JPS6157577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a failure detection device for a vehicle speed sensor.

For example, a vehicle speed sensor conventionally used in a constant speed running system for internal combustion engine vehicles is configured to output a pulse signal whose frequency changes depending on the vehicle speed, and the vehicle speed is determined from the period of this pulse signal. is being detected. Therefore, the pulse noise output from the ignition system of the internal combustion engine or various auxiliary equipment is superimposed on the pulse signal output from the vehicle speed sensor, indicating a vehicle speed higher than the actual vehicle speed, or the vehicle speed sensor is about to break. Alternatively, the period of the pulse signal becomes apparently longer due to a connection failure in the internal wiring, etc., which tends to cause problems such as a vehicle speed that is slower than the actual vehicle speed. As a result, for example, in the case of a constant vehicle speed traveling device, the above-mentioned failure of the vehicle speed sensor causes control failures such as sudden deceleration or sudden acceleration. In order to eliminate the above-mentioned defects in the vehicle speed sensor, it is determined whether the value of vehicle speed data obtained by a pulse signal from the vehicle speed sensor is within a preset normal range of vehicle speed data, If this determines that the vehicle speed data is outside the normal range, a vehicle speed sensor failure detection device has been used that determines that the vehicle speed data is abnormal (Japanese Patent Laid-Open No. 57
-Refer to Publication No. 94662). However, this fault detection device cannot distinguish between a state in which a pulse signal is not output because the vehicle speed is zero and a state in which a pulse signal is not output because the vehicle speed sensor is faulty, so complete failure detection cannot be performed. It has the disadvantage of not being able to

In addition, a device configured to install two vehicle speed sensors and detect abnormalities by comparing two vehicle speed signals obtained from these vehicle speed sensors was disclosed in Japanese Patent Application Laid-Open No. 1983-
This device, which is disclosed in Japanese Patent No. 147062, has a complicated circuit configuration because it uses two vehicle speed sensors, which increases the failure rate and is expensive.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a highly reliable vehicle speed sensor failure detection device that eliminates the above-mentioned drawbacks of the prior art and is capable of reliably detecting vehicle speed sensor failures. .

The present invention provides a failure detection device for a vehicle speed sensor that outputs a pulse train signal whose cycle changes depending on the vehicle speed of an internal combustion engine vehicle, in which a first device detects that the output of the pulse train signal from the vehicle speed sensor has stopped.
It has a detection means, a second detection means for detecting engagement and disengagement of the clutch, and a third detection means for detecting that the rotational speed of the internal combustion engine is equal to or higher than a set value,
In response to each detection result from the first, second, and third detection means, the rotational speed of the internal combustion engine is equal to or higher than the above-mentioned set value, the clutch is connected, and the output of the pulse train signal is stopped. The vehicle speed sensor is characterized in that it is determined that the vehicle speed sensor is malfunctioning if the vehicle speed sensor fails.

According to the above configuration, since the clutch connection state and the rotational state of the internal combustion engine are taken into consideration, even if the pulse signal from the vehicle speed sensor stops, it is possible to determine whether it is because the vehicle speed has become zero. Or, it can be easily determined whether the problem is caused by a vehicle speed sensor failure, and sensor failure can be detected more reliably than in the past.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows an embodiment of a constant vehicle speed traveling device equipped with a failure detection device according to the present invention. The constant vehicle speed running device 1 is a device for controlling the speed of a vehicle using an internal combustion engine as a drive source so that the speed of the vehicle is maintained at a desired speed. Source vehicle 3
A case is shown in which the vehicle is configured to control the vehicle speed of the vehicle. The diesel engine 2 is connected to a running gear 3b via a clutch 3a. An actuator 4 is connected to a fuel adjustment member (not shown) for adjusting the amount of fuel supplied to the diesel engine 2, and in response to a control signal _S1 supplied from a control unit 5, An actuator 4 is configured to position the fuel adjustment member.

The control unit 5 is provided with a storage section 6 in which the control program is stored, and a central processing unit (CPU) 7 for executing the control program. /O) 8, various data and control signals are input. That is, the control unit 5 includes a vehicle speed sensor 9 connected to the traveling device 3b and a rotation speed sensor 10 connected to the diesel engine 2.
The vehicle speed sensor 9 outputs a first pulse signal S2, which is a pulse signal whose cycle changes depending on the vehicle speed, and the rotation speed sensor 10 outputs a first pulse signal _S2 whose cycle changes depending on the speed of the internal combustion engine. A second pulse signal _S3 , which is a pulse signal, is output. The first and second pulse signals S ₂ and S ₃ are waveform-shaped by corresponding interface circuits (I/F) 11 and 12, respectively, and inputted to the CPU 7 via the input/output device 8 using a well-known method. The data is converted into binary data indicating vehicle speed and engine speed.

On the other hand, in order to set and release the desired vehicle speed, a switch section 13 including various switches is provided in the control unit 5, and signals outputted in response to opening/closing operations of these switches are sent to the interface. The signal is inputted to the input/output device 8 via the circuit 14 and then inputted to the CPU 7. Switch part 1
The switches configuring 3 are main switch 15,
A brake switch 16, a set switch 17, a resume switch 18, and an acceleration switch 1, which are closed by stepping on a brake pedal (not shown).
9 and a clutch switch 20 which is opened when the clutch is connected, and a main switch 15.
By closing the switch, the set switch 17, the resume switch 18, and the acceleration switch 19 become operable, and execution of constant speed driving control is permitted.

When the set switch 17 is operated with the main switch 15 closed, the set switch 17
The data indicating the vehicle speed at the timing when the door is once closed and then opened is stored as the target vehicle speed in the storage unit 6.
is set, and constant speed driving control is started. The constant speed running control is temporarily released by depressing the brake pedal or releasing the clutch, and then returned to the constant speed control by operating the resume switch 18. Further, the acceleration switch 19 is operated when accelerating the target vehicle speed. As data indicating the vehicle speed, binary data obtained by the input/output device 8 based on the first pulse signal _S2 from the vehicle speed sensor 9 as described later is used. The binary data indicating the vehicle speed is updated at predetermined time intervals, and the actual vehicle speed data indicating the vehicle speed at that time is compared with the data indicating the target vehicle speed mentioned above, and the fuel required to make the difference between the two vehicle speeds zero is calculated. The supply amount is calculated. Position control data D, which is a signal indicating the position of the fuel adjustment member necessary to obtain the calculated fuel supply amount, is outputted via the input/output device 8, and converted into an analog signal by a digital-to-analog converter (D/A) 21. The signal is converted into a signal, amplified by an amplifier 22, and applied to the actuator 4 as a control signal _S1 .

FIG. 2 shows the first signal output from the vehicle speed sensor 9.
An embodiment of a signal processing circuit for converting the pulse signal _S2 into binary data indicative of vehicle speed is shown. The signal processing circuit 31 is a component of the input/output device 8, and is triggered at the rising edge of the vehicle speed pulse signal S′ ₂ obtained by waveform-shaping the first pulse signal S ₂ from the vehicle speed sensor 9 by the interface circuit 11. One-shot multivibrator 32
, whose output terminal is a binary counter 33
is connected to the enable terminal ENA.

As can be seen from FIGS. 3a and 3b, the level of the output terminal of the one-shot multivibrator 32 falls in response to the rise in the level of the vehicle speed pulse signal _S'2 , and remains at the "L" level for a predetermined time _T1 . After maintaining the level, the level becomes "H" again, which is repeated. Therefore, only when the level is "H", the binary counter 33 is activated by the clock pulse generator (not shown) provided inside the CPU 7.
Count the number of clock pulses CL from CL.

The Q output terminal of the one-shot multivibrator 32 is connected to the other one-shot multivibrator 3.
4, the one-shot multivibrator 34 is triggered in response to the falling level Q of the Q output terminal of the one-shot multivibrator 32, and the level RES of the Q output terminal is set to a predetermined level. It is held at the "H" level for a time _T2 (see Figure 3c, d). The Q output of the one-shot multivibrator 34 is applied to the reset terminal RES of the binary counter 33, and the binary counter 33 is reset at the rising edge of the Q output.

Therefore, at the same time that the level changes from "L" to "H" and the binary counter 33 becomes ready for counting, the Q of the one-shot multivibrator 34 changes.
The binary counter 33 is reset by the rise of the output and starts counting the clock pulses CL. Then, at the same time as the binary counter 33 stops counting due to the fall of the level, the level Q rises, and in response to this, the count output data Dc from the binary counter 33 is transferred to the latch circuit 3.
It is latched at 5. The latched data is
It is transferred to a predetermined address in the storage unit 6 by the CPU 7 and stored, and then the latch circuit 35
The reset pulse output from CPU7 is
RP is applied and reset. The value of time T ₁ is
In reality, it is set to be extremely short compared to the period of the clock pulse CL, and therefore the "H" level period is substantially the same as the period of the vehicle speed pulse signal.
The period coincides with the period of the vehicle speed pulse signal S' ₂ , and the count output from the binary counter 33 is data indicating the period of the vehicle speed pulse signal S' ₂ . Based on this data, the CPU 7 calculates vehicle speed data indicating the speed of the vehicle.

FIG. 4 shows a flowchart of a program for detecting a failure in the vehicle speed sensor of the device shown in FIG. This failure determination program reads the count output data Dc (see FIGS. 2 and 3) from the latch circuit 35, which is data indicating the cycle of the vehicle speed pulse signal S' ₂ (see FIGS. A check is made to see if any fault determination has been issued. (Step b). This check is performed based on a failure flag set in step k, which will be described later. If a failure has already been determined, the program for determining the failure will not be executed.
The control is completely canceled (step c), and if no failure has been determined yet, it is determined whether the vehicle speed sensor is malfunctioning or not according to the following procedure.

First, in step d, it is determined whether the value of the count data Dc read in step a is within a predetermined normal range. This normal range is the range of vehicle speeds that can normally occur, for example, when the vehicle speed V is 0.
The range of count data corresponding to Km/h<V≦200Km/h can be set, and if the value of count data Dc is within the normal range determined in this way, registers A and B are set to zero (step e), and the vehicle speed is calculated based on the counting data Dc (step f).

On the other hand, if the determination result in step d is NO, it is further determined whether or not the vehicle speed value indicated by the vehicle speed cycle data is zero (step g). data dc
If the vehicle speed indicated by is higher than 200 km/h, the contents of register A are incremented by 1 (step h), and it is determined whether the contents of register A are equal to a predetermined value _A0 ( Step i). If the contents of register A are still smaller than _A0 , proceed to step j, change the value of count data Dc to the latest value within the normal range before the value of Dc deviated from the normal range, and change this normal value. Vehicle speed is calculated based on the value of Dc. However, the value of data Dc is 200
When a state indicating a vehicle speed higher than Km/h occurs _A0 times in a row, the contents of cylinder A becomes _A0 , the process proceeds from step i to step k, a display indicating that the vehicle speed sensor is malfunctioning is displayed, and a malfunction flag is set. is set, and the constant vehicle speed running control is canceled (step c). Therefore, if the value of the count data Dc deviates from the normal range due to temporary reasons, such as pulse noise being temporarily superimposed on the first pulse signal _S2 , the young and the contents of register A are
By the time _A0 is reached, the cause has been removed, the determination result at step d becomes YES, and step e is passed, so that the contents of register A become zero again, and the predetermined value is reached without the control being released. Constant vehicle speed driving control can be continued.

The value of count data Dc is not in the normal range, and
If the vehicle speed indicated by the counting data Dc is zero, it is determined from the determination of the clutch connection state and engine speed state at step m that the problem is due to the vehicle speed being zero or a malfunction of the vehicle speed sensor. Determine whether the That is, in step F, it is determined whether the clutch switch is ON or not, and if the clutch switch is ON (clutch disengaged state), it is considered that the vehicle speed sensor is not malfunctioning, so proceed to step f and calculate the vehicle speed. . The clutch switch is OFF, i.e.
If it is determined that the clutch is connected, it is further determined whether the engine speed N _E is higher or lower than a predetermined engine speed N _EO (step m);
If N _E ≦N _EO , even if the clutch is engaged, it is determined that the vehicle speed has become zero due to a decrease in engine speed, and therefore step f is executed in this case as well. Note that the predetermined engine speed N _EO is set to a sufficiently low value that the vehicle speed sensor does not become inoperable. The discrimination result in step m is
If YES, it is determined that an abnormality or failure has occurred in the vehicle speed sensor, and the contents of register B are incremented by 1 (step n), and the controller checks whether the contents of register B match a predetermined value _B0 . This determination is made (step o). Steps n and o are provided for the same purpose as steps h and i described above, and when the contents of register B match _B0 , a vehicle speed sensor failure is displayed (step k) and the vehicle is driven at a constant speed. The control is released (step c).

In this way, the first stage of failure determination is performed by determining whether the value of count data Dc is within a predetermined range, and when the vehicle speed value indicated by the value of count data Dc is zero, The second stage of failure determination is performed by determining from the clutch connection state and engine speed whether the pulse signal output stops due to a failure of the vehicle speed sensor or the pulse signal output stops due to the vehicle speed becoming zero. Therefore, failure of the vehicle speed sensor can be completely and reliably detected.

Note that in the above embodiment, the determination in step d is performed when the count data falls within the normal range fixedly set in advance.
This was done based on whether or not there was a Dc value, but this determination is not limited to this. For example, the normal speed range is ±10 km/h relative to the vehicle speed set as a target, and the counting data It may be determined whether the vehicle speed sensor is normal or abnormal depending on whether the vehicle speed indicated by Dc is within this range.

Furthermore, when the constant speed driving control is canceled in step c, the fuel supply amount before the control is canceled is memorized.
When a control release command is issued, the fuel supply amount is gradually decreased based on the value obtained by subtracting a predetermined value from the stored fuel supply amount value at a predetermined time interval, and a predetermined time elapses. The fuel supply amount is then reduced to zero. According to such a control release method, the vehicle speed can be gradually reduced without suddenly decelerating the vehicle, and the vehicle can be safely stopped.

In the above embodiment, a case has been described in which failure detection is performed in a vehicle speed sensor provided in a constant vehicle speed running device, but the present invention is not limited to this, and failure detection in a vehicle speed sensor used for other purposes is described. It can also be applied to, and similar effects can be obtained.

According to the present invention, as described above, the presence or absence of a failure in the vehicle speed sensor is detected from the output signal of the vehicle speed sensor in consideration of the clutch connection state and the speed of the internal combustion engine. It is possible to reliably distinguish between the stoppage of the output of a predetermined signal from the vehicle speed sensor and the stoppage of the output of the predetermined signal due to a failure of the vehicle speed sensor, and more reliable failure determination of the vehicle speed sensor can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a constant vehicle speed traveling device equipped with a vehicle speed sensor failure device according to the present invention, FIG. 2 is a block diagram showing a signal processing circuit for processing the first pulse signal, and FIG. Figures a to 3d are time charts for explaining the operation of the signal processing circuit shown in Figure 2, and Figure 4 shows a failure of the vehicle speed sensor loaded in the device shown in Figure 1. This is a flowchart of a program for determination. 1... Constant speed running device, 2... Diesel engine, 3
...Vehicle, 3a...Clutch, 5...Control unit, 9
...Vehicle speed sensor, 10...Rotational speed sensor, 13 _... Switch section, 20...Clutch switch, S1...Control signal, _S2 ...First pulse signal, _S3 ...Second pulse signal,
S′ ₂ ...Vehicle speed pulse signal.

Claims (1)

[Claims] 1. In a failure detection device for a vehicle speed sensor that outputs a pulse train signal whose period changes depending on the vehicle speed of an internal combustion engine vehicle, a first means for detecting that the output of the pulse train signal from the vehicle speed sensor has stopped, and a clutch connection , second means for detecting a disconnection condition;
a third means for detecting that the rotational speed of the internal combustion engine is equal to or higher than a predetermined set speed; and a third means for detecting that the rotational speed is equal to or higher than the set value; A failure detection device for a vehicle speed sensor, comprising means for outputting a signal indicating a failure of the vehicle speed sensor when a clutch is connected and output of the pulse train signal is stopped.