JP3484503B2 - Power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering device used for an automobile or the like, and more particularly to a power steering device which is supplied from a pump to a control valve at a low load. The present invention relates to a power steering apparatus that saves energy by reducing flow rate. 2. Description of the Related Art FIG. 4 shows a power steering apparatus of this type. This is mainly composed of a pump 100 for discharging hydraulic oil, a reservoir 101, and a power cylinder 102 for power assisting steering operation.
A control valve 103 for restricting hydraulic oil supplied from a pump 100 to a power cylinder 102;
Measuring orifice 1 provided in the discharge passage 104
Opening and closing the bypass passage 106 in accordance with the differential pressure between before and after
A flow control valve 108 urged by a spring 107 in a direction to close the bypass passage 106 to control the discharge flow rate of the pump 100 to a constant flow rate, and the operating oil controlled at the constant flow rate to the flow rate via a control orifice 109. Control valve 10
8 to control the operation oil guided to the spring chamber 110 of the flow control valve 108 by the load pressure between the spring chamber 110 of the flow control valve 108 and the reservoir 101 in accordance with the load pressure. Spring chamber 11 of flow control valve 108
And a bypass control valve 111 having a variable throttle 111A for controlling the pressure of zero. Here, the bypass control valve 11
The first spool valve 112 is directly slidably fitted into the pump housing 100a of the pump 100, and
11A is a slit 112 formed in the spool valve 112.
a and an annular groove 11 formed in the pump housing 100a.
4. Therefore, in the neutral state of steering, since the load pressure is low, the spool valve 112 of the bypass control valve 111 is held at the left end in FIG. 4 by the spring 113, and the opening area of the variable throttle 111a is kept at the maximum. Therefore, the spring chamber 110 of the flow control valve 108 is connected to the reservoir 10 via the variable throttle 111a.
1 and the pressure drops, the flow control valve 108
Is displaced in a direction to open the bypass passage 106 more, and more hydraulic fluid discharged from the pump 100 is
1, the supply flow rate of the hydraulic oil supplied to the control valve 103 is reduced. Therefore, the energy loss of the pump power can be reduced. When a steering wheel (not shown) is rotated from this state, the opening area of one of the variable throttles of the control valve 103 is increased, and the opening area of the other variable throttle is reduced. Thereby, the pressure of the pump 100, that is, the load pressure gradually increases. When the load pressure becomes equal to or higher than a predetermined pressure, the spool valve 108 is moved rightward in FIG. 4 against the spring 113 to reduce the size of the variable throttle 111a. When the load pressure further increases, the variable throttle 111a is closed. As a result, the pressure in the spring chamber 110 of the flow control valve 108 is increased, and the flow control valve 108
The supply flow rate of the hydraulic oil supplied to the control valve 103 increases with an increase in the load pressure, and contributes to the assisting action. However, in FIG. 4, the pump discharge pressure acts on the left end of the spool valve 112 of the bypass control valve 111, and the pump suction pressure is guided to the right end. If the spool valve 112 is to be controlled with a short movement amount by the pressure difference between the left and right of the spool valve 112 (pump discharge pressure), the spring 113 of the bypass control valve 111 needs a large spring constant. When the spring constant of the spring 113 is increased, the influence of the variation in the height at which the spring is attached increases, and there is a problem that the selection of the spring constant is required for mass production, which increases the cost. Further, since the spool valve 112 is brought into direct sliding contact with the pump housing 100a, a spool valve 1 is provided.
Machining accuracy is required so that the clearance between the pump 12 and the pump housing is appropriate.
Is formed by counterboring the inner surface of the pump housing 100a, so that there is a problem that the processability is very poor. SUMMARY OF THE INVENTION A power steering apparatus according to the present invention has been made to solve the above-mentioned problem, and has a bypass control valve which is independently formed in a cartridge type. valve, and a sleeve member fitted into insertion hole fitting that is formed in the pump housing of the pump, and a spool valve which is inserted slidably fitted into the sleeve member, the spool valve with one end of the spool valve is seated A valve seat having an inner hole that is closed when one end of the spool is seated, the spool valve and the sleeve
A spring interposed between the valve seat and the biasing member to bias the spool valve away from the valve seat.The other end of the spool valve is connected to an upstream side of a control orifice, and the One end of the inner hole is connected to the downstream side of the control orifice, the other end of the inner hole of the valve seat is connected to the reservoir side, and the opening area of the inner hole of the valve seat is connected to the other end of the spool valve. The spool valve has a pressure receiving area difference that is smaller than the load pressure receiving side area. With the above arrangement, the bypass control valve is provided.
Since the pumps are configured independently as cartridges, the pump
Allowance is given to the clearance between the housing and the sleeve member
And the introduction or discharge of hydraulic oil
If an annular groove or the like is necessary for
And workability is improved. Also, the pressure upstream of the control orifice,
When the load pressure rises, the bypass control valve
The spool valve springs due to the difference in the pressure receiving area of the spool valve.
To the valve seat side against the urging force of
Restrict the passage formed between the end and the valve seat, and
Reduces the flow rate guided to the server and further increases the load pressure
Then, the spool valve sits on the valve seat, closing the inner hole,
The flow guided to the reservoir from the inner hole is set to zero. This
As a result, the flow rate to the control valve increases. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration of a hydraulic power steering device. The power steering device mainly includes a pump 10 driven by an automobile engine, a reservoir 11, a power cylinder 12 for power assisting a steering operation, and A rotary control valve 14 that operates in response to the rotation of the steering wheel 13 to throttle and control the hydraulic oil supplied from the pump 10 to the power cylinder 12. In FIG. 1, reference numeral 10a denotes a pump housing of the pump 10, and a valve housing hole 15 is formed in the pump housing 10a. A supply passage 16 communicating with the discharge port of the pump 10 and a bypass passage 17 communicating with the suction port of the pump 10 are opened in the valve storage hole 15 in a direction orthogonal to the axial direction of the valve storage hole 15.
The bypass passage 17 has an intake passage 18 that communicates with the reservoir 11. A union 19 is provided at one end of the valve housing hole 15.
Are screwed in a liquid-tight manner, and the union 19 has a supply hole 2
0 is formed, and a measuring orifice 21 is formed in the middle of the supply hole 20. An outlet 22 is formed at the outer end of the union 19.
Is connected to the control valve 14. A flow control valve 23 is slidably fitted in the valve housing hole 15. The flow control valve 23 is urged by a spring 26 inserted into a spring chamber 25 to resiliently contact the union 19. The communication between the supply passage 16 and the bypass passage 17 is shut off. One end is opened to the supply hole 20 on the downstream side of the measuring orifice 21 and the other end is connected to the pump housing 10.
The union 19 is formed with a communication passage 28 that opens into a communication hole 27 formed in the flow control valve 2 through the communication passage 28 and the communication hole 27 downstream of the measuring orifice 21.
3 is communicated with the spring chamber 25. A throttle member 30 having a control orifice 29 is press-fitted and fixed in the communication hole 27. As a result, part of the hydraulic oil downstream of the metering orifice 21 is guided to the spring chamber 25 via the control orifice 21, and the pressure around the metering orifice 21 acts on both end faces of the flow control valve 23. The flow control valve 23 moves in the axial direction according to the pressure difference, and adjusts the opening degree of the bypass passage 17 so as to keep the pressure difference constant. A valve hole 31 is formed in the flow control valve 23, and a valve seat 32 is screwed into one end of the valve hole 31. The valve hole 31 communicates with the spring chamber 25 via an introduction hole 33 formed in the valve seat 32. A ball valve 34 that comes into contact with the valve seat 32 is inserted into the valve hole 31. The ball valve 34 is urged by a spring 35 inserted into the valve hole 31 to
To resiliently close the inlet hole 33. Also,
The valve hole 31 has a radial hole 36 formed in the flow control valve 23.
Through the bypass passage 17. Here, a relief valve 37 is constituted by the introduction hole 33, the ball valve 34, and the spring 35. Thus, when the pressure in the spring chamber 25 of the flow control valve 23 reaches the relief pressure, the ball valve 34 moves leftward in FIG. 1 against the urging force of the spring 35, and bypasses the pressure in the spring chamber 25. Passage 17
To be missed. A fitting hole 38 is formed in the pump housing 10a in parallel with the valve housing hole 15 and out of phase with the communication hole 27. A cartridge type bypass control valve 39 is formed in the fitting hole 38. A stopper 40 is screwed into the opening end of the fitting hole 38 in a liquid-tight manner, and the stopper 40 prevents the bypass control valve 39 from moving in the axial direction. The cartridge type bypass control valve 39 includes a sleeve member 41 inserted in the insertion hole 38 and a spool valve slidably inserted in a slide hole 42 formed in the sleeve member 41. 43, a ball 44 fixed to the tip of the spool valve 43, a valve seat 45 on which the ball 44 sits, and a spring 46 for urging the spool valve 43 in a direction away from the valve seat 45. Is done. Here, a variable throttle 39a is formed between the ball 44 fixed to the spool valve 43 and the valve seat 45, and by changing the opening area of the variable throttle 39a, the spring space 25 of the flow control valve 23 is changed. The pressure is controlled. Also, the diameter D _A of the spool valve 43
The diameter of the bore 47 formed in the valve seat 45 and D _B is D _A>
It has a D _B, thereby loading the pressure receiving side area large cities on the side where the pressure upstream of the control orifice 29 is introduced in the spool valve 43, on the side where the pressure downstream of the control orifice 29 is introduced The load pressure receiving side area is small. The spring 46 is inserted between a locking member 48 press-fitted and fixed to the spool valve 43 and the sleeve member 38, and a spring chamber 49 in which the spring 46 is disposed is formed in the sleeve member 38. Small hole 50, annular groove 51,
It is connected to the communication hole 27 upstream of the control orifice 29 via a communication passage 52 formed in the pump housing 10a. In addition, an introduction groove 53 is formed in a tip surface of the spool valve 52 on the pump housing 10a side,
Due to the introduction groove 53, a pressure upstream of the control orifice 29 acts on the left end surface of the spool valve 43 in FIG. The internal chamber 54 in which the ball 44 is disposed is bypassed through a small hole 55 and an annular groove 56 formed in the sleeve member 38, a communication path 57 formed in the pump housing 10a, and the valve housing hole 15. It is connected to the passage 17. Further, the inner hole 47 of the valve seat 45 has a cross groove 58 formed on the end face of the valve seat 45 on the stopper 40 side, an annular groove 59 formed on the sleeve member 41, and the pump housing 10.
The communication orifice 27 is connected to the communication hole 27 on the downstream side of the control orifice 29 through a communication passage 60 formed in a. The control valve 14 includes a first bridge circuit 6
1 and a second bridge circuit 62. The first bridge circuit 61 includes four flow paths L1, L2, L connected to the pump 10 and the reservoir 11, respectively.
Variable apertures V1, V2, V3, V4 are provided at 3, L4, and these variable apertures V1, V2, V3, V4 are configured as semi-center open valves. The second bridge circuit 62 is connected in parallel to the first bridge circuit 61 and has four flow paths L5, L6, which are connected to both the oil chambers of the pump 10 and the power cylinder 12 and the reservoir 11, respectively. Variable aperture V5 for L7 and L8,
V6, V7, and V8 are provided. Of these variable throttles, the variable throttles V5 and V6 connected to the pump 10 side are configured as center close valves.
The variable throttles V7 and V8 connected to the first side are configured as center open valves. Next, the operation will be described based on the above configuration. When the pump 10 is driven by the vehicle engine, hydraulic oil is supplied from the discharge port of the pump 10 to the supply passage 16. The supplied hydraulic oil is guided to the pressure chamber 24, and is supplied from the pressure chamber 24 through the metering orifice 21 to the control valve 14 from the outlet 22 of the union 19. After the hydraulic oil passes through the measuring orifice 21, the communication passage 28, the communication hole 2
7, the spring chamber 25 of the flow control valve 23 through the control orifice 29, and the communication hole 27 on the upstream side of the control orifice 29.
Are supplied to the annular groove 51 of the bypass control valve 39 through the communication passage 52 connected to the control valve orifice, and to the annular groove 59 of the bypass control valve 39 through the communication passage 60 connected to the communication hole 27 downstream of the control orifice 29. . In the bypass control valve 39, hydraulic oil is supplied from the annular groove 51 to the spring chamber 49 via the small hole 50, while the valve seat 4 is supplied from the annular groove 59 via the cross groove 58.
5 is supplied to the inner hole 47 formed. The hydraulic oil is guided from the inner hole 47 to the bypass passage 17 via the variable throttle 39a, the inner chamber 54, the small hole 55, the annular groove 56, the communication passage 57, and the valve housing hole 15. That is, after the working oil is controlled to a constant flow rate by the metering orifice 21 and the flow rate control valve 23, the pilot flow rate q supplied to the bypass passage 17 through the variable throttle 39a of the bypass control valve 39, and the control flow rate It is distributed to the supply flow rate Q supplied to the valve 14. In the neutral state of steering, the center-closed variable throttles V5 and V6 of the second bridge circuit 62 are closed, and the pump 10
The discharged hydraulic oil is discharged to the reservoir 11 through the semi-center open type variable throttles V1, V2, V3, V4 of the first bridge circuit 61. Further, both oil chambers of the power cylinder 12 are connected to the reservoir 11 via center-open type variable throttles V7 and V8, and are maintained in a low pressure state. As a result, manual steering is performed near the neutral position, and the neutral rigidity of the steering wheel 13 is increased. At this time, since the load pressure P (the pressure on the downstream side of the metering orifice) is low, the differential pressure at the control orifice 29 is small. Therefore, the variable throttle 39a of the bypass control valve 39 is fully opened, and the pilot flow rate q ₁ Is supplied to the bypass passage 17, so that the variable throttle 39a
The spring chamber 25 of the flow control valve 23 is
7, the flow control valve 23 is moved in a direction to open the bypass passage 17 more, and the pump 1
Hydraulic oil discharged from 0 is more bypassed to the bypass passage 17 and supplied to the suction port of the pump 10.
Thus, the supply flow rate Q of the hydraulic fluid supplied to the control valve 14 is reduced to a minimum flow rate Q _A of FIG. 3. This allows
Energy loss of pump power can be reduced. From this state, the steering wheel 13
Is rotated, the opening area of the variable apertures V1, V4 or the variable apertures V2, V3 in the first bridge circuit 61 is reduced in accordance with the rotation direction of the steering wheel 13, while the second bridge circuit 61 In 62, the aperture areas of the variable stops V5 and V8 are enlarged, and the variable stops V
6. The opening area of V7 is reduced. As a result, the load pressure P gradually increases. [0025] The load pressure P rises, the differential pressure is increased in the control orifice 29, when the differential pressure predetermined pressure (load pressure P shown in FIG. 3 is a differential pressure when the P _A) becomes, the spool valve 43 moves rightward in FIG. 1 against the urging force of the spring 46 to reduce the size of the variable throttle 39a. Further, when the differential pressure across the control orifice 29 load pressure P rises to the pressure P _B increases, moved further spool valve 43, will be variable throttle 39a is closed, as shown in FIG. 2, the bore The pilot flow rate q guided from 54 to the bypass passage 17 is set to zero. As a result, the pressure in the spring chamber 25 of the flow control valve 23 is increased, so that the flow control valve 23 is displaced in a direction to narrow the bypass passage 17, and the supply flow rate Q of the working oil supplied to the control valve 14 is reduced as shown in FIG. Maximum supply flow Q shown in
Increases to _B and contributes to assist action. As described above, since the bypass control valve 39 is formed independently of a cartridge type, the clearance between the pump housing 10a and the sleeve member 41 can be made wider, and furthermore, the annular groove 5 can be formed.
Since 1, 56 and 59 are formed in the sleeve member 41, it is not necessary to form an annular groove in the pump housing 10a, and the workability is improved. Further, the load control pressure receiving area at both ends of the spool valve 43 of the bypass control valve 39 is provided with an area difference, and the bypass control valve 39 is controlled by the differential pressure across the control orifice 29. The spring constant of the spring 46 can be reduced, the influence of the variation in the height at which the spring is mounted is reduced, and accurate flow control can be performed. Although the cartridge-type bypass control valve 39 shown in FIG. 1 is of a variable-throttle ball poppet type, the present invention is not limited to this ball-poppet type, and various types of variable throttle structures are applicable. Is done. Further, in the above embodiment, the control valve 14
The variable apertures V1 to V8 of the first bridge circuit 61 and the second bridge circuit 62 may all be center open valves, and various rotary valve structures can be applied. As described above, according to the present invention, since the bypass control valve is independently formed in a cartridge type, the clearance between the pump housing and the sleeve member can have a certain width. When forming an annular groove or the like, it can be formed in the sleeve member, and there is no need to form an annular groove on the pump housing side, and workability is improved. In addition, the bypass control valve has a pressure receiving area difference and is controlled by the differential pressure before and after the control orifice, so even when controlling the spool valve with a small movement amount, the spring constant of the spring of the bypass control valve is reduced. Therefore, the influence of the variation in the height at which the spring is mounted is reduced, and accurate flow control can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of a power steering device showing an embodiment of the present invention. FIG. 2 is a graph showing pilot flow rate characteristics depending on load pressure. FIG. 3 is a graph showing a supply flow rate characteristic with respect to a load pressure. FIG. 4 is a diagram showing a conventional power steering device. DESCRIPTION OF SYMBOLS 10 Pump 10a Pump housing 11 Reservoir 12 Power cylinder 16 Supply passage 17 Bypass passage 21 Metering orifice 23 Flow control valve 25 Spring chamber 29 Control orifice 39 Bypass control valve 41 Sleeve member 43 Spool valve 44 Ball 45 Valve seat 46 Spring 47 Inner hole 49 Spring chamber 50 Small hole 51 Annular groove 58 Cross groove 59 Annular groove L1 to L8 Flow paths V1 to V8 Variable throttle

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takeya Kato 1-1-1 Asahi-cho, Kariya-shi, Aichi Prefecture Inside Toyota Koki Co., Ltd. (56) References JP-A-7-81593 (JP, A) JP-A Sho JP-A-6-8840 (JP, A) JP-A-58-209656 (JP, A) JP-A-57-113988 (JP, A) JP-A-4-27666 (JP, A) A) Japanese Utility Model Application Hei 6-40532 (JP, U) Japanese Utility Model Application Hei 1-166864 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B62D 5/06-5/32

Claims (1)

(57) [Claim 1] A control valve in which variable throttles are respectively provided in flow paths connected to both oil chambers and a reservoir of a pump and a power cylinder, and provided in a discharge passage of the pump. A flow control valve that opens and closes a bypass passage in accordance with the differential pressure across the measured orifice and controls the discharge flow rate of the pump to a predetermined flow rate; and controls the flow rate of the working oil controlled to the predetermined flow rate through a control orifice. A power steering apparatus comprising: a bypass control valve that guides a spring chamber of a control valve and controls a pressure of the spring chamber of the flow control valve between the spring chamber of the flow control valve and a reservoir. Independently configured as a cartridge, this bypass control valve is a sleeve member that is inserted into an insertion hole formed in the pump housing of the pump, A spool valve which is fitted slidably sleeve member, a valve seat inner bore is formed which is closed when the end of the spool valve is seated one end of the spool valve is seated, the spool valve And between the sleeve member
A spring that is interposed and biases the spool valve away from the valve seat, connects the other end of the spool valve to an upstream side of the control orifice, and has one end of an inner hole of the valve seat. Is connected to the downstream side of the control orifice, the other end of the inner hole of the valve seat is connected to the reservoir side, and the opening area of the inner hole of the valve seat is set to the load pressure receiving side of the other end of the spool valve. A power steering device characterized in that the spool valve has a pressure receiving area difference that is smaller than the area.