JPH0285063A - Power steering device - Google Patents

Abstract

PURPOSE:To increase the joint strength between a ball screw and a torsion bar by serration-joining the both and caulking the opened port part of a fitting hole of the ball screw into which the edge part of the torsion bar is fitted. CONSTITUTION:A torsion bar 27 whose one edge is fixed onto an input shaft 17 and the other edge is fixed onto a ball screw 21 is inserted into a through hole 26 formed on the input shaft 17 connected with a steering wheel, and the input shaft 17 and the ball screw 21 are elastically connected by the torsion bar 27, and a serration part 30 is formed at the other edge of the torsion bar 27, and a taken-away part 31 having a small diameter is formed in the intermediate part. Fixing is performed by press-fitting the serration part 30 into a serration hole part 23 which is formed at the large diameter part 23 of the ball screw 21 and has the equal tooth shape to that of the serration part 30. Further, a projection part 36 formed on the edge surface 35 of the serration hole part 32 is adjusted to the outer periphery of the torsion bar 27 and caulked.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a power steering device.

<Prior Art> Conventionally, in a power steering device, as shown in FIG. is inserted and elastically connected to the ball screw 5. That is, one end of the torsion bar 4 is connected to the input shaft 2 through a pin 6, and the other end of the torsion bar 4 is connected to a ball screw 5 through a pin 7. Alternatively, there is one in which the torsion bar 4 and the ball screw 5 are fixed by electron beam welding.

<Problems to be Solved by the Invention> As described above, the ball screw 5 and the torsion bar 4 are connected by bottle connection or electron beam welding, but when performing the bottle connection, it takes a lot of man-hours to insert the bottle, and the electron beam This joint is problematic because it requires the use of expensive equipment to weld.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned problems. The ends of the torsion bars are brought into contact with each other, and in this state caulking is performed at the opening of the fitting hole, and serrations are formed on the inner periphery of the fitting hole, and a recess is formed in the middle of the outer periphery of the torsion bar. The ball screw and the torsion bar are connected to each other by forming serrations.

Effect> With the above configuration, when the handle is rotated, the input shaft is rotated, and the rotation of the input shaft is transmitted to the torsion bar. The ball screw fixed to the other end of the torsion bar is difficult to rotate due to the ground resistance of the tire, so the torsion bar is twisted. Then, a servo valve consisting of an outer sleeve fixed to the ball screw and an inner sleeve formed on the input shaft is activated. At this time, torsional torque and lateral stress are applied to the joints at both ends of the torsion bar. Eventually, the ball screw begins to rotate, and the piston screwed into the ball screw reciprocates while being assisted by pressure oil from the servo valve.The reciprocating motion rotates the cross shaft that engages with the piston, and the front wheels are steered.

<Example> Hereinafter, an example of the present invention will be described based on FIG. 1. 10
is a servo housing, and this servo housing 10
A cylindrical cylinder housing 11 is coupled to the cylindrical cylinder housing 11 .

A small diameter hole 12 and a large diameter hole 13 are sequentially formed in the servo housing 10.
A stepped portion 14 extending in the radial direction is formed between them.

An input shaft 17 connected to the handle via a bearing 15 and a packing 16 is rotatably supported in the small diameter hole 12, and an outer sleeve 18 is rotatably fitted between the input shaft 17 and the small diameter hole 12. There is.

Further, an inner sleeve 19 is integrally formed on the input shaft 17 at a position corresponding to the outer sleeve 18, and the outer sleeve 18 and the inner sleeve 19 constitute a well-known servo valve 20. Note that 61°62.63.64 is a flow path formed in the servo valve 20 for passing pressure oil,
65 is a discharge port formed in the input shaft F.

Reference numeral 21 denotes a ball screw that rotates integrally with the outer sleeve via a pin 22 on the first day of the outer sleeve, and this ball screw 21 has a large diameter portion 23 that is fitted and supported in the large diameter hole 13 . A support hole 24 is formed in the large diameter portion 23, and one end of the human power shaft 17 is rotatably supported in the support hole 24 via a bearing 25.

A through hole 26 is formed in the input shaft 17, and this through hole 26
A torsion bar 27 having one end fixed to the input shaft 17 and the other end fixed to the ball screw 21 is inserted, and the input shaft 17 and the ball screw 21 are elastically connected by this torsion bar 27.

That is, an insertion hole 28 is formed at one end of the torsion bar 27, and a pin 29 is driven into the insertion hole 28, thereby fixing the torsion bar 27 to the input shaft 17.

Furthermore, a serration portion 30 is provided at the other end of the torsion bar 27.
is formed, and a hollow part 31 having a small diameter and in which no serrations are formed is provided in the middle part of the serration part 30. The serration hole 32 is provided in the large diameter portion 23 of the ball screw 21 and has a tooth profile having the same shape as the tooth profile of the serration part 30.
is fixed by press-fitting and rotated in the same direction as the ball screw 21.

Further, the torsion bar 27 is press-fitted until the tip end surface 34 of the serration section 30 comes into contact with the bottom surface 33 of the serration hole section 32, and the convex section 36 formed on the end surface 35 of the serration hole section 32 is inserted into the outer periphery of the torsion bar 27. By caulking the ball screw 21 and the torsion bar 27, the joint between the ball screw 21 and the torsion bar 27 is strengthened against transverse stress.

A cylinder chamber 50 is formed inside the cylinder housing 11, and a piston 51 is fitted into this cylinder chamber 5o so as to be slidable in the axial direction.The cylinder chamber 50 is divided into a right chamber 5G and a left chamber 57 by this piston 5I. It is being At the center of the piston 51, it is screwed into the ball screw 21 via a ball 52, and rack teeth 53 are formed on the outer periphery. A cross shaft 54 is rotatably supported in the cylinder housing 11 around an axis perpendicular to the rotational axis of the ball screw 21, and the cross shaft 54 is formed with binion teeth 55 that mesh with the rack teeth 53. The right chamber 56 is communicated with the flow path 64 of the servo valve 20 via a flow path 68 formed in the cylinder housing 11 and a flow path 69 formed in the servo housing 10, and the left chamber 57 is formed in the cylinder housing 11. The servo valve 20 is connected to the flow path 63 of the servo valve 20 through a flow path 70 formed in the servo housing 10 and a flow path 71 formed in the servo housing 10 .

The servo housing 10 also has a supply port 66 for supplying pressure oil to the servo valve 20 and a discharge port 6 for discharging the pressure oil.
7 is formed.

The operation will be explained based on the above configuration. When the handle is in the neutral position, pressure oil flows from the supply port 66 to the flow path 62.
The pressure oil that has entered the flow path 63 and the flow path 64 is guided to the left ventricle 57 via the flow paths 71 and 70, and the pressure oil that has entered the flow path 64 enters the flow paths 69 and 6B. right ventricle 56 via
guided by.

Since there is no relative rotation between the outer sleeve 18 and the inner sleeve 19, the same pressure oil is distributed in the flow path 63 and the flow path 64, and no pressure difference occurs between the left chamber 57 and the right chamber 56. , the piston 51 maintains the neutral position.

For example, when the handle is turned to the right, the input shaft 17 rotates to the right, but because the ball screw 21 is loaded with the ground resistance of the tires, it cannot rotate immediately and stops, so the input shaft 17 The torsion bar 27 connected between the ball screw 21 and the ball screw 21 is twisted. Further, due to the rotation of the human power shaft 17, the inner sleeve 19 rotates relative to the outer sleeve 18, so that the flow path 62 communicates only with the flow path 63. That is, the pressure oil enters the flow path 63 from the supply port 66 through the flow path 62, passes through the flow paths 71 and 70, and enters the left ventricle 5.
7, and the fluid in the right ventricle 56 flows through channels 68, 69, 6.
4.61, enters the discharge port 65 and flows out from the discharge boat 67. As a result, a pressure difference is generated between the left chamber 57 and the right chamber 56, and the piston 51 generates an operating force to the right in FIG. Rotate clockwise. When the input shaft 17 stops rotating after turning the handle, the twisted torsion bar 27 returns to its neutral state, and the pressure difference between the left chamber 57 and the right chamber 56 disappears. When the handle is turned to the left, a similar operation is performed to assist the rotational force of the input shaft 17 and rotate the cross shaft 54 counterclockwise.

In this way, each time the handle is turned left and right, torsional torque is applied to the torsion bar 27, so the ball screw 21
In order to withstand large rotational stress at the fixed part, the required tolerance range of the press-fitting load of the serration part is strictly determined. As described above, by forming the hollow part 31 in the middle part of the serration part 30 of the torsion bar 27, as shown in FIG. Even if the press-fit interference is the same, the press-fit load can be reduced. Also, from this fact, if the press-fitting load is the same, the press-fitting interference increases, and as shown in FIG. 3, the slope α of the press-fitting load with respect to the press-fitting interference becomes small. Therefore, the control width X of the press-fit interference, which corresponds to the control width Y of the press-fit load to ensure the required quality, becomes larger. That is, the tolerance of the press-fitting interference can be increased, and the matching work when assembling the torsion bar 27 and the ball screw 21 becomes easier. Moreover, since the hollow part 31 is formed in the intermediate part, the same precision in tilting the torsion bar 27 due to press fitting as in the case where the hollow part 31 is not provided can be ensured.

In addition, in order to prevent lateral stress at the serration joint between the ball screw 21 and the torsion bar 27, the torsion bar 27 is press-fitted until the end face 34 of the serration part 30 comes into contact with the bottom part 33, and then the serration hole 32 By caulking the convex portion 36 formed on the end surface 35 of the torsion bar 27 to match the outer periphery of the torsion bar 27, as shown in FIG. can now be made larger than before.

<Effects of the Invention> As described above, in the present invention, the serration joint is more cost-effective than the conventional bottle joint or the joint by electron beam welding, and the hollow part is formed in the serration. The control range of the press-fit interference corresponding to the control range of the press-fit load to ensure the required quality is increased, the tolerance of the press-fit interference can be increased, and the matching work during assembly is easier. Become.

In addition, by press-fitting the torsion bar until the tip touches the bottom of the serration hole, and in that state, caulking the convex part formed on the end surface of the serration hole to match the outer circumference of the torsion bar, became more resistant to external forces.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall view of the present invention, FIG. 2 is a diagram showing the relationship between press-fitting load and press-fitting depth in the serrations, and FIG. 3 is a diagram showing the relationship between the press-fitting load and the press-fitting depth in the serrations. Figure 4 is a diagram showing the relationship between the maximum value of lateral external force and the press-fitting method,
FIG. 5 is an overall diagram of the conventional method. 17...Human power shaft, 21...Ball screw, 27...
・Torsion bar, 30... ・Serration part,
31... Recessed portion, 33... Bottom portion, 34... Tip surface, 36... Convex portion 9

Claims (1)

[Claims] (1) A cylindrical input shaft that rotates when the handle is operated;
A similarly cylindrical ball screw is provided coaxially with this input shaft, and one end is fixed to the inner periphery of this ball screw and the other end is fixed to the inner periphery of the input shaft to connect the input shaft and the ball screw. In a power steering device including a torsion bar that is elastically connected, an end of the torsion bar is attached to the bottom of a fitting hole of the ball screw on the side where the torsion bar is fixed to the inner periphery of the ball screw. and in this state, caulking is performed at the opening of the fitting hole, and serrations are formed on the inner periphery of the fitting hole, and a hollow part is formed in the middle part of the outer periphery of the torsion bar. A power steering device characterized in that serrations are formed to perform serration connection between the ball screw and the torsion bar.