JPH022702Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a variable steering force device for a hydraulic power steering device.

(Prior art) The applicant first used a hydraulic power steering device to lighten the steering wheel operation when stationary or when driving straight ahead at low speed, and as the speed increases, the power assist force is reduced to prevent over-turning the steering wheel. In order to achieve this, a variable steering force device for a hydraulic power steering device as shown in FIGS. 1 and 2 was devised.

1 is the input shaft connected to the handle and housing 2
It is rotatably supported by an upper bearing 3, and has a center hole 1a.
The upper end of the torsion bar 4 inserted into the input shaft 1 is fixed to the input shaft 1, and the serration processing part 4a at the tip of the torsion bar 4, which protrudes from the tip of the input shaft 1, meshes with the rack 5 connected to the steering wheel, and coaxially extends below the input shaft 1. The pinion 7 is fitted and fixed into the upper hole 8a of the pinion shaft 8 of the pinion 7 which is arranged and pivotally connected to the bearing 6 at the lower part of the housing 2. A plurality of through holes 8b are formed in the radial direction of the pinion shaft 8, and a plunger 9 is slidably inserted into each of the through holes 8b. are in contact. Seal rings 10 and 11 are provided above and below the plunger 9 to form a high pressure chamber 12 that receives pressurized oil according to the vehicle speed.
C between 0 and 11 is partially cut and has elasticity.
A mold-shaped retainer 13 is incorporated. The outer diameter of the retainer 13 is the same as or smaller than the outer diameter of the pinion shaft 8.
The gap S between the retainer 1 and the plunger 9 is such that even if the control valve 14 is operated up to the valve stopper and the plunger 9 is moved outward along the longitudinal groove 1a, the retainer 1
There is enough space to prevent contact with 3. The vertical groove 1b of the input shaft 1 is a single-step cut groove with an angle γ as shown in FIG.

When turning to the left, the input shaft 1 rotates to the left, the spherical head 9a of the plunger 9 aligns with the wall of the vertical groove 1b, and rises from the valve center point a' to the contact point c' when the valve is stopped, and the amount of rise is l become.

The reaction force is expressed as Wtan (90° - γ/2), and increases as the reaction force groove angle γ becomes smaller. However, the load W generated by pressure oil has a limit due to the pressure generated by the steering circuit of an actual vehicle, and the expected increase is due to the angle γ,
The smaller γ is, the better, especially since it is necessary in a low pressure region.

Next, the frictional force when the wall surface rises is expressed as F×μμ: coefficient of friction, and the smaller F, that is, the larger γ, the smoother the operation with less frictional resistance.

Therefore, when the groove angle is set to a small γ (for example, 100°), the ODB of the satisfied valve characteristics shown in Fig. 4 is obtained.
curve is obtained, while the rise of plunger 9 is
l, which not only causes interference (Sa) between the retainer 13 and the wall surface but also increases the frictional force between the retainer 13 and the wall surface, impeding smooth operation of the plunger.

On the other hand, in order to eliminate the above drawbacks, when the groove angle is set to a large δ (for example 120°), interference and smoothness can be solved, but the valve characteristics become OCB, and the required input torque at the same pressure P ₁ is the groove angle γ. T ₁ is less than T ₂ at , and its effect is reduced.

That is, the reaction force acting on the plunger 9 depends on the diameter φd of the plunger 9, the magnitude of the applied pressure, and the angle γ, but for the same φd and pressure, the smaller the angle γ, the greater the reaction force. However, the smaller the angle γ, the more spherical the head 9a becomes.
The frictional resistance acting on the valve increases and the valve hysteresis increases. Furthermore, if the plunger 9 slides unsmoothly and the angle γ becomes smaller, the displacement l of the plunger 9 will increase and it will come into contact with the retainer, so the length of the plunger 9 must be shortened, which may cause twisting. There was a drawback that it became.

(Purpose) This invention increases the reaction force for the same pressure acting on the plunger, minimizes the amount of movement to avoid contact with the retainer, and reduces the twisting of the plunger and valve hysteresis due to frictional force, thereby smoothing out the plunger. It is intended to operate.

(Example) FIG. 5 shows an example of the present invention. 1b' is a vertical groove on the outer periphery of the lower part of the input shaft 1 that the spherical head of the plunger 9 comes into contact with.If the inner groove angle up to the intermediate predetermined position b is γ, and the outer groove angle outward from b is δ, then δ >γ.

Next, the effect will be explained. An input from a handle (not shown) causes a relative angular displacement between the input shaft 1 and the pinion shaft 8 of the pinion 7 engaged with the output shaft connected to the steering wheel via the torsion bar 4. Pressure oil from a pump (not shown) supplied to the import 15 is selectively supplied to right-hand and left-hand cylinders (not shown) by the control valve 14, and is returned to the tank from the out port 16. Further, pressure oil corresponding to road resistance and vehicle speed is supplied to the high pressure chamber 12 through a separate circuit (not shown), which pushes the plurality of plungers 9 inward to prevent relative angular displacement between the input shaft 1 and the pinion shaft 8. Work like.

In this case, the present invention, as shown in _FIG .
By setting the inward groove angle up to γ and the outward groove angle up to the valve and stopper beyond which no reaction force is required to be δ, the overall plunger lift amount is reduced to 1,
There is a gap Sb with the retainer 13, and the range of large frictional force can be narrowed, the plunger can operate smoothly, interference with the retainer 13 can be avoided, and the plunger length L can be made long with less twisting.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view of the conventional device, Fig. 2 is a -plane sectional view of Fig. 1, Fig. 3 is an enlarged partial view of the main part of Fig. 2, Fig. 4 is an explanatory diagram of operation, and Fig. 5 is FIG. 3 is a diagram corresponding to FIG. 3 of an embodiment of the present invention. 1...Input shaft, 1a...Vertical groove, γ...Inner groove angle, δ...Outer groove angle, 2...Housing, 4...
Torsion bar, 5... rack, 7... pinion, 8... pinion shaft, 8b... through hole, 9... plunger, 9a... spherical head, 12... high pressure chamber, 14... control valve.

Claims (1)

[Scope of utility model registration request] The tip of the torsion bar, which has one end fixed to the input shaft connected to the steering wheel, is fixed to the pinion shaft engaged with the output shaft connected to the steering wheel, and the hydraulic pressure is controlled by the relative angular displacement of the input shaft and pinion shaft to generate power assist force. A plurality of through holes are provided in the radial direction of the pinion shaft, and a plunger is slidably inserted into each hole, and the tip of the plunger is fitted into a longitudinal groove on the outer circumference of the input shaft, and the plunger is inserted into the hole using hydraulic pressure according to the vehicle speed. In a variable steering force device for a hydraulic power steering device, the input shaft is pressed in the opposite direction to reduce the relative angular displacement between the input shaft and the pinion shaft, thereby reducing the power assist force. A variable steering force device for a hydraulic power steering device that satisfies δ > γ when the inner groove angle of the longitudinal groove is γ and the outer groove angle from a predetermined intermediate position is δ.