JPH08147017A - Cam grinding device - Google Patents

Abstract

PURPOSE: To suppress an increase in error even when the value of a gain is increased for a request for small-frequency grinding by controlling a forward/ backward movement position between a work and a grinding wheel by using correction value data when the maximum value of an error in every rotation of the work becomes minimum. CONSTITUTION: A one-rotation detection signal from a C-axial single-rotation detection part 37, data on the current position of a slider from an X-axial position counter 20, and target position data of the slider at corresponding time from an X-axial data memory 13 are inputted to a maximum error value detection part 38. Then the detection part 38 compares the data on the current position inputted from the X-axial position counter 20 with the target position data at the corresponding time which is inputted from the X-axial data memory 13 to detect the maximum error value in every rotation. This maximum error value is read by an error increase/decrease judgement part 40 and when it becomes minimum, a target precision setting part 41 outputs a movement position within target precision to memories 34 and 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a cam grinding device capable of accurately forming a cam shape of a cam shaft or the like by grinding.

[0002]

2. Description of the Related Art Conventionally, grinding of a cam such as a cam shaft has been performed by a processing device (cam grinding device) dedicated to the grinding because it is necessary to perform complicated control during grinding.

This cam grinding device is usually shown in FIG.
It is configured as shown in FIG. The cam 2 which is the object to be ground fixedly attached to the main shaft 1 is a cam rotation motor 3
(Hereinafter, referred to as C-axis motor), the grindstone 5 which is rotated by the grindstone rotating motor 4 in the same direction as the rotating direction of the cam 2 is a slider moving motor 6 (hereinafter
It is attached to a slider 7 that moves back and forth in a direction (X-axis direction) perpendicular to the rotation axis (C-axis) of the cam 2 by an X-axis motor. Then, by controlling the C-axis motor 3 and the X-axis motor 6 by the controller 8, the cam 2 is ground by the grindstone 5 to form a desired cam shape. In the figure, “9” is a ball screw.

In the conventional cam grinding device, the cam (C
There is a method in which the feed amount (X axis) of the grindstone is corrected by learning based on the rotation angle of the shaft (see, for example, Japanese Patent Laid-Open No. 3-65706).

FIG. 6 is a block diagram of a control system of such a conventional cam grinding device. The control device 8 has a control unit 11 that controls the grinding process of the cam based on a command from the external control device 10 that manages the process. This control unit 1
1 receives a command signal such as starting and ending the grinding process from the external control device 10 to control the C-axis motor 3 and the X-axis motor 6.

That is, when the grinding start command is input, the control unit 11 outputs the target position data for each time preset in the C-axis data memory 12 and the X-axis data memory 13 at the time when the time counter 14 outputs the target position data. The rotation amount of the C-axis motor 3 and the X-axis motor 6 is calculated based on the input target position data, and the obtained rotation amount is output to the C-axis servo amplifier 15 and the X-axis servo amplifier 16, respectively. To do. These servo amplifiers 15 and 16 respectively supply electric power according to the input rotation amount to the C-axis motor 3 and the X-axis motor 6 to drive them. As a result, the cam 2 and the slider 7 respectively move to the target position corresponding to the target position data according to the time.

At the same time, the C-axis pulse generator 17 and the X-axis pulse generator 18 detect the rotation amounts of the C-axis motor 3 and the X-axis motor 6, respectively, and the detected rotation amounts are the C-axis position counter 19 and the X-axis position counter 19 respectively. It outputs to the axis position counter 20, respectively. These counters 19 and 20 convert the input rotation amount into the current position data corresponding to each target position data according to time, and output it to the control unit 11. Control unit 1
1 compares the input current position data with the target position data and matches the C-axis motors 3 and X to match them.
The shaft motors 6 are controlled respectively. That is, the control unit 11
The C-axis and X-axis pulse generators 17 and 18 and the position counters 19 and 20 feedback-control the C-axis motor 3 and the X-axis motor 6, respectively.

The correction unit 21 calculates a correction value for correcting the relative positional relationship between the rotation angle of the cam 2 and the moving position of the slider 7 which is generated by performing the above feedback control.

That is, the correction unit 21 inputs the current position data of the rotation angle of the cam 2 output from the C-axis position counter 19 and the current position data of the slider 7 output from the X-axis position counter 20. Then, the target position data corresponding to the current position data of the cam 2 input from the C-axis position counter 19 is searched and searched from the target position data for each time stored in the C-axis data memory 12. After the target position data of the slider 7 corresponding to the target position data at the same time is input from the X-axis data memory 13, the input target position data is compared with the current position data of the slider 7 input from the X-axis position counter 20. Then, the deviation (error) is calculated, the correction value is calculated from the calculated deviation (error) by a predetermined correction function, and the calculated correction value is set to the time count. To correspond to the time output from 14 is stored in the X-axis compensation data memory 22. That is, the correction unit 21 sets a correction value for the target position data of the slider 7 stored in the X-axis data memory 13 at the same time as the target position data of the cam 2 corresponding to the current rotation angle of the cam 2. It is supposed to do. Regarding this correction value, learning is performed in consideration of past deviation (error). This learning will be described later.

The control unit 11 controls the X-axis motor 6 as described above.
Is operated to move the slider 7. At this time, the control unit 11 reads the correction value corresponding to this time from the X-axis correction data memory 22 based on the current time output from the time counter 14. Similarly, the target position data corresponding to that time is read from the X-axis data memory 13, the read correction value is added to the read target position data to correct the target position data, and based on the corrected target position data, As described above, the X-axis motor 6 is driven via the X-axis servo amplifier 16.

As described above, the target position data of the slider 7 preset with respect to the time output from the time counter 14 is repeatedly corrected (learned) based on the operation (rotation angle) of the cam 2 and corrected. By controlling the X-axis motor 6 according to the target position data, the grindstone 5
Is corrected so as to match the operation (rotation angle) of the cam 2, the positional relationship between the cam 2 and the grindstone 5 is relatively corrected, and the cam shape can be accurately formed. Like

The correction function unit for obtaining the correction value in the correction unit 21 receives the target position data of the slider 7 input from the X-axis data memory 13 and the X-axis position counter 20 as shown in FIG. 7, for example. A predetermined correction function is calculated from the gain integration unit 23 that multiplies the deviation (error) from the current position data of the slider 7 by a gain, and the output of this gain integration unit 23 and the previously calculated correction value used for correction at that time. And a repetitive correction function unit 24 for calculating a correction value according to. The correction value calculated by the iterative correction function unit 24 is output to the X-axis correction data memory 22 as described above and stored in association with the corresponding time. That is, learning is performed in which error data (correction value) for one rotation is stored in the X-axis correction data memory 22 for each rotation angle of the cam 2 or for each control cycle, and the above data is updated for each rotation to perform repeated correction. We are in control.

[0013]

However, in such a conventional cam grinding apparatus, learning is performed in the correction section 21, but the learning effect is as follows.
As shown in FIG. 8, when the value of the gain used in the gain integration unit 23 is increased, the error is reduced with a small number of learnings, but the error is increased when the learnings are repeated. On the other hand, when the gain value is reduced, the error converges, but it takes time to converge.
For example, when the number of grinding is small in the first place, such as during spark-out, where grinding is performed without cutting (zero depth of cut), it is required that the error be reduced quickly with a small number of learnings (repetition corrections). Therefore, it is necessary to increase the value of the gain. However, when the value of the gain is increased, there is a problem that the error increases with repeated learning as described above.

The present invention has been made in view of the problems of the prior art as described above, and increases the error even when the gain value is increased, especially when grinding with a small number of times is required. It is an object of the present invention to provide a cam grinding device having a learning control function capable of suppressing the above.

[0015]

In order to achieve the above object, a cam grinding apparatus according to a first aspect of the present invention provides a rotary shaft of a work while rotating a work and a grindstone for grinding the work by feedback control. When a desired cam shape is formed by moving the workpiece relatively in the direction perpendicular to it, the relative advance / retreat position between the workpiece and the grindstone is set for each rotation with a preset gain as a reference. In the cam grinding device which is adapted to correct, a work position detecting means for detecting a rotation position of the work, a forward / backward moving position detecting means for detecting a relative forward / backward moving position between the work and the grindstone, and a target position of the work in advance. Work target position storage means that stores each time the set time elapses, and the relative target advance / retreat movement position between the work and the grindstone is stored in advance. Of the data stored in the work target position storage means, and the target position corresponding to the current position of the work detected by the work position detection means. The target advancing / retreating movement position at the same time corresponding to the target position of the retrieved work is read from the target advancing / retreating movement position storing means, and the read target advancing / retreating movement position is detected by the advancing / retreating movement position detecting means. Correction value calculating means for calculating an error by comparing with the advancing / retreating moving position, and calculating the next correction value for the target advancing / retreating moving position at the corresponding time point from the calculated error, and the correction value calculated by the correction value calculating means, respectively. A plurality of correction value storage means for storing at each corresponding time point, and from the plurality of correction value storage means, according to a predetermined rule, The first selection means for selecting the correction value storage means for storing the correction value calculated by the correction value calculation means, and the correction stored inside the plurality of correction value storage means according to a predetermined rule. Second selection means for selecting the correction value storage means for reading the value, and the previous correction value data when the magnitude of the maximum error value of the forward / backward movement position between the work and the grindstone for each rotation of the work changes from decrease to increase. Setting means for outputting a signal for selecting to the second selecting means, and the target advancing / retreating movement position stored in the target advancing / retreating movement position storing means is stored in the correction value storage means selected by the second selecting means. The present invention is characterized by further comprising: a control means for performing correction based on the correction value at the same time point, and controlling the forward / backward movement position between the work and the grindstone using the corrected target forward / backward movement position as a target value.

According to a second aspect of the present invention, there is provided the cam grinding apparatus according to the first aspect, wherein the setting means is
Further, the learning end signal is output to the first selecting means when the magnitude of the maximum error value of the advancing / retreating movement position for each one rotation of the work changes from decreasing to increasing.

According to a third aspect of the present invention, in the cam grinding apparatus according to the first or second aspect, the setting means reduces the maximum error value of the forward / backward movement position for each rotation of the work. It is characterized in that a predetermined signal is generated when the minimum value of the maximum error value per rotation of the work is within the arbitrarily set target accuracy when turning to increase.

According to a fourth aspect of the present invention, in the cam grinding apparatus according to the first, second or third aspect, the setting means preliminarily sets the present position of the work detected by the work position detecting means. A means for generating a work 1 rotation detection signal in comparison with the set origin position (referred to as a first detection means), and a current position detected by the advancing / retreating movement position detection means each time the work 1 rotation detection signal is input. The advancing / retreating movement position is compared with the target advancing / retreating movement position at the same time point stored in the target advancing / retreating movement position storage means to obtain the error at each time point, and the magnitude of the obtained error at each time point is compared to perform one work revolution Means for detecting the maximum error value for each rotation (referred to as second detection means) and means for comparing the detected maximum error value for each one rotation of the workpiece to determine increase / decrease (referred to as determination means). Characterized in that it.

[0019]

In the cam grinding apparatus according to claim 1 configured as described above, when the workpiece and the grindstone are rotated by the feedback control, the workpiece and the grindstone are moved forward and backward relative to the rotation axis of the workpiece. , The correction value calculation means,
The target position corresponding to the current position of the work detected by the work position detection means is searched from the data stored in the work target position storage means, and the target forward / backward movement at the same time corresponding to the searched target position of the work is performed. The position is read from the target advancing / retreating moving position storage means, the read target advancing / retreating moving position is compared with the current advancing / retreating moving position detected by the advancing / retreating moving position detecting means to obtain an error, and the target advancing / retreating at the corresponding time is calculated from the obtained error. The next correction value for the moving position is calculated. The correction value calculated by the correction value calculation means is stored in the correction value storage means selected by the first selection means according to a predetermined rule at each corresponding time point. The control means corrects the target advancing / retreating movement position stored in the target advancing / retreating movement position storage means based on the correction value at the same time point stored in the correction value storage means selected by the second selecting means according to a predetermined rule. Then, the forward / backward movement position between the work and the grindstone is controlled with the corrected target forward / backward movement position as the target value. Then, when the maximum error value of the forward / backward movement position between the work and the grindstone for each rotation of the work changes from decreasing to increasing, the setting means outputs the signal for selecting the previous correction value data to the second selecting means. The control means performs the subsequent control by using the previous correction value data, that is, the correction value data when the magnitude of the maximum error value per one rotation of the work becomes the minimum. As described above, since the subsequent control is performed using the correction value data when the magnitude of the maximum error value per one rotation of the work becomes the minimum, even if the gain value is increased to quickly reduce the error, It is possible to prevent an increase in error thereafter and form the cam shape quickly and accurately. In other words, since the machining accuracy is not impaired and the gain value can be large, the error can be quickly reduced, and both the machining time and the machining accuracy in the grinding process of the cam can be achieved.

Further, in the cam grinding apparatus according to the second aspect, the setting means further ends the learning when the maximum error value of the forward / backward movement position for each rotation of the work piece starts to decrease and then increases. The signal is output to the first selecting means. As a result, the first selection unit disconnects the correction unit and the plurality of correction value storage units, and thereafter, the correction value calculated by the correction value calculation unit is not stored in any correction value storage unit. . That is, the learning is stopped at the time when the maximum error value per rotation of the work changes from decreasing to increasing.
Since the correction value data that minimizes the maximum error value for each rotation is determined, useless learning can be avoided and there is no fear of updating the correction value data due to continuing learning.

Further, in the cam grinding apparatus according to the third aspect of the present invention, the setting means makes one rotation of the work when the magnitude of the maximum error value of the forward / backward movement position per one rotation of the work changes from decrease to increase. Since a predetermined signal (previous correction value data selection signal, learning end signal) is generated when the minimum value of the maximum error for each is within the arbitrarily set target accuracy, at least a certain processing accuracy is secured. be able to.

Further, in the cam grinding apparatus according to the fourth aspect, in the setting means, the first detecting means compares the current position of the work detected by the work position detecting means with a preset origin position. To generate a workpiece 1 rotation detection signal, and the second detection means sets the current forward / backward movement position detected by the forward / backward movement position detection means to the target forward / backward movement every time the workpiece 1 rotation detection signal is input from the first detection means. The error at each time point is calculated by comparing with the target advancing / retreating movement position at the same time point stored in the position storage means, and the magnitude of the error at each time point is compared to detect the maximum error value for each rotation of the work. . The judging means compares the maximum error values for each rotation of the work detected by the second detecting means and judges whether the error increases or decreases. In this way, the setting means can determine whether or not the magnitude of the maximum error value of the advancing / retreating movement position for each rotation of the work piece has changed from decreasing to increasing.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a control system of a cam grinding device according to the present invention. The basic configuration of this control system is the same as that of the conventional one shown in FIGS. 6 and 7 up to the point of feedback controlling the C-axis and the X-axis, respectively. Note that FIG.
The parts common to those in FIG. 7 are designated by the same reference numerals.

First, the overall schematic structure of the cam grinding apparatus to which this control system is applied is the same as that shown in FIG. That is, a cam 2 which is an object to be ground as a work is fixedly attached to the main shaft 1 and is rotationally driven by a cam rotation motor (C-axis motor) 3. On the other hand, the grindstone 5 as a processing tool for grinding the cam 2 is rotationally driven at a high speed in the same direction as the rotating direction of the cam 2 by the grindstone rotating motor 4, for example. The grindstone 5 and the grindstone rotation motor 4 are attached to a slider 7.
The slider 7 is movable by a slider moving motor (X-axis motor) 6 in a direction perpendicular to the rotation axis of the cam 2. That is, in this embodiment, the cam 2
On the other hand, the grindstone 5 is moved back and forth by the slider 7. The cam 2 attached to the spindle 1 is driven to rotate during machining, but since the cam 2 is eccentrically rotated with respect to the spindle 1, the grindstone 5 follows the profile of the cam 2 to perform grinding. It is necessary to move the slider 7 forward and backward with respect to the rotation angle of 1 (or the cam 2). It is necessary to accurately control the rotation angle of the cam 2 and the amount of advance / retreat movement of the slider 7 with respect to the rotation angle of the cam 2 so as to have a preset positional relationship.
This control is performed by the control device 8 controlling the C-axis motor 2 and the X-axis motor 5. Of course, the grindstone rotating motor 4 is also controlled by the controller 8. In this embodiment, the cam 2 and the grindstone 5 are used as described above.
Although they are rotated in the same direction, the rotation directions of both do not necessarily have to be the same direction.

Next, the structure of the control system centering on the control device 8 will be described with reference to FIG. It should be noted that the portions common to the conventional one shown in FIGS. 6 and 7 will be briefly described.

A cam 2 fixedly attached to the main shaft 1 is rotated by a C-axis motor 3. The rotation angle of the C-axis motor 3 is calculated based on the number of pulses output from the pulse generator 17. The pulse from the pulse generator 17 is C
It is counted by the axis position counter 19. Therefore, referring to the number of pulses counted by the C-axis position counter 19, the main shaft 1 (or the cam 2) is rotated by what angle from the origin position (the position when the value of the C-axis position counter 19 is zero). That is, the current rotational position of the cam 2 can be detected. The current position data of the cam 2 detected by the C-axis position counter 19 is the control unit 11 and the correction unit 2.
1 and a C-axis single-rotation detecting unit described later. The work position detecting means is composed of a pulse generator 17 and a C-axis position counter 19.

Since the cam 2 is eccentric, when grinding the cam 2, it is necessary to reciprocate the grindstone 5 for grinding the cam 2 following the cam shape. The X-axis motor 6 reciprocates the slider 7 on which the grindstone 5 is placed during cam grinding. The rotation angle of the X-axis motor 6 is calculated based on the number of pulses output from the pulse generator 18. The pulses from the pulse generator 18 are counted by the X-axis position counter 20. Therefore, by referring to the number of pulses counted by the X-axis position counter 20, the current moving position of the slider 7 can be detected. The current position data of the slider 7 detected by the X-axis position counter 20 is output to the control unit 11, the correction unit 21, and the maximum error value detection unit described later. The advancing / retreating movement position detecting means includes a pulse generator 18 and an X-axis position counter 2.
It is composed of 0s.

The C-axis data memory 12 stores, as target position data, data relating to a target rotation angle for each time from the preset origin position of the spindle 1 (or cam 2). The C-axis data memory 12 is connected to the control unit 11 and the correction unit 21, respectively. Also,
The X-axis data memory 13 stores, as target position data, data relating to a target advance / retreat movement position for each time from the preset origin position of the slider 7. The X-axis data memory 13 includes a control unit 11 and a correction unit 2.
1 and a maximum error value detection unit described later, respectively. The time counter 14 counts time, and this count value is input to the control unit 11,
It is used to synchronize the rotation angle of the cam 2 from the origin position and the feed position of the slider 7 from the origin position.
The work target position storage means is the C-axis data memory 1
2. The target advancing / retreating movement position storage means is the X-axis data memory 13
Each is composed of.

The correction unit 21 functions as a correction value calculation means, receives the current rotation angle of the cam 2 from the C-axis position counter 19, and corresponds to the input current rotation angle of the cam 2. Target rotation angle is C axis data memory 1
2 is searched from the target position data for each time stored in 2, and the target forward / backward moving position of the slider 7 at the same time corresponding to the searched target position of the cam 2 is read from the X-axis data memory 13 and read. The slider 7 that outputs the target forward / backward movement position from the X-axis position counter 20
The error (deviation) is calculated by comparing with the current moving position of
A correction value is calculated from the obtained error by a predetermined correction function. As in the conventional case, the correction function unit for obtaining the correction value in the correction unit 21 is, as shown in FIG. 7, the target position data of the slider 7 input from the X-axis data memory 13 and the slider 7 input from the X-axis position counter 20. A gain integration unit 23 that multiplies an error (deviation) from the current position data of the gain by a gain, and a predetermined correction function that corrects the output of the gain integration unit 23 and the previously calculated correction value used for correction at that time. Iterative correction function unit 2 for calculating values
It consists of 4. The previous correction value used in the iterative correction function unit 24 to calculate the correction value is input from any one of the X-axis correction data memories A to C selected by the correction memory selecting means, as described later. It Also,
The correction value newly calculated by the correction unit 21 corresponds to the time output from the time counter 14 in the X-axis correction data memories A to C selected by the learning memory selection unit, as described later. It is stored in either one.

The control unit 11 also functions as a control means, and is an external control device 1 for performing process management and the like.
When a grinding start command is input from 0, C-axis data memory 1
2 and the target position data corresponding to the time output from the time counter 14 from the X-axis data memory 13, respectively, and based on the respective input target position data, via the C-axis servo amplifier 15 and the X-axis servo amplifier 16. Feedback control is performed on the C-axis motor 3 and the X-axis motor 6, respectively. That is, the current rotation angle of the cam 2 is input from the C-axis position counter 19, the current forward / backward movement position of the slider 7 is input from the X-axis position counter 20, and these input current position data are used as corresponding target position data. Then, the C-axis motor 3 and the X-axis motor 6 are controlled so as to match them. At this time, when operating the X-axis motor 6 to move the slider 7, the target position data corresponding to the current time output from the time counter 14 is read from the X-axis data memory 13, and the read target position is read. The correction value of the time corresponding to the data is added to correct the target position data, and the X-axis motor 6 is feedback-controlled via the X-axis servo amplifier 16 based on the corrected target position data as described above. It has become. Note that, here, the correction value used for correcting the target position data is, as will be described later,
The correction value stored in any one of the X-axis correction data memories A to C selected by the correction memory selecting means is used. In this way, the control unit 11 controls the rotation angle of the cam 2 and the feed amount of the grindstone 5 attached to the slider 7 so that grinding can be performed with a predetermined cut amount while following the cam shape.

In this way, the target position data of the slider 7 set in advance for the time output from the time counter 14 is repeatedly corrected with the operation (rotation angle) of the cam 2 as a reference, and the corrected target position data is obtained. By controlling the X-axis motor 6 by means of, the operation (feed amount) of the grindstone 5 is corrected to match the operation (rotation angle) of the cam 2, so that the positional relationship between the cam 2 and the grindstone 5 is relatively large. The cam shape can be corrected and accurately formed.

In this embodiment, the correction value calculated by the correction unit 21 is stored in any one of the three X-axis correction memories A30, B31, C32 as the correction value storage means.
Which of the X-axis correction memories A to C30 to 32 is to be stored is selected by the learning memory selection unit 33 including a changeover switch, for example. The learning memory selection unit 33 is provided with an OFF contact for disconnecting the correction unit 21 and the memories 30 to 32. The switch position in the learning memory selection means 33 is mechanically switched by the learning memory determination unit 34. The rule of memory selection by the learning memory determination unit 34 will be described later. The first selecting unit is composed of the learning memory selecting unit 33 and the learning memory determining unit 34.

The correction values used by the control unit 11 when operating the X-axis motor 6 are three X-axis correction memories A.
Is input from any one of C30 to C32, which X-axis correction memory A to C30 to 32 is selected.
For example, the correction memory selection means 3 including a changeover switch
Selected by 5. This correction memory selection means 35
The switch position inside is mechanically switched by the correction memory determination unit 36. The rule of memory selection by the correction memory determination unit 36 will be described later. The second selecting unit is composed of the correcting memory selecting unit 35 and the correcting memory determining unit 36.

In this embodiment, which X-axis correction memories A to C are used.
In order to set whether to select 30 to 32, as a setting means, a C-axis single rotation detection unit 37, an error maximum value detection unit 38,
An error maximum value storage unit 39, an error increase / decrease determination unit 40, and a target accuracy setting unit 41 are provided. The C-axis 1 rotation detection unit 37 inputs the current position data of the cam 2 (C-axis) from the C-axis position counter 19, compares the input data with the preset origin position data, and outputs the data of the cam 2 to the cam 2.
A signal indicating that the (C-axis) has rotated once (one-rotation detection signal) is generated. The one-rotation detection signal generated by the C-axis one-rotation detecting unit 37 is output to the maximum error detecting unit 38, the learning memory determining unit 34, and the correcting memory determining unit 36. The maximum error value detection unit 38 detects the single rotation detection signal from the C-axis single rotation detection unit 37 and the X-axis position counter 20 to the slider 7 (X
(Axis) current position data and X-axis data memory 13
The target position data of the slider 7 (X-axis) at the corresponding time are input respectively, and the current position input from the X-axis position counter 20 is input each time one rotation detection signal is input, that is, while the cam 2 makes one rotation. The error (deviation) at each time is calculated by comparing the data with the target position data at the corresponding time input from the X-axis data memory 13, and the magnitude of the error (deviation) at each time obtained (for example, absolute value) And the maximum error value for each rotation is detected. The maximum error value storage unit 39 learns the magnitude of the maximum error value for each rotation output from the maximum error value detection unit 38 by the number of times of learning (that is, the cam 2
The number of rotations is stored. Error increase / decrease determination unit 4
The value 0 indicates that the maximum error value at each learning number is read from the maximum error value storage unit 39 and the increase and decrease of the maximum error value is determined by comparing the data before and after the reading, and the maximum error value for each rotation is determined. The magnitude of the change from monotonous decrease to increase,
And last time (that is, when the maximum error value becomes the minimum)
When the error maximum value of one rotation of is within the target accuracy arbitrarily set by the target accuracy setting unit 41, the previous learning count data and the learning end signal are respectively set to the correction memory determination unit 36 and the learning memory determination. It is output to the unit 34.
In the present embodiment, the absolute value of the maximum error value for each rotation is stored and the increase / decrease thereof is determined, but the present invention is not limited to this, and the magnitude of the maximum error value for each rotation is not limited to this. For this, the square of the maximum error value for each rotation may be used.

The learning memory determination unit 34 and the correction memory determination unit 36 are synchronized with the one rotation detection signal from the C-axis one rotation detection unit 37 until the output signal of the error increase / decrease determination unit 40 is input. Change each X-axis correction memory 30-32 from A → B →
The program is programmed so as to cycle through C → A and select. However, since the correction value data learned this time is used for the next correction, the correction memory is one time behind the learning memory (see FIG. 3). The memory selection means 33 and 35 select the X-axis correction memories by the determination of the memory determination units 34 and 36. After that, the learning memory determination unit 34 determines the error increase / decrease determination unit 40.
When the learning end signal is input from, the learning memory selection unit 33 is switched to the off position and is disconnected from the memory. Further, when the correction memory determination unit 36 receives the learning number data having the minimum error maximum value from the error increase / decrease determination unit 40, the correction memory selection unit 35 selects the correction data memory corresponding to the learning number. Switch, and then
Keep this state.

Next, the selection processing of the X-axis correction memory in the cam grinding device configured as described above will be described with reference to the flowchart of FIG. When a command signal indicating that machining should be started is input from the external control device 10, X-axis correction data memories for learning and correction are selected as predetermined memories as initial settings, and each parameter N (learning) is selected. The number of times and the number of times M (the number of times target accuracy has not been reached) are reset to zero (step S1), and the error maximum value detection unit 38 calculates the error at each time output by the time counter 14 (step S2). The calculation of the error at each time is performed by the X-axis position counter 20 as described above.
The current position data input from the X-axis data memory 13
Compared with the target position data of the corresponding time input from
It is obtained by finding the deviation. The process of step S2 is repeated while the cam 2 (C axis) makes one rotation (step S3). Whether or not the cam 2 (C-axis) makes one rotation is determined by whether or not a one-rotation detection signal is input from the C-axis / one-rotation detection unit 37.

When it is determined in step S3 that the cam 2 (C-axis) has made one rotation, the maximum error value detection section 38 determines the magnitude of the error (absolute value) at each time during one rotation obtained in step S2. ) Are compared, and the maximum error value in the one rotation is detected (step S4). The maximum error value detected in step S4 is stored in the maximum error value storage unit 39 in association with the value of the learning count N (step S5).

Then, the error increase / decrease judgment unit 40 compares the current error maximum value stored in the error maximum value storage unit 39 with the previous error maximum value, and determines whether or not the size of the error maximum value has increased. It is determined (step S6). If the magnitude of the maximum error value does not increase as a result of this determination, the value of the learning count N is incremented by 1 (step S
7) The learning memory determination unit 34 switches the learning X-axis correction data memory to the next memory through the learning memory selection unit 33, and the correction memory determination unit 36 determines the correction memory. Memory selection means 3
The X-axis correction data memory for correction is switched to the memory of the next order via 5 (step S8), and the process returns to step S2.

On the other hand, if the magnitude of the error maximum value increases as a result of the determination in step S6, it is determined that the error maximum value of the previous one rotation is the minimum, and the error maximum value It is determined whether the minimum value is within the target accuracy set by the target accuracy setting unit 41 (step S9). If the result of this determination is not within the target precision, the value of the target precision unachieved number M is incremented by 1 (step S10), and it is determined whether this M value is a predetermined number of times (for example, 2 times) or more. (Step S
11). As a result of this judgment, the M value is a predetermined number of times (twice).
If it is above, in order to prevent the increase of the maximum error value from being learned many times, the fact that there is an accuracy error is output (step S12), and a signal for stopping the grinding process is output (step S13). If the M value is less than the predetermined number (twice), the process proceeds to step S7 to continue learning.

On the other hand, if the result of determination in step S9 is within the target accuracy, the error increase / decrease determination unit 40
The previous learning count data and the learning end signal that minimize the maximum rotation error are output to the correction memory determining unit 36 and the learning memory determining unit 34, respectively (step S1).
4). Then, the learning memory determination unit 34, to which the learning end signal is input, switches the learning memory selection unit 33 to the off position and disconnects it from the X-axis correction data memory (step S15). Further, the correction memory determination unit 36, to which the learning number data is input, selects the X-axis correction data memory corresponding to the learning number so as to select the correction memory selecting unit 35.
Is switched (step S16). As a result, the correction value data that minimizes the error maximum value for each rotation is determined, and thereafter, the target position data is corrected using the correction value data of the X-axis correction data memory selected in step S16. The X-axis motor 6 is feedback-controlled based on the corrected target position data.

The above operation will be described more specifically with reference to FIGS. 3 and 4. For example, as shown in FIGS. 3 and 4, as the learning number increases to 0 times, 1 time, and 2 times, the maximum error value per rotation is 15.1 μm, 6.9 μm, and 3.2 μm.
It is assumed that the error maximum value per rotation increases to 4.8 μm when the number of times of learning is the third time. Target accuracy setting unit 41
Assuming that the target accuracy is set to 5 μm, the maximum error of 3.2 μm for one rotation when the number of learning is the second, clears the target accuracy. In this case, the error increase / decrease determination unit 4
0 is the number of learning times when the maximum number of errors per rotation is the minimum when the control of the learning number is completed for the third time is 2 (N
= 2), and the data is corrected by the correction memory determination unit 36.
And a learning end signal to the learning memory determination unit 34. In response to this, the learning memory selection means 33 is disconnected from the X-axis correction data memory, and
The correction memory selection means 35 selects the X-axis correction data memory B31 used for correction when the number of times of learning is the second, and thereafter does not perform learning and uses the correction value data of the X-axis correction data memory B31 to set the target position. Correct the data.

Therefore, according to the present embodiment, the subsequent correction is performed by using the correction value data when the magnitude of the maximum error value for each one rotation of the C-axis becomes the minimum, so that the error can be corrected quickly. Even if the value of the learning gain is increased to make it smaller, it is possible to prevent an increase in error thereafter, and to form the cam shape quickly and accurately. Conversely, since the machining accuracy is not impaired and the gain value can be increased, the error can be quickly reduced, and the machining time and the machining accuracy in the grinding of the cam 2 can be compatible.

Further, in this embodiment, the learning is stopped when the magnitude of the maximum error value for each rotation of the C-axis turns from a decrease to an increase, and the maximum magnitude of the error value for each rotation of the C-axis is minimized. Since the correction value data is determined as follows, unnecessary learning can be avoided and there is no fear of updating the correction value data due to continuing learning.

Further, in the present embodiment, when the magnitude of the maximum error value for each rotation of the C-axis changes from decreasing to increasing, and the minimum value of the maximum error value for each rotation is arbitrarily set. Since a predetermined signal (previous learning count data, learning end signal) is output when it is within the target accuracy,
It is possible to secure a certain processing accuracy.

In this embodiment, three X-axis correction data memories 30 to 32 are provided, but the present invention is not limited to this, and the number of X-axis correction data memories installed is two. The above is sufficient. Specifically, it will be determined in consideration of the switching speed, the miniaturization of the circuit board, the manufacturing cost, and the like.

In this embodiment, the grindstone 5 is moved forward and backward by the slider 7 with respect to the cam 2, but the present invention is not limited to this, and the grindstone is fixed and the grindstone is fixed. Needless to say, the cam may be configured to move back and forth.

[0047]

As described above, according to the cam grinding device of the first aspect of the present invention, the correction value data when the magnitude of the maximum error value for each rotation of the work is minimized is used. Since the subsequent control is performed, even if the value of the gain is increased in order to quickly reduce the error, it is possible to prevent the subsequent error from increasing and to form the cam shape quickly and accurately. In other words, since the machining accuracy is not impaired and the gain value can be large, the error can be quickly reduced, and both the machining time and the machining accuracy in the grinding process of the cam can be achieved.

According to the cam grinding apparatus of the second aspect, learning is stopped when the magnitude of the maximum error value per rotation of the work changes from decreasing to increasing, and the maximum error value per rotation of the work is stopped. Since the correction value data that minimizes the size of is determined, unnecessary learning can be avoided, and the risk of updating the correction value data due to continuing learning is eliminated.

According to the cam grinding device of the third aspect, when the magnitude of the maximum error value of the advancing / retreating movement position per rotation of the work piece changes from decreasing to increasing, the maximum error value per rotation of the work piece is increased. Since a predetermined signal (previous correction value data selection signal, learning end signal) is generated when the minimum value of is within the arbitrarily set target accuracy, it is possible to ensure a certain processing accuracy.

Further, according to the cam grinding apparatus of the fourth aspect, since the setting means is configured as described above, it is easy to determine whether or not the maximum error value per rotation of the work has changed from decreasing to increasing. Can be determined.

[Brief description of drawings]

FIG. 1 is a block diagram of a control system of a cam grinding device according to the present invention.

FIG. 2 is a flowchart of an X-axis correction memory selection process.

FIG. 3 is a chart showing a specific example for explaining the process of FIG.

FIG. 4 is a graph showing the results of the specific example of FIG.

FIG. 5 is a schematic configuration diagram of a conventional cam grinding device.

FIG. 6 is a block diagram of a control system of a conventional cam grinding device.

7 is a block diagram showing an internal configuration of a correction unit in FIG.

FIG. 8 is a graph showing the relationship between the number of times of learning by gain and the maximum error value.

[Explanation of symbols]

2 ... Cam (work) 3 ... C-axis motor 5 ... Whetstone 6 ... X-axis motor 7 ... Slider 8 ... Control device 11 ... Control unit (control means) 12 ... C-axis data memory (work target position storage means) 13 ... X Axis data memory (target advancing / retreating movement position storage means) 17 ... Pulse generator (work position detecting means) 18 ... Pulse generator (advancing / retreating movement position detecting means) 19 ... C axis position counter (work position detecting means) 20 ... X axis Position counter (advance / retreat movement position detection means) 21 ... Correction unit (correction value calculation means) 30, 31, 32 ... X-axis correction data memory (correction value storage means) 33 ... Learning memory selection means (first selection means) 34 ... learning memory determination unit (first selection unit) 35 ... correction memory selection unit (second selection unit) 36 ... correction memory determination unit (second selection unit) 37 ... C-axis single rotation detection unit (setting hand) 38) ... Maximum error value detection unit (setting unit) 39 ... Maximum error value storage unit (setting unit) 40 ... Error increase / decrease determination unit (setting unit) 41 ... Target accuracy setting unit (setting unit)

Claims (4)

[Claims] 1. A preset value is set when a desired cam shape is formed by moving a work and a grindstone for grinding the work by feedback control and moving the work in a direction perpendicular to a rotation axis of the work relatively. In a cam grinding device in which the relative forward / backward movement position between the work and the grindstone is corrected for each rotation based on the work rotational position by the gain, a work position detecting means for detecting the work rotational position, and the work and the grindstone. Between the advancing / retreating movement position detecting means for detecting the relative advancing / retreating movement position between the workpiece, the workpiece target position storing means for storing the target position of the workpiece at each elapse of a predetermined time, and the relative target between the workpiece and the grindstone. Target advancing / retreating movement position storage means for storing the advancing / retreating movement position for each elapse of a predetermined time; The target position corresponding to the current position of the work detected by the step is searched from the data stored in the work target position storage means, and the target forward / backward moving position at the same time corresponding to the searched target position of the work is determined. The target advancing / retreating position read out from the target advancing / retreating moving position storage means is compared with the current advancing / retreating moving position detected by the advancing / retreating moving position detecting means to obtain an error, and the target advancing / retreating at the corresponding time point is obtained from the obtained error. Correction value calculation means for calculating the next correction value for the moving position; a plurality of correction value storage means for storing the correction values calculated by the correction value calculation means at each corresponding time point; and the plurality of correction value storages. A first selecting a correction value storage means for storing the correction value calculated by the correction value calculation means according to a predetermined rule from among the means; Selecting means, second selecting means for selecting a correction value storage means for reading the correction value stored therein according to a predetermined rule from the plurality of correction value storage means, and a work for each rotation of the work. Setting means for outputting to the second selecting means a signal for selecting the previous correction value data when the maximum error value of the advance / retreat movement position between the grindstones changes from decrease to increase; The target advancing / retreating movement position stored in the storage means is corrected based on the correction value at the same time point stored in the correction value storage means selected by the second selecting means, and the corrected target advancing / retreating movement position is set to the target value. And a control means for controlling the forward / backward movement position between the workpiece and the grindstone, and a cam grinding device. 2. The setting means further outputs a learning end signal to the first selecting means when the magnitude of the maximum error value of the advancing / retreating movement position for each rotation of the work piece changes from decreasing to increasing. The cam grinding device according to claim 1. 3. The setting means arbitrarily sets the minimum value of the maximum error value for each rotation of the work when the maximum error value of the forward / backward movement position for each rotation of the work changes from decreasing to increasing. The cam grinding device according to claim 1 or 2, wherein a predetermined signal is generated when the target accuracy is within the target accuracy. 4. The setting means compares the present position of the workpiece detected by the workpiece position detecting means with a preset origin position to generate a workpiece 1 rotation detection signal, and a workpiece 1 rotation detection signal. For each input, the current advancing / retreating position detected by the advancing / retreating moving position detecting means is compared with the target advancing / retreating moving position at the same time stored in the target advancing / retreating moving position storage means to obtain an error at each time point. ,
A means for detecting the maximum error value for each rotation of the work by comparing the magnitudes of the errors at each time point obtained and a means for comparing the detected maximum error value for each rotation of the work and determining the increase or decrease thereof. The cam grinding device according to claim 1, 2 or 3, wherein the cam grinding device is provided.