JP2593050B2 - Power steering system equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for a hydraulic power steering system which provides a desired resistance between two relatively rotating members for controlling a power steering motor.

[0002]

BACKGROUND OF THE INVENTION In known power steering systems, torsion bars are used to interconnect a pair of relatively rotatable hydraulic control valves. When a steering operation is performed, the torsion bar undergoes torsional elastic deformation. Since the torsion bar is elastically deformed, the valve members rotate relative to each other. Due to the relative rotation between the valve members, the pressurized liquid flows from the pump to the hydraulic power steering motor connected between the frame of the vehicle and the steered wheels, and the vehicle is steered by operating the power steering motor. To A power steering system in which a torsion bar is subjected to torsional deformation is disclosed in U.S. Pat.
No. 9,099, No. 4,557,342, No. 4,59
8,787.

[0003]

During operation of a vehicle, it is desirable to have the force to bias the hydraulic valve of the steering system to a neutral, non-steering state when the steering torque input by the operator is low or non-existent. . Also, the amount of manual input torque required to turn the steered wheels is based on whether the vehicle was stationary or operating at a very low speed and the parking operation was performed, or 88 km / h (55 mph).
It is also desirable to be able to compare whether or not the lane change operation is being performed. However, the amount of torque that the vehicle driver should input to the steering system is 88
Steering in parking operation is about 240% larger than during lane change when traveling at km (55 miles). The torsion bar spring has an essentially linear spring constant and provides a hydraulic control valve biasing torque toward the on-center state, ie, a torque that is the product of angular displacement multiplied by the spring constant. It is desirable to apply a preload to suppress the angular displacement of the torsion bar until the input torque reaches a predetermined minimum level.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a device including a new and improved torsional tension spring for use in a hydraulic power steering system. The device includes a pair of members rotatable relative to each other to control operation of a power steering motor. A torsional tension spring resiliently interconnects the pair of members. In this device, cam surface means for changing the tension of the torsion tension spring in accordance with the relative rotation between the pair of members is provided, and the cam surface means changes the degree of the tension in one range of the relative rotation and the other range. The degree of change in tension is different.

[0005]

When the steering operation is started, the torque acts on the torsional tension spring, causing the torsional tension spring to deform in the torsional direction and the axial direction. The increment of axial deformation of the torsion tension spring for each increment of relative rotation between members is such that torsional force is required to effect either a parking operation or a relatively fast lane change. For one angular displacement range of the spring, it decreases in the other ranges.

[0006] The torsional tension spring is tensioned by cam surfaces which engage on opposite sides of a bearing element in the form of an annular array of rollers. Due to the relative rotation between the cam surfaces,
The extension tension is transmitted to both ends of the torsional tension spring via the rigid body, and the torsional tension spring extends in the axial direction. The cam surface has a torsion rod during at least a portion of the relative rotation between the cam surfaces, where each successive incremental rotation increment is subsequent to the initial increase of the relative cam surface relative rotation. It has a shape that allows the spring to deform in the axial direction by a small amount.

[0007]

DETAILED DESCRIPTION A power steering system 10 (FIG. 1) is used to rotate the steered wheels (not shown) of a vehicle. The power steering system 10 includes the necessary elements to convert the energy of the pressurized liquid into a mechanical output torque. One of the elements is a hydraulic power steering motor 12. The power steering motor 12 includes a housing 1 having a cylindrical inner surface 16 defining a chamber 18.
4 is included. A piston 20 divides the chamber 18 into left and right ends 22, 24 (see FIG. 1).

[0008] A plurality of rack teeth 26 are formed on the piston 20. The rack teeth 26 mesh with the teeth 28 of the sector gear. The sector gear teeth 28 are disposed on an output shaft 32 which is connected to the steered wheels by a suitable steering chain (not shown). The movement of the piston 20 in the chamber 18 causes the output shaft 32 to rotate, activating the steering chain in a known manner.

The housing 14 has a fluid inlet port 34 connected to a pump or other pressurized hydraulic source. Housing 14 also has a fluid outlet port 36 connected to the reservoir.

A directional control valve assembly 40 constructed in accordance with the present invention controls the direction of operation of the power steering motor 12. The directional control valve assembly 40 includes a member 42 connected to a valve core or rotatable input shaft 44.
The input shaft 44 is rotated by manual rotation of the steered wheels.
The valve core 42 is received in a valve sleeve or member 46 in a telescopic manner. The valve cylinder 46 is a driven shaft 4 having an external thread.
8 is connected. The driven shaft 48 includes a ball nut 50
Is connected to the piston 20.

The valve core 42 and the valve cylinder 46 are formed by a torsion tension spring 52.
Interconnected by The inner end 56 of the torsional tension spring 52 is connected to the valve cylinder 46 by a pin 58. The outer end 60 of the torsional tension spring 52 is connected to the valve core 42 by a pin 62. The torsional tension spring 52 has a shape corresponding to the shape of a known torsion bar.

An outflow passage 66 formed in the valve cylinder 46 connects the inside of the valve cylinder 46 with the power steering motor chamber 18.
Is in fluid communication with the left end 22 of the. Another flow path (not shown) formed in the valve cylinder 46 fluidly communicates the inside of the valve cylinder to the right end of the motor cylinder chamber 18 via the housing flow path 70.

The power steering system 10 has the same configuration as disclosed in US Pat. No. 4,942,803. However, the power steering system may have a configuration different from the configuration shown in FIG. For example, a power steering system is disclosed in U.S. Pat.
A rack and a pinion of the type disclosed in U.S. Pat. If desired, a motorized valve may be used to control the flow of fluid to the power steering motor as disclosed in U.S. Pat. No. 4,557,342. Otherwise, the power steering system may include an electric steering assist motor as disclosed in U.S. Pat. No. 4,598,787.

Means for Applying Tension to the Torsion Tension Spring According to a feature of the invention, means 74 for applying tension to the torsion tension spring (hereinafter referred to as tensioning assembly) applies tension to the torsion tension spring 52. Used for Assembly 7
4 is connected to the inner end 56 and the outer end 60 of the torsional tension spring via a rigid metal. Thus, the assembly 74
Is connected to the inner end 56 of the torsional tension spring by a metal clip 76 and a rigid metal valve sleeve 46. Valve cylinder 46
Is connected to the inner end 56 of the torsional tension spring 52 by a rigid metal pin 58. The assembly 74 includes the rigid valve core 42.
Tension spring 52 through a rigid metal pin 62 (FIG. 2)
Is connected to the outer end portion 60 of the main body.

The tensioning assembly 74 includes an annular thrust bearing assembly 80. Thrust bearing assembly 80
Are the outer annular rows 84 of the same cam surface 86 (FIGS. 3 and 4).
And the inner annular row 92 of the same cam surface 94. The cam surfaces 86 are separated by flat radially extending lands 88. In the illustrated embodiment of the invention, the cam surface 86 is formed on the axially inner end of the rigid metal valve core 42. However, if requested,
The cam surface 86 and the land 88 are formed by an annular member or valve core 42.
It can also be formed on a washer that is firmly secured to the inner end of the body.

The inner annular row 92 of the same cam surface 94
It is formed on an annular profile washer 98 (FIGS. 3, 5). The cylindrical cam surfaces 94 in the annular row 92 are separated by flat radially extending lands 96 (FIG. 5). The cam surface 94 (FIG. 5) has the same shape as the cam surface 86 (FIG. 4).

A profile washer 98 is fixedly secured to a rigid annular metal support ring 102 (FIGS. 2 and 3).
Thus, the support ring 102 has a cylindrical central portion 104 that snaps into the inner diameter of the profile washer 98. The support ring 102 also snaps into the tubular end of the torsion tension spring 52. An inner end in the axial direction of the support ring 102 is disposed in abutment engagement with the annular clip 76.

The interrupted fit between the support ring and the inner end of the torsion tension spring transfers force from the support ring 102 to the inner end 56 of the torsion tension spring 52. Further, a force is transmitted from the support ring 102 to the inner end of the torsion force spring 52 by the clip 76.

The thrust bearing 80 (FIGS. 2 and 6) includes a plurality of cylindrical rollers 110 disposed in an annular row 112. The roller 110 has an annular retainer ring 114.
(FIG. 6), a more evenly spaced relationship is maintained. Although the thrust bearing assembly 80 can have many different configurations,
In one particular embodiment of the present invention, the thrust bearing assembly 80
Is an INA TC-1018 thrust bearing.

The number of rollers 110 in thrust bearing 80 depends on the number of cam surfaces in annular array 84 of cam surfaces 86 (FIG. 4) and the number of cam surfaces in annular array 92 of cam surfaces 94 (FIG. 5). equal. The cam surfaces 86 in the annular row 84 and the cam surfaces 94 in the annular row 92 abut and engage the respective ends of the roller 110. Retainer 114 (FIG. 6) extends between lands 88 between cam surfaces 86 and lands 96 between cam surfaces 94 to interconnect rollers 110. In one particular embodiment of the present invention, thrust bearing 80 includes twenty rollers 110 that engage twenty cam surfaces 86 in annular row 84 and twenty cam surfaces 94 in annular row 92. In.

The relationship between one of the rollers 110 and one of the cam surfaces 94 in the annular row 92 is illustrated in FIG. The cam surface 94 has a central groove or recess 122 in which the roller 110 rests when the annular row 112 of rollers is in an on-center position corresponding to the straight travel of the vehicle. Cam surface 94
Is gently upwardly inclined toward the land 96 (see FIG. 7).
It has a pair of side parts 124 and 126 to be formed. Side 124,
126 is connected to the groove 122 by transition portions 128 and 130.

The groove 122 has a slightly steep side surface. The sides 124, 126 of the cam surface 94 have a more gradual upward slope. The steeply inclined side surface of the groove 122 is
Sides 124, 12 gently inclined by 8, 130
6 is connected. The central axis 134 of the cam surface 94 is located at the center of the interconnection between the sides 124, 126 and the land 96. When the steering system is in the on-center state, the center axis of the roller 110 is
4 on the central axis 134.

In a particular embodiment of the invention, a portion of the cam surface 94 for one of the shafts 134, such as the right side seen in FIG. It should be understood that the configuration of the cam surface 94 is the same on both sides of the central axis 134. In Chart I, the angle is measured from a first or primary radial axis 138 (FIG. 5) extending through the center of cam surface 94 and intersecting vertical axis 134 (see FIG. 7). The angle is measured up to the second radiation axis 140 (FIG. 5). The angle is indicated by reference numeral 142 in FIG.

The angle 142 is determined by the two radiation axes 138 and 140
When (FIG. 5) extends through the center of the cam surface 94, 0
Is considered to be a degree. As the angle increases in a counterclockwise direction (see FIG. 5), the radiation axis 140 is increasingly pulled away from the radiation axis 138, and the angle 142 becomes larger.

In Table I, the depth of the cam surface is the land surface 9
6 is considered to be the vertical distance from the cam surface 94 to the intersection of the radial axis 140. Thus, the depth of the cam surface 94 is
It is measured vertically downward (see FIG. 7) from the land 96 to the height at which the radial axis 140 intersects the cam surface 94.

When the angle is 0 degrees, the depth of the cam surface 94 in a particular embodiment of the present invention, corresponding to FIG.
It is 0.0508 mm (0.00200 inches). As the angle 142 increases to one degree, the depth of the cam surface 94 becomes 0.0409 mm (0.00161 inches). Similarly, if the angle 142 (FIG. 5) increases by two degrees, the depth of the cam surface 94 will be 0.0345 mm (0.00136 inches). The cam surface 94 has a shape such as that produced by a radial axis from the center of the annular row 92. Thus, the axis of radiation from the center of the cam surface is tangent to cam surface 94 throughout the cam surface.

The amount of elevation of cam surface 94 for each increment of angle 142 (see FIG. 7) varies. Thus, the cam surface 9
4 near the center of 4, ie in the region of the groove 122
For each increment, there is a relatively large decrease in cam surface depth. The outside 126 of the cam surface 94 that is gently inclined
, For each increment of angle 142, the depth of cam surface 94 changes relatively small. In the transition section 130, the cam surface 9
The depth of 4 changes at a rate of decrease for each increment of angle 142.

Chart I (mm) Angle Depth Angle Depth Angle Depth 0.00 0.0508 2.00 0.0345 4.00 0.0213 0.25 0.0465 2.25 0.0328 4.25 0.0198 0.50 0.0437 2.50 0.0310 4.50 0.0185 0.75 0.0422 2.75 0.0292 4.75 0.0170 1.00 0.0409 3.00 0.0277 5.00 0.0157 1.25 0.0394 3.25 0.0259 5.25 0.0145 1.50 0.0378 3.50 0.0244 5.50 0.0132 1.75 0.0361 3.75 0.0229 5.75 0.0119 6.00 0.0107 Cam surface 86, in two rows 84, 92 of cam surfaces (Figs. 4 and 5)
94 have the same shape. The roller 110 is provided in the annular row 8.
4 and one of the cam surfaces 94 in the annular row 92.
Is engaged with one of them. Therefore, each increment within angle 142 causes annular rows 84 and 92 to be spaced apart by a distance that is twice as large as the distance shown in FIG. For example, angle 14
As 2 increases from one degree to two degrees, the annular rows 84, 92 become
It is separated by a distance of 0.0127 mm (0.00050 inches), or twice the change of one recess depth of 0.00635 mm (0.00025 inches).

The annular row 84 includes the rigid valve core 42 and the pin 62.
And to the outer end 60 of the torsion tension spring.
An annular row 92 inward of the cam surface includes a rigid support ring 102.
And a clip 76 connected to the inner end 56 of the torsion tension spring. Therefore, the length of the torsional tension spring 52 is
It increases resiliently as the annular rows 84, 82 are spaced apart.

As the roller 110 (FIG. 7) rotates along the cam surface 94, the slope of the portion of the cam surface with which the roller engages changes. Thus, when the roller 110 is in the on-center position corresponding to the straight movement of the vehicle, the roller is in the groove 1
22 engage the relatively steeply sloping sides. Roller 11
When 0 is displaced from the on-center position, for example, to the right as viewed in FIG. 7, the roller moves to engage a more gently sloping transition of the cam surface 94. As the slope of the portion of the cam surface where the roller engages changes, the line at which the cam surface engages the roller also changes.

When the roller 110 (FIG. 8) engages the relatively steeply sloping portion of the cam surface 94 as shown schematically at 144 in FIG.
45. The roller 110 moves upward (FIG. 7,
When the cam surface 94 engages the less steep sloped portion 146 (as seen in FIG. 8), the roller has a second line 147 that engages the cam surface 94. Part 14 of cam surface 94
It should be understood that the change in slope of 4,146 is exaggerated for clarity of the illustration of FIG. 8 and is greater than would actually occur.

Since the cam surfaces 94 and 86 have the same shape, the slope of the cam surface 86 changes from the slope shown by line 148 to the slope shown by line 149 in FIG. As a result, the line of engagement of the roller 110 with the cam surface 86 becomes 15
The line indicated by 1 changes to the line indicated by 153 in FIG.

The radial distance that the line of engagement of the cam surface 94 with the roller 110 moves radially outward (as viewed downward in FIG. 8) is from the line indicated by the slope 144 to the line indicated by 146. When this occurs, it is shown in FIG. 8 as distance X / 2. Similarly, the radial distance at which the line of engagement of cam surface 86 with roller 110 moves radially outward (upward in FIG. 8) is one line from the line indicated by slope 148.
When changing to the line indicated by 49, FIG.
/ 2. Thus, the cam surfaces 86, 94
The composite radial distance of the line of engagement of the roller 110 with respect to
be equivalent to.

The amount by which the line of engagement of the roller 110 with the cam surfaces 86 and 94 changes, that is, the distance X is the angle 142
It is shown in Chart II for each increment of (Figure 5). Angle 14
For each increment of 2 change, the amount of extension of the torsional tension spring 52 is the sum of the change due to the change in the depth of the cam surfaces 86, 94 and the change in the line of engagement of the cam surface with the surface of the roller 110. By an amount equal to

As the angle increases from one degree to two degrees, the change in the axial length of the torsional tension spring is caused by the change in the depth of the cam surface 86, the change in the depth of the cam surface 94, and the engagement of the roller 110 with the cam surface. Resulting from line changes. For example, as the angle increases from one degree to two degrees, the annular rows 84 and 92 become 0.0127 mm.
(0.00050 inches), i.e., a depth change at one of the cam surfaces is separated by twice the distance of 0.00635 mm (0.00025 inches). In addition, the cam surface row
Sum of the distances X shown in Chart II, ie 0.0094
0mm (0.00356 + 0.00254 + 0.001
78 + 0.00152). As a result, as a result of the angle 142 changing from 1 degree to 2 degrees, the total axial extension of the torsional tension spring 52 becomes 0.022.
It is 1 mm (0.00087 inch).

Chart II (mm) Angle Depth Angle Depth Angle Depth 0.00 2.00 0.00152 4.00 0.00025 0.25 2.25 0.00127 4.25 0.00025 0.50 0.00279 2.50 0.00102 4.50 0.00025 0.75 0.00508 2.75 0.00076 4.75 0.00025 1.00 0.00457 3.00 0.00076 5.00 0.00025 1.25 0.00356 3.25 0.00051 5.25 0.00025 1.50 0.00254 3.50 0.00051 5.50 0.00025 1.75 0.00178 3.75 0.00051 5.75 0.00025 6.00 0.00025 When the working vehicle is traveling straight, the annular rows 84, 92 of cam surfaces 86, 94 are axially aligned with each other. At this time, the roller 110 is engaged with the groove 122 in the cam surfaces 86 and 94. The torsional tension spring 52 is tensioned in the axial direction by a preload force. This allows the torsional tension spring 52 to move the cam surfaces 86 and 94 to the thrust bearing assembly 8.
0 is pressed against both ends.

Until the steered wheels of the vehicle are rotated, the force of the initial preload acts on the valve core 42 and the valve cylinder 46 to stop the power steering motor 12 at the on-center position where the power steering motor 12 is not operated. When the rotation steering is started, the input shaft 44 and the valve core 42 rotate with respect to the valve cylinder 46.

The relative rotation between the valve core 42 and the valve cylinder 46 causes the left end 2 of the power steering motor chamber 18 to rotate.
The pressure fluid is supplied to either the right end 2 or the right end 24. The other chamber of the power steering motor is connected to a reservoir. This results in a rotational movement of the steered wheels.

When the valve core 42 rotates with respect to the valve cylinder 46,
The inner annular row 84 and the outer annular row 92 of the cam surface are offset from each other. Thus, the angle 142 (FIG. 5) increases. As angle 142 increases, roller 110 (FIG. 7) rotates from groove 122 along cam surface 94, for example, to the right (see FIG. 7).

The portion of the cam surface 94 that forms the groove 122 has a relatively steep slope, so that for each incremental movement of the relative movement between the valve core 42 and the valve body 46, the cam surface 94
The depth varies relatively widely. Thus, the angle 142
As the angle increases from 0 degrees to 1 degree, the depth of the portion of the cam surface 94 where the roller engages becomes 0.0508 mm (0.002 mm).
00 inch) to 0.0409 mm (0.00161 inch) (see Figure I). Further, the depth of the cam surface 86 engaging the opposite side of the roller is also 0.0508.
mm (0.00200 inch) to 0.0409 mm
(0.00161 inches). This creates a total change of 0.0198 mm (0.00078 inches) in the cam surface.

As the roller 110 rotates along the cam surfaces 86, 94, the line of engagement of the roller with the cam surface changes axially relative to the annular rows 84, 92 by the amount indicated by X in Chart II. Thus, when the angle 142 increases from 0 degrees to 1 degree, the axial change of the roller engagement point is 0.0124.
mm (0.00279 + 0.00508 + 0,0045
Shift by 7). The composite or total change in the length of the torsional tension spring 52 is the sum of the change due to the change in the depth of the cam surfaces 86, 94 and the change in the line of engagement of the roller 110 with the cam surface. Thus, the torsion tension spring 5
The total change in the axial amount of 2 is 0.0198 mm (0.00
(0.078 inch) to 0.0124 mm (0.00049 inch). Since both ends 56 and 60 of the torsional tension spring 52 are connected to the annular rows 84 and 92 by the rigid metal members, the tension received by the torsional tension spring 52 elastically tensions the torsional tension spring to reduce its length. The same amount, ie 0.0
Increase elastically by 323 mm (0.00127 inches).

When the relative rotation between the valve core 42 and the valve cylinder 46 continues, the cam surface 8 with which the rollers of the thrust bearing 80 engage.
The 6,94 slope is reduced. Therefore, for an equal increment of relative rotation between the valve core 42 and the valve body 46, the amount of elastic axial deformation of the torsion tension spring is such that the relative rotation between the valve core 42 and the valve body 46 is It decreases as it increases.

As the amount of axial extension of the torsion tension spring 52 decreases, during successive increments of relative rotation between the valve core 42 and the valve body 46, the valve is caused by the elastic tension deformation of the torsion tension spring. The amount of force required to cause each successive increment of wick rotation is reduced. This corresponds to curve 1 in FIG.
Indicated by 50. When the steered wheels change direction from the initial position, the steeply inclined portions of the cam surfaces 86, 94 adjacent to the groove 122 have a relatively large increase in the resistance to relative rotation between the valve core 42 and the valve cylinder 46. Indicates the rate. This is indicated by the relatively steep slope of portion 152 of curve 150 (FIG. 9).

As the relative rotation between the valve core 42 and the valve cylinder 46 increases, the inclination of the outer cam surface 86 and the inner cam surface 94 with which the roller 110 engages decreases. Therefore,
The amount of resistance encountered during further increments of relative rotation between the valve stem 42 and the valve stem 46 is reduced. This is indicated by the portion of the curve indicated at 154 in FIG. This is the valve core 4
This is because the resilient axial extension of the torsional tension spring 52 for each incremental rotation of the relative rotation between the two and the valve body 46 results in less axial extension of the torsional tension spring 52. Therefore, even if the total elastic axial extension of the torsion tension spring 52 and the total axial distortion in the torsion tension spring are caused by the valve core 42 and the valve cylinder 4
To increase for each increment of relative rotation between 6 and
The resistance to each additional increment of relative rotation is represented by curve 150
Is reduced as indicated by portion 154.

In addition to the axial extension caused by the action of tension on the torsional tension spring 52, the torsional tension spring is elastically deformed by the torsional force when the valve core 42 and the valve cylinder 46 rotate relative to each other. Thus, the inner end 46 of the torsional tension spring 52 is secured to the valve sleeve 46 and the outer end 60 of the torsional tension spring is securely secured to the valve core 42. Valve core 42
The relative rotation between the valve body 46 and the torsion tension spring 52
Deform elastically in torsional tension or in a known manner.

The amount of torsional deformation of the torsional tension spring 52 is
It remains constant for each increment of relative rotation between 2 and the valve body 46. Therefore, the resistance due to the tension is shown in FIG.
As shown by the curve 158 in FIG.

The total resistance force encountered to effect relative rotation between the valve core 42 and the valve body 46 is the resistive force caused by the elastic tension deformation of the torsional tension spring and the elastic torsional deformation of the torsional tension spring. Is the sum of Thus, the total resistance to the relative rotation between the valve core 42 and the valve cylinder 46 is reduced by the valve core 4.
The result is an increase during the relative rotation between 2 and valve body 46 as shown in curve 162.

During the parking operation, the relative rotation between the valve core 42 and the valve cylinder 46 will typically slightly exceed 3 degrees. During a lane change at 55 mph, the relative amount of rotation between the valve stem 42 and the valve stem 46 will typically be about 2.2 degrees.
After a relative rotation of about 1.5 degrees between the valve core 42 and the valve body 46, the decreasing resistance due to the tension deformation of the torsion tension spring 52 increases the increasing resistance due to the torsional deformation of the torsion spring. Is partially offset.

From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications in the invention. Such improvements, changes and modifications within the art are intended to be covered by the appended claims.

[0050]

According to the present invention, an accurate steering operation can be performed by a hydraulic control valve having a torsional tension spring.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a power steering system configured according to the present invention.

FIG. 2 is an enlarged partial sectional view showing a part of the power steering system of FIG.

3 is an exploded view of some components of the device of FIG.

FIG. 4 is a sectional view taken generally along the line 4-4 in FIG. 2;

FIG. 5 is a sectional view taken generally along the line 5-5 in FIG. 2;

FIG. 6 is an enlarged partial view showing a part of a thrust bearing assembly used in the apparatus of FIGS.

FIG. 7 is an enlarged partial sectional view showing a part of a roller and a part of a cam surface in the thrust bearing assembly of FIG. 6;

FIG. 8 is a highly simplified diagram depicting the manner in which the line of engagement of the bearing with the cam surface changes based on the change in inclination of the cam surface.

FIG. 9 is a graph illustrating how the steering force changes.

[Explanation of symbols]

 42 valve core 46 valve cylinder 52 torsion tension spring 80 thrust bearing 84,92 annular row 86,94 cam surface 100 roller

Claims (5)

(57) [Claims] An apparatus for use in a power steering system (10), wherein first and second members (4) are rotatable relative to each other to control operation of a power steering motor (12).
2, 46); a torsional tension spring (52) interconnecting the first and second members (42, 46); and a torsional tension spring (52) upon relative rotation between the members in a first direction. Means for applying a torque to the torsional tension spring to increase the torsional deformation of the torsional tension spring; and applying a tension to the torsional tension spring when the members rotate relative to each other in a first direction. Means (74) for increasing the axial deformation of the torsional tension spring, the means (74) for applying tension to the torsional tension spring comprises a first member (74) between the first and second members. The tension applied to the torsional tension spring (52) is changed by a first amount with respect to the first angular displacement increment at the time of relative rotation in the direction of. The increment at a position deviating from the position of the first angular displacement increment. Means for changing the tension applied to the torsional tension spring by a second amount different from the first amount for a second angular displacement increment that is the same as the minute amount (80, 84, 92), said means (80, 84, 92) comprising a cam surface means (8) for transmitting a force to effect an axial deformation of said torsional tension spring.
4, 92), wherein the cam surface means comprises a first portion (128, 130) having a first slope and a second portion having a second slope having a smaller degree of slope than the first slope. And the first portion (128, 130) of the cam surface passes through the first angular displacement increment of relative rotation between the first and second members. Applying tension to the torsional tension spring (52), the second portion (124, 126) of the cam surface causes the torsion through the second angular displacement increment between the first and second members. The device according to claim 1, characterized in that it exerts a tension on a tension spring (52). 2. Apparatus according to claim 1, wherein said means (74) for tensioning said torsional tension spring comprises an annular array (112) of rollers (110) and said cam surface means. (84, 92) are an annular array (84) of first cam surfaces (86) disposed in engagement with a first side of the annular array (112) of rollers, and an annular array of rollers. An annular row (92) of second cam surfaces (94) disposed in engagement with the second side of (112). 3. The apparatus of claim 1, wherein the first and second members cooperate to control fluid flow to a power steering motor. The means (74) for tensioning the torsional tension spring comprises an annular array of rollers (112) having an open central portion through which the torsional tension spring (52) extends. The cam surface means (84, 92) is fixedly connected to one end of the first valve member (42) and the annular row of rollers (11
2) a first cam surface (8) disposed in engagement with the first side.
6) an annular row (84) and a second fixedly connected to said second valve member (46) and disposed in engagement with a second side of said annular row of rollers (112). An annular row (92) of cam surfaces (94). 4. The apparatus according to claim 1, wherein the first and second members are rotatable relative to each other from an initial position and torque the torsional tension spring. (58, 6)
2) increasing the torsional deformation of the torsional tension spring during relative rotation between the members in a first direction from an initial position, and between the members in a second direction opposite to the first direction. The torsional deformation of the torsional tension spring is also increased during the relative rotation, and the means (74) for applying a tension to the torsional tension spring is provided when the members (42, 46) are in the initial positions. Means (80) for maintaining said torsion tension spring in an axially deformed state under the influence of said torsion tension spring and exerting a force for urging said first and second members to an initial position. The device, comprising: 5. The device according to claim 1, wherein the torsional tension spring (52) has first and second ends (6).
0, 56), wherein the first member (42) is fixedly connected to the first end (60) of the torsional tension spring and the second member (46). Is fixedly connected to said second end (56) of said torsional tension spring and means (74) for tensioning said torsional tension spring.
Are the first and second ends (6) of the torsional tension spring.
0, 56) and a rigid body (42, 1).
02) connected to said first and second ends of said torsional tension spring, said rigid body comprises means for applying said tension (74) and said first and second ends of said torsional tension spring. The device for transmitting tension to and from an end.