JPH0144544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a bypass valve for adjusting steering pressure in a power steering system for a vehicle, that is, a bypass valve for adjusting high pressure side and a low pressure side flow path of the power steering system in response to a control pressure according to vehicle speed. This is a bypass valve that adjusts steering pressure by cutting off communication. Its purpose is to utilize the pressure (steering pressure) generated in the power cylinder when the steering wheel is suddenly turned while driving at high speed. To reduce the steering force of a power steering device.

In general, in automobiles equipped with a power steering device, both chambers of the power cylinder of the power steering device are communicated with each other during high-speed driving in order to compensate for the problem that the steering wheel operation becomes too light when driving at high speeds. Measures have been taken to bypass this to the low pressure side, thereby reducing the steering gain. However, when the driver suddenly turns the steering wheel while driving at high speed, the steering gain decreases due to the bypass control of the pressure oil, making the steering wheel operation heavier and causing a sense of uneasiness.

In order to solve the above-mentioned problems, the present invention is capable of regulating the decrease in steering gain in response to the steering pressure generated in the power cylinder when a sudden steering wheel is turned at high speed, and also capable of providing desired characteristics. It is an object of the present invention to provide a bypass valve for regulating steering pressure that is easy and has a simple structure.Examples of the present invention will be described below with reference to the drawings.

In FIG. 1, 10 indicates a power steering device;
This power steering device 10 is, for example,
The valve housing 11 containing the servo valve and the power cylinder 12 fitted with the piston are fixed together, and when the servo valve is operated by operating the handle,
A constant flow of pressure oil supplied from the steering pump 13 via the supply pipe 14 is distributed to one chamber of the power cylinder 12, and the oil in the other chamber of the power cylinder 12 is discharged to the tank 16 via the discharge pipe 15. be done.
A bypass valve 30 configured to be described later is attached to the power cylinder 12 to communicate or cut off both chambers of the power cylinder 12 depending on the vehicle speed.

Reference numeral 20 indicates a known trochoid pump driven by the propeller shaft of the transmission 21, and the suction side of the trochoid pump 20 is connected to the exhaust pipe 15 of the power steering device 10 via the suction pipe 22.
The discharge side thereof is connected to the pressure oil inlet 301 (see FIG. 2) of the bypass valve 30 via the discharge pipe 23. Discharge pipe 23 and suction pipe 22
A control throttle valve 24 that controls the discharge pressure of the trochoid pump 20 to a pressure that corresponds to the rotational speed of the propeller shaft, that is, the vehicle speed, and a relief valve 25 that sets the upper limit of the discharge pressure are connected in parallel. ing.

As shown in FIG. 2, the bypass valve 30 includes a valve body 31 that is fluid-tightly fixed to the upper circumferential wall of the power cylinder 12.
1 is provided with a flow path 26 that opens into the right chamber of the power cylinder 12 and a flow path 28 that opens into a through hole 27 that communicates with the left chamber of the power cylinder 12. Small diameter portion 32a of stepped inner hole 32 provided in valve body 31
Inside there is a pair of bypass slits 41a, 41a.
A bypass valve valve body 41 having a bypass valve body 41 is fitted so as to be slidable in the axial direction, and a control pressure proportional to the vehicle speed is applied to one end of this valve body 41 through a pressure oil inlet 301. is open to the flow path 26 via an annular groove 33a provided in the inner wall of the valve body 31. Note that the flow path 28 opens into an annular groove 33b provided in the inner wall of the valve body 31, and communicates with the flow path 26 through each bypass slit 41a when the valve body 41 is displaced downward in the drawing. The compression coil spring 43 has one end locked to the valve body 41 and the other end to a circlip 45 fixed to the inner wall of the valve body 31 via an annular retainer 44, and the valve body 41 is controlled by a predetermined mounting load. It is energized against pressure. In this case, the small diameter portion 32a of the stepped inner hole 32 that accommodates the spring 43 is connected to the reservoir 16 through the through hole 46. The plug 50, which is provided opposite the large diameter portion 32b of the stepped inner hole 32 of the valve body 31, is fluid-tightly inserted into the radial through hole 12a provided in the upper peripheral wall of the power cylinder 12, intersecting the through hole 27. Two spools 52 and 53 are coaxially fitted into an inner hole 51 provided at the axis of the plug 50, facing the valve body 41 mentioned above. In this case, the first spool 52 is integrally provided with a control rod 54 that protrudes into the small diameter portion 32a of the stepped inner hole 32, and the lower end of the first spool 52 can come into contact with the upper end of the first spool 53. A radial port 50a provided in the plug 50 is provided at this lower end.
The hydraulic oil in the through hole 27 is applied through the hole. Further, the second spool 53 is prevented from coming off downward by a ring 55 fixed to the peripheral wall of the inner hole 51, and receives the first spool 52 at its upper end, and the right chamber of the power cylinder 12 at its lower end. is exposed. The compression coil spring 56 has one end engaged with a stepped portion of the stepped inner hole 32 of the valve body 31 and the other end engaged with an annular flange 52a provided integrally with the first spool 52 to maintain a predetermined mounting load. The spools 52 and 53 are urged downward in the drawing.

Next, the bypass valve 3 configured as described above is
The functions of 0 will be explained. When the trochoid pump 20 is driven by the propeller shaft while the vehicle is running, hydraulic oil is sucked into the trochoid pump 20 through the suction pipe 22 and pressurized oil is discharged into the discharge pipe 23. The pressure oil discharged into the discharge pipe 23 acts on the upper surface of the valve body 41 at the pressure oil inlet 301 of the bypass valve 30, but a part of this pressure oil is transferred to the control throttle valve 2.
4 to the suction side of the trochoid pump 20, the pressure oil acting on the upper surface of the valve body 41, that is, the control pressure of the trochoid pump 20, is proportional to the vehicle speed. Therefore, when the automobile is running at low speed, the control pressure of the trochoid pump 20 is low, so the valve body 41 of the bypass valve 30 is not displaced, and both chambers of the power cylinder 12 are shut off, allowing normal power steering operation. .

By the way, when the vehicle speed reaches a predetermined speed V _S , the control pressure of the trochoid pump 20 increases in proportion to the vehicle speed, and this causes the valve body 41 of the bypass valve 30 to increase.
is displaced downward in the figure against the spring 43, and as a result, the valve body 4 for the flow path 26 and the flow path 28
The opening area of each slit 41a increases as shown in FIG. That is, when such an automobile runs at high speed, the opening area of each bypass slit 41a in the valve body 41 increases as the control pressure applied to the pressure oil inlet 301 increases, and the maximum area of this opening area is larger than that of the valve. The displacement of the body 41 is regulated by engagement with the upper end of the control rod 54. In such a state, both chambers of the power cylinder 12 are connected to the flow path 26, the slit 41a,
The output torque relative to the manual steering torque decreases as the opening area of the slit 41a increases, and the steering force required to operate the steering wheel during high-speed driving is controlled according to the vehicle speed. This provides stability in steering operation. In addition, in the above-mentioned normal steering wheel operation during high-speed driving, although the steering pressure generated in the left or right chamber of the power cylinder 12 is applied to the spool 52 or 53, it acts on the pressure receiving area of the spools 52 and 53. Since the steering pressure is smaller than the spring force of the spring 56, the control rod 54 is not displaced upward in the drawing.

Next, when the steering wheel is rapidly turned to the right or left while driving at high speed, the steering pressure applied to the left or right chamber of the power cylinder 12 increases rapidly in response to the steering wheel operation. The pressure becomes larger than the oil pressure _P1 shown in FIG.
4 on the valve body 41. Therefore, the valve body 41 is assisted by the steering pressure applied to the spool 52 or 53 and is displaced upward in the drawing against the control pressure applied to the pressure oil inlet 301. As a result, the slit 41a of the valve body 41 with respect to the flow paths 26, 28
The opening area of the spool 52 is as shown in FIG.
Or, the reduction is corrected in accordance with an increase in the steering pressure acting on the power cylinder 12, and the bypass flow rate of pressure oil between the two chambers of the power cylinder 12 is restricted.
This reduces the steering force required for rapid steering operations at high speeds. Note that the valve body 41 is not affected by changes in steering pressure until the control rod 54 comes into contact with it.

As understood from the detailed explanation above,
In the present invention, first and second spools 52 and 53 having the same outer diameter are inserted in series into a common inner hole 51 provided in the valve body 31 of the bypass valve 30 so as to be able to abut each other. Applying the steering pressure generated in the left and right chambers of the power cylinder 12, respectively, to the intermediate portion of the two spools 52, 53 and the tip of the second spool 53 when turning,
A bypass valve valve body 41 to which the control pressure is applied to the valve body 31 is coaxially fitted in the valve body 31 facing the first spool 52 , and the first spool 52 has a gap between the valve body 31 and the valve body 31 . A first spring 56 is attached to apply a predetermined spring force opposing the respective steering pressures, and a predetermined spring force opposing the control pressure is applied to the valve body 41 between the valve body 31 and the valve body 31. A second spring 43 is attached, and the displacement of the valve body 41 due to the control pressure is restricted by the displacement of each of the spools 52 and 53, and the opening area of the bypass slit 41a provided in the valve body is adjusted according to the steering pressure. Its structural feature is that the reduction correction is made by adjusting the opening area of the bypass slit 41a by appropriately setting the mounting loads of the first springs 56. As a result, for normal steering operation at high speeds, the steering force required for manual operation is increased, in other words, the steering gain is lowered and the steering wheel operation at high speeds is reduced. To ensure stability and respond appropriately to sudden steering operations at high speeds, the reduction in steering gain is regulated, the output torque of the power cylinder 12 is increased, and the steering force required for steering operations is increased. can be reduced. Further, in the present invention, as illustrated in the above embodiment, the valve body 4 to which control pressure is applied
1 and a spool 52 to which a steering force is applied;
53 are disposed coaxially, the shapes of the valve body 41 and the spools 52, 53 are simplified, and the above-described first spring 56 and second spring 43 can be easily assembled, allowing this type of bypass valve to have a simple structure. Furthermore, with the above configuration, the valve body 41 is provided with the second spring 4 until its displacement is regulated by the spools 52 and 53.
Since the operation is performed accurately according to the settings given by No. 3, there is an advantage that desired characteristics can be easily given to the bypass valve.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a hydraulic system diagram of a power steering device equipped with a bypass valve according to the present invention; FIG. 2 is a longitudinal sectional view of the bypass valve shown in FIG. 1; Figure 3 is a graph showing the relationship between the slit opening area of the valve body shown in Figure 2 and the control pressure, and Figure 4 is a graph showing the relationship between the slit opening area of the valve body shown in Figure 2 and the steering pressure generated in the power cylinder. It is a graph showing the relationship between Explanation of symbols, 12... Power cylinder, 30...
...Bypass valve, 31... Valve body, 41...
...Valve body, 41a...Slit, 43...Second spring, 50...Inner hole, 52...Spool, 54
...Control rod, 56...First spring.

Claims (1)

[Claims] 1. A common inner hole provided in the valve body of the bypass valve in a steering pressure adjustment bypass valve that communicates and disconnects the high-pressure side flow path and low-pressure side flow path of the power steering device in response to the control pressure depending on the vehicle speed. First and second spools having the same outer diameter are fitted in series so as to be in contact with each other, and the steering pressure generated in the left and right chambers of the power cylinder, respectively, when the steering wheel is turned left and right is applied to the middle part of the two spools and the second spool. A valve body for a bypass valve is attached to the tip of the second spool, and the control pressure is applied to the valve body facing the first spool.
A first spring is attached to the spool to apply a predetermined spring force opposing the respective steering pressures between the spool and the valve body, and a first spring is attached to the valve body to apply a predetermined spring force opposing the control pressure between the valve body and the valve body. A second spring that applies a predetermined spring force is attached, and the displacement of the valve body due to the control pressure is restricted by the displacement of each of the spools, and the opening area of the bypass slit provided in the valve body is adjusted to the steering pressure. A bypass valve for adjusting steering pressure that compensates for reduction accordingly.