JPH0624960B2 - Steering force control device for power steering device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering force control device for a power steering system including a reaction force mechanism that changes a steering wheel torque according to a vehicle speed.

<Prior Art> It is known that a control pressure proportional to a vehicle speed or the like is introduced into a reaction force mechanism to control the steering force of a power steering apparatus according to the vehicle speed or the like. In this type of device, the oil pressure introduced into the reaction force mechanism is controlled by using the pressure oil in the high pressure line connecting the power steering device and the supply pump.

<Problems to be Solved by the Invention> Generally, in this type of control device, the hydraulic pressure applied to the reaction mechanism is reduced during low-speed traveling requiring steering pressure, and conversely, high-speed traveling requiring little steering pressure. Sometimes it needs to be higher.

Conventionally, control of the hydraulic pressure applied to this reaction force mechanism is controlled by an electromagnetic pressure control valve based on a signal such as vehicle speed, regardless of the steering pressure. As shown in FIG. 5, the characteristics of the manual torque-gear generated pressure due to this are such that the characteristics at high speed traveling are only parallel to the characteristics at low speed traveling as indicated by the chain double-dashed line. The inclination cannot be changed freely. Therefore, there is a problem that the steering force does not change much even if the steering wheel is turned while the reaction force hydraulic pressure is high. Ideally, the characteristics should be such that the inclination is large as shown by the solid line during high speed running in FIG.

In view of the above-mentioned conventional problems, the present invention makes a change in steering force clear by setting a large inclination ideally for a manual torque-gear generated pressure characteristic during high-speed traveling.

<Means for Solving Problems> In order to solve the above problems, the present invention provides a supply passage connecting a supply pump and a servo valve of a power steering device,
The first variable throttle valve whose throttle area is enlarged and controlled in response to an increase in steering pressure and the second variable throttle valve whose throttle area is controlled to be reduced in response to an increase in vehicle speed are connected to the low pressure side, and The passage between the first variable throttle valve and the second variable throttle valve is connected to the reaction force chamber of the reaction force mechanism.

<Operation> In the present invention described above, the throttle area of the second variable throttle valve is large at low speeds, so that the hydraulic reaction force of the reaction force chamber is zero.
It becomes a light steering force.

On the other hand, at high speeds, the throttle area of the second variable throttle valve becomes small, which increases the hydraulic reaction force of the reaction force chamber, and since the throttle area of the first throttle valve is largely controlled by the steering pressure due to the steering wheel cut, The hydraulic reaction force in the force chamber increases in accordance with the steering pressure, and the manual torque increases with a large inclination characteristic.

<Examples> Examples of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 10 denotes a gear housing which is a main body of the power steering apparatus, and a pinion shaft (output shaft) 11 is rotatably supported by the gear housing 10, and the pinion shaft 11 intersects with the gear housing 10. It is meshed with a rack shaft 14 which can slide. Both ends of the rack shaft 14 are connected to steering wheels via a required steering link mechanism, and a piston of a power cylinder (not shown) is operatively connected to the rack shaft 14.

A valve housing 18 is fixed to the gear housing 10,
A rotary servo valve 20 is housed in the valve housing 18. The rotary servo valve 20 is a sleeve valve member capable of relative rotation about the axis of the pinion shaft 11.
21 and a rotor valve member 22.
Is integrally formed with a steering shaft (input shaft) 24 connected to the steering handle. The steering shaft 24 is flexibly connected to the pinion shaft 11 via a torsion bar 25, and has an engaging portion.
It is engaged via 43 via a predetermined amount so that relative rotation is possible.

A plurality of port grooves 21a, 22a are formed on the inner circumference of the sleeve valve member 21 and the outer circumference of the rotor valve member 22 at equal angular intervals on the circumference, and by relative rotation of the sleeve valve member 21 and the rotor valve member 22, The supply port 26 is connected to one of supply / discharge ports 28 and 29 connected to both chambers of the power cylinder, and the other is connected to the discharge port 27.

A cylindrical portion 30 that is rotatably fitted in the valve housing 18 is formed at one end of the pinion shaft 11.
One end of is connected to the sleeve valve member 21 via a connecting pin 31. A reaction force cylinder chamber 33 is formed concentrically with the pinion shaft 11 in the cylindrical portion 30.
A flange-shaped reaction force receiving portion 34 formed on the steering shaft 24 is relatively rotatably fitted therein. A ring-shaped reaction force piston 35 is fitted in the reaction force cylinder chamber 33 so as to face the reaction force receiving portion 34 so as to be slidable in the axial direction. It has been stopped against. The inner circumference of the reaction force piston 35 is fitted to the steering shaft 24, and the reaction force piston 35 divides the reaction force cylinder chamber 33 into a left chamber and a right chamber. Then, the left chamber is communicated with the introduction port 40 into which the reaction force hydraulic pressure is introduced as described later, and the right chamber is communicated with the drain port 41 connected to the reservoir. A plurality of conical recesses 34a, 35a are circumferentially formed on the opposing surfaces of the reaction force receiving portion 34 and the reaction force piston 35, and a plurality of circumferentially engaging balls are engaged with the recesses 34a, 35a. A retainer 37 for holding 36 and a retainer 37 are interposed between the reaction force receiving portion 34 and the reaction force piston 35. Thus, the reaction force piston 35 is constantly pressed by the web washer 39 provided on the back surface thereof in the direction in which the engagement ball 36 is engaged.

A metering orifice 52 controls a flow rate Q ₀ of pressure oil discharged from a supply pump driven by an engine to a predetermined flow rate Q ₁ required for power steering and reaction force control, and an excess flow is bypass passage 53 It is a flow control valve that discharges to a lower pressure side. This flow control valve 51 is not necessary in the case of a constant speed motor drive pump.

The supply passage 47 connecting the servo valve 20 of the power steering apparatus and the supply pump has a first variable throttle valve 60 controlled according to the steering pressure and a second variable throttle valve 80 controlled according to the vehicle speed and the like. Is connected to the low pressure side via a passage 45 between the variable throttle valves 60 and 80 and is connected to the introduction port 40 via a passage 46. As means for controlling the first variable throttle valve 60 according to the steering pressure, one end of the first variable throttle valve 60 is connected to the supply passage 47, and the variable throttle area S (P) of the variable throttle valve 60 is As shown in FIG. 3, control is performed so that the steering pressure increases as the steering pressure increases. In addition, the second variable throttle valve 80 controlled according to the vehicle speed and the like (handle rotation angle or handle rotation speed)
As shown in FIG. 2, is a throttle hole 83 leading to the low pressure side,
A valve rod 81 for controlling the opening degree of the throttle hole 83 and a solenoid 82 for moving the valve rod 81 back and forth in the axial direction are supplied with a current value according to the vehicle speed and the like. As a result, the variable aperture area S (I) is reduced as shown in FIG. The second variable throttle valve 80 may be an electromagnetic relief valve, or in the case where the flow rate supplied to the power steering device is changed according to the vehicle speed (engine speed), the change in the flow rate is used to change the flow rate before and after the fixed throttle. Variable throttle S (I) with differential pressure
It may be a hydraulic throttle valve for controlling.

Next, the operation of the above configuration will be described. In the case of the illustrated embodiment, the flow rate of the pressure oil discharged from the supply pump is controlled by the flow rate control valve 51 to a predetermined flow rate required for the power steering apparatus, and passes through the control valve 55 to the servo valve 20. It is supplied to the supply port 26. At the same time, the first variable throttle valve
It is also branched to 60, and is drained from the first variable throttle valve 60 via the second variable throttle valve 80. When the vehicle speed is low, the variable throttle area S (I) of the second variable throttle valve 80 has the fourth area.
The second variable throttle valve is held at the maximum as shown in the figure.
The drain resistance from 80 is reduced, and the hydraulic reaction force PR of the reaction force chamber of the reaction force mechanism is maintained at 0. Therefore, when the reaction force piston 35 is pressed against the engagement ball 36 only by the repulsive force of the web washer 39 and the steering shaft 24 is rotated by the steering wheel operation, the reaction force mechanism piston 35 is easy to resist the repulsive force of the web washer 39. The sleeve valve member 21 and the rotor valve member 22 are relatively rotated by this, and the manual torque has a normal light power steering action as shown by the solid line at low speed in FIG.

When the vehicle speed exceeds a predetermined value, the variable throttle area S (I) of the second variable throttle valve 80 is throttled as the vehicle speed increases, and the drain resistance from the second variable throttle valve 80 is increased. As the drain resistance of the second variable throttle valve 80 increases, the hydraulic reaction force PR rises, whereby the reaction force piston 35 is pressed against the engagement ball 36 by the axial thrust force corresponding to the hydraulic reaction force PR, and the sleeve. The manual torque for relatively rotating the valve member 21 and the rotor valve member 22 increases.

When the handle is operated in this state and the gear generation pressure rises, the first variable throttle valve increases in response to this gear generation pressure rise.
The aperture area S (P) of 60 is increased as shown in FIG. As a result, the flow rate branched to the second variable throttle valve 80 side via the first variable throttle valve 60 increases, and the discharge resistance of the second variable throttle valve 80 increases in accordance with the increase in this flow rate, and the hydraulic pressure PR
Is increased according to the increase in gear generation pressure. Note that the hydraulic pressure PR is, when the gear generation pressure is P ₁ , It is represented by.

Therefore, when the steering wheel is operated at a high speed, the characteristics are inclined as shown by the solid line in FIG. 5, and a feeling of steering feel is obtained.

Incidentally, the reaction force mechanism of the above embodiment is such that the reaction force piston 35 is a servo valve.
Although it is moved in the axial direction of 20, the same steering force control can be obtained by a radial method in which the reaction force piston is moved in the radial direction of the servo valve.

<Effects of the Invention> As described above, according to the present invention, the supply passage that connects the supply pump and the servo valve is provided with the first variable throttle valve whose throttle area is controlled to be enlarged according to the increase of the steering pressure and the increase of the vehicle speed. It is connected to the low pressure side through the second variable throttle valve whose throttle area is controlled to be reduced accordingly, and the reaction force chamber of the reaction force mechanism is connected between both variable throttle valves to provide a reaction force in relation to the throttle area of both variable throttle valves. Since the hydraulic pressure is controlled, the gradient of the gear generated pressure (steering pressure) -manual torque characteristics at high speed can be greatly changed, and the effect of clearly feeling the feel when the handle is cut is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a power steering apparatus showing an embodiment of the present invention with a hydraulic system diagram combined, FIG. 2 is a cross-sectional view of a variable throttle valve, and FIG. 3 is a gear of the first variable throttle valve. FIG. 4 is a diagram showing a change in the throttle area depending on the generated pressure, FIG. 4 is a diagram showing a change in the throttle area according to the vehicle speed of the second variable throttle valve, and FIG. 5 is a conventional and actual gear generated pressure-manual torque characteristic. It is the diagram which compared with invention. 11 …… Output shaft, 20 …… Servo valve, 24 …… Input shaft, 33 ……
Reaction force cylinder chamber, 35 …… Reaction force piston, 55 …… Control valve,
60 …… First variable throttle valve, 80 …… Second variable throttle valve.

Claims (1)

[Claims] 1. A servo valve which is operated based on relative rotation between an input shaft and an output shaft to control supply and discharge of pressure oil to and from a power cylinder, and a reaction force mechanism which changes a steering wheel torque according to a vehicle speed. In a steering force control device of a power steering apparatus, a supply passage connecting a supply pump and the servo valve is controlled to be expanded with a first variable throttle valve whose throttle area is controlled to be enlarged in response to an increase in steering pressure and an increase in vehicle speed. Is connected to the low pressure side via a second variable throttle valve whose throttle area is controlled to be reduced, and the passage between the first variable throttle valve and the second variable throttle valve is connected to the reaction force chamber of the reaction force mechanism. A steering force control device for a power steering device.