JPS62223671A - Abnormality detecting device for vehicle speed detecting device - Google Patents

Abstract

PURPOSE:To detect abnormality successively during vehicle drive by comparing the vehicle speed obtained based on vehicle driving states other than a vehicle speed with a vehicle speed detected by a vehicle speed sensor. CONSTITUTION:A vehicle speed detecting device detects the vehicle speed based on the vehicle speed signal from the vehicle sensor coupled with a propeller shaft. A vehicle driving state detecting means, on the other hand, detects vehicle driving states including at least the rotating speed of an internal combustion engine except the vehicle speed. Further, a vehicle speed storage means stores a set vehicle speed which is a specific speed lower than a vehicle speed forecasted according to the driving states detected by the driving state detecting means and a vehicle speed retrieval means retrieves the vehicle speed stored in the vehicle speed storage means based on the detected driving states. Then, a vehicle speed sensor abnormality detecting means compares the retrieved vehicle speed with the vehicle speed detected based on the vehicle speed signal from the vehicle speed sensor to detect the abnormality of the vehicle speed sensor and an abnormality detection signal output means outputs a vehicle speed abnormality detection signal at the time of the vehicle speed sensor abnormality detecting means detects the abnormality.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an abnormality detection device for a vehicle speed detection device for a vehicle.

(Prior art) A conventional vehicle speed detection device measures the period of a pulse signal from a vehicle speed sensor that generates a pulse signal in synchronization with the rotation of the vehicle's propulsion shaft, and detects the vehicle speed, which is the reciprocal of the period. There is something I did. In this case, as shown in FIG. 5, the period from the rise of the pulse signal from the vehicle speed sensor to the next rise is counted at a constant time interval τ, and the period T of the pulse signal is calculated from the count value N and the time interval. The vehicle speed was detected by a method called the so-called count pulse method, which calculates =N·τ and calculates the vehicle speed VSP=/T (K is a constant) (see Utility Model Application No. 95075, etc.).

In addition, when such a vehicle speed detection device is used to perform control according to vehicle speed (for example, determining the shift point in an automatic transmission), if a problem such as a disconnection of the signal line from the vehicle speed sensor occurs, it may cause problems during driving. However, since no pulse signal is detected even when the ignition switch is turned on, the vehicle speed is determined to be O and incorrect control is performed. Therefore, it is necessary to detect abnormalities such as disconnection of the vehicle speed sensor. If the detected vehicle speed exceeds a predetermined speed (for example, 8 km/h) even once, the vehicle speed sensor is determined to be normal, and if the detected vehicle speed does not exceed the predetermined speed, an abnormality detection signal is issued and a predetermined fail-safe process is performed. was.

<Problems to be Solved by the Invention> However, with such conventional abnormality detection, there is a problem that once a predetermined speed is exceeded and a normality determination is made, abnormality detection cannot be performed even if a problem such as a disconnection occurs afterwards. there were.

In other words, if the vehicle speed detected by the vehicle speed sensor after the ignition switch is turned on exceeds a predetermined speed (abnormality determination level) even once, the ignition switch is turned off.
Since the normality judgment is maintained until F is detected, as shown in Fig. 6, even if a malfunction occurs after the normality judgment, there is a risk that this abnormality will not be detected and control will be performed based on the incorrect detection result. It is something.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an abnormality detection device that increases the chances of abnormality detection in a vehicle speed detection device and can quickly determine an abnormality.

Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. 1, a vehicle speed detection device that detects the speed of a vehicle based on a vehicle speed signal from a vehicle speed sensor connected to a propulsion shaft of the vehicle is provided. a vehicle driving state detection means for detecting a vehicle driving state other than vehicle speed, including at least the rotational speed of an internal combustion engine mounted on the vehicle;
a vehicle speed storage means storing a vehicle speed preset to a speed smaller than a predicted vehicle speed by a predetermined speed according to the predetermined vehicle driving state detected by the vehicle driving state detection means; vehicle speed retrieval means for retrieving the vehicle speed stored in the vehicle speed storage means; and vehicle speed sensor abnormality for detecting an abnormality in the vehicle speed sensor by comparing the retrieved vehicle speed with a vehicle speed detected based on a vehicle speed signal from the vehicle speed sensor. An abnormality detection device for a vehicle speed detection device is constituted by a detection means and an abnormality detection signal output means for outputting a vehicle speed sensor abnormality detection signal when an abnormality in the vehicle speed sensor is detected by the vehicle speed sensor abnormality detection means.

According to the abnormality detection device having such a configuration, the abnormality is detected by comparing the vehicle speed obtained based on the vehicle driving state other than the vehicle speed with the vehicle speed detected by the vehicle speed sensor, so that abnormality detection is performed sequentially during vehicle operation. Is possible.

The vehicle operating state includes not only the engine rotation speed but also the gear position, clutch engagement, etc. If the driving force of the engine is transmitted to the wheels, the vehicle speed should be approximately proportional to the engine rotation speed. Therefore, if transmission of engine driving force is detected by detecting gear position and clutch engagement as described above, the resulting vehicle speed can be predicted.

Therefore, a vehicle speed that is smaller than the vehicle speed predicted based on the vehicle driving condition (vehicle speed that should not be detected when the vehicle speed sensor is normal) is stored in the vehicle speed storage means, and the vehicle speed that is actually detected by the vehicle speed sensor is stored. An abnormality in the vehicle speed sensor can be detected by comparing the vehicle speed retrieved by the vehicle speed retrieval means based on the vehicle driving state.

<Example> An embodiment of the present invention will be described below based on the drawings.

In FIG. 2, a vehicle speed sensor 1 generates a pulse signal in synchronization with the rotation of a propulsion shaft (not shown) of the vehicle. That is, the reed switch 4 is turned on when the magnetic pole of a rotating magnet 3, which is connected to a propulsion shaft (for example, an output shaft of a transmission, a propeller shaft, or an axle) of a vehicle (not shown) via a flexible wire 2, approaches.
Generates a pulse signal by turning off.

5 is a control unit with a built-in microcomputer, and CPU6. ROM7. It is equipped with a RAM 8, an input/output interface 9, etc., and calculates the vehicle speed VSPx based on the pulse signal from the vehicle speed sensor 1, and controls the operation of various control devices (for example, a speed change device of an automatic transmission) 10 according to the calculation results.

The control unit 5 also includes a neutral switch 1) which turns on when the transmission is in the neutral position. Clutch switch 1 that turns on when the clutch is disconnected
2 and a rotational speed sensor 13 that detects the rotational speed N of an internal combustion engine mounted on the vehicle. These neutral switches 1). The clutch switch 12 and the rotational speed sensor 13 correspond to the vehicle driving state detection means in this embodiment.

Here, the microcomputer in the control unit 5 has functions as a vehicle speed storage means, a vehicle speed retrieval means, a vehicle speed sensor abnormality detection means, and an abnormality detection signal output means, as shown in the flowchart of FIG. 3 (abnormality detection routine).
It is equipped with software as shown in the figure below.

Next, the operation will be explained based on the flowchart shown in FIG.

First, in step (indicated as "S" in the figure, the same applies hereinafter) ■, turn on/off the neutral switch 1).
When it is OFF, that is, the transmission gear is engaged, the process proceeds to the next step 2, and when it is ON, that is, it is in the neutral state, it returns.

In step 2, the clutch switch 12 is turned on and off.
As in step 1, when the clutch is OFF, that is, when the clutch is connected, the process proceeds to the next step 2, and when it is ON, that is, when the clutch is disengaged, the process returns.

In this way, abnormality detection of the vehicle speed sensor 1 in this embodiment is performed by the neutral switch 1) and the clutch switch 12.
This is performed when both are OFF and the rotational driving force of the engine mounted on the vehicle is being transmitted to the wheels.

In step 3, the vehicle speed VSPx detected by measuring the period of the pulse signal from the vehicle speed sensor 1 is read.

In step 4, the engine rotation speed N detected by the rotation speed sensor 13 is read.

In step 5, the vehicle speed VSPx read in step 3
is greater than or equal to the value obtained by multiplying the engine rotational speed N read in step 4 by a preset constant K (V S Px
≧KXN).

The constant is set as follows depending on the vehicle. In other words, when the driving force of the internal combustion engine mounted on the vehicle is transmitted to the wheels, the vehicle speed increases approximately in proportion to the engine rotational speed N, and the rate of increase increases as the gear ratio of the transmission gear increases. It becomes sudden. Therefore, the vehicle speed exhibits the characteristics shown in FIG. 4, and in this embodiment, the vehicle speed at the first gear of the transmission gear (the transmission gear position where the gear ratio is the smallest) where the vehicle speed is the smallest relative to the engine rotational speed N. A vehicle speed that is sufficiently smaller than (vehicle speed that is not detected when the vehicle speed sensor is normal) is set as the judgment level for abnormality detection, and this judgment level (judgment vehicle speed) is calculated from the engine rotation speed N. The constant K is set so that In principle, the determination level may be stored in correspondence with the engine rotation speed N, and in this case, the vehicle speed as the determination level is searched based on the engine rotation speed N.

In this way, the judgment level is set sufficiently lower than the vehicle speed obtained in the first gear, so if the vehicle speed sensor 1 is normal, the determination level is set to be sufficiently lower than the vehicle speed obtained in the first gear. state) detected vehicle speed VSPx
should never fall below this judgment level.

Therefore, in step 5, No, that is, vSPx<K
When it is determined that the vehicle speed sensor 1 is XN, it is presumed that some kind of abnormality has occurred in the vehicle speed sensor 1. When an abnormality in the vehicle speed sensor l is detected in this manner, an abnormality detection signal is output in step 6. This abnormality detection signal is
It is used as a start signal for predetermined fail-safe processing.

The abnormality detection of the vehicle speed sensor 1 described above is always performed as long as the neutral switch 1) and the clutch switch 12 are OFF, and unlike conventional methods, an abnormality is detected only once between the start and stop of the engine. It's not something you don't do. Therefore, the chances of abnormality detection are increased, and prompt abnormality detection becomes possible.

In addition, the abnormality determination level is set corresponding to each transmission gear by detecting the transmission gear position (for each transmission gear, the abnormality determination level is set at a predetermined speed lower than the predicted vehicle speed based on the relationship with the engine rotation speed). An abnormality in the vehicle speed sensor 1 may be detected based on the vehicle speed.

<Effects of the Invention> As explained above, according to the present invention, an abnormality in the vehicle speed sensor is detected by comparing the vehicle speed retrieved based on the driving state of the vehicle and the vehicle speed detected by the vehicle speed sensor. This increases the chances of detecting an abnormality, making it possible to detect the abnormality as quickly as possible, and suppressing the occurrence of malfunctions due to control being performed based on incorrect vehicle speed.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a hardware configuration diagram showing an embodiment of the present invention, Fig. 3 is a flowchart of the same embodiment, and Fig. 4 shows the relationship between engine rotation speed and vehicle speed. FIG. 5 is a time chart showing the relationship between the pulse signal from the vehicle speed sensor and the count value, and FIG. 6 is a time chart showing the abnormality detection characteristics of a conventional abnormality detection device. 1... Vehicle speed sensor 5... Control unit 1)... Neutral switch 12... Clutch switch 13... Rotational speed sensor Figure 3 Figure 4 Figure 5 2 Figure 6

Claims (2)

[Claims] (1) In a vehicle speed detection device that detects the speed of a vehicle based on a vehicle speed signal from a vehicle speed sensor connected to the propulsion shaft of the vehicle, the vehicle is operated at a speed other than the speed that includes at least the rotational speed of the internal combustion engine mounted on the vehicle. Vehicle driving state detection means for detecting a state; and a vehicle speed memory storing a vehicle speed preset to a speed smaller than a predicted vehicle speed by a predetermined speed according to a predetermined vehicle driving state detected by the vehicle driving state detection means. means, vehicle speed retrieval means for retrieving the vehicle speed stored in the vehicle speed storage means based on the detected vehicle driving state, and comparing the retrieved vehicle speed with the vehicle speed detected based on the vehicle speed signal from the vehicle speed sensor. a vehicle speed sensor abnormality detection means for detecting an abnormality in the vehicle speed sensor; and an abnormality detection signal output means for outputting a vehicle speed sensor abnormality detection signal when the vehicle speed sensor abnormality detection means detects an abnormality in the vehicle speed sensor;
An abnormality detection device for a vehicle speed detection device comprising: (2) The vehicle speed storage means records a vehicle speed that is a predetermined speed smaller than the vehicle speed predicted from the relationship between the transmission gear position with the smallest gear ratio and the engine rotational speed while the engine driving force is being transmitted to the wheels. An abnormality detection device for a vehicle speed detection device according to claim 1, characterized in that a preset vehicle speed is stored.