JPH11157458A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device that is able to miniaturize the device as a whole, and also inexpensive in manufacturing cost. SOLUTION: In this power steering system, a control valve 20, taking charge of a supply of hydraulic fluid to a power cylinder, is installed. Likewise a converting mechanism converting the steering torque to be inputted into an input shaft 1 to the displacement of this operating stick 54 which is capable of operating this control valve 20. A directional control valve 63 selecting the supply of hydraulic fluid to a cylinder chamber on one side or a cylinder chamber on the other of the power cylinder according to the direction of the steering torque, while taking charge of the discharge of the hydraulic fluid from these cylinder chambers is installed in an interval between the control valve 20 and the power cylinder. In succession, a movable member 55 of the converting mechanism is linked with an output shaft 2 as shiftable in the axial direction but relatively unrotatable, linking the operating stick 54 to this movable member 55. Then, the directional control valve 63 is formed in space between the input shaft 1 and the movable member 55.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device for an automobile or the like, and more particularly to a power steering device having a control valve of a type that shuts off supply of hydraulic oil to a power cylinder at a neutral position of a steering operation.

[0002]

2. Description of the Related Art A power steering apparatus of this type is disclosed in WO 95/11158.

[0003] The conventional power steering apparatus is a power steering apparatus for supplying and discharging hydraulic oil to and from a power cylinder in accordance with a steering torque input to an input shaft of a steering mechanism to obtain a steering assisting force. It has a power cylinder that exerts power and a control valve that controls supply of hydraulic oil to the power cylinder and shuts off supply of hydraulic oil to the power cylinder at a neutral position of the steering operation. The control valve is provided in a pair, and is selectively operated in a leftward or rightward steering operation of the steering mechanism.

That is, in the conventional power steering apparatus, one of the control valves is opened in a leftward or rightward steering operation of a steering mechanism, for example, in a leftward steering operation, and hydraulic oil is supplied to the power cylinder. The steering oil is guided to one of the cylinder chambers to obtain a steering assisting force for the steering operation in the left direction, while in the steering operation in the right direction, the other control valve is opened, and the hydraulic oil is supplied to the other cylinder chamber of the power cylinder. As a result, a steering assisting force for the rightward steering operation is obtained.

[0005]

However, in the prior art, two control valves, a control valve that opens when turning leftward and a control valve that opens when turning rightward, are used. Since the valve is provided, not only the whole apparatus is enlarged, but also the number of parts is large, and the manufacturing cost may increase.

The present invention has been devised in view of the above-mentioned conventional circumstances, and has as its object to provide a power steering device which can reduce the size of the entire device and can be manufactured at low cost.

[0007]

SUMMARY OF THE INVENTION In view of the above, the present invention has an output shaft connected to an input shaft of a steering mechanism so as to be rotatable relative to the input shaft, and responds to a steering torque input to the input shaft. In a power steering apparatus for supplying and discharging hydraulic oil to and from a power cylinder to obtain a steering assisting force, the power steering apparatus controls supply of hydraulic oil to the power cylinder in accordance with a steering torque input to the input shaft, and a neutral position of the steering operation. A control valve of a type that shuts off the supply of hydraulic oil to the power cylinder, and a conversion mechanism that includes an operation rod that can operate the control valve and that converts a steering torque input to the input shaft into a displacement of operation means. Provided between the control valve and the power cylinder, when the supply of hydraulic oil is switched to one or the other cylinder chamber of the power cylinder in accordance with the direction of the steering torque input to the input shaft. In, and a directional control valve that controls the discharge of the working oil from these cylinder chamber, wherein the conversion mechanism, the output shaft or input shaft, an axially movable,
A movable member to which the operating rod is connected, and which is connected between the movable member and the input shaft or the output shaft opposed to the movable member, is provided so as not to be relatively rotatable. Motion converting means for converting the relative rotation with respect to the input shaft or the output shaft into the axial movement of the movable member, wherein the direction switching valve is rotatable relative to the movable member and the movable member. It is configured to be formed between the input shaft and the output shaft.

According to a second aspect of the present invention, in the configuration of the first aspect, the movable member is accommodated in a housing accommodating the input shaft so as to be rotatable, and the operation rod is movable. A structure in which a base end side is connected to a member, a front end side penetrates the housing and operably extends the control valve, and an intermediate portion between the base end side and the front end side is pivotally connected to the housing. It is.

According to a third aspect of the present invention, in the configuration of the first aspect of the present invention, the motion converting means includes the movable member and an input shaft or an output shaft facing the movable member. It is provided with a pair of inclined surfaces provided on one of them and inclined in the rotating direction, and a projection provided on one of the other and in contact with the pair of inclined surfaces.

According to a fourth aspect of the present invention, in the configuration of the first aspect, the control valve includes a spool valve that is moved in the axial direction by operating means of a conversion mechanism. The configuration is such that the spool valve is disposed substantially parallel to the input shaft.

According to a fifth aspect of the present invention, in the configuration of the first aspect, the directional control valve is formed between an outer periphery of the input shaft or the output shaft and an inner periphery of the movable member. Configuration.

According to a sixth aspect of the present invention, in the configuration of the second aspect, the direction switching valve is formed between an outer periphery of the input shaft or the output shaft and an inner periphery of the movable member. And the control valve is in contact with the housing.

According to a seventh aspect of the present invention, in the configuration of the first aspect, a cutoff valve is provided to give an assisting force to the operation of the control valve by the operating rod of the conversion mechanism. The cutoff valve is provided at a position facing the control valve with the operation rod of the conversion mechanism interposed therebetween.

In such a configuration, the control valve is operated by the operation rod of the conversion mechanism in accordance with the steering torque input to the input shaft of the steering mechanism. That is, the movable member of the conversion mechanism moves according to the steering torque, and the operating rod connected to the movable member operates the control valve. Further, in the invention according to claim 2, the distal end side of the operation rod moves in a direction opposite to the movement of the base end side linked to the movable member to operate the control valve. In this case, the control valve is opened according to the magnitude of the steering torque, regardless of the direction of the steering torque.

When the control valve is opened, hydraulic oil is guided from the control valve to the power cylinder via the direction switching valve.

The directional control valve is formed between a movable member and an input shaft or an output shaft which is rotatable relative to the movable member. To switch the supply of hydraulic oil to one cylinder chamber or the other cylinder chamber of the power cylinder.

As a result, a steering assisting force by the power cylinder is obtained for a leftward or rightward steering operation of the steering mechanism.

Here, there is one control valve for controlling the supply of hydraulic oil to the power cylinder, and this one control valve is irrespective of the steering direction, that is, when it is steered to the left and to the right. In both cases, the steering is performed according to the steering torque.

Further, since the operating rod for operating the control valve is connected to a movable member constituting the direction switching valve,
Both the control valve and the direction switching valve are operated by the movable member that moves in accordance with the steering torque.

Therefore, the power steering apparatus can be reduced in size, and the manufacturing cost can be reduced.

According to the second aspect of the present invention, since the operating rod of the conversion mechanism is pivotally connected to the housing, by selecting the pivot connection point, the so-called lever ratio is selected. Can be selected, it is possible to select the amount of movement on the distal end side with respect to the movement on the proximal end side of the operation rod connected to the movable member.

According to the third aspect of the present invention, since the motion converting means is constituted by an inclined surface and a projection, the relative movement between the movable member and the input shaft or the output shaft is simple. Regardless of the direction of rotation, the movable member can be moved in a fixed direction according to the steering torque.

According to the fourth aspect of the present invention, since the control valve can be disposed substantially in parallel with the input shaft, the control valve is disposed radially outward as compared with a case where the control valve is disposed in a substantially right angle direction. By reducing the number of protrusions, the size of the entire apparatus can be reduced.

According to the fifth aspect of the present invention, since the direction switching valve can be constituted by a so-called rotary valve, the radially outwardly protruding portion is reduced to reduce the size of the entire apparatus. Can be.

In the invention according to the sixth aspect, the passage of the hydraulic oil between the direction switching valve and the control valve can be formed in the housing. can do.

In the invention according to claim 7, so-called cutoff characteristics can be imparted to the hydraulic characteristics of the control valve, and the cutoff valve is arranged in series with the control valve. The number of radially outwardly projecting portions can be reduced, and the size of the entire apparatus can be reduced.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an explanatory view of a power steering apparatus showing an embodiment of the present invention, and is a drawing including a cross-sectional view of a control valve and a direction switching valve. FIG. 2 is an enlarged cross-sectional view showing a main part of FIG. FIG. 3 is an explanatory view including a cross-sectional view taken along line AA of FIG.
FIG. 5 is a sectional view taken along the line BB in FIG. 1, and FIG. 5 is a diagram showing the relationship between the steering torque (T) input to the input shaft and the operating oil pressure (P) for generating the steering assisting force, using the vehicle speed as a parameter. is there.

In FIG. 1, reference numeral 1 denotes a hollow input shaft. A steering wheel (not shown) is connected to the input shaft 1 to input a steering torque. An output shaft 2 is connected to the input shaft 1 so as to be rotatable relative to the input shaft 1. The input shaft 1 and the output shaft 2 include a valve housing 3a and a gear housing 3b.
And is rotatably accommodated in a housing 3 comprising: Reference numerals 4, 5, and 6 denote bearings that support the input shaft 1 and the output shaft 2, and reference numeral 7 denotes a seal member that seals between the output shaft 2 and the housing 3.

The output shaft 2 is provided with a pinion shaft 8 which meshes with a rack shaft 9 for steering a steering link (not shown).

Reference numeral 10 denotes a rack support. The rack support 10 presses the rack shaft 9 from its rear side toward the pinion shaft 8 by the spring force of a spring 11, whereby the rack shaft 9 and the pinion shaft 8 are pressed. A smooth steering feeling can be obtained by removing the meshing gap with the steering wheel. A plug 12 also serves as a spring receiver for the spring 11.

A power cylinder 13 is attached to the rack shaft 9, and the power cylinder 13 is mounted on the rack shaft 9.
And a pair of cylinder chambers 15L and 15R facing each other on both sides of the piston 14 attached to the piston.

Reference numeral 16 denotes a torsion bar inserted into the hollow interior of the input shaft 1. The torsion bar 16 has an appropriate torsional elasticity. The ends are connected to the output shaft 2 by serrations 18. Thereby, the output shaft 2
Is connected to the input shaft 1 via the torsion bar 16,
The torsion bar 16 can be relatively rotated with respect to the input shaft 1 by being twisted.

A control valve 20 controls the supply of hydraulic oil to the power cylinder 13 in accordance with the steering torque input to the input shaft 1. The control valve 20 is disposed in contact with the housing 3 and is configured as follows.

That is, reference numeral 24 denotes a body of the control valve 20 which has a spool valve housing hole 2 substantially parallel to the input shaft 1.
5 are formed. One end of the spool valve housing hole 25 is sealed by a plug 26, and the inside thereof is
A large diameter portion 25a is formed on one end (sealing end side), and a small diameter portion 25b is formed on the other end. Reference numeral 27 denotes a retaining ring for controlling the removal of the plug 26.

Reference numeral 28 denotes a first spool valve slidably housed in the spool valve housing hole 25. The first spool valve 28 connects the inside of the spool valve housing hole 25 to a first oil chamber 29 on one end side. It is divided into the second oil chamber 30 on the end side. Also,
The first spool valve 28 has a body portion whose diameter is reduced, and defines a third oil chamber 31 in a substantially central portion of the spool valve housing hole 25.

A section of the third oil chamber 31 with respect to the first oil chamber 29 is formed by a poppet portion 28a formed by tapering and expanding the first spool valve 28 on the large diameter portion 25a side of the spool valve housing hole 25. Is the large diameter portion 2 of the spool valve housing hole 25.
This is achieved by contacting a step 25c between the small oil tank 5a and the small diameter part 25b to cut off the communication between the first oil chamber 29 and the third oil chamber 31. Therefore, the first oil chamber 29 and the third oil chamber 29
The first spool valve 28 is provided between the first oil chamber 29 and the oil chamber 31.
The poppet 28a moves to the side and the poppet 28a is separated from the step 25c to allow communication.

The section of the third oil chamber 31 with respect to the second oil chamber 30 is achieved by a seal ring 32 provided on the outer periphery of the body of the first spool valve 28.

Further, a concave tapered surface 35 is formed at an end of the first spool valve 28 on the second oil chamber 30 side.

Reference numeral 36 denotes a communication oil passage which connects the first oil chamber 29 and the second oil chamber 30. The communication oil passage 36 is formed in the first spool valve 28 in this embodiment. That is, the communication oil passage 36 is formed to penetrate the first spool valve 28 in the axial direction.

Reference numeral 37 denotes a second spool valve slidably accommodated in the other end of the spool valve accommodation hole 25. In this embodiment, the second spool valve 37 has a tapered surface 3 having a convex shape on one end side toward the first spool valve 28 side.
8 and a hemispherical spherical surface 39 is formed on the other end side. The convex tapered surface 38 formed at one end of the second spool valve 37 contacts the concave tapered surface 35 of the first spool valve 28, and the tip of the other end where the hemispherical surface 39 is formed is: The projection protrudes into a through-hole 40 formed in the body 24 substantially perpendicular to the spool valve housing hole 25, and is in contact with an operation rod of a conversion mechanism described later in detail. The through hole 4
The open end of 0 is sealed with a plug plate 41.

Reference numeral 42 denotes a supply spring accommodated in the first oil chamber 29. One end of the supply spring 42 contacts the plug 26, and the other end contacts the first spool valve 28.
The first spool valve 28 is biased toward the second oil chamber 30. Accordingly, in the first spool valve 28, the poppet portion 28a is in contact with the step portion 25c of the spool valve accommodating hole 25 in the normal state, and the communication between the first oil chamber 29 and the third oil chamber 31 is shut off.

Reference numeral 43 denotes a discharge spring housed in the second oil chamber 30. The discharge spring 43 has one end in contact with the first spool valve 28 and the other end in contact with the second spool valve 37. The two spool valve 37 is urged in a direction to protrude from the valve body 20. That is, the discharge spring 43 connects the second spool valve 37 to the first spool valve 28.
The first spool valve 28 and the convex tapered surface 38 of the second spool valve 37 do not come into contact with each other. For this reason, in the normal state, the second spool valve 37 does not close the communication oil passage 36 formed in the first spool valve 28 at the end on the second oil chamber 30 side, and opens the communication passage 36. State.

The first oil chamber 29 of the control valve 20 has a passage 44
Through a directional control valve, which will be described in detail later.
The second oil chamber 30 is connected to the drain passage 4 through the oblique hole 45.
6, the third oil chamber 31 is in communication with a supply passage 47 for hydraulic oil.

Reference numeral 53 denotes a conversion mechanism.
It has an operating rod 54 capable of operating the control valve 20, and converts a steering torque input to the input shaft 1 into a displacement of the operating means 54. The conversion mechanism 53 includes a movable member 55 that is movable in the axial direction with respect to the output shaft 2 housed in the housing 3 and is connected to the output shaft 2 so that the movable member 55 cannot rotate relative to the output shaft 2. It has a motion converting means 56 provided between the movable member 55 and an opposing surface facing the movable member 55 and converting relative rotation between the movable member 55 and the input shaft 1 into axial movement of the movable member 55. Further, an operation rod 54 capable of operating the control valve 20 is connected to a movable member 55 as described later in detail.

The movable member 55 has a hollow cylindrical shape and is arranged on the outer peripheral side of the input shaft 1 with the input shaft 1 inserted into the hollow interior, and a flange 57 formed on the input shaft 1 and extending outward in the radial direction. And the output shaft 2, and are connected to the output shaft 2 so as to be axially movable and relatively non-rotatable by a pin 58 provided in the output shaft 2 in the axial direction. The movable member 55 is constantly urged toward the flange 57 of the input shaft 1 by a spring member 59 having one end contacting the seal member 7.

The motion converting means 56 includes a pair of inclined surfaces 60 provided on the movable member 55 and inclined in the rotational direction, and a sphere 61 as a projection in contact with the inclined surface 60. The shaft 1 is provided on a facing surface facing the movable member 55, that is, on an end surface of the flange 57 (FIG. 4).
reference). As a result, the steering torque is input to the input shaft 1 and the relative rotation occurs between the input shaft 1 and the output shaft 2, so that the ball 61 pushes the inclined surface 60. It is possible to move in the axial direction against the spring force of the spring member 59, that is, in the direction away from the end face of the flange 57. In this case, since the inclined surface 60 is provided in a pair in the rotation direction of the movable member 55, the movable member 55 is moved in one direction even if the relative rotation of the input shaft 1 and the output shaft 2 is in the left or right direction. Will be moved to.

The operating rod (operating means) 54 has a base end 54.
The side a is connected to the movable member 55, the end 54 b extends through the housing 3, and the second spool valve 3 of the control valve 20
7 is in contact with the hemispherical surface 39. The operation rod 54
Is supported by a spherical bearing 62 attached to the housing 3 at an intermediate portion between the base end 54a side and the distal end 54b side, and is pivotally connected to the housing 3 by the spherical bearing 62. For this reason, the operation rod 54 can swing about the spherical bearing 62 as a fulcrum,
When the base end 54a side connected to the movable member 55 moves upward in FIG. 1, the front end 54b side moves downward to operate the control valve 20.

Reference numeral 63 denotes the control valve 20 and the power cylinder 1
The direction switching valve 63 is provided between the outer periphery of the input shaft 1 and the inner periphery of the movable member 55 in this embodiment, as best shown in FIG. It is formed as a so-called rotary valve between them.

The direction switching valve 63 switches the supply of hydraulic oil to one of the cylinder chambers 15L or the other cylinder chamber 15R of the power cylinder 13 in accordance with the direction of the steering torque input to the input shaft 1. It is responsible for discharging hydraulic oil from the cylinder chambers 15L and 15R.

That is, a depression 64 is formed on the outer periphery of the input shaft 1.
65 are formed at regular intervals in the circumferential direction,
On the inner periphery of 5, recesses 66, 67 are formed between the recesses 64, 65 of the input shaft 1 and are arranged at regular intervals in the circumferential direction, and these recesses 64, 65, 66, 67 are formed. Between,
Restrictors 68a, 68b, 69 constituting the direction switching valve 63
a and 69b are formed.

The depression 64 communicates with a peripheral groove 71 formed on the outer periphery of the movable member 55 via a passage 70. The circumferential groove 71 is provided with the control valve 20 through the through hole 40 and the passage 44.
Of the control valve 2 in the recess 64.
Hydraulic oil in the first oil chamber 29 can be guided. The proximal end 54a of the operating rod 54 is inserted into the peripheral groove 71, whereby the proximal end 54a of the operating rod 54 is connected to the movable member 55.

The circumferential groove 71 is formed with two diameters, and the diameter d1 on the side close to the spring member 59 (the lower side in FIGS. 1 and 2) corresponds to the flange 5 of the input shaft 1.
7 (the upper side in FIGS. 1 and 2) is formed larger than the diameter d2. Therefore, when high-pressure hydraulic oil is introduced into the recess 64, the movable member 55 tends to be urged toward the spring member 59 due to the difference in pressure receiving area.

The recess 65 communicates with a low-pressure portion in the housing 3 through a passage 72 and a gap between the inner circumference of the input shaft 1 and the outer circumference of the torsion bar 16.
It communicates with the drain passage 46 through the inside.

The depression 66 communicates with a peripheral groove 74 formed on the outer periphery of the movable member 55 through a passage 73.
4, one cylinder chamber 15 of the power cylinder 13
L.

The recess 67 communicates with a peripheral groove 76 formed on the outer periphery of the movable member 55 through a passage 75,
6, the other cylinder chamber 15 of the power cylinder 13
It communicates with R.

Further, seal rings 77, 78, 79, 80 are disposed on both sides of the peripheral grooves 71, 74, 76, whereby the peripheral grooves 71, 74, 76 are liquid-tightly partitioned. ing.

Numeral 81 denotes a cutoff valve which gives an assisting force to the operation of the control valve 20 by the control rod 54 of the conversion mechanism 53.
The cutoff valve 81 is provided at a position facing the control valve 20 with the control rod 54 of the conversion mechanism 53 interposed therebetween.

The cutoff valve 81 includes a bottomed cylindrical cylinder 83 housed and fixed in a cylinder housing hole 82 formed in the body 24 common to the control valve 20.
And a plunger 84 slidably housed in the housing 3. The cylinder housing hole 82 is open to the through hole 40, and the tip of the plunger 84 protrudes into the through hole 40, and the second spool valve 3 of the control valve 20 is sandwiched by the operation rod 54.
7.

A pressure chamber 85 is formed between the bottom of the bottomed cylindrical cylinder 83 and the plunger 84, and the pressure in the pressure chamber 85 causes the plunger 84 to project into the through hole 40. It has become. On the other hand, a cylindrical plug 8 is provided at the end of the cylinder 83 on the side of the through hole 40.
6 is screwed and fixed, and a spring member 87 is provided between the plug 86 and the plunger 84 to urge the plunger 84 toward the pressure chamber 85. In a state where the pressure in the pressure chamber 85 is smaller than the spring force of the spring member 87 and in a state where both are in opposition, the tip of the plunger 84 does not contact the operating rod 54 of the conversion means 53,
They are facing each other with a predetermined gap.

The hydraulic oil in the first pressure chamber 29 of the control valve 20 is led into the pressure chamber 85 of the cutoff valve 81. That is, the passage 44 communicating with the first pressure chamber 29 of the control valve 20 is connected to the pressure chamber 85 through the peripheral groove 88 formed on the outer periphery of the cylinder 83 and the through hole 89 opened at the bottom of the peripheral groove 88. The hydraulic oil in the first pressure chamber 29 of the control valve 20 is guided into the pressure chamber 85 by the communication.

The inside of the cylinder 83 communicates with the inside of the cylinder housing hole 82 through the through holes 90 and 91 except for the inside of the pressure chamber 85, and further, through the oblique hole 92, the low pressure inside the housing 3. And a drain passage 46 through the inside of the housing 3.

Reference numeral 95 denotes a hydraulic pump for supplying hydraulic oil to the supply passage 47. In the middle of the supply passage 47, there is provided a check valve 96 for allowing the flow of hydraulic oil from the hydraulic pump 95 to the third oil chamber 31 side of the control valve 20 and preventing the flow in the reverse direction. An accumulator 97 capable of holding the pressure in the supply passage 47 at a predetermined pressure is connected to the supply passage 47 downstream of the check valve 96.

Reference numeral 98 denotes a motor for rotating and driving the hydraulic pump 95. The motor 98 is driven and stopped based on a detection signal of a pressure switch 99 for monitoring the pressure in the supply passage 47 downstream of the check valve 96. Is controlled.

Incidentally, reference numeral 100 denotes a reservoir of hydraulic oil.

In this configuration, when a steering wheel (not shown) connected to the input shaft 1 is steered and a steering torque is input to the input shaft 1, the steering torque is output via the torsion bar 16. Transmitted to shaft 2,
A steering link (not shown) is steered through the rack shaft 9.

At this time, when the ground resistance of the wheels (not shown) is large, the torsion bar 16 is twisted, and the relative rotation between the input shaft 1 and the output shaft 2 occurs.

The relative rotation between the input shaft 1 and the output shaft 2 causes the control valve 20 and the direction switching valve 63 to operate, thereby supplying and discharging hydraulic oil to and from the power cylinder 13, and assisting the steering by the operating hydraulic pressure. Power will be gained,
This will be described step by step.

First, the operating oil in the supply passage 47 is supplied to an accumulator 97 provided downstream of the check valve 96.
And is constantly maintained at a predetermined pressure.
That is, the pressure of the hydraulic oil in the supply passage 47 is monitored by the pressure switch 99.
When the internal pressure is lower than the predetermined pressure, the motor 98 is rotated based on the detection signal of the pressure switch 99 and the hydraulic pump 95 is driven to rotate, so that the supply passage 4
The pressure of the hydraulic oil in 7 is increased. On the other hand, when the pressure in the supply passage 47 reaches a predetermined pressure, the pressure switch 99 detects this, and the motor 98 and the hydraulic pump 95
Stop the rotational drive of. Therefore, the control valve 20
, The hydraulic oil at a predetermined pressure is always guided into the third oil chamber 31.

At this time, in a state where relative rotation does not occur between the input shaft 1 and the output shaft 2, that is, in a neutral position of the steering operation, the movable member 55 of the conversion mechanism 53 has a spring member 59.
And the ball 61 is not in contact with the pair of inclined surfaces 60 of the motion converting means 56 (see FIG. 4), the operating rod 54 is in the neutral position shown in FIG.
Do not operate 0. Therefore, the first spool valve 28 and the second spool valve 37 of the control valve 20 are both in the neutral state shown in FIG. 1, and the supply of the hydraulic oil to the direction switching valve 63 and the power cylinder 13 is cut off. is there.

That is, the first spool valve 2 of the control valve 20
8 is a normal state, and partitions a first oil chamber 29, a second oil chamber 30, and a third oil chamber 31 formed in the spool valve housing hole 25 by the first spool valve 28, respectively.
Mutual communication between the oil chambers is blocked. That is, the first spool valve 28 is urged toward the second oil chamber 30 by the supply spring 42, and the first spool valve 2
8 is the stepped portion 2 of the spool valve accommodating hole 25.
5c, thereby preventing communication between the first oil chamber 29 and the third oil chamber 31. Further, a seal ring 32 seals between the second oil chamber 30 and the third oil chamber 31. That is, the third oil chamber 31 communicating with the supply passage 47 of the hydraulic oil is connected to the first oil chamber 29 communicating with the circumferential groove 71 of the direction switching valve 63 and the second oil chamber 30 communicating with the drain passage 46. Therefore, the operating oil supplied to the third oil chamber 31 is not supplied to any of the direction switching valve 63 and the drain passage 46.

Although the second spool valve 37 is urged by the discharge spring 43 in a direction to protrude from the body 24, the hemispherical surface 39 at the end thereof is in the normal state and the operation rod 54 of the conversion mechanism 53 is used. Accordingly, the communication oil passage 36 that connects the first oil chamber 29 and the second oil chamber 30 is maintained in a communication state. That is, the second spool valve 37 is moved by the discharge spring 43 to the valve body 20.
, The second spool valve 37 is separated from the first spool valve 28, and the concave tapered surface 35 of the first spool valve 28 and the convex shape of the second spool valve 37. The state is such that the tapered surface 38 does not make contact. Therefore, the second spool valve 37 opens the communication passage 36 formed in the first spool valve 28 without closing the communication oil passage 36 at the end on the second oil chamber 30 side. Therefore, the first direction communicating with the direction switching valve 63
The oil chamber 29 communicates with the drain passage 46 that communicates with the second oil chamber 30.

In this state, a steering torque is input to the input shaft 1 via a steering wheel (not shown), and the torsion bar 16 is twisted to rotate the input shaft 1 and the output shaft 2 relatively. The operating rod 54 of the conversion mechanism 53 operates the hemispherical surface 39 at the tip of the second spool valve 37, and presses the second spool valve 37 against the spring force of the discharge spring 43 to move in the axial direction. Let it.

More specifically, the relative rotation of the input shaft 1 and the output shaft 2 causes the ball 61 of the motion converting means 56 to contact only one of the pair of inclined surfaces 60 formed on the movable member 55. Then, the movable member 55 is moved downward in FIG. As a result, the operation rod 54 whose base end 54a is connected to the movable member 55 is moved to the spherical bearing 62.
1 and the tip 54b side of this operating rod 54 is
Because it will move upward at
The tip of the second spool valve 37 is pushed on the side. As a result, the second spool valve 37 is pressed by the operation rod 54, and moves in the axial direction according to the relative rotation amount between the input shaft 1 and the output shaft 2.

The operating rod 54 presses and moves the second spool valve 37 of the control valve 20 in the axial direction, so that the second spool valve 37 is moved to the first oil chamber 29 and the second oil chamber 30.
Is closed.

That is, by moving the second spool valve 37 toward the first spool valve 28 against the spring force of the discharge spring 43, the second spool valve 37 comes into contact with the first spool valve 28, The concave tapered surface 35 of the first spool valve 28 comes into contact with the convex tapered surface 38 of the second spool valve 37. For this reason, the second spool valve 37
The communication oil passage 36 formed in the spool valve 28 is connected to the second oil chamber 30
The communication path 36 is closed at the side end, and the communication path 36 is closed. Therefore, the first oil chamber 29 communicating with the direction switching valve 63 is connected to the drain passage 46 communicating with the second oil chamber 30.
Will be blocked.

The operating rod 54 is connected to the second spool valve 3
7 to move in the axial direction, and the second spool valve 3
7 comes in contact with the first spool valve 28,
When the spool valve 28 is pressed in the axial direction, the supply spring 4
The second oil chamber 29 moves to the first oil chamber 29 side against the second spring force.

When the first spool valve 28 moves to the first oil chamber 29 side, the first oil chamber 29 and the third oil chamber 31 communicate with each other. As a result, the working oil guided from the third oil chamber 31 communicating with the working oil supply passage 47 to the first oil chamber 29 is supplied to the power cylinder 13 via the direction switching valve 63.

That is, when a steering torque in a fixed direction is input to the input shaft 1 and the first spool valve 28 in the spool valve receiving hole 25 moves toward the first oil chamber 29, the first
The poppet portion 28a formed in the spool valve 28 is separated from the step 25c between the large-diameter portion 25a and the small-diameter portion 25b of the spool valve housing hole 25, and the first oil chamber 29 and the third oil chamber 31 are communicated. You. Thereby, the hydraulic oil supplied from the supply passage 47 to the third oil chamber 31 is guided into the first oil chamber 29, and the passage 44, the through hole 40,
And through the circumferential groove 71 to the direction switching valve 63. Under the control of the direction switching valve 63, one cylinder chamber 15 </ b> L of the power cylinder 13 (when the steering direction is reversed, the other cylinder chamber 15 </ b> L). 15R).

In the state where the direction switching valve 63 does not rotate relative to the input shaft 1 and the output shaft 2, that is, in the neutral position of the steering operation, the throttles 68a and 69a are closed. The apertures 68b and 69b are slightly open. Therefore, one cylinder chamber 1 of the power cylinder 13
5L includes a circumferential groove 74, a passage 73, a throttle 68b, a depression 65,
The other cylinder chamber 15 </ b> R communicates with the drain passage 46 via a passage 72, and a circumferential groove 76, a passage 75, a throttle 69
b, communicating with the drain passage 46 through the depression 65.

From this state, a steering torque is input to the input shaft 1 via the steering wheel (not shown), and the torsion bar 16 is twisted to rotate the input shaft 1 and the output shaft 2 relatively. , Throttle 68 of direction switching valve 63
a is opened and the aperture 68b is closed (if the steering direction is reversed, the aperture 69a is opened and the aperture 69b is closed). As a result, the hydraulic oil supplied to the circumferential groove 71 through the control valve 20 passage 44
Via one of the cylinder chambers 15L of the power cylinder 13
(In the case where the steering direction is reversed, it is guided from the passage 70 to the other cylinder chamber 15R of the power cylinder 13 via the throttle 69a).

That is, the control valve 20 is connected to the direction switching valve 6
3 and the operation of the direction switching valve 63 for selectively switching the supply of the hydraulic oil to the one cylinder chamber 15L or the other cylinder chamber 15R of the power cylinder 13 is performed substantially simultaneously. become.

When the control valve 20 supplies the operating oil to the power cylinder 13 through the direction switching valve 63, the first spool valve 28 of the control valve 20 receives an input to the input shaft 1 in the process of increasing the steering torque. The balance between the steering torque and the pressure in one cylinder chamber 15L of the power cylinder 13 (in the other cylinder chamber 15R when the steering direction is opposite) and the spring force of the supply spring 42 gradually balance the three. And act as follows.

That is, the poppet portion 28a of the first spool valve 28 separates from the step portion 25c of the spool valve accommodating hole 25, and the operating oil is supplied from the first oil chamber 29 to the power cylinder 13 and, for example, one of the cylinder chambers When the pressure in 15L increases and the steering assisting force is exerted, the steering torque input to the input shaft 1 from the steering wheel (not shown) is equal to the magnitude of the assisting force obtained by the power cylinder 13, It can be reduced. At the same time, as the pressure in the cylinder 15L increases, the pressure in the first oil chamber 29 also increases. Therefore, the first spool valve 28 is pushed back by the pressure in the first oil chamber 29, and the poppet portion 28a Contacts the step 25c of the spool valve housing hole 25 to cut off the communication between the first oil chamber 29 and the third oil chamber 31. Further, when the steering torque input to the input shaft 1 increases for the steering operation, the poppet portion 28a moves away from the step portion 25c of the spool valve housing hole 25 again, and the hydraulic oil is removed from one of the cylinders of the power cylinder 13. It is supplied to the chamber 15L. Thereafter, the above operation is repeated until a steering assisting force of a predetermined magnitude is obtained in accordance with the steering torque input to the input shaft 1.

That is, when the steering torque is input to the input shaft 1, the first spool valve 28 of the control valve 20
The poppet portion 28a separates from the step portion 25c of the spool valve housing hole 25 until the assisting force of a predetermined magnitude is obtained, and the hydraulic oil is supplied to the power cylinder 1
3 and the operation of stopping the introduction of the hydraulic oil when the poppet 28a is in contact with the step 25c of the spool valve accommodating hole 25 is repeated.

Therefore, the torsion bar 16 is
The poppet portion 28a of the first spool valve 28 is twisted only within a range until the poppet portion 28a is separated from the step portion 25c of the spool valve housing hole 25, and the relative rotation amount between the input shaft 1 and the output shaft 2 is the same. Within the range.

On the other hand, when the hydraulic oil from the control valve 20 is introduced into the one cylinder chamber 15L of the power cylinder 13 via the direction switching valve 63, the other cylinder chamber 15R of the power cylinder 13 is set in the circumferential groove 76, Passage 75, depression 6
7. The throttle 69b communicates with the drain passage 46 via the recess 65 and the passage 67.

For this reason, a force in the steering direction is applied to the rack shaft 9 via the piston 14 by the pressure of the hydraulic oil introduced into the one cylinder chamber 15L of the power cylinder 13, and a steering assisting force is exerted. It is.

Thus, a predetermined steering assisting force is obtained by the hydraulic oil supplied to the power cylinder 13 in accordance with the steering torque applied to the input shaft 1.

Next, when the steering operation is completed and the input of the steering torque to the input shaft 1 is released, the first control valve 20 is turned off.
The spool valve 28 is pushed back toward the second oil chamber 30 by the pressure in the first oil chamber 29 and the spring force of the supply spring 42, and the poppet 28 a of the first spool valve 28 is moved to the step 25 c of the spool valve housing hole 25. The communication between the first oil chamber 29 and the third oil chamber 31 is interrupted.

The second spool valve 37 is connected to the pressure in the second oil chamber 30 (this pressure is equal to the cylinder chamber of the power cylinder 13 to which the hydraulic oil is supplied, for example, one cylinder chamber 1).
5L) and the spring force of the discharge spring 43, which is gradually pushed back in the direction away from the first spool valve 28, and the concave tapered surface 35 of the first spool valve 28 and the convexity of the second spool valve 37. The state is such that the tapered surface 38 of the shape does not contact. For this reason, the second spool valve 37 opens a communication oil passage 36 formed in the first spool valve 28 at an end on the second oil chamber 30 side, and the communication oil passage 36
open. As a result, the first oil chamber 29 communicating with one of the cylinder chambers 15L of the power cylinder 13 communicates with the drain passage 46, and releases the inside of the cylinder chamber 15L under atmospheric pressure to remove the steering assisting force. Will be.

At the same time, the direction switching valve 63 also returns to the neutral position, and the inside of one cylinder chamber 15L and the inside of the other cylinder chamber 15R of the power cylinder 13 communicate with the drain passage 46 from the center open type throttles 68b, 69b. Is done.

At this time, the second spool valve 37 of the control valve 20 is connected to the steering torque remaining on the input shaft 1 in the process of reducing the steering torque and the inside of one cylinder chamber 15L of the power cylinder 13 (the steering direction is reversed). In the case of (3), the pressure remaining in the other cylinder chamber 15R) and the discharge spring 43
When the balance between the three members and the spring force gradually changes, the spring moves and the communication oil passage 36 is gradually opened.

That is, when the second spool valve 37 slightly opens the communication oil passage 36, the oil pressure in one cylinder chamber 15L of the power cylinder 13 is slightly reduced, and the steering assisting force is reduced. When the assisting force of the power cylinder 13 is reduced, the steering torque remaining on the input shaft 1 is superior, and the second
The spool valve 37 contacts the first spool valve 28 and closes the communication oil passage 36. Further, when the steering torque input to the input shaft 1 is removed to cancel the steering operation, the second spool valve 37 separates from the first spool valve 28 again to open the communication oil passage 36, and the power The hydraulic oil in one cylinder chamber 15L of the cylinder 13 is released to the drain passage 46. Thereafter, the above operation is repeated until the steering torque input to the input shaft 1 and the steering assisting force of the power cylinder 13 become zero.

In other words, the second spool valve 37 of the control valve 20 reduces the relative rotation between the input shaft 1 and the output shaft 2 by reducing the steering torque input to the input shaft 1, thereby reducing the steering assist. Until the power becomes zero, the first spool valve 28
From the power cylinder 13
The operation of communicating the oil passage with the drain passage 46 and the operation of contacting the first spool valve 28 and closing the communication oil passage 36 are repeated.

On the other hand, when the steering wheel (not shown) is steered in the opposite direction, the ball 61 of the motion converting means 56 comes into contact only with the other of the pair of inclined surfaces 60 formed on the movable member 55. However, this movable member 55
Moves downward in FIG. 1 in the same manner as described above, so that the operating rod 54 operates the control valve 20 in the same manner as described above. On the other hand, the direction switching valve 63 operates in a direction opposite to the above-described direction, opens the throttles 69a and 68b, and opens the throttles 69b and 68.
Close a. Thereby, the direction switching valve 63 supplies the operating oil from the control valve 20 to the other cylinder chamber 15R of the power cylinder 13 via the throttle 69a,
The inside of one cylinder chamber 15L communicates with the drain passage 46 via the throttle 68b.

Thus, in the same manner as described above, a predetermined steering assisting force is obtained by the hydraulic oil supplied to the power cylinder 13 in accordance with the steering torque input to the input shaft 1.

As a result, a steering assisting force by the power cylinder 13 is obtained for a leftward or rightward steering operation of the steering mechanism.

At this time, the control valve 2
Since the recess 64 into which the hydraulic oil in the first oil chamber 29 of the 0 is guided has two diameters d1 and d2, when the high-pressure hydraulic fluid is guided into the recess 64, the movable member 55 has a spring due to a difference in pressure receiving area. It tends to be biased toward the member 59 side, and the operation of the movable member 55 becomes smooth.

The cut-off valve 81 operates as follows. That is, at the neutral position of the steering operation, the control valve 2
0 is not operated by the operation rod 54 and the second spool valve 3
7 opens the communication passage 36 and the inside of the first oil chamber 29 communicates with the drain passage 46, the inside of the first oil chamber 29 and the inside of the pressure chamber 85 are under atmospheric pressure. 8
4 is urged by the spring force of the spring member 87 and is located at a position separated from the operation rod 54 by a predetermined dimension (see FIG. 2).

Next, the operating rod 54 operates the control valve 20, the second spool valve 37 closes the communication passage 36, and the first spool valve 28 moves to move the third oil chamber 29 into the first oil chamber 29. When the hydraulic oil in 31 is introduced, the cutoff valve 81 is controlled to operate by the hydraulic oil pressure in the first oil chamber 29 guided through the passage 44, and the plunger 84 of the cutoff valve 81 operates the operating rod 54. Manipulate.

That is, the pressure chamber 8 of the cutoff valve 81
5, a first pressure chamber 29 of the control valve 20 is provided through a passage 44.
When the control valve 20 is operated by the operation rod 54 of the conversion mechanism 53 and the oil pressure in the first oil chamber 29 increases, the plunger 84 is set to the pressure in the pressure chamber 85 and the spring. The through hole 40 is balanced by the member 87.
After a predetermined stroke due to the gap between the tip of the plunger 84 and the operation rod 59, the operation rod 54 of the conversion mechanism 53 is pressed, and the operation rod 54 of the conversion mechanism 53 is pressed.
Discharges the second spool valve 37 of the control valve 20 to the discharge spring 4.
Thus, an assisting force is applied to the force pressing against the spring force of No. 3.

Therefore, when the steering torque is input to the input shaft 1 and the operating rod 54 of the conversion mechanism 53 operates the control valve 20 to increase the oil pressure in the first oil chamber 29, this control is performed. After the cutoff point at which the first oil chamber 29 of the valve 20 has increased to a predetermined pressure, the oil pressure (P) is controlled with a characteristic of increasing the increase rate of the hydraulic pressure (P) with respect to the steering torque (T) (see FIG. 5). ).

Here, there is one control valve 20 for controlling the supply of the hydraulic oil to the power cylinder 13. This one control valve 20 is irrespective of the steering direction, that is, when the vehicle is steered to the left and the right. The steering is operated in accordance with the steering torque in both cases of turning in the direction.

The operating rod 5 for operating the control valve 20
Since 4 is connected to the movable member 55 constituting the direction switching valve 63, both the control valve 20 and the direction switching valve 63 are operated by the movable member 55 that moves according to the steering torque.

Therefore, a power steering apparatus which can be downsized and whose manufacturing cost is low can be obtained.

Further, since the operating rod 54 of the conversion mechanism 53 is pivotally connected to the housing 3 via the spherical bearing 62, by selecting this pivot connection point, a so-called lever ratio is selected. Accordingly, the amount of movement of the distal end 54b with respect to the movement of the proximal end 54a of the operation rod 54 linked to the movable member 55 can be selected.

The motion converting means 6 of the converting mechanism 53
5 is constituted by a pair of inclined surfaces 60 and a ball 61, so that the movable member 5 has a simple configuration in accordance with the steering torque irrespective of the direction of relative rotation between the movable member 55 and the input shaft 1.
5 can be moved in a certain direction.

Further, since the control valve 20 is disposed substantially parallel to the input shaft 1, the number of radially outwardly projecting portions is reduced as compared with the case where the control valve 20 is disposed substantially in a right angle direction. In addition, the size of the entire apparatus can be reduced.

Further, since the direction switching valve 63 is constituted by a so-called rotary valve, the number of projecting portions outward in the radial direction can be reduced, and the size of the entire apparatus can be reduced.

The direction switching valve 63 and the control valve 20
Is formed in the housing 3 (3a), the installation of piping and the like can be minimized.

Further, so-called cut-off characteristics can be imparted to the hydraulic characteristics of the control valve 20, and since the cut-off valve 81 is arranged in series with the control valve 20, the radially outwardly projecting portion is formed. And the size of the entire apparatus can be reduced.

Although the embodiments have been described with reference to the drawings, the specific configuration is not limited to these embodiments, and can be changed without departing from the spirit of the invention.

For example, as the conversion mechanism 53, the embodiment in which the movable member 55 is movable in the axial direction with respect to the output shaft 2 and is connected so as not to be able to rotate relative to the output shaft 2 has been described. It is also possible to adopt a configuration that can move in the axial direction with respect to 1 and is connected so as not to be able to rotate relatively. In this case, the motion converting means 56 is provided between the movable member 55 and the surface of the output shaft 2 facing the movable member 55.

Further, the motion converting means 56 is provided with an inclined surface 60 at the end face of the movable member 55, and a sphere 61 as a projection which is in contact with the inclined surface 60 is provided on the opposing surface of the input shaft 1 facing the movable member 55, ie, Although the embodiment in which the radial flange 57 formed on the input shaft 1 is provided on the end surface has been described, the inclined surface is provided on the end surface of the radial flange 57 formed on the input shaft 1, and the protrusion is provided on the end surface of the movable member 55. It may be configured. The case where the motion converting means 56 is provided between the movable member 55 and the surface of the output shaft 2 facing the movable member 55 can be similarly considered.

The first spool valve 2 of the control valve 20
Although the embodiment in which the communication oil passage 36 is formed in FIG. 8 has been described, the communication oil passage 36 may be provided in the body 24.

Although the direction switching valve 63 is constituted by a so-called rotary valve, it may be constituted by a spool valve.

Further, the first spool valve 28 of the control valve 20 which controls the supply of the hydraulic oil to the power cylinder 13 and the operation rod 54 for operating the control valve 20 are provided with an actuator for giving a resistance to these operations. It is possible to add a drag (control force) to the first spool valve 28 and the operation rod 54 according to the vehicle speed by controlling the actuator according to the vehicle speed. Specifically, a drag that increases with an increase in vehicle speed is given to the operating force in the case of the valve opening operation of the control valve 20 by the operating rod 54. In this case, in the hydraulic characteristics of the hydraulic oil that changes according to the steering torque, the magnitude of the steering torque at which the hydraulic pressure starts to rise and the magnitude of the steering torque at which the hydraulic pressure starts to decrease change according to the vehicle speed, and when the vehicle is running at a low speed or stopped. At the time, a predetermined hydraulic oil pressure is obtained with a smaller steering torque than during high-speed running, and so-called vehicle speed sensitive control is performed.

[0119]

As described in detail above, according to the present invention, it is possible to reduce the size of the entire apparatus,
A power steering device with low manufacturing cost can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a power steering device according to an embodiment of the present invention, including a cross-sectional view of a control valve and a direction switching valve.

FIG. 2 is an enlarged sectional view showing a main part of FIG. 1;

FIG. 3 is an explanatory view including a cross section taken along line AA of FIG. 1;

FIG. 4 is a sectional view taken along line BB of FIG. 1;

FIG. 5 is a diagram showing a relationship between a steering torque (T) input to an input shaft and an operating oil pressure (P) for generating a steering assisting force, using a vehicle speed as a parameter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input shaft 2 Output shaft 13 Power cylinder 15L, 15R Cylinder chamber 20 Control valve 53 Conversion mechanism 54 Operating rod 55 Movable member 56 Motion conversion means 63 Direction switching valve

Claims (7)

[Claims] An output shaft connected to an input shaft of a steering mechanism so as to be rotatable relative to the input shaft is supplied with hydraulic oil to and from a power cylinder in accordance with a steering torque input to the input shaft. In a power steering apparatus for obtaining power, a type of a type in which the supply of hydraulic oil to a power cylinder is controlled in accordance with a steering torque input to the input shaft, and the supply of hydraulic oil to the power cylinder is interrupted at a neutral position of the steering operation. A control valve, including an operation rod capable of operating the control valve, a conversion mechanism for converting a steering torque input to the input shaft into a displacement of an operation means, provided between the control valve and a power cylinder, According to the direction of the steering torque input to the input shaft, the supply of hydraulic oil is switched to one or the other cylinder chamber of the power cylinder, and the discharge of hydraulic oil from these cylinder chambers is controlled. A direction switching valve, wherein the conversion mechanism is connected to the output shaft or the input shaft so as to be movable in the axial direction, and to be relatively unrotatable, and a movable member to which an operation rod is connected. A motion conversion device that is provided between a movable member and an opposing surface of an input shaft or an output shaft facing the movable member, and converts relative rotation between the movable member and the input shaft or the output shaft into an axial movement of the movable member. Means, wherein the direction switching valve is formed between a movable member and an input shaft or an output shaft which is rotatable relative to the movable member. . 2. The control rod is accommodated in a housing that rotatably accommodates an input shaft, and a control rod is connected to a movable member at a base end side and a distal end side penetrates the housing to operate a control valve. 2. The power steering apparatus according to claim 1, wherein the power steering apparatus extends so that an intermediate portion between a proximal end and a distal end thereof is pivotally connected to the housing. 3. The motion conversion means is provided on one of the movable member and an opposing surface of an input shaft or an output shaft facing the movable member, and a pair of inclined surfaces inclined in a rotating direction; The power steering device according to claim 1, further comprising a projection provided on one of the other surfaces and in contact with the pair of inclined surfaces. 4. The control valve includes a spool valve that is operated to move in an axial direction by operating means of a conversion mechanism,
The power steering device according to claim 1, wherein the spool valve is disposed substantially parallel to the input shaft. 5. The power steering apparatus according to claim 1, wherein the direction switching valve is formed between an outer periphery of the input shaft or the output shaft and an inner periphery of a movable member. 6. The directional control valve is formed between the outer periphery of the input shaft or the output shaft and the inner periphery of the movable member, and the control valve is in contact with the housing. 3. The power steering device according to 2. 7. A cut-off valve for assisting the operation of the control valve by the operation rod of the conversion mechanism is provided, and the cut-off valve is located at a position facing the control valve with the operation rod of the conversion mechanism interposed therebetween. The power steering device according to claim 1, wherein the power steering device is provided.