JPS6231668B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering system, and more particularly to an improved mechanism for creating a relative elastic displacement between the input shaft and output shaft at the connection between the two shafts.

Conventionally, a power steering device is known in which an input and output shaft is connected by a torsion bar, and a non-operating portion can be maintained in a neutral state by the torsion force of the torsion bar. however,
Due to its structure, a torsion bar must be in a neutral state when the torsion force in the left and right directions is zero. Therefore, it is impossible to apply preload between the input and output shafts with a torsion bar, and the structure is The drawbacks were that it was complicated and large.

The present invention has been made in view of these drawbacks, and includes an engaging portion that rotates integrally with the input shaft side and the output shaft side, respectively, and a roughly C-shaped shape that can be engaged with these engaging portions. By arranging a spring that exhibits a shape, the elastic force of this spring holds these engaging parts in a predetermined position, and the stress generated in this spring is made approximately uniform in each part of the circumference. To provide a power steering device capable of applying preload between input and output shafts, and capable of reducing weight and size.

The present invention will be described in detail below with reference to the illustrated embodiment. In FIG. 1, reference numeral 1 denotes an input shaft rotatably supported in a housing 2 via a bearing 3, and is linked to a steering wheel (not shown). Reference numeral 4 denotes an output shaft rotatably supported in the housing 1 through bearings 5 and 6. A pinion formed on the output shaft 4 is engaged with a rack rod 7, and the rack rod 7 is outputted to the housing 2. It is supported slidably in a direction perpendicular to the shaft 4, and both ends thereof are linked to steering wheels (not shown).

The input shaft 1 and the output shaft 4 are arranged on the same axis, and a protrusion formed at the tip of the input shaft 1 is connected to the end of the output shaft 1 via a bush 8 that receives forces in the thrust direction and radial direction. By fitting into the formed hole, the input shaft 1 and the output shaft 4 can rotate relative to each other. The tip of the input shaft 1 and the end of the output shaft 4 respectively form flange portions 9 and 10 facing each other, and as shown in FIG. A plurality of grooves 11 are formed on the end face of the flange portion 10 on the output shaft 4 side, and a plurality of protrusions 12 are formed at predetermined intervals, and the grooves 11 and protrusions 12 are arranged in a required manner in the circumferential direction. By engaging each other with a gap, the input shaft 1 and the output shaft 4
and can be rotated relative to each other by an amount permitted by the gap. Further, the same gears 13 and 14 are fixed to the tip of the input shaft 1 and the end of the output shaft 4, respectively, as shown in FIG. , 16 are press-fitted and fixed. By sandwiching both pins 15 and 16 between the ends of an annular spring 17 disposed on the outer periphery of the flange portions 9 and 10 (see FIG. 2), the spring 17 normally causes both pins 15 and 16 are located on the same axis, so that the protrusion 12 on the output shaft 4 side is usually located in the center of the groove 11 on the input shaft 1 side. Therefore, the input shaft 1 can be rotated relative to the output shaft 4 by the gap between the protrusion 12 and the groove 11 against the spring 17, and the external force applied to both shafts 1 and 4 is When removed, both shafts 1 and 4 are returned to their original state of zero relative rotation angle by the spring 17. As is clear from FIG. 2, the spring 17 has a roughly C-shape with a part of the annular body cut out, and the wall thickness gradually increases from the notch toward the center. The structure is such that the stress is approximately uniform in each part.

In FIG. 2, reference numeral 18 denotes a control valve mechanism having a conventionally well-known configuration, which includes a rod 19 slidably supported on the housing 2, a spool valve 20 attached to this rod, and a control valve mechanism 18 that is connected to the oil pump 21 and ports 22, 23. The function is to supply the pressure oil circulating through the rod 19 and the spool valve 20 to the power cylinder 28 through the port 24 and the pipe line 25 or through the port 26 and the pipe line 27. have. The power cylinder 28 is equipped with a piston 29 fixed to the rack rod 7, and when pressure oil is supplied by displacement of the spool valve 20 constituting the control valve mechanism 18, the power cylinder 28 moves the steering wheels. It aids conversion.

Between the control valve mechanism 18 and the input/output shafts 1, 4, there is a mechanism that converts the relative rotational displacement between the two shafts 1, 4 into a linear displacement and transmits it to the spool valve 20 of the control valve mechanism 18, which is known in the art. A conversion mechanism 30 is provided to perform the same function as the power steering device. In this embodiment, a conventionally well-known Oldham joint is used as the conversion mechanism 30. That is,
In FIG. 1, 31 and 32 are gears of the same shape that mesh with the gears 13 and 14, respectively; 33 is a protrusion with a rectangular cross section protruding from the end surface of one of the gears 31;
34 is a protrusion with a rectangular cross section protruding from the end face of the other gear 32 and perpendicular to the protrusion 33; 35 is a disc interposed between the opposing protrusions 33 and 34; An Oldham joint is constructed by slidably engaging grooves cut perpendicularly to each other with the projections 33 and 34, respectively. The rotating shaft 36 of one gear 32 constituting this Oldham joint is rotatably supported in the housing 2, and the rotating shaft 36 of the other gear 31 is rotatably supported by the housing 2.
By connecting the rod 19 to 7, the conversion mechanism 30 is constructed. In FIGS. 1 and 2, 38 is a seal that prevents lubricating grease from leaking from between the input shaft 1 and housing 2, and 39 and 40 are seals that prevent oil from leaking from the spool valve 20 side. , 41 is a cover.

With the above configuration, when the vehicle is traveling straight, that is, when the input shaft 1 and the output shaft 4 are stationary and the relative rotational displacement between them is zero,
The gears 31 and 32 of the conversion mechanism 30 that mesh with the gears 13 and 14 provided on each shaft 1 and 4 are also stationary, and in this state, the rotation shafts 36 and 37 of both gears 31 and 32 are
are located on the same axis, and the spool valve 20, which is connected to the rotating shaft 37 via the rod 19, is held at a neutral position. Therefore, the pressure oil from the oil pump 21 is not introduced into the power cylinder 28, and the vehicle can continue to travel straight.

When the input shaft 1 is rotated by operating the steering wheel (not shown) from this state, the output shaft 4 is interlocked with the steering wheel via the rack rod 7 and receives road resistance from the steering wheel, so the input shaft 4 is rotated. Shaft 1 has spring 17
The output shaft 4 is rotated relative to the output shaft 4. Then, the gear 31 that is meshed with the gear 13 fixed to the input shaft 1 tries to rotate as the input shaft 1 rotates, but the other gear that rotates integrally with this gear 31 via the Oldham joint 32
Since the gear 31 is still meshed with the gear 14 of the output shaft 4 which is in a stationary state, the gear 31 cannot rotate with the rotation of the input shaft 1, and as a result, the gear 31
is displaced along the sliding direction of the rod 19 without rotating by the driving force of the gear 13.

When the gear 31 is displaced from its normal rest position, the spool valve 20, which is coupled to the gear 31 via the rod 19, is also displaced from its neutral position, switching the hydraulic circuit and shutting down the power cylinder as is well known in the art. Pressure oil is supplied to 28 to assist in turning the steering wheel. When the steering wheel starts turning, the output shaft 4, which is interlocked with the steering wheel through the rack rod 7, starts rotating in the rotation direction of the input shaft 1.

When the input shaft 1 and the output shaft 4 begin to rotate at the same speed, the gear 31, which constitutes the Oldham joint,
32 also begins to rotate in the same direction at the same speed, but since the output shaft 4 is constantly receiving steering resistance from the road surface while the vehicle is turning, the input shaft 4 remains rotationally displaced relative to the input shaft 1. Therefore, the gear 31 and the valve spool 20 interlocked therewith also maintain a displaced state and continue to supply pressure oil to the power cylinder 28. During this time, the driver senses the acting force of the spring 17, which attempts to return the amount of relative rotational displacement between the input and output shafts 1 and 4 to zero, as an operational reaction force. In addition, since this spring 17 returns the relative rotational displacement between the input shaft and the output shaft 4 to zero when the steering wheel is returned to the neutral position, the gear 31 and the valve spool 20 are also reliably returned to the original neutral position. It will be returned. In this way, by holding the pins 15 and 16 in the neutral position by the spring 17, it is possible to apply a preload that could not be obtained with a device using a conventional torsion bar. Since the stress generated in the spring 17 is formed to be substantially uniform in each part, a high spring constant can be obtained even with a small spring, and the entire device can be made smaller and lighter.

Note that if the gear 31 is moved greatly in the axial direction of the rod 19, it will disengage from the gear 13, but generally the amount of displacement of the spool valve 20 that interlocks with the gear 31 may be small, and the gear 3
1, in other words, the relative rotational displacement between the input shaft 1 and the output shaft 4 can be adjusted by adjusting the gap between the groove 11 and the protrusion 12 in accordance with the displacement of the spool valve 20. It will never come out of sync. If it is necessary to displace the spool valve 20 by a large amount, the gear 31
The rod 19 may be connected to the gear 13 by a link or the like so that it can rotate around the gear 13 while remaining in mesh with the gear 13, and the rod 19 may be connected to this link or the like.

Furthermore, in the above embodiment, an Oldham joint is used as the conversion mechanism 30 that converts the relative rotational displacement between the input shaft 1 and the output shaft 4 into linear displacement, but like the Oldham joint, rotation is transmitted between two parallel axes. It goes without saying that mechanisms with other configurations may be used as long as they are capable of doing so. 4 and 5 respectively show the main parts of different conversion mechanisms. In the mechanism shown in FIG. 4, splines are formed on the shafts of the gears 31 and 32, and splines that engage with the splines are formed on the spherical portions 42 at both ends. Both gears 31 and 32 are connected by a rotating shaft 43 having a shape formed therein. Further, in the mechanism shown in FIG. 5, both gears 31 and 32 are connected by a pair of hook universal joints 44, so that changes in the gap between both joints 44 can be absorbed by splines or the like.

As described above, according to the present invention, the input side,
By holding the engaging parts provided on each output side in a predetermined position by using a C-shaped spring,
This has the effect of being able to add preload between the input and output axes.

Moreover, in the present invention, the spring exhibiting a roughly C-shape is formed to have a thicker wall in order from each end toward the center, so that the stress generated in the spring is approximately uniform in each part of the periphery. This has the effect of making the spring lighter and smaller by making maximum use of the spring force depending on the material.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
Figure 3 shows the - line and - line in Figure 1, respectively.
A cross-sectional view taken along the line, FIGS. 4 and 5 are a cross-sectional view and a plan view showing the main parts of the conversion mechanism, respectively, which are different from the above figure. 1: input shaft, 4: output shaft, 18: control valve mechanism,
20: Spool valve, 21: Oil pump, 2
9: Power cylinder, 30: Conversion mechanism.

Claims (1)

[Claims] 1. Controls supply and discharge of pressure oil from the oil pump to the power cylinder by switching the hydraulic circuit according to the input shaft linked to the steering wheel, the output shaft linked to the running wheels, and the relative rotational displacement that occurs between these two shaft connections. In a power steering device equipped with a control valve mechanism, an engaging portion that rotates integrally with each shaft is formed at a connecting portion between the input shaft and the output shaft, and
These engaging portions are provided with springs having a roughly C-shape that engage with the engaging portions to hold the input shaft and the output shaft in a neutral position, and the springs are arranged sequentially from each end toward the center. A power steering device characterized in that the spring is formed thick so that the stress generated in the spring is set and maintained substantially uniformly at various parts of the circumference.