JPH0223494Y2 - - 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 present applicant uses a hydraulic power steering device to lighten the steering operation when stationary or when driving straight ahead at low speed, and reduces the power assist force as the speed increases to prevent excessive steering. In order to eliminate this problem, we devised a variable steering force device for a hydraulic power steering device as shown in FIGS. 1 and 2. 1 is an input shaft connected to the handle, which is rotatably supported by a bearing 3 on the upper part of the housing 2;
The upper end of the torsion bar 4 inserted into the center hole 1a is fixed to the input shaft 1, and a serration processed portion 4a at the tip of the torsion bar 4 protrudes from the tip of the input shaft 1.
meshes with the rack 5, which is an output shaft connected to the steering wheel, and is disposed coaxially below the input shaft 1, and is connected to the housing 2.
A pinion shaft 8 of a pinion 7 pivotally mounted on a lower bearing 6 is press-fitted into an upper hole 8a. A plurality of through holes 8b are formed in the radial direction of the pinion shaft 8,
A plunger 9 is slidably inserted into each plunger 9, and a spherical head 9a at the tip of the plunger 9 is in contact with a vertical groove 1b formed on the outer periphery of the tip of the input shaft 1. Seal rings 10 and 11 are provided above and below the plunger 9 to form a high pressure chamber 12 that receives pressurized oil depending on the vehicle speed. , are positioned and held by fixing pins 17. Therefore, the rotational positions of the pinion shaft 8 and the input shaft 1 are determined by the control valve 14, and the plunger 9 fitted in the through hole 8b formed in the radial direction of the pinion shaft 8 is defined as shown in FIG. Such discrepancies often occur. This deviation becomes a reaction force deviation δ as shown in FIG. At this time, since there is almost no reaction force from the torsion bar 4, even if a slight pressure is applied to the plunger 9, it acts until it hits both walls of the vertical groove 1b.

That is, the input shaft 1 is relatively displaced so that the deviation δ becomes zero. Therefore, as shown in FIG.
4.There was a drawback that the vehicle became unbalanced at the neutral position, creating a pressure difference of P between the left and right cylinders, causing the vehicle to drive diagonally or causing the steering wheel to rotate.

(Purpose) The purpose of the present invention is to automatically correct the pressure difference between the left and right cylinders when the control valve is in the neutral position to prevent the vehicle from running diagonally or from rotating the steering wheel.

(Example) FIG. 6 shows an embodiment of the present invention.

1. As shown in Figure 6, the plunger's shaft and ball are misaligned.

2 Alignment action Now, when assembled as shown in Figure 6, and at low speed reduction where no hydraulic reaction force is applied, the plunger is only lightly touching the V-groove of the input because P ₁ ≒ P ₂ . In this case, there is no alignment effect.

When the vehicle speed increases and hydraulic reaction pressure is applied to increase the central stiffness of the steering wheel (towards a straight-ahead state), the plunger is hydraulically applied from top to bottom in Figure 6 (F).

In this case, when the X and Y axes are the same and there is an error only in the Z axis (the Z axis is directly connected to the valve center and changes depending on the valve center), press down along slope a of the input and move the input axis to the left. Rotate (move so that sphere X matches Z). That is, the input shaft is twisted to the left and the valve balance is lost (prior art).

On the other hand, if the X and Y axes are shifted as in the present invention, a rotational force will be applied to the plunger due to the eccentricity between the Y axis and the contact point of the ball in response to the pressure of the plunger. Then, it moves until it hits another slope b. As a result, the valve neutral position and the center of the spherical head of the reaction force plunger coincide, so that the pressure difference between the left and right cylinders at the valve neutral position can be automatically corrected.

Note that depending on the direction of rotation of the input shaft 1 as the direction of the reaction force, the range of eccentricity ±δ may be felt as a torque dead zone, but since δ is small, it is within a range that does not cause any actual harm.

(Effect) According to this invention, the spherical head at the tip of the plunger is slightly eccentric to the axis of the plunger, so it settles in the vertical groove of the input shaft, automatically correcting the pressure difference between the left and right cylinders when the control valve is in the neutral position. This can prevent the car from running diagonally or from rotating the steering wheel.

[Brief explanation of the drawing]

Figure 1 is a front sectional view of the conventional device, Figure 2 is a planar sectional view of Figure 1, Figure 3 is an enlarged partial view of the main part of Figure 2, and Figure 4 is the input torque and torsion bar of the conventional device. The torsion angle graph, Figure 5 is a graph of pressure and input torque of the left and right cylinders of the conventional device, and Figure 6 is a graph of the pressure and input torque of the left and right cylinders of the conventional device.
The figure is an explanatory diagram of the operation of one embodiment of the present invention. 1...Input shaft, 1a...Vertical groove, 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, one end of which is 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 relative angular displacement between the input shaft and pinion shaft controls hydraulic pressure to provide power assist. In order to control the force, a plurality of through holes are provided in the radial direction of the pinion shaft, and plungers are slidably inserted into each hole, and the tip of the plunger is fitted into a vertical groove on the outer circumference of the input shaft, and the plunger is activated by hydraulic pressure according to the vehicle speed. In a variable steering force device for a hydraulic power steering device, the spherical head at the tip of the plunger is pressed inward to reduce the relative angular displacement between the input shaft and pinion shaft, thereby reducing the power assist force. A variable steering force device for a hydraulic power steering device with a slightly eccentric axis.