JPS62139755A - Steering force control device for power steering apparatus - Google Patents

Abstract

PURPOSE:To always obtain an optimum steering characteristic, by detecting the pressure of a passage communicating between a pump device and a servo- valve for controlling the supply of hydraulic oil into a power cylinder, and by changing the pressure given by a reaction force mechanism in accordance with thus detected pressure value. CONSTITUTION:In a steering force control device, a steering force is applied to an input shaft 23 so that pressure fluid is fed into a power cylinder from a supply pump 30 through a distribution hole 40 when a servo-valve 30 is displaced from its neutral position to apply a steering assist force to a rack shaft 22. Further, there is provided a reaction force mechanism in which a plunger 54 urged inward in the radial direction by the pressure in a pressure chamber 56 is engaged to one end part of a rotary valve member 31 in the servo-valve 30. In this arrangement, a reaction force regulating device (pressure control valve) 70 is connected to a reaction force control passage 68 which leads fluid distributed by a flow dividing control valve 65 into the pressure chamber 56, and is controlled by a reaction force control device 100 in accordance with the outputs of a vehicle speed sensor 105 and a pressure sensor 83.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a servo valve that is operated based on a manual steering torque applied to a steering handle and controls the supply of pressure oil from a pump to a power cylinder, and a steering resistance. The present invention relates to a power steering device equipped with a reaction force mechanism that changes the force.

<Prior Art> In general, in this type of control device, it is necessary to lower the hydraulic pressure applied to the reaction force mechanism when running at low speeds, which requires steering pressure, and to increase it at high speeds, when little steering pressure is required.

Conventionally, the hydraulic pressure applied to this reaction force mechanism is controlled by an electromagnetic pressure control valve based on signals such as vehicle speed, regardless of the manual torque acting on the steering wheel. The resulting manual torque-gear generated pressure characteristics are shown in Figure 6, and the characteristics during high-speed driving only shift in parallel to the characteristics during low-speed driving, as shown by the two-dot chain line, and the characteristics during high-speed driving are shown in Figure 6. The slope of the characteristic cannot be changed. Therefore, there is a problem in that even if the steering wheel is turned in a state where the reaction oil pressure is high, the steering force does not change much. A preferable characteristic is a characteristic with a large slope as shown by the solid line during high-speed running in FIG.

In order to obtain such characteristics, the passage connecting the pump and servo valve and the passage leading to the reaction force chamber are communicated via a restrictor, and at high speeds, the pressure in the pump discharge side passage when the steering wheel is turned is reduced. A method has been proposed in which the reaction force increases as the vehicle ascends. According to this method, the characteristics shown by the solid line in FIG. 6 can be obtained at high speeds.

<Problems to be Solved by the Invention> However, in such conventional valves, the rate of increase in reaction force against the pressure increase in the pump discharge side passage due to handle operation is higher than that in the servo valve example passage and the reaction force chamber side passage. There was a problem in that ideal control characteristics could not be obtained because the characteristics were determined by the characteristics of the communicating shear diaphragm.

Means for Solving the Problems> The present invention provides a reaction force adjustment device that changes the steering resistance applied by a reaction force mechanism in accordance with an electrical command signal, and a pressure adjustment device that changes the pressure in a passage communicating between a pump and a servo valve. A pressure detection device that detects and outputs an electric signal according to the detected pressure, and a control means that changes the magnitude of a command signal given to the reaction force adjustment device in response to a change in the output of the pressure detection device. It is characterized by the fact that it has been provided.

When the servo valve is activated by the handle operation and the pressure in the pump discharge side passage increases, this is detected by the pressure detection device, and the control means sends a command signal to the reaction force adjustment device according to the amount of increase in pressure. change the magnitude of and change the reaction force. The ratio of the amount of increase in reaction force to the pressure increase in the pump discharge side passage is optimally set by the control means according to driving conditions such as vehicle speed. Thereby, ideal control characteristics can be obtained.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 11 indicates a housing main body forming the main body of the power steering device, and reference numeral 12 indicates a valve housing fixed to the housing main body 11. A pinion shaft (output shaft) 21 is rotatably supported within the housing body 11 and the valve housing 12 via a pair of bearings 13 and 14.
A rack m 22 a of a rack shaft 22 that is slidable in a direction crossing the pinion shaft 21 is meshed with the pinion shaft 21 .

This rank shaft 22 is connected to a piston of a power cylinder (not shown), and both ends thereof are connected to steering wheels via a required steering link mechanism.

A servo valve 3o is housed in the hole of the valve housing 12. The servo valve 30 has a rotary valve member 31 integrally formed with an input shaft 23 as a steering shaft, and a sleeve valve member 32 fitted to the outer circumference of the rotary valve member 31 concentrically and rotatably relative to each other as main components. There is. The low-return valve member 31 is flexibly connected to the pinion shaft 21 via a torsion bar 24 whose one end is connected to an input shaft 23 integral therewith.

Further, as is well known, a plurality of lands and grooves extending in the axial direction are formed at equal intervals on the outer circumference of the rotary valve member 31, and similarly, on the inner circumference of the sleeve valve member 32, a plurality of lands and grooves extending in the axial direction are formed. A plurality of lands and grooves extending in the direction are formed at equal intervals. Therefore, if the servo valve 30 is in the neutral state, the pressure fluid supplied from the supply port 35 flows evenly into the grooves on both sides of the land portion, and then flows through the communication path 37 and the low pressure chamber 3.
8 and exits via passage 39 to discharge port 36 . In this case, the power cylinders are not activated because the redistribution ports 40, 41 are at low and equal pressure.

However, when the servo valve 30 is displaced from the neutral state, the distribution action of the servo valve 30 supplies pressure fluid to the power cylinder through one distribution hole 40, and fluid discharged from the power cylinder is supplied to the other distribution port. 41 to the exhaust port 3 via the communication passage 37, three passages, and the low pressure chamber 38.
It is designed to be released on the 6th.

Further, a reaction force mechanism having the following configuration is incorporated within the valve housing 12. That is, as shown in FIG. 2, a protrusion 50 that protrudes on both sides in the radial direction is formed at the end of the rotary valve member 31.
The protrusion 50 is attached to the pinion shaft 21 corresponding to the input shaft 23.
A fitting groove 51 is formed into which the fitting groove 51 is loosely fitted so as to be rotatable through several angles around the axis. A tapered engagement groove 52 is formed on the outer circumferential surface of the protrusion 50, and an insertion groove 52 is formed in the pinion shaft 21 at a position corresponding to the engagement groove 52, into which the plunger 54 is slidably inserted in the radial direction. A hole 53 is formed.

A reaction force chamber 56 into which fluid pressure is introduced through an annular groove 55 is formed at the rear of the plunger 54, and the plunger 54 is caused by the fluid pressure introduced into this reaction force chamber 56.
is pressed against the engagement groove 52.

In addition, 58 is a port for introducing fluid for reaction force control, and 57
is a passage that communicates the port 58 and the annular groove 55.

The reaction force mechanism configured as described above is a so-called radial type in which the plunger is slid in the radial direction, but it may also be a thrust type in which the plunger is slid in the axial direction to apply a reaction force.

Reference numeral 60 indicates a supply pump driven by an automobile engine, and a discharge port of this supply pump 60 is connected to a flow control valve 6.
1 and the supply port 35 via a branch control valve 65. The flow rate control valve 61 is operated according to a metering orifice 62 provided in a passage 45 that connects the discharge port of the supply pump 60 and the diversion control valve 65, and the pressures before and after this metering orifice 62. A bypass valve 64 controls the opening of the bypass passage 63 so as to keep the differential pressure of It is bypassed to the reservoir via the passage.

The diversion control valve 65 controls the constant flow NQ of the working fluid to a servo valve passage 67 and a reaction force control passage 68 by a control spool 65a that operates according to the differential pressure before and after the fixed throttle 66.
A constant flow rate Q1 and Q2 are distributed to each of them. The servo valve passage 67 is connected to the supply boat 35, and the reaction force control passage 68 is connected to the port 58 for the reaction force mechanism. Further, a pressure control valve 70 constituting a reaction force adjustment device is connected to a passage 68 communicating with the introduction port 58.

As shown in FIG. 3, the pressure control valve 70 includes a valve body 72 fixed to a housing 71, a solenoid 73 attached to the valve body 72, and a movable spool 74 that is displaced when the solenoid is energized. a valve seat member 76 forming a relief passage 75 communicating with the passage 68;
It is composed of a pawl valve 77 that opens and closes the relief passage 75 of the valve seat member 76, and a relief pressure setting spring 78 and a balance spring 79 inserted between the pawl valve 77 and the movable spool 74. ing. The movable spool 74 is normally held in the state shown in the figure by the balance of springs 78 and 79, and the spring load of the spring 78 for setting the relief pressure is set to the maximum. However, as the movable spool 74 is displaced to the right against the balance spring 79 due to the suction action of the solenoid 73, the spring load of the spring 78 is reduced.

Further, the passage 60a connecting the supply pump 60 and the flow rate control valve 61 is communicated with the reservoir via a branch passage 82 in which a pair of throttles 80.81 are interposed in series. A pressure sensor 83 is connected between 81 and 81 .

In FIG. 1, 100 is a reaction force control device that controls the opening and closing of the pressure control valve 70 to control the hydraulic reaction force generated in the reaction force chamber 56 of the reaction force mechanism. This reaction force control device 100 includes a microprocessor 101, a ROM 102, and a RAM 103.
This microprocessor 101 is connected to the pressure control valve 70 via a solenoid drive circuit 104. Further, a vehicle speed sensor 105 is connected to the microprocessor 101, and the traveling speed of the vehicle is detected based on an output signal from the vehicle speed sensor 105.The output of the pressure sensor 83 is also connected to the pressure sensor 83. Based on the output of the supply pump 60, the discharge pressure of the supply pump 60 is detected. Note that the pressure sensor 83
The output of is the engine control circuit 1 that controls the rotation of the engine.
10 is also supplied.

The ROM 102 stores data necessary to obtain a control pattern as shown in FIG. 4(a) in the form of a map. This control pattern diagram shows the relationship between the magnitude of the discharge pressure P of the supply pump 60 and the magnitude of the reaction force to be applied, and the magnitude of the current supplied to the pressure control valve 70 is inversely proportional to the reaction force to be applied. There is a relationship between In addition, in this embodiment, the speed range of the vehicle is divided into three: low, medium, and high speed.
It is designed to perform control appropriate to the driving speed.

That is, in a low speed range where the vehicle is in a stationary state or a state close to this, there is almost no need to apply a reaction force, and there is no need to increase the reaction force in response to an increase in the manual torque acting on the steering wheel. Therefore, a map in which the current value is maintained at a constant high value regardless of the increase in the discharge pressure P is stored as the control pattern (2). On the other hand, in the medium speed range, the control map uses a control map that slightly increases the reaction force and smoothly decreases the current value as the detected pressure increases, in order to gradually increase the reaction force as the manual torque increases. It is stored as ■.

Further, a control map is stored as pattern (2) in which the reaction force is generally larger in the high speed range than in the medium speed range, and the rate of increase in the reaction force with respect to an increase in the steering torque is increased.

Furthermore, a control program shown in FIG. 5 is stored in the ROM 102, and the microprocessor 101 executes this program at regular intervals. When this program is executed, the output of the vehicle speed sensor 105 and the output of the pressure sensor 83 are read (200), and a map corresponding to the control pattern according to the speed range is selected (20).
1). Then, based on the selected map, a current value corresponding to the discharge pressure of the supply pump 60 detected by the pressure sensor 83 is derived (202), and this is supplied to the solenoid drive circuit 104 (203).

Next, the overall operation of the above device will be explained.

The pressure fluid discharged from the supply pump 60 flows through the flow control valve 6
1, the flow is controlled to a predetermined flow rate by the flow control valve 65, and one of the flows is supplied to the supply boat 35 of the power steering device.

At the same time, the excess flow discharged from the branch control valve 65 is
8 to the reaction force chamber 56. The fluid pressure of the fluid supplied to this reaction force chamber 56 is controlled by a pressure control valve 70.

On the other hand, the reaction force control device 100 outputs a control signal to the pressure control valve 70 in response to the output of the pressure sensor 83 and the output of the vehicle speed sensor 105. That is, as described above, the microprocessor 101 of the reaction force control device 100 executes the program shown in FIG. 5, determines the vehicle speed range based on the output of the vehicle speed sensor 105, and selects a control pattern according to the vehicle speed. do. Then, based on the selected control pattern,
Controls the supply of current to the pressure control valve 70.

For example, when the vehicle speed is low or low, the control pattern (■) is selected, so the servo valve 30 is activated by operating the steering wheel.
is activated, and the pressure in the passage 60a increases according to the manual torque, and even if the output of the pressure sensor 83 increases, the current supplied to the pressure control valve 70 remains at a high value. is maintained, and the reaction force does not increase.

Therefore, in such a low speed range, a smooth steering characteristic is achieved in which no reaction force acts.

On the other hand, when the vehicle speed is in the medium speed range, the control pattern (2) is selected, so the current supplied to the pressure control valve 70 is slightly reduced and the reaction force is increased.

Furthermore, as the pressure in the passage 60a increases as the steering wheel is operated, the current value supplied to the pressure control valve 70 also decreases, and as the steering torque increases, the reaction force increases, resulting in an appropriate steering feel. can get.

In addition, in the case of a high speed range, control pattern (3) is selected, so that the reaction force is further increased and the passage 60a
The amount of decrease in current with respect to the increase in pressure, that is, the amount of increase in reaction force, is increased, and a highly stable steering feeling can be obtained.

As described above, since the increase characteristic of the reaction force against an increase in the manual torque acting on the steering wheel can be freely changed according to the vehicle speed, an optimal steering feeling can be obtained according to the vehicle speed.

Note that since the discharge pressure of the supply pump 60 is divided into throttles 80 and 81 and the divided pressures are measured by the pressure sensor 83, it is possible to use a pressure sensor with low pressure resistance.

Note that when the output of the pressure sensor 83 changes due to handle operation, this is detected by the engine control device 110, and when the engine is in an idle state, the opening degree of the idle speed control valve 111 is changed to idle up the engine.

<Effects of the Invention> As described above, in the present invention, the pressure in the passage connecting the pump device and the servo valve is detected by a pressure sensor,
Since the pressure applied by the reaction force mechanism is changed based on the change in the output of the pressure sensor, the increase rate of the reaction force with respect to the increase in steering wheel torque can be set arbitrarily, and the advantage is that the optimum steering characteristics can be obtained. There is.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG. 1 is a sectional view of the power steering device of the present invention together with a control circuit diagram, and FIG.
The figure is a cross-sectional view taken along the line nn in Figure 1, Figure 3 is a cross-sectional view of the main part of the pressure control valve, Figure 4 (a) is a diagram showing changes in reaction force against pump discharge pressure, and Figure 4 (b) is a cross-sectional view of the main part of the pressure control valve. ) is a diagram showing changes in gear generation pressure with respect to manual torque, FIG. 5 is a flowchart showing a control program, and FIG. 6 is a characteristic diagram showing conventional characteristics and preferred characteristics. 21... Binion shaft, 23... Input shaft, 30...
Servo valve, 56...reaction force chamber, 6o...supply pump,
61...Flow control valve, 65...Diversion control valve, 70.
...Pressure control valve, 8o, 81...throttle, 83...pressure sensor, lo. ...Reaction force control device, 105...Vehicle speed sensor.

Claims (2)

[Claims] (1) In a power steering device equipped with a servo valve that is activated based on manual steering torque applied to a steering handle and controls the supply of pressure oil from a pump to a power cylinder, and a reaction force mechanism that changes steering resistance. , a reaction force adjustment device that changes the steering resistance applied by the reaction force mechanism according to an electrical command signal, and an electric signal that detects pressure in a passage connecting the pump and the servo valve and responds to the detected pressure. A power steering system comprising: a pressure detection device that outputs a pressure detection device; and a control means that changes the magnitude of a command signal given to the reaction force adjustment device in response to a change in the output of the pressure detection device. Steering force control device for the device. (2) The pressure detection device includes a pair of throttle bodies provided in a passage that communicates a portion of oil discharged from the pump to the tank side, and a pressure sensor that detects passage pressure between the pair of throttle bodies. A steering force control device for a power steering device according to claim (1), characterized in that it is constituted by: