JPH0133421Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spool-type control valve for a power steering device.

In order to reduce the steering force of the vehicle,
In the case of a power steering device that uses hydraulic pressure to power assist during steering, the steering reaction force is fed back to the input shaft in order to prevent the steering wheel from becoming too light due to the power assist and to give the driver an appropriate operating feel. are doing.

For this reason, in spool-type control valves that switch based on the input rotation from the handle shaft and selectively supply pressure oil to the output drive unit connected to the wheels, a reaction spring is arranged on the axis of the spool. However, in many cases, a steering reaction force is generated by a spring reaction force that opposes the axial displacement of the spool.

As an example of this, the applicant of the present application previously applied for the U.S. Pat.
The spool-type control valve for the rack-and-pinion power steering device proposed by Tsutsumi in No. 148612 will be explained.

In FIGS. 1 and 2, 1 is a rack connected to a steering link (tie rod etc. not shown), 2 is a pinion, 3 is a spool valve, and 4 is a main housing housing these.

A pinion 2 that meshes with the rack 1 is formed integrally with a pinion shaft 5 and is supported by the main body housing 4 via bearings 6 and 7 provided at the front and rear of the pinion 2. These bearings 6 and 7 are easily
The outer race 9 is inserted into an oval long hole 8 whose long axis is parallel to the pinion shaft 5, and is formed so that the pinion shaft 5 can be displaced by a predetermined distance left and right.

Next, the spool valve 3 is arranged in a direction perpendicular to the pinion shaft 5 and is slidably housed in the valve housing 16, so that the displacement of the pinion shaft 5 coincides with the sliding direction of the spool valve 3, and the spool valve 3 is driven. The spool valve 3 is switched and operated by the lever 10.

The lever 10 has a ring portion 1 that fits into the pinion shaft 5.
A support pin 12 and a drive pin 13 are protruded at symmetrical positions passing through the center of the main body housing 4, and the support pin 12 is inserted into the support hole 14 of the main body housing 4, and the drive pin 13 is inserted into the pin hole 15 of the spool valve 3. , the spool valve 3 is switched by a drive pin 13 that moves in an arc around the support pin 12 as the pinion shaft 5 is displaced from side to side.

The spool valve 3 has a valve housing 16
The valve housing 16 is provided with annular grooves 17 to 19 that form pressure oil passages between the valve housing 16 and the annular grooves 17 to 19 to connect the hydraulic chamber of the power cylinder (not shown) to the pump side or tank side. Operating ports A, B, pump port P, tank port T, etc. are formed that selectively communicate with The direction of pressure oil switching to the cylinder is switched. Here, 2
0 is a reaction spring that urges the spool valve 3 to the neutral position.

In the above configuration, when the pinion shaft 5 is rotated in any direction by operating a handle (not shown), the resistance of the rack 1 connected to the steering link is large, so the pinion shaft 5 is rotated for a long time along the rack 1 in this rotation direction. The pinion 2 is displaced by the amount allowed by the hole 8.

At this time, the drive lever 10 switches the spool valve 3 by means of a drive pin 13 that moves in an arc around the support pin 12 as the pinion shaft 5 is displaced from side to side. With this switching of the spool valve 3, the power cylinder is connected to the operating port A or B.
Pressure oil is supplied to drive the rack 1 in the direction of rotation of the pinion 2.

At this time, the reaction spring 20 is compressed and acts as a resistance against the movement of the spool valve 3, thereby acting as a steering reaction force toward the handle.

By the way, the displacement x of the spool valve 3 and the reaction force F of the reaction force spring 20 (or the input torque of the handle)
T _IN ) is directly proportional, as shown by the solid line in FIG. 3a, and the proportionality constant is expressed by the spring constant K.

On the other hand, the increase in the pressure p of the hydraulic oil flowing from the pump port P to the operating port A or B due to the displacement x of the spool valve 3 is a characteristic determined by the way the lands and chambers of the valve 3 are cut. As shown in Figure b, it tends to be small at first and then rise gradually.

On the other hand, the output of this power steering device is obtained by displacing the spool valve 3 against the reaction spring 20 with _the input T _IN and increasing the pressure of the hydraulic oil due to this displacement. The relationship of _OUT is shown in Figure 3a
By combining and b, we get something like c in the same figure. this is,
The relationship between the displacement x of the spool valve 3 and the reaction force F is the third
Since it is a straight line as shown in Figure a, the relationship between valve displacement x and pressure p shown in Figure 3b is approximately the same, and tends to rise gradually from the low pressure side to the high pressure side.

However, from the standpoint of maneuverability, the relationship between input and output is generally as shown in Figure 4. In the low pressure section of the assist hydraulic pressure, the input to output gain is generally low, and in the high pressure section, the input to output gain is low. It is desired that the output gain is high. This means that it is possible to prevent the steering wheel from turning excessively at high speeds, and also to make it easier to actively turn the steering wheel, that is, to turn the steering wheel at rest.

By the way, in order to obtain a preferable relationship between input and output as shown in FIG. 4, if the relationship between valve displacement x and reaction force F obtained by the reaction force spring 20 is a straight line as shown in FIG. The relationship between valve displacement x and oil pressure p must be set as shown in FIG.

However, in such a relationship, in general, in a high pressure region, even a small displacement x of the spool valve 3 causes a sudden change in pressure, and the sensitivity is too high, which is undesirable due to the vibration of the hydraulic system and the fluid-like sound of the spool valve 3. .

In order to avoid this undesirable tendency, the relationship between the displacement x and the spring reaction force F can be changed in the valve, for example, as shown by the chain line in FIG. 3a. That is,
When the reaction force F (input T _IN ) increases slightly above a certain range, the valve displacement x increases significantly, and the output F _OUT also increases.
As shown in the figure, it suddenly starts to rise.

The present invention was developed with attention to the above-mentioned points, and the input-output gain is lowered in the low-pressure part of the assist hydraulic pressure by setting the reaction spring, and
The purpose of the present invention is to provide a spool-type control valve for a power steering device, which has a high pressure at a high pressure part to improve high-speed steering performance and increase power assist at low speeds.

In order to achieve the above object, the present invention provides a spool-type control valve for a power steering device that switches based on input rotation from a steering wheel and selectively supplies pressure oil to an output drive unit connected to the wheels. Reaction springs with equal spring constants are interposed between both ends of the spool valve and the valve housing with a preload applied to them, and the magnitude of the preload is set in the middle of the stroke of the spool valve from the neutral position. It was set to such an extent that the reaction force on the extension side would disappear.

Based on the above configuration, at the beginning of the spool valve's stroke, the combined force of the reaction springs that are in contact with both ends becomes the reaction force, and on the other hand, when the spool valve strokes beyond a certain point, the preload of the rebound side reaction spring increases. Therefore, the input-output gain is low in the low-pressure part of the generated oil pressure and high in the high-pressure part.

Hereinafter, embodiments of the present invention will be described based on the drawings.

As shown in FIG. 6, the spool valve 3 is slidably supported by the valve housing 16, and the drive pin 13 of the drive lever 10 is engaged with the pin hole 15. At both ends of the spool valve 3, reaction springs 22, 22 are interposed between plugs 21, 21 which are screwed into the valve housing 16.

These reaction springs 22, 22 have the same spring constant K and are given the same preload F ₀ ,
The spool valve 3 is held at the neutral position.

Therefore, when displacing the spool valve 3 to one side, the preload of the reaction spring 22 on the other side
Until F ₀ disappears (x = F ₀ /K), the spring constant becomes 2K as shown by the thick solid line in Figure 7a, and x =
After F ₀ /K, it becomes K. This is exactly because the input T _IN is
After 2F ₀ , the valve displacement x increases greatly with a small input, and when combined with the conventional valve characteristics shown in FIG. 7b, the input-output relationship shown in FIG. 7c is obtained.

This has the same tendency as the above-mentioned preferable input-output relationship, and provides preferable output characteristics in terms of maneuverability.

FIG. 8 shows another embodiment of the present invention, which differs from FIG. 6 in that there are washers 25, 25 and a plug in contact with stepped portions 24, 24 of the valve hole 23, which are approximately equal to the entire length of the spool valve 3. 21, 21 are interposed between centering springs 26, 26, which have a spring constant of K ₁ and a preload of F ₀₁ , unlike the reaction spring 22.

According to this, the relationship between the valve displacement x and the spring reaction force F becomes as shown in FIG. 2
6, neutral stability is improved.

FIG. 10 shows another embodiment of the present invention,
What is different from FIG. 6 is the stepped portion 2 of the valve hole 23.
Washers 27, 27 that come into contact with 4, 24 and clamp the spool valve 3, and another large diameter stepped portion 2.
Flange-shaped cylindrical washers 29, 2 that come into contact with 8, 28
9, washers 27, 27 and washers 29,
The first reaction force spring (spring constant
K ₁ , preload F ₁ ) 30,30, and washer 2
A second reaction spring (spring constant K ₂ , preload F ₂ ) 3 is installed between the collars 9 and 29 and the plugs 21 and 21.
1, 31, K ₁ > K ₂ and F ₁ <
Set it like F ₂ .

According to this, the relationship between valve displacement and spring reaction force F becomes as shown in FIG. This can be done reliably by the reaction force spring 31.

As explained above, according to the present invention, reaction springs with the same spring constant are placed at both ends of the spool valve with a preload applied, and two-phase spring reaction force is obtained. The gain can be made low in the low pressure area of the hydraulic pressure and high in the high pressure area,
This improves steering stability when driving at high speeds, and makes it easier to operate the steering wheel when stationary.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing a conventional device, Fig. 2 is a sectional view taken along the - line in Fig. 1, and Fig. 3 shows the characteristics of the conventional device.
Figure b shows the valve displacement to oil pressure, Figure c shows the input to output characteristics, Figure 4 shows the preferred input to output characteristics, and Figure 5 shows the desired valve displacement to oil pressure characteristics for Figure 4. , FIG. 6 is a side cross-sectional view showing an embodiment of the present invention, and FIG. 7 shows the characteristics of FIG. Fig. c is a characteristic diagram of input to output, Fig. 8 is a side sectional view showing another embodiment of the present invention, Fig. 9 is a characteristic diagram of valve displacement to reaction force of Fig. 8,
FIG. 10 is a side sectional view showing another embodiment of the present invention;
FIG. 11 is a characteristic diagram of valve displacement to reaction force in FIG. 10. 3... Spool valve, 16... Valve housing, 20, 22... Reaction spring, 21... Plug, 24... Step portion, 25, 27, 29... Washer, 26... Centering spring, 28... Large-diameter stepped portion, 30...first reaction spring, 31...second reaction spring.

Claims (1)

[Claims for Utility Model Registration] (1) In a spool-type control valve of a power steering device that selectively supplies pressurized oil to an output drive unit connected to a wheel, the control valve switches based on input rotation from a steering wheel, Reaction springs with equal spring constants are interposed between both ends of the spool valve and the valve housing with a preload applied to them, and the magnitude of the preload is set in the middle of the stroke of the spool valve from the neutral position. A control valve for a power steering device, characterized in that the reaction force spring on the extension side is set to such an extent that it disappears. (2) The reaction spring is the first claim of utility model registration that includes a reaction spring interposed for valve centering.
The control valve for the power steering device described in .