JPH0749272B2 - Power steering control device - Google Patents

Description

TECHNICAL FIELD 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.

[Conventional technology]

Conventionally, the power steering apparatus includes a vehicle speed sensor that generates a vehicle speed signal according to the vehicle speed, and a control circuit that controls the oil flow rate based on the vehicle speed signal generated by the vehicle speed sensor,
The control is such that the oil flow rate decreases as the vehicle speed increases. That is, the oil flow rate is increased at a low speed where a large steering force is required, and the oil flow rate is decreased at a high speed where the steering force is small, and
Steering can be performed with an appropriate steering force. In this case, the oil flow rate is controlled by inserting an electromagnetic valve into the oil passage and decreasing the output current value supplied to the electromagnetic valve as the vehicle speed increases, as shown in FIG. The oil flow rate is reduced by narrowing with increasing vehicle speed.

[Problems to be solved by the invention]

However, in such a conventional control device,
As shown in FIG. 9, the output current supplied to the electromagnetic valve changes in a one-to-one correspondence with changes in the vehicle speed, so that only uniform changes in the vehicle speed / steering force characteristics are possible. Atsuta Further, the vehicle speed-steering force characteristic is fixed to a predetermined characteristic, and it is difficult to meet the driver's preference.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and includes a vehicle speed sensor that generates a vehicle speed signal corresponding to a vehicle speed, and a voltage conversion circuit that converts the vehicle speed signal generated by the vehicle speed sensor into a DC voltage corresponding to the signal. And a smoothing amplification circuit that smoothes and amplifies the DC voltage from the voltage conversion circuit, and in the control device of the power steering apparatus that controls the oil flow rate to decrease as the vehicle speed increases, the voltage conversion circuit and the smoothing amplification circuit The circuit constants of the circuit are simultaneously switched, the conversion characteristic of the voltage conversion circuit and the amplification characteristic of the smoothing amplification circuit are simultaneously changed, and the control characteristic of the oil flow rate is switched by the combination of both characteristics.

[Action]

Therefore, according to the present invention, if, for example, a characteristic changeover switch is provided as the characteristic changeover means, by operating this characteristic changeover switch, the circuit constants of the voltage conversion circuit and the smoothing amplification circuit are simultaneously changed over to perform the voltage conversion. The conversion characteristics of the circuit and the amplification characteristics of the smoothing amplifier circuit are changed at the same time, and switching of the circuit constants of the voltage conversion circuit cannot do this, and switching of the circuit constants of the smoothing amplifier circuit cannot do it. It is possible to switch to the desired oil flow rate control characteristic.

〔Example〕

Hereinafter, the control device of the power steering apparatus according to the present invention will be described in detail.

First, before starting the description of the present invention, the technology underlying the present invention will be described with reference to the basic example shown in FIG. This basic example is the technology on which the present invention is based,
It is not an example of the present invention. The circuit shown in FIG. 7, which is a modification of this basic example, is an embodiment of the present invention. The circuit of FIG. 7 will be described later.

In FIG. 1, 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 this vehicle speed signal into a DC voltage corresponding to the signal, and 3 is smoothing amplification. Circuit, 4 is solenoid drive circuit, 5
Is a first abnormality detection circuit for detecting a short circuit with the power source of the vehicle speed sensor 1, 6 is a solenoid valve (not shown) connected between the ground of the vehicle speed sensor 1 and the output terminals SOL1 and SOL2 of the solenoid drive circuit 4. A second abnormality detecting circuit for detecting an excessive current flowing through the solenoid, 7 is a third abnormality detecting circuit for detecting the disconnection of the solenoid valve, and 8 is an abnormality detected in the first to third abnormality detecting circuits 5-7. It is a solenoid drive stop circuit that shuts off the power supply to the solenoid drive circuit 4 when

The voltage conversion circuit 2 includes resistors 2a to 2g, capacitors 2h to 2k, diodes 2l to 2n, and transistors 2p and 2q. The vehicle speed signal input via the output terminal 1a of the vehicle speed sensor 1 is in a high speed state. As a result, a DC voltage is generated which decreases in voltage. The base of the transistor 2q is connected to the characteristic switching switch 9, and when the characteristic switching switch 9 is turned on, the transistor 2q is turned off.

The smoothing amplifier circuit 3 is composed of resistors 3a to 3f, capacitors 3g and 3h, a thermistor 3i, and an operational amplifier (hereinafter referred to as an operational amplifier) 3j. I'm running. The solenoid drive circuit 4 includes resistors 4a to 4p, capacitors 4q to 4t, and diodes 4u.
_{1 to} 4u ₆ , a comparator 4v, and transistors 4w and 4x, and generates a pulse signal having a smaller duty ratio as the supplied input signal becomes smaller. The first abnormality detection circuit 5 includes resistors 5a, 5c to 5e, a capacitor 5f,
It is composed of 5g, a diode 5h, and a comparator 5i. The second abnormality detection circuit 6 includes resistors 6a and 5b and a capacitor 6
It is composed of b to 6e, a diode 6f, and a comparator 6g. The third abnormality detection circuit 7 is composed of resistors 7a to 7f, capacitors 7g to 7i, diodes 7j and 7k, and a comparator 7l. Solenoid drive stop circuit 8 has resistors 8a-8
g, capacitors 8h-8j, transistor 8k, diode 8
l, varistor 8m, relay 8n, relay 8n contact 8p.

The solenoid valve connected between the output terminals SOL1 and SOL2 of the solenoid drive circuit 4 has a larger opening degree as the duty ratio of the current flowing therethrough increases.
A structure is used that acts to increase the oil flow rate. Also, when no current is supplied thereto, the oil supply to the power steering device is reduced.
Incidentally, 10 is an abnormality warning lamp.

Next, the operation of the circuit thus configured will be described. When the vehicle starts traveling, 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. Then, this DC voltage is smoothed and amplified by the smoothing 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 becomes smaller as the vehicle speed increases, and the solenoid drive circuit 4 generates a pulse signal having a smaller duty ratio as the input signal becomes smaller. That is, the current value supplied to the solenoid valve decreases as the vehicle speed increases, and 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.

By the way, in general, the output voltage of an operational amplifier has a dead zone with respect to the power supply voltage. FIG. 2 shows the input / output characteristics of the operational amplifier 3j. The horizontal axis shows the input voltage in FIG., The vertical axis represents the output voltage, the output voltage is a predetermined voltage than the supply voltage Vcc input voltage is supplied to the operational amplifier V ₁ of the operational amplifier 3j
It changes linearly from the moment it descends. That is, the input voltage Vcc to Vcc-V ₁ is the output voltage is constant. In this basic example, the connection point A in the voltage conversion circuit 2 is set to the same potential as the power supply potential of the operational amplifier, and the dead zone of the operational amplifier 3j is positively used. By doing so, the vehicle speed-output voltage characteristic of the operational amplifier 3j becomes as shown in FIG. That is, the output voltage becomes constant until the vehicle speed reaches the predetermined vehicle speed v ₁ , and after the predetermined vehicle speed v ₁ , the output voltage decreases as the vehicle speed increases. By this,
The output current supplied to the solenoid valve via the solenoid drive circuit 4 has the same characteristic as shown in FIG. 4, and the oil flow rate supplied to the power steering device is constant until the predetermined vehicle speed v ₁ is reached, and the predetermined vehicle speed v After reaching ₁ , it decreases as the vehicle speed increases. In this embodiment, this predetermined vehicle speed v _{1 is set} to 10
It was set to ~ 15Km / h. This allows the steering wheel to be operated with a minimum steering force from when the vehicle starts to run until it reaches 10 to 15 km / h, and after reaching 10 to 15 km / h, the steering force varies depending on the vehicle speed. It is adjusted as before.

This vehicle speed v ₁ can be arbitrarily set by appropriately selecting the circuit constant of the voltage conversion circuit 2, and the characteristic switching switch 9
Is turned on, the transistor 2q is turned off, and the resistor 2e is connected in parallel with the resistor 2d. By switching to a circuit state, the vehicle speed-output voltage characteristic of the voltage conversion circuit 2 is Vcc as shown by the dotted line in FIG. It becomes a gentle slope with the fulcrum as the fulcrum. Therefore, the dead vehicle speed blunt in the operational amplifier 3j spreads, and the output current supplied to the solenoid valve reaches a vehicle speed v ₂ larger than the vehicle speed v _{1 as} shown by the dotted line in FIG. The virtual output current value Icc corresponding to Vcc starts to decrease as a virtual fulcrum. In other words, by switching the characteristic switching switch 9 from the off state to the on state or from the on state to the off state, the voltage conversion circuit 2
The circuit constant in Fig. 2 changes, and the control characteristic of the oil flow rate supplied to the power steering apparatus can be switched according to the preference of the driving vehicle, the driving state, and the like. In this basic example, the characteristic switching switch 9 is connected between the base of the transistor 2q and the ground.
However, it may be connected between the base and the power supply potential.

FIG. 7 is a circuit diagram showing an embodiment of the present invention, which is based on the above-mentioned basic example and which is further improved.

In this circuit, a relay 11 is connected to the characteristic changeover switch 9 whose one end is connected to the power supply voltage, the first normally open contact 11 _a1 of this relay 11 is connected in series to the resistor 2e, and this normally open contact 11 _a1 is connected. The circuit constant in the voltage conversion circuit 2 is switched by turning on and off. In this case, the reverse current blocking diode 2n of the voltage conversion circuit 2 in FIG. 1 can be omitted.

In addition, in this circuit, relay to the resistor 3e of the smoothing amplifier circuit 3.
By connecting the resistor 12 in parallel via the second normally open contact 11 _a2 of 11, the circuit constant of the voltage conversion circuit 2 is switched and the circuit constant of the smoothing amplification circuit 3 is switched at the same time. . In this case, the amplification factor of the operational amplifier 3j changes by switching the circuit constant of the smoothing amplification circuit 3.

That is, when the characteristic switching switch 9 is turned on, the normally open contacts 11a ₁ and 11a _{2 of the} relay 11 are closed, and the solenoid valve is supplied only by closing the normally open contact 11a ₁ . The vehicle speed-output current characteristic (dotted line in FIG. 8)
By changing the amplification factor of the operational amplifier 3j, the value of the virtual output current value Icc decreases as shown by the solid line in FIG. 8, and the inclination also becomes gentle with the predetermined point P as the fulcrum. Therefore, the dead vehicle speed range in the operational amplifier 3j becomes small,
The output current supplied to the solenoid valve has a characteristic that it gradually decreases from the time when the vehicle speed reaches v ₃ . The predetermined point P can be determined by a feedback resistor that determines the amplification factor of the operational amplifier 3j, and can be set arbitrarily. That is, by simultaneously switching the circuit constants of the voltage conversion circuit 2 and the amplification circuit 3 by turning on / off the characteristic switching switch 9, it is not possible to switch only the circuit constants of the voltage conversion circuit 2, and the circuit of the smoothing amplification circuit 3 is also possible. It becomes possible to switch to the oil flow rate control characteristic that the driver prefers, which cannot be achieved only by switching the constant.

In addition, in order to change the circuit constant, normally open contacts 11a ₁ , 1 of relay 11 are
Although 1a ₂ is used, it goes without saying that the normally closed contact of the relay 11 may be used.

The above is the operation of the characteristic part of the present invention. The abnormality detection circuits 5 to 7 for fail-safe in this control circuit
The operation of is briefly explained. That is, when the vehicle speed sensor 1 is short-circuited with respect to the power supply during traveling, the output of the comparator 5i becomes "H" level. As a result, the transistor 8k of the solenoid drive stop circuit 8 is turned on, the relay 8n operates, and the contact 8p of the relay 8n switches. By this switching operation, the power supplied to the solenoid drive circuit 4 is cut off, and the transistor 8 is connected via the resistor 8d.
The power supply voltage is supplied to the 8k base and this state is held. At the same time, the power supply voltage is also supplied to the abnormality warning lamp 10 and the lamp lights.

On the other hand, the solenoid drive circuit 4 does not generate a pulse signal because the power supply is cut off, so that no current is supplied to the solenoid valves connected to the output terminals SOL1 and SOL2. For this reason, the amount of oil supplied from the solenoid valve to the power steering device decreases, so that the necessary steering force changes in an increasing direction, and safety is maintained even if this abnormality occurs during high-speed traveling.

Similarly, when an abnormality is detected in the abnormality detection circuits 6 and 7, the outputs of the comparators 6g and 7l are set to the “H” level, the relay 8n operates, and the safety during traveling is maintained.

〔The invention's effect〕

As described above, according to the control device for a power steering apparatus of the present invention, if a characteristic changeover switch is provided as the characteristic changeover means, for example, by operating this characteristic changeover switch, the voltage conversion circuit and the smoothing amplification circuit can be operated. The circuit constants of the voltage conversion circuit and the amplification characteristic of the smoothing amplification circuit are changed at the same time by switching the circuit constants of, and the circuit constants of the smoothing amplification circuit cannot be achieved only by switching the circuit constants of the voltage conversion circuit. It is possible to switch to the oil flow rate control characteristic that is preferred by the driver, which cannot be achieved only by switching the above, and it is possible to obtain the vehicle speed-steering force characteristic that meets the driver's request with a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic example of a control device of a power steering system for explaining the technology on which the present invention is based, FIG. 2 is an input / output voltage characteristic diagram of an operational amplifier used in this device, and FIG. Fig. 4 is a characteristic diagram of a vehicle speed / output voltage of this operational amplifier, Fig. 4 is a characteristic diagram of a vehicle speed / output current supplied to a solenoid valve, Fig. 5 is a characteristic diagram of a vehicle speed / output voltage of a voltage conversion circuit, and Fig. 6 is a voltage conversion circuit. Showing changes in the vehicle speed-output current characteristics supplied to the solenoid valve when the circuit constant of FIG. 7 is changed, and FIG. 7 is a circuit diagram showing an embodiment of the control device for the power steering apparatus according to the present invention. The figure shows the change in the vehicle speed-output current characteristic supplied to the solenoid valve when the circuit constant of the amplifier circuit of this control device is changed, and FIG. 9 is the vehicle speed supplied to the solenoid valve using the conventional control device. It is one output current characteristic view. 1 ...... vehicle speed sensor, 2 ...... voltage conversion circuit, 3 ...... smoothing amplifier circuit, 3j ...... operational amplifier, 4 ...... solenoid drive circuit, 9 ...... characteristic changeover switch, 11 ...... relay, 11a _1, 11a
₂ ... Normally open contact.

Claims (1)

[Claims] 1. A vehicle speed sensor for generating a vehicle speed signal according to a vehicle speed, a voltage conversion circuit for converting a vehicle speed signal generated by the vehicle speed sensor into a DC voltage according to the signal, and a DC voltage from the voltage conversion circuit. In a control device for a power steering system, which includes a smoothing amplification circuit that smoothes and amplifies, the control unit that controls the oil flow rate to decrease as the vehicle speed increases, the circuit constants of the voltage conversion circuit and the smoothing amplification circuit are simultaneously switched. And a characteristic switching means for changing the conversion characteristic of the voltage conversion circuit and the amplification characteristic of the smoothing amplification circuit at the same time, and switching the control characteristic of the oil flow rate by a combination of both characteristics. Control device for steering device.