JPS59143767A - Power steering device - Google Patents

Abstract

PURPOSE:To prevent the shortage of assist even in a sudden steering by reducing the discharge by a PS pump as the speed of a car is increased and controlling it to be increased as the rotational speed of a steering wheel is increased. CONSTITUTION:A discharge control valve 19 is provided on the way of a pipe 15 to supply the fluid generated by a PS pump 14 driven by an engine 18 to a PS-operation cylinder 11. The discharge control valve 19 is controlled by a controller 30 to reduce the discharge as the car speed is increased and increase the discharge as the steering speed of a handle is made greater and more sudden on the basis of signal from a car speed sensor 22. This construction permits to obtain a speed-sensing type PS without causing the shortage of assist of PS when a handle is suddenly operated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device for a vehicle, and more particularly to a vehicle speed-sensitive power steering device that changes steering assist force in accordance with the traveling speed of the vehicle.

A power steering device that uses hydraulic means to assist the driver's steering force generates a large steering assist force when driving at low speeds (including when stopped), where steering resistance is large, significantly reducing the driver's burden and improving the vehicle's performance. As the running speed of the vehicle increases and the steering resistance decreases, it is desirable that the steering assist force be gradually reduced so that the steering does not become too light.

In conventional power steering devices, pressurized oil is supplied to a power cylinder that assists the steering force by an oil pump directly connected to the engine. In conventional power steering systems equipped with such oil pumps that are directly connected to the engine, a control valve is installed in the hydraulic system to the power cylinder to limit the amount of pressurized oil supplied to the power cylinder, or to limit the amount of pressure oil supplied to the power cylinder at high speeds. The above-mentioned adverse effects are prevented by controlling the amount to a minimum. For example, in Japanese Patent Publication No. 54-18810, in the flow path that communicates the oil pump and the power cylinder,
A power steering system is equipped with a control valve that controls the flow rate according to the vehicle speed using a centrifugal governor, etc., and increases the flow rate at low speeds to reduce the steering force, and decreases the flow rate to increase the steering force at high speeds. Disclosed.

On the other hand, in a power steering device, when the steering speed at which the steering wheel is operated is high, it is necessary to supply a large amount of pressure oil to the power cylinder in a short period of time. Otherwise, the amount of pressure oil supplied will be insufficient and sufficient steering assist force will not be obtained. For this reason, simply controlling the amount of pressure oil supplied to the power cylinder according to the vehicle speed as described above is not enough.
If the pressure oil supply amount is set based on the normal steering speed, the pressure oil supply amount will be insufficient during sudden steering. Furthermore, if settings are made based on sudden steering, the above-mentioned shortage of pressure oil supply can be avoided, but there is also the problem of having to increase the oil cylinder capacity, and unnecessary pressure at normal steering speeds. Pressure oil supply is carried out, and there is a problem that pressure oil supply loss increases.Increasing the pump capacity increases the driving power accordingly, leading to a decrease in fuel efficiency. So it's not desirable.

In view of these circumstances, the present invention controls the amount of pressure oil supplied to the power cylinder according to the running speed of the vehicle to optimize the steering force, and also increases the amount of pressure oil supplied according to the steering speed during steering. An object of the present invention is to provide a power steering device that can prevent a flow shortage even during sudden steering.

The power steering device of the present invention includes a flow control pulp that controls the amount of pressure oil supplied in a pressure oil supply flow path from a pump driven by an engine to a power cylinder, and the operation of this flow control pulp is controlled from a controller. In a power steering device that is controlled by a control signal, this controller issues a control@1 signal to the flow control pulp to reduce the amount of pressure oil supplied as the running speed increases, and during steering, the pressure The present invention is characterized in that a control signal corrected to increase the amount of oil supplied is issued to the flow rate control pulp.

According to the present invention, the amount of pressure oil supplied to the power cylinder can be reduced as the vehicle speed increases, and the amount of pressure oil supplied can be increased during steering, so the amount of pressure oil supplied at low speeds can be set appropriately. Even if the pressure oil supply amount is reduced during medium and high speeds, there will be no shortage of assist force during steering. For this reason, at medium and high speeds, there is a demand to reduce the pressure oil supply I to make the steering heavier and to increase stability and responsiveness IJρ, and there is also a demand for sufficient pressure to respond to sudden steering at medium and high speeds. 2. The need to secure the amount of pressure oil supply
Two conflicting demands? We can satisfy each other.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram showing a power steering device according to an embodiment of the present invention. The power steering device of this embodiment is equipped with a rack and pinion type V-no steering as manual steering, and a steering shaft 2 rotated by a steering wheel 1 is connected to a pinion 5 via joints 3 and 4.

This pinion 5 is meshed with a rack 6, and this rack 60
At both ends, knuckle arms 8a, 8. are rotatably supported around shafts 7a, 7b. Tie rods 9a and 9b engaged with b are connected. steering wheel 1
is operated and 20 rotations of the steering shaft are transmitted to the rack width via the pinion 5, the rack 6 moves in the left and right directions in the figure, rotates the steering arms 8a and 8b via the tie rods 9a and 9b, and performs steering. Wheel (generally the front wheel)
Give the steering angle to 10a and 10b.

The power cylinder 11 repiston 11 is attached to the soil hook 6.
Pipes 12a and 12b, which are connected to oil chambers 11a and llb defined by this histone llc, are connected to an oil pump 14 via a control valve 13. The control valve 13 has been commonly used in this type of power steering device, and the control valve 13 connects the discharge pipe 15 and return pipe 16 of the oil pump 14 to pipes 12a and 12b, or 12b, respectively, depending on the steering direction. Switch the hydraulic system to connect to 12a and 12a. For example, when the rack 6 is steered to move to the right in the figure, the discharge pipe 15 is connected to the pipe 12b, and the return pipe 16 is connected to the pipe 12a. As a result, the rightward movement of the rack 6 is assisted by the hydraulic pressure within the power cylinder 11. Further, when the steering shaft 2 is not rotated, the control valve 13 is connected to the discharge pipe 1.
5 and the return pipe 16 are directly connected to each other, and the power cylinder 11
Do not send pressure oil to the

The oil pump 14 is connected to the engine 18 via a belt 17 etc.
In addition, the oil pump 14 has a built-in constant flow discharge mechanism, and when the engine rotation is above a predetermined value (for example, idle link rotation speed), a constant amount (for example, (yl /m1n) of pressure oil is discharged.Furthermore, a flow rate control valve 19 is interposed in the discharge pipe 15 at a position near the oil pump.This flow rate opening side 1 valve 19 is connected to the casing A valve body 19d is formed to be slidable in the vertical direction in the figure within the valve body 19g;
The casing 19g is composed of a spring 19e that urges the valve body 19d downward in the figure, and a solenoid 19f that causes a force to pull the valve body 19d upward when excited. s2 baud) 19
a, 19 b.

and a third boat 19Q connected to the return pipe 16.

When the solenoid 19f is demagnetized, the valve body 19d is
The third boat 19c is closed by the force of the spring 19e. At this time, the annular groove 19h formed around the circumference of the valve body 19d is connected to the first groove. 2nd boat 1'9 a, 19 b
lc is matched, and the first boat 19a and the second boat 19b are communicated with each other (the state shown in FIG. 1). - When the solenoid 19f is energized, the valve body 19d is pulled up against the biasing force of the spring 19e, and the solenoid 19f is energized.
, p The magnetic force of the solenoid is proportional to the energizing current (++, so the amount of movement by which the valve body 19d is pulled up is also proportional to the energizing direct current (i+). Therefore, the solenoid 19
With the excitation of f, the third bow (19c), which had been closed by the valve body 19d, opens the first and second boats (19a, 1).
9b, and its opening area is the solenoid 19f.
It increases in proportion to the amount of current applied to it. Therefore, a part of the oil discharged from the oil pump 14 flows into the return pipe 16 through the boat 19c, and the amount (q) of pressure oil supplied to the power cylinder 11 changes in accordance with the increase in the amount of energization to the solenoid 19f. It becomes less.

The amount of current supplied to the solenoid 19f is controlled by a control signal input to the controller 30 through the line 20e.
A signal from the steering speed sensor 23 is input through a line 20b, a signal from the changeover switch 24 through a line 20b, a signal from the vehicle speed sensor 22 through a line 20c, and a power input from the battery 21 through a line 20d.

The controller 30 outputs a control signal for the solenoid 19f based on the above input, and its operation will be explained in detail with reference to FIGS. 2, 3, and 4.

FIG. 2 is a circuit diagram of the controller 300, in which the vehicle speed signal detected by the vehicle speed sensor 22 is converted into a voltage signal by the fV converter 31 via the line 20c, and is sent to the (-+1 side) of the adder 32. On the other hand, the steering speed signal (i) detected by the steering speed sensor 23 is sent to the adder 3.
It is input to (-) 11Ilj of 2. In the adder 32, the steering speed signal is subtracted from the vehicle speed signal converted into a voltage signal, and then outputted to the voltage-current converter 33,
It is converted into a current proportional to the output voltage. This current acts as a base current of the transistor 34, and the amount of energization (1) of the solenoid 19f is also controlled in proportion to the base current.

Therefore, in this embodiment, when the steering speed is θ-0 (for example, when traveling straight), the output of the steering speed sensor 23 is zero, and the current (1) flowing through the solenoid 1 and 19r is
As shown by line A in the graph of the relationship between solenoid energizing current fi) and vehicle speed in FIG.
m/I-1), the relationship is set such that the current is constant. The flow rate control valve 19 shown in FIG. 1 operates according to this energizing current (1) to control the pressure oil supply ff1h+ to the power cylinder 11, so this pressure oil supply amount (
The relationship between q) and vehicle speed is shown by line A in Figure 4. At low speeds, the flow rate is high (at low speeds, the flow rate decreases as the speed increases, and when the vehicle speed exceeds a predetermined value (e.g. 80 km/r1), it remains constant). becomes the flow rate.

Next, when you operate the steering wheel, the steering speed θ
The steering speed signal that increases according to the magnitude of is added to the adder 3
Since the output of the na calculator 32 is inputted to the (-) side of 2, the energizing current (1) of the solenoid 19f also changes from the line A depending on the magnitude of the steering speed θ, as shown in FIG. B
.

Continuously changes (decreases) from C to D. Therefore, the amount of oil supplied to the power cylinder 11 (q) increases from line A to B, C, and D in accordance with the magnitude of the steering speed, as shown in FIG. In this way, the amount of pressure oil supplied to the power cylinder 11 can be controlled according to the vehicle speed and corrected according to the steering speed. Furthermore, as shown in FIG. 1, a signal from a changeover switch 24 is also input to the controller 30, and this changeover switch 24 emits a signal that changes the energizing current (i) of the solenoid 19f as a whole. So, lines A and B in Figure 3.

C, I) can be changed. That is, as the vehicle speed increases, the pressure oil supply amount can be decreased relatively suddenly or relatively slowly. For this reason, for example, the changeover switch 24 can be attached so that it can be operated by the driver, and the driver can increase the steering force at high speeds to increase stability and responsiveness, or reduce the steering force to make steering easier, depending on the driver's preference. You can do it like this.

In this embodiment, the flow rate control in the flow rate control pulp 19 is performed by controlling the opening area using a linear solenoid, but this is performed by controlling the tute ratio using an ON-01i'li' type solenoid. The same flow rate control as in this embodiment is possible.

As explained in detail above, according to the present invention, the amount of pressure oil supplied to the power cylinder is reduced as the vehicle speed increases, and during steering, the amount of pressure oil supplied is increased depending on the magnitude of the steering speed. Therefore, at low speeds or when stationary, the steering force can be reduced to improve steering response, and at high speeds, the steering force can be increased to increase stability. Even when the vehicle is in use, there is no lack of assist power, and the result is a car with excellent maneuverability and stability.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an electric circuit of the embodiment of the present invention, and FIG. 3 is a graph showing the relationship between solenoid current (i) and vehicle speed. and FIG. 4 is a graph showing the relationship between pressure oil supply amount (q) and vehicle speed.

Claims (1)

[Claims] a power cylinder that assists steering force; an oil pump that is driven by an engine and supplies pressure oil to the power cylinder; and a flow rate control pulp that controls the amount of pressure oil supplied from the oil pump to the power cylinder;
a vehicle speed sensor that detects the running speed of the vehicle; a steering sensor that detects the steering speed of the steering wheel; A power steering device comprising a controller that outputs a flow control signal to a flow control pulp and corrects the flow control signal so as to increase the pressure oil supply amount in accordance with an increase in steering speed based on the steering sensor kamo signal.