JPH0674051B2 - Steering force control device for power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention provides a power steering apparatus which is provided with a reaction force mechanism to allow a driver to sense an optimum steering force according to various driving states such as a traveling speed of a vehicle. The present invention relates to a steering force control device.

<Prior Art> Generally, a power steering apparatus including a reaction force mechanism requires a fluid supply source for supplying a pressure fluid to a reaction force chamber of the reaction force mechanism.

Conventionally, as the fluid supply source, a dedicated pump is provided, or a part of the passage is branched on the supply passage side for supplying the steering device pump to the servo valve to control this fluid for reaction force control. It also acts on the reaction chamber via the throttle valve.

<Problems to be Solved by the Invention> In the above conventional technique, the former requires a dedicated pump, which requires a space for arranging the pump and increases the cost.

The latter does not require a dedicated pump, but on the other hand,
Since the steering pressure does not rise unless the servo valve is steered, in the above branching system, pressure is not generated in the reaction force chamber in the neutral state of the servo valve, and necessary control cannot be performed. To this end, a switching valve may be interposed between the servo valve and the throttle valve for reaction force control to hydraulically separate the two, but the addition of a switching valve complicates the structure accordingly. It also causes a cost increase.

The present invention has been made in order to solve such a conventional problem, and uses the discharge hydraulic pressure of a servo valve for reaction force control, and enables optimum steering force control with a device having a simple structure and low cost. .

<Means for Solving Problems> According to the present invention, the discharge passage from the servo valve to the tank is communicated with the reaction force chamber of the reaction force mechanism, and the discharge passage from the discharge port of the servo valve to the tank is connected to the vehicle speed. An electromagnetic throttle valve that is controlled according to the above, and a variable throttle valve that is controlled by using the hydraulic pressure supplied to the supply port of the servo valve as a signal pressure are arranged, and the variable throttle valve is supplied to the variable throttle valve signal line at low speed. A switching valve is provided to prevent introduction of hydraulic pressure.

<Operation> At a low speed, the present invention makes the electromagnetic throttle valve wide open and closes the switching valve to widen the variable throttle valve to widen the pressure in the discharge passage of the servo valve to reduce the reaction force of the reaction mechanism. Set to practically 0 to lighten the handle operation.

Further, at high speed, the electromagnetic throttle valve is throttled according to the vehicle speed to increase the back pressure in the discharge passage of the servo valve, and the back pressure on the discharge side acts a reaction force mechanism to enhance the steering force. Further, when the handle is operated at high speed, the variable throttle valve is controlled according to the supply hydraulic pressure (gear generated pressure) introduced through the switching valve, and the hydraulic reaction force is controlled according to the gear generated pressure.

<Example> An example of the present invention will be described below with reference to the drawings. In FIG. 1, 11 is a housing main body which is a main body of the power steering apparatus, and 12 is a valve housing fixed to the housing main body 11. These housing body 11 and valve housing 12
Through a pair of bearings 13 and 14 to the pinion shaft 21 (output shaft)
Is rotatably supported, and the rack teeth 22 of the rack shaft 22 slidable in the direction intersecting with the pinion shaft 21.
a is in mesh. The rack shaft 22 is connected to a piston of a power cylinder (not shown), and both ends of the rack shaft 22 are connected to steering wheels via a required steering link mechanism.

A servo valve 30 is housed in the hole of the valve housing 12. The servo valve 30 mainly comprises a rotary valve member 31 integrally formed with the input shaft 23 as a steering shaft, and a sleeve valve member 32 concentrically and relatively rotatably fitted to the outer periphery of the rotary valve member 31. I am trying. The rotary valve member 31 is
It is flexibly connected to the pinion shaft 21 via a torsion bar 24 which is integrally connected to an input shaft 23 which is integral with this and the other end thereof is connected to the pinion shaft 21.

Further, on the outer periphery of the rotary valve member 31, a plurality of lands extending in the axial direction and grooves are formed at equal intervals as is well known, and similarly, on the inner periphery of the sleeve valve member 32, the axial direction thereof is also formed. A plurality of lands extending in the direction and grooves are formed at equal intervals. Then, when the servo valve is in the neutral state, the pressure fluid supplied from the pump to the supply port 35 is evenly distributed to the grooves on both sides of the land portion, and the discharge fluid is the communication passage between the steering shaft 23 and the torsion bar 24. 25, the communication passage 39 formed in the steering shaft 24, the low pressure chamber 38, and the discharge port 36, and the fuel is discharged to the tank T. In this case, the power cylinders are not operated because both distribution ports 33, 34 have low pressure and equal pressure.

When the servo valve is displaced from the neutral state, pressure fluid is supplied from one groove portion to the power cylinder via the distribution port 33, and the fluid discharged from the power cylinder flows into the other groove portion from the distribution port 34, Furthermore, the communication passage
25, 39, the low pressure chamber 38, and the discharge port 36 are discharged to the tank T.

A reaction force mechanism 50 is provided between the rotary valve member 31 and the pinion shaft 21. This reaction mechanism 50 is a movable piston
51 and the ball 52 as the main constituent members, this movable piston
The reference numeral 51 is slidably fitted in the inner hole of the pinion shaft 21 and is fitted by being rotated by a projection 53.
Is formed. The fluid pressure of the low pressure chamber 38 is introduced into the reaction force chamber 54 through the clearance of the bearing 59 and the communication passages 25 and 39, and the movable piston 51 is operated by this fluid pressure. Further, the balls 52 are inserted between the movable piston 51 and the flange portion 59 of the input shaft 23, and the holes 51 formed in the movable piston 51 as shown in FIG.
a and a V groove 59a formed in the flange 59. This contact pressure fluctuates according to the fluid pressure acting on the movable piston 51, and an appropriate operation reaction force is applied when the input shaft 23 is steered.

The structure of the hydraulic system for the servo valve 30 is as follows.
Reference numeral 61 is a flow rate control valve for controlling the flow rate Q ₀ of the discharge pressure oil from the supply pump driven by the automobile engine to a constant flow rate. This flow control valve 61 has a metering orifice 62
And a bypass valve 64 that is operated according to the front-rear pressure of the metering orifice 62 and controls the opening of the bypass passage 63 that communicates with the low-pressure side so as to always maintain the front-rear pressure constant. The flow rate control valve 61 is not necessary when the supply pump discharges a constant flow rate of a constant speed motor drive type.

Discharge pressure oil from the supply pump whose constant flow rate is controlled by the metering orifice 62 is supplied to the servo valve by the supply passage 45.
It is supplied to 30 supply ports 35.

46 is a discharge passage leading from the discharge port 36 of the servo valve 30 to the tank T. An electromagnetic throttle valve 80 that is controlled according to the vehicle speed and a variable throttle valve 90 that is controlled by using a hydraulic pressure supplied through the supply passage 45 as a signal pressure are provided in the discharge passage 46, and a line 47 of the signal pressure is provided. Is a configuration in which a switching valve 91 that is switched by the discharge hydraulic pressure of the discharge passage 46 is provided.

As shown in FIG. 3, the electromagnetic throttle valve 80 is a variable throttle valve 90.
Side of the throttle hole 83, a valve rod 81 for controlling the opening of the throttle hole 83, and a solenoid 82 for moving the valve rod 81 back and forth in the axial direction.The solenoid 82 has a current value corresponding to the vehicle speed. Is supplied to reduce the area of the throttle hole 83 due to the increase in vehicle speed. The switching valve 91 may be an electromagnetic switching valve that is switched based on the signal from the vehicle speed sensor.

Next, the control of the steering force in the power steering system having the above configuration will be described. When the vehicle is running, a vehicle speed signal is input from the vehicle speed sensor to the solenoid 82 of the electromagnetic throttle valve 80, and a current having a magnitude corresponding to this signal is applied.

At low speeds, the current applied to the solenoid 82 is small, and therefore the aperture 81 is wide open. Therefore, the pressure in the discharge passage 46 is maintained at a low pressure, the switching valve 91 is closed, and the variable throttle valve 90 is also wide open. Therefore,
Since the hydraulic pressure discharged from the discharge port 36 flows without resistance to the tank T, the reaction hydraulic pressure introduced into the reaction chamber 54 is low, and when the handle is operated, the reaction force by the reaction mechanism 50 does not act and the power is reduced. You can operate the handle lightly with the power assist of the cylinder.

When the vehicle speed shifts to a high speed exceeding a predetermined value, a change in the vehicle speed is detected by the vehicle speed sensor, the current applied to the solenoid 82 increases, and the valve rod 81 narrows the opening of the throttle hole 83. As a result, the pressure in the discharge passage 46 rises and this pressure is introduced into the reaction force chamber 54, so that the back pressure (reaction force hydraulic pressure) on the discharge side of the servo valve 30 increases as shown in FIG. , The reaction force action of the reaction force mechanism is enhanced, and the pressing force by the movable piston 51 and the ball 52 is increased. Therefore, a force for restricting relative rotation is applied between the pinion shaft 21 and the rotary valve member 31 in accordance with the vehicle speed, which makes the operation of the steering wheel heavy. Further, when the pressure in the discharge passage 46 rises, the switching valve 91 is switched to introduce the signal pressure from the supply passage 45 into the variable throttle valve 90. Therefore, when the pressure in the supply passage 45 rises by the handle operation in that state, The variable throttle valve 90 operates according to the pressure to throttle the opening, and controls the hydraulic pressure discharged from the electromagnetic throttle valve 80 to the tank T. Therefore, the steering force in this case is controlled by the variable throttle valve 90, which is controlled by the pressure generated by the gear as shown by the curve of medium speed and high speed in FIG. The inclination of is greatly changed to clarify the feeling of feeling when the handle is cut.

Although the current applied to the solenoid 82 is controlled only by the vehicle speed signal in the above embodiment, the control current is controlled in consideration of a plurality of conditions such as the steering angle signal and the steering angular velocity signal in addition to the vehicle speed signal. Good.

Further, in the above embodiment, the movable piston that moves the reaction force in the axial direction is used, but the present invention is not limited to this,
The reaction force may be applied by a plunger that slides in the radial direction.

<Effects of the Invention> As described above, according to the present invention, the discharge passage from the servo valve to the tank is communicated with the reaction force chamber of the reaction mechanism, and the vehicle speed input signal is input to the discharge passage from the discharge port of the servo valve to the tank. The electromagnetic throttle valve that controls the discharge fluid according to the above, and the variable throttle valve that is controlled by the gear generation pressure are arranged, so the gradient of the gear generation pressure (steering pressure) -manual torque characteristics at high speed You can change it greatly, and you can clearly feel the feeling when you cut the handle. In addition, a pump dedicated to the reaction force mechanism is not required, which is advantageous in terms of space and has an effect of reducing cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a power steering apparatus according to the present invention with a hydraulic system diagram, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a sectional view of essential parts of an electromagnetic throttle valve. FIG. 4 is a curve diagram showing a back pressure generation state depending on vehicle speed, and FIG. 5 is a curve diagram of steering characteristics. 25 ... communication passage, 30 ... low pressure chamber, 31 ... rotary valve member, 32 ... sleeve valve member, 38 ... low pressure chamber, 50 ... reaction mechanism, 54 ... reaction chamber, 80 ... electromagnetic Throttle valve, 90 …… Variable throttle valve, 91 …… Switching valve.

Claims (1)

[Claims] 1. A servo valve for distributing and controlling pressure fluid from a pump to a power cylinder by relative rotation of a pair of valve members, and a reaction force for introducing a pressure fluid into a reaction force chamber to give a steering reaction force to an input shaft. In a power steering apparatus having a mechanism, a discharge passage from the servo valve to the tank is communicated with a reaction force chamber of the reaction mechanism, and a discharge passage from the discharge port of the servo valve to the tank is provided according to a vehicle speed. The electromagnetic throttle valve to be controlled and the variable throttle valve controlled by using the hydraulic pressure supplied to the supply port of the servo valve as a signal pressure are arranged, and the hydraulic pressure to be supplied to the variable throttle valve at a low speed in the signal pressure line of the variable throttle valve. A steering force control device for a power steering device, which is provided with a switching valve that prevents the introduction of the engine.