JPH0534304Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a power steering rear wheel control valve that controls the flow rate and direction of oil sent to a power cylinder for power steering rear wheel steering.

(Prior Art) In general, power steering includes a handle 1, a power steering gear assembly (hereinafter referred to as "PSG") 3, a pump 9 and a tank 10 for steering the front wheels, and a rear wheel as shown in FIG. A wheel control valve 13, a pump 14 and a tank 15 for rear wheel steering, a flow control solenoid valve 16, a direction switching solenoid valve 17 for rear wheel steering, a controller 18, and a power cylinder 19 for rear wheel steering. We are prepared.

The PSG 3 includes a steering shaft 2 connected to the steering wheel 1, a pinion 4 provided at the tip of the steering shaft 2, and left and right front wheels 2.
A tie rod 5 connecting the nuts 1 and 22, a rack 6 formed on the tie rod 5, and a power cylinder 7 in which the tie rod 5 is a piston rod.
A power steering control valve 8 is provided which is linked to the steering shaft 2 and controls the flow rate and direction supplied to the power cylinder 7, and the pinion 4 is engaged with the rack 6.

The power steering control valve 8 is switched depending on the rotation direction and rotation angle of the handle 1, and for example, the power steering control valve 8 is switched in accordance with the rotation direction and rotation angle of the handle 1.
is connected to the pump 9, and the other cylinder chamber 7b is connected to the tank 10. Therefore, at this time, the power cylinder 7 operates and the front wheel 2
1 and 22 to the left.

The rear wheel control valve 13 is connected to the PSG 3 through hydraulic pilot lines 11 and 12. Further, the rear wheel control valve 13 is connected to the pump 14 for steering the rear wheels.

The flow rate control solenoid valve 16 is provided in a passage connecting the rear wheel control piece 13 and the pump 14.

The direction switching solenoid valve 17 is provided in a passage connecting the rear wheel control valve 13 and a power cylinder 19 for steering the rear wheels.

The controller 18 calculates rear wheel steering conditions from input data such as vehicle speed, steering angle, power steering output, and engine speed, and controls the flow rate control solenoid valve 16 and the direction switching solenoid valve 17 based on the calculated values. The control signal is output to the

Then, by turning the handle 1 to the left, one cylinder chamber 7a of the power cylinder 7 is connected to the pump 9, and the other cylinder chamber 7b is connected to the tank 10.
When connected, the tie rod 5 moves to the right and the front wheels 21, 22 are steered to the left.

When the front wheels 21 and 22 are steered as described above,
The pressure in one cylinder chamber 7a of the power cylinder 7 at that time acts on the rear wheel control valve 13 as a pilot pressure, causing the control valve 13 to open.

Further, at this time, the controller 18 functions to control the opening degree of the flow rate control solenoid valve 16 and the switching direction of the direction switching solenoid valve 17. Therefore, as described above, the rear wheel control valve 13
When the valve is opened, the flow rate of the oil discharged from the pump 14 is controlled by the flow rate control solenoid valve 16, and the direction is controlled by the direction switching solenoid valve 17, and the oil is discharged into either the cylinder chamber 19a or the rear wheel side power cylinder 19. 19b. This supplied oil operates the power cylinder 19 on the rear wheel side, causing the rear wheels 23, 2 to operate.
4 in a predetermined direction.

Further, as shown in FIG. 5, the rear wheel control valve 13 has a spool 131 slidably provided inside the housing 130, and the spool 131 is slidably provided inside the housing 130.
Both ends of the pilot chamber 13a and 13b are exposed to the pilot chambers 13a and 13b.

The housing 130 is formed with pilot ports 132 and 133, a P port 134, and A and B ports 135 and 136.

The pilot ports 132, 133 are opened to the pilot chambers 13a, 13b, and
Through the hydraulic pilot lines 11 and 12
Connected to PSG3, power cylinder 7 on the front wheel side
The operating pressure is introduced as pilot pressure to either one of the pilot chambers 13a, 13b.

The P port 134 is connected to the rear wheel steering pump 14 via a flow rate control solenoid valve 16. Further, the A and B ports 135 and 136 are connected to a power cylinder 19 for steering the rear wheels through the flow rate control solenoid valve 16 and the direction switching solenoid valve 17.

Note that reference numerals 137 and 138 indicate centering springs that act on both ends of the spool.

The rear wheel control valve 13 thus configured controls the pressure on the power cylinder 19 side in proportion to its opening degree, but since the throttle part c of the control valve 13 is a choke throttle, The pressure on the power cylinder 19 side on the rear wheel side is indicated by the solid line x in Fig. 6.
As shown, there is a linear proportional relationship.

(Problems to be Solved by the Present Invention) In the conventional control valve as described above, the throttle part is a choke throttle so that the gain with respect to the pilot pressure has a linear proportional relationship as described above. This choke throttle is greatly affected by changes in viscosity due to changes in oil temperature, and even if
Even if the pilot pressure is constant, the pressure on the power cylinder 19 side changes. That is, as shown in FIG. 6, when the oil temperature changes from normal temperature x to low temperature y, the gain increases and the pressure in the power cylinder 19 increases. On the other hand, when the oil temperature changes from normal temperature x to high temperature z, the gain decreases and
The pressure in the power cylinder 19 becomes low.

In other words, this conventional control valve has a problem in that it is difficult to perform stable control against changes in oil temperature.

The object of this invention is to provide a rear wheel control valve for power steering, which has less change in characteristics due to changes in oil temperature and can stabilize the rear wheel steering angle.

(Means for Solving the Problems) In order to achieve the above object, this invention disposes a spool inside a housing, and has an introduction part in the housing that introduces pilot pressure to both ends of the spool. A rear wheel control valve is provided, which applies driving pressure of a steering gear assembly including a power cylinder for front wheel steering to both ends of the spool to switch the spool, and configures a circulation circuit between the pump, the power cylinder, and the tank,
A choke throttle is provided in the pilot pressure introducing portion of the housing, an oil passage is formed inside the spool that penetrates in the axial direction, and an orifice is provided in the middle of this passage.

(Operation of the present invention) In this invention, the intermediate pressure between the choke formed at the pilot pressure introduction part and the orifice formed inside the spool acts as the pilot pressure.

The above-mentioned yoke is easily affected by changes in oil temperature, and the above-mentioned orifice is not easily affected by changes in oil temperature. Therefore, when the oil temperature decreases, the pilot flow rate through the choke yoke decreases, and the pilot pressure due to the orifice decreases. When the pilot pressure decreases,
The rear wheel pressure is reduced and corrected to the rear wheel pressure at normal temperature. Conversely, as the oil temperature increases, the pilot flow rate through the choke increases and the pilot pressure through the orifice increases. When the pilot pressure increases, the rear wheel pressure increases and is corrected to the rear wheel pressure at room temperature.

(Effects of the present invention) According to the rear wheel control valve of this invention, the intermediate pressure between the choke formed at the pilot pressure introduction part in the housing and the orifice formed in the middle of the oil passage formed inside the spool is controlled. It is made to act on the spool as pilot pressure. As a result, the pilot pressure can be changed in response to changes in oil temperature, and the rear wheel pressure can be corrected to remain constant, reducing changes in control characteristics due to changes in oil temperature, resulting in a stable rear wheel steering angle. There is an effect that can be obtained.

(Embodiments of the present invention) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of this invention.

In the rear wheel control valve 13 of the embodiment shown in FIG. 1, choke throttles 139 and 140 are formed in the pilot pressure introduction portion of the housing 130.

On the other hand, an oil passage 141 is formed inside the spool 131 provided inside the housing 130. This oil passage 141 passes through the spool 131 in the axial direction, and is connected to both pilot chambers 13a and 13.
b is connected. In addition, the oil passage 141
An orifice 142 is provided in the middle.

The rest of the structure of this embodiment is the same as the conventional one shown in FIG. 4, so common components are designated by the same reference numerals.

In the rear wheel control valve 13 of the embodiment shown in FIG. 1, the pilot pressure sent from the PSG side is passed through the choke throttles 139, 140 as shown in FIG.
It is further narrowed by the orifice 142. Therefore, the intermediate pressure of the double throttle by the choke throttles 139, 140 and the orifice 142 acts on the spool 131 as a pilot pressure.

The choke yoke throttles 139 and 140 are easily affected by changes in oil temperature, and the orifice 142 is not easily affected by changes in oil temperature, and the spool 1 as a whole.
The pilot pressure applied by 31 is affected by changes in oil temperature.

For example, when the oil temperature drops, Chi York 139, 14
The pilot flow rate decreases due to the throttling action of 0. When the pilot flow rate decreases, the pilot pressure due to the throttling action of the orifice 142 decreases, and as shown in FIG. 3, the rear wheel pressure is corrected to the rear wheel pressure at room temperature.

On the other hand, when the oil temperature rises,
The pilot flow rate is increased by the throttle action of the orifice 140, the pilot pressure is increased by the throttle action of the orifice 142, and the rear wheel pressure is corrected to the rear wheel pressure at room temperature.

As a result, according to this embodiment, the rear wheel pressure can be kept constant regardless of changes in oil temperature, and therefore a stable rear wheel steering angle can be obtained.

[Brief explanation of the drawing]

Figure 1 is a longitudinal sectional view of one embodiment of this invention;
Figure 3 is an explanatory diagram of the same operation, Figure 3 is an explanatory diagram showing the relationship between pilot pressure and rear wheel power cylinder pressure, Figure 4 is an explanatory diagram of a steering system using the control valve, and Figure 5 is an explanatory diagram of the steering system using the control valve. 6 is a longitudinal sectional view of a conventional rear wheel control valve, and FIG. 6 is a diagram showing the relationship between oil temperature, PSG pressure, and rear wheel pressure. 3...PSG, 11, 12...Hydraulic pilot line, 13...Rear wheel control valve, 14...Pump for rear wheel steering, 19...Power cylinder, 130
...Housing of the rear wheel control valve, 131...Spool, 139, 140...Choice provided at the pilot pressure introduction part, 141...Oil passage formed inside the spool, 142...Oil passage Orifice installed in the aisle.

Claims (1)

[Scope of utility model registration request] A spool is disposed inside the housing, and the housing is provided with an introduction part that introduces pilot pressure to both ends of the spool, and the driving pressure of the steering gear assembly including the power cylinder for steering the front wheels is transferred to both ends of the spool. In the rear wheel control valve, which switches the spool by acting on A rear wheel control valve for power steering, characterized in that a penetrating oil passage is formed and an orifice is provided in the middle of this passage.