JP3782545B2 - Gear cutting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gear cutting method for a spiral bevel gear or a hypoid gear, and more particularly to a gear cutting method that enables generation gear cutting by continuous rotation indexing while using a Gleason gear cutting machine.
[0002]
[Prior art]
As shown in FIG. 6, gear cutting of a spiral bevel gear or a hypoid gear is performed by rotating an annular front milling cutter 58 eccentrically supported by a cradle (not shown) as a support body around its cutter axis. One tooth of the virtual generating gear G is revealed by the locus of the cutting edge of the front milling cutter 58, and the front milling cutter 58 is rotated around the cradle axis that coincides with the axis of the virtual generating gear G together with the cradle. Thus, the front milling cutter 58 is continuously revolved and rotated synchronously around its axis to give an ideal meshing motion to a gear material (hereinafter referred to as a workpiece) 61 arranged at a position meshing with the virtual generating gear G. It is based on creating one tooth surface by making it. And if one tooth surface is created, it will index sequentially and the next tooth surface will be created.
[0003]
As a typical example of such a generating gear cutting method, a Gleason type gear cutting machine and a CNC type gear cutting machine (including a dedicated machine having an equivalent function) are known.
[0004]
[Problems to be solved by the invention]
As shown in FIG. 7, the Gleason type gear cutter is configured such that a rotary output from a single motor 51 is transmitted to a front milling cutter 58, a cradle 59, and further a work spindle 60 via gear trains 52 to 57. The rotation of the cradle 59 and the rotation of the work 61 are synchronized, but the same drive source is used for the indexing rotation of the work 61 even though the rotation of the cradle 59 and the rotation of the work 61 are synchronized. Therefore, the rotation of the workpiece 61 is converted into intermittent rotation by the Geneva mechanism 62 and the workpiece 61 is indexed and rotated. Therefore, synchronization between the indexing rotation of the workpiece 61 and the rotational motion of the front milling cutter 58 can be achieved. As a result, gear cutting by continuous rotation indexing of the work 61 is made difficult.
[0005]
Further, in recent years, a part of the gear trains 52 to 57 shown in FIG. 7 has been removed, and instead, motors are individually provided on the work shaft and the cradle shaft, respectively, so that the movement of the pure mechanical gear cutter as described above can be achieved. Trying NC control is also being tried. However, in this case as well, there is no change in performing gear cutting while indexing one tooth at a time, and it is not possible to realize a gear cutting method by continuous rotation indexing with high productivity.
[0006]
On the other hand, although the CNC type gear cutting machine can only realize the gear cutting method by continuous indexing, the machine itself is expensive due to its function, which is not preferable because the equipment cost increases.
[0007]
The present invention has been made paying attention to the problems as described above, and intends to provide a gear cutting method capable of gear cutting by continuous indexing at a relatively low cost only by improving existing equipment. It is.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, when the spiral bevel gear or the hypoid gear is cut, an annular front milling cutter that is eccentrically supported by the cradle is rotated around the cutter axis, and the front milling cutter is rotated. One tooth of the virtual generating gear is revealed by the trajectory of the cutting blade, and the front milling cutter is continuously rotated by rotating the front milling cutter around the cradle axis that coincides with the axis of the virtual generating gear together with the cradle. It is premised on a method in which gear cutting is performed by synchronously rotating a gear material arranged at a position meshing with the virtual generating gear around its axis . Then, each of the cradle, the front milling cutter, and the gear material is individually driven by an individual motor to individually control the rotation angle, and the rotation angle of the front milling cutter and the gear material has a predetermined rotation ratio. The rotation angle ratio of the gear material and the cradle is corrected while the synchronous control is performed so that the rotation angle of the gear material and the cradle is multiplied by the rotation angle ratio of the gear material and the cradle. While being changed during gear cutting, the rotation detection for controlling the rotation angle of the front milling cutter is housed and arranged so as to be positioned on the same axis as the inside of the cutter spindle to which the front milling cutter is mounted. And a rotation sensor directly connected to the cutter spindle .
[0011]
The invention described in claim 2 is characterized in that, in the invention described in claim 1, processing is performed while constantly applying a braking torque to the cutter spindle on which the front milling cutter is mounted.
[0013]
Therefore, according to the first aspect of the present invention, the rotational phases of the cradle, the face mill cutter, and the gear material are individually controlled, so that the respective rotational drive systems can be substantially NC-controlled. This makes it possible to synchronize between the rotation of the cradle and the rotation of the gear material, as well as the indexing rotation of the gear material, and the rotation of the front milling cutter, Generating gear cutting by continuous rotation indexing of gear material becomes possible.
Moreover, during synchronization control between a face milling cutter and the gear material, for the rotation angle of the cradle shall obtain pressure compensation to the rotation angle of the gear material in a predetermined ratio, especially in the face milling cutter and the gear Material By synchronously controlling the rotation angle so that it becomes a predetermined rotation ratio , the rotation angle of the gear material is corrected by the amount obtained by multiplying the rotation angle ratio of the cradle by the rotation speed ratio between the gear material and the cradle. Tooth line creation and tooth profile creation by continuous indexing are performed at the same time only by correction control, not by three-axis control.
[0015]
By changing the rotational speed ratio between the gear material and the cradle during gear cutting, the tooth profile to be created is corrected, and at the same time as the tooth profile creation, for example, tooth contact or mesh transmission error is optimized. Can be planned.
[0016]
Here, when the gear train must be interposed between the front milling cutter and the motor for driving the front milling cutter, the gear cutting by the front milling cutter is an intermittent cutting in the first place. Pitch error due to backlash of the gear train, i.e., backlash, is unavoidable.
[0017]
Therefore, as in the invention described in claim 2 , if the machining is performed while constantly applying a braking torque to the cutter spindle by means such as a brake, for example, the influence on the pitch error due to the backlash can be eliminated.
[0018]
Further, as described above, in order to individually control the rotation phase of the front milling cutter using an independent motor as a drive source, it is necessary to detect the rotation of the front milling cutter, but it is close to the motor. If the rotation is detected at the position, a detection error is generated due to the backlash of the gear train interposed between the motor and the front milling cutter.
[0019]
For this reason, as described above , the rotation is detected by the rotation sensor that is housed in the cutter spindle on which the front milling cutter is mounted so as to be positioned on the same axis as the front milling cutter and is directly connected to the cutter spindle. As a result, the rotation detection accuracy of the front milling cutter is improved, and the synchronization accuracy is increased by following the other axes.
[0020]
【The invention's effect】
According to the first aspect of the present invention, the rotational angles of the cradle, the front milling cutter, and the gear material can be individually controlled, and the NC control of each rotational drive system is substantially achieved. In the past, it was possible to create gears by continuous indexing, which had been impossible without using a high-precision CNC gear cutting machine or a dedicated machine. By synchronously controlling the rotation angle of the milling cutter and the gear material, the rotation angle of the gear material is corrected by the amount of multiplication of the rotation angle ratio of the cradle and the rotation speed ratio of the gear material and the cradle. Tooth straight line creation and tooth profile creation by continuous indexing are performed at the same time by correction control alone, regardless of control, so control can be simplified. There is an effect.
[0022]
In addition, since the rotational speed ratio between the gear material and the cradle is actively changed during the gear cutting, the tooth profile to be created is modified simultaneously with the generation gear cutting, for example, tooth contact or There is an effect that it is possible to optimize the meshing transmission error and the like.
[0023]
Also, rotation detection for controlling the rotation angle of the front milling cutter is accommodated in the cutter spindle to which the front milling cutter is mounted so as to be positioned on the same axis as that and directly connected to the cutter spindle. Therefore, even if a gear train is interposed between the cutter driving motor and the front milling cutter, a detection error may occur in the rotation detection of the cutter due to the backlash of the gear train. There is also an effect of improving the accuracy of synchronization with other axes.
[0024]
According to the second aspect of the present invention, since gear cutting is performed while constantly applying a braking torque to the cutter spindle by means of a brake or the like, in addition to the same effect as the first aspect of the invention, Even if a gear train must be interposed between the front milling cutter mounted on the cutter spindle and the motor for driving the front milling cutter, the pitch error of the gear to be machined due to backlash of the gear train can be reduced. There is an effect that can eliminate the influence of.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
1 to 5 are views showing a preferred embodiment of the present invention. In particular, FIG. 1 shows the overall configuration of a gear cutter to which the present invention is applied, FIG. 2 shows its block circuit diagram, and FIG. 4 shows cross-sectional views of the main part of the cutter spindle.
[0026]
1 and 3, 4 is a front milling cutter (hereinafter simply referred to as a cutter) for gear cutting, 2 is a cradle, and the cradle 2 is located at a position eccentric from its axis a. As shown, the cutter spindle 4 is rotatably supported via the cutter spindle sleeve 3, and the cutter 1 is attached to the tip of the cutter spindle 4. The cutter 1 is rotationally driven by a spindle motor (AC servomotor) 5 via gear trains 6 and 7, while the cradle 2 is also rotationally driven by an AC type servomotor 8.
[0027]
A rotary encoder 9 is provided at the rear end of the cutter spindle 4 as shown in FIG. The rotary encoder 9 is fixedly supported on a mounting base 10 attached to the cutter spindle sleeve 3, while its input shaft 11 is connected to the cutter spindle 4 via a coupling 12, a support shaft 13 and a bolt 14. The rotation angle (number of rotations) of the cutter 1 that is rotationally driven by the spindle motor 5 is detected by the rotary encoder 9 at a position as close as possible to the cutter 1.
[0028]
As shown in FIG. 3, a brake disc 15 is fixed to the cutter spindle 4 at a position closest to the cutter 1, while a brake disc 15 is supported on the side of the cutter spindle sleeve 3 that supports the cutter spindle 4. The caliper 16 is provided so as to sandwich the brake disc 15, and the brake disc 15 and the caliper 16 form a brake 17.
[0029]
Then, the brake shoe 18 supported by the caliper 16 is pressed against the brake disk 15 by hydraulic pressure, so that the cutter 1 is always driven to rotate with a predetermined braking force applied.
[0030]
As shown in FIGS. 3 and 5, the cutter 1 includes a large number of cutter blades 20 a and 20 b arranged in parallel on the outer peripheral edge of a disc-shaped cutter body 19. The cutter blades 20 a and 20 b are arranged as follows. Is a blade group 20 consisting of a pair of cutter blades 20a, 20b (if one is for cutting in the meshing direction side tooth surface, the other is for cutting in the counter meshing direction side tooth surface) along the circumferential direction. A large number of blade groups 20 are arranged along the circumferential direction of the cutter body 19 at an equal pitch.
[0031]
As will be described later, by synchronizing the rotation and revolution movements of the cutter 1 and the rotational movement of the workpiece W, the tooth trace creation and the tooth profile creation by continuous indexing of the workpiece W are performed simultaneously. 5, C ₁ indicates the rotation center of the cutter 1, C ₂ indicates the rotation center of the cradle 2, and the positional relationship among the cutter 1, the cradle 2 and the workpiece W is basically shown in FIG. It is the same as shown in.
[0032]
Further, 21 in FIG. 1 is a work spindle on which a gear material (hereinafter referred to as a work) W is mounted, and 22 is a slide base on which a spindle unit including the work spindle 21 is mounted. The work spindle 21 is a servo motor (AC). Servo motor) 23 is driven to rotate through gears 24 and 25, while slide base 22 is also driven to slide through gears 27 and 28 and ball screw 29 using AC type servo motor 26 as a drive source. It has become.
[0033]
As shown in FIG. 2, both the servo motor 23 for driving the work spindle 21 (C axis) and the servo motor 8 for driving the cradle 2 are provided with a speed detector 30 or 31 as a speed feedback element, The servo motor 23 for driving the work spindle has a rotary encoder 32 as a position feedback element.
[0034]
That is, in the structure of the gear cutting machine of FIG. 1, each of the cradle drive system, the work drive system, and the slide base drive system has an independent servo motor, and each drive system can be controlled individually by NC. It has become.
[0035]
Here, lodgings In conducting a gear cutting of the pinion gear of the bevel gears, as shown in FIG. 2, with the NC controller EGB (Electronic Gear Box) function, the rotation angle of the rotation angle and the workpiece W of the cutter 1 preparative controlled synchronously by a closed loop to a predetermined rotational speed ratio, by for the rotation angle of the cradle 2 adding the correction to the rotational angle of the workpiece W at a predetermined ratio, by continuous rotation indexing of the workpiece W Tooth line creation and tooth profile creation are performed simultaneously.
[0036]
The relative positional relationship between the workpiece W and the cutter 1 and the cradle 2 at the time of machining is basically the same as that shown in FIG. 6 as described above, but as shown in FIG. The only difference is that the blade group 20 is spiral. Further, 34 in FIG. 5 indicates a convex tooth streak (hatched portion), and a concave tooth groove 35 is formed by cutting between the tooth streaks 34 and 34.
[0037]
More specifically, as shown in FIGS. 1 and 5, if the number of teeth to be cut on the workpiece W is Z ₁ and the number of blade groups 20 of the cutter 1 is Z _W , the rotational speed of the cutter 1 and the workpiece W is as follows. ratio Z _1: Z _W, in other words, when the rotation angle of the workpiece W when the cutter 1 is rotated by theta _X and theta _1, in order to perform a tooth trace creation is _{θ 1 = (Z W / Z} 1) × the θ _X. Therefore, as shown in FIG. 2, the output of the rotary encoder 9 attached to the cutter spindle 4 is taken into the EGB function part 36 of the NC controller, and this is multiplied by the tooth number ratio Z _W / Z ₁ of the cutter 1 and the workpiece W. Is added as a correction command to the command signal of the workpiece drive system. As a result, the cutter 1 and the workpiece W rotate synchronously at a rotation speed ratio of Z ₁ : Z _W , and the blade group 20 of the cutter 1 draws an extended epicycloid curve, thereby generating a tooth trace by indexing the continuous rotation of the workpiece W. Is possible.
[0038]
On the other hand, the gear cutting of the pinion gear must make tooth created simultaneously in addition to the tooth trace the creation of the relationship between the rotation of the rotation angle and the cradle 2 of the workpiece W required for this tooth creation, the rotation of the workpiece W When the angle is θ ₂ and the rotation angle of the cradle 2 is θ _Q , θ ₂ = f (θ _Q ).
[0039]
Note that the above f (θ _Q ) is nothing but a function indicating the relationship between the workpiece rotation angle and the cradle rotation angle. Usually, θ ₂ = f (θ _Q ) = R _a × θ _Q (where R _a is The rotation speed ratio between the workpiece and the cradle, usually R _a = constant).
[0040]
Therefore, when the cradle 2 is rotated while synchronously controlling the rotation angles of the cutter 1 and the workpiece W as described above, the rotation angle θ _{2 of the} workpiece W is θ ₂ = with respect to the rotation angle θ _Q of the cradle 2. A difference is given to the rotation angle of the workpiece W so that f (θ _Q ) is obtained. In other words, by correcting the work rotation angle θ ₂ with respect to the previous work rotation angle θ ₁ using an NC linear interpolation function, the correction rotation angle θ of the entire work W θ = θ _{If 1} + θ ₂ and the cutter 1 rotates and revolves once, all teeth are cut by the same amount. By repeating this operation continuously, tooth creation and tooth profile creation are performed simultaneously. .
[0041]
In this case, the tooth surface (tooth profile) shape can be corrected by actively changing the function f (θ _Q ), that is, the rotational speed ratio Ra between the workpiece W and the cradle 2 during gear cutting. For example, it is possible to optimize the tooth contact state and the meshing transmission error at the same time.
[0042]
That is, according to the present embodiment, although the three axes of the cutter driving system, the workpiece driving system, and the cradle driving system can be controlled independently, the cutter 1 and the three axes are not controlled independently. Since the method of correcting the rotation of the workpiece W in accordance with the movement of the cradle 2, it is possible to perform generation gear cutting by continuous rotation indexing with a cheaper equipment configuration.
[0043]
Moreover, as shown in FIG. 1, gear trains 6 and 7 are interposed between the cutter 1 and the spindle motor 5 for rotationally driving the cutter 1, and the cutter 1 is clearly shown in FIG. Since the gear cutting by means of intermittent cutting is a form of intermittent cutting, it is inevitable that a pitch error will occur due to backlash of the gear trains 6 and 7. However, in the above embodiment, the disk brake 17 shown in FIG. 3 is always machined while applying a predetermined braking force to the cutter spindle 4, so that the pitch of the gear to be machined due to the backlash of the gear train described above. The effect on error is eliminated.
[0044]
For the same reason, as shown in FIG. 4, since the rotation of the cutter 1 is detected by the rotary encoder 9 embedded in the cutter spindle 4, the rotation is detected at a position close to the spindle motor 5. In comparison, there is no influence of the backlash of the gear train, and the rotation detection accuracy of the cutter 1 and thus the synchronization accuracy between the workpiece W and the cutter 1 are improved.
[0045]
Here, in the structure of the above-described gear cutting machine, a so-called single indexing type gear cutting process for indexing for each tooth as in the prior art can be performed as necessary. In this case, the rotation of the workpiece W and the rotation of the cradle 2 may be controlled simultaneously by two axes in an open loop manner. Of course, if cutting is performed by the reciprocating movement of the cradle 2 and the workpiece W is cut and rotated when switching from the forward movement to the backward movement, the tooth surface on the meshing side and the tooth surface on the counter meshing side It is also possible to perform processing by making the function f (θ _Q ) described above different.
[0046]
Further, in the case of forming gear cutting of a ring bevel gear ring gear, the cradle 2 is fixed without being rotated, and only the cutting feed is provided by using the degree of freedom of the slide base 22 in FIG. Processing is possible.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an embodiment of the present invention, and is a configuration explanatory diagram of a gear cutting machine used in the gear cutting processing method of the present invention.
FIG. 2 is a block circuit diagram of a control system of each motor shown in FIG.
FIG. 3 is an enlarged view of a main part in the vicinity of the cutter in FIG. 1;
4 is a cross-sectional view of the main part of FIG. 3;
FIG. 5 is an explanatory diagram of the principle by the gear cutting method of the present invention.
FIG. 6 is an explanatory view showing a conventional generating gear cutting method.
FIG. 7 is a configuration explanatory view of a conventional Gleason type gear cutter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Front milling cutter 2 ... Cradle 4 ... Cutter spindle 5 ... Spindle motor 8 ... Servo motor 9 ... Rotary encoder 17 ... Disc brake 20 ... Blade group 20a, 20b ... Cutter blade 21 ... Work spindle 23 ... Servo motor 26 ... Servo motor 32 ... Rotary encoder 36 ... EGB function part W ... Gear material (workpiece)

Claims (2)

When cutting a spiral bevel gear or a hypoid gear, a virtual generating gear is generated by rotating an annular front milling cutter that is eccentrically supported by a cradle around the cutter axis and by the locus of the cutting blade of the front milling cutter. The front milling cutter is continuously revolved by rotating the front milling cutter around the cradle axis that coincides with the axis of the virtual generating gear together with the cradle, and the virtual generating gear It is a method of performing gear cutting by synchronously rotating the gear material arranged at the meshing position around its axis,
While individually driving each of the cradle, the front milling cutter and the gear material by an individual motor, the respective rotation angles are individually controlled,
While controlling synchronously so that the rotation angle between the front milling cutter and the gear material becomes a predetermined rotation ratio, the rotation angle of the gear material is set by the amount obtained by multiplying the rotation angle ratio of the gear material and the cradle by the rotation angle of the cradle. While adding corrections ,
While changing the rotation speed ratio between the gear material and the cradle during gear cutting ,
The rotation detection for controlling the rotation angle of the front milling cutter is housed and disposed in the cutter spindle on which the front milling cutter is mounted so as to be positioned on the same axis as the front milling cutter and is directly connected to the cutter spindle. A gear cutting method characterized by being performed by a rotation sensor .   2. The gear cutting method according to claim 1, wherein the cutting is performed while constantly applying a braking torque to a cutter spindle on which the front milling cutter is mounted.

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