JPH11115772A - Shaft with gear and steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce weight and be hardly broken by constituting the shaft with gear of a cylindrical shaft main body and a gear fitted to the outer circumference of it, and by expanding the shaft main body toward the recessed parts of a gear inner hole to integrate the shaft main body with the gear. SOLUTION: A plurality of recessed parts 5b constituted of spline grooves in parall along the inner circumference direction are formed on the inner circumference of a gear 5. By expanding a shaft main body 30 from the inner circumferential side of the gear 5 to the outer circumferential side, a projecting part 30b entering the respective recessed parts 5b of the gear 5 are formed, and the shaft main body 30 and the gear 5 are integrated. By this constitution, the shaft main body 30 is cylindrical and formed into a hollow part 30c in the inner part, and the weight can be reduced than that of the inner solid material. Further the shaft main body 30 is hardly broken compared with the solid material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a geared shaft having a gear on the outer periphery, and a steering device provided with the geared shaft.

[0002]

2. Description of the Related Art A ball screw type steering apparatus includes an input shaft which is rotated by steering, a rack which is moved by the rotation of the input shaft, and a geared shaft which meshes with the rack. The vehicle is steered by transmitting it to the steering wheel. The geared shaft includes a shaft body and a sector gear disposed on an outer periphery of the shaft body. Conventionally, the gear and the shaft main body have been integrally formed from a solid material by hot forging, and then machined.

[0003]

Since the geared shaft in the conventional ball screw type steering apparatus is a solid material, it is heavy and is unsuitable as a vehicle component which requires a reduction in weight for energy saving. It was something.

[0004] If the shaft with gears is significantly reduced in weight and an excessive load acts on the gears to break the shaft body, the vehicle cannot be steered.

[0005] Since the shaft length of the shaft main body differs according to the type of vehicle, there is a problem that the number of types of shafts with gears increases and the production efficiency is low.

When the gear and the shaft main body are hot forged, the number of machining steps for the forged gear increases. Therefore, cold forging is desired. However, when the gear and the shaft main body are integrally formed from a solid material, since the shaft main body needs to be drafted from the mold, cold forging becomes more difficult as the shaft main body becomes longer.

An object of the present invention is to provide a geared shaft and a steering device that can solve the above-mentioned problems.

[0008]

SUMMARY OF THE INVENTION A geared shaft according to the present invention includes a cylindrical shaft body, and a gear fitted to the outer periphery of the shaft body, the gear having a concave portion on the inner periphery. The shaft main body has a convex portion that has entered the concave portion by being spread from the inner peripheral side toward the outer peripheral side, and the shaft main body and the gear are integrated by the convex portion entering the concave portion. It is characterized by the following. According to this configuration, since the shaft main body is cylindrical and the inside is hollow, the weight can be reduced as compared with the solid material. Since the shaft body is cylindrical, it is less likely to break than a solid material.
Because the shaft body and gear are molded from separate members,
When an excessive load acts on the gear, relative displacement occurs, thereby preventing breakage of the shaft main body due to the excessive load. Since the shaft body and the gear are formed from separate members, the gear can be cold forged, and the number of machining steps after forging can be reduced as compared with the case of hot forging. Since the same type of gear can be integrated with a plurality of types of shaft bodies having different shaft lengths, production efficiency can be improved.

A steering device according to the present invention includes an input shaft that is rotated by steering, a rack that is moved by the rotation of the input shaft, and the geared shaft of the present invention that meshes with the rack, and that rotates the geared shaft. It is characterized in that the vehicle is steered by transmitting it to the steering wheel. According to this configuration, by using the geared shaft having the configuration of the present invention,
Energy saving can be achieved by reducing the weight of the vehicle. Further, even if the weight is reduced, breakage of the geared shaft can be prevented, so that the vehicle can be prevented from being unable to be steered.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

A ball screw type power steering apparatus A shown in FIGS. 1 and 2 has an input shaft 1 and a housing 2.
And the ball screw 13 and the ball screw 1
Ball nut 3 fitted to ball 3 via ball 14
And a rack 4 formed on the ball nut 3, and an output shaft 6 with a sector gear 5 meshing with the rack 4.
And a pitman arm 17 attached to the lower end of the output shaft 6 via a tapered serration 18. The pitman arm 17 is fixed by a nut (not shown) screwed into a screw portion 19 at the lower end of the output shaft 6.

The housing 2 is made of cast iron, and the first space 2a into which the ball nut 3 is inserted so as to be movable in the axial direction.
And a second space 2b whose output shaft 6 is supported via bearings 7 and 8 so as to be rotatable about the axis and movable in the axial direction. The first space is partitioned by a piston 3a integral with the ball nut 3 to form a pair of oil chambers 11, 12. The input shaft 1 and the ball screw 13 are connected via a torsion bar 19, the input shaft 1 is connected to a steering wheel (not shown), and a rotary valve 16 is provided on the outer periphery of the input shaft 1. Its input shaft 1
Is rotated by steering, the rotation is transmitted from the torsion bar 19 to the ball screw 13, the ball nut 3 and the rack 4 move in the axial direction, and the movement of the rack 4 is transmitted via the gear 5 to output. The shaft 6 rotates. The swing of the pitman arm 17 due to the rotation of the output shaft 6 is transmitted to the steered wheels via a link (not shown) to steer the vehicle.

A known rotary valve 16 can be used, and pressure oil sent from a pump (not shown) is used.
Oil is supplied to one of the oil chambers 11 and 12 according to the amount of elastic torsion of the torsion bar 19 according to the steering direction and the steering torque, and oil is returned from the other of the oil chambers 11 and 12 to a tank (not shown). Thereby, the hydraulic pressure for moving the ball nut 3 in the axial direction acts, and the steering assist force is given.

Outside one end of the output shaft 6,
The screw shaft 21 is screwed to the cover fitted to the housing 2. One end of the screw shaft 21 is connected to one end of the output shaft 6 so as to be relatively rotatable about the axis and to restrict relative movement in the axial direction. That is, one end of the screw shaft 21 is rotatably inserted into a rectangular cylindrical receiving member 40 which is screwed to the outer periphery of the small diameter portion 6a at one end of the output shaft 6, and the screw shaft 21 is screwed.
The flange 21a formed at one end of the
0 so that the axial relative movement is restricted. The rotation of the screw shaft 21 causes the output shaft 6 to rotate.
Is moved axially with respect to the housing 2 so that the gear 5
And the rack 4 is adjusted.

The output shaft 6 includes a cylindrical shaft body 30 and the gear 5 fitted on the outer periphery of the shaft body 30. On the inner periphery of the gear 5, a plurality of recesses 5b formed by spline grooves arranged in parallel in the circumferential direction are formed. The shaft main body 30 has a convex portion 30b which is pushed into the concave portion 5b of the gear 5 by being pushed out from the inner peripheral side to the outer peripheral side, and the shaft portion 30b is formed by entering each concave portion 5b into the concave portion 5b. Body 30
And the gear 5 are integrated.

The gear 5 is formed from a columnar gear material 5 'such as solid SCM420 and S45CB1 shown in FIGS. 3 (1) and 3 (2). The gear blank 5 'is formed into a first intermediate formed body having a shape shown in FIGS. 3 (3) and (4) by cold die forging in the first stage. At this stage, portions 5a 'and 5b' corresponding to the teeth 5a and the inner peripheral hole 5b of the gear 5 are substantially formed. Next, the first intermediate formed body is formed by the second stage cold die forging into a second intermediate formed body having a shape shown in (5) and (6) of FIG.
It is molded into an intermediate molded body. At this stage, the teeth 5a
5a 'is formed close to the final shape, leaving only the finishing process, and the other portions are formed into the final shape, and the recess 5b is formed at this stage.

The shaft main body 30 is formed from a hollow cylindrical shaft material 30 'such as a hollow SCM 420 or S45CB1 shown in FIG. The shaft material 3
0 ′ is formed in a first intermediate formed body having a shape shown in FIG. 4 (2) by a first-stage cold die forging in which the punch P is pushed into the inside of the forming die. That is, one end 6a 'of the first intermediate molded body has a shape corresponding to the small diameter portion 6a, and the other end has an axial dimension and an inner peripheral diameter of the material 3.
0 ', and the thickness of the portion between both ends is made larger than the thickness of the other end. The first intermediate molded body of the shaft body 30 is placed in a molding die after the second intermediate molded body of the gear 5 is fitted around the outer periphery between both ends, and the punch P is pushed into the second intermediate molded body. By cold die forging,
The portion between both ends is pushed and spread from the inner peripheral side to the outer peripheral side by the punch P via the inner peripheral step 30c 'between the both end part and the other end side, and the shape shown in FIG. It is molded into a second intermediate molded body. That is, the convex portion 30b that enters the concave portion 5b is formed.

Thereafter, as shown in FIG. 4 (4),
The other end of the second intermediate formed body is narrowed by rotor lease aging, the tapered serration 18 and the threaded portion 19 are rolled around the narrowed portion, and the screw shaft 21 is inserted into one end thereof. The member 40 is swaged. Further, the outer circumference between the portion corresponding to the small diameter portion 6a and the portion of the gear 5 where the second intermediate molded body is fitted, and the portion of the gear 5 where the second intermediate molded body is fitted are tapered serrations. 18 is polished after quenching. The output shaft 6 with the gear 5 is completed by finishing and hardening a portion 5a 'corresponding to the tooth portion 5a based on the polished portion.

According to the above configuration, the shaft body 30
Is cylindrical and has a hollow portion 30c inside, so that the weight can be reduced as compared with the solid material, and energy saving can be achieved by reducing the weight of the vehicle. Further, since the shaft main body 30 is harder to break than the solid material, and since the shaft main body 30 and the gear 5 are formed from separate members, when an excessive load acts on the gear 5, relative displacement occurs, and The breakage of the shaft main body 30 due to the excessive load can be prevented. By preventing the breakage, it is possible to prevent the vehicle from being unable to be steered. Further, since the shaft body 30 and the gear 5 are formed from separate members, cold forging can be performed, and the number of machining steps after forging can be reduced as compared with the case of hot forging. . In addition, since the same type of gear can be integrated with a plurality of types of shaft bodies having different shaft lengths, production efficiency can be improved.

The present invention is not limited to the above embodiment. For example, the present invention may be applied to a geared shaft of a manual steering device, or may be applied to a geared shaft used other than the steering device.

[0021]

According to the geared shaft of the present invention, the weight is reduced, the breakage is prevented even when the weight is reduced, the production efficiency is improved, and the processing cost is reduced. By using the geared shaft, energy saving and improvement in safety can be achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a ball screw type power steering device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the ball screw type power steering device according to the embodiment of the present invention.

FIG. 3 is a plan view of a gear according to an embodiment of the present invention, (1) is a plan view of a raw material, (2) is a side view of the raw material, (3) is a plan view of a first intermediate molded body, and (4) is a first intermediate form. Side view of the molded body, (5) is a plan view of the second intermediate molded body, (6) is a side view of the second intermediate molded body

FIGS. 4A and 4B are cross-sectional views of a raw material, (2) a cross-sectional view of a first intermediate molded body, (3) a cross-sectional view of a second intermediate molded body, and (4). ) Is a sectional view

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input shaft 4 Rack 5 Gear 5b Concave part 6 Output shaft 30 Shaft main body 30b Convex part

Claims (2)

[Claims] A shaft fitted to an outer periphery of the shaft body, the gear having a concave portion on an inner periphery, and the shaft body being moved from an inner peripheral side to an outer peripheral side. A shaft with a gear, comprising: a convex portion which is pushed into the concave portion to enter the concave portion; and the convex portion enters the concave portion, whereby the shaft body and the gear are integrated. 2. An input shaft that is rotated by steering, a rack that is moved by rotation of the input shaft, and a geared shaft of claim 1 that meshes with the rack, and the rotation of the geared shaft is applied to a steering wheel. A steering device that steers a vehicle by transmitting it.