JPH0624959B2 - 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 device, the hydraulic pressure discharged from the supply pump is reduced when the vehicle travels at a low speed requiring a steering pressure. The oil pressure applied to the reaction mechanism is increased during high-speed traveling, which requires almost no. However, conventionally, the pressure oil discharged from the plurality of discharge ports of the supply pump is collected in one flow passage to control it. Therefore, the pump internal pressure is considerably higher than the hydraulic reaction force chamber pressure of the reaction mechanism, and this pump internal pressure is applied to the total flow rate discharged by the pump itself.
There was a problem that the pump consumed horsepower was large.

The present invention is intended to suppress an increase in pump internal pressure and reduce pump consumption horsepower.

<Means for Solving Problems> The present invention is directed to 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 handle torque depending on a vehicle speed. In a steering force control device for a power steering system having a reaction force mechanism that changes the discharge force, a plurality of discharge ports of a supply pump are divided into two, one discharge port is connected to the servo valve side, and the other discharge port is A switching valve that is switched based on the vehicle speed is connected to the servo valve side at a low speed and to the reaction force chamber side of the reaction force mechanism at a high speed, and the pressure on the reaction force chamber side is controlled according to the vehicle speed. It has a solenoid valve.

<Operation> In the present invention, during low-speed traveling in which the oil pressure applied to the reaction force mechanism is reduced, the switching valve is turned off so that the pressure oil guided to the reaction force mechanism joins the supply line to the servo valve, and the reaction force mechanism is During high-speed traveling that requires oil pressure to be applied to the servo valve, the switching valve is turned on so that the servo valve is not covered with the pressure oil from one discharge port of the supply pump, and the pressure oil from the other discharge port of the supply pump is While being guided to the force mechanism, the pressure oil guided to the reaction mechanism is controlled by a solenoid valve according to the vehicle speed.

<Embodiment> An embodiment 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 26a so as to be relatively rotatable by a predetermined amount.

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.

50 is a pressure balance type supply pump driven by an engine. The supply pump 50 divides the plurality of discharge ports into two parts, that is, a first discharge port 51a and a second discharge port 51b. This first discharge port 51a is the supply port 2 of the servo valve 20.
It is connected to 6 by aisle 45. A flow control valve 80 is provided in the passage 45. This flow control valve 80 is
The flow rate control is constituted by a metering orifice 81 and a bypass valve 82 which is operated according to the front-rear pressure of the metering orifice 81 and which controls the opening of a bypass passage 83 communicating with the low-pressure side so as to always keep the front-rear pressure constant. valve
A constant flow rate required for the power steering apparatus is supplied to the supply port 26 by 80, and the surplus flow is discharged from the bypass passage 83 to the low pressure side.

The second discharge port 51b of the supply pump 50 is an electromagnetic switching valve 52.
Is connected to the passage 46 connected to the introduction port 40 communicating with the reaction force chamber of the reaction force mechanism. Also, this switching valve
The passage 52 is connected by a passage 47 to the upstream side of the flow control valve 80 in the passage 45 that connects the first discharge port 51a, the servo valve 20, and the supply port 26. The switching valve 52 is switched based on the signal from the vehicle speed sensor, but may be a switching valve switched according to the governor pressure of the torque converter, which changes depending on the vehicle speed, the shift signal of the change lever, or the like.

Further, the passage 46 connected to the introduction port 40 is provided with an electromagnetic relief valve 60 for controlling the pressure in the reaction force chamber of the reaction force mechanism according to the vehicle speed or the like. This solenoid relief valve 60
As shown in FIG. 2, is a valve body 62 fixed to the housing 61, and a solenoid 63 attached to the valve body 62.
A movable spool 64 that is displaced by energizing the solenoid 63, a valve seat member 66 that forms a relief passage 65 that communicates with the introduction port 40, and a ball valve that opens and closes the relief passage 65 of the valve seat member 66. 67, and a relief pressure setting spring 68 and a balance spring 69 that are interposed between the ball valve 67 and the movable spool 64. The movable spool 64 is a normal spring 68,
The balance of 69 holds the state shown in the figure, and the spring load of the relief pressure setting spring 68 is set to the maximum.
However, the spring load of the spring 68 is reduced as the movable spool 64 is displaced rightward against the balancing spring 69 by the suction action of the solenoid 63. The solenoid 63 has a vehicle speed signal V from a solenoid drive circuit 71 controlled by a computer 70.
Is supplied, and the control pressure (relief pressure) PC changes in accordance with this current value.

Next, the operation of the above configuration will be described. The flow rate of the pressure oil discharged from the first discharge port 51a and the second discharge port 51b of the supply pump 50 is distributed in half, and the first discharge port 51a is directed to the servo valve 20 side and the second discharge port is also discharged. Port 51b
Is supplied to the reaction mechanism side.

During low-speed traveling, the switching valve 52 is located in the OFF state as shown in the figure, and the pressure oil from the second discharge port 51b is introduced into the passage 45 on the servo valve 20 side via the passage 47, and the reaction force of the reaction force mechanism. Not introduced into the room. Therefore, the flow rate on the servo valve 20 side is as shown in FIG. 3A, the first discharge port 51a and the second discharge port 5a.
Both flow rates are 1b and 1b, and in a region where the engine speed is low, the flow rate control valve 80 controls the flow rate to a predetermined constant flow rate required for the power steering apparatus and supplies the same to the supply port 26 of the servo valve 20. Therefore, the reaction force piston 35 is pressed against the engagement ball 36 only by the repulsive force of the web washer 39, and when the steering shaft 24 is rotated by the steering wheel operation, the reaction force piston 35 resists the repulsive force of the web washer 39. Easily retracted, whereby the sleeve valve member 21 and the rotor valve member 22 are relatively rotated,
Normal power steering action is performed.

When the vehicle speed exceeds a predetermined value, the switching valve 52 is turned on, and the pressure oil from the second discharge port 51b is switched so as to be introduced into the passage 46 leading to the reaction force chamber of the reaction force mechanism, and then to the servo valve 20 side. Is only the pressure oil from the first discharge port 51a and is reduced as shown in FIG. 3B. However, at high speeds, the engine speed is also high, and therefore the flow rate required for the power steering apparatus is secured only by the pressure oil from the first discharge port 51a. On the other hand, the second discharge port 51 guided from the passage 46 to the reaction chamber.
The pressure oil from b is controlled by the electromagnetic relief valve 60 that is controlled according to the vehicle speed, and the control pressure PC is increased according to the increase of the vehicle speed, and the reaction force hydraulic pressure is increased according to the vehicle speed as shown in FIG. . As a result, the reaction force piston 35 is pressed against the engagement ball 36 by the axial thrust force corresponding to the reaction force hydraulic pressure, and the sleeve valve member 21
The manual torque for rotating the rotor valve member 22 and the rotor valve member 22 relative to each other is increased. Since the flow rate of the pressure oil from the second discharge port 51b increases in proportion to the increase of the vehicle speed (engine speed), the flow rate control for controlling the flow rate between the switching valve 52 and the electromagnetic relief valve 60 constant. A valve may be provided, and in this case, instead of the electromagnetic relief valve 60, the same pressure control can be performed by providing an electromagnetic flow control valve that changes the throttle area of the variable throttle according to the supplied current value. . Further, the electromagnetic relief valve 60
The control may be performed by the steering wheel rotation angle, the steering wheel rotation speed, or the like in addition to the vehicle speed.

As for the reaction force mechanism, the side where the reaction force piston 35 is moved in the axial direction of the servo valve 20 has been described, but even if the reaction force piston is a radial type that moves the reaction force piston in the radial direction of the servo valve, similar steering force Control is gained.

<Effects of the Invention> As described above, according to the present invention, the plurality of discharge ports of the supply pump are divided into two, one discharge port is always on the servo valve side, and the other discharge port is a switching valve that is switched based on the vehicle speed. At low speeds, the servo valve side is connected, and at high speeds, the reaction force chamber side is connected to the reaction force chamber side. The pressure oil can be supplied only to the pump, and the flow rate required for power assist can be secured with a pump with a relatively small capacity. Since the pressure oil is supplied to the chamber side, the increase in the pump internal pressure due to the reaction hydraulic pressure only affects the flow rate discharged from one of the discharge ports, which has the effect of reducing the pump consumption horsepower.

[Brief description of drawings]

FIG. 1 is a sectional view of a power steering apparatus showing an embodiment of the present invention with a hydraulic system diagram combined, FIG. 2 is a sectional view of a main portion of a solenoid valve, and FIG. 3 is an engine speed (vehicle speed). FIG. 4 is a diagram showing the flow rate of pressure oil to the servo valve, and FIG. 4 is a diagram showing reaction force hydraulic pressure based on vehicle speed and the like. 11 …… Output shaft, 20 …… Servo valve, 24 …… Input shaft, 33 ……
Reaction force cylinder chamber, 35 ... Reaction force piston, 50 ... Supply pump, 51a ... First discharge port, 51b ... Second discharge port,
52 …… Switching valve, 60 …… Solenoid valve, 80 …… Flow control 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 device, a plurality of discharge ports of a supply pump are divided into two, one discharge port is connected to the servo valve side, and the other discharge port is a switching valve that is switched based on a vehicle speed. An electromagnetic valve is provided, which is switched and connected to the servo valve side at a low speed and to the reaction force chamber side of the reaction force mechanism at a high speed, and which controls the pressure on the reaction force chamber side according to the vehicle speed. Steering force control device for power steering device.