JPH0446791B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device equipped with a plate-type valve mechanism.

Conventionally, power steering devices equipped with rotary type or spool type valve mechanisms have been widely used, but these valve mechanisms themselves are not only complex and relatively long, but also require high precision valve mechanisms. It has the disadvantage of being expensive due to the size required.

Therefore, the applicant has proposed a power steering system equipped with a new plate-type valve mechanism, which is completely different from conventional rotary-type or spool-type valve mechanisms, with the aim of simplifying and downsizing the valve mechanism configuration. is proposed.

By the way, a power steering device equipped with such a plate-type valve mechanism has a sliding surface of a valve plate that is rotated integrally with a stub shaft, and a pinion shaft that is in relative sliding contact with this sliding surface. A hydraulic oil passage switching mechanism with a special shape is formed between the end face of the cylinder and the supply hole and the discharge hole. multiple oil passages through which hydraulic oil is supplied and discharged,
The pinion shaft is configured such that one end thereof opens into the oil passage switching mechanism, and the opening area of the oil passage switching mechanism is changed by rotating the valve plate. Hydraulic oil is supplied to and discharged from two working chambers. Therefore, in a power steering device having such a configuration, the shape of the oil passage switching mechanism must be machined with high dimensional accuracy because the flow rate of hydraulic oil must be appropriately controlled. It is necessary to

Conventionally, due to such a need, the oil passage switching mechanism section has been molded with high precision by an electric discharge machining method, a precision forging method, or the like.

However, the electrical discharge machining method has the disadvantage that machining costs are high, and the precision forging method has the drawback that it is difficult to manage dimensional accuracy.

The present invention has been made in view of such conventional drawbacks, and provides first and second oil passages constituting an oil passage switching mechanism section on the end surface side of the pinion shaft where the valve plate slides. By opening the hole in a circular shape, the first and second holes can be formed by an inexpensive process such as drilling or end milling.
This paper attempts to propose a power steering device that can form each of the oil passages.

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

The first is a sectional view of a main part of a power steering device showing an embodiment of the present invention. That is, in the power steering device according to the present invention, the interior of the cylinder 2 is divided into two, a first working chamber 3 and a second working chamber 4, by the piston 1 (see FIG. 2), and the piston 1 is provided with a rack 1a for driving a control link (not shown). 5
6 has a pinion 5a that meshes with the rack 1a at one end, and a pinion shaft protruding from the cylinder 2 at the other end; The housing 6 is provided with a supply hole 7 and a discharge hole 8 for hydraulic oil, and the hydraulic oil is supplied to each of the first and second actuators through the supply hole 7 and the discharge hole 8. The air is selectively supplied to and discharged from the chambers 3 and 4 to assist the steering operation of the rack 1a provided on the piston 1.

The pinion shaft 5 is rotatably supported by the cylinder 2 and housing 6 via bearings 9 and 10. Further, as shown in FIGS. 3a and 4, the head portion 5b at one end of the pinion shaft 5 is provided with a bearing hole 5c and a radial long groove 5d into which a flange 13a of the stub shaft 13, which will be described later, is inserted. It is being Furthermore, the head 5b
On the other end side end surface 5b', at least one (in this embodiment, two supply passages 5e, 5e) and at least one set (in this embodiment, two sets corresponding to two supply passages 5e, 5e) are provided. The first and second oil passages 5 of
f and 5g are open. The first and second oil passages 5f and 5g are connected to the supply passage 5.
They are respectively disposed at positions in the circumferential direction sandwiching one of the elements 5e and 5e. In addition, each oil passage 5f, 5g
The shape of the other end side end surface 5b' of the pinion shaft 5 is circular so that it can be processed by an inexpensive processing method such as drilling or end milling (see Figures 3a and 4). ). In addition, in this embodiment, the first and second oil passages 5f, 5
g are small circular holes 5f ₁ and 5g ₁ having a predetermined diameter;
and large circular hole portions 5f ₂ and 5g ₂ that are larger than these.

Of these oil passages 5f and 5g, one first oil passage 5f supports an annular cavity 11 formed between the pinion shaft 5 and the inner circumferential surface of the housing 6, and rotatably supports the pinion shaft 5. It communicates with the first working chamber 3 through a bearing 10 and a passage 2a formed in the cylinder 2, and the other second oil passage 5g directly communicates with the second working chamber 4. ing. Moreover, the two supply passages 5e, 5e are
One end is opened on the outer peripheral surface of the pinion shaft 5,
The housing 6 communicates with the supply hole 7 through an annular groove 12 formed on the inner circumferential surface thereof. In addition, 5 hours
... is a screw hole for connecting a color plate 19, which will be described later, and 5i is a positioning pin hole of the color plate 19.

A stub shaft 13 has one end connected to a steering wheel (not shown), and the stub shaft 13 is rotatable by a bearing hole 5c of the pinion shaft 5 and a bearing 14 attached to an end of the housing 6. It is supported and connected to the pinion shaft 5 via a torsion bar 15 having flexibility. 16a and 16b are pins that respectively fix both ends of the torsion bar 15, and 17 is a shaft seal that seals the stub shaft 13. The stub shaft 13 is also provided with at least one radial flange 13a, which is loosely fitted into the long groove 5d of the pinion shaft 5 with a desired rotational direction. Therefore, even if hydraulic oil is not supplied to the working chambers 3 and 4 due to a failure of the pump or the like,
The rotational force of the steering wheel is transmitted to the pinion shaft 5 with a slight play angle, allowing so-called normal manual operation. Furthermore, a driving pin 13b is implanted in the radial direction of the stub shaft 13 to connect the stub shaft and a valve plate 18, which will be described later, so as to be integrally rotatable.

A valve plate 18, which is rotated integrally with the stub shaft 13 by the drive pin 13b of the stub shaft 13, is disposed in sliding contact with the other end surface 5b' of the head 5b of the pinion shaft 5. As shown in FIGS. 3b and 5, the valve plate 18 is formed with a center hole 18a into which the stub shaft 13 is loosely fitted, and an engagement groove 18b into which the drive pin 13b is inserted and engaged. Further, a sliding surface 18c that is in sliding contact with the other end side end surface 5b' of the pinion shaft head 5b is provided with one of the supply passages 5e formed in the pinion shaft 5 and at least one set of first and second supply passages 5e. each oil passage 5f,
A first recess 18d that is not open to the outer periphery and communicates with a part of each pinion shaft 5, and at least one set of first and second recesses disposed on both sides of the first recess 18d in the circumferential direction. Second and third recesses 18e and 18f are formed in portions of the oil passages 5f and 5g, respectively, and are open to the outer periphery. Note that in this embodiment, the first,
Between each of the second recesses 18d and 18e and between each of the first and third recesses 18d and 18f, there are
Large circular hole portions 5f ₂ , 5 constituting each oil passage 5f, 5g
Circular parts 18i, 18j at least smaller than g ₂
is formed.

As shown in FIG. 5, the first concave portion 18d is located in each large circular hole portion 5 of the first oil passage 5f and the second oil passage 5g.
a wide fan-shaped recess 18d ₁ having a radial width ₂ approximately equal to the diameter width ₁ of f 2 _{and 5g 2 and formed approximately concentrically with each of the large circular holes 5f 2 and 5g 2} ;
Continuing with the wide fan-shaped recess _18d1 , its radial width
When _the valve plate 18 shown in _FIG . _6a is rotated and is in the standard position, the first oil passage 5f is The opening area Y ₁ of the wide fan-shaped recess 18d ₁ for the second oil passage 5g has a larger opening area than the opening area _{X 1 of} the narrow fan-shaped recess 18d 2 for the second oil passage 5g. Part of the oil passages 5f and 5g of No. 2 are in communication with each other. The reason why the opening areas X ₁ and Y ₁ are different in this way is that the effective pressure receiving area applied to the piston 1 in the cylinder 2 is different from the cross section of the rack 1a between the first working chamber 3 side and the second working chamber 4 side. Since the integral is smaller on the second working chamber 4 side than on the first working chamber 3 side, the narrow fan-shaped recess 18 with respect to the first oil passage 5f
By making the opening area Y ₁ of the wide fan-shaped recess 18d ₁ for the second oil passage 5g larger than the opening area X ₁ of the opening d ₂ , the pressure of the hydraulic oil guided from the former to the first working chamber 3 is lower. , the pressure of the hydraulic oil guided from the latter to the second working chamber 4 is increased, and the difference in the effective pressure receiving area is canceled out by the difference in these pressures.
This is to make the steering assist force in the left and right directions the same.

Further, for the same reason, the radial width ₄ of the wide fan-shaped recess 18e ₁ of the second recess 18e is approximately equal to the diameter width ₁ of the large circular hole 5f ₂ of the first oil passage 5f.
Conversely, the narrow fan-shaped recess 18f ₁ of the third recess 18f
The radial direction ₅ is the large circular hole 5 of the second oil passage 5g.
It is formed smaller than the diameter width ₁ of g ₂ .

In addition, in this example, as shown in FIG.
Annular step portions 5f ₃ , 5g ₃ are formed between the large circular hole portions 5f ₂ , _{5g 2} and _{the small circular hole portions 5f 1 ,} 5g ₁ . , was formed to approximate the ideal hydraulic characteristics of hydraulic fluid.
That is, as shown in FIG. 7, the ideal hydraulic characteristics of the hydraulic fluid during normal running are a straight line with a predetermined inclination angle corresponding to the torsion angle of the torsion bar 17, as shown by a in the figure. It is desirable for the oil pressure to be high. However, as shown in FIG. 8a, the hydraulic characteristics of the hydraulic fluid differ from the valve plate 18.
It is determined by the size of the opening area of the narrowest part S between the circular parts 18i, 18j formed in the circular parts 18i, 18j and the first or second oil passage 5f, 5g. When the opening area is small, the oil pressure will be high. Therefore, as shown in a in Figure 8,
If a stepped portion is not formed in the first or second oil passage 5f, 5g, even if the valve plate 18 is gradually moved in the direction of arrow A in the figure from _S1 to _S2 , _S3 ... , the opening area hardly changes corresponding to the amount of movement, and the outer circumferential surface 18 of the circular parts 18i, 18j
From the time when i ₁ , 18j ₁ approaches the inner circumferential surface of the large circular hole portions 5f ₂ , 5g 2 of the first or second oil passages 5f, _5g , the opening area thereof rapidly decreases. Therefore, as shown by b in Fig. 7, the torsion bar 1
Even if the torsion angle of the torsion bar 17 increases, the oil pressure hardly increases, and only non-ideal oil pressure characteristics can be obtained in which the oil pressure suddenly increases near the maximum torsion angle of the torsion bar 17. On the other _hand , as in this embodiment, as shown in FIG _. 18 in the direction of arrow A in the same figure, the opening area of the narrowest part S rapidly becomes narrower from the point where the circular parts 18i, 18j approach the step parts 5f ₃ , 5g ₃ , and then the opening area remains almost the same. will be maintained. Therefore, as shown by C in FIG. 7, it is theoretically possible to obtain hydraulic characteristics that increase rapidly in response to the torsion angle of the torsion bar, and therefore, as shown by d in FIG. , it is possible to obtain actual hydraulic characteristics that are close to the ideal hydraulic characteristics a.

Reference numeral 19 denotes an annular collar plate, and as shown in FIG. It is formed. Also, this color plate 19
The valve plate 18 and the bearing 20 that controls the smooth rotation of the valve plate 18 are housed in the inner circumference of the pinion shaft, and the shaft plate 21 axially closes the inside of the valve plate 18. It is fixed at 5. 22... are these color plates 19 and shaft plates 2
Bolt 23 for fixing 1 to the pinion shaft 5
is a positioning pin between the collar plate 19 and the pinion shaft 5.

An annular chamber 24 communicating with the discharge hole 8 is formed between the outer periphery of the collar plate 19 and the shaft plate 21 and the inner periphery of the housing 6. Further, a thrust bearing 2 is connected between the shaft plate 21 and the housing 6 via a shim 25.
6 are arranged.

Next, the operation of the power steering device according to the present invention having the above configuration will be explained.

First, a description will be given of the case where the steering wheel (not shown) does not rotate and is in the standard position. In this case, the stub shaft 13 and the valve plate 18 connected thereto by the drive pin 13b do not rotate and are The first and second oil passages 5f and 5g formed in the pinion shaft 5 and the valve plate 1
8 first, second, and third recesses 18d, 18e,
The relative positional relationship with 18f is as shown in FIG. 6a. Therefore, the hydraulic oil supplied from a pump (not shown) is sequentially supplied from the supply hole 7 to the annular chamber 12 formed on the inner peripheral surface of the housing 6, and then to the pinion shaft 5 whose one end is open to the annular chamber 12. Supply passages 5e, 5e, each supply passage 5
Valve plate 1 whose other ends e and 5e are open
This first recess 18d passes through the first recess 18d of No.8.
and first and second oil passages 5f and 5g formed in the pinion shaft 5 which are in open communication with each other at both ends thereof. These first and second oil passages 5f and 5g communicate with the first and second working chambers 3 and 4 in the cylinder 2, so
The hydraulic oil that has reached each of the oil passages 5f and 5g attempts to flow into each of the working chambers 3 and 4, but a portion of each of the first and second oil passages 5f and 5g simultaneously flows into the valve plate 18. Since the openings are in communication with both the second and third recesses 18e and 18f formed in the color plate 19, the color plate The annular chamber 24 is formed between the outer circumferential surface of the housing 19 and the inner circumferential surface of the housing 6 . Therefore, the hydraulic oil is discharged from the discharge hole 8 communicating with the annular chamber 24 to a tank chamber (not shown). Therefore, no oil pressure difference occurs between the first and second working chambers 3 and 4. Therefore, the piston 1 within the cylinder 2 does not move in the axial direction.

On the other hand, when a steering wheel (not shown) is rotated to rotate the stub shaft 13 clockwise or counterclockwise, the pinion shaft 5 connected to the stub shaft 13 via the torsion bar 15 will also rotate. However, in the initial rotation state of the stub shaft 13, the rack 1a is receiving ground resistance from the wheels via the control link connected to it, so the piston 1 and pinion shaft 5 remain stationary. If the torsion bar 15 remains in the same position, a torsion angle occurs in the flexible torsion bar 15, and relative rotation occurs between the pinion shaft 5 and the valve plate 18, which are integrally connected to the stub shaft 13 by the drive pin 13b. arise. Then, for example, when the valve plate 18 is rotated counterclockwise by rotating the stub shaft 13 from the standard position of the valve plate 18 shown in FIG. Road 5f
The opening area _X1 of the first recess 18d formed in the valve plate 18 with respect to the large circular hole _5f2 constituting the valve plate 18 is gradually reduced, and eventually the opening area X1 is reduced as shown in FIG. 6b. ₁ becomes zero. on the other hand,
On the contrary, the second oil passage 5 of the pinion shaft 5
The opening area _Y1 of the first recess 18d relative to the large circular hole _5g2 constituting g is increased, and the hydraulic oil from the supply passage 7 is transferred to the second oil passage 5 of the pinion shaft 5.
It is supplied only into the second working chamber 4 through g.
At the same time, the first oil passage 5 of the pinion shaft 5
Opening area X ₂ of the second recess 18e formed in the valve plate 18 with respect to the large circular hole 5f ₂ constituting f
will be gradually increased, so the hydraulic oil in the first working chamber 3 passes through the first oil passage 5f and the second recess 18e communicating with the first working chamber 3,
It flows into the annular chamber 24, passes through the discharge hole 8, and is discharged to a tank chamber (not shown).

Therefore, the hydraulic pressure in the first working chamber 3 is the same as that in the second working chamber 4.
This oil pressure difference causes the piston 1 to move leftward in the cylinder 2, and a sliding steering assisting force in the leftward direction is applied to the rack 1a provided on the piston 1. Therefore, the steering link is rotated in a predetermined direction via a side rod (not shown) by the action of this rack 1a, and the vehicle is steered counterclockwise.

Note that when the stub shaft 13 is rotated clockwise, the same operation as described above is performed, and in this case, the hydraulic pressure in the first working chamber 3 is transferred to the second working chamber 4.
The piston 1 moves to the right, and a sliding force in the right direction is applied to the rack 1a. In this way, the steering operation of the wheels is effectively assisted by the rotation operation of the steering wheel (not shown).

The power steering device according to the present invention operates in this way, but as described above, in the present invention, at least one set of first and second 2 each oil passage 5
Since the shapes of the oil passages f and 5g are circular, the oil passages 5f and 5g can be formed by an inexpensive processing method such as drilling or end milling. Therefore, a power steering device suitable for mass production can be obtained.

The present invention provides a pinion shaft with a supply passage for supplying hydraulic oil and first and second oil passages communicating with each working chamber of the cylinder, and these supply passages and each of the first and second oil passages. is opened at the end face of the pinion shaft and controls the supply and discharge of hydraulic oil together with the first, second, and third recesses formed in the valve plate, reducing the number of parts and making parts management easier. In addition to reducing man-hours and simplifying the structure, the first and second oil passages can be
Since the opening is circular rather than fan-shaped as in the past, and opened at the end face of the pinion shaft, the first and second oil passages can be formed quickly and easily using inexpensive processing methods such as drilling and end milling. It also has the effect of being able to be processed and molded.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the power steering device according to the present invention, Fig. 2 is a sectional view taken along the line - - in Fig. 1, and Fig. 3a is a partially omitted view showing the other end side of the pinion shaft. FIG. 3B is a perspective view showing the valve plate, FIG. 3C is a perspective view showing the collar plate, FIG. 3D is a perspective view showing the shaft plate,
Figure 4 is a front view showing the other end side of the pinion shaft, Figure 5 is a rear view of the valve plate, and Figure 6 is a rear view of the valve plate.
Figure a is an enlarged cross-sectional view taken along the - line in Figure 1;
Figure b is an enlarged sectional view showing the valve plate rotated counterclockwise relative to the pinion shaft;
Fig. 6C is an enlarged sectional view showing the valve plate rotated clockwise relative to the pinion shaft, and Fig. 7 shows the ideal hydraulic characteristics of the hydraulic oil, with a step in the first or second oil passage. Figure 8a is a characteristic diagram showing the hydraulic characteristics with and without forming
8b is a sectional view of the main part to explain the hydraulic characteristics when the step is not formed in the second oil passage, and FIG. FIG. 2 is a cross-sectional view of a main part for explanation. 1... Piston, 1a... Rack, 2... Cylinder, 3... First working chamber, 4... Second working chamber, 5
...Pinion shaft, 5a...Pinion, 6...
...housing, 5e...supply passage, 5f...first
Oil passage, 5f ₁ ... small circular hole section, 5f ₂ ... large circular hole section, 5
g...Second oil passage, 5g ₁ ...Small circular portion, 5g ₂ ...Large circular hole, 6...Housing, 7...Supply hole, 8...
Discharge hole, 18...Valve plate, 18d...First recess, 18e...Second recess, 18f...Third recess.

Claims (1)

[Claims] 1 A cylinder filled with hydraulic oil, a piston that separates the inside of the cylinder into a first working chamber and a second working chamber, one end of which has a pinion that meshes with a rack formed in the piston, and the other end of which is connected to the cylinder. a pinion shaft that projects outward; a housing that accommodates the other end of the pinion shaft and has a hydraulic oil supply hole and a discharge hole; and a stub shaft that is operatively connected to the other end of the pinion shaft; A valve plate is provided that rotates integrally with the stub shaft while sliding relative to the other end side end surface of the pinion shaft, and the other end side of the pinion shaft has a supply hole and a a supply passage communicating with the end surface, and first and second chambers each having one end communicating with each of the first and second working chambers, and the other end having a circular shape and opening at the other end side end surface of the pinion shaft. 2 oil passages, and a supply passage for the pinion shaft and the first and second oil passages are formed on the sliding surface of the valve plate with the other end side end surface of the pinion shaft.
a first recess that communicates with each of the oil passages of the pinion shaft, and second and third recesses that communicate the first and second oil passages of the pinion shaft with a discharge hole, respectively; Due to the relative rotation between the valve plate and the pinion shaft, the first and second
The first, second, and
A power steering device characterized in that supply and discharge of hydraulic oil to the two working chambers of the cylinder is controlled by changing the opening area of each third recess.