JP2014172112A - Gear processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear processing method which can make surface roughness small, while aiming at shortening of processing time.SOLUTION: By advancing a tool T for processing in a workpiece axis line Lw direction against a workpiece W, cutting processing is performed with an advancing rake face 11 of a tool blade 10 (an outward processing step S1). After the outward processing step, crushing with a retreat rake face of the tool blade 10 or a flank face 12 of the tool blade 10 in the outward processing step is performed by retreating the tool T for processing in the workpiece axis line Lw direction against the workpiece W (a return processing step S3). The return processing step performs processing over the full length in a tooth trace line direction of the gear formed at the outward processing step.

Description

  The present invention relates to a gear machining method.

  As a gear machining method, a machining method as described in JP 2012-45687 A (Patent Document 1) is known. This type of machining method uses a machining tool having a plurality of tool blades on the outer periphery, and in a state where the rotation axis of the workpiece and the rotation axis of the machining tool are inclined, The machining tool is moved in the axial direction of the workpiece while being rotated synchronously.

JP 2012-45687 A

  In a gear, it is required to reduce the step (surface roughness) in the tooth trace direction of the tooth surface. In the above-described machining method, the surface roughness can be reduced by lowering the feed speed of the machining tool, but the machining time becomes longer.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a gear machining method capable of reducing the surface roughness of the tooth surface while shortening the machining time.

  In order to solve the above-mentioned problems, the present inventor has conducted intensive research, and when reciprocating the machining tool with respect to the workpiece, the inventor performs cutting with the machining tool on the forward path and pushes with the machining tool on the return path. The idea of crushing was conceived and the present invention was reached.

  (Claim 1) A gear machining method according to the present means is a gear machining method using a machining tool having a plurality of tool blades on the outer periphery, wherein the workpiece is rotated around a workpiece axis, and the machining is performed. The tool is advanced in the workpiece axis direction with respect to the workpiece while the tool is rotated synchronously with the workpiece around a tool axis inclined with respect to the workpiece axis. An outward path machining step for performing cutting with a forward rake face of the blade, and after the forward path machining process, while rotating the workpiece and the machining tool in the forward path machining step, with respect to the workpiece A backward path machining step in which the machining tool is retracted in the workpiece axial direction to perform a crushing process by a backward rake face of the tool blade which is a flank face of the tool blade in the forward path machining step.The return path machining process is performed over the entire length of the gear formed in the forward path machining process.

Below, the suitable aspect of the gear processing method which concerns on this means is described.
(Claim 2) Further, the gear machining method includes a radial movement in which the machining tool is moved in the cutting direction with respect to the workpiece after the forward path machining process and before the backward path machining process. It is good to provide a process.
(Claim 3) Further, the movement amount in the cutting direction in the radial movement step may be set based on a deflection amount of at least one of the workpiece and the machining tool.

(Claim 4) Further, the return path rake face may be set to a negative rake angle in the return path machining step.
(Claim 5) Moreover, it is good to make the reverse speed in the said backward path | route process higher than the forward speed in the said forward path | route process.
(Claim 6) Further, the forward speed in the forward path machining step and the reverse speed in the backward path machining step may be different.

  (Claim 1) According to this means, the work is crushed by using the backward movement in the return path. Therefore, it is possible to reduce the surface roughness of the tooth surface without reducing the advance speed. As a result, it is possible to reduce the surface roughness of the tooth surface while shortening the processing time.

Further, according to the above means, each tool blade generates a cutting load in the forward path and a crushing load in the return path. According to the above processing method, the tool blades to be cut in the forward path are sequentially changed, and the tool blades to be crushed in the backward path are sequentially changed. Therefore, concentration of load on each tool blade can be avoided.
Furthermore, the surface roughness can be reduced over the entire length of the tooth surface in the tooth trace direction by performing the return path machining step over the entire length of the gear formed in the forward path machining step.

(Claim 2) The crushing force in the return path machining step can be increased by moving the machining tool in the cutting direction before the return path machining step. As a result, the surface roughness of the tooth surface can be further reduced.
(Claim 3) Depending on the rigidity of the workpiece and the machining tool, at least one of the workpiece and the machining tool may be bent and deformed by crushing the machining tool. Even in this case, since the movement amount in the cutting direction is set based on the deflection amount, the surface of the workpiece can be reliably crushed by the tool blade. As a result, the surface roughness can be reliably reduced.

(Claim 4) By setting the return rake face to a negative rake angle in the return path machining step, crushing with a tool blade can be performed without cutting.
(Claim 5) As described above, the crushing range can be widened by setting the return rake face to a negative rake angle. Therefore, even if the backward speed is made faster than the forward speed, the crushing process on the return path can be sufficiently performed. Thereby, shortening of processing time can be aimed at.

  (Claim 6) By making the forward speed and the reverse speed different, the cutting cycle in the forward path and the crushing period in the backward path can be surely made inconsistent in the tooth trace direction. As a result, each tooth surface does not receive a crushing force in the return path over the entire length in the tooth trace direction. Therefore, the surface roughness of all tooth surfaces can be reduced.

It is a figure explaining the basic operation | movement of gear processing, Comprising: It is a figure which shows the position of the workpiece W and the tool T for a process at the time of a cutting start (at the time of the start of the outward process of this embodiment), Comprising: Y-axis direction It is the figure seen from. It is the figure seen from the I (B) direction of FIG. 1A, ie, the X-axis direction. It is a figure explaining the basic operation | movement of gear processing, Comprising: It is a figure which shows the position of the workpiece W and the tool T for a process at the time of completion | finish of cutting (at the time of completion | finish of the outward path | route process of this embodiment), Comprising: It is the figure seen from. It is a partial perspective view of the workpiece W which is a gear. It is a flowchart of the gearwheel processing method in embodiment of this invention. It is a figure which shows the position of the workpiece W and the processing tool T at the time of the start of the outward path | route process S1 of FIG. However, the workpiece W is illustrated with the tooth line direction d in the vertical direction, and the same applies to FIGS. 5B to 5F. It is a figure which shows the position of the workpiece W and the process tool T in the middle of the outward path | route process S1 of FIG. It is a figure which shows the position of the workpiece W and the processing tool T at the time of completion | finish of the outward path | route process S1 of FIG. It is a figure which shows the position of the workpiece W and the processing tool T at the time of completion | finish of radial direction movement process S2 of FIG. It is a figure which shows the position of the workpiece W and the process tool T in the middle of the return path | route process S3 of FIG. It is a figure which shows the position of the workpiece W and the processing tool T at the time of completion | finish of the backward path | route process S3 of FIG. In the gear machining method of FIG. 4, the time change of the command position of the machining tool T in the Z-axis direction is shown. In the case of FIG. 6A, the time change of the command position of the machining tool T in the X-axis direction is shown. In the case of FIG. 6B, the time change of the actual position of the machining tool T in the X-axis direction is shown. FIG. 5 is a diagram showing the relationship of the amount of movement ΔX in the X-axis direction of the machining tool T in the radial movement step S2 of FIG. 4 with respect to the rigidity of the machining tool and workpiece. The deformation | transformation aspect of the tool T for a process is shown. In the gear machining method, the deformation mode of the time change of the command position in the Z-axis direction of the machining tool T is shown.

(Gear processing equipment)
An apparatus to which the gear machining method of the present embodiment is applied is, for example, a 5-axis machining center. That is, the workpiece W and the machining tool T are moved relative to each other in three orthogonal axes, the workpiece W and the machining tool T are rotated about their respective axes, and the rotation axis Lw of the workpiece W (hereinafter referred to as a workpiece). A device capable of inclining a rotation axis Lt of the machining tool T (hereinafter referred to as a tool axis) is applied.

(Basic operation of gear processing)
The basic operation of gear processing will be described with reference to FIGS. Here, a case where gears are formed on the outer peripheral surface of the workpiece W will be described as an example. As shown in FIGS. 1A and 1B, the workpiece W is formed in a disc shape, and a gear is formed on the outer peripheral surface thereof. The workpiece W is supported by the machining center so as to be rotatable around the workpiece axis Lw.

  The machining tool T has a plurality of tool blades 10 on the outer periphery, and is supported by a machining center so as to be rotatable around a tool axis Lt. Each tool blade 10 has an end surface 11 in the tool axis Lt direction and an outer surface 12 on the outer peripheral surface side. The end surface 11 is substantially orthogonal to the tool axis Lt. On the other hand, the outer surface 12 is inclined with respect to the tool axis Lt. And the site | part which the end surface 11 of the tool blade 10 and the outer surface 12 cross is formed in acute angle shape.

  The tool axis Lt is inclined with respect to the workpiece axis Lw. That is, it means that they are not parallel. Here, as shown in FIG. 1B, the workpiece axis Lw is parallel to the Z direction, and the tool axis Lt is inclined in the Z direction.

  Subsequently, while rotating the machining tool T in synchronization with the workpiece W, the machining tool T is advanced in the workpiece axis Lw direction with respect to the workpiece W as shown in FIG. Then, as shown in FIG. 3, a gear having a tooth tip 21, a tooth bottom 22, and a tooth surface 23 is formed.

(Gear processing method of this embodiment)
Next, the gear machining method of the present embodiment will be described with reference to FIGS. As shown in FIG. 4, an outward processing step is performed (S1). The outward machining process is a machining process based on the basic operation of the gear machining described above.

  At the start of the forward machining step, the workpiece W and the machining tool T are positioned as shown in FIG. 5A. At this time, as described with reference to FIGS. 1A and 1B, the workpiece W and the machining tool T are synchronously rotated while the workpiece axis Lw and the tool axis Lt are inclined. Then, the machining tool T is advanced in the workpiece axis Lw direction (−Z direction).

  As the processing tool T moves forward, as shown in FIG. 5B, the end face 11 of each tool blade 10 forms a rake face in advance, and the end face 11 as the advance rake face is cut. At this time, a step corresponding to the forward feed speed is formed on the tooth surface 23 in the tooth line direction d (shown in FIG. 3). Further, since the end face 11 as the forward rake face and the outer surface 12 as the forward flank face are formed at an acute angle, the step shape is formed in a shape that follows the acute angle.

  When the machining tool T is further advanced and the machining tool T is moved over the entire length in the thickness direction of the workpiece W, a tooth surface 23 is formed over the entire length in the thickness direction as shown in FIG. 5C. Then, the outbound process is finished. The maximum height of the surface roughness of the tooth surface 23 at this time is Rz1. The maximum height Rz1 of the surface roughness varies according to the shapes of the end surface 11 and the outer surface 12 of the machining tool T and the feed speed of the machining tool T.

  After the outward processing step, as shown in FIG. 4, a radial movement step is performed (S2). As shown in FIG. 5D, in the radial movement process, the machining tool T is moved in the cutting direction (X-axis direction) in the forward machining process to bring the machining tool T closer to the workpiece axis Lw. Here, also in the radial direction moving process, the workpiece W and the machining tool T are rotated synchronously.

  When the machining tool T is moved in the cutting direction, the machining tool T and the workpiece W receive a radial load on each other. Therefore, the machining tool T and the workpiece W are bent and deformed in the radial direction. In this embodiment, since the rigidity of the machining tool T is lower than the rigidity of the workpiece W, the machining tool T is bent and deformed. As shown in FIG. 5D, when the movement command value in the X-axis direction with respect to the machining tool T is ΔX, the machining tool T is pushed back by the amount of deflection ε. You will be closer to the side.

  After the radial direction moving process, as shown in FIG. 4, a return path machining process is performed (S3). Also in the backward path machining process, the workpiece W and the machining tool T are rotated synchronously continuously from the forward path machining process. Then, the machining tool T is retracted in the workpiece axis Lw direction (+ Z direction).

  As the processing tool T moves backward, as shown in FIG. 5E, the outer surface 12 of each tool blade 10 forms a rake face in the backward movement, and machining by the outer surface 12 as the backward rake face is performed. Here, the outer surface 12 is set to a negative rake angle with respect to the backward direction. In particular, the rake angle is set to be less than −45 ° (an angle larger in the negative direction than −45 °). For this reason, in the backward machining process, the outer surface 12 is not cut and the outer surface 12 is crushed.

  The crushing by the outer surface 12 causes the machining tool T to retreat in the workpiece axis Lw direction while reducing the level difference of the tooth surface 23. Then, as shown in FIG. 5F, the process is finished after the return path machining step is performed over the entire length of the gear tooth direction d of the gear formed by the forward path machining process. The maximum height of the surface roughness of the tooth surface 23 when the return path machining process is completed is Rz2, which is smaller than Rz1. In particular, the surface roughness can be reduced over the entire length of the tooth surface 23.

  With respect to the gear machining method described above, the Z of the machining tool T, the command position in the X-axis direction, and the actual position in the X-axis direction will be described in detail with reference to FIGS. 6A to 6C as time elapses.

  As described above, the machining tool T is advanced in the workpiece axis Lw direction in the forward path machining process, moved in the cutting direction in the radial movement process, and retracted in the workpiece axis Lw direction in the backward path machining process. That is, as shown in FIG. 6A, the command position in the Z-axis direction of the machining tool T moves from Z1 to Z2 in the forward path machining process (t0 to t1). Subsequently, in the radial direction moving step (t1 to t2), the Z-axis direction position of the machining tool T is made constant. Subsequently, in the return path machining step (t2 to t3), the movement is made from Z2 toward Z1. Here, the movement speed of the machining tool T in the forward path machining step and the movement speed in the backward path machining step are set to be the same.

  Further, as shown in FIG. 6B, the command position in the X-axis direction of the machining tool T is held at X1 in the forward path machining process (t0 to t1), and to X2 in the radial movement process (t1 to t2). Moving. The movement amount ΔX as the command position at this time is (X1−X2). And X2 is hold | maintained in a return path | route process (t2-t3).

  However, in the radial movement process and the return path machining process, at least one of the workpiece W and the machining tool T (the machining tool T in the present embodiment) bends and deforms. Therefore, as shown in FIG. 6C, the actual position of the machining tool T in the X-axis direction is held at X1 in the outward machining process (t0 to t1), and to X3 in the radial movement process (t1 to t2). Moving. That is, it is pushed back by the amount of deflection ε. The movement amount ΔXreal as the actual position at this time is (X1−X3). And X3 is hold | maintained in a return path | route process (t2-t3).

  Next, a method for determining a command value for the amount of movement of the machining tool T in the cutting direction in the radial movement step will be described with reference to FIG. First, it is necessary to change the crushing force according to the maximum height of the surface roughness of the tooth surface 23 when the forward path machining process is completed. Further, as described above, at least one of the workpiece W and the machining tool T is bent and deformed in the radial movement process and the return path machining process. Therefore, the amount of movement in the cutting direction is determined in consideration of the amount of deflection. Here, the amount of deflection differs depending on the rigidity of the workpiece W and the machining tool T.

  Therefore, the command value for the amount of movement in the cutting direction is determined based on the maximum height of the surface roughness of the tooth surface 23 at the end of the forward machining process and the rigidity of the workpiece W and the machining tool T. The The relationship of the command value of the movement amount of the machining tool T in the X-axis direction with respect to the rigidity of the workpiece W and the machining tool T is as shown in FIG. That is, the movement amount is larger than the maximum height Rz1 of the surface roughness. Furthermore, the movement amount is reduced when the rigidity is high, and the movement amount is increased when the rigidity is low. For example, in FIG. 7, when the rigidity of the workpiece W and the machining tool T is P, the command value for the amount of movement of the machining tool T in the X-axis direction is ΔX. Here, the rigidity is an index indicating the difficulty of deformation when the workpiece W and the machining tool T receive a force in the X-axis direction.

  According to the above-described embodiment, the workpiece W is crushed by using the backward movement in the return path. Therefore, it is possible to reduce the surface roughness of the tooth surface 23 without reducing the forward speed in the forward path machining step. As a result, it is possible to reduce the surface roughness of the tooth surface 23 while shortening the processing time.

  Furthermore, each tool blade 10 has a cutting load in the forward path and a crushing load in the return path. Since the workpiece W and the machining tool T are rotated synchronously, the tool blades 10 to be cut in the forward path are sequentially changed, and the tool blades 10 to be crushed are sequentially changed in the return path. Therefore, it is possible to avoid concentration of load on each tool blade 10.

  Further, the return path machining process is performed over the entire length of the tooth surface 23 of the gear tooth surface 23 formed by the forward path machining process. Thereby, surface roughness can be made small over the full length of the tooth surface 23 of the tooth trace direction.

  Further, before the return path machining step, the machining tool T is moved in the cutting direction in the radial direction movement step. Thereby, the crushing force with respect to the tooth surface 23 by the processing tool T in the return path machining process can be increased. As a result, the surface roughness of the tooth surface 23 can be further reduced.

  Further, the command value of the moving amount in the cutting direction in the radial moving process is set in consideration of the deflection amount of the workpiece W and the machining tool T and the surface roughness of the tooth surface 23 in the forward machining process. . Therefore, the surface of the tooth surface 23 of the workpiece W can be reliably crushed by the tool blade 10. As a result, the surface roughness can be reliably reduced.

<Deformation mode>
Modifications of the above embodiment will be described below. In the above embodiment, the outer surface 12 of the machining tool T is inclined with respect to the tool axis Lt. In addition, as shown in FIG. 8, the outer surface 12 of the machining tool T is set to a rake angle close to −90 ° with respect to the backward direction. For example, the outer surface 12 is a surface substantially parallel to the tool axis Lt. That is, in the machining tool T, the end surface 11 and the outer surface 12 are substantially orthogonal. In this case, when the outer surface 12 crushes the tooth surface 23 in the return path machining step, the range of crushing at a time can be widened. As a result, the surface roughness of the tooth surface 23 can be further reduced.

  In particular, when the outer surface 12 of the machining tool T is a plane parallel to the tool axis Lt as shown in FIG. 8, the backward speed in the backward machining step (t2 to t13) is set as shown in FIG. It is faster than the forward speed in the processing steps (t0 to t1). As described above, when the outer surface 12 of the machining tool T is a surface parallel to the tool axis Lt, the range to be crushed at a time can be widened. Therefore, even if the reverse speed is made faster than the forward speed, the crushing process can be sufficiently performed in the return path. Thereby, shortening of processing time can be aimed at. Even when the machining tool T shown in FIG. 1A is applied, if the rake angle of the outer surface 12 in the backward direction is less than −45 °, the above-described effect is exhibited when the backward speed is made faster than the forward speed. .

  Further, the present invention is not limited to the case where the reverse speed is made higher than the forward speed, and it is also possible to apply different forward speed and reverse speed. Also in this case, the processing tool T may have the configuration shown in FIG. 1A or the configuration shown in FIG.

  By making the forward speed and the reverse speed different, the cutting cycle in the forward path and the crushing period in the backward path can be surely made inconsistent in the tooth trace direction d. As a result, the tooth surfaces 23 do not receive a crushing force in the return path over the entire length in the tooth line direction d. Accordingly, the surface roughness of all the tooth surfaces 23 can be reduced.

  Moreover, in the said embodiment, the tool T for a process was moved to the cutting direction in the radial direction movement process. In addition, the return path machining process may be performed subsequent to the forward path machining process without applying the radial movement process. In this case, there is no effect of increasing the crushing force in the return path machining step by the radial direction moving step. However, since the crushing process can be performed even if the cutting direction of the machining tool T is the same as that in the forward path machining process in the backward path machining process, the surface roughness is reduced compared to the end of the forward path machining process. I can.

  Moreover, in the said embodiment, the case where a gearwheel was formed in the outer peripheral surface of the workpiece W, ie, the processing method of an external tooth, was demonstrated. In addition, the present invention can also be applied to a case where a gear is formed on the inner peripheral surface of the workpiece W, that is, a method for processing an internal tooth. Moreover, in the said embodiment, although the case where a general purpose machining center was used as an apparatus which applies a gear machining method was mentioned as an example, a dedicated processing machine can also be used.

10: Tool blade, 11: End face (advance rake face), 12: Outer face (advance flank face, reverse rake face), 23: Tooth face, d: Tooth line direction, Lt: Tool axis, Lw: Workpiece axis, S1 : Outward machining process, S2: Radial movement process, S3: Return path machining process, T: Machining tool, W: Workpiece, ΔX: Amount of movement in the cutting direction, ε: Deflection amount

Claims (6)

A gear machining method using a machining tool having a plurality of tool blades on the outer periphery,
The workpiece is rotated with respect to the workpiece while rotating the workpiece around the workpiece axis and rotating the machining tool synchronously with the workpiece about a tool axis inclined with respect to the workpiece axis. A forward machining step in which a tool is advanced in the workpiece axial direction to perform cutting by the forward rake face of the tool blade;
After the forward path machining step, the work tool and the machining tool are moved backward in the workpiece axial direction with respect to the workpiece while the synchronous rotation in the forward path machining step is performed. A backward path machining step in which crushing is performed by a retreat rake face of the tool blade which is a flank face of the tool blade in the forward path machining step;
With
The return path machining step is a gear machining method in which machining is performed over the entire length of the gear formed in the outward path machining step.   The gear processing method includes a radial movement step of moving the machining tool with respect to the workpiece in a cutting direction after the forward path machining step and before the backward path machining step. Gear machining method.   The gear machining method according to claim 2, wherein the movement amount in the cutting direction in the radial movement step is set based on a deflection amount of at least one of the workpiece and the machining tool.   The gear machining method according to any one of claims 1 to 3, wherein the return rake face is set to a negative rake angle in the return path machining step.   The gear machining method according to claim 4, wherein a reverse speed in the backward path machining step is set higher than a forward speed in the forward path machining step.   The gear machining method according to any one of claims 1 to 5, wherein a forward speed in the forward path machining step and a reverse speed in the backward path machining step are different.

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