JPH07102819B2 - Power steering control device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a control device for a power steering apparatus that controls an oil flow rate in accordance with a vehicle speed.

[Prior art]

Conventionally, a power steering apparatus generates a vehicle speed signal that determines a repetition cycle of "1" level and "0" level corresponding to a vehicle speed, and based on this vehicle speed signal, the oil flow rate decreases as the vehicle speed increases. It is in control. Therefore, it is possible to perform steering with a small steering force over a wide vehicle speed range.

However, if the circuit including the vehicle speed sensor that generates the vehicle speed signal is short-circuited during high-speed traveling, the vehicle speed signal will not be obtained, and the power steering system will control so that the oil flow rate will be the maximum, so the steering force will be steep. It becomes very small and dangerous. For this reason, various detection methods have been proposed in the past, but all of them were poor in reliability and economical.

[Object and Structure of Invention]

Therefore, an object of the present invention is to provide a control device for a power steering system which can detect a short circuit of a vehicle speed sensor with high reliability and economical efficiency and perform safe driving.

In order to achieve such an object, the present invention uses a vehicle speed sensor that fixedly sends out a signal of "1" level when the vehicle speed sensor is short-circuited, and the output signal of the vehicle speed sensor is kept at "1" level. The vehicle speed sensor is short-circuited by detecting that Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is a vehicle speed sensor that generates a number of pulse-shaped electric signals corresponding to the vehicle speed as a vehicle speed signal, 2 is a voltage conversion circuit that converts the vehicle speed signal into a DC voltage, 3 is an amplification circuit, 4 is a solenoid drive circuit, 5 Reference numeral 6 is a short circuit detection circuit for detecting a short circuit of the vehicle speed sensor 1, 6 is a disconnection detection circuit for detecting a disconnection of the vehicle speed sensor 1, and 7 is a control circuit for controlling the oil flow rate to a value at which safe operation can be performed when the vehicle speed sensor 1 is short circuited. , 8 are control circuits for controlling the oil flow rate to a value at which safe operation can be performed when the vehicle speed sensor 1 is disconnected.

The vehicle speed sensor 1 is composed of a magnet 1a, a coil 1b, resistors 1c to 1e, a comparator 1f, and a transistor 1g. The magnet 1a is designed to rotate integrally with the speedometer cable, and the coil 1b is rotated along with the rotation of the magnet 1a. A voltage is induced. The resistors 1c and 1d are connected to one terminal of the comparator 1f.
The bias voltage is supplied in advance by, and the signal induced in the coil 1b is supplied to the other terminal. Therefore, when a signal is induced in the coil 1b, the comparator 1f
A voltage difference is generated between the two input terminals of and the output level of the comparator 1f changes accordingly. When the internal circuit of the sensor 1 is short-circuited, that is, when the coil 1b is short-circuited, the two input terminals of the comparator 1f are supplied with the same level, that is, the same bias voltage. Since this bias voltage is generally set to about half the power supply voltage, the output signal level of the comparator 1f is also about half the power supply voltage.

Since the output signal is supplied to the base of the transistor 1f, the transistor 1f becomes conductive, and the "1" level signal is output to the resistor 1e. That is, when the vehicle speed sensor 1 is normal, the "0" level signal and the "1" level signal are alternately output, but when the vehicle speed sensor 1 is short-circuited, the "1" level signal is fixedly output. The voltage conversion circuit 2 has a resistor 2a
~ 2d, capacitors 2e ~ 2g, transistor 2h, diode
It is composed of 2i and 2j, and generates a DC voltage whose voltage drops as the vehicle speed signal goes into a high speed state. The amplifier circuit 3 is adapted to in-phase amplify the input signal. The solenoid drive circuit 4 is composed of resistors 4a to 4o, capacitors 4p to 4r, a diode 4s, a comparator 4t, and transistors 4u and 4v, and generates a pulse signal with a reduced duty ratio as the supplied input signal decreases. To do.
The short circuit detection circuit 5 includes resistors 5a to 5c, diodes 5d and 5e, capacitors 5f and 5g, and a comparator 5h. The disconnection detection circuit 6 is composed of resistors 6a to 6d, capacitors 6e and 6f, a diode 6g, and a comparator 6h. The control circuit 7 is composed of a resistor 7a, a capacitor 7b, and a transistor 7c. The control circuit 8 has resistors 8a to 8d and capacitors 8e to 8
g, diode 8h, varistor 8i, relay 8j, contact 8k of relay 8j, and transistor 8l.

A solenoid valve (not shown) is connected between the output terminals SOLl and SOL2 of the solenoid drive circuit 4. This solenoid valve has a larger opening degree as the duty ratio of the current flowing therethrough increases, thereby increasing the oil flow rate. A structure having a structure that acts so as to be used is used. Also, when no current is supplied thereto, the oil supply to the power steering device is reduced.

The operation of the circuit thus configured is as follows. When the vehicle runs, the pulse-shaped vehicle speed signal generated from the vehicle speed sensor 1 is converted into a DC voltage by the voltage conversion circuit 2. This DC voltage is amplified by the amplifier circuit 3 and supplied to the solenoid drive circuit 4. At this time, the magnitude of the DC voltage obtained from the voltage conversion circuit 2 decreases as the vehicle speed increases, and the solenoid drive circuit 4 generates a pulse signal with a smaller duty ratio as the input signal size decreases. Therefore, the solenoid drive circuit 4 sends a pulse signal having a smaller duty ratio as the vehicle speed increases. Therefore, the oil flow rate supplied to the power steering device via the solenoid valve is controlled to be large at low speed and small at high speed, so that stable steering can be performed from low speed to high speed.

Next, the operation of the short circuit detection circuit 5, which is a characteristic part of the present invention, will be described.

When the vehicle is running, the vehicle speed sensor 1 generates a vehicle speed signal in which "1" level and "0" level are repeatedly generated as shown in FIG.

The capacitor 5f of the short circuit detection circuit 5 is charged through the resistor 5a when the vehicle speed signal "1" is at the level, and discharged through the diode 5d when the vehicle speed signal is at the "0" level. Therefore, since the charging time constant is large and the discharging time constant is small, the terminal voltage of the capacitor 5f never reaches the "1" level, and the voltage of the non-inverting input terminal of the comparator 5h becomes "a" in FIG. As shown, "1" level voltage
It will be smaller than V1. At this time, if the voltage of the inverting input terminal of the comparator 5h is set to a value lower than the voltage V1 of "1" level and higher than the maximum voltage of "a" as shown in "b", the voltage of the comparator 5h Since the voltage "b" at the inverting input terminal is always higher than the voltage "a" at the non-inverting input terminal, the output of the comparator 5h is always at "0" level.

On the other hand, when a short-circuit failure occurs inside the vehicle speed sensor 1 and a continuous signal of "1" level is transmitted from there, the voltage supplied to the non-inverting input terminal of the comparator 5h is shown in FIG. As shown in "a", the voltage rises from the time t1 when the failure occurs until the voltage V1 of "1" level is reached. Therefore, the voltage "a" at the non-inverting input terminal exceeds the voltage "b" at the inverting input terminal at time t2, so that the comparator 5h sends an output signal of "1" level after time t2.

This signal is supplied to the control circuit 7 to turn on the transistor 7c, so that the transistor 4v of the solenoid drive circuit 4 is turned on.
The base of is grounded. Therefore, the transistors 4u and 4v are turned off, and the pulse signal is not supplied to the solenoid valve (not shown) connected to the terminals SOL1 and SOL2. Therefore, when a short-circuit failure occurs in the vehicle speed sensor 1, the oil supplied from the solenoid valve to the power steering apparatus decreases, so that the required steering force changes in an increasing direction, and this failure occurs during high-speed traveling. Even if it occurs, safety is maintained.

The above is the case where a short circuit occurs inside the vehicle speed sensor 1, but the same operation occurs when the output signal line of the vehicle speed sensor 1 and the power supply are short-circuited.

The description of the characterizing portion of the present invention is completed above. Next, the operation of the disconnection detection circuit 6 will be described.

FIG. 5 (a) is a graph showing the change in vehicle speed at the time point t1.
The vehicle is traveling at a constant speed up to and is stopped at time t2. In this case, the output voltage of the voltage conversion circuit 2 changes as shown in FIG. 5 (b). Then, the disconnection detection circuit 6 sets the voltage of the inverting input terminal of the comparator 6h to a value larger than the voltage of the non-inverting input terminal, and also sets each constant so that the discharge time constant becomes larger on the inverting input terminal side. If set, the voltage at the non-inverting input terminal changes as shown in Fig. 5 (c) "a" and the voltage at the inverting input terminal changes as "b" with changes in vehicle speed. .

Therefore, the voltage "a" at the non-inverting input terminal does not exceed the voltage "b" at the inverting input terminal, and the output signal of the comparator 6h maintains the "0" level both during running and when stopped. .

On the other hand, if the vehicle speed sensor 1 is disconnected at the time point t1 shown in FIG. 6 (a), the vehicle speed signal will not be sent out, so the output voltage of the voltage conversion circuit 2 rises much more rapidly than the change state that occurs during normal traveling. Then, it changes as shown in FIG. At this time, the voltage of the non-inverting input terminal of the comparator 6h immediately follows as shown in "a" of FIG. 6 (b), but the voltage of the inverting input terminal has a large time constant, so that it is shown in "b". Ascends slowly. Therefore, the comparator 6h sends the output signal of "1" level at this time because the heavy pressure "a" at the non-inverting input terminal exceeds the voltage "b" at the inverting input terminal at the time t2. This signal is supplied to the control circuit 8 to turn on the transistor 8l, so that the relay 8j operates and the contact 8k of the relay 8j is switched. Therefore, the power supply to the solenoid drive circuit 4 is cut off, and the power supply voltage is supplied to the base of the transistor 8l via the resistor 8c, and this state is held.

Since the solenoid drive circuit 4 is cut off from the power supply, it does not generate a pulse signal, and as a result, the pulse signal is not supplied to the solenoid valve (not shown) connected to the terminals SOL1 and SOL2. Therefore, when a disconnection failure occurs in the vehicle speed sensor 1, the oil supplied from the solenoid valve to the power steering device decreases, so that the required steering force changes in an increasing direction, and this failure occurs during high-speed traveling. Even if it occurs, safety is maintained.

In the above embodiment, the oil flow rate was reduced to ensure safe driving. However, this value may be an intermediate flow rate. In this case, a large steering force is required when shifting to low speed running. Never be.

〔The invention's effect〕

As described above, the present invention uses the vehicle speed sensor that fixedly outputs the signal of "1" level when the vehicle speed sensor is short-circuited, and the output signal of the vehicle speed sensor continues to be "1" level. Since the short circuit of the vehicle speed sensor is determined by detecting the state, the detection can be performed by a simple circuit, which has the effect of improving reliability and economy.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram of a vehicle speed signal, and FIGS. 3 and 4 are waveform diagrams of respective parts for explaining the operation of a short circuit detection circuit of a vehicle speed sensor. FIGS. 5 and 6 are waveform charts for explaining the operation of the disconnection detection circuit of the vehicle speed sensor. 1 ... Vehicle speed sensor, 4 ... Solenoid drive circuit, 5 ...
Short circuit detection circuit, 6 ... Disconnection detection circuit, 7,8 ... Control circuit, 5a-5c, 6a-6d ... Resistor, 5d, 6g ... Diode, 5
f, 6e, 6f …… Capacitor, 5h, 6h …… Comparator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-205211 (JP, A) JP-A-57-160878 (JP, A) JP-A-53-106157 (JP, A) JP-A-56- 54359 (JP, A) JP 57-178971 (JP, A) JP 59-48264 (JP, A) Actually opened 59-114369 (JP, U) Actually opened 61-10561 (JP, U)

Claims (1)

[Claims] 1. A control device for a power steering system, which controls a oil flow rate by driving a solenoid based on a vehicle speed signal, wherein vehicle speed signals of "1" level and "0" level are repeatedly generated during running. A vehicle speed sensor that continuously generates a vehicle speed signal of “1” level when a circuit is short-circuited, a vehicle speed sensor short-circuit detection circuit that detects that the vehicle speed signal is in a state of continuing the “1” level, and a vehicle speed signal A vehicle speed sensor disconnection detection circuit that detects that the vehicle speed sensor is disconnected when the change state becomes more rapid than the change state that occurs during normal traveling, and the output of the vehicle speed sensor short circuit detection circuit or the vehicle speed sensor disconnection detection circuit And a control circuit for stopping the drive of the solenoid according to the present invention.