JPH0232187B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device that uses hydraulic pressure to reduce the steering force of a vehicle, and more specifically, when the speed of the vehicle or engine increases to a certain extent, the movement of a control valve in response to the steering wheel operation is reduced. The present invention relates to a speed-sensitive power steering device that stops power assist by restraining the vehicle.

A power steering device, typified by a power steering device for an automobile, generally provides selective control to the output drive unit connected to the wheels (steering mechanism) via a control valve that switches based on the input rotation from the steering wheel. By supplying pressurized oil, the steering force is reduced.

By the way, as the running speed of the vehicle increases, the resistance force generated between the wheels and the road surface when operating the steering wheel becomes smaller, and the pump oil pressure has a property of increasing in proportion to the engine rotation speed. There was a problem in that the power assist force for steering wheel operation sometimes became excessive, impairing the steering stability of the steering wheel.

Therefore, for example, the present applicant proposed in Japanese Patent Application No. 56-177639 that the present applicant includes a spool-type control valve that switches based on the input rotation from the steering wheel, and an output drive unit that is connected to the wheels via the control valve. In a power steering device that selectively supplies pressurized oil to a control valve, there is a valve seat that receives a return spring disposed at the end of a spool of a control valve; A power steering device is proposed that includes reaction oil chambers, a circuit that communicates these reaction oil chambers with each other, and an electromagnetic valve that closes this circuit when the speed of the vehicle or engine exceeds a predetermined value. There is. According to this device, after the vehicle's running speed or engine speed increases above a certain level, the spool of the control valve is oil-locked to the neutral position and the flow of pressure oil to the output drive section is stopped, thereby controlling the steering wheel operation. Since the hydraulic assist is suppressed, the steering force can be appropriately increased during high-speed driving to create a stable driving sensation.

However, in order to completely lock the spool with oil in this device, the valve seat of the control valve and the solenoid valve must be completely airtight.
As a result, there is a problem in that high-precision machining is required, leading to high costs.

The present invention was made in order to solve the above-mentioned problems.The present invention has been made in order to solve the above-mentioned problem. By guiding oil and restraining it in a neutral position and cutting off the supply of pressurized oil to the output drive unit, the system aims to stop power assist for steering wheel operations during high-speed driving and improve high-speed stability.

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

A planetary gear type power steering device to which the present invention is applied will be explained with reference to FIGS. 1 and 2.

The device main body is composed of a planetary gear device 2, a control valve 3, and an output drive section (power cylinder) 1. First, the planetary gear device 2 consists of three planetary gears 4 to 4 supported by a carrier (input shaft) 7 connected to a handle H, a sun gear 5 meshing with the three planetary gears 4, and a ring gear 6.
The sun gear 5 is connected to the output drive section 1, and a groove 8 is formed on the outer periphery of the ring gear 6. A pin 9 is inserted into the groove 8 in the radial direction.
The end portion of the control valve 3 projects into the lumen 13 of the control valve 3, which will be described later.

Next, the control valve 3 is housed in the valve hole 10 , and a spool 12 is housed inside the sleeve 11 fixed to the valve hole 10 so as to be slidable in the axial direction. It is formed short, and the end of a pin 9 that fits into the groove 8 of the ring gear 6 and penetrates the side wall of the spool 12 protrudes from the inner cavity 13 thereof.

There are two annular grooves 1 on the outer peripheral surface of this spool 12.
4 and 15 are formed, and three annular grooves 16 to 18 are formed on the inner circumferential surface of the sleeve 11, and among these, the left and right annular grooves 16 and 18 communicate with the hydraulic pump P via a passage 19, and the so-called The central annular groove 17 communicates with a tank 21 via a passage 20, forming a so-called tank port.

In addition, passages (not shown) that communicate with the pressure chambers 1A and 1B of the output drive section 1 are opened in the inner circumferential surface of the sleeve 11, respectively, and are located at the annular grooves 14 and 15 formed in the valve spool 12. and form an actuation port. Although the above-mentioned configuration is similar to that of a well-known device, the present invention further includes:
As mentioned above, means are provided to maintain the spool 12 in a neutral position so that it cannot be switched when the vehicle or engine speed increases.

This means includes connectors 22, 22 that close both side openings of the valve hole 10, and connectors 22, 22 that contact both end surfaces of the sleeve 11 in the neutral state.
Valve seats 25 and 25 define reaction oil chambers 23 and 24 between them, and are interposed between the valve seat 25 and the connector 22 and urge the valve seat 25 to be crimped onto the sleeve 11. spring 2
6, 26 and the reaction oil chambers 23, 24; and a solenoid valve 28 which is interposed in the circuit 32 and which opens and closes the circuit 32, which communicates the circuit 27 with a part of the pump P. , a control device that drives the electromagnetic valve 28 in the direction of opening while the speed is above a predetermined value (for example, a control device that compares the signal from the speed sensor 29 with a set value and outputs a drive signal to the electromagnetic valve) comparator) 30, etc.

The electromagnetic valve 28 includes a valve 28a and an electromagnetic solenoid 28b. A spool 34 is housed in the valve hole 33 of the valve 28a so as to be slidable in the axial direction. An annular groove 3 is formed on the outer peripheral surface of this spool 34.
5 is formed, and 3 is formed on the inner peripheral surface of the valve hole 33.
Two annular grooves 36 to 38 are formed, of which the right (as shown) and center annular grooves 36 and 37 are formed.
The high pressure chamber and both reaction force oil chambers 2 of the hydraulic pump P are connected through parts 32a and 32b of the circuit 32, respectively.
The base 33a on the left side (illustrated) of the valve hole 33 communicates with the circuit 27 that communicates the valve holes 33 and 24.
communicates with tank 21 via circuit 39.

This electromagnetic valve 28 normally closes the circuit 32 as shown in the figure, while closing the circuit 32b and the annular groove 3.
7, 35, 38, both reaction force oil chambers 23, 2 by the circuit 27 via the valve hole base 33a and the circuit 39.
4 are both connected to the tank 21, but when the electromagnetic solenoid 28b is actuated by the output signal of the control device 30 and pushes out the spool 34, the circuit 32b
While cutting off communication between the annular groove 36 and the circuit 39,
The circuit 32a is connected to the circuit 32b via 35 and 37.
The hydraulic pressure generated by the hydraulic pump P is connected to the circuit 3.
The reaction force is led to both the reaction force oil chambers 23 and 24 via the oil chambers 2 and 27.

The effects based on the above configuration are as follows.

First, to explain the normal power steering operation when the speed is below a predetermined value, when the handle H is turned and the planet gears 4 to 4 are rotated via the carrier 7 connected thereto, the output drive section 1 and the sun gear 5 connected thereto are in a pseudo-fixed state based on ground resistance, the ring gear 6 rotates, and the spool 12 is moved, for example, to the right via the pin 9 that fits into the groove 8 of the ring gear 6. Displace.

At this time, the reaction oil chamber 24 is connected to the tank 2 through the circuits 27 and 32a, the electromagnetic valve 28, and the circuit 39.
1, the spool 12 contracts the oil chamber 24 and freely moves to the right.

Then, until now, passage 19 (pump port),
Pressure oil from the pump, which had been circulating to the tank 21 via the annular grooves 16, 14, 17 and the passage 20, is switched by the rightward movement of the spool 12, and is transferred to one side of the output drive unit 1 via a passage (not shown). Pressure oil is fed into the pressure chamber 1A, while the other pressure chamber 1B communicates with the passage 20 through a passage (not shown) and becomes a low pressure side, so the output drive unit 1 turns the wheels.

When the handle H is turned in the opposite direction to the above, the spool 12 moves to the left, and the output drive section 1 turns the wheels in the opposite direction. In this way, the steering force is reduced in low speed ranges where the ground resistance of the wheels is large.

On the other hand, if the speed increases and exceeds a predetermined value, the electromagnetic solenoid 28b drives the spool 34 toward the tip based on a command from the control device 30, closes the circuit 39, and closes the annular groove 36.
35 and 37, and the pressure generated by the hydraulic pump P is guided to the reaction oil chambers 23, 24 via the circuit 27, so that in the neutral position, the valve seats 25, 25 are moved by this oil pressure into the sleeves. 11
is pressed against both end faces. As a result, spool 12
Therefore, the ring gear 6 is fixed via the pin 9, and as a result, the sun gear 5 rotates as the handle is operated, and the output operating section 1 is operated by manual operation.

In addition, in this case, the valve seats 25, 25 are
When the electromagnetic valve 28 is opened, it is always pressed against the end face of the sleeve 11 by the hydraulic pressure of the hydraulic pump P, so even if a slight leak occurs between the two, the spring seats 25, 25 are pressed against the spool 12 by the hydraulic pressure.
As a result, spool 1
2's neutral restraint is completely maintained. Therefore, there is no need for high-precision seal processing as in conventional devices.

In this way, the control valve 3 is not switched at high speeds, and while the spool 12 remains in the restrained state, a manual operation state is established in which no hydraulic assist force is applied to the steering wheel operation.

As a result, the steering force does not become unnecessarily light during high-speed driving, and a stable steering feel can be obtained.

Note that the speed at which the spool 12 is restrained can be determined as appropriate depending on the specifications of the vehicle and engine, but the amount of oil from the pump, which is the oil pressure source of the power steering device, can be determined to determine the speed. If a drooping pin type flow control valve is provided, which decreases the flow rate as the flow rate increases, it goes without saying that the discharge flow rate should be restricted in a speed range where the discharge flow rate decreases sufficiently.

As explained above, according to the present invention, after the traveling speed of the vehicle or the rotational speed of the engine increases above a certain level, high pressure oil from the hydraulic pump is guided to both ends of the spool of the control valve to restrain it in the neutral position. By stopping the flow of pressurized oil into the output drive unit, the hydraulic assist for steering wheel operation is controlled, which increases the steering force to an appropriate level during high-speed driving to provide a stable steering feel. can be produced.

Furthermore, the sealing accuracy of control valves and electromagnetic valves can be lowered, and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention;
FIG. 2 is a sectional view of the valve when it is in neutral. 2... Planetary gear device, 3... Control valve, 6... Ring gear, 8... Groove, 9... Pin,
10... Valve hole, 11... Sleeve, 12...
Spool, 13... Spool lumen, 23, 24...
...Reaction oil chamber, 25...Valve seat, 27,3
2, 39...Circuit, 28...Solenoid valve, 30...
... Control device, 31 ... Notch groove, 33 ... Valve hole, 34 ... Spool, 35 to 38 ... Annular groove.

Claims (1)

[Claims] 1. A power steering device comprising a spool-type control valve that switches and operates based on input rotation from a steering wheel, and selectively supplies pressurized oil to an output drive unit connected to wheels via the control valve,
A valve seat that receives a return spring disposed at the end of a spool of a control valve, two reaction oil chambers defined at both ends of the spool by this valve seat, and a circuit that communicates these reaction oil chambers with each other. This circuit includes a circuit that guides the hydraulic pressure of the hydraulic pump independently of the circuit to the output drive unit, and a circuit that guides the hydraulic pressure when the speed of the vehicle or engine is above a predetermined value, and the circuit that guides the hydraulic pressure to the valve seat. A power steering device comprising: an electromagnetic valve that presses and restrains the spool by applying hydraulic pressure of a pump.