JPS6056671A - Control circuit for power steering device - Google Patents

Abstract

PURPOSE:To keep off a sudden variation in an oil flow rate for steering even if anything trouble happens in a power steering control circuit in time of high speed driving as well as to improve safety at the high-speed driving, by controlling an electric current according to a car speed and regulating the oil flow rate. CONSTITUTION:A solenoid valve 102 is provided with a coil 102a, a plunger 102b, an orifice 102c and a nonmagnetic material 102d, and the plunger 102b is forcibly pushed upward in time of the coil being nonconductive, narrowing the orifice in size, and oil out of a pump is designed so as to feed an outlet 102f at the steering side with its little amount. On the other hand, when the coil is energized with current, the plunger is attracted to the lower part, opening the orifice, whereby a large quantity of oil is fed to the outlet 102f. An electric current flowing into the solenoid valve 102 is designed so as to be large in a mean value in time of a car speed being low while to the small in the mean value in time of the car speed being high, so that if the car speed is large, a flow rate to be fed to the steering side comes small, therefore if anything trouble happens in time of high speed driving, a large variation in steering power will not occur because of smallness in oil quantity, thus safety comes high.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control circuit for a power steering device, and is designed to ensure operational safety even when the control circuit fails, especially during high-speed operation.

[Prior art]

In recent years, power steering devices have been widely used to perform light steering. This increases the oil flow rate at low speeds, where a large steering force is required, and reduces the oil flow rate at high speeds, where the steering force is small, allowing steering with a small steering force over a wide vehicle speed range. . in this case,
To control the oil flow rate, a solenoid valve is inserted into the oil passage, and as the vehicle speed increases, the value of the current supplied to the solenoid valve is increased so that the degree of opening of the solenoid valve becomes smaller. Ta.

However, with conventional devices like this, the control circuit that controls the solenoid valve breaks down at high speeds, and when the current supplied to the solenoid valve becomes zero, the oil flow reaches its maximum, resulting in a sudden loss of steering force. A small vehicle will result in a very dangerous driving situation.

To eliminate this drawback, it is possible to reduce the value of the current supplied to the solenoid valve as the vehicle speed increases, as shown in Figure 2, but with this configuration, the current supplied to the solenoid valve at high speeds Since the current becomes zero, it has a drawback that it is impossible to distinguish between a failure state in which current is no longer supplied to the electromagnetic valve and a normal operating state.

[Object and structure of the invention]

Therefore, an object of the present invention is to provide a control circuit for a power steering device that can ensure operational safety against a failure of the electromagnetic valve control circuit at high speeds, and can also distinguish between a failure state and a normal operating state. It is something to do.

In order to achieve this purpose, the circuit related to this circuit 1'(i) reduces the value of the current supplied to the electromagnetic valve as the vehicle speed increases, and reduces the value of the current supplied to the electromagnetic valve when the vehicle speed exceeds a predetermined value. The current value is kept constant.

Hereinafter, the present invention will be described in detail using drawings showing embodiments.

〔Example〕

FIG. 3 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is a waveform shaping circuit, 2 is an F-V conversion circuit, 3 is a smoothing circuit, 4 is a pulse conversion circuit, 5 is a power amplifier circuit, and 6
is a first failure detection circuit, T is a second failure detection circuit, 8 is a stop drive circuit, 100 is a vehicle speed sensor, 101 is a lamp,
102 is an electromagnetic valve, and 103 is a power input connector.

The waveform shaping circuit 1 includes resistors 11a to 119 and a capacitor 12.
8 to 12 operational amplifiers (hereinafter referred to as operational amplifiers) 1
3a and 13b, and includes a vehicle speed sensor 100.
Shapes the signal supplied from the converter into a pulse signal.

The F-V conversion circuit 2 includes a resistor 21 and a capacitor 22□~22
The diodes 23a to 23d are configured to send out a signal whose voltage value decreases as the number of pulses supplied increases, so as shown in Figure 4, if the vehicle speed increases. It sends out a signal whose voltage value decreases as the voltage increases. The Y-slip circuit 3 includes resistors 31 and -31 and capacitors 32a and 32b.

W4 is constructed from operational amplifier 33 and thermita 35, F-■
After smoothing the output signal of the conversion circuit 2, non-inverting amplification is performed and the output voltage is prevented from dropping below a predetermined value.As shown in FIG.
In this case, the output voltage decreases as the vehicle speed increases, and when the vehicle speed exceeds a predetermined value, a constant signal with a constant (direction) is output.
The pulse conversion circuit 4 includes resistors 41a to 41f and a capacitor 4.
It is composed of 2a, 42bx operational amplifiers 43, and Zener diodes 45 and 46, and when the value of the signal voltage supplied from the smoothing circuit 3 is large, a pulse with a large duty ratio is produced, and when the value of the signal voltage is small, a pulse with a small duty ratio is produced. It's starting to happen. The power amplifier circuit 5 has a resistor 5
1a-51e% Capacitor 52, diode 53a~
53d, Zener diode 54, transistor 55a
, ssb, a relay 56a, and a relay contact 56b. The first failure detection circuit 6 includes resistors 61a, 6
1b, capacitor 62. , 62b, and an operational amplifier 63, and is designed to detect disconnection of the coil of the vehicle speed sensor 100, continuous continuity to the electromagnetic valve 102, or an accident when this occurs. The second failure detection circuit 7 includes resistors 71a to 71f1 capacitors 72a + 72
1) b diode T3a #73b.

It is composed of an operational amplifier 74, and is designed to detect when a pulse signal is no longer supplied to the electromagnetic valve 102. The stop drive circuit 8 includes resistors 81a to 81c.
, capacitors 82a, 82b, and thyristor 83.

The operation of the circuit configured in this way is as follows. When the vehicle is running, the vehicle speed sensor 100 generates a pulse corresponding to the vehicle speed, and this pulse is transmitted to the waveform shaping circuit 1.
After the waveform is shaped by the F-V conversion circuit 2, it is converted into a signal having a voltage corresponding to the vehicle speed as shown in FIG. This signal is supplied to the non-inverting input terminal of the operational amplifier 33 via the resistors 31, 31b, so the operational amplifier 3
The output N pressure of No. 3 decreases as the vehicle speed increases, as shown in FIG. In this case, when the vehicle speed is VG, the operational amplifier 33
If a constant is set so that one output voltage of 1 is at the lowest potential, the output voltage of the operational amplifier 33 remains at the lowest potential even if the vehicle speed exceeds VO. In this case, so that the lowest value of the output xL pressure of the operational amplifier 33 becomes EO in FIG.
The values of the resistors 31d to 31g are set. Therefore, as shown in FIG. 5, the amplifier circuit 3 outputs a voltage that decreases as the vehicle speed increases when the vehicle speed Vot increases, and outputs a constant voltage regardless of the vehicle speed when the voltage is higher than the single series ■o. In addition, as a method of obtaining a certain voltage at high speed, there is also a method of connecting a resistor between the non-inverting input terminal of the operational amplifier 43 and the power supply.

Since a signal having the vehicle speed vs. voltage characteristic shown in FIG. When the vehicle speed is high, a pulse with a small duty ratio is supplied. For this reason, solenoid valve 1
The average value of the current flowing through 02 becomes smaller as the vehicle speed increases.

As shown in the sixth factor, the electromagnetic valve 102 has a coil 102.
It has a Bb plunger 102b, an orifice 102c, and a non-magnetic material 102d, and the plunger 102b is pressed upward when the coil 102a is not energized, and the orifice 10
2o is narrowed. For this reason, the oil supplied from the inlet 102e of the oil pump j is throttled by the orifice 102c and is supplied in a small amount to the outlet 102f on the power steering section side. However, coil 102. When a current is supplied to the plunger 102b, the plunger 102b is drawn downward and the orifice 102o is opened, so that a large amount of oil is supplied from the inlet 102e to the outlet 102f. At this time, coil 1
Since the average current supplied to the outlet 102a is large, the opening area of the orifice is large, and more oil is supplied to the outlet 102f.

Therefore, when the vehicle speed is low, a current with a large average value is supplied to the electromagnetic valve 102, and more oil is supplied to the power steering section, and when the vehicle speed is high, a current with a small average value is supplied. .

On the other hand, if the coil of the vehicle speed sensor 100 is disconnected, the resistance 11
When the voltage that was being supplied to the capacitor 12b via the capacitor 12b is no longer supplied, the operational amplifier 63 generates a signal at the "1" level. Further, when the wiring to the electromagnetic valve 102 is short-circuited or comes into direct contact with the power supply, an excessive current flows, and an abnormal voltage is generated in the resistor 41e. As a result, the voltage at the non-inverting input of the operational amplifier 63 increases, so the operational amplifier 63 still generates a signal at the rlJ level. As a result, the thyristor 83 of the stop drive circuit 8 is turned on and the relay 56 is driven, so that the power supplied to the control circuit is cut off at the relay contact 56b, and the lamp 101 lights up to warn of a malfunction. Do the following.

In this way, the first failure detection circuit 6 is connected to the vehicle speed sensor 100.
Even if the coil is disconnected, the sensor wiring is grounded, or the sensor wiring contacts the power supply, the operational amplifier 63 is connected via the resistor 61a, Zener diode 46, and resistor 61b.
A failure is detected because the voltage at the non-inverting input of the electromagnetic valve 102 increases, and a failure is also detected when the current flowing through the electromagnetic valve 102 becomes excessive.

If the pulse from the pulse conversion circuit 4 is turned on continuously due to another failure, the maximum current is supplied to the electromagnetic valve 102, and the supply of oil to the power steering device becomes maximum. At this time, since the signal from the operational amplifier 43 of the pulse conversion circuit 4 is no longer supplied to the operational amplifier 74 of the pulse drive detection circuit 7, the operational amplifier T4 generates a signal at the "1" level.

This turns on thyristor 83, so relay 56. is driven, and the power supplied to the control circuit is cut off by the relay contact 56a, and the lamp 101 is turned on to detect a failure. Note that the pulse drive detection circuit 7 can detect an abnormality regardless of whether the output from the pulse conversion circuit 4 is on or off.

As described above, the F-V conversion circuit 2 constitutes a means for reducing the oil flow rate as the vehicle speed increases, and the sliding circuit 3 constitutes a means for keeping the oil flow rate at a constant value when the vehicle speed is above a predetermined value. Therefore, the oil flow rate changes with respect to vehicle speed as shown in FIG. Therefore, even if an accident occurs in which current is not supplied to the electromagnetic valve 102 during high-speed driving at a predetermined vehicle speed of 70 or higher, there will be little change in the oil flow rate, so the change in steering force will be small. Since this is a change, driving safety will not be compromised. Solenoid valve 1 even when driving at high speed.
Since current is constantly supplied to 02, it is possible to distinguish between a normal operating state and a faulty state at high speeds.

〔Effect of the invention〕

As explained above, the control circuit of the power steering device according to the present invention reduces the average value of the current supplied to the electromagnetic valve as the vehicle speed increases up to a predetermined vehicle speed, and keeps the average value of the current constant at or above the predetermined vehicle speed. Therefore, even if a failure occurs in which current is not supplied to the solenoid valve at high speed, the steering force will change to a larger value, and the amount of change will be small, so it will not impair driving safety. This has the effect of being able to detect the occurrence of a failure even at high speeds.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the characteristics of the current supplied to the electromagnetic valve with respect to vehicle speed in a conventional circuit, and FIG. 2 is a graph showing the characteristics of the current supplied to the electromagnetic valve with respect to vehicle speed when the characteristics of FIG. 1 are improved. FIG. 3 is a circuit diagram showing one embodiment of the present invention, FIG. 4 is a graph showing the characteristics of the output voltage with respect to vehicle speed of the F-V conversion circuit shown in FIG. 3, and FIG.
A graph showing the output voltage versus vehicle speed of the smoothing circuit shown in the figure, Figure 6 is a cross-sectional view of the electromagnetic valve, and Figure 7 is 1. , i: is a graph showing the characteristics of oil flow rate with respect to vehicle speed of the electromagnetic valve controlled by this circuit. 1. Excellent - waveform shaping circuit, 2φ - - F-V conversion circuit,
3.--Smoothing circuit, 411.--Pulse conversion circuit, 5
...Power amplification circuit, 6,7-...Operational amplifier, 1oo--Vehicle speed sensor, 101 @--Lamp, 102--Solenoid valve. Patent Applicant Jidosha Kiki Co., Ltd. Agent Masaki Yamakawa (IBI 11 people) Figure 1 Figure 4 Figure 7 ■0*Return Figure 2 Figure 5

Claims (1)

[Claims] In a control circuit of a power steering device that controls the state of power steering by controlling the oil flow rate with a solenoid valve, means for reducing the average current supplied to the solenoid valve to reduce the oil flow rate as the vehicle speed increases; 1. A control circuit for a power steering device, comprising means for keeping the average value of the current supplied to the electromagnetic valve constant to keep the oil flow rate constant when the current exceeds a predetermined value.