 8.

In the intake passage 2, an intake air temperature sensor 2 for detecting an intake air temperature THA is provided near the air cleaner 3.
1 is provided. A throttle sensor 22 for detecting the opening of the throttle valve 8, that is, the throttle opening TA is provided near the throttle valve 8. Further, the surge tank 9 is provided with an intake pressure sensor 23 as a load detecting means which communicates with the surge tank 9 and detects an intake pressure (intake pressure) PiM.

On the other hand, in the middle of the exhaust passage 6, there are mainly three harmful components in the exhaust gas, namely, hydrocarbons (H
A three-way catalyst 13 is provided as a catalyst device for simultaneously purifying C), carbon monoxide (CO), and nitrogen oxides (NOx). An oxygen sensor 24 for detecting the oxygen concentration OX in the exhaust gas is provided upstream of the three-way catalyst 13 in the exhaust passage 6. The oxygen sensor 24 has a characteristic that the output voltage changes rapidly near the stoichiometric air-fuel ratio.

The engine 1 is also provided with a water temperature sensor 25 for detecting the temperature of the cooling water (cooling water temperature) THW. The ignition signal distributed by the distributor 11 is applied to the ignition plug 10 provided for each cylinder of the engine 1. The distributor 11 is for distributing the high voltage output from the igniter 12 to each spark plug 10 in synchronization with the crank angle of the engine 1. The ignition timing of each spark plug 10 is the high voltage output timing from the igniter 12. Determined by

The distributor 11 is provided with a rotation speed sensor 26 as rotation speed detecting means for detecting the rotation speed (engine speed) NE of the engine 1 from the rotation of a rotor (not shown) of the distributor 11.
Similarly, the distributor 11 is provided with a crank angle sensor 27 that detects a change in the crank angle of the engine 1 at a predetermined rate according to the rotation of the rotor.
In this embodiment, the engine 1 has 2
As it rotates, the crank angle sensor 27 displays “30 °
The crank angle is detected at a rate of "CA". Further, the transmission (not shown) is provided with a vehicle speed sensor 28 that detects a vehicle speed (vehicle speed) SPD and outputs a signal according to the magnitude of the detected value.
At the same time, the transmission has its shift position Sh.
A shift position sensor 29 that outputs a signal instructing P is provided. In this embodiment, the sensors 21 to 29 constitute an operating state detecting means.

Further, in this embodiment, an electronic control unit (hereinafter simply referred to as "ECU") 3 for controlling fuel injection is provided.
0 is provided. The ECU 30 constitutes a fuel cut means, an operating state determination means, a rotational speed change amount calculation means, a racing state determination means, and a fuel cut compensation means. The intake air temperature sensor 21, the throttle sensor 22, the intake air pressure sensor 23, the oxygen sensor 24, the water temperature sensor 25, the rotation speed sensor 26, the crank angle sensor 27, the vehicle speed sensor 28, and the shift position sensor 29 are connected to the ECU 30, respectively. Has been done. Further, the injector 4 and the igniter 12 are connected to the ECU 30, respectively. Then, the ECU 30 uses the sensors 2
The individual injectors 4 and igniters 12 are drive-controlled based on the detection signals from 1 to 29.

Next, the electrical configuration of the ECU 30 will be described with reference to the block diagram of FIG. The ECU 30 includes a central processing unit (CPU) 31, a read-only memory (ROM) 32 that stores a predetermined control program and the like in advance, a CPU 3
A random access memory (RAM) 33 for temporarily storing the calculation result of 1 and the like, a backup RAM 34 for storing previously stored data, and the like are provided. And ECU3
0 is each of these parts, the external input circuit 35, and the external output circuit 3
6 and the like are connected by a bus 37 as a logical operation circuit.

The external input circuit 35 includes an intake air temperature sensor 21, a throttle sensor 22, an intake air pressure sensor 23,
Oxygen sensor 24, water temperature sensor 25, rotation speed sensor 26,
A crank angle sensor 27, a vehicle speed sensor 28, a shift position sensor 29, etc. are connected to each other. The injector 4 and the igniter 12 described above are connected to the external output circuit 36, respectively.

Then, the CPU 31 reads the detection signals from the sensors 21 to 29 as input values via the external input circuit 35. In addition, the CPU 31 is based on these input values,
The injector 4, the igniter 12, and the like are preferably controlled via the external output circuit 36.

Next, the above-mentioned ECU 30 (strictly speaking, CP
Among the various processing operations performed by U31), the processing operation for determining the current driving state and determining the failure (failure) of the vehicle speed sensor 28 will be described with reference to the flowchart of FIG.

The flowchart shown in FIG. 4 shows a "driving state judgment / vehicle speed sensor failure judgment routine" executed by the ECU 30, which is started at the same time as the cranking of the engine 1 is completed, and thereafter at predetermined time intervals. It is executed by a scheduled interrupt.

When the processing of this routine is started, the EC
First, in step 101, the U30 detects the vehicle speed sensor 2
8, throttle sensor 22, shift position sensor 29, water temperature sensor 25, rotation speed sensor 26 and intake pressure sensor 23
Various signals such as the current vehicle speed SPD, the throttle opening TA, the shift position ShP, the cooling water temperature THW, the engine speed NE, and the intake pressure PiM are read based on the signals from the above.

Next, at step 102, it is judged based on the various signals read this time whether all of the following four conditions (1) to (4) for executing the fuel cut are satisfied. That is, the condition is that the vehicle speed SPD is "10k.
m / h ”or less, the condition is that the throttle opening T
A is “0”, the condition is that the vehicle speed sensor 28 is not failing (Note: What is the judgment?), And the condition is that the cooling water temperature THW is equal to or higher than the predetermined temperature and the warm-up is completed. It is that you are. However, even if the vehicle speed sensor fail flag FSPD is "0" at this point, the vehicle speed sensor 28 may actually fail. And, among the four conditions, 1
If any of the conditions is not satisfied, the current operating state is not the operating state for executing the fuel cut, and the vehicle speed sensor 2
It is judged that the driving condition is not judged to be the failure of No. 8 and the process proceeds to step 103. In step 103, the count value C of the counter is cleared to "0".
Then, the ECU 30 once ends the subsequent processing.

On the other hand, in step 102, if all of the four conditions are satisfied, step 104
Move to. In step 104, the average engine speed (referred to as the past average speed) NESM when the previous engine time NE is traced back is subtracted from the current engine speed NE,
The value is set as the rotation speed change amount DLNE.

Further, in step 105, based on the intake pressure PiM corresponding to the engine load read this time and the rotational speed change amount DLNE calculated this time, referring to the map shown in FIG. Determines whether is in the racing state. That is, the intake pressure P
It is determined whether the rotational speed change amount DLNE for iM is larger than the threshold value in the map of FIG. here,
The threshold value of the map is set in advance based on the amount of change in the number of revolutions at the actual vehicle level, acceleration is performed at each intake pressure from light load to full load at the first (first speed) gear that gives the most acceleration. This is the value that was set. Accordingly, if the rotational speed change amount DLNE is larger than the threshold value, it can be considered that the rotational speed change amount is larger than the rotational speed change amount when the transmission is connected, and it can be considered that the transmission is not connected. it can. That is, it can be determined that the current driving state is the racing state at the time of neutral.

Then, at step 105, when the rotational speed change amount DLNE with respect to the intake pressure PiM is larger than the threshold value, it is considered that the vehicle is in the racing state, and the routine proceeds to step 110. In step 110, the vehicle speed sensor fail flag FSPD is set to "0", the process of step 103 is then executed, and the subsequent process is temporarily terminated without performing the subsequent process.

On the other hand, in step 105, the intake pressure P
If the rotational speed change amount DLNE with respect to iM is smaller than the threshold value, it is determined that there is a high probability that the vehicle is traveling with the transmission connected, and step 10
Go to 6. In step 106, based on the engine speed NE and the intake pressure PiM that have been read this time, it is determined with reference to the map shown in FIG. 6 whether the current operating state of the engine 1 is running the vehicle. That is, it is determined whether or not the intake pressure PiM of this time with respect to the engine speed NE of this time is within the shaded area in the map of FIG. The broken line in the figure indicates the most loaded state in the neutral state (for example, air conditioner on,
It is an engine speed NE-intake pressure PiM characteristic in a headlight / on state). If it is determined that the operating state of the engine 1 is not running, the step 11
Move to 0. In step 110, the vehicle speed sensor fail flag FSPD is set to "0" and
Next, the process of step 103 is executed, and the subsequent processes are once ended without performing the subsequent processes.

If it is determined in step 106 that the operating state of the engine 1 is running, the count value C of the counter is determined in step 107.
Is incremented by "1".

Next, at step 108, it is judged whether or not the count value C of the counter exceeds a predetermined value (corresponding to a predetermined time: for example, 2 seconds) T0. When the count value C has not yet exceeded the predetermined value T0, the process goes back to step 106 to execute the process. Also,
If the count value C still exceeds the predetermined value T0, the process proceeds to step 109.

Then, in step 109, even though the operating state of the engine 1 is running the vehicle,
It is an error that the vehicle speed SPD is output as "10 km / h" or less (which is almost equal to zero), it is determined that the vehicle speed sensor 28 has failed, and the vehicle speed sensor fail flag FSPD is set to "1". Then, the subsequent processing is temporarily terminated.

As described above, in the "driving state determination / vehicle speed sensor failure determination routine", it is determined whether or not the driving state at that time is the racing state, and it is determined whether or not the vehicle speed sensor 28 has failed. To be done.

Next, based on the above judgment and judgment result,
Regarding the control of the cut of the fuel injected from the injector 4 executed to prevent the engine 1 from over-rotating,
Description will be given according to the flowchart of FIG. 7. The flowchart of FIG. 7 is a flowchart showing the “fuel cut control routine” executed by the ECU 30, and is executed for each revolution of the engine 1. However, the fuel cut described below means a fuel cut for preventing excessive rotation during racing, and is a concept different from the fuel cut during running.

When the processing shifts to this routine, first in step 201, the ECU 30 causes the vehicle speed sensor 2 to operate.
8, throttle sensor 22, shift position sensor 29, water temperature sensor 25, rotation speed sensor 26 and intake pressure sensor 23
Various signals such as the current vehicle speed SPD, the throttle opening TA, the shift position ShP, the cooling water temperature THW, the engine speed NE, and the intake pressure PiM are read based on the signals from the above.

Next, at step 202, it is judged based on the various signals read this time whether or not all of the above four conditions (1) to (4) for executing the fuel cut are satisfied. (Note: How do you decide?
When it is determined whether FSPD is “0”, step 205
Will result in a contradiction. ) If any of the four conditions (1) to (4) is not satisfied, the current operating state is not in the operating state in which the fuel cut is executed, and is not in the operating state in which the vehicle speed sensor 28 determines the failure. Then, the process proceeds to step 203. In step 203, the fuel cut flag FCUT is set to "0", and the subsequent process is once ended without performing the fuel cut. Further, in step 202, four conditions ~
If all of the above are satisfied, the process proceeds to step 204.

In step 204, it is determined whether the engine speed NE read this time is greater than the fuel cut speed NHC for executing the fuel cut. The engine speed NE is the fuel cut speed N.
If it is larger than HC, in step 205,
It is determined whether the vehicle speed sensor fail flag FSPD is "1". Here, the vehicle speed sensor fail flag FS
When PD is "1", the vehicle speed sensor 28 has failed, and even if all of the above conditions (1) to (4) are satisfied, that is because the vehicle speed sensor 28 has failed. When it is determined that there is one, the process proceeds to step 203. Then, in step 203, the fuel cut flag FCUT is set to "0", and the subsequent processing is once ended without performing the fuel cut.

If the vehicle speed sensor fail flag FSPD is "0" in step 205, it is determined that the vehicle speed sensor 28 has not failed and the vehicle is in the racing state, and the routine proceeds to step 206. In step 206, the fuel cut flag FCUT is set to "1" to execute the fuel cut, and in the following step 207, the fuel cut determination flag FNHC is set to "1". Then, in step 208,
The fuel cut is executed, and the subsequent processing is once ended.

On the other hand, in step 204, when the engine speed NE is not higher than the fuel cut speed NHC, the process proceeds to step 209. In step 209, the ECU 30 determines whether or not the engine speed NE read this time is higher than the return speed NHR. Here, the return rotational speed NHR is a value smaller than the fuel cut rotational speed NHC, and a certain hysteresis is provided between the return rotational speed NHR and the fuel cut rotational speed NHC.
When the engine speed NE is equal to or lower than the return speed NHR, the fuel cut flag FCUT is set to "0" in step 203 in order to stop the fuel cut and restart the fuel injection. The process ends once.

If the engine speed NE is still higher than the return speed NHR at step 209, the routine proceeds to step 210, where the fuel cut flag FCU is set.
It is determined whether T is "1". Then, if the fuel cut flag FCUT is "1", it is determined that it is necessary to continue the fuel cut until the engine speed NE becomes equal to or lower than the return speed NHR, and the routine proceeds to step 207. In step 207, the fuel cut determination flag FNHC is set to "1", in step 208, fuel cut is executed, and the subsequent processing is temporarily terminated.

Further, in step 210, if the fuel cut flag FCUT is not "1", it is determined that the fuel cut need not be performed, and the subsequent processing is temporarily ended.

As described above, in the "fuel cut control routine", the fuel cut may or may not be executed depending on the operating state at that time. In particular,
When the vehicle speed sensor fail flag FSPD is "1", the vehicle speed sensor 28 has failed even if all the conditions 1 to 5 for executing the fuel cut are satisfied. Is determined to be. Then, in such a case, the fuel cut flag FCUT is set to "0", and the fuel cut is not performed.

Now, in parallel with the above fuel cut control,
The fuel cut rotation speed NHC and the return rotation speed NHR are sequentially set when the fuel cut determination flag FNHC is "1". Next, the control relating to the change of the set rotational speed will be described with reference to the flowchart of FIG. The flowchart of FIG. 8 shows a "set speed change routine" executed by the ECU 30, which is executed by a regular interruption every predetermined time. When the processing shifts to this routine, in step 301, E
The CU 30 determines whether the fuel cut determination flag FNHC is “1”. That is, regardless of whether or not the fuel is currently being cut, for example, it is determined at every predetermined time whether or not the fuel has been cut at least once. When the fuel cut determination flag FNHC is "1", in step 302, a value obtained by subtracting the predetermined value a from the current fuel cut rotational speed NHC is set as the new fuel cut rotational speed NHC, and The value obtained by subtracting the predetermined value b from the return rotation speed NHR of is set as the new return rotation speed NHR.

Next, at step 303, the fuel cut determination flag FNHC is set to "0", and the routine proceeds to step 304. In step 304, the fuel cut rotation speed NHC and the return rotation speed NHR are held within a certain fixed range. That is, NHC0 ≧ NHC
The fuel cut rotation speed NHC and the return rotation speed NHR are set to fall within the range of ≧ NC and NHR0 ≧ NHR ≧ NR. Here, for example, NHC0 is "700
0 rpm ", NHR0 is" 6800 rpm ", NC is" 4000 rpm ", and NR is" 2000 rpm ". Then, the subsequent processing is temporarily terminated.

In this way, at least once every predetermined time
When the fuel cut is performed once and the fuel cut-return is repeated, both the fuel cut rotational speed NHC and the return rotational speed NHR are gradually lowered, and the difference (hysteresis) is gradually increased.

On the other hand, in step 301, when the fuel cut determination flag FNHC is "0", that is, when the fuel cut is not executed within a fixed time, or when the fuel cut is not executed, the routine proceeds to step 305 and the fuel is cut. Processing for increasing the cut rotation speed NHC and the return rotation speed NHR by predetermined values c and d, respectively (where c <
d). Then, the ECU 30 executes the process of step 304 and ends the subsequent process once. This step 30
The fuel cut speed NHC gradually lowered by the return of the fuel cut-return by going through the process of No. 5
Also, the return rotation speed NHR is gradually increased. In this way, in the above-mentioned "set speed change routine", so-called variable control of the fuel cut speed NHC and the return speed NHR is performed.

As described above, according to the engine overspeed prevention device of this embodiment, all four conditions (1) to (5) for executing the fuel cut control are satisfied.
Based on the engine speed NE and the intake pressure PiM, it is determined that the current operating state of the engine 1 is not running the vehicle according to the map shown in FIG. 6 (steps 106, 10).
If it is 8), it is basically considered that the vehicle speed sensor 28 has not failed (step 110). Also,
Further, in the present embodiment, in addition to the requirement, the rotation speed change amount DLNE is calculated (step 104), and
When the rotational speed change amount DLNE with respect to the intake pressure PiM is larger than the threshold value (step 105), it is determined that the vehicle is not running and is in the racing state. There are almost no exceptions to this judgment, so the judgment result is shown in FIG.
It can be said that it is a more reliable one, unlike the conventional technology that relied only on the map of. If it is determined that the vehicle is currently traveling, it is determined that the vehicle speed sensor 28 has failed, and fuel cut is not executed even if the engine speed NE exceeds the fuel cut speed NHC. When it is finally determined that the vehicle is in the racing state, it is determined that the vehicle speed sensor 28 has not failed, and when the engine speed NE exceeds the fuel cut speed NHC, the fuel cut is executed. .

Therefore, even during the racing, unlike the conventional technique in which there is a possibility that the vehicle actually rushes into the hatched area of the map of FIG. It is possible to determine whether or not there is a state. As a result, the excessive rotation of the engine 1 can be prevented more reliably. Further, along with this, the failure of the vehicle speed sensor 28 can be determined more reliably.

In the present embodiment, so-called variable control is adopted when performing fuel cut. In this variable control, the value of the predetermined value b is made larger than the predetermined value a to be subtracted. Therefore, when the fuel cut-return is repeated, the hysteresis gradually increases, and the fuel cut duration gradually increases. As a result, it is possible to prolong the cooling time of the exhaust system, particularly the catalyst, and thus effectively prevent the catalyst from overheating.

The present invention is not limited to the above embodiment, but may be configured as follows, for example. (1) In the above-described embodiment, it is configured to wait for the predetermined time to elapse after it is determined in step 106 that the vehicle is in the running area. Alternatively, it may be determined that the vehicle speed sensor 28 has failed.

(2) In the above embodiment, the so-called variable control is performed at the time of fuel cut, but a simple fuel cut control for cutting the fuel when the engine speed NE exceeds a predetermined set speed. May be

(3) In the above embodiments, the engine 1 is embodied in the case of a gasoline engine, but may be embodied in the case of a diesel engine or the like. (4) In the above-described embodiment, the vehicle speed sensor 28 is determined to be failed as well as the driving state is determined. However, even if the vehicle speed sensor 28 is not determined to be failed,
It may be determined that the vehicle is in the racing state, and the determination result may be used to determine whether or not the control is executed in the fuel cut control.

The technical idea which is not stated in the claims of the present invention and which can be grasped from the above-mentioned embodiment will be described below together with its effect. (A) In the engine overspeed prevention device according to claim 1, a vehicle speed sensor that detects the speed of the vehicle, and a driving state that allows fuel cut based on the detection results including the detection result of the vehicle speed sensor are set. An allowable state determining means for determining whether or not there is a state, and a case where the allowable state determining means determines that the engine is in an operating state in which the fuel cut is permitted, and the racing state determining means determines the current operation of the engine. When it is determined that the vehicle is in the racing state, vehicle speed sensor abnormality determining means for determining that an abnormality has occurred in the vehicle speed sensor is provided.

With such a structure, it is possible to reliably judge the abnormality of the vehicle speed sensor.

[0055]

As described in detail above, according to the engine over-rotation preventing device of the present invention, it is possible to more reliably determine the fact of racing and prevent over-rotation more reliably. Produce an effect.

[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 showing an engine overspeed prevention device according to an embodiment.

FIG. 3 is a block diagram showing an electrical configuration of an ECU in one embodiment.

FIG. 4 is a flowchart showing a “driving state determination / vehicle speed sensor failure determination routine” executed by the ECU.

FIG. 5 is a map that defines a threshold value between an intake pressure and a rotational speed change amount.

FIG. 6 is a map for determining whether or not the vehicle is in a traveling region in the relationship between engine speed and intake pressure.

FIG. 7 is a flowchart showing a “fuel cut control routine”.

FIG. 8 is a flowchart showing a “set speed change routine”.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 4 ... Injector as fuel supply means, 23 ... Intake pressure sensor as load detection means, 26 ...
An ECU that constitutes a rotation speed sensor as rotation speed detection means, 28 ... Vehicle speed sensor, 30 ... Fuel cut means, operating state determination means, rotation speed change amount calculation means, racing state determination means, and fuel cut compensation means.

Claims (1)

[Claims] 1. A fuel supply means for supplying fuel to an engine, a rotation speed detection means for detecting the rotation speed of the engine, and a rotation speed detection means when the vehicle is stopped. A device for preventing excessive rotation of an engine during vehicle stop, comprising: a fuel cut means for controlling the fuel supply means to cut off fuel supply when the rotation speed exceeds a set rotation speed, A load detecting means for detecting the load of the engine, and a driving state judging means for judging whether or not the current driving state of the engine is a vehicle running state based on the detection results of at least the rotational speed detecting means and the load detecting means And a rotation speed change amount calculation means for calculating a rotation speed change amount based on the detection result of the rotation speed detection means, and detection of the load detection means and the rotation speed change amount detection means. Based on the result, a racing state determination means for determining whether or not the current operating state of the engine is a racing state, and a case where the current operating state of the engine is determined to be a vehicle traveling state by the operating state determination means. Even if the racing state determination means determines that the current operating state of the engine is in the racing state, it is determined that the vehicle is currently stopped and the fuel cut means causes the fuel cut to be executed. An engine over-rotation preventing device comprising a fuel cut compensating means.