JPS646985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oil amount adjusting valve for a power steering device, and more particularly, to an oil amount adjusting valve for a power steering device that can be downsized.

2. Description of the Related Art An example of a conventional oil amount regulating valve for a power steering device is the one shown in FIG.
To explain this structure, 1 is a pump, and this pump 1 is connected to an inlet port 3a of a control valve 3 via a supply path 2, and discharges working fluid from a reservoir tank 4 to the control valve 3. This control valve 3 has an outlet port 3b connected to a reservoir tank 4 via a drain passage 5, and a power cylinder 6.
is connected to two fluid chambers 7 and 8 via channels 9 and 10, and during steering, one fluid chamber is connected to the supply channel 2 to supply working fluid depending on the steering direction, and the other fluid chamber is connected to the supply channel 2. is communicated with the drain passage 5 to discharge the working fluid, and in the neutral state, the supply passage 2 and the drain passage 5 are short-circuited, and the working fluid is circulated without being supplied to the fluid chambers 7 and 8. 11 is a steering wheel. A pinion gear 12 that rotates together with the steering wheel 11 is provided below the steering wheel 11, and this pinion gear 12 is connected to a rack gear 1 formed on a rack 13.
It meshes with 3a. 14 is a cylinder, and this cylinder 14 is attached to the steering gear housing 1.
5, and a piston 13b fixed to the rack 13 is slidably inserted therein.
The power cylinder 6 is constituted by the cylinder 14, the piston 13b, and the rack 13. In this power cylinder 6, working fluid flows into either of the fluid chambers 7, 8 depending on the steering direction of the steering wheel 11, and presses the rack 13 in the steering direction to assist in steering force. 17 is an oil amount adjustment valve, which is interposed on the supply path 2, and
It is connected to the reservoir tank 4 via a bypass path 18. To explain the structure of this oil amount adjustment valve 17, 19 is the supply path 2 on the control valve 3 side.
is the outflow port to which pump 1 is connected, and 20 is the outflow port to which pump 1 is connected.
It is an inflow port to which the side supply path 2 is connected, and 2
1 is a drain port to which the bypass path 18 is connected. This oil amount adjustment valve 17 has a chamber 22 therein that communicates with an inflow port 20 and a drain port 21.
A chamber 24 communicates with this chamber 22 through an orifice passage 23 and also communicates with the outflow port 19.
The inflow port 2 is slidably inserted into the chamber 22.
0 and the drain port 21, a chamber 27 which is equipped with a spring 26 that urges the spool 25 toward the orifice passage 23, and into which the pressure of the chamber 24 is introduced; It has a plunger 28 that projects and changes the area of the orifice, and a solenoid 29 that is driven by a drive circuit (not shown) to operate the plunger 28. The spool 25 is
Differential pressure between chamber 22 and chamber 27, that is, orifice 2
3, the fluid flowing in from the supply path 2 is released to the bypass path 18 through the notch 25a on its outer periphery, and the amount of fluid supplied to the control valve 3 is controlled by the plunger 2.
The amount corresponds to the area of the orifice 23 controlled by 8. Further, inside the spool 25, there is a chamber 31 that communicates with the chamber 27 through a passage 30 and also communicates with the drain port 21, and this chamber 31.
A relief valve 34 is provided in the chamber 27, that is, a valve body 33 that is biased by a spring 32 to freely open and close the passage 30. In this case, the working fluid in the chamber 27 is discharged to the drain port 21.

However, in the oil volume adjustment valve of such a power steering device, the discharge pressure of the pump 1 is applied to the plunger 28, and the oil volume adjustment valve 17 is interposed in the supply path 2 to control the discharge pressure of the pump 1. Even when all of the working fluid flows through the orifice passage 23, it is necessary to control the solenoid 29 that operates the plunger 28.
The solenoid 29 needs to be strong enough to withstand the control of high pressure and large flow of working fluid.
There was a problem that the oil amount regulating valve 17 could not be made smaller because of the increased size. Furthermore, when the power cylinder 6 is operated, the pressure of the working fluid in the supply passage 2 increases, but the flow rate of the working fluid flowing through the orifice 23 increases or decreases in proportion to the square root of the differential pressure across the orifice. 28 to change the area of the orifice 23 to quickly supply the required amount of working fluid to the power cylinder 6 in such a case, the power cylinder is unable to respond to the steering wheel 11 operation. There was a problem that the response of 6 was reduced.

This invention was made by focusing on such conventional problems, and includes a flow control valve that keeps the flow rate of working fluid discharged by a pump constant;
In a power steering device having a bypass passage that short-circuits a supply passage and a drain passage, an orifice valve having an orifice passage whose flow passage area is variable and a pressure compensation valve that keeps the differential pressure before and after the orifice passage constant are provided. It is an object of the present invention to solve the above-mentioned problems by providing a flow rate regulating valve in a bypass passage to adjust the flow rate of bypassing working fluid to control the flow rate of working fluid supplied to the control valve.

The present invention will be explained below based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention. Note that the same parts as those of the conventional power steering device shown in FIG. 1 are given the same numbers, and the explanation thereof will be omitted.

First, to explain the configuration, numeral 35 is a flow control valve installed on the supply path 2a near the pump 1;
5 is connected to the supply path 2b connecting the pump 1 and the reservoir tank 4 via a bypass path 36, and supplies the working fluid discharged by the pump 1 to the supply path 2c at a constant flow rate. To explain the structure of this flow control valve 35, 37 is a housing, and inside this housing 37, a chamber 38 communicating with the supply path 2c and a chamber 40 into which a spool 39 is slidably inserted are formed. These chambers 38 and 40 are communicated through an orifice passage 41. Further, the chamber 40 is defined into two chambers 40a and 40b by the spool 39, and has a port 42 communicating with the pump 1 and a supply path 2.
One chamber 40a communicates with the port 42 and the orifice passage 41, and the pressure of the chamber 38 is introduced into the other chamber 40b through an introduction path 44. When the spool 39 slides within the chamber 40, the port 43 is communicated with or shut off from the chamber 40a by a notch 39a formed in the spool 39 toward the chamber 40a. Reference numeral 45 denotes a spring disposed within the chamber 40b, and this spring 45 biases the spool 39 in the direction of the orifice passage 41. moreover,
A relief valve 46 is provided on the spool 39. This relief valve 46 is connected to the spool 3
A chamber 47 defined within the interior of the chamber 9 and communicating with the port 43
and a passage 48 that communicates this chamber 47 and chamber 40b.
It has a valve body 49 that can freely open and close this passage 48 from the chamber 47 side, and a spring 50 that presses this valve body 49 against the passage 48. Room 4
The working fluid in 0b is discharged to port 43.

Moreover, 51 is an oil amount adjustment valve, which is interposed in the middle of a bypass path 52 that short-circuits the supply path 2 and the drain path 5. The oil amount adjusting valve 51 includes an orifice valve 54 having an orifice passage 53 with a variable flow area, and a pressure compensation valve disposed upstream of the orifice valve 54 to maintain a constant differential pressure across the orifice passage 53. It is composed of a valve 55. First, the configuration of the pressure compensation valve 55 will be explained. 56 is 1
This balance piston has a pair of lands, one of which (the left side in FIG. 2) has a large pressure receiving area, and this balance piston 56 slides into a chamber 58 formed inside the housing 57. It is movably stored, and this chamber 58 is further divided into four small chambers 59,
60, 61, and 62. 63 is an inlet port connected to the bypass passage 52 on the side of the supply passage 2, and this inlet port 63 communicates with the small chamber 59 via a constriction part 64, through which the balance piston 56 slides. When the valve is moved, the area of the flow path is variable. On the other hand, this small room 5
9 has two small chambers 60,
61, and due to the land area difference mentioned above, the pressure in the small chamber 59 presses the balance piston 56 to the left in the figure, and also communicates with the inflow port 66 of the orifice valve 54. 67 is a spring stored in the small chamber 62, and this spring 6
7 connects the balance piston 56 to the aforementioned small chambers 59, 6.
It is biased to the right in the figure to counteract the pressing force of 0.61. Further, this small chamber 62 communicates with a chamber 69 of the orifice valve 54 through a passage 68.
Next, the configuration of the orifice valve 54 will be explained. 70
is a spool that is slidably housed in the aforementioned chamber 69. This spool 70 forms an orifice passage 53 with the wall surface of the chamber 69. This orifice passage 53 communicates the chamber 69 with the above-mentioned inflow port 66, and changes its flow area when the spool 70 slides. Further, this chamber 69 is connected to the small chamber 62 of the pressure compensating valve 55 as described above.
It also has an outlet port 72 and communicates with the bypass passage 52 on the drain passage 5 side. The spool 70 is biased to the right in the figure by a spring 73 housed in a chamber 69 at the left end in the figure, and is connected to a solenoid 74 at the right end in the figure to counteract the elastic force of the spring 73. A pressing force is applied. This solenoid 74
is connected to vehicle speed detection means 75 for detecting the speed of the vehicle via a drive circuit 76, so that its pressing force can be controlled continuously, that is, linearly. In other words, a certain pressing force of the solenoid 75 is applied to the spool 7.
If it is set to 0, the spool 70 will be connected to the spring 73.
It stops at a certain position due to the elastic force of , opens the orifice passage 53 to a certain flow area, and controls the flow rate passing through the orifice passage 53.

Next, the action will be explained.

Generally, the steering force of the steering wheel 11 needs to be changed according to the traveling speed of the vehicle.
It is desirable that the steering force be larger at high speeds than at low speeds.

First, let me explain the characteristics of the orifice. For an ideal orifice, the steady-state flow rate Q of ideal fluid passing through the orifice is given by the following equation.

However, C: flow coefficient, A: orifice area,
g: Dynamic acceleration, γ: Specific weight of fluid, P ₁ : Upstream pressure, P ₂ : Downstream pressure In other words, when the orifice area is constant, the flow rate Q flowing through the orifice is the same as before and after the orifice. It is proportional to the square root of the fluid pressure difference ΔP (ΔP=P ₁ - P ₂ ), and if this fluid pressure difference ΔP is constant, the flow rate Q is proportional to the area A of the orifice,
Furthermore, if the fluid pressure difference ΔP and the area A of the orifice are constant, the flow rate Q will also be constant.

When the vehicle is running at a certain speed, the pump 1 is driven and discharges working fluid from the reservoir tank 4 to the flow control valve 3. Normally, this pump 1 is driven by the engine and the speed is approximately proportional to the engine speed. It is driven at the same rotation speed. Therefore, the flow rate of the working fluid discharged by the pump 1 increases or decreases in proportion to the engine speed, and increases as the engine speed increases. The flow control valve 35 maintains a constant pressure difference between the chambers 38 and 40a before and after the orifice passage 41, and supplies a constant flow rate of the working fluid discharged from the pump 1 to the supply passage 2c. That is, if the pump 1 is now discharging a certain flow rate of working fluid, this working fluid flows into the chamber 40a from the port 42, flows out into the chamber 38 through the orifice passage 41, and flows before and after the orifice passage 41. A pressure difference is created between chambers 40a and 38, that is, chamber 40a and chamber 4
0b. Therefore, the spool 39 is pressed and moved downward in the figure due to the differential force between this pressure difference and the elastic force of the spring 45, and the port 43 and the chamber 40a are opened with a certain flow path area, and the working fluid in the chamber 40a is opened. is recirculated from port 43 to pump 1. That is, the spool 39 is pressed by the differential force and comes to rest at a certain position. Now, when the rotational speed of the engine increases and the discharge amount of the pump 1 increases, the flow rate of the working fluid flowing into the chamber 40a from the port 42 increases, and the flow rate of the working fluid flowing through the orifice passage 41 increases. growing. However, as described in the characteristics of the orifice above, since the flow area of the orifice passage 41 remains unchanged, the chamber 4
Between 0a and chamber 38, that is, between chamber 40a and chamber 40
The pressure difference △P between spool 3 and
9 is pushed downward with a larger differential force and moves,
The aforementioned flow path area S is further increased. Then,
Since the flow rate of the working fluid circulating from the chamber 40a to the pump 1 via the port 43 increases, this differential pressure ΔP decreases and becomes equal to the initial differential pressure ΔP. That is, the flow rate of the working fluid supplied to the supply path 2c remains unchanged regardless of the amount discharged by the pump 1. Note that when the engine rotational speed decreases and the discharge amount of the pump 1 decreases, the process opposite to the above case is followed.

Furthermore, if the pressure of the working fluid in the supply passage 2c becomes excessively high, such as when the power piston 6 operates, this pressure is transmitted from the chamber 38 to the chamber 40b through the introduction passage 44, and the relief valve 46 is activated. Operate. That is, the valve body 49 moves against the elastic force of the spring 50 due to this pressure, and the chamber 38, that is, the supply path 2c, communicates with the port 43 via the introduction path 44, the chamber 40b, the passage 48, and the chamber 47, The working fluid in the supply path 2c is supplied to the reservoir tank 4.
This prevents problems caused by excessively high pressure of the working fluid in the supply path 2c.

A part of the working fluid, which has been made to have a constant flow rate by the flow control valve 35, flows to the drain path 5 via the control valve 3, and the remaining part flows to the drain path 5 via the bypass path 52 and the oil amount adjustment valve 51.
flows to From this bypass path 52 to the oil amount adjustment valve 5
The working fluid flowing into the pressure compensation valve 55 flows into the inlet port 63 of the pressure compensating valve 55, and then flows into the small chamber 59 from the constriction portion 64. If the balance piston 56 is in a parallel state, the pressure P ₁ in the small chamber 59 is introduced into the two small chambers 60 and 61 and becomes a force that presses the balance piston 56 to the left in the figure.
The pressure P ₂ and the elastic force Fx of the spring 67 are the forces that press the balance piston 56 to the right in the figure, so the force exerted by the pressure in the small chambers 60 and 61 and the force exerted by the pressure in the small chamber 62 are The differential force is constant, and the differential force is equal to the elastic force Fx of the spring 67. Therefore, the small chambers 60 and 61, that is, the small chamber 59
The pressure difference between the pressure in the small chamber 62 and the pressure in the small chamber 62 is constant.
Now, for example, when the power cylinder 6 is operated and the pressure in the supply path 2c increases, the flow rate of the working fluid flowing into the small chamber 59 through the constriction part 64 increases, so that the small chamber 59, that is, the small chambers 60 and 61, has a large pressure ( P ₁ +△p) and the balance piston 56
Press and move it to the left in the figure. Therefore, the flow path area of the throttle portion 64 becomes smaller and the pressure in the small chamber 59 becomes smaller, so that the small chamber 59 returns to its original pressure _P1 . In other words, even in such a case,
The pressure difference between the small chamber 59 and the small chamber 62 is constant. On the other hand, if the pressure in the supply path 2c decreases, the balance piston 56 moves to the right in the figure due to the elastic force of the spring 67, resulting in a pressure difference between the small chambers 59 and 62. is held constant.

On the other hand, since the vehicle is traveling at a certain speed, the vehicle speed detection means 75 detects the speed of the vehicle.
detects its running speed and outputs a signal corresponding to the running speed to the drive circuit 76. The drive circuit 76 applies an exciting current to the solenoid 7 according to the signal.
4 is energized, and the spool 70 connected to the solenoid 74 receives a force from the solenoid 74 toward the left in the figure that is proportional to the excitation current. Further, this solenoid 74 continuously changes the force applied to the spool 74 according to changes in the excitation current. Here, for example, if the vehicle is traveling straight and the steering wheel 11 is in the neutral position, the control valve 3 short-circuits the supply path 2 and the drain path 5,
The working fluid circulates back to the reservoir tank 4 without flowing into the fluid chambers 7 and 8 of the power cylinder 6. Further, the flow rate of the working fluid that returns to the reservoir tank 4 via the bypass path 52 and the oil amount adjustment valve 51 is as follows:
As described above, the differential pressure across the orifice passage 53 of the orifice valve 54 is kept constant by the pressure compensating valve 55 regardless of the pressure in the supply passage 2c, so it is proportional to the flow area of the orifice passage 52. Also,
The flow area of the orifice passage 52 is determined by the pressing force of the solenoid 74 applied to the spool 70 and the elastic force of the spring 73. That is, the flow rate of the working fluid flowing into the bypass path 52 is changed according to the traveling speed, and the power cylinder 6
The flow rate of the working fluid supplied to the pump is controlled.
In this way, the solenoid 74 controls part of the working fluid discharged by the pump 1 under a constant differential pressure, so a large force is not applied to the solenoid 74, making it possible to downsize, and the pressure in the supply path 2c is It becomes possible to control the flow rate regardless of the flow rate, resulting in precise control.

Next, from the above state, the steering wheel 1
The case where 1 is operated in a certain direction will be explained. Now, when the steering wheel 11 is steered in a certain direction, for example, the control valve 3 connects one fluid chamber 7 of the power cylinder 6 with the supply path 2c to supply working fluid, and connects the other fluid chamber 8 to the drain path 2c. The working fluid in the fluid chamber 8 is discharged. Therefore, the power cylinder 6 is pressed to the right in the figure to assist in steering the steering wheel 11. On the other hand, when the power cylinder 6 is operated in this way, the pressure of the working fluid in the supply path 2c increases, but as described above, the pressure compensation valve 55 of the oil amount adjustment valve 51 is connected to its inlet port 63. The differential pressure across the orifice passage 53 of the orifice valve 54 is kept constant regardless of the applied fluid pressure and the flow rate of the inflowing working fluid. Therefore, as in the case described above, the flow rate of the working fluid flowing through the bypass passage 52 is determined by the orifice passage 53 having a passage area corresponding to the traveling speed. That is, the power cylinder 6 is supplied with working fluid at a flow rate obtained by subtracting the flow rate of the working fluid flowing through the bypass path 52 corresponding to the traveling speed from the constant flow rate of working fluid discharged by the flow control valve 35. Therefore, the power cylinder 6 is supplied with working fluid at a flow rate corresponding to the traveling speed, and generates a steering assist force corresponding to the traveling speed.

Furthermore, when a vehicle changes its running speed,
The vehicle speed detecting means 75 detects the traveling speed and outputs a signal corresponding to the traveling speed to the drive circuit 76, so the solenoid 74 is excited with an excitation current corresponding to the traveling speed. Therefore, the spool 70 is pressed with a pressing force corresponding to the traveling speed.
For example, if the vehicle speed increases, the pressing force of the spool 70 decreases, and the flow area of the orifice passage 53 increases, and as in the case described above, the differential pressure across the orifice passage 53 remains constant. Therefore, the flow rate of the working fluid flowing through the bypass passage 53 increases. That is, the flow rate of the working fluid supplied to the power cylinder 6 becomes smaller,
The steering assist force applied to the steering wheel 11 becomes smaller in accordance with the increased traveling speed. Moreover, when the traveling speed decreases, contrary to the above-mentioned case, the flow rate of the working fluid flowing through the bypass passage 52 decreases, and the flow rate of the working fluid supplied to the power cylinder 6 increases. The auxiliary force increases. In this way, the steering force of the steering wheel 11 is reduced depending on the running speed, that is, as the running speed becomes smaller, the steering force of the steering wheel 11 is reduced as the running speed becomes higher.
Since the steering assist force is smaller, the driver can enjoy better operability.

As explained above, according to this invention,
The structure consists of a pump that discharges working fluid, a supply path that sends the working fluid from the pump to the control valve, a drain path that circulates the working fluid from the control valve to the pump, and a drain path that discharges the working fluid from the pump to the supply path. a control valve that maintains a constant flow rate of working fluid; the control valve is operated by a steering wheel, the working fluid is transmitted to a power cylinder via the control valve, and the power cylinder is actuated to bias the steered wheels. In the device, there is a bypass passage that connects the supply passage and the drain passage, an orifice valve that is provided in the middle of the bypass passage and has an orifice passage with a variable flow passage area, and a pressure compensation that keeps the differential pressure before and after the orifice passage constant. A flow rate adjustment valve having a valve is provided, and the flow rate of the working fluid to be bypassed is adjusted to control the flow rate of the working fluid supplied to the control valve, so that the flow rate adjustment valve is miniaturized and the supply path is It is possible to control the steering force without being affected by the pressure of the working fluid, resulting in the effect that responsive and accurate control can be achieved.

In addition, a vehicle speed detection means for detecting the vehicle speed is provided,
If the flow rate adjustment valve is controlled by the signal output from the vehicle speed detection means, in addition to the above effects, the steering force of the steering wheel changes depending on the vehicle speed, thereby improving the operability of the vehicle.
Further, in addition to the vehicle speed detection means of the above embodiment, the steering force itself may be detected to further improve the accuracy of steering force control.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a part of a flow rate regulating valve of a conventional power steering device together with the power steering device and piping, and FIG. 2 is a schematic diagram showing a flow regulating valve of a power steering device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a part of the power steering device and piping together with a portion thereof in cross section. DESCRIPTION OF SYMBOLS 1... Pump, 2... Supply path, 3... Control valve, 5... Drain path, 6... Power cylinder, 11... Steering wheel, 35...
Flow control valve, 51...oil amount adjustment valve, 52...bypass path, 53...orifice passage, 54...orifice valve, 55...pressure compensation valve, 75...vehicle speed detection means.

Claims (1)

[Claims] 1. A pump that discharges working fluid, a supply path that supplies working fluid from this pump to a control valve, a drain path that circulates working fluid from the control valve to the pump, and a supply path from the pump. The control valve is equipped with a flow control valve that maintains a constant flow rate of working fluid discharged to the steering wheel, and the control valve is operated by the steering wheel, and the working fluid is transmitted to the power cylinder via the control valve, and the power cylinder is operated to control the steering wheel. In a power steering device that biases, a bypass path that connects the supply path and the drain path;
An orifice valve is provided in the middle of the bypass passage and has an orifice passage with a variable flow area, and a flow rate adjustment valve has a pressure compensation valve that keeps the differential pressure before and after the orifice passage constant. An oil amount regulating valve for a power steering device, characterized in that the flow rate of the working fluid supplied to the control valve is controlled by adjusting the flow rate. 2. The oil amount regulating valve for a power steering device according to claim 1, further comprising a vehicle speed detecting means for detecting vehicle speed, and the flow regulating valve is controlled by the vehicle speed detecting means.