JPH0311101Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention is a so-called speed-sensitive power steering system that is mounted on a vehicle and assists the steering force of the steering wheel, and also reduces the assisting force according to the vehicle speed. Regarding the collecting device.

(Prior art) A type of power steering device includes a valve rotor that rotates integrally with a first shaft rotatably supported within a valve housing, and a valve rotor that is connected coaxially and rotatably relative to the first shaft by a predetermined amount. a valve sleeve that rotates integrally with the second shaft and is arranged concentrically around the outer periphery of the valve rotor; and a valve sleeve that is provided between the valve sleeve and the valve rotor and can switch the supply/discharge flow path to each oil chamber of the power cylinder. A power rudder comprising a rotary valve type control valve that operates the switching valve mechanism through relative rotation between the two shafts to control supply and discharge of hydraulic oil to each oil chamber of the power cylinder. There is a device to remove it.

Incidentally, in this kind of power steering device, the two shafts are generally connected by a torsion bar, so that relative rotation occurs between the two shafts. In addition, in this kind of speed-sensitive power steering device, as proposed in Japanese Patent Publication No. 54-9368, for example, an engagement recess provided on either side of the two shafts is used. A ball serving as a cam follower supported on one of the other shafts is engaged, and a hydraulic pressure that increases according to the vehicle speed is applied to this ball, so that the engagement force of the ball with the engagement recess is increased according to the vehicle speed. I have to. Accordingly, in such a power steering device, the relative rotation between the two shafts is gradually regulated according to the vehicle speed, so that the assisting force generated according to the degree of the relative rotation decreases according to the vehicle speed.

As described above, in this type of conventional speed-sensitive power steering device, the torsion bar is an essential component as a main component that connects both shafts so that they can rotate relative to each other. In order to control the relative rotation between the two axes, it is necessary to apply a considerably high hydraulic pressure to the ball.

(Purpose of the invention) The present invention was made to solve this problem, and its main purpose is to connect both shafts of this kind of power steering device with a cam surface provided on the inner shaft at the overlapping part. It is assembled with a C-shaped spring on the outer shaft and connected by engagement with a cam follower whose pressing force increases depending on the vehicle speed.The structure allows the torsion bar, which was conventionally considered indispensable, to be omitted, and the cam follower. The object of the present invention is to make it possible to lower the applied hydraulic pressure and to make it possible to easily change the steering force.

(Structure of the Device) In order to achieve the above object, the present invention provides a power steering device of this kind in which a portion of the two shafts are overlapped, and a pair of cam surfaces are provided around both sides of the outer periphery of the inner shaft. A pair of through holes are formed in the radial direction of the shaft and correspond to each of the cam surfaces, and a cam follower longer than the axial length of the same hole is slidably assembled into both of the through holes. At the same time, a C-shaped spring that surrounds these cam followers from the outside and elastically urges them radially inward is installed from the outside, and presses each of the cam followers against each of the cam surfaces. Both shafts are connected, and hydraulic pressure is applied to the outside or inside of each of the cam followers to increase or decrease pressure according to vehicle speed, so that the pressing force of each of these cam followers against each of the cam surfaces increases according to vehicle speed. Particularly noteworthy are its structural features.

(Operations and effects of the invention) As a result, in the present invention, the relative rotation between the two shafts can be regulated according to the pressing force between each cam follower and each cam surface that connect the two shafts to each other. A speed-sensitive power steering device in which the auxiliary force decreases in accordance with the vehicle speed can be constructed without using a torsion bar, and the device can be simplified and made more compact. Also,
In the present invention, since the C-shaped spring surrounds both cam followers from the outer periphery and elastically urges them radially inward, each cam follower assembled to both shafts is removed when the device is assembled. Not only does it not stick out in any direction, making it easy to assemble, but it also allows you to replace the C-shaped spring without disassembling both shafts, making it easy to change the spring force using the same spring. I was able to
It is possible to easily change the steering force (ie, adjust the steering characteristics). Furthermore, in the present invention, hydraulic pressure is applied to the outside or inside of each cam follower to increase or decrease the pressure according to the vehicle speed, so that the pressing force of each cam follower against the cam surface increases according to the vehicle speed. When applying hydraulic pressure to the outside of each cam follower that increases in accordance with vehicle speed, the direction of action of the hydraulic pressure and the direction of action of the spring become the same, making it possible to lower the hydraulic pressure compared to conventional methods. When a hydraulic pressure is applied to the inside of each cam follower to reduce the pressure according to the vehicle speed, the energy consumption required for generating the hydraulic pressure can be reduced by setting the hydraulic pressure to a low value at high speeds.

(Embodiment) Hereinafter, an embodiment of the present invention will be described based on the drawings. FIG. 1 shows a power steering system PS1 according to a first embodiment of the present invention. The power steering device is a rack and pinion type power steering device, and the power steering device includes an input shaft 12 rotatably supported within a valve housing 11 and a pinion shaft 14 rotatably supported within a gear housing 13. The two shafts 12 and 14 are fitted to be relatively rotatable between their end portions, and both shafts 12 and 14 are connected to each other via a cam follower and a spring, which will be described later. This input shaft 1
A portion inside the valve housing 11 at 2 is formed as a valve rotor 21, and a valve sleeve 22 is arranged concentrically around the outer periphery of the valve rotor 21. Further, the pinion shaft 14 is connected to the power cylinder 31
It is constantly engaged with the rack bar 15 that constitutes the rod.

The valve rotor 21 is connected to the input shaft 12
arcuate grooves 21a that are evenly formed at eight locations on the outer periphery of the valve sleeve 22 and extend in the axial direction;
It is provided with a communication groove 21b that reaches the oil chamber R1.

The valve sleeve 22 is a component of the switching valve mechanism together with the valve rotor 21.
1, and is integrally connected to the upper end of the pinion shaft 14 via a connecting pin 23 at its lower end. This valve sleeve 22 is provided with switching grooves 22a that are equally formed at eight locations on the inner circumference and extend in the axial direction. Of these switching grooves 22a, half of them communicate with the upper annular groove 22b provided on the outer periphery of the valve sleeve 22, and the remaining half communicate with the lower annular groove 22c provided on the outer periphery of the valve sleeve 22.
is connected to. This valve sleeve 22 is similar to a known valve sleeve, and the upper annular groove 22b communicates with the right oil chamber R3 of the power cylinder 31 via the supply/discharge passage 31a, and the lower annular groove 22c communicates with the supply/discharge passage 31a. 31b to the left oil chamber R4 of the power cylinder 31, and a central annular groove 22d provided on the outer periphery of the valve sleeve 22 communicates to a hydraulic pump (not shown) via a supply flow path 32a. Note that the first oil chamber R1 located above the valve sleeve 22 and having the communication groove 21b opens therein communicates with the tank of the hydraulic pump via the discharge passage 32b.

As a result, in the power steering device PS1, both shafts 12,
If relative rotation occurs between 14 and 14, the supply flow path 32a
The hydraulic oil supplied through the valve sleeve 22
central annular groove 22d, either one of the switching grooves 22
a, it is supplied into the right oil chamber R3 or left oil chamber R4 of the power cylinder 31 through the upper annular groove 22b or the lower annular groove 22c and either one of the supply/discharge channels 31a, 31b. At the same time, left oil chamber R4
Alternatively, the hydraulic oil in the right oil chamber R3 is supplied to the other supply/discharge channels 31b, 31a, the lower annular groove 22c or the upper annular groove 22b of the valve sleeve 22, the other switching groove 22a, the first oil chamber R1, and the discharge channel. 32b and is discharged into a tank. As a result, the steering force is assisted when turning the steering wheel to the right or left.

In this embodiment, as shown in FIGS. 1 and 2, the lower end of the input shaft 12 and the upper end of the pinion shaft 14 overlap with each other with the input shaft 12 inside. Parts of both sides of the outer periphery of the lower end of the shaft 12 are formed with cam surfaces 12a, 12a having a width across flats, and the upper end of the pinion shaft 14 has a cylindrical shape into which the lower end of the input shaft 12 can be inserted. An insertion hole 14a and cylindrical through holes 14b, 14b having substantially the same height as the cam surfaces 12a, 12a of the input shaft 12 are formed. The lower end of the input shaft 12 is a pinion shaft 14.
is rotatably inserted into the insertion hole 14a of the pinion shaft 14, and is assembled liquid-tightly and slidably in the radial direction into each through-hole 14b of the pinion shaft 14, and is fitted into each cam surface 12a at the inner end. In addition, a pair of cylindrical cam followers 24, 24 whose outer ends protrude a required amount outside each through hole 14b (that is, longer than the axial length of each through hole 14b) allow relative rotation and axial movement to the pinion shaft 14. Impossibly connected.

On the other hand, the pinion shaft 14 has its respective through holes 1
A pair of outward flange portions 14c, 14 above and below 4b.
d, and both of these flange portions 14c, 1
A cylindrical spring 25 having a C-ring shape in cross section is interposed between the springs 4d and 4d. This spring 25 surrounds each cam follower 24 from the outer periphery and elastically biases it in the radial direction, and the inner surface of each cam follower 24
4a is pressed against each cam surface 12a with a predetermined force. Further, both flange portions 14c, 14 of the pinion shaft 14 in the gear housing 13
d, a second oil chamber R2 is formed outside each cam follower 24. A hydraulic pressure that increases in accordance with the vehicle speed is applied to the second oil chamber R2, and each cam follower 24 is pressed against each cam surface 12a by this hydraulic pressure. Note that the hydraulic pressure generating means for generating such hydraulic pressure may be of a conventionally known type; for example, as shown in FIG. 1, a hydraulic pump 3 driven by a propeller shaft of a vehicle or the like is used.
3. Orifice 3 that generates oil pressure according to vehicle speed
4. It is possible to use means such as a relief valve 35 for regulating the maximum pressure. Therefore, a relative rotation occurs between the shafts 12 and 14 corresponding to the amount of outward sliding of each cam follower 24, and the steering force of the steering wheel is assisted. Thus, the pressing force on each cam follower 24 is increased in accordance with the vehicle speed, and the relative rotation between the shafts 12 and 14 is gradually regulated in accordance with the vehicle speed. Therefore, the assisting force on the steering wheel decreases according to the vehicle speed.

In this way, according to the power steering device PS1,
A speed-sensitive power steering device can be configured without using a torsion bar as a connecting member between the shafts 12 and 14, and the device can be simplified and made more compact. In addition, since the C-shaped spring 25 surrounds both cam followers 24 from the outer periphery and elastically biases them radially inward, each shaft 12, 1
It goes without saying that each cam follower 24 assembled to the shaft 4 does not protrude outward and can be easily assembled, and the C-shaped spring 25 can be replaced without disassembling both the shafts 12 and 14. Therefore, the spring force of the spring 25 can be easily changed, and the steering force can be easily changed (that is, the steering characteristics can be adjusted). Furthermore, since a hydraulic pressure is applied to the outside of each cam follower 24 that increases according to the vehicle speed so that the pressing force of each cam follower 24 against each cam surface 12a increases according to the vehicle speed, the direction of action of the hydraulic pressure and the action of the spring can be changed. Since the directions are the same, the oil pressure can be lowered compared to the conventional one.

FIG. 3 shows a modification of the first embodiment.
The power steering system PS1' of this modified example has substantially the same structure as the power steering system PS1 of the first embodiment, except for the shape of each cam follower 24A, the second oil chamber R2, and the oil pressure applied thereto. .

In the power steering device PS1', a second shaft is connected between the input shaft 12 and each cam follower 24A.
An oil chamber R2 is formed, and a hydraulic pressure that is reduced in accordance with the vehicle speed is applied to the second oil chamber R2. This oil pressure urges each cam follower 24A against the urging force of the spring 25 against each cam follower 24A, and thereby the pressing force of each cam follower 24A against each cam surface 12a increases in accordance with the vehicle speed. . Therefore, similarly to the first embodiment, the assisting force applied to the steering wheel decreases in accordance with the vehicle speed. Also,
In this embodiment, since a hydraulic pressure is applied to the inside of each cam follower 24A to reduce the pressure according to the vehicle speed, the energy consumption required for generating hydraulic pressure can be reduced by setting the hydraulic pressure to a low value at high speeds.

4 and 5 show a second embodiment of the power steering device according to the present invention. In the power steering system PS2 of the second embodiment, each of the cam surfaces 12b, 12b on both sides of the input shaft 12 is formed into an arcuate concave surface, and a portion of the inner surface 24b of each cam follower 24B is formed on each cam. Face 12
It is formed into an arcuate convex surface corresponding to b and 12b. Therefore, the restraining effect of each cam follower 24B on the input shaft 12 can be exerted more than the power steering system PS1 of the first embodiment.

6 and 7 show a third embodiment of the power steering device according to the present invention. In the power steering system PS3 of the third embodiment, a cam pin 12c is fixedly fixed to the lower end of the input shaft 12, and both ends of the cam pin 12c function as cam surfaces. Further, each cam follower 24C is provided with a recess 24c on the inside thereof, in which both ends of the cam pin 12c engage. For this reason,
The portion forming the cam surface of the input shaft 12 is located at a portion expanded in the radial direction, and the restraining effect on the input shaft 12 can be further increased.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a power steering device according to a first embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view taken along the line - in FIG. 1, and FIG. 3 is a modification of the same device. FIG. 4 is a partial longitudinal sectional view of the power steering device according to the second embodiment, FIG. 5 is an enlarged cross-sectional view taken along the line - in FIG. 4, and FIG. 6 is a third embodiment. FIG. 7 is an enlarged cross-sectional view taken along the - line in FIG. 6. Explanation of symbols, 11...Valve housing, 12
...Input shaft (inner shaft), 12
a, 12b...cam surface, 12c...cam pin, 1
4...Pinion shaft (outer shaft), 14
b... Through hole, 21... Valve rotor, 22...
Valve sleeve, 24, 24A-24C...cam follower, 25...C-shaped spring, 31...
power cylinder.

Claims (1)

[Scope of utility model registration request] a first rotatably supported within the valve housing;
a valve rotor that rotates integrally with the shaft;
a valve sleeve that rotates integrally with a second shaft coaxially connected to the shaft and capable of relative rotation by a predetermined amount and is arranged concentrically around the outer periphery of the valve rotor; and a power cylinder that is provided between the valve sleeve and the valve rotor. is provided with a switching valve mechanism capable of switching the supply/discharge flow path to each oil chamber of the power cylinder, and the switching valve mechanism is actuated by relative rotation between the two shafts to supply/discharge hydraulic oil to each oil chamber of the power cylinder. In a power steering device equipped with a rotary valve type control valve, a pair of cam surfaces are formed in the circumferential direction on a part of both sides of the outer periphery of the inner shaft by partially overlapping the two shafts, and A pair of through holes are formed in the radial direction of the shaft corresponding to each of the cam surfaces, and cam followers longer than the axial length of the holes are slidably attached to both of the through holes, and a pair of through holes are formed on the outer periphery of both of the cam followers. A C-shaped spring that surrounds these from the outer periphery and elastically biases them radially inward is assembled from the outside, and the two shafts are connected by pressing each of the cam followers against each of the cam surfaces, and A power rudder characterized in that a hydraulic pressure is applied to the outside or inside of each of the cam followers to increase or decrease the pressure depending on the vehicle speed so that the pressing force of each of these cam followers against each of the cam surfaces increases according to the vehicle speed. removal device.