JP2787163B2 - Hydraulic control valve - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary hydraulic control valve, and more particularly to a hydraulic control valve suitable for application to a hydraulic power steering device (power steering).

[Conventional technology]

BACKGROUND ART A hydraulic power steering device assists a force required for steering operation by an oil pressure generated by a hydraulic cylinder disposed in a steering mechanism, and includes an input shaft connected to a steering wheel, and a steering mechanism. And the output shaft connected to the output shaft is coaxially connected via a torsion bar, and when a steering torque is applied to the steering wheel, a relative angular displacement due to the torsion of the torsion bar is generated between the input shaft and the output shaft. According to the direction of the relative angular displacement, that is, the direction of the steering torque applied to the steering wheel, by the operation of the rotary hydraulic control valve formed at the connecting portion of the two shafts,
The direction in which hydraulic oil is supplied to the hydraulic cylinder is switched to generate a steering assist force in the hydraulic cylinder.

FIG. 5 is a schematic sectional view of a conventional hydraulic control valve. In the figure, reference numeral 36 denotes a casing, and 37 denotes a valve body. casing
Reference numeral 36 denotes a cylindrical shape, and concave grooves 36d, 36e, 36f, 36g extending in the axial direction are formed on the inner peripheral surface at four positions in the circumferential direction, and the concave grooves 36d, 36f communicate with each other. Hydraulic cylinder 4 through hole 36h
And the concave grooves 36e and 36g are connected to the other hydraulic chamber B of the hydraulic cylinder 4 via the communication holes 36i. The casing 36 has communication holes 36j and 36k penetrating between the concave grooves 36d and 36e and between the grooves 36f and 36g, respectively. The communication holes 36j and 36k are connected to the hydraulic pump P.
Valve chambers r ₁ , r ₂ formed between the casing 36 and the valve body 37 through the two communication holes 36j, 36k.
It is supplied to.

On the other hand, the valve body 37 is formed by forming a concave portion 37b in a state in which a predetermined length of arc surface 37a is left in the circumferential direction between each other at four equally spaced positions in the circumferential direction on the outer circumferential surface of the thick-walled cylindrical body. It is formed in a substantially square shape, and is accommodated in the casing 36 so as to be coaxially rotatable with the casing 36. In this state, the arc surface 37a of the valve body 37 contacts the inner peripheral surface of the casing 36, and each recess 37b and the casing 3
Valve chamber r ₁ surrounded by these between the inner peripheral wall of the 6 ~r
_The center hole 37d provided at the center is communicated with the oil tank T.

Each recess 37b in the valve body 37 is formed by cutting the outer peripheral surface of the thick-walled cylindrical body flat and surrounded by two sides perpendicular to the axis of the valve body 37 and two sides parallel to the axis. It has a rectangular shape.
A pair of recesses 37b, 37b corresponding to the center of rotation of the valve body 37 is provided with a communication hole 37e projecting from a hole 37d communicating with the oil tank T, and is provided with a valve chamber. The pressure oil returned to r ₃ and r ₄ is returned to the oil tank T via the communication hole 37e and the core hole 37d. 35 is a torsion bar.

Thus, in such a hydraulic control valve, the state where the hydraulic pressure is supplied from the pressure oil pump P to the valve chambers r ₁ and r ₂ through the communication holes 36 j and 36 k is maintained, and the steering wheel, the input shaft, the torsion bar
When the valve body 37 to rotate relative to the casing 36 through 35, the communicating area between the groove 36d~36g the valve chamber r ₁ ~r ₄ and the casing 36 varies depending on the relative angular displacement,
The pressurized oil in the valve chambers r ₁ and r ₂ is supplied to the concave grooves 36d, 36f and 36
e, 36g selectively flows into the valve chambers r ₃ , r ₄ from one of the other grooves at the same time, and the hydraulic oil returns to the valve chambers r ₃ , r ₄ . The steering assist force is generated.

[Problems to be solved by the invention]

By the way, in such a conventional power steering device using a hydraulic control valve, in the process of returning the steering wheel from a state where the steering wheel is rotated by a predetermined angle or more to the neutral position, a smooth return operation of the steering wheel is hindered in the initial stage. There was a problem that there is.

FIG. 6 shows the relative displacement angles (deg) of the input and output shafts when the conventional hydraulic control valve described above is used, and the casing 36.
Hydraulic pressure (kgf / c) in the valve chambers r ₁ and r ₂ formed between
m ² ), in which the horizontal axis represents the relative displacement angle and the vertical axis represents the hydraulic pressure (kgf / cm ² ).
In the graph, the relative displacement angle (deg) on the horizontal axis is common, the steering torque (kgf · cm) is on the vertical axis, and the hydraulic pressure (kgf / cm ² ) on the vertical axis is common. The steering torque (kgf
· Cm), the relationship between the relative displacement angle and the steering torque and the relationship between the steering torque and the hydraulic pressure are indicated by a chain line and a broken line, respectively.

As is clear from this graph, as the relative angular displacement of the input and output shafts increases, the hydraulic pressure in the valve chambers r ₁ and r ₂ also increases at a substantially predetermined ratio, but in a region where the relative displacement angle exceeds 3.5 °. ,
As for the steering torque, a hysteresis in a region exceeding 55 kgf · cm) becomes large, and a phenomenon that the hydraulic pressure fluctuates finely occurs.

Although this phenomenon has not been elucidated in detail, it is considered as follows.

In FIG. 5, the pressure oil from the hydraulic pump P is supplied to the annular groove 36b formed on the outer peripheral surface of the casing 36 as described above.
To the communication holes 36j, 36k and the valve chambers r ₁ , r ₂ from which the pressure oil is supplied to, for example, the hydraulic chamber A of the hydraulic cylinder 4, the concave grooves 36d, 36f and the communication holes 36h After that, it is supplied to the hydraulic chamber A. At the same time, the pressure oil in the hydraulic chamber B of the hydraulic cylinder 4 passes through the communication hole 37i and the concave grooves 36e and 36g, and the valve chambers r ₃ and r
_The flow returns to step ₄ , and from this, the oil is returned to the oil tank T through the communication holes 37e, 37e and the core hole 37d. Therefore, in the hydraulic control valve, the annular groove 36b connected to the hydraulic pump P, the communication holes 36j and 36k, and the valve chambers r ₁ and r
_2, concave grooves 36d, 36f, the communication hole 36h becomes high pressure region, whereas communication hole 36i leading to the oil tank T, the groove 36e, 36 g, the valve chamber r _3,
r ₄ , the communication hole 37e and the core hole 37d are in the low pressure region, as shown in FIG.

In FIG. 7, the hatched area is the high pressure area,
The area with a dot is the low pressure area. Of the casing 36,
Regarding the pressure balance outside, in the area facing the valve chambers r ₁ and r ₂ , the inside and outside of the casing 36 are in a high pressure area, whereas in the area facing the valve chambers r ₃ and r ₄ , The inside of 36 is a low pressure area, the outside is a high pressure area,
For this reason, as a result of the casing 36 being pressed inward in the region where the pressure difference between the inside and the outside of the casing 36 is large, the casing 36 is deformed into an elliptical shape as shown by a broken line 1 and the valve body 37 is tightened.

Therefore, in the process of rotating the input shaft to return the valve body 37 to the neutral position side, the valve body 37 is rotated in the casing 36 deformed into an elliptical shape, so that the valve body 37 and the casing 36 are rotated.
A “torsion” condition occurs between the
It is presumed that a sudden increase in the hysteresis and a change in the hydraulic pressure in the valve chamber as shown in the figure will occur.

The present invention has been made in view of such circumstances, and an object thereof is to reduce the influence of a large pressure difference between the inside and outside of a casing, to reduce valve clearance, and to reduce internal leakage of pressure oil. To provide an improved hydraulic control valve.

[Means for solving the problem]

The hydraulic control valve according to the present invention has a cylindrical casing formed with long grooves extending in the axial direction at four circumferential positions on the inner peripheral surface, and is fitted inside the casing so as to be coaxially rotatable therewith,
A valve body having a rectangular cross section with a recess formed to form a valve chamber between the casing and the casing at four locations in the circumferential direction, and a plurality of valve chambers through which pressure oil flows to a pressure oil source. In a hydraulic control valve which is sent to a long groove and is recirculated from another plurality of long grooves to a plurality of other valve chambers communicating with a low pressure source, the valve element has a substantially rectangular cross section and a valve communicating with the low pressure source. The length of the side facing the chamber is smaller than the length of the side facing the valve chamber that communicates with the hydraulic pressure source.

[Action]

According to the present invention, the area of the region where the high-pressure region and the low-pressure region are opposed to each other inside and outside the casing is reduced, and deformation of the casing is suppressed.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments.

FIG. 1 is a longitudinal sectional view of a hydraulic control valve according to the present invention, and FIG. 2 is an enlarged sectional view taken along line II-II of FIG. The input shaft 11 is connected to a steering wheel (not shown), and the output shaft 12 is engaged with the rack 3a of the rack shaft 3 via a pinion 13 provided here. The rack shaft 3 has both ends connected to steering wheels (not shown), and a hydraulic cylinder 4 having the rack shaft 3 as a piston rod is formed near an end opposite to the position where the rack portion 3a is formed. Have been.

The hydraulic cylinder 4 is provided with a piston 4a on the rack shaft 3 and a cylinder 4b integrated with the housing 5 on the outer periphery thereof.
The hydraulic chambers A and B on both sides of the piston 4a communicate with ports 1a and 1b of a hydraulic control valve 1 opened on the peripheral wall of the housing 5, respectively. A steering assist force is generated for the right side by the supply of the hydraulic pressure into A, and a left side by the supply of the pressurized oil to the hydraulic chamber B.

The input shaft 11 and the output shaft 12 are a common housing 5 having a cylindrical shape.
Are separately supported inside, and are rotatable coaxially. The input shaft 11 is a hollow shaft as shown in FIG.
Numeral 12 has a cylindrical portion at its upper part. The lower end of the input shaft 11 is inserted into this cylindrical portion at an appropriate length, and is supported by a bearing bush internally fitted and fixed in the cylindrical portion. ,
The output shafts 11 and 12 are connected to each other via a torsion bar 15 that is pin-joined to each of the output shafts.

Therefore, the steering torque applied to the steering wheel is transmitted to the output shaft 12 via the input shaft 11 and the torsion bar 15, and the input shaft 11 and the output shaft
12, a relative angular displacement with respect to the steering torque is generated.

The hydraulic control valve body is formed integrally with a cylindrical casing 16 rotatably fitted in the housing 5 and at an intermediate portion of the input shaft 11, and inside the casing 16 in the axial direction with the casing 16. And a valve element 17 fitted so as to be aligned. The casing 16 is provided inside the housing 5.
The pin 12a rotates around the axis in conjunction with the output shaft 12, and the valve body 17 rotates around the axis in conjunction with the input shaft 11, so that the casing 16 and the valve body 17, a relative angular displacement corresponding to the relative angular displacement between the input and output shafts 11 and 12 occurs.

On the outer peripheral surface of the casing 16, three annular grooves 16a, 16b, 16c are formed at appropriate intervals in the axial direction, and the central annular groove 16b is a hole and a port that penetrate the housing 5 in and out. Via 1c, it is connected to a hydraulic pump P which is a hydraulic pressure generating source, and the hydraulic pressure generated by the hydraulic pump P is introduced here.

The annular grooves 16a and 16c on both sides are connected to the hydraulic chambers A and B of the hydraulic cylinder 4 for assisting steering through holes penetrating the housing 5 in and out and respective ports 1a and 1b. Inside the housing 5 is a reflux chamber above the casing 16.
The reflux chamber 18 is connected to the oil tank T by a port 1d penetrating the housing 5 in and out.

On the other hand, as shown in FIGS. 1 and 2, four grooves 16d to 16g are provided on the inner circumferential surface of the casing 16 at predetermined positions in the circumferential direction including positions corresponding to the ports 1a and 1b of the housing 5 in the axial direction. The grooves 16d and 16f are formed over the length (about 20 mm), and the oil flows into the hydraulic chamber A of the cylinder 4 through the communication holes 16 and the grooves 16d and 16f.
e and 16g are respectively connected to the hydraulic chamber B of the hydraulic cylinder 4 via the communication holes 16i. The casing 16 has a groove.
Between 16d, 16e and 16f, 16g, two communication holes 16j, 16k penetrating inward and outward are formed at two locations 180 ° apart in the circumferential direction, and these are communicated with the hydraulic pump P, respectively. The pressure oil is supplied to the valve chambers r ₁ and r ₂ formed between the valve body 37 and the valve body 37 through the two communication holes 16j and 16k.

On the other hand, the valve body 17 has a circular arc surface 17 of a predetermined length between the outer peripheral surface of the input shaft 11 forming a thick-walled cylindrical body at four positions in the circumferential direction.
The recess 17b is formed in a state where a is left, the section is formed in a rectangular shape, and is accommodated in the casing 16 so as to be rotatable coaxially.In this state, the arc surface 17a of the valve body 17 is the inner peripheral surface of the casing 16. in contact, also these by being formed a valve chamber r ₁ ~r ₄ enclosed, Kokoroana 17d oil tank is further provided in the center between an inner peripheral surface of the recess 17b and the casing 16 T
Is communicated to. The recess 17b in the valve body 17 is formed by cutting the outer peripheral surface of the thick-walled cylindrical body flat to be orthogonal to the axis of the valve body 17.
It is surrounded by two sides parallel to the sides and the axis, has a rectangular shape in plan view, and has two sides in a direction orthogonal to the axis in each of the recesses 17b facing the valve chambers r ₃ and r _4. Is shorter than two sides of each recess 17b facing the valve chambers r ₁ and r ₂ in the same direction.

The valve chamber r _3, r is the set of recesses 17b facing the ₄ in as shown in FIG. 2, a communication hole 17e penetrating the outer, the valve chamber r ₃ to form 17e, r ₄
Are communicated with the communication hole 17e and the core hole 17d.

The length d ₁ of two sides of the recess 17b facing the valve chambers r ₁ and r ₂ and the recess 17b facing the valve chambers r ₃ and r ₄ in a direction orthogonal to the axis of each valve element. , d ₂ ratio is not particularly limited,
It can be set as needed.

Thus, in such a product of the present invention, when the steering torque for the steering wheel is transmitted to the valve body 17 through the torsion bar 15 and the valve body 17 is rotated in the casing 16, the port 1c is communicated from the hydraulic pump P to the port 1c. hole 16j, the valve chamber r ₁ formed between the recess 17b of the casing 16 and the valve body 17 via a 16k, r ₂
The hydraulic pressure introduced into the groove 16d, 16f or 16e, 1
6g flows into _{one of} the valve chambers r ₁ , r ₂ depending on the communication area, and is supplied to the hydraulic chamber A or B of the hydraulic cylinder 4,
The pressure oil in the hydraulic chamber B or A of the hydraulic cylinder 4 is
The fluid is returned to the valve chambers r ₃ , r ₄ via the other one of 16g or 16d, 16f, and then returned to the hydraulic cylinder T via the communication holes 17e, 17e and the core hole 17d.

FIG. 3 shows the pressure distribution inside and outside the casing 16 of such a product of the present invention. FIG. 3 is a pressure distribution diagram as shown in FIG. 7, in which the hatched area is the high pressure area and the dotted area is the low pressure area. As is apparent from these figures, the area of the casing 16 in which the pressure difference between the inside and outside is large, that is, the area where the outside pressure is large and the inside pressure is small, is that the valve body 17 has a rectangular cross section and the valve chambers r ₃ , r _{3 By making} the side length on the side facing ₄ shorter than the side length on the side facing the valve chambers r ₁ and r ₂ , the side length becomes smaller and the deformation of the casing 16 can be reliably suppressed.

FIG. 4 shows the relative angles (deg) of the input and output shafts and the hydraulic pressure in the valve chambers r ₁ and r ₂ formed between the casing 16 and the valve element 17 for the product of the present invention corresponding to FIG. And the relative displacement angle is plotted on the horizontal axis and the hydraulic pressure is plotted on the vertical axis.

In the graph, the horizontal axis represents the relative displacement angle (deg), the vertical axis represents the steering torque (kgfcm), the vertical axis represents the hydraulic pressure (kgf / cm ² ), and the horizontal axis represents the steering torque. (Kgfc
m), the relationship between the relative displacement angle and the steering torque and the relationship between the steering torque and the hydraulic pressure are shown by a dashed line and a broken line, respectively.

As is clear from this graph, as the relative angular displacement of the input and output shafts increases, the hydraulic pressure in the valve chambers r ₁ and r ₂ also increases at a predetermined ratio, and even in a region where the relative displacement angle exceeds 3.5 °. It can be seen that there is no change in hysteresis and no fibrillation of hydraulic pressure.

〔effect〕

As described above, in the product of the present invention, the deformation of the casing is reliably suppressed even when the relative displacement angle between the casing and the valve body increases, in other words, when the difference between the hydraulic pressures inside and outside the casing increases. The present invention exhibits excellent effects such as stable steering without the occurrence of "torsion" between the valve body and the effect of applying a power steering device or the like, which is extremely large. Things.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a hydraulic control valve according to the present invention, FIG. 2 is an enlarged sectional view taken along the line II-II of FIG. 1, and FIG. Illustrated illustration,
FIG. 4 is a graph showing the relationship between the relative displacement angles of the input and output shafts of the product of the present invention and the pressure in the valve chamber, FIG. 5 is a schematic cross-sectional view of the conventional product, and FIG. Is a graph showing the relationship between the relative displacement angle and the pressure in the valve chamber, and FIG. 7 is an explanatory diagram showing the pressure distribution inside and outside the casing of a conventional product. 1a, 1b, 1c… port, 3… rack shaft 4… hydraulic cylinder, 5… housing 11… input shaft, 12… output shaft 13… pinion, 15… torsion bar 16… casing 16a, 16b, 16c …… Circular grooves 16d, 16e, 16f, 16g …… Concave grooves 16h, 16i, 16j, 16k …… Communication holes 17 …… Valve, 17a …… Arc surface, 17b …… Concave, 17e …… Communication holes r _{1 to} r ₄ … Valve room

Claims (1)

(57) [Claims] A cylindrical casing having long grooves extending in the axial direction at four circumferential positions on an inner circumferential surface, and a cylindrical casing fitted in the casing so as to be coaxially rotatable therewith. A valve body having a rectangular cross section with a recess formed to form a valve chamber between the casing and the casing, and pressurized oil is sent out from the plurality of valve chambers communicating with a pressure oil source to a plurality of long grooves. And a hydraulic control valve adapted to recirculate from the other plurality of long grooves to a plurality of other valve chambers communicating with the low pressure source, wherein the valve element has a substantially rectangular cross section and faces the valve chamber communicating with the low pressure source. A hydraulic control valve characterized in that the side length of the side is smaller than the side side opposite to the valve chamber communicating with the hydraulic pressure source.