JPH05301160A - Grinding wheel correction device - Google Patents

Abstract

PURPOSE:To correct errors due to charge in temperature when the tooth surface of a cylindrical worm shaped grinding wheel is corrected. CONSTITUTION:The temperature Tt of a cylindrical worm gear shaped grinding wheel 27 is detected by a first temperature sensor 61, and the temperature Tm of a drive means (made up of a motor 41, a ball screw 42, and of a ball nut 43) for driving the grinding wheel 27 in the axial direction is detected by a second temperature sensor 62. A relative feed per tooth L between the grinding wheel 27 and a truer 25 is corrected at the time of truing based on both the temperatures Tt and Tm in such a way that a relative moving lead between the grinding wheel 27 and the truer is equal to the lead of the grinding wheel 27. This constitution thereby allows each addendum of the truer 25 comes in contact with both the surfaces of each space of the grinding wheel 27, so that truing is thereby accurately carried out regardless of change in temperature. The same method can be applied to the case of dressing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grindstone correcting device for correcting an error with respect to a temperature change when correcting (truing or dressing) a tooth surface of a cylindrical worm-shaped grindstone.

[0002]

2. Description of the Related Art In a gear grinder for processing a helical gear or the like using a cylindrical worm-shaped grindstone, truing is performed to adjust the tooth surface of the cylindrical worm-shaped grindstone in order to improve processing accuracy, and It is necessary to correct the tooth flank of the cylindrical worm-shaped grindstone in which the projection height of the abrasive grains becomes uneven or clogging occurs after the machining. The truing is performed using, for example, a disk-shaped truer having a tip cross-sectional shape that matches the tooth profile of a cylindrical worm-shaped grindstone. Fine diamond particles are attached to the tooth tip surface of this truer, and the surface of a cylindrical worm-shaped grindstone can be ground.

When truing a cylindrical worm-shaped grindstone with this truer, the tooth tips of the truer are brought into contact with the tooth surfaces of the cylindrical worm-shaped grindstone rotating at a constant speed.
While rotating the truer at a speed higher than the rotational speed of the grindstone, the truer is relatively moved in the axial direction by a lead obtained by multiplying the pitch of the grindstone by the number of threads for one rotation of the cylindrical worm-shaped grindstone. By such an operation, the tooth surface of the cylindrical worm-shaped grindstone is trued by the truer, and the entire tooth surface is corrected. Also in the case of dressing, a dresser is used instead of the truer, and the tooth flank of the grindstone is corrected by the same operation as described above.

[0004]

However, since the cylindrical worm-shaped grindstone is thermally expanded by the working operation, the pitch changes before and after the working. Further, most of the driving devices for relatively moving the cylindrical worm-shaped grindstone and the correction tool are of a ball screw type, and the length of this ball screw also changes due to thermal change. However, in the above-mentioned truing operation, since the relative movement amount of the truer and the whetstone for one rotation of the cylindrical worm-shaped whetstone is set to a predetermined lead, the lengths of the whetstone and the ball screw are changed by the temperature change. In this case, the relative movement amount does not match the lead obtained by multiplying the pitch of the grindstone by the number of threads, and the tooth tips of the truer come into contact with only one surface of the tooth groove of the grindstone in a “single contact” state. .. For this reason, only one of the tooth flanks of the grindstone is trued by the truer, and it is not possible to evenly true both sides of the tooth groove of the grindstone. This also applies to dressing.

[0005]

In order to solve the above-mentioned problems, a grindstone correcting device of the present invention is a tool for correcting a tooth surface of a cylindrical worm-shaped grindstone, and a relative movement between the correcting tool and the grindstone. A driving device for controlling the driving device, a control device for controlling the driving device, a first temperature detecting means for directly or indirectly detecting the temperature of the cylindrical worm-shaped grindstone, and a direct or indirect temperature for the driving device. Second temperature detecting means for detecting the relative movement of the grindstone and the correction tool for one rotation of the grindstone based on the temperature of the cylindrical worm-shaped grindstone and the temperature of the driving device. It is characterized in that it comprises a correction means for correcting the lead.

[0006]

The pitch of the cylindrical worm-shaped grindstone changes in proportion to the change in the length of the grindstone due to the temperature change, and the change in the temperature of the drive device for relatively moving the grindstone and the correction tool causes the grindstone to move. The relative movement amount with the correction tool changes.
Therefore, by detecting the temperature of the grindstone and the temperature of the drive device, the relative movement lead between the grindstone and the correction tool for one rotation of the grindstone when the drive device relatively moves the grindstone and the correction tool is obtained. Therefore, by correcting the relative movement lead after the temperature change to be equal to the lead of the grindstone after the temperature change, the grindstone can always be corrected accurately regardless of the temperature change.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a grindstone correcting device according to the present invention will be described below with reference to the drawings. The grindstone correcting device of the present embodiment is integrally provided on a gear grinding machine as shown in FIG. This gear grinding machine uses a cylindrical worm wheel 27
Is a grinding device for grinding helical gears and the like. A movable table 12 is mounted on the machine base 11 so as to be horizontally movable, and a ball nut 14 is fixed to the lower surface of the movable table 12. The ball nut 14 is screwed onto a ball screw 13 installed inside the machine base 11. By rotating the ball screw 13 in the forward and reverse directions by the motor 15 attached to one end of the machine base 11, the movable table 12 moves forward and backward in the left-right direction on the machine base 11 together with the ball nut 14. A headstock 16 and a tailstock 17 are mounted on the movable table 12 so as to face each other and movable on the movable table 12 in the left-right direction in the drawing. On the back surface of the headstock 16, a coolant nozzle 60 for supplying a coolant (grinding liquid) for cooling the grindstone 27.
Is fixed.

As shown in the side view of FIG. 2, a column 23 is provided upright on the rear side (right side in the figure) of the movable table 12, and on the front surface of this column 23, a rotary table 18 is mounted. It is rotatably supported by 44. A grindstone base 19 is supported on the front surface of the rotary base 18. A shaft 20 that is rotated by a motor 45 fixed to a column 23 is hung on the back surface of the rotary table 18.
A circular worm wheel 22 that meshes with the worm 21 axially mounted on the shaft 0 is provided on the outer periphery of the shaft 44. Motor 45
By rotating the worm 21 forward and backward, the rotary table 18 rotates about the shaft 44. Also, column 2
A ball screw 47 that is rotated by a motor 46 fixed to the machine base 11 and a ball nut 48 fixed to the column 23 are provided in the lower part of the column 3.
3 moves forward and backward (forward and backward in the figure). The rotary table 18 is provided with a ball screw 42 that is rotated by a motor 41 that is fixed to the rotary table 18 and a ball nut 43 that is fixed to the grindstone table 19.
Moves in the axial direction. The motor 41, the ball screw 42, and the ball nut 43 correspond to the drive device described in claim 1.

The cylindrical worm-shaped grindstone 27 has a structure in which abrasive grains are electrodeposited on the surface of a metal core processed and formed with high accuracy by a composite plating treatment of a nickel plating layer for high processing accuracy. There is. The abrasive grains to be electrodeposited have a shape close to a sphere with a uniform grain size obtained by sieving with a fine mesh, and only one abrasive grain layer is formed on the surface of the core.

On the rear upper surface of the movable table 12,
A truing device 24 is erected about a vertical axis. At the upper end of the truing device 24, a disc-shaped truer 25 is rotatably supported so as to rotate in a horizontal plane. The truer 25 is rotated by a motor (not shown) provided below the truing device 24. The cross-sectional shape of the tooth tip of the truer 25 matches the cross-sectional shape of the tooth groove of the grindstone 27. Further, diamond fine particles are uniformly attached to the tooth tip surface of the truer 25.

Further, this gear grinding machine is controlled by a control device having a central processing unit 51 using a microcomputer, as shown in the block diagram of FIG. The central processing unit 51 includes signals from various data input devices 52 and a motor 41 fixed to the turntable 18.
From the encoder 58 that detects the amount of rotation of the headstock 16, a signal from the first temperature sensor 61 fixed to the rear surface of the headstock 16, and a second temperature sensor fixed near the ball screw 42 on the rear surface of the wheel head 19. The signal from 62 is input.
The memory 57 connected to the central processing unit 51 stores a machining program for controlling gear grinding, and a truing program for controlling truing. The first temperature sensor 61 detects the temperature of the coolant discharged from the coolant nozzle 60, and the second temperature sensor 62 detects the temperatures of the ball screw 42 and the ball nut 43.

Further, the central processing unit 51 has a signal for controlling the driving of the motors 15, 41, 45, 46, etc. for driving the respective parts of the gear grinding machine, and a coolant pump for supplying the coolant to the coolant nozzle 60. A signal for instructing driving / stopping (not shown) is output. In FIG. 2, the motor 4 driven during the truing operation described later
Only the control systems 1 and 46 are shown, and the control systems of the other motors are assumed to be configured by similar circuits. Pulse distribution circuit 5
Reference numerals 3 and 54 are circuits that distribute the control pulse signal output from the central processing unit 51 so as to be a signal for driving the motors 41 and 46. The drive circuits 54 and 56 use the motor 4 based on the output signals from the pulse distribution circuits 53 and 54.
It is a circuit that supplies a drive current to 1, 46.

When performing grinding with this gear grinding machine, as shown in FIG. 1, a shaft 29 of an object to be ground 30 is horizontally supported between a chuck 28 of a headstock 16 and a tailstock 17. The object to be ground 30 is ground using the cylindrical worm-shaped grindstone 27 mounted on the spindle 26 of the grindstone base 19. When the object to be ground 30 is processed several times, the teeth of the cylindrical worm-shaped grindstone 27 are worn and deformed. Therefore, the truer 25 performs a truing operation for correcting the tooth surface to the original tooth profile. This truing operation is performed according to the truing program. The contents of this truing program are shown in the flow chart of FIG. The truing operation will be described below with reference to this flowchart.

The truing operation in the gear grinding machine of this embodiment is carried out by moving the movable table 12 to the right in the drawing from the state shown in FIG. 1 and moving the truer 25 in front of the cylindrical worm-shaped grindstone 27. At this time, it is conceivable that the cylindrical worm-shaped grindstone 27 is thermally expanded by the heat generated during processing and the axial length becomes longer than that at room temperature, and the pitch also increases accordingly. Further, the ball screw 42 and the ball nut 43 for moving the grindstone 27 in the axial direction are also thermally expanded and the axial length becomes longer than that at room temperature, and the movement of the ball nut 43 per rotation of the ball screw 42. It is possible that the number of leads is also increasing. Therefore, in this embodiment, before the truer 25 is brought into contact with the grindstone 27,
Based on the temperature Tt of the cylindrical worm-shaped grindstone 27 (hereinafter, referred to as grindstone temperature) Tt and the temperature of the ball screw 42 and the ball nut 43 (hereinafter, referred to as device temperature) Tm, the grindstone and the truer 25 for one rotation of the grindstone 27. Correct the relative movement lead of.

The truing program shown in FIG. 4 is automatically executed every time a predetermined number of workpieces 30 have been machined, or a truing start switch (not shown) provided in the input device 52. It is executed by an on operation. When this truing program is started, first, in step 70, the motors 15, 41, 46 are driven to move the movable table 12, the column 23, and the grindstone base 19, so that the grindstone 27 is discharged from the coolant nozzle 60. The coolant is moved to a position where it hits the grindstone 27. At this time, the position of the whetstone base 19 is the encoder 58.
Calculated based on the output of.

Next, at steps 71 and 72, the timer 59 is reset to 0 and started. The timer 59 is set to a time (for example, 5 to 6 minutes) required until the grindstone 27 is cooled by the coolant and the temperature of the whole grindstone 27 becomes equal to the temperature of the coolant. Therefore, the first
The temperature sensor 61 detects the temperature of the coolant, which means that the temperature of the grindstone 27 is indirectly detected. Then, in step 73, the coolant pump is driven to discharge the coolant from the coolant nozzle 60. This coolant discharge operation is performed in step 7
In step 4, the process continues until the set time of the timer 59 elapses. During this time, the grindstone 27 is cooled by the coolant, and the temperature of the whole grindstone 27 becomes equal to the temperature of the coolant.

When the set time of the timer 59 has elapsed, in step 75, the coolant pump is stopped, and then the motors 15, 41 and 46 are driven to move the grindstone 27 to the truing start position. As shown in FIG. 3, the truing start position is set so that the lower surface 27A of the grindstone is located above the tooth tip 25a of the truer 25 by a predetermined distance La. The predetermined distance La is a predetermined temperature (for example, room temperature)
The pitch t of the grindstone 27 at that time is set as a reference, and the distance is about 2t to 3t. This is because the rotation speeds of the grindstone 27 and the truer 25 are not stable immediately after the truing is started, and therefore, the idling period for preventing the truer 25 and the grindstone 27 from coming into contact with each other until the rotation speeds become stable. It is for providing. The truing end position E is set to a position where the upper surface 27B of the grindstone is lower than the tooth tip 25a of the truer by a predetermined distance Lb.

By the way, the truing operation is carried out by lowering the grindstone 27 in the axial direction between the truing start position S and the truing end position E (the feed amount) L. In order to make the tooth tips 25a of the truer 25 evenly contact both sides of the tooth groove of the whetstone 27, the pitch of the whetstone 27 per rotation of the whetstone 27 is set to the whetstone 2
It is necessary to relatively move the grindstone 27 and the truer 25 with the lead multiplied by the number of threads. The relative movement lead is set based on the pitch t of the grindstone 27 at a predetermined temperature (for example, room temperature) and the movement amount of the grindstone 27 per one rotation of the ball screw 42, and is incorporated in the truing program. That is, the feed amount L at the predetermined temperature is the grinding wheel 2
The number of times the grindstone 27 rotates while the 7 moves (for example,
A length obtained by dividing the feed amount L by 8 rotations) is set to be the relative movement lead. This feed amount L is the length of the grindstone 27 at the predetermined temperature L0
Then, L = La + Lb + L0. Since the feed amount L changes due to the temperature change of the grindstone 27 and the ball screw 42, the correction is performed in the following steps 76 to 78.

At step 76, the grindstone temperature Tt detected by the first temperature sensor 61 and the apparatus temperature Tm detected by the second temperature sensor 62 are input, and the temperature difference Δt (T
Calculate m-Tt). Then, in step 77, the feed amount L of the grindstone is corrected. The correction of the feed amount L is performed as follows. Here, the linear expansion coefficient of the material of the core of the grindstone 27 is α1, and the linear expansion coefficient of the material of the ball screw 42 is α2.

The linear expansion amount ΔLm with respect to the temperature change ΔT of the object having the length Lm and the linear expansion coefficient α is approximately ΔLm = α
It is represented by Lm ΔT. Therefore, the length after temperature change Lm + Δ
Lm is Lm + ΔLm = Lm (1 + αΔT). Therefore, the grindstone 27 linearly expands by α1 ΔTt (ΔTt is a change in the grindstone temperature), and the ball screw 42 is α2 ΔTm (ΔT
Since m is the linear expansion of the temperature of the equipment),
The distance that the grindstone 27 moves while rotating the grindstone 27 a predetermined number of times (eight times in this embodiment), that is, the feed amount after temperature change (hereinafter referred to as the corrected feed amount) L + ΔL is L + ΔL = L (1 + α1 ΔTt − α 2 ΔTm) (1) Here, specifically, the core of the grindstone 27 is
The same material as that of the ball screw 42 is used, and the linear expansion coefficient is steel of 12 × 10 ⁻⁶ . Therefore, the above equation (1) is L + ΔL = L (1 + 12 × 10 ⁻⁶ Δt) (2) Therefore, using this equation (2), the correction feed amount L
+ ΔL is calculated and stored in the memory 57.

Then, in step 78, based on the corrected feed amount L + ΔL, the motor 41 is controlled to rotate the ball screw 42 so that the grindstone 27 rotates a predetermined number of times (here, 8 times) during this period. Adjust speed and number of rotations. As a result, the grindstone 27 moves relative to the truer 25 by the lead of the grindstone 27 after one temperature change per rotation of the grindstone 27, and the tooth tips 25a of the truer evenly contact both surfaces of the tooth groove of the grindstone 27. , You can do accurate truing. After performing the truing in this way and moving the grindstone 27 to the end position E, the grindstone 27 is returned to the original position in step 79 to end the truing operation.

The present invention is not limited to the above-described embodiment. For example, the structure in which the position of the grindstone 27 is fixed and the truer 25 is moved in the axial direction at the time of truing is similarly applied. The invention can be applied. In this case, the temperature sensor 62 is attached to a position for detecting the temperature of the ball screw 13 for moving the truer 25. Further, the temperature sensors 61 and 62 which detect the temperature of the grindstone 27 and the temperature of the ball screw 42 may directly detect these temperatures.

Further, dressing of the grindstone 27 can be performed by providing a dresser having the same shape in place of the truer 25. In this case as well, by the same control operation as in the above embodiment, accurate dressing can be performed regardless of temperature changes.

[0024]

As described in detail above, the grindstone correcting apparatus of the present invention detects the temperature of the cylindrical worm-shaped grindstone and the temperature of the drive device that relatively moves the grindstone and the correcting tool to detect the grindstone. By compensating the relative movement lead of the grindstone and the correction tool for one rotation of, according to the temperature change,
Even if the length of the grindstone changes due to thermal expansion due to grinding, etc., and the relative feed amount between the grindstone and the correction tool changes due to the change in the temperature of the drive device, the grindstone is always irrespective of this temperature change. Can be corrected accurately.

[Brief description of drawings]

FIG. 1 is a front view of a gear grinding machine including an embodiment of a grindstone correcting device according to the present invention.

FIG. 2 is a side view of the gear grinding machine and a block diagram of its control device.

FIG. 3 is a side view showing a relationship between a grindstone and a truer during truing in the apparatus of the embodiment.

FIG. 4 is a flowchart showing the contents of a truing program in the apparatus of the embodiment.

[Explanation of symbols]

18 ... Rotating table 19 ... Whetstone stand 24 ... Truing device 25 ... Truer 27 ... Cylindrical worm-like grindstone 41 ... Motor 42 ...
Ball screw 43 ... Ball nut 50 ... Control device 60 ... Coolant nozzle 61 ... First temperature sensor 62 ... Second temperature sensor L
… Feed amount L + ΔL… Corrected feed amount

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhisa Watanabe 1-1, Asahi-machi, Kariya city, Aichi Toyota Koki Co., Ltd. (72) Tomoyuki Kasuga 1-1-1, Asahi-cho, Kariya city, Aichi Toyota machine Within the corporation

Claims (1)

[Claims] 1. A correction tool for correcting a tooth surface of a cylindrical worm-shaped grindstone, a drive device for relatively moving the correction tool and the grindstone, a control device for controlling the drive device, and the cylindrical worm-shaped grindstone First temperature detecting means for directly or indirectly detecting the temperature of the driving device, and a second temperature detecting means for directly or indirectly detecting the temperature of the driving device.
And a temperature detecting means for correcting the relative movement lead of the grindstone and the correction tool for one rotation of the grindstone based on the temperature of the cylindrical worm-shaped grindstone and the temperature of the driving device. A grindstone repairing device comprising means.