This gear cutting machine, which is equipped with a cutter (15), a cutter spindle motor (11) that causes, via a crank mechanism (13) and a cutter spindle (16), the cutter (15) perform a stroke operation, and a motor control unit (10) that controls the rotation angle of the cutter spindle motor (11), is provided with a relieving spindle motor (12) that causes the cutter (15) to move in the direction of a relieving spindle via a link mechanism (four-joint link mechanism (14)). The motor control unit (10) controls the rotation angle of the relieving spindle motor (12) on the basis of the rotation angle of the cutter spindle motor (11). Consequently, a gear cutting machine that accurately controls the relieving operation in accordance with a desired shape, such as crowning and tapering of a gear to be cut can be provided.

TECHNICAL FIELD

The present invention relates to a gear cutting machine.

BACKGROUND ART

In conventional gear cutting machines, principally, gear shapers, a cutter spindle motor causes a tool to perform a stroke operation (linear reciprocal movement) in a vertical direction of the tool (in a spindle direction). In addition, in synchronism with this cutter spindle motor, a cam mechanism causes the tool to move toward or away from a gear to be cut in a direction orthogonal to the cutter spindle, that is, to perform a relieving operation.

FIG. 13is a schematic view for explaining a cam mechanism of a conventional gear cutting machine. As shown in this figure, the conventional gear cutting machine has a cam101linked to a cutter spindle motor with a gear train (the illustration is omitted) and configured to rotate mechanically and synchronously. Together with the rotation of the cam101, a cam lever102moves, and the movement of the cam lever102via a four-bar link mechanism104provided to the cam lever102causes a cutter105to perform the relieving operation.

FIG. 14is a schematic diagram for explaining a path of the cutter in the conventional gear cutting machine, and the solid arrow in this figure indicates the path of the cutter. As shown in this figure, the cutter105in the conventional gear cutting machine performs machining in a cutting step (top dead center→bottom dead center), and performs a relieving operation in a returning step (bottom dead center top dead center) so that the cutter105can avoid interfering with a gear21to be cut in the returning step.

PRIOR ART DOCUMENT

Patent Document

Patent Document 1: Japanese Patent Application Publication No. 2004-154921

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

Since the relieving operation of the cutter in the conventional gear cutting machine is determined in accordance with the shape of the cam, the cutter follows the same path. Hence, the relieving operation cannot be performed suitably in a crowning process and a tapering process to be described later. Moreover, it is not easy to replace the cam.

Patent Document 1 discloses, instead of having a cutter spindle motor mechanically generating a driving force required for relieving, a technique of providing a relieving spindle motor independent from the cutter spindle motor: a type of gear cutting machine which performs an NC control on a relieving operation. In this gear cutting machine, the relieving operation is utilized not only for preventing an interference between a cutter and a gear to be cut in a returning step, but also for a crowning process and a tapering process in a cutting step.

FIG. 15is a diagram for explaining the crowning process in the type of gear cutting machine which performs an NC control on a relieving operation, Part (a) thereof shows a schematic diagram for explaining a path of the cutter during the crowning process, and Part (b) thereof shows a perspective view of the crowned gear to be cut. Note that, in this figure, the solid arrow in Part (a) indicates the path of the cutter, and the long and short dash lines in Part (b) indicate the shape of a gear to be cut not having been subjected to the crowning process.

As shown in Part (a) ofFIG. 15, in the cutting step, the cutter105is caused to perform the relieving operation on an arc-shaped path. This makes it possible to perform the crowning process on a gear21to be cut as shown in Part (b) ofFIG. 15.

FIG. 16is a diagram for explaining the tapering process in the type of gear cutting machine which performs an NC control on a relieving operation, Part (a) thereof shows a schematic diagram for explaining a path of the cutter during the tapering process, and Part (b) thereof shows a perspective view of the tapered gear to be cut. Note that, in this figure, the solid arrow in Part (a) indicates the path of the cutter, and long and short dash lines in Part (b) indicate a tapering amount.

As shown in Part (a) ofFIG. 16, in the cutting step, the cutter105is caused to perform the relieving operation on an inclined path. This makes it possible to perform the tapering process on the gear21to be cut as shown in Part (b) ofFIG. 16.

However, since Patent Document 1 does not describe how the relieving spindle motor is controlled, the method for accurately controlling the relieving operation in accordance with a desired shape of a gear to be cut is not clear.

Accordingly, an object of the present invention is to provide a gear cutting machine which accurately controls a relieving operation in accordance with a desired shape of a gear to be cut.

Means for Solving the Problems

A gear cutting machine according to a first aspect of the invention to achieve the above object is a gear cutting machine comprising:

a cutter;

a cutter spindle motor configured to cause, via a crank mechanism and a cutter spindle, the cutter to perform a stroke operation in a direction of the cutter spindle; and

a motor control unit configured to control a rotation angle of the cutter spindle motor, characterized in that

the gear cutting machine comprises a relieving spindle motor configured to cause the cutter to move in a direction of a relieving spindle via a link mechanism, and

the motor control unit controls a rotation angle of the relieving spindle motor based on the rotation angle of the cutter spindle motor.

A gear cutting machine according to a second aspect of the invention to achieve the above object is the gear cutting machine according to the first aspect of the invention, characterized in that

the motor control unitdetermines a track of the cutter on x-y coordinates from tracks of the cutter on x-θ coordinates and on y-θ coordinates, where θ is the rotation angle of the cutter spindle motor, the y-axis direction is the direction of the cutter spindle, and the x-axis direction is the direction of the relieving spindle,determines an inclination angle of the cutter from the track of the cutter on the x-y coordinates (the inclination angle of the cutter is equal to an inclination angle of a cutter head (the illustration is omitted). The same applies hereinafter),determines an output angle of the link mechanism from the inclination angle, anddetermines an input angle of the link mechanism from the output angle, so that the motor control unit controls the rotation angle of the relieving spindle motor.

A gear cutting machine according to a third aspect of the invention to achieve the above object is the gear cutting machine according to the second aspect of the invention, characterized in that the motor control unit performs control such that the track of the cutter in a relieving region on the x-θ coordinates forms a universal cam curve.

A gear cutting machine according to a fourth aspect of the invention to achieve the above object is the gear cutting machine according to the second or the third aspect of the invention, characterized in that the motor control unit divides into two sub-zones each of a zone of a machining region and a zone of the relieving region within the θ, and controls the track of the cutter in each of the divided sub-zones on the x-θ coordinates.

Effect of the Invention

The gear cutting machine according to the present invention makes it possible to accurately control a relieving operation in accordance with a desired shape of a gear to be cut. Thus, the relieving operation can be performed suitably in a crowning process and a tapering process, and is also applicable to internal gear cutting.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a gear cutting machine according to the present invention will be described by way of Embodiment using the drawings.

Embodiment

A gear cutting machine according to Embodiment 1 of the present invention performs an NC control on a relieving operation. The gear cutting machine according to Embodiment 1 of the present invention will be described using Parts (a) and (b) ofFIG. 1.

FIG. 1shows schematic views of the gear cutting machine according to Embodiment 1 of the present invention, Part (a) thereof shows a relieving spindle system, and Part (b) thereof shows a cutter spindle system. As shown in this figure, the present machine includes a motor control unit10, a cutter spindle motor11, a crank mechanism (slider crank mechanism)13, a relieving spindle motor12, a four-bar link mechanism14, a cutter15, and a cutter spindle16.

As shown in Part (b) ofFIG. 1, the cutter spindle motor11is a servomotor configured to cause the cutter15to perform a stroke operation in a y-axis direction by transmitting a rotational movement to the cutter15via the crank mechanism13and the cutter spindle16. Moreover, the crank mechanism13includes a crank arm13aand a connecting rod13b. Note that the y-axis direction refers to a direction of the cutter spindle. Hereinbelow, a direction of a relieving spindle, which is orthogonal to the direction of the cutter spindle, is an x-axis direction.

As shown in Part (a) ofFIG. 1, the relieving spindle motor12is a servomotor configured to cause the cutter15to perform a relieving operation in the x-axis direction by transmitting a rotational movement to the cutter15via the four-bar link mechanism14. Note that, in Part (a) ofFIG. 1, L1, L2, L3, and L4on the four-bar link mechanism14respectively denote lengths of a fixed link, an input link, a coupler link, and an output link. Here, the input link (the link having the length L2) moves together with the rotation of the relieving spindle motor12.

The motor control unit10is configured to control rotation angles (rotational movements) of the cutter spindle motor11and the relieving spindle motor12independently from each other. Hereinafter, the motor control unit10will be described in detail.

FIG. 2is a block diagram for explaining a configuration of the motor control unit10. As shown in this figure, the motor control unit10includes a cutter-spindle-system set unit31, a y-axis-direction track calculation unit32, a relieving-spindle-system input unit33, a rotation-angle allocation unit34, an x-axis direction track calculation unit35, an x-y-coordinates track calculation unit36, a cutter-head inclination-angle calculation unit37, and a relieving-spindle-motor input-angle command unit38.

The cutter-spindle-system set unit31is configured to receive: a value of a face width B (seeFIG. 14) of a gear21to be cut; and calculate a length Larmof the crank arm13abased on the face width B. Moreover, the cutter-spindle-system set unit31is configured to output data on the length Larmof the crank arm13aand on a length Lconof the connecting rod13b, which is a machine-specific constant set in advance, to the y-axis-direction track calculation unit32.

The y-axis-direction track calculation unit32is configured to: determine a shift of the cutter15in the y-axis direction from a rotation angle θ based on the data inputted from the cutter-spindle-system set unit31; and control the rotational movement of the cutter spindle motor11. The phrase determining a shift of the cutter15in the y-axis direction from the rotation angle θ means, in other words, determining a track of the cutter15on y-θ coordinates.

FIG. 4is a graph for illustrating the track (and velocity) of the cutter plotted on the y-θ coordinates (and v-θ coordinates). The track of the cutter15on the y-θ coordinates, that is, y=f(θ), resembles a cosine curve as indicated by the solid line in the graph. Further, the y-axis-direction track calculation unit32is configured to output data on y=f(θ) to the x-y-coordinates track calculation unit36.

The relieving-spindle-system input unit33is configured to: receive data on a relieving amount R, a crowning amount R1, and a tapering amount R2in accordance with the shape of the gear21to be cut; and output the inputted data to the x-axis-direction track calculation unit35. Incidentally, the relieving amount R may be set to a fixed value in advance. Note that all of R, R1, and R2are shift amounts in the x-axis direction.

Moreover, the relieving-spindle-system input unit33is configured to: receive data on the lengths L1, L2, L3, and L4of the fixed link, the input link, the coupler link, and the output link of the four-bar link mechanism14; and output the inputted data to the relieving-spindle-motor input-angle command unit38.

The rotation-angle allocation unit34is configured to set correspondences of the rotation angle θ of the cutter spindle motor11in a single rotation thereof with a cutting step (machining region) and a returning step (relieving region). As shown inFIG. 5, first, the machining region is divided into two sub-zones to obtain θ1 and θ2 as sub-zones of the rotation angle θ respectively corresponding to the two. Similarly, the relieving region is divided into two sub-zones to obtain θ3 and θ4 as sub-zones of the rotation angle θ respectively corresponding to the two.

Meanwhile, as indicated by the broken line inFIG. 4, a velocity v of the cutter15in the y-axis direction in a range of θ=0 to 180 deg. is zero at a top dead center with θ=0 deg. and at a bottom dead center with θ=180 deg., while the velocity v is at its maximum with θ=90 deg. Since the machining efficiency varies in accordance with the velocity v of the cutter15in the y-axis direction, the machining efficiency is lowered around the top and bottom dead centers.

Thus, in the present embodiment, 90±60 deg. is the zone of θ corresponding to the machining region (hatched portion inFIG. 4). Additionally, θ=30 to 90 deg. is θ1, and θ=90 to 150 deg. is θ2.

The rotation angles θ3 and θ4 corresponding to the relieving region are ones obtained by subtracting the rotation angles θ1 and θ2 corresponding to the machining region from the rotation angle θ of the cutter spindle motor11in the single rotation. Here, θ=150 to 270 deg. is θ4, and θ=270 to 30 deg. is θ3.

Note that, in the above description, the rotation angle θ is set to have four sub-zones in total: θ1 and θ2 in the machining region and θ3 and θ4 in the relieving region. Nevertheless, it is also possible to set, for example, two sub-zones in total: one in the machining region and one in the relieving region.

Furthermore, the rotation-angle allocation unit34is configured to output data on the correspondences of the rotation angle θ of the cutter spindle motor11in the single rotation with the machining region and the relieving region, which have been set as described above, to the x-axis-direction track calculation unit35.

The x-axis-direction track calculation unit35is configured to perform setting such that a track of the cutter15in the relieving region (θ3, θ4) on x-θ coordinates forms a universal cam curve based on the data inputted from the relieving-spindle-system input unit33and the rotation-angle allocation unit34.

Normally, the relieving amount R is large in terms of the shift amount in the x-axis direction in comparison with the crowning amount R1and the tapering amount R2. Hence, in considering a case of operating the cutter15at a high velocity, it is necessary to smoothly link the track of the cutter15in the relieving region between an acceleration section and a deceleration section. Accordingly, setting the track of the cutter15plotted on the x-θ coordinates to form the universal cam curve makes a smooth and continuous NC control possible.

The universal cam curve includes various curves as shown in Table 1 below. As exemplified inFIG. 6, curves of a shift S, a velocity V, and an acceleration A can be defined against time T in accordance with specific parameters. Nevertheless, since each curve has its own advantage and disadvantage, an appropriate curve is selected and set in accordance with the purpose of use.

Moreover, the x-axis-direction track calculation unit35is configured to: set a track of the cutter15in the machining region (θ1, θ2) on the x-θ coordinates based on the data inputted from the relieving-spindle-system input unit33and the rotation-angle allocation unit34; and to link and combine the track to the track of the cutter15in the relieving region set as described above by using cubic interpolation.

When a crowning process is performed in the machining region, a track of the cutter15is plotted on the x-θ coordinates, and the track is set in a shape of arc within a range of the face width B, in such a manner as to satisfy a desired crowning shape. The arc is set to have a radius rcbased on the crowning amount R1and the face width B. Specifically, the radius rcis calculated according to the following equation (1).
rc={(0.5·B)2+R12}/2·R1(1)

When the track of the cutter15in the machining region (θ1, θ2) on the x-θ coordinates thus calculated and the above-described track of the cutter15in the relieving region are linked and combined together, a curve as shown inFIG. 7is obtained.

On the other hand, when a tapering process is performed in the machining region, a track of the cutter15is plotted on the x-θ coordinates, and the track is set in a shape of oblique straight line within the range of the face width B, in such a manner as to satisfy a desired tapering process or tapering angle.

When the track of the cutter15in the machining region (θ1, θ2) on the x-θ coordinates thus set and the above-described track of the cutter15in the relieving region are linked and combined together, a curve as shown inFIG. 8is obtained.

The x-axis-direction track calculation unit35is then configured to output data on the track of the cutter15on the x-θ coordinates obtained as described above to the x-y-coordinates track calculation unit36.

The x-y-coordinates track calculation unit36is configured to: continuously plot the track of the cutter15within the rotation angle θ=0 to 360 deg. of the cutter spindle motor11on x-y coordinates based on the data inputted from the x-axis-direction track calculation unit35; determine a track of the cutter15on the x-y coordinates, that is, an actual track of the cutter15; and output data on the track to the cutter-head inclination-angle calculation unit37.

FIG. 9is a graph in which a track of the cutter performing the crowning process is plotted in the x-y coordinates.FIG. 10is a graph in which a track of the cutter performing the tapering process is plotted in the x-y coordinates. Note that the arrows inFIGS. 9 and 10indicate directions in which the cutter moves. For example, within a range of the rotation angle θ=0 to 360 deg., (xi, yi) (i=0, . . . , 360) are plotted. The track of the cutter15on the x-y coordinates thus created is the actual track of the cutter15as shown inFIGS. 9 and 10.

The cutter-head inclination-angle calculation unit37is configured to: determine an inclination angle of a cutter head (the illustration is omitted) for each rotation angle θ of the crank arm13afrom (xi, yi) of the cutter15on the x-y coordinates described above; and output data on the inclination angle ΔΨi(i=0, . . . , 360) thus determined to the relieving-spindle-motor input-angle command unit38.

To be more specific, actually, the relieving spindle motor12and the four-bar link mechanism14cause the cutter15to move in the x-axis direction. The cutter head (the illustration is omitted) including the cutter spindle, to which the cutter15is attached, is capable of freely swinging (inclining) about a fulcrum14aas shown in Part (a) ofFIG. 1. The output link (the link having the length L4in Part (a) ofFIG. 1) of the four-bar link mechanism14and the cutter head has such a relation that the two are always orthogonal to each other. Hence, when the rotation angle of the output link changes in an amount of ΔΨ, the cutter head also inclines at an angle of ΔΨ.

FIG. 11is a schematic diagram for illustrating a relation among the shift amount in the x-axis direction, the shift amount in y-axis direction, and the inclination angle ΔΨ. As shown in this figure, the inclination angle of the cutter head can be calculated according to the following equation (2).
ΔΨ=f(θ)=tan−1(x−y)  (2)

Note that since the inclination angle of the cutter head is equal to the inclination angle of the cutter15, the cutter-head inclination-angle calculation unit37may be configured to determine the inclination angle of the cutter15as described above in place of the cutter head.

The relieving-spindle-motor input-angle command unit38is configured to: determine an output angle Ψ of the four-bar link mechanism14from the inclination angle ΔΨ of the cutter head based on the data inputted from the cutter-head inclination-angle calculation unit37; and inversely calculate an input angle δ from the output angle Ψ (see Part (a) ofFIG. 1).

The output angle Ψ of the four-bar link mechanism14can be calculated according to the following equation (3).
Ψ=Ψ0−ΔΨ  (3)

FIG. 12is a schematic view for illustrating a reference position of the four-bar link mechanism14. When the reference position is set with the inclination angle of the cutter15(the inclination angle of the cutter head) being zero as shown in this figure, the Ψ0represents the output angle (initial output angle) at the reference position. Note that the initial output angle Ψ0can be geometrically determined from a positional relation regarding where the relieving spindle motor12is attached relative to the fulcrum14a, and the lengths L1, L2, L3, and L4of the links.

Here, values of L1to L4, which are machine-specific constants, are inputted from the relieving-spindle-system input unit33. Meanwhile, since the rotation angle θ of the crank arm13adetermines a value of the output angle Ψi, the above-described δi=f−1(Ψi, L1, L2, L3, L4) (i=0, . . . , 360) can be converted to δ(θ)=f−1(Ψ(θ)). According to this equation, the input angle δ of the four-bar link mechanism14is calculated for each rotation angle θ of the crank arm13a(the cutter spindle motor11).

Moreover, the relieving-spindle-motor input-angle command unit38is configured to output a command value Uito the relieving spindle motor12. This command value Uiis calculated from the following equation (4).
Ui=Δδ(θ)=δ(θ)−δ0(i=0, . . . ,360)  (4)

Here, the δ0represents an input angle (initial input angle) at the reference position shown inFIG. 12. Note that the initial input angle δ0can be geometrically determined from the positional relation regarding where the relieving spindle motor12is attached relative to the fulcrum14a, and the lengths L1, L2, L3, and L4of the links.

To be more specific, the amount Δδiof change in the rotation angle of the input link is the command value Uito the relieving spindle motor12.

The configuration of the motor control unit10has been described. Hereinbelow, an operation of the motor control unit10will be described using a flowchart inFIG. 3.

In step S1, the position of the cutter15in the y-axis direction is determined from: the rotation angle of the crank arm13a, that is, the rotation angle θ (θ=0 to 360 deg.) of the cutter spindle motor11, the length Larmof the crank arm13a, and the length Lconof the connecting rod13b. The cutter-spindle-system set unit31sets the values of Larmand Lcon, and thereby the y-axis-direction track calculation unit32can determine the track of the cutter15on the y-θ coordinates as indicated by the solid line inFIG. 4according to y=f(θ) from y=f (θ, Larm, Lcon). In this step S1, the motor control unit10controls the cutter spindle motor11.

In step S2, the relieving-spindle-system input unit33sets the relieving amount R, the crowning amount R1, and the tapering amount R2in accordance with the shape of the gear21to be cut.

In step S3, the rotation-angle allocation unit34sets the correspondences of the rotation angle θ of the cutter spindle motor11in the single rotation with the machining region and the relieving region. As shown inFIG. 5, the machining region is divided into two sub-zones to obtain θ1 and θ2 as the sub-zones of the rotation angle θ respectively corresponding to the two. Similarly, the relieving region is divided into two sub-zones to obtain θ3 and θ4 as the sub-zones of the rotation angle θ respectively corresponding to the two. In the present embodiment, θ1 is θ=30 to 90 deg., θ2 is θ=90 to 150 deg., θ4 is θ=150 to 270 deg., and θ3 is θ=270 to 30 deg.

In step S4, the x-axis-direction track calculation unit35performs setting such that the track of the cutter15in the relieving region (θ3, θ4) on the x-θ coordinates forms a universal cam curve.

In step S5, the x-axis-direction track calculation unit35sets the track of the cutter15in the machining region (θ1, θ2) on the x-θ coordinates, and links and combines the track to the track of the cutter15in the relieving region set in step S4by using cubic interpolation. When a crowning process is performed, a curve as shown inFIG. 7is obtained. When a tapering process is performed, a curve as shown inFIG. 8is obtained.

Through steps S2to5above, shifts of the cutter15in the x-axis direction in the machining region and the relieving region can be defined as a function of θ by x=f(θ).

In step S6, the x-y-coordinates track calculation unit36continuously plots the track of the cutter15, defined through steps S1to5, within the rotation angle θ=0 to 360 deg. of the cutter spindle motor11on the x-y coordinates, and determines the actual track of the cutter15. For example, by plotting (xi, yi) (i=0, . . . , 360) for each rotation angle θ within the range of the rotation angle θ=0 to 360 deg., the actual track of the cutter15as shown inFIGS. 9 and 10is obtained.

In step S7, the cutter-head inclination-angle calculation unit37determines the inclination angle of the cutter head, that is, the output angle ΔΨi(i=0, . . . , 360) of the four-bar link mechanism14, for each rotation angle θ of the crank arm13afrom (xi, yi) of the cutter15on the x-y coordinates obtained in step S6using the equation (2).

In step S8, the output angle Ψ of the four-bar link mechanism14is determined from the inclination angle ΔΨ of the cutter head, and the input angle δ (see Part (a) ofFIG. 1) is inversely calculated from the output angle Ψ.

To be more specific, the relieving-spindle-motor input-angle command unit38, first, geometrically determines the initial output angle Ψ0from the positional relation regarding where the relieving spindle motor12is attached relative to the fulcrum14a, and the lengths L1, L2, L3, and L4of the links, and next determines the output angle Ψ according to the equation (3). Further, the relieving-spindle-motor input-angle command unit38solves the inverse function of the equation Ψi=f (δi, L1, L2, L3, L4) for the input angle δi. Hence, δi=f−1(Ψi, L1, L2, L3, L4) is obtained.

Here, the relieving-spindle-motor input-angle command unit38is configured to receive values of L1to L4, which are machine-specific constants, from the relieving-spindle-system input unit33. The values of L1to L4are inputted from the relieving-spindle-system input unit33. Meanwhile, since the rotation angle θ of the crank arm13a(the cutter spindle motor11) determines the value of the output angle Ψi, δ(θ)=f−1(Ψ(θ)) is obtained. According to this equation, the input angle δ of the four-bar link mechanism14is calculated for each rotation angle θ of the crank arm13a(the cutter spindle motor11). The above is step S8.

In step S9, the relieving-spindle-motor input-angle command unit38geometrically determines the initial output angle δ0from the positional relation regarding where the relieving spindle motor12is attached relative to the fulcrum14a, and the lengths L1, L2, L3, and L4of the links. Next, the relieving-spindle-motor input-angle command unit38calculates the command value Uifrom the equation (4), and further outputs the command value Uito the relieving spindle motor12.

Through steps S1to9above, the motor control unit10is capable of executing an appropriate command to the relieving spindle motor12.

Hereinabove, the gear cutting machine according to Embodiment 1 of the present invention has been described. In other words, the present machine is a gear cutting machine including: the cutter15; the cutter spindle motor10configured to cause, via the crank mechanism13and the cutter spindle16, the cutter15to perform a stroke operation in the direction of the cutter spindle; and the motor control unit10configured to control the rotation angle of the cutter spindle motor10. The gear cutting machine includes the relieving spindle motor12configured to cause the cutter15to move in the direction of the relieving spindle via the link mechanism (the four-bar link mechanism14). The motor control unit10controls the rotation angle of the relieving spindle motor12based on the rotation angle of the cutter spindle motor11.

Moreover, in the present machine,

the motor control unit10determines the track of the cutter15on the x-y coordinates from the tracks of the cutter15on the x-θ coordinates and on the y-θ coordinates, where θ is the rotation angle of the cutter spindle motor11, the y-axis direction is the direction of the cutter spindle, and the x-axis direction is the direction of the relieving spindle,determines the inclination angle ΔΨ of the cutter15from the track of the cutter15on the x-y coordinates,determines the output angle Ψ of the link mechanism from the inclination angle ΔΨ, anddetermines the input angle δ of the link mechanism from the output angle Ψ of the link mechanism, so that the motor control unit10controls the rotation angle of the relieving spindle motor12.

Further, in the present machine, the motor control unit10may perform control such that the track of the cutter15in the relieving region on the x-θ coordinates forms a universal cam curve.

Furthermore, in the present machine, the motor control unit10may divide into two sub-zones each of the zone of the machining region and the zone of the relieving region within the rotation angle θ, and control the track of the cutter15in each of the divided sub-zones on the x-θ coordinates.

With the above configurations, the present machine makes it possible to accurately control a relieving operation in accordance with a desired shape of a gear to be cut. Thus, the relieving operation can be performed suitably in a crowning process and a tapering process, and is also applicable to internal gear cutting.

INDUSTRIAL APPLICABILITY

The present invention is preferable as a gear cutting machine.

REFERENCE SIGNS LIST