Shaving processing method and shaving processing apparatus for gear

A shaving processing method and apparatus for a gear are provided which reduce a load at the time of processing a tooth surface, thereby reducing a transmission error of the gear. Embodiments include a method for finishing the tooth surface of the gear in a state where the gear and a shaving cutter are engaged with each other and the shaving cutter is rotated. The gear has a pair of end surfaces facing each other in the tooth width direction. A first shaving step of processing the tooth surface is performed so that a processing region gradually expands from one end surface of the pair of end surfaces toward the other end surface, and a second shaving step of processing the tooth surface is performed so that a processing region gradually expands from the other end surface of the pair of end surfaces toward the one end surface.

TECHNICAL FIELD

The present disclosure relates to a shaving processing method and a shaving processing apparatus for a gear.

BACKGROUND ART

Japanese Patent Laid-Open No. 2004-154873 discloses a shaving processing method for finishing a tooth surface of a gear by using a shaving cutter. In this shaving processing method, so that an axis of the gear and an axis of the shaving cutter intersect with each other at a previously determined intersection angle, the gear and the shaving cutter are disposed in a state of being engaged with each other, and the shaving cutter is rotated, thereby performing finishing processing of the tooth surface. However, when at the time of finishing processing, a previously determined cut amount of the tooth surface is all cut in one-time processing, the processing load increases, thus easily causing an error. This error causes a transmission error in a rotational angle of the engaged gear, and an increased transmission error may cause vibration and noise.

SUMMARY

The disclosure of the present application provides a shaving processing method and a shaving processing apparatus for a gear which reduce a processing load at the time of processing a tooth surface, and thereby reduce a transmission error of the gear.

A shaving processing method according to an embodiment of the present disclosure is a shaving processing method for finishing a tooth surface of a gear in a state where the gear and a shaving cutter are engaged with each other and the shaving cutter is rotated, the gear comprising a pair of end surfaces facing each other in a tooth width direction. The disclosed method has a first shaving step of processing the tooth surface so that a processing region gradually expands from one end surface of the pair of end surfaces toward the other end surface, and a second shaving step of processing the tooth surface so that a processing region gradually expands from the other end surface of the pair of end surfaces toward the one end surface.

Furthermore, a shaving processing apparatus according to an embodiment of the present disclosure is a shaving processing apparatus for finishing a tooth surface of a gear in a state where the gear and a shaving cutter are engaged with each other and the shaving cutter is rotated, the gear comprising a pair of end surfaces facing each other in a tooth width direction. The disclosed apparatus includes an intersection angle adjusting mechanism which sets an intersection angle between a central axis of the gear and a central axis of the shaving cutter to a first intersection angle and to a second intersection angle corresponding to a finishing condition of the tooth surface.

According to the present disclosure, finishing processing of the gear is divided into the first shaving step and the second shaving step to be performed. The first shaving step and the second shaving step both process the tooth surface to gradually expand the processing regions. At this time, a processing load gently increases, so that the entire processing load is reduced. As a result, an error is suppressed, and a gear with a reduced transmission error can be obtained.

DETAILED DESCRIPTION

Hereinafter, an embodiment of a shaving processing apparatus and shaving processing method according to the present disclosure will be described with reference to the attached drawings. Note that the shaving processing apparatus and shaving processing method of the embodiment described below use a plunge cut shaving method in which a shaving cutter is caused to approach a workpiece gear to thereby process the workpiece gear, but are not limited to this.

Configuration of Shaving Processing Apparatus

FIG. 1is a schematic view of the shaving processing apparatus according to this embodiment. The size of the illustrated apparatus and the size and shape of each of portions constituting the apparatus are shown in an exaggerated manner and differ from the actual ones.

A shaving processing apparatus (hereinafter referred to as a “processing apparatus”)100shown inFIG. 1has a workpiece gear supporting mechanism10. The workpiece gear supporting mechanism10has a gear supporting shaft12detachably supporting a workpiece gear11. In this embodiment, the gear supporting shaft12extends in the left-right direction of the drawing. A central axis13of the workpiece gear11and a central axis14of the gear supporting shaft12coincide with each other in a state where the workpiece gear11is supported by the gear supporting shaft12. Hereinafter, the direction of the central axis14of the gear supporting shaft12is referred to as an “x direction”; the front-back direction of the drawing which is orthogonal to the x direction, a “y direction”; the up-down direction of the drawing which is orthogonal to the x direction and the y direction, a “z direction.”

Workpiece Gear Supporting Mechanism

The gear supporting shaft12is supported by a fixed base15. The gear supporting shaft12may be rotatably fixed to the fixed base15or may be non-rotatably fixed to the fixed base15. When the gear supporting shaft12is rotatably fixed to the fixed base15, the workpiece gear11may be rotatable or non-rotatable with respect to the gear supporting shaft12. When the gear supporting shaft12is non-rotatably fixed to the fixed base15, the workpiece gear11is rotatable with respect to the gear supporting shaft12.

Cutter Driving Unit

The processing apparatus100also has a cutter driving unit20. The cutter driving unit20has a cutter supporting shaft22detachably supporting a shaving cutter (hereinafter referred to as a “cutter”)21. A central axis23of the cutter21and a central axis24of the cutter supporting shaft22coincide with each other in a state where the cutter21is supported by the cutter supporting shaft22. The cutter supporting shaft22is held so that the central axis23of the cutter21and the central axis24of the cutter supporting shaft22are positioned on a surface parallel to an xy plane including the x direction and the y direction.

Cutter Rotating Mechanism

The cutter supporting shaft22is supported by a cutter rotating mechanism31. The cutter rotating mechanism31has a cutter rotating motor32, the cutter rotating motor32is drivingly connected to the cutter supporting shaft22, and the cutter supporting shaft22is configured so as to rotate based on driving of the cutter rotating motor32.

Cutter Lifting and Lowering Mechanism

The cutter rotating mechanism31is supported so as to be capable of lifting and lowering, by a cutter lifting and lowering mechanism33which moves or lifts and lowers the cutter rotating mechanism31in the z direction. In this embodiment, the cutter lifting and lowering mechanism33includes a cutter lifting and lowering motor34, a rotational axis (not illustrated) of the cutter lifting and lowering motor34is drivingly connected to the cutter rotating mechanism31, and the cutter rotating mechanism31is configured to move or lift and lower in the z direction based on driving of the cutter lifting and lowering motor34.

Cutter Turning Mechanism

The cutter lifting and lowering mechanism33is supported by a cutter turning mechanism (intersection angle adjusting mechanism)35. In this embodiment, the cutter turning mechanism35includes a cutter turning motor36, and the cutter rotating mechanism31and the cutter lifting and lowering mechanism33are configured so as to integrally turn and move based on driving of the cutter turning motor36in a state where a center39of the cutter21is positioned at a reference line38in the z direction which passes through a center37of the workpiece gear11supported by the gear supporting shaft12of the workpiece gear supporting mechanism10.

The cutter rotating motor32, the cutter lifting and lowering motor34, and the cutter turning motor36are rotatable in the forward and reverse directions. Alternatively, a mechanism which reverses the rotational direction may be provided in a mechanism which transmits the driving of each of the motors so that this reversing mechanism switches the rotational direction and moving direction (lifting and lowering direction and turning direction) of the cutter.

It is preferable that the cutter lifting and lowering motor34and the cutter turning motor36use a stepping motor to be able to strictly adjust a lifting and lowering amount and a turning amount (turning angle).

Controller

The cutter rotating motor32, the cutter lifting and lowering motor34, and the cutter turning motor36are connected to a controller40and are configured so that, during shaving processing, the driving is controlled based on an instruction output from the controller40. Specifically, a program necessary for performing shaving processing described below is stored in the controller40, and based on this program, the driving of the motors32,34, and36is controlled.

Shaving Processing

An embodiment will be described in which the processing apparatus100including the above configurations is used and a tooth surface of the workpiece gear11is subject to shaving processing.

Workpiece Gear

In this embodiment, the workpiece gear11is a spur gear and has an inner peripheral surface and an outer peripheral surface which are centered on the central axis13, and a pair of end surfaces111and112facing to each other in the direction of the central axis13(tooth width direction), and on the outer peripheral surface, a tooth (workpiece tooth)113(seeFIG. 4) is formed which extends parallel to the central axis13at a constant interval in the peripheral direction.

In a state where the center37of the workpiece gear11coincides with the reference line38, the workpiece gear11is detachably fixed to the gear supporting shaft12so as to be rotatable with respect to the gear supporting shaft12or rotatable together with the gear supporting shaft12.

Cutter

The cutter21has an inner peripheral surface and an outer peripheral surface which are centered on the central axis23, and a pair of end surfaces211and212facing each other and orthogonal to the central axis23, and on the outer peripheral surface, a cutting tooth213is formed which extends in a helical shape at a constant interval in the peripheral direction (i.e., the cutter21of this embodiment is of a helical gear type). As shown inFIGS. 2A-2B, a length214(substantially corresponding to an interval of the pair of end surfaces facing each other) of the cutting tooth213which relates to the direction of the central axis23of the cutter21is sufficiently larger than a length114of the workpiece tooth113which relates to the direction of the central axis13of the workpiece gear11and is determined so that, in a shaving processing state where the central axis23of the cutter21is inclined at a predetermined angle (intersection angles θ1and θ2described later) with respect to the central axis13of the workpiece gear11so as to intersect therewith, the cutting tooth213of the cutter21is engaged with the corresponding workpiece tooth113of the workpiece gear11over the full length of the workpiece tooth113(seeFIG. 2).

In a state where the center39of the cutter21coincides with the reference line38, the cutter21is detachably fixed to the cutter supporting shaft22.

Although inFIG. 1, the workpiece gear11and the cutter21are represented in a state of being engaged with each other, in a state before processing, the workpiece gear11and the cutter21are spaced apart from each other in the z direction. A position of the cutter21at this time is an “initial position” of the cutter21(a position P0inFIG. 6A), and shaving processing described below starts from this initial position.

First Shaving Step

The shaving processing is schematically divided into a first shaving step and a second shaving step. In the first shaving step, the controller40drives the cutter turning motor36to set an intersection angle (an intersection angle as viewed from the z direction) of the central axis24of the cutter supporting shaft22with respect to the central axis14of the gear supporting shaft12to the first intersection angle θ1(seeFIG. 2A). The first intersection angle θ1is larger than an intersection angle (second intersection angle θ2shown inFIG. 2B) corresponding to a finishing condition for obtaining a tooth surface shape of the workpiece gear11which can be finally obtained.

The controller40next drives the cutter lifting and lowering motor34for a predetermined time (from a time T0to a time T1inFIG. 6A) to cause the cutting tooth213of the cutter21to approach a tooth surface115of the workpiece gear11(a cutter position P1after the approach).

Subsequently, the controller40, while driving the cutter rotating motor32and thereby rotating the cutter21, drives the cutter lifting and lowering motor34to cause the cutting tooth213of the cutter21to abut against the tooth surface115of the workpiece gear11, thereby shaving the tooth surface115of the workpiece gear11. A time at which the cutter21contacts the workpiece gear11is a time T12inFIG. 6B. As shown inFIG. 6B, as the shaving of the cutter21increases, a load applied to the cutter21gradually increases. This load applied to the cutter21becomes constant immediately before the shaving of the cutter21reaches a predetermined amount (a cutter position P2inFIG. 6A). When the predetermined amount of the shaving ends, the controller40stops the driving of the cutter lifting and lowering motor34(a time T2and the cutter position P2inFIG. 6A).

As described above, in the first shaving step, the intersection angle of the central axis24of the cutter supporting shaft22with respect to the central axis14of the gear supporting shaft12is set to the first intersection angle θ1which is larger than the second intersection angle θ2corresponding to a final shape of the tooth surface115.

Accordingly, as shown inFIG. 3, for example, at the tooth surface115of the workpiece gear11contacting a driving-side cutting tooth surface215(seeFIG. 4) of the cutter21, the shaving starts from a tooth surface portion117close to one end surface111of the workpiece gear11, and the shaving region (processing region) gradually expands toward a tooth surface portion118close to the other end surface112. Conversely, at a tooth surface116of the workpiece gear11contacting a driven-side cutting tooth surface216(seeFIG. 4) of the cutter21, the shaving starts from a tooth surface portion118′ close to the other end surface112of the workpiece gear11, and the shaving region (processing region) gradually expands toward a tooth surface portion117′ close to the one end surface111. Therefore, as shown inFIG. 6B, the load on the cutter21increases with an increase in the cut amount.

Furthermore, as shown inFIG. 3, at the tooth surface115of the workpiece gear11contacting the driving-side cutting tooth surface215(seeFIG. 4) of the cutter21, the tooth surface portion117close to the one end surface111of the workpiece gear11is shaved deeper than the tooth surface portion118close to the other end surface112, and at the tooth surface116of the workpiece gear11contacting the driven-side cutting tooth surface216(seeFIG. 4) of the cutter21, for example, the tooth surface portion118′ close to the other end surface112of the workpiece gear11is shaved deeper than the tooth surface portion117′ close to the one end surface111.

Note that as shown inFIG. 3, in the first shaving step, a maximum shaved amount of the deeply shaved tooth surface does not reach a final processing tooth surface (a tooth surface119after the second processing).

Next, the controller40, in a state of stopping the driving of the cutter lifting and lowering motor34and maintaining the cutter21at the same position (the cutter position P2inFIG. 6A), maintains the driving of the cutter rotating motor32and executes a first dwell for a predetermined time (from the time T2to a time T3). As shown inFIG. 6B, during this first dwell, the load applied to the cutter21decreases.

When the first dwell ends (the time T3inFIG. 6A), the controller40drives the cutter lifting and lowering motor34to slightly retract the cutter21from the workpiece gear11(a cutter position P3inFIG. 6A).

A state where the cutter21is retracted from the workpiece gear11is maintained for a predetermined time (from the time T3to a time T4inFIG. 6A). Meanwhile, the controller40drives the cutter turning motor36to set the intersection angle of the central axis24of the cutter supporting shaft22with respect to the central axis14of the gear supporting shaft12to the second intersection angle θ2which is smaller than the first intersection angle θ1.

Second Shaving Step

Next, the second shaving step starts, and the controller40, while driving the cutter rotating motor32, drives the cutter lifting and lowering motor34(the time T4and a cutter position P4[=P3] inFIG. 6A) to cause the cutter21to approach the workpiece gear11and cause the cutting tooth213of the cutter21to abut against the tooth surface115of the workpiece gear11, thereby shaving the tooth surface115of the workpiece gear11. A time at which the cutter21contacts the workpiece gear11is a time T45inFIG. 6B.

At this time, as shown inFIG. 3, for example, at the tooth surface115of the workpiece gear11contacting the driving-side cutting tooth surface215(seeFIG. 4) of the cutter21, the shaving starts from the tooth surface portion118close to the other end surface112of the workpiece gear11, and the shaving region (processing region) gradually expands toward the tooth surface portion117close to the one end surface111. Conversely, at the tooth surface116of the workpiece gear11contacting the driven-side cutting tooth surface216(seeFIG. 4) of the cutter21, the shaving starts from the tooth surface portion117′ close to the one end surface112of the workpiece gear11, and the shaving region (processing region) gradually expands toward the tooth surface portion118′ close to the other end surface111. Therefore, as shown inFIG. 6B, the load on the cutter21increases with an increase in the cut amount. This load applied to the cutter21becomes constant immediately before the shaving of the cutter21ends (a cutter position P5inFIG. 6A).

Furthermore, as shown inFIG. 3, at the tooth surface115of the workpiece gear11contacting the driving-side cutting tooth surface215(seeFIG. 4) of the cutter21, the tooth surface portion118close to the other end surface112of the workpiece gear11is more shaved than the tooth surface portion117close to the one end surface111, and the final tooth surface (the tooth surface after the second processing)119is completed. As shown in the drawing, in the final tooth surface119, the tooth surface portion117close to the one end surface111of the workpiece gear11and the tooth surface portion118close to the other end surface112are shaved to the same degree, and the final tooth surface119is left-right symmetrical with respect to a midpoint between both the end surfaces111and112.

When the final tooth surface119of the workpiece gear11is completed (a time T5and the cutter position P5inFIG. 6A), the controller40stops the driving of the cutter lifting and lowering motor34.

During the second shaving step, the rotational direction of the cutter rotating motor32may be reversed. Thereby, left and right tooth surfaces of each of teeth of the workpiece gear11are processed more equally.

Next, the controller40, while stopping the driving of the cutter lifting and lowering motor34, maintains the driving of the cutter rotating motor32and starts a second dwell (the time T5and the cutter position P5). The second dwell is continued for a predetermined time (from the time T5to a time T6).

As required, the controller40, while maintaining the driving of the cutter rotating motor32, drives the cutter lifting and lowering motor34to slightly retract the cutter21from the workpiece gear11(the time T6and a cutter position P6) and performs a third dwell. The third dwell is continued for a predetermined time (from the time T6to a time T7).

Last, the controller40stops the driving of the cutter rotating motor32and drives the cutter lifting and lowering motor34to return the cutter21to the initial position (the time T7and the cutter position P0).

As described above, in the shaving apparatus and the shaving method according to the present embodiment, the shaving step is divided into the first shaving step and the second shaving step. In the first shaving step, the intersection angle between the gear central axis and the cutter central axis is set to the first intersection angle θ1which is larger than the second intersection angle θ2for final finishing and the predetermined amount of the shaving is performed, and in the subsequent second shaving step, the intersection angle is set to the second intersection angle θ2for final finishing. Accordingly, in the first and second shaving steps, at each of the teeth of the workpiece gear, one tooth surface is gradually shaved from one end surface toward the other end surface, and the other tooth surface is gradually shaved from the other end surface toward the one end surface. Accordingly, as apparent fromFIG. 6B, a load which the cutter receives through the shaving method of this embodiment is less than a load received by a cutter in a conventional shaving method (a method in which a relationship between a cut amount and a processing load is shown inFIGS. 7A-B) in which the intersection angle is set to an angle for final finishing (the above-described second intersection angle) and the entire tooth surface is uniformly shaved.

Furthermore, since the load received by the cutter is reduced, as shown inFIG. 8, a transmission error of the gear processed by the shaving method according to this embodiment is smaller than a transmission error of a gear processed by the conventional shaving processing method. As a result, the gear processed by the shaving processing method of this embodiment has further more improved power transmission efficiency and durability than the gear processed by the conventional shaving processing method, reducing gear noise.

OTHER EMBODIMENTS

Although in the above description, the processing apparatus is provided with the intersection angle adjusting mechanism (cutter turning mechanism) and, by this, the intersection angle is adjusted, the intersection angle between the central axis of the workpiece gear supporting shaft and the central axis of the cutter supporting shaft may be maintained constant, and the cutters used in the first shaving step and the second shaving step may be switched. Furthermore, the first intersection angle may be set according to a torsion angle of a cutting tooth of a helical gear type cutter21′ (seeFIG. 9A) used in the first shaving step, and the second intersection angle may be set according to a torsion angle of a cutting tooth of a helical gear type cutter21″ (seeFIG. 9B) used in the second shaving step.

Furthermore, although in the above description, an embodiment is described in which the first intersection angle θ1is set to be larger than the second intersection angle θ2, the first intersection angle may be set to be smaller than the second intersection angle. In this case, the tooth surface after the first processing inFIG. 3inclines in a left and right reversed manner.

Furthermore, although in the above description, an embodiment is described in which the workpiece gear is a spur gear and the cutter is a helical gear type cutter, the present disclosure is also applicable to a processing apparatus and a processing method in which the workpiece gear is a helical gear and the cutter is a spur gear type cutter. Furthermore, the present disclosure is also applicable to a combination in which the workpiece gear is a helical gear and the cutter is a helical gear type cutter, or a combination of a workpiece gear of another shape and a cutter of another shape.