JPS6331325B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a rack and pinion mechanism rack (hereinafter abbreviated as variable rack) of variable ratio type in which the gear ratio changes depending on the meshing position of the rack and pinion. The present invention relates to a device for processing.

This type of rack-and-pinion mechanism can be suitably used for vehicle steering devices, etc., and the racks used in this mechanism have straight teeth and can be processed with high productivity by milling or broaching. can. However, with a variable rack with a helix angle, not only the tooth lead direction differs for each tooth, but also the tooth thickness, module,
Machining is extremely difficult because the pitch etc. differ in each location, and no equipment is known yet that can process this with high productivity.

Against this background, the present invention has been made with the object of providing an apparatus capable of manufacturing variable racks with high productivity by cutting. Therefore, the variable rack processing apparatus according to the present invention comprises: (1) a cutting tool having a shape corresponding to a pinion capable of meshing with a desired rack and having a cutting edge formed at the tip of each tooth trace; ) While holding the cutting tool rotatably,
a reciprocating member that is reciprocated in the axial direction of the cutting tool by a drive mechanism; (4) a master rack that is intermittently fed in the longitudinal direction between each reciprocating movement of the reciprocating member by an intermittent feed mechanism in a state in which the workpiece is engaged with the tool; and material holding means for holding the material in the mating position and moving together with the master rack.

In the processing device according to the present invention, the reciprocating member is simply reciprocated, and the master rack and material holding means are intermittently fed by minute distances between the reciprocating movements, so that cutting is performed by the guidance of the master rack. Since the tool is provided with the necessary movement to create a predetermined variable rack, most of the processing equipment can be relatively simple, similar to a conventional milling machine, and can be manufactured at low cost. It is also possible to construct the apparatus of the present invention by modifying an existing milling machine.

In particular, with regard to variable racks having a helix angle, the only conventional machining methods that can be used to process them are die-scattering machining, electric discharge machining, etc., but with the device of the present invention, these methods can be processed. It is no exaggeration to say that the completion of the present invention made it possible for the first time to mass produce variable racks with a helix angle. Furthermore, since the cutting tool can be easily manufactured by ordinary hobbing, and the variable rack is processed by the generation method, a product with high meshing accuracy can be obtained.

It should be noted that, as is clear from the above description, the present invention was made for the direct purpose of enabling highly productive processing of variable racks with helix angles; Of course, it is also possible to process variable racks, and in this case, changing the gear ratio can be easily handled, and since expensive milling cutters, broach cutters, etc. are not required, small-scale production is also possible. The effect of this can be obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIGS. 1 and 2, 1 is the base of the main body of the processing device, and 2 is the head. The head 2 is fixed to a column (not shown) erected on the base 1 and is positioned above the base 1.

A ram 3, which is a reciprocating member, is fitted to the head 2 in a slidable but non-rotatable manner. The ram 3 is reciprocated up and down by a drive mechanism (not shown) equipped with a mechanism such as a crank mechanism or a cam mechanism that converts rotational motion into reciprocating motion. A tool holder 6 is rotatably attached to the ram 3 via ball bearings 4 and 5, and a cutting tool 7 is mounted on the tool holder 6.
is fixed. The cutting tool 7 has a shape corresponding to a pinion that can mesh with the variable rack to be machined (not only the pinion actually used in combination with the variable rack, but also a pinion with a larger diameter to increase rigidity). However, the end surface 8 of each tooth having a helix angle is formed so as to be approximately perpendicular to the respective tooth trace, and the edge thereof is used as a cutting edge.

On the other hand, a movable table 11 is disposed on the base 1 so as to be slidable in the horizontal direction. The movable table 11 is fed in minute amounts by an intermittent feed mechanism that operates in conjunction with the drive mechanism. Since the intermittent feed mechanism is a normal one, illustrations and detailed explanations will be omitted, but it operates when the cutting tool 7 is raised to near the top dead center and moves the movable table 11 by a preset minute distance. let A partially cut-out circular through hole 12 is horizontally formed in the movable table 11, and a master rack 13 is inserted through the through hole 12 with a portion exposed, and is fixed with a bolt 14. . The exposed portion of the master rack 13 is provided with teeth formed to vary the gear ratio, similar to the variable rack to be machined. These teeth are manufactured by die-sculpting machining, electrical discharge machining, or the like. Master rack 13 and cutting tool 7
are in mesh with each other, so that the cutting tool 7 is given rotational motion by the master rack 13 when reciprocated as described above.

The workpiece W to be processed is mounted below and parallel to the master rack 13. That is, a similar through hole 15 is formed in the movable table 11 below the through hole 12, and the material W is inserted into the through hole 1.
5 and is fixed with a bolt 16, and in this embodiment, the moving table 11 and the bolt 16 constitute a material holding means.

Furthermore, as shown by the two-dot chain line in Fig. 2, the base 1
A hydraulic cylinder 18 is fixed to an erected stand 17, and a pusher head 21 is attached to the tip of the piston rod 19, whereby the cutting tool 7
By pressing the master rack 13 against the master rack 13 with a constant force, play in the direction perpendicular to the axis of the cutting tool 7 can be eliminated and stable machining can be performed.

In the processing apparatus configured as described above, the moving table 11 is moved to the farthest left in FIG. It will be done. Thereafter, the drive device is activated to cause the ram 3 to reciprocate up and down. Along with this, the cutting tool 7 is also moved back and forth, but at the same time, the master rack 13 also imparts rotational movement. Each time the cutting tool 7 makes one reciprocation and reaches near the top dead center, the movable table 11 is moved to the right by a certain minute distance by the intermittent feed mechanism.

Eventually, the cutting tool 7 comes into contact with the material W to start cutting, and teeth similar to the teeth of the master rack 13 are created on the material W. The amount of intermittent movement of the moving table 11 is the same throughout the entire machining length, but
Since the rotation angle of the cutting tool 7 relative to the amount of movement in the longitudinal direction of the cutting tool 7 differs depending on the processing position, the material W is also formed with teeth whose gear ratio changes in the longitudinal direction.

In addition, when the cutting tool 7 is raised, the material W
If the cutting tool 7 remains in strong contact with the material W, it will accelerate the wear of the cutting edge and cause the cutting edge to break. Therefore, it is desirable that the cutting tool 7 be slightly separated from the material W when it is raised. This means that when the cutting tool 7 reaches the vicinity of the bottom dead center, the moving table 11 is moved a small distance in the direction away from the cutting tool 7 (direction perpendicular to the feeding direction), and when the cutting tool 7 reaches the vicinity of the top dead center. This is achieved by providing a mechanism for returning to the original position, but if a pusher head 21 is provided as shown by the two-dot chain line in FIG. 21
Almost the same effect can be obtained by pressing the cutting tool 7 against the cutting tool 7 and separating it from the cutting tool 7 when rising.

In addition, since the material W can be mounted parallel to the master rack 13 at a position where it can be processed by the cutting tool 7 and moved together with the master rack 13, the material W can be attached to the cutting tool 7 as shown in FIG. It is also possible to attach the master rack 7 to the side opposite to the master rack 13. The other parts in FIG. 3 are the same as those in the previous embodiment, so the same reference numerals are given and the explanation will be omitted.

[Brief explanation of the drawing]

FIG. 1 is a front view (partially in section) of a main part of a processing device which is an embodiment of the present invention, and FIG. 2 is a side view thereof. FIG. 3 is a side view of another embodiment of the present invention. 1: base, 2: head, 3: ram (reciprocating member), 7: cutting tool, 11: moving table, 13: master rack, W: material.

Claims (1)

[Claims] 1. A device for machining the rack of a variable gear ratio rack and pinion mechanism, which has a shape corresponding to a pinion that can mesh with a desired rack, and has a cutting edge at the tip of each tooth trace. a reciprocating member that rotatably holds the cutting tool and is reciprocated in the axial direction of the cutting tool by a drive mechanism; a master ruck, which is provided with teeth formed to change direction and is intermittently fed in the longitudinal direction between each reciprocating movement of the reciprocating member by an intermittent feed mechanism while meshed with the cutting tool; A variable gear ratio type rack machining device comprising a workpiece holding means that moves together with the master rack while holding the workpiece parallel to the master rack in a position where it engages with the cutting tool.