JPH01186470A - Hydraulic control valve - Google Patents

Abstract

PURPOSE:To facilitate the working for a cut part for obtaining the working oil passing area variation state by forming the first cut part at the corner part on a valve body side and forming the second cut part having a circular arc port and a straight line part on the peripheral surface of the valve body, in a hydraulic control valve suitable for a power steering device. CONSTITUTION:As for a hydraulic control valve of a power steering device, a cylindrical valve body 2 connected with an input shaft is fitted into a casing 1 jointed with an output shaft connected with the input shaft through a torsion bar 4. The gap 8 between the long grooves 5 and 6 is varied according to the relative revolution of the both 1 and 2, and the communication state of the oil leading-out holes 11..., 12... connected with a power cylinder is controlled. In this case, the first cut part 60 is formed at the corner parts on the both sides of two long grooves 6 which are positioned in symmetry for the axis center of a valve body 2 among the long grooves 6 communicating to the discharge side of a hydraulic pump through an oil introducing hole 10. Further, the second cut part 50 is formed at the corner part of the long groove 5 faced to the gap 8 on the both sides of two long grooves 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary hydraulic control valve, and particularly to a hydraulic control valve suitable for application to a hydraulic power steering device.

[Prior art]

2. Description of the Related Art In automobiles, particularly large automobiles, considerable force is required to operate the steering wheel due to the resistance force acting on the wheels from the road surface.

Therefore, a hydraulic power steering system has been developed that assists the force required for this operation with the hydraulic pressure generated by a hydraulic cylinder installed in the steering mechanism, reducing the driver's labor burden and providing a comfortable steering sensation. Widely popular.

In this power steering device, an input shaft that is interlocked with the steering wheel and an output shaft that is connected to the wheel are coaxially connected via a torsion bar, and as the steering wheel is rotated, the torsion bar is twisted. In this case, a relative angular displacement is generated between the two shafts, and a rotary hydraulic control valve is configured at the connecting portion of the two shafts, and the operation of the hydraulic control valve causes pressure oil to be supplied to the hydraulic cylinder. The feeding direction of the steering wheel is switched according to the relative angular displacement, that is, the operation of the steering wheel.

This hydraulic control valve has a plurality of long grooves extending in the axial direction at equal intervals on its inner peripheral surface, and is attached to a cylindrical casing coaxially fixed to the connecting end of the output shaft. , a valve body having the same number of long grooves as the long grooves equidistantly arranged on the outer circumferential surface near the connecting end of the input shaft; At the same time, the long grooves of the valve body are connected alternately to a hydraulic pump as a high pressure source and an oil tank as a low pressure source, and the long grooves of the casing are connected to both sides of the hydraulic cylinder. The valves are connected alternately to the oil chambers, and when a relative angular displacement occurs between the valve body and the casing, the switching operation is performed in accordance with the change in area that occurs in the gap between both sides of the long groove. . In other words, the area of the gap on both sides of the long groove of the casing becomes larger on one side and smaller on the other depending on the relative angular displacement, so that the area of the gap on both sides of the long groove of the casing becomes larger and smaller on the other side. Long grooves of the casing that communicate through gaps and long grooves of the casing that also communicate through gaps with smaller areas occur alternately in the circumferential direction of the casing, and the hydraulic pressure in the long grooves is Due to the difference in flow resistance in the gap, the oil pressure in the former becomes larger than the oil pressure in the latter, resulting in a pressure difference between the two oil chambers of the hydraulic cylinders respectively connected to the long grooves. The hydraulic cylinder then generates a steering assist force in response to this pressure difference.

Now, the force required to steer a car varies depending on the driving speed, and while a large operating force is required to steer a car that is running at low speed or when it is stopped, a car that is running at high speed can be steered with a small amount of operating force. is possible. Therefore, the power steering system generates a large steering assist force to reduce the driver's labor burden as much as possible when driving at low speeds or when stopped; It is desirable to have such a characteristic that almost no steering assist force is generated in order to improve running stability, and that a steering assist force proportional to the road reaction force can be obtained in an intermediate portion between the two. Therefore, in the hydraulic control valve, until the steering torque applied to the steering wheel reaches a predetermined value and the relative angular displacement between the valve body and the casing reaches a predetermined value, the pressure difference generated as described above is maintained. The pressure difference is maintained at approximately 0, and then the pressure difference increases approximately linearly as the relative angular displacement increases, and the relative angular displacement further increases, and after this reaches another predetermined value, the relative angular displacement increases. It is required that the pressure difference rapidly increases as the pressure increases.

Since the hydraulic control valve performs the switching operation as described above, in order for it to exhibit the above-mentioned characteristics, the area of the gap must be large until the relative angular displacement between the valve body and the casing reaches a predetermined value. , it is required that the relative angular displacement exhibits a gradual change state as the relative angular displacement increases, and thereafter shows a rapid change state.

Therefore, conventional hydraulic control valves have realized the above-mentioned change in gap area by forming notches at the corners between both side walls of the long groove of the valve body and the outer peripheral surface of the valve body. Various proposals have been made. For example, in the hydraulic control valve disclosed in Japanese Unexamined Patent Publication No. 57-949, as shown in FIG. In the axial cross section, from a first straight portion 9a that has an intersecting angle close to a right angle and continues to the outer circumferential surface, and a second straight portion 9b that also has an intersecting angle close to a right angle and continues to the side wall. A notch 9 is formed in which the casing 1 and the valve body 2 are connected.
Due to the relative angular displacement between During this period, the area of the gap 8 changes gradually, and after the relative angular displacement exceeds this, a similar rapid change occurs.

In addition, in the hydraulic control valve disclosed in Japanese Patent Application Laid-open No. 58-116265, as shown in FIG. A notch 9.9 is formed in each of the parts, each of which is formed of a single straight line in the axial cross section and has a different width in the circumferential direction on the outer circumferential surface, and both notches 9,9 are formed respectively. The purpose is to obtain a desired area change state as a result of combining the area change states of the gaps 8, 8.

[Problem to be solved by the invention]

However, the notch 9 disclosed in JP-A-57-949 has a rotation axis perpendicular to the axis of the valve body 2, and has a ground surface shape corresponding to the axial cross-sectional shape of the notch 9. It must be formed by grinding using a special rotating grindstone.
It is difficult to improve the shape accuracy, and the widthwise dimensions of the notches 9 formed at the corners of each long groove 6 may differ from each other, making it impossible to obtain desired characteristics. There is a problem in processing that it is difficult to modify the shape of the notch 9 based on, for example, the results of a characteristic test. Further, on the surface of this notch 9, grinding marks are formed along the longitudinal direction of the long groove 6, in other words, in a direction perpendicular to the flow direction of the pressure oil, due to the grinding process.
Since the grinding marks are perpendicular to the flow direction of the pressure oil in the gap 8, there is a problem in that a harsh flow sound is generated.

On the other hand, the notches 9, 9 disclosed in Japanese Patent Application Laid-open No. 58-116265 have a simple axial cross-sectional shape, so machining and shape modification are easy, and the difficulties in machining are solved. These chamfered portions 9.9 form gaps 8, respectively.
. There is a drawback that a rapid change in area cannot be obtained in a large portion, and therefore a sufficient effect of improving characteristics cannot be expected.

The present invention has been made in view of the above circumstances, and it is possible to easily process the notch and modify the shape in order to obtain the above-mentioned area change state, and also to obtain a sufficient characteristic improvement effect. An object of the present invention is to provide a hydraulic control valve capable of reducing flow noise. [Means for solving the problem] A hydraulic control valve according to the present invention alternately communicates with a high pressure source and a low pressure source, and has a plurality of A cylindrical valve body having long grooves in the axial direction evenly distributed on its outer peripheral surface is communicated alternately with pressure oil supply holes in two different directions, and the same number of long grooves in the axial direction as the long grooves are formed. It is rotatably fitted into a cylindrical casing that is equally spaced on the inner circumferential surface of the valve body, and the flow of pressure oil through the gap between the long groove of the valve body and the long groove of the adjacent casing is controlled. , in a hydraulic control valve that is controlled according to a relative angular displacement of the valve body with respect to the casing, corner portions on the valve body side facing each other across the gap on both sides of the long groove communicating with the high pressure source, or corner portions on the casing side. The first cutout portion has an arcuate or linear axial cross-sectional shape, or intersects a circular arc portion parallel to the circumferential surface of the valve body or casing in the axial cross-section at an angle close to perpendicular to the circumferential surface. A second notch portion having a straight line portion is formed, and at least one of each of the first notch portion and the second notch portion is provided.

[Effect]

In the present invention, the desired change in the entire hydraulic control valve is achieved as a result of combining the change in the gap area in the portion where the first notch is formed and the change in the gap area in the portion where the second notch is formed. A characteristic in which when an area change state is obtained and the relative angular displacement between the valve body and the casing is small, the pressure difference in the hydraulic cylinder gradually increases approximately linearly with respect to an increase in the relative angular displacement, and the relative angle When the displacement is large,
Similarly, the characteristic that the pressure difference rapidly increases is realized.

〔Example〕

The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a front sectional view of a hydraulic control valve according to the present invention shown together with a hydraulic circuit diagram of a power steering device, and FIG. 2 is a partially enlarged sectional view of FIG. 1.

In the figure, 1 is a cylindrical casing, and a cylindrical valve body 2 having an outer diameter that is approximately the same as the inner diameter is attached to the casing 1 and is coaxial with the cylindrical valve body 2, which rotates around the axis. It is fitted inside so that it can move freely. For example, when this hydraulic control valve is applied to a power steering system of an automobile equipped with a rack-and-binion type steering mechanism, a lower part of an input shaft (not shown) whose upper end is interlocked with a steering wheel; The upper part of an output shaft (not shown) whose lower end is interlocked and connected to the pinion shaft in the steering mechanism is coaxially connected via a torsion bar 4, while the valve body 2 is connected to the input shaft. and the casing 1 is installed coaxially with the upper end of the output shaft, and the casing 1 is placed inside a cylindrical shaft body casing 3 surrounding the output shaft and the input shaft, It is supported so that it can rotate freely around the axis. Therefore, the torsion bar 4 is
As shown in the figure, an annular chamber located on the axis of the valve body 2 and formed between the torsion bar 4 and the inner surface of the valve body 2 serves as a return oil passage 20 to be described later.

On the inner peripheral surface of the casing I, eight long grooves 5, 5, . On the outer peripheral surface of
Eight long grooves 6°6... having a rectangular cross section and approximately the same axial dimension as the long grooves 5, 5... are formed equally spaced in the circumferential direction. The casing 1 and the valve body 2 are
When the torsion bar 4 is in an untwisted state (neutral state), as shown in FIG.
... and long grooves 6°6... are arranged in a staggered manner, and are positioned in the circumferential direction so that they communicate with each other through a slight gap 8.8 (see Fig. 2) on both sides in the width direction. .

Three annular grooves 7, 7.7 (only the central one is shown) are formed on the outer peripheral surface of the casing 1 at appropriate lengths apart in the axial direction. Pressure oil generated by a hydraulic pump P driven by the engine is introduced into the central annular groove 7, and the other two annular grooves 7 are connected to the rank shaft 70 in the steering mechanism. Partly, concentrically with this piston 7
The hydraulic cylinder S for steering assistance, which is constructed by fixing the hydraulic cylinder S to the hydraulic cylinder S, is connected to oil chambers S+ and S2 on both sides, respectively.

Of the eight long grooves 6, 6... of the valve body 2, the four long grooves 6, 6... located at every other position have openings on the outside of these grooves and open the casing I in the radial direction. These four long grooves 6,
6...Inside there is a central annular groove 7 and an oil introduction hole 10.1.
0..., pressure oil from the hydraulic pump P is introduced. In addition, the other four long grooves 6, 6...
・ is a return oil hole 1 formed in such a manner that it has an opening in each substantially central portion in the width direction and penetrates the valve body 2 in the radial direction.
3.13... communicate with the return oil passage 20, and the length a6.6 of these is connected to the return oil hole 13.
13... and a return oil passage 20 to communicate with the oil tank T maintained in an unpressurized state.

Furthermore, the four long grooves 15.5 located at every other position among the eight long grooves 5, 5, etc. of the casing 1 each have an opening at approximately the center in the width direction thereof. , a first oil outlet hole 11.11 formed radially through the casing 1.
... communicates with one of the annular grooves 7, 7 located on both sides, further communicates with one oil chamber S of the hydraulic cylinder S via the annular groove 7, and communicates with the other oil chamber S of the hydraulic cylinder S. The four long grooves 5.5... are communicated with the other annular groove 7 through similarly formed second oil outlet holes 12, 12... It is communicated with the other oil chamber Sg of the cylinder S. Therefore, a pressure difference occurs between the adjacent long grooves 5 and 5 between the oil chambers Sl+32 of the hydraulic cylinder S, and the hydraulic cylinder S applies hydraulic pressure corresponding to this pressure difference in the direction of the pressure difference. This hydraulic pressure moves the rank shaft 7o to assist the steering force.

In the hydraulic control valve configured as described above, when no steering torque is applied to the steering wheel and no torsion torque is acting on the torsion bar 4, that is, when it is in the neutral state, the long groove 6 .6... and the long grooves 5, 5... adjacent to these are communicated through gaps 8 of a constant width formed on both sides in the width direction, so that the pressure from the hydraulic pump P is reduced. Oil flows through the central annular groove 7 and oil introduction hole 1.
After being introduced into the long groove 6 through the long groove 6, it flows into the long groove 6 adjacent to each other on both sides of the long groove 5 in an evenly distributed manner, without creating a pressure difference between these long grooves 5. The oil is introduced into long grooves 6°6 adjacent to these on the opposite side, and is returned to the oil tank T via the return oil hole i3.13 and the return oil path 2°. As a result, both oil chambers 31 of the hydraulic cylinder S. The pressure in S2 is equal and the pressure in the hydraulic cylinder S
does not generate a steering assist force, the rank shaft 70 is moved to the center of its movement range by the resistance from the road surface acting on it through the wheels, and the wheels are maintained in a straight line.

On the other hand, when a steering torque is applied to the steering wheel and a relative angular displacement occurs between the casing 1 and the valve body 2 due to the torsion generated in the torsion bar 4, pressure oil from the hydraulic pump P is introduced. The areas of the gaps 8, 8 between the long groove 6 and the adjacent long grooves 5, 5 on both sides change. For example, if the valve body 2 is displaced relative to the casing 1 in the direction indicated by the white arrow in FIG.
The area of the gap 8 on the long groove 5 side that communicates with the second oil outlet hole 12 increases, while the area of the gap 8 on the long groove 5 side that communicates with the second oil outlet hole 12 decreases. As a result, in the hydraulic cylinder S, a pressure difference occurs such that the pressure in the oil chamber S+ is greater than the pressure in the oil chamber S2.

The increasing characteristic of this pressure difference with respect to the increase in steering torque depends on the state of change in the area of the gap 8 with respect to the increase in the relative angular displacement generated between the valve body 2 and the casing 1, as described above. In order to realize the desired area change state of the gap 8, in the hydraulic control valve according to the present invention, the oil introduction hole 1
Of the four long grooves 6, 6, . . ., two long grooves 6. Both side walls of 6 and valve body 2
As shown in an enlarged view in FIG. 3, first notches 60, 60 each having a single arcuate axial cross-sectional shape are formed at the four corners between the casing and the outer circumferential surface of the casing. 1 long groove 5
, 5... out of a total of 16 corners between the respective side walls and the inner peripheral surface of the casing 1, facing the gaps 8, 8... on both sides of the other two long grooves 6, 6... As shown in the enlarged view of FIG. 4, the four corners are formed with straight portions 50a that intersect with the inner circumferential surface of the casing 1 at an angle close to a right angle, and are concentric with the inner circumferential surface of the casing 1. A circular arc portion 50 parallel to the inner circumferential surface
The second cutout portions 50, 50 consisting of b are formed.

Therefore, the four long grooves 6, 6, . . . communicate with the high pressure source.
In the eight gaps 8.8 located on both sides of the gap 8, each of the four corners is placed at the corner on the valve body 2 side or the corner on the casing 1 side that face each other across the gap 8. This means that the first notch 60 or the second notch 50 is formed.

In FIG. 5, the horizontal axis represents the relative displacement angle between the casing 1 and the valve body 2, and the vertical axis represents the area of the gaps 8, 8,..., and the gaps 8, 8,... as the relative displacement angle increases. It is a graph showing the state of change in the area of . The curves indicated by broken lines in the figure indicate the gaps 8, 8, . . . formed by the first notch 60.
The curve showing the change in the area of the gaps 8, 8 at the two locations where the gap area decreases, and the curve shown by the dashed dotted line, also shows the change in area of the gaps 8, 8 at the four locations where the second notch 50 is formed. , 8... are shown, respectively, showing changes in area of the gaps 8, 8 at two similar locations, and among the eight gaps 8, 8..., the four gaps where the area decreases. The sum of the areas of 8, 8, . . . indicates a state of change as shown by the solid line obtained as a result of combining the two drawing lines.

As shown in this figure, the first notch 60 has a single arc shape.
The area of the gap 8.8 at the two locations where the gap 8.8 is formed gradually decreases approximately linearly as the relative displacement angle increases. The area of the gap 8.8 at the two locations where
In the range corresponding to the forming part of 0b, it is kept substantially constant as the relative displacement angle increases, and after the relative displacement angle exceeds 3.5°, the range corresponding to the forming part of the straight part 50a , similarly shows a rapidly decreasing state of change. Therefore, the eight gaps 8.8 obtained by synthesizing these
The total area of ... gradually decreases as the relative displacement angle increases in the range of 1.5' to 3.5 degrees, and 3.
In a range exceeding 5 degrees, the change state similarly rapidly decreases, and the desired area change state required for the power steering device is realized.

FIG. 6 shows a pressure difference generated between both arm chambers S+ and St of a hydraulic cylinder S for steering assistance in response to a steering torque applied to a steering wheel in a power steering system using a hydraulic control valve according to the present invention. This is a graph showing how the steering assist force generated by the hydraulic cylinder S changes. As shown in this figure,
Until the steering torque reaches a predetermined value shown as T1 in the figure, the pressure difference is maintained at approximately O, and
For steering torques between T and a predetermined value shown as T2 in the figure, the pressure difference gradually increases proportionally as the steering torque increases, and furthermore, for steering torques exceeding T2, the pressure difference increases proportionally as the steering torque increases. is applied to the steered wheels, the pressure difference increases rapidly as the steering torque increases. The predetermined value T1 corresponds to the steering torque at which the relative displacement angle between the casing 1 and the valve body 2 is 1.5 degrees, and the predetermined value T2 corresponds to the steering torque at which the relative displacement angle is 3.5 degrees. Needless to say, this corresponds to a steering torque of 5°.

Therefore, in the power steering system using the hydraulic control valve according to the present invention, the driver can:
By simply applying a steering torque that slightly exceeds the above Tt to the steering wheel, the large steering assist force generated by the hydraulic cylinder S makes it possible to easily steer the steering wheel, reducing the force required to operate the steering wheel, and while driving at high speed. , the stiffness corresponding to the above-mentioned T is given to the steering wheel, making it possible to realize high running stability, and the steering torque of T, ~T2 is gradually increased in proportion to the increase in road resistance. This provides a steering assist force that provides a comfortable steering feel.

The first notch 60 can be formed with a normal disk-shaped rotating grindstone having a rotation axis parallel to the axis of the valve body 2,
Further, the second notch 50 can be easily processed with high dimensional accuracy using a broaching machine using a broach having a cutting edge corresponding to the above-described cross-sectional shape. The second notch 50 formed in this way has machining marks in the direction perpendicular to the pressure oil feeding direction, but the first notch 60 has machining marks parallel to the pressure oil flow direction. Because of the machining marks, the flow noise generated when pressure oil flows through the gaps 8, 8, etc. is significantly reduced compared to conventional hydraulic control valves. Further, the area change characteristic as shown in FIG. The hydraulic pressure according to the present invention is realized only when the width of the first notch 60 in the circumferential direction of the body 2 and the width of the second notch 50 in the circumferential direction of the casing 1 correctly match. In the control valve, if a characteristic test after assembly reveals a characteristic defect due to a mismatch in the widths of both cutout portions, this defect can be easily resolved by modifying the shape of the first notch portion 60. Is possible.

FIG. 7 is a front sectional view of a part of a hydraulic control valve showing another embodiment of the present invention. The hydraulic control valve according to the present invention has the first notch 60 and the second notch at the corners of the valve body 2 side or the casing 1 side on both sides of the long grooves 6, 6 communicating with the high pressure source. In addition to these, as shown in this figure, a long groove 6, which communicates with a low pressure source, may be used.
Notches 61', 61... of appropriate shapes are formed in the corners of the valve body 2 side located on both sides of 6..., or similar notches are formed in the corners of the casing 1 side. Needless to say, these are also included in the present invention.

In this embodiment, the first notch 60 is formed on the valve body 2 side and the second notch 50 is formed on the casing 1 side in consideration of ease of machining. A first notch 60 is formed on the side, and a second notch 5 is formed on the valve body 2 side.
0 may be formed, and furthermore, a first notch 60 and a second notch 50 may be formed in either the casing l or the valve body 2.
may be formed.

Further, in this embodiment, the first notch 60 is shaped like an arc, but the state of change in the gap area that is approximately equal to the state of change in the gap area shown by the broken line in FIG. The first notch 60 may have a straight shape since it can also be obtained by forming a straight line or a combination of a plurality of straight lines. Further, the arc portion 50 in the second notch 50
b is not limited to a circular arc concentric with the inner circumferential surface of the casing 1 as shown in the embodiment, but is an arc substantially parallel to the inner circumferential surface, and the position where the second notch 50 is formed As shown by the dashed line in FIG. It is fine as long as it does not change.

Further, in this embodiment, the gap 8 on both sides of one long groove 6 is
．． Although the same type of notch portions are formed in 8, different types of notch portions may be formed, and the number of first notch portions 60 and second notch portions 50 to be formed is not limited to the same number. It is sufficient that at least one of both is formed.

Further, the application of the hydraulic control valve according to the present invention is not limited to the power steering device shown in this embodiment, but can be applied to any application requiring the above-mentioned pressure difference change characteristics.

〔effect〕

As detailed above, in the hydraulic control valve according to the present invention,
A first notch and a second notch are formed in a corner on the valve body side or a corner on the casing side that face each other across a gap formed on both sides of a long groove of the valve body communicating with a high pressure source. Therefore, in the entire gap, when the relative angular displacement between the valve body and the casing is small, the area changes gradually in proportion to the increase, and when the relative angular displacement is large, the area changes rapidly. Since a changing state can be obtained, when this is applied to a power steering system, almost no steering assist force is generated until a predetermined steering torque is applied to the steering wheels.
Appropriate rigidity is imparted to the steering wheels to improve driving stability, and after that, a steering assist force approximately proportional to road resistance is obtained, a comfortable steering feeling is achieved, and the steering torque is maintained at the predetermined value. After reaching another predetermined value greater than , a rapidly increasing steering assist force is obtained, and there is no need to apply steering torque exceeding the predetermined value when driving at low speed or when stopping, and the force required to operate the steering wheel. can be significantly reduced. Further, the first notch and the second notch for realizing the above-mentioned area change state can be easily formed with high dimensional accuracy, and the shape can be easily adjusted to improve characteristics. , since the first notch can be formed using a machining method that creates machining marks parallel to the flow direction of pressure oil, the flow noise caused by the flow of pressure oil is significantly reduced, etc. The invention has excellent effects.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a front sectional view of a hydraulic control valve according to the present invention shown together with a hydraulic circuit diagram of a power steering device, and FIG. 2 shows a state in which a notch is formed. 1 is a partially enlarged sectional view, FIGS. 3 and 4 are partially enlarged sectional views showing the shapes of the first notch and the second notch, respectively;
FIG. 5 is a graph showing how the gap area changes, and FIG. 6 is a graph showing how the steering torque applied to the steering wheel and the oil chambers of the hydraulic cylinder for steering assistance are applied in the power steering system using the hydraulic control valve according to the present invention. FIG. 7 is a partially enlarged sectional view showing another embodiment of the present invention, and FIGS. 8 and 9 show the shape of the notch in a conventional hydraulic control valve. The figure shown in FIG. 10 is a graph showing changes in the gap area in a conventional hydraulic control valve. 1...Casing 2...Valve body 4...Torsion bar 5.6...Long groove 8...Gap
1o...Oil introduction hole 11.12...Oil outlet hole
13... Return oil hole 20... Return oil path 50...
Second notch 60...First notch P...
Hydraulic pump S...Hydraulic cylinder patent Applicant Koyo Seiko Co., Ltd. Agent Patent attorney Noboru Kono No. 3 Fig. N 4 Fig. eq) Fig. 5 TI T2 Steering torque Fig. 6 Fig. 8 Fig. N 9

Claims (1)

[Claims] 1. A cylindrical valve body that alternately communicates with a high pressure source and a low pressure source and has a plurality of long grooves in the axial direction equally distributed on its outer circumferential surface,
The casing is rotatably fitted into a cylindrical casing which alternately communicates with pressure oil supply holes in two different directions and has the same number of long grooves in the axial direction as the long grooves evenly distributed on its inner peripheral surface. , a hydraulic control valve that controls the flow of pressure oil through a gap between a long groove of a valve body and a long groove of a casing adjacent thereto in accordance with a relative angular displacement of the valve body with respect to the casing; A first notch portion having an arcuate or linear axial cross-sectional shape, or a first notch portion having an arcuate or linear axial cross-sectional shape, at a corner portion on the valve body side or a corner portion on the casing side facing each other across the gap on both sides of the long groove communicating with the high pressure source; A second notch is formed on the circumferential surface of the body or casing, and has a circular arc portion parallel to the axial cross section and a straight line portion that intersects the circumferential surface at an angle close to a right angle; and at least one second notch.