JPH0253670A - Power steering device - Google Patents

Abstract

PURPOSE:To increase mechanical strength of a reaction force spring by constituting the reaction force spring, which relatively rotatably connects a stub shaft in a handle side to a side plate in the periphery of the stub shaft, of an almost annular spring member consisting of material of piano wire or the like and protruding its both ends in a radial direction. CONSTITUTION:When a handle 9 is steered, a stub shaft 101 and a side plate 105 are displaced by a relative angle by the elastic deformation of a reaction force spring 103 in accordance with steering torque in that time, and an A valve 3 and a B valve 5, connected to the stub shaft 101 and the side plate 105, are relatively displaced. Thus, a power cylinder is driven by switching an oil path. Here the reaction force spring 103 is constituted, juxtaposing in an axial direction two or more spring members 117 formed by annularly curving a piano wire and by protruding its both ends 121 almost in a radial direction, and the both ends 121 are arranged appearing in notched parts 123, 125 formed in the stub shaft 101 and the side plate 105.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a power steering device used for, for example, a forklift or agricultural machinery.

In particular, it relates to an improved structure of the reaction spring.

(Prior Art) A conventional example will be explained with reference to FIGS. 7 to 12. FIG. 7 is a sectional view showing the configuration of a conventional power steering device, and reference numeral 1 in the figure indicates a housing. An A valve 3 and a B valve 5 are housed within this housing l. Further, a stub shaft 7 is rotatably housed within the housing 1 at the right end in the figure, and rotation from the handle 9 is transmitted to the stub shaft 7.

A side plate 13 is disposed within the housing 1 at a position on the outer periphery of the stub shaft 7. These stub shaft 7 and side plate 13 are
As shown in FIG. 9.10, they are linked via one reaction spring 11. Further, the stub shaft 7 is connected to the A valve 3.
The side plate 13 is configured to rotate together with the B pulp 5.

A drive shaft 15 is attached to the B valve 5, and a trochoid pump 17 is disposed at the tip of the drive shaft 15 within the housing l. Note that the reference numeral 18 in FIG. 1 is a stopper mechanism.

The hydraulic circuit of the power steering system having the above structure is shown in FIG. 8, and numeral 21 in FIG. 0 indicates a power cylinder.

Reference numeral 23 is a tire, and reference numeral 24 is a hydraulic pump.

The configurations of the stub shaft 7, reaction spring 11, and side plate 13 will be explained in more detail with reference to FIGS. 9 to 12. 1 on the inner circumference side of side brake) 13
A pair of square grooves 25.25 are formed at 80° positions, while the stub shaft 7 has the above-mentioned pair of square grooves 25.25.
A square hole 27 is formed so as to coincide with a line connecting the two. Further, as shown in FIG. 11, the reaction spring 11 is a stack of two leaf springs 33 having flat portions 29 and 29 at both ends and a curved portion 31 between these flat portions 29 and 29. It is mounted in the square groove 25 and the square hole 27 with the convex sides of the curved portion 31 in contact with each other.

The operation will be explained based on the above configuration. First, tire 23
Operate the handle 9 against the side load.

This operation of the handle 9 is transmitted to the stub shaft 7,
As a result, the stub shaft 7 and the side plate 13 undergo a relative angular displacement as shown in FIG. (angle θ), that is, only the stub shaft 7 rotates due to the elastic deformation of the reaction spring 11. Note that this relative displacement amount is limited in both directions by the stopper mechanism 19.

The reaction spring 11 bends and deforms as shown in the figure, and this bending deformation generates a steering reaction force.

Further, the A valve 3 and the B valve 5, which are connected to the stub shaft 7 and the side plate 13, respectively, are also relatively displaced by the above-mentioned angle θ, and are switched to either the left or right position in FIG. When the valves are switched in this way, the flow path that leads the hydraulic pump side oil path P to the trochoid pump 17 side is opened, and the flow path that leads the discharged oil of the trochoid pump 17 to the power cylinder 21 is opened. By further rotating the handle 9 in this state, the relative displacement angle θ is maintained in the tap shaft 7 and the side play (13.1), and the handle 9 is rotated in accordance with the amount of rotation of the handle 9.
1 transmitted to the trochoid pump 17, and the trochoid pump 17 counters the load acting on the tire 23 by discharging pressure oil counteracting the load while being hydraulically assisted by the push pressure from the hydraulic pump 24 side. The power cylinder 21 generates hydraulic thrust, and the required steering function is achieved. Furthermore, when the steering input from the handlebar 9 is removed, the first reaction spring 11 returns to its original state due to its elastic restoring force, resulting in a short circuit between the pump side and the tank side, and the passages R and L on the power cylinder 21 side. The state is closed.

(Problems to be Solved by the Present Invention) The conventional configuration described above has the following problems. First, the stress state when the first reaction spring IJ, which had a problem with the aM strength of the reaction spring 11, is deflected, as shown in No. 11ffi (a), the convex side a is the pressure stress,
The recess 1b becomes a tensile stress, and these stress values become large. - When increasing the mechanical strength of the reaction spring 11 inside the shell, it is difficult to rely on the fatigue strength of the leaf spring material that makes up the reaction spring 11, so the only option is to rely on the residual stress that can be secured during the forming process. do not have. However, when the leaf spring 33 is bent, the residual stress generated on the concave side of the leaf spring 33
The tensile stress is the same as the residual stress when the is deflected.

Therefore, it is disadvantageous in terms of durability and strength.In contrast, it is possible to generate residual compressive stress on the concave side, but in order to generate compressive stress on the concave side, it is necessary to increase the bending process. However, there is a problem in that the production cost is high.

Further, even if it were possible to generate residual compressive stress, it would be difficult to stabilize its value, resulting in a problem of variations in durability.

Next, the function of the reaction spring 11 is not only to return the valve to the neutral state when the input signal to the handle 9 is released, but also to provide a steering feel (appropriate weight of the handle 9). In general, cargo handling vehicles such as forklifts are required to have a light steering feel, while agricultural vehicles such as tractors and tractors are required to have a heavy steering feel. by the way,
In the conventional configuration, the steering feeling is adjusted by increasing or decreasing the number of leaf springs 33.
If the width St of the square groove 25 of No. 3 (Fig. 9) and the radius S2 of the square hole 27 of the stub shaft 7 (Fig. 12) are fixed, so-called backlash may occur depending on the number of leaf springs 33 used. There is a risk of malfunction of the valve function. Moreover, if the number of leaf springs 33 to be used is individually set in order to avoid this, there is a problem in terms of cost.

Another problem is that of the processing method.

If the width S2 and position of the square hole 27 of the stub shaft 7 are to be accurately drilled, high machining accuracy is required, and broaching is considered to be possible in the shell, but if you want to increase the precision, it is difficult to use wire, which is expensive. Cutting was required, and there was also a cost problem in this case.

The present invention has been made based on these points, and its purpose is to increase the mechanical strength of the reaction spring and to facilitate the processing of each member at the location where the reaction spring is installed. An object of the present invention is to provide a power steering device that can reduce costs.

(Means for Solving the Problems) In order to achieve the above object, a power steering device according to the present invention includes a housing, a stub shaft installed in the housing to which steering force from a steering wheel is transmitted, and a stub shaft installed in the housing to transmit steering force from a steering wheel. a side plate rotatably disposed on the outer periphery of the stub shaft via a reaction spring; a trochoid pump disposed within the housing for supplying pressure oil to the power cylinder; and a trochoid pump disposed within the housing and disposed on the stub shaft. A power source driven by the relative displacement of a shaft and a side plate, which is equipped with a valve mechanism that adjusts the opening degree of a flow path from a hydraulic pump to a tank, and a flow path from the hydraulic pump to the power steering via the trochoid pump. In the steering device, the reaction spring includes a substantially annular spring provided between the stub shaft and the side plate, and the spring is formed by bending a rod-like elongated member into an annular shape, with both ends protruding in the radial direction and extending in the circumferential direction. A predetermined gap is formed between the stub shaft and the side plate, and when the stub shaft rotates when it is installed between the stub shaft and the side plate with both ends engaged with the notches formed in the stub shaft and side plate. It is characterized in that the stub shaft and the side plate are relatively displaced by a predetermined angle by elastically deforming the two end portions in a direction in which they approach each other.

(Operation of the present invention) When the reaction spring is bent and deformed, compressive stress is generated on the inner circumferential side of the annular portion, and tensile stress is generated on the outer circumferential side. The residual stress distribution of the negative spring is the opposite distribution to that during the above-mentioned bending deformation, so that stress generation can be alleviated.

The steering feel can be adjusted by arranging reaction springs in the axial direction.

Processing of the stub shaft and side plate is also easy, and manufacturing costs can be reduced.

(Embodiment of the present invention) An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. Incidentally, the same parts as in the prior art are denoted by the same reference numerals, and the explanation thereof will be omitted.

Reference numeral 101 in FIG. 1 is a stub shaft, and a side plate 105 is connected to this stub shaft 101 via a reaction spring 103. As shown in FIG. 6, the stub shaft 101 includes members 107 and 101.
9, and these members 107 and 109
The copper brazing is integrated at the position indicated by the two-dot chain line in the figure. A flange 111 is formed at the boundary between the member 107 and the member 108, and a cylindrical portion 113 projects from the flange 111 in the direction of the member 108.

The reaction spring 103 is installed in an annular groove 115 between the cylindrical portion 113 and the member 108.

The reaction force spring 103 is made of piano wire and has a substantially annular spring portion 117.
are connected in the axial direction. As shown in FIG. 4, the spring portion 117 is made by bending an elongated rod-shaped piano wire into an annular shape, with both ends 121 and 121 protruding approximately in the radial direction. have. On the other hand, the cylindrical portion 113 of the stub shaft 101 has a notch as shown in FIG. 23 is formed, and similarly, a notch 125 is formed in the side plate 105 as shown in FIG. The spring portion 117 is installed in the annular groove 115 with its both ends 121 fitted into the notches 123 and 125.

The operation will be explained based on the above configuration.

The basic operation as a power steering device is no different from the conventional one.In the case of this embodiment, the reaction force spring 10 is
The structure of No. 3 is distinctive. That is, when the handle 9 is operated, the operation is transmitted to the stub shirt 101,
As a result, the reaction spring 103 is deformed as shown in FIG.
A relative displacement of each θ occurs between the stub shaft 101 and the side plate 105. This changes the valve mechanism, and then the handle 9 is further operated to drive the trochoid pump 17.

According to this embodiment, the following effects can be achieved.

First, the mechanical strength of the reaction spring 103 will be explained. The stress state when the zero reaction force spring 103 is deflected is shown in Figure 4 (
As shown in b), part a is tensile stress, and part b is compressive stress. The piano wire that makes up the reaction spring 103 has a higher expansion force than conventional leaf spring materials, and the residual stress inherent in the reaction spring 103 after forming is compressive stress in part a and tensile stress in part b. This results in a stress distribution that is opposite to that during bending deformation. As described above, since the material has a high expansion force and the residual stress is opposite to the stress distribution during flexural deformation, the stress during flexural deformation is alleviated. As a result, the reaction force spring 10
The mechanical strength of 3 is improved, 1 and its life can be extended.

Next, the steering reaction force will be explained. As already mentioned, the steering reaction force differs depending on the type of equipment to which it is applied, so it is necessary to adjust this using the reaction force spring 103. In the case of this embodiment, the number of spring parts 117 is adjusted.
23 and the notch 125 of the side plate 105, there is no need to change the dimensions, positions, etc., and costs can be reduced.

Roughly connect the stub shaft 101 to the two members 107.10
9, and these are integrated with copper brazing, etc., so manufacturing costs can be reduced.

(Effects of the present invention) As detailed above, according to the power steering device according to the present invention, by improving the configuration of the reaction spring, it is possible to increase the mechanical strength of the reaction spring and extend its life. At the same time, the steering reaction force can be easily adjusted and manufacturing costs can be reduced, which has great effects.

[Brief explanation of the drawing]

1 to 6 are diagrams showing one embodiment of the present invention, FIG. 1 is a sectional view of a power steering device, and FIG. 2 is a sectional view of a power steering device.
Figure 3 shows the relative displacement between the stub shaft and the side plate, Figure 4 (A) is a plan view of the reaction spring, and Figure 4 (B) shows the reaction spring. Side view, Figure 5 is a side view of the stub shaft, Figure 6 is VI-VI of Figure 5.
Line sectional views and FIGS. 7 to 12 are diagrams showing conventional examples,
Fig. 7 is a sectional view of the power steering device, Fig. 8 is a hydraulic circuit diagram, Fig. 9 is a sectional view taken along line IX-IX in Fig. 7,
Figure 0 is a diagram showing the relative displacement between the stub shaft and the side plate, Figure 11 (A) is a side view of the leaf spring, and Figure 11 (A) is a side view of the leaf spring.
B) is a plan view of the leaf spring, and FIG. 12 is a side view of the stub shaft. l...Housing, 9...Handle, 17...
Trochoid pump, 21... Power cylinder, 24...
- Hydraulic bomb, 101... Stub shaft, 103
...Reaction spring, ...Side plate. ...spring part, ...notch part of fist stub shaft, ...notch part of rhinoceros. Dobrate

Claims (1)

[Claims] a housing; a stub shaft mounted within the housing to which operating force from the handle is transmitted; and a side plate rotatably disposed within the housing and around the outer periphery of the stub shaft via a reaction spring; A trochoid pump that is disposed within the housing and supplies pressure oil to the power cylinder; a flow path that is disposed within the housing and is driven by the relative displacement of the stub shaft and side plate from the hydraulic pump to the tank; and a flow path from the hydraulic pump to the trochoid pump. In a power steering device comprising a valve mechanism that adjusts the opening of a flow path leading to the power steering via a pump, the reaction spring is a substantially annular spring provided between the stub shaft and the side plate, The spring is made by bending an elongated rod-like member into an annular shape, with both ends protruding in the radial direction and a predetermined gap formed in the circumferential direction. It is installed between the stub shaft and the side plate while being engaged with the stub shaft, and when the stub shaft rotates, the stub shaft and side plate are elastically deformed in the direction in which the two ends approach each other, thereby relatively displacing the stub shaft and the side plate by a predetermined angle. A power steering device characterized by: