JPH0374288A - Reaction control device of power steering - Google Patents

Abstract

PURPOSE:To keep the feeling of operation satisfactory by connecting the discharge side of a pilot pump to the pilot chamber of a reaction pressure control valve, and communicating a spring chamber between a throttle provided in the connecting process with the tank and the tank. CONSTITUTION:In low speed running, the discharge quantity of e pilot pump PP is small, the differential pressure between the front and back of a throttle 27 is low, the pressure difference between a spring 23 and a pilot chamber 24 is not large, and the spool 22 of a reaction pressure control valve V keeps normal position by the action of a spring 26 to keep the communicating opening between both ports 18, 21. Thus, the reaction chamber 10 of a cylinder control valve 2 is communicated with the outflow port 21 at the maximum opening, and the pressure of the reaction chamber 10 is kept low to make the feeling of handle operation light. In middle and high running, the discharge quantity of the pilot pump PP is large, the differential pressure between the front and back of the throttle 27 is high, the differential pressure between the spring chamber 23 and the pilot chamber 24 is also increased, so that the spool 22 is moved to reduce the communicating opening between the both ports 18, 21, and the pressure of the reaction chamber 10 is increased to make the feeling of handle operation heavy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power steering reaction force control device in which a reaction force pressure control valve is of a hydraulic pilot type.

(Prior Art) The conventional device shown in FIG.
This is a power steering device according to No. 4,825. In this device, a counter bomb C is connected to a reaction force chamber of a controller @a. This anti-caponbu C is linked to a propeller shaft (not shown). Therefore, the discharge amount of this pump C depends on the vehicle speed.

The counterforce pump C and the counterforce chamber S are connected to a tank d, and an orifice e is provided in the passage therebetween. Therefore, as the traveling speed of the vehicle increases, the discharge amount of the anti-force pump C increases, but the pressure loss of the orifice e also increases in proportion to the discharge amount. As the pressure loss of the orifice e increases in this way, the pressure in the reaction force chamber increases accordingly. In other words, the pressure inside the reaction force chamber changes depending on the vehicle speed.

Applying pressure to the reaction force chamber in this way increases the initial reaction force according to the vehicle speed, but the control characteristics of a device that increases the initial reaction force in this way are shown in Figure 4. It is shown. As is clear from this control characteristic diagram, there was a problem in that the steering force near neutral became too large, resulting in poor feeling characteristics.

The device shown in FIG. 5 is known as a device that solves this problem.

In the device shown in FIG. 5, a cylinder control valve 2 is connected to a main passage l that connects a main pump P and a power cylinder (not shown). This cylinder control valve 2 is switched according to the steering direction of the steering wheel, and controls the operation of the back cylinder.

Further, this main pump P is connected to a reaction pressure control valve 4 via a branch passage 3;
The structure is as follows.

The valve body 5 of the reaction pressure control valve 4 is formed with an inflow port 6, an outflow port 7, and a tank port 8. The inflow port 6 is connected to the main pump P via the branch passage 3, the outflow boat 7 is connected to the reaction chamber 10 of the cylinder control valve 2, and the tank boat 8 is connected to the tank 11.

A spool 12 is provided in the valve body 5 as described above, and one end of this spool 12 has a proportional solenoid 1.
The bushing rod 14 of No. 3 is brought into contact with the bushing rod 14, and the spring 15 is brought into contact with the other end.

A controller 16 for controlling the excitation current is connected to the proportional solenoid 13, and a vehicle speed sensor 17 is connected to the controller 16. The controller 16 thus constructed has a control function that maximizes the excitation current to the proportional solenoid 13 when the vehicle is running at low speed, and decreases the excitation current as the vehicle speed increases.

Thus, when the vehicle is running at low speed, the excitation current to the solenoid 13 is at a maximum, keeping the spool 12 in the position shown. In this illustrated position,
Communication between the inflow port 6 and the outflow boat 7 is cut off, while the outflow boat 7 and the tank boat 8 are communicated with each other. In this state, the reaction force chamber 10 of the cylinder control valve 2 communicates with the tank 11, so the pressure within this reaction force chamber 10 also becomes the tank pressure. Therefore, the steering reaction force becomes the smallest, and the steering feel becomes lighter.

Further, when the vehicle is running at a medium to high speed, the exciting current of the proportional solenoid 13 becomes small, so the spool 12 moves rightward in the drawing by the spring force of the spring 15 in accordance with the current value. When the spool 12 moves to the right, the opening degree of the tank boat 8 becomes smaller and the inflow port 6 and the outflow boat 7 are brought into communication. At this time, the opening degree of the tank port and the degree of communication opening between the inflow port 6 and the outflow boat 7 are determined according to the amount of movement of the spool 12, that is, the exciting current to the solenoid 13. therefore,
When the excitation current becomes the minimum, the tank port 18 is completely closed and the degree of communication between the inflow port 6 and the outflow boat 7 is maximized.

When the inflow port 6 and the outflow boat 7 communicate with each other as described above, the discharge pressure of the main pump P acts on the reaction force chamber 10, increasing the steering reaction force.

In other words, this conventional device controls the excitation current of the proportional solenoid 13 according to the vehicle speed, and also controls the pressure in the reaction force chamber IO of the cylinder control valve 2 according to the excitation current.

Therefore, according to this control device, as shown in FIG. 6, the initial reaction force hardly changes and ideal control characteristics can be obtained.

(Problem to be Solved by the Invention) However, in the reaction force control device shown in FIG. 5, the proportional solenoid 13 is used to control the reaction pressure control valve 4, but this proportional solenoid l3 is extremely Since it is expensive, there is a problem in that the manufacturing cost is high.

In addition, as mentioned above, it uses an electric control method, so
For example, there is a problem in that the control mechanism malfunctions when there is radio interference.

An object of the present invention is to provide a power steering reaction force control device that does not change the initial reaction force and can control a reaction pressure control valve without using a proportional solenoid.

(Means for Solving the Problems) This invention connects a cylinder control valve to a passage process that supplies oil discharged from a main pump to a power cylinder, and provides a reaction force that controls the pressure in a reaction chamber of this control valve. This invention is based on a power steering reaction force control device that is provided with a pressure control valve and configured to control the steering reaction force in accordance with the pressure within the reaction force chamber.

Based on the above-mentioned device, the present invention provides a pilot pump in which one end of the spool of the reaction pressure control valve faces the spring chamber and the other end faces the pilot chamber, and the discharge amount is made variable according to the vehicle speed. At the same time, the discharge side of this pilot pump is connected to both the tank and the pilot chamber of the reaction pressure control valve, and a restriction is provided in the connection process between the pilot pump and the tank, and this restriction and The feature is that the spring chamber is communicated with the tank.

Note that the pilot pump may be linked to a speedometer drive device.

(Action of the present invention) Since the present invention is configured as described above, as the vehicle speed increases, the discharge amount of the pilot pump increases.

Therefore, the pressure difference between before and after the throttle provided in the connection process between the pilot pump and the tank becomes large. The pressure on the upstream side of this throttle acts on the reaction chamber of the reaction pressure control valve, so the pressure within this reaction chamber increases as the vehicle speed increases.

If the pressure within the reaction force chamber increases in this way, the steering feel will become heavier. This means that the steering wheel becomes lighter when driving at low speeds, and heavier when driving at higher speeds.

(Effects of the Present Invention) According to the power steering reaction force control device of the present invention, the initial reaction force can be kept substantially constant, so that the steering feeling can be maintained good.

Moreover, since there is no need to use a proportional solenoid like in the past, there is also the advantage of lower costs.

Further, since the device of the present invention employs a hydraulic control system, even if there is radio interference, the reaction force control device will not malfunction.

Furthermore, since the differential pressure before and after the throttle is applied to both ends of the spool, the operation of the spool is more stable than when pressure is applied only to the pilot chamber.

(Embodiment of the present invention) In the embodiment shown in Fig. 1.2, the main pump P and the cylinder control valve 2 are connected via the main passage 1 connected to the main pump P, and the cylinder control valve 2 is the same as the conventional one.

In this embodiment, a branch passage 3 branched from the main passage 1 is connected to an inflow boat 18 of the reaction pressure control valve (2), and a throttle 19 is provided in this branch passage 3. Further, the reaction force chamber 10 of the cylinder control valve 2 is connected to the downstream side of the throttle 19.

The reaction pressure control valve V has an inflow boat 18 and an outflow boat 21 formed in its valve body 20, and a spool 2
2 is installed inside. The spool 22 has one end facing the spring chamber 23 and the other end facing the pilot chamber 24.

A drain boat 25 is formed in the spring chamber 23, and a spring 26 is interposed therein so that the spool 22 normally maintains the normal position shown in the drawing. When the spool 22 is in the normal position shown, the degree of communication between the inflow boat 18 and the outflow boat 21 is maintained at the maximum.

Further, the pilot chamber 24 is connected to the tank T via the throttle 27.
This pilot chamber 24 and the aperture 27
A pilot pump PP is connected between the Further, a return passage 28 connected to the port 25 is connected to the connecting process between the throttle 27 and the tank T.

As shown in FIG. 2, the pilot pump PP is linked to an input valve 31 of a speedometer drive device 30 that drives the speedometer 29. This human power shaft 31 is linked to a transmission 33 linked to an engine 32. Therefore, the pilot pump PP increases its discharge amount in proportion to the traveling speed of the vehicle.

Note that the pilot pump PP is connected to the propeller shaft 34.
It is also possible to link the discharge amount to the vehicle speed, and the important thing is to make the discharge amount increase or decrease depending on the vehicle speed.

As the discharge amount of the pilot pump PP increases, the pressure difference before and after the throttle 27 increases, and accordingly, the pressure difference between the spring chamber 23 and the pilot chamber 24 increases. When the pressure difference between the two chambers 23, 24 increases in this way, the spool 22 moves against the spring 26, gradually reducing the degree of communication between the ports 18, 21.

Next, the operation of this embodiment will be explained.

When the vehicle is running at low speed, the amount of discharge from the pilot pump PP decreases. Therefore, the pressure difference before and after the throttle 27 becomes small, and the pressure difference between the spring 23 and the pilot chamber 24 does not become large. Therefore, the spool 22 of the reaction pressure control valve V maintains the normal position shown in the figure by the action of the spring 26, and maintains the communication opening of both boats 18, 21 to the maximum.

In this way, when the communication opening degree of both ports) 18 and 21 becomes maximum, the reaction force chamber lO of the cylinder control valve 2 and the reaction force pressure control valve ■
This results in communication with the outflow port 21 at the maximum opening degree.

Therefore, the pressure inside the reaction force chamber 101 2 is maintained at a low pressure, so that the steering wheel feels lighter when operated.

When the vehicle travels at medium to high speeds, the amount of discharge from the pilot pump PP increases accordingly. Therefore, the pressure difference before and after the throttle 27 also increases, and the pressure difference between the spring chamber 23 and the pilot chamber 24 increases. Therefore, the spool 22 of the reaction pressure control valve
and moves against the pressure action in the spring chamber 23, reducing the communication opening of both boats 18, 21.

If the degree of communication between the boats 18 and 21 is reduced in this way, the pressure within the reaction force chamber 10 will increase, which will make the steering feel heavier.

As described above, according to the power steering reaction force control device of this embodiment, the spool 22 of the reaction force pressure control valve (2) is controlled by the pressure of the pilot pump PP, so that the proportional pressure control valve 22 is controlled by the pressure of the pilot pump PP. This eliminates the need to use .

Further, since the differential pressure of the throttle 27 is applied to both ends of the spool 22, the operation of the spool 22 can be made stable.

It goes without saying that the reaction pressure control valve 4 shown in FIG. 2 as a conventional example may be used instead of the reaction pressure control valve V of this embodiment. In any case, the present invention is applicable to any structure in which the spool of a reaction pressure control valve is switched by the action of pilot pressure generated by a combination of a pilot pump and a throttle.

Further, the configuration of the cylinder control valve 2 is not particularly limited as long as it can control the power cylinder according to the switching direction of the handle.

[Brief explanation of drawings]

Drawings 1 and 2 show embodiments of this invention.
The figure is a circuit diagram showing only the reaction pressure control valve in a specific cross-sectional view, Figure 2 is an explanatory diagram showing the linkage mechanism between the pilot pump and transmission, and Figures 3 and 4 show the conventional device. Fig. 3 is a sectional view, Fig. 4 is a characteristic diagram showing its control characteristics, Fig. 5.6 shows another conventional example, and Fig. 345 shows a reaction pressure control valve. The circuit diagram shown in a specific sectional view, and FIG. 6 is a characteristic diagram showing its control characteristics. P... Main pump, 2... Cylinder control valve, lO
...Reaction force chamber, ■...Reaction force pressure control valve, 22... Sprue, 24... Pilot chamber, PP... Pilot pump, 27... Throttle, T... Tank, 30 ...
Speedometer drive device.

Claims (2)

[Claims] (1) Connect the cylinder control valve to the path that supplies oil discharged from the main pump to the power cylinder, and
In a power steering reaction force control device, a reaction force control valve for controlling the pressure in a reaction force chamber of the control valve is provided, and the steering feeling is controlled according to the pressure in the reaction force chamber. One end of the spool of the control valve faces the spring chamber and the other end faces the pilot chamber, and a pilot pump whose discharge amount is variable according to the vehicle speed is provided, and the discharge side of this pilot pump is located opposite to the tank. Connected to both the above pilot chamber of the pressure control valve, and
A restriction is installed in the connection process between the pilot pump and the tank,
A power steering reaction force control device characterized in that the spring chamber is communicated with the communication process between the throttle and the tank. (2) A power steering reaction force control device according to claim 1, in which a pilot pump is linked to a speedometer drive device.