JPS63295176A - Grinder control method - Google Patents

Abstract

PURPOSE:To enhance cylindricity of the surface to be ground by sensing the grinding forces in the normal and tangential directions, determining the grinding force as the vector resultant of the two first named grinding forces, and by controlling so that this resultant grinding force becomes constant. CONSTITUTION:When a grinder 1 performs grinding, the grinding force in the normal direction FN and that in the tangential direction FT are sensed by magnetic sensors 14a, 14b, respectively. Then the grinding force F as the vector resultant of these two, FN and FT, is calculated, and control is performed so that this value F becomes constant. Thereby the angle of deflection of the grinding wheel spindle 3a is kept constant even though the deflecting direction of this shaft varies a little, which decreases as a result the degree of taper very much to lead to enhancement of the cylindricity of the surface ground. Because the grinding force F as the resultant is controlled constant, the grinding force FN in the normal direction decreases with increasing grinding force FT in the tangential direction, and accordingly the roughness of the ground surface is held in satisfactory condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control method for a grinding machine, and more particularly, to a control method that can significantly improve cylindricity errors caused by deflection of a grindstone shaft.

[Prior art]

In general, a grinding machine consists of a cutting table whose cutting is fed by a cutting motor, a swivel table which is rotatably mounted on the cutting table so as to be rotatable around a vertical axis and which is swivel-driven by a swivel motor, and a workpiece which is mounted on the swivel table. A main shaft and a main shaft drive motor having a chuck for mounting, a grindstone table, a wheel head provided on the grindstone table, a grindstone attached to the wheel head, a grindstone drive motor that drives the wheel head, and a grindstone dresser. It is equipped with such things as

When grinding a workpiece with a grinding machine, the workpiece and grindstone are rotated, and the swivel table is rotated by an angle corresponding to the deflection angle of the grindstone shaft, thereby keeping the axis of the workpiece parallel to the axis of the grindstone. Grind while feeding the cutting table in this state.

During this grinding, as shown in FIG. 5 according to the embodiment, a horizontal normal grinding force Fs (hereinafter, normal grinding force FM ) and the tangential grinding force Ft that is mainly caused by the torque of the grindstone drive motor and is transmitted to the workpiece W via frictional force.
(hereinafter referred to as tangential grinding force FT) acts,
A grinding force F, which is a Peltor resultant force of the normal grinding force FM and the tangential grinding force FA, acts on the workpiece W.

During grinding, the diameter of the grinding wheel decreases as grinding progresses as the grinding wheel wears out and the grinding wheel is dressed many times during grinding. Normally, a constant amount of power is supplied to the grinding wheel drive motor to control its rotation speed and torque. Since grinding is carried out while holding approximately constant, the tangential grinding force FT increases as the grinding wheel diameter decreases, and the increase in the tangential grinding force FT improves grinding performance, so the normal grinding force FN increases. becomes smaller.

Since the tangential grinding force F7 controls the grinding performance, as the tangential grinding force Fa increases, the surface roughness of the ground surface increases. In addition, the normal grinding force FM greatly affects the deflection angle of the grinding wheel shaft, so if the normal grinding force FM fluctuates, the grinding surface becomes taberous, the cylindricity of the grinding surface worsens, and the grinding accuracy decreases. It turns out. However, the grindstone shaft is elastically deformed in the feed direction of the cutting table by the normal grinding force FM, and at the same time, it is also elastically deformed by the reaction force of the tangential grinding force FA.

BACKGROUND ART Conventionally, methods for controlling grinding machines have been proposed to improve the roughness and cylindricity of the ground surface.

For example, Japanese Patent Application Laid-Open No. 51-143983 describes a technique for detecting the deflection of a grindstone shaft and controlling the cutting speed via a cutting motor so that the deflection becomes constant. This is intended to maintain the normal grinding force FN constant and improve the accuracy of the cylindricity of the ground surface.

Furthermore, Japanese Patent Publication No. 53-34036 describes a technique for detecting the power supplied to a grindstone drive motor and controlling the cutting feed rate so that the power becomes a set value.

This is intended to improve the roughness of the ground surface by keeping the tangential grinding force F constant.

[Problem that the invention seeks to solve]

As mentioned above, the technique of grinding while keeping the tangential grinding force FT constant and the technique of grinding while keeping the normal grinding force F constant will be examined using FIG. 9 according to the embodiment. .

In the figure, point 0 is the center of the grinding wheel when no load is applied, point 08 is the center of the workpiece, point O0 is the center of the grinding wheel at the initial stage of grinding, and point 0a is the center of the grinding wheel when the tangential grinding force Fa is controlled constant. The center of the grindstone when the diameter becomes smaller, the point ON, is the center of the grindstone when the diameter of the grindstone becomes smaller by controlling the normal grinding force FM to be constant.

After the start of grinding, a normal grinding force F due to the cutting feed and a tangential grinding force F due to the torque of the grinding wheel act, F,
Since the grinding force F, which is the Peltor resultant force of F and F, acts,
The center of the grinding wheel is Oo, the grinding point at this time is Po, and the machining radius of the workpiece is a line segment 0°Wo.

At the start of grinding, the spindle is swiveled via the swivel table by an angle corresponding to the deflection angle of the grindstone spindle deflected in the horizontal direction by the normal grinding force FM. ) is generally adjusted and ground so that they are parallel to each other.

As the grinding progresses, the diameter of the grinding wheel becomes smaller, and as mentioned above (the magnitudes of the tangential grinding force FT and the normal grinding force F8 fluctuate, but as in the former publication mentioned above, the normal grinding force FN remains constant). When controlling so that 2, the center of the grinding wheel is O8
The state shifts to ON, the grinding point becomes Ps, and the machining radius of the workpiece becomes line segment 0.4WH. In this case, the normal grinding force FH is kept constant, but since the tangential grinding force FA increases, the deflection angle of the grindstone shaft changes toward the increasing side, and as a result, the grinding point becomes PM. And the tangential grinding force F
Since the a is significantly increased, the grinding performance increases and the roughness of the ground surface deteriorates.

On the other hand, when the tangential grinding force FT is controlled to be constant as in the latter publication, the center of the grinding wheel shifts from 0° to OF, the grinding point becomes PT, and the workpiece is machined. The radius becomes the line segment Ow WT. In this case, since the tangential grinding force F is controlled to be constant, the grinding performance is kept constant and the roughness of the ground surface is reduced. However, as shown in the figure, the normal direction grinding force F becomes smaller and the grinding force F becomes smaller, so the deflection angle of the grinding wheel shaft becomes smaller, the degree of taper of the ground surface increases, and the cylindricity of the ground surface decreases. However, the grinding point at this time is point P7.

When the normal grinding force F8 is controlled to be constant as described above, the roughness of the ground surface is not improved, and the cylindricity of the ground surface is only improved to some extent. Also, the tangential grinding force F
When A is controlled to be constant, the roughness of the ground surface is improved, but there remains a problem with the cylindricity of the ground surface.

[Means for solving problems]

A method for controlling a grinding machine according to the first invention of the present application includes detecting a normal grinding force and a tangential grinding force when grinding with a grinding machine, and detecting the normal grinding force and the tangential grinding force. The grinding force, which is the vector resultant force, is determined and controlled so that this grinding force is constant.

A method for controlling a grinding machine according to a second invention of the present application includes detecting a normal grinding force and a tangential grinding force when grinding with a grinding machine, and detecting the normal grinding force and the tangential grinding force. The grinding force, which is the vector resultant force, is determined, and the cutting speed between the grindstone and the workpiece is controlled so that the grinding force, which is the vector resultant force, is constant.

[Effect]

In the method for controlling a grinding machine according to the present invention, when grinding with the grinding machine, a normal grinding force and a tangential grinding force are respectively detected, and a vector resultant of the normal grinding force and the tangential grinding force is generated. Since the grinding force is determined and controlled so that the grinding force is constant, the deflection angle of the grindstone spindle is kept constant, although the direction of deflection of the grindstone spindle changes slightly, and as a result, the taper of the grinding surface is reduced. The degree of cylindricity becomes very small, and the cylindricity of the ground surface is greatly improved.

Further, since the grinding force as a resultant force is controlled to be constant, the normal grinding force decreases as the tangential grinding force increases, so that the roughness of the ground surface is maintained at a substantially good level.

〔Effect of the invention〕

According to the method for controlling a grinding machine according to the present invention, as explained above, the grinding force, which is the vector resultant of the normal grinding force and the tangential grinding force, is controlled to be constant, and the grinding machine is By keeping the deflection angle of the shaft constant, the grinding surface can be prevented from becoming tapered and the cylindricity of the grinding surface can be significantly improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

First, FIGS. 1 to 3 regarding the grinding machine 1 to which the present invention is applied.
Provide a brief explanation of the drawing. In FIG. 1, the -X direction is defined as the left side, the X direction is defined as the right side, the -Y direction is defined as the front, and the Y direction is defined as the rear.

Cutting table 2 that supports the spindle 4 and spindle motor 4a
The table base 10 on the bed 6 is cut by the cutting motor 5.
It is designed to be driven forward and backward in the forward and backward directions relative to the
The main shaft 4 and the main shaft motor 4a are fixed on a swivel table II placed on the cutting table 2, and the swivel table 11 is rotatable around a vertical swivel bin lla. An arm llb protruding leftward is provided at the center of the left edge of the table 11, and a screw shaft 12 screwed into a screw nut of the arm llb is disposed facing forward and backward. It is driven by a swivel drive motor 13 provided on the bracket 2a.

A grindstone table 8 supporting a wheel head 7 and a grindstone drive motor 7a is driven forward and backward relative to the bed 6 in the left-right direction by a grindstone table drive motor 9.

A workpiece W is attached to the chuck 4b of the main spindle 4, and the inner peripheral surface of the workpiece W is ground by the grindstone 3 at the tip of the grindstone shaft 3a of the wheel head 7. After the grindstone table 8 is moved to the left and the grindstone 3 is inserted into the shaft hole of the workpiece W, the cutting table 2 is moved forward or backward to perform grinding.

During the above-mentioned grinding, when the cutting table 2 is fed forward by the cutting motor 5, a grinding force in the normal direction is generated from the grinding wheel 3 to the workpiece W as a reaction force of the feeding force as shown in FIGS. 4 and 5. F, and the tangential grinding force F7 caused by the rotational torque of the grindstone 3 and transmitted through the frictional force act, and the grinding force F as a vector resultant of the normal grinding force FM and the tangential grinding force F7 is It will work.

Due to the normal grinding force FM and the tangential grinding force FT, the grinding wheel shaft 3a has a normal grinding force F, as shown in FIG.
It is elastically deformed in the opposite direction (cut feed direction) and also in the opposite direction to the tangential grinding force Fy.

Therefore, at the beginning of grinding, the swivel drive motor 13 is driven to swivel the swivel table 11, and a predetermined swivel angle θ is set so that the axial center of the workpiece W and the axial center of the grindstone 3 are parallel to each other as shown in FIG. Adjust and grind.

Next, a method of controlling the grinding machine 1 will be explained.

The method of controlling this grinding machine 1 is to detect the normal grinding force FM and the tangential grinding force Ft, respectively, and to detect the normal grinding force F
The cutting motor 5 is controlled so that the grinding force F, which is the Peltor resultant force of s and the tangential grinding force F7, is constant, and as a result, the grinding surface becomes tapered without worsening the roughness of the grinding surface. The aim is to significantly improve the cylindricity of the ground surface by suppressing this as much as possible.

In order to detect the normal grinding force Fs and the tangential grinding force Fy, as shown in FIGS.
F facing close to the front side of the outer peripheral surface of a, F facing close to the lower side of the outer peripheral surface of the detection magnetic sensor 14a and the grindstone shaft 3a
7 detection magnetic sensors 14b are provided, and detection signals from these magnetic sensors 14a and 14b are output to the control unit 15.

In this embodiment, the cutting speed is adjusted based on the detected normal grinding force FM and tangential grinding force Ft so that the grinding force F, which is the vector resultant of these forces, becomes a set value set for each workpiece W. In terms of control, the control system for the cutting motor 5 is constructed as shown in FIG. 8, for example.

That is, the control unit 15 includes a grinding force setting device 16 that sets the target value of the grinding force F, and a cutting speed setting device 17 that sets the target value of the cutting speed according to the material, shape, dimensions, etc. of the workpiece W. FM detection magnetic sensor 14a and F
Detection signals are received from the T detection magnetic sensor 14b, respectively, and F = [(FN)"+ (F7)"] "" (
D calculation calculation A calculation circuit 18 that calculates the grinding force F, a subtracter 19 that subtracts the output signal of the calculation circuit 18 from the output signal of the grinding force setter 16, and a predetermined coefficient multiplied by the output signal of the subtractor 19. It is equipped with a coefficient multiplier 20 and an adder 21 that adds the output signal of the cutting speed setting device 17 and the output signal of the coefficient multiplier 20, and the output signal of the adder 21 is sent to the drive circuit 5.
The current is amplified by the drive circuit 5a and controlled by the drive circuit 5a.
Voltage power is supplied to the cutting motor 5.

Therefore, when the actual grinding force F obtained from the detected value of the normal grinding force Fs and the detected value of the tangential grinding force F7 is smaller than the grinding force set value, the output signal of the subtractor 19 becomes a signal of 10. , a signal proportional thereto is added to the output signal of the cutting speed setting device 17 by the adder 21, so the cutting speed is corrected to increase, the cutting speed increases, the normal grinding force F8 increases, and the actual grinding The force F approaches the grinding force setting value.

When the actual grinding force F is larger than the grinding force setting value, the cutting speed is corrected to the decreasing side, contrary to the above.

To explain the operation when controlling the cutting speed so that the actual grinding force F becomes the set value as described above, the 9th
In the figure, the point OF is the center of the grinding wheel when the grinding wheel diameter is reduced by controlling the grinding force F to be constant as described above, and the grinding point at this time is PF, and the workpiece W
The machining radius of is the line segments O and W. On the other hand, when the normal grinding force F is controlled to be constant as described above, the machining radius of the workpiece W is the line segment 0°W, 4, and the tangential grinding force F is constant. The machining radius of the workpiece W when controlled so as to become the line segment 01Wt.

As is clear from FIG. 9, when the grinding force F is controlled to be constant, the machining radius 0° WF of the workpiece W is the smallest. This is because the machining radius of the workpiece W at the initial stage of grinding is the line segment OwWo, so when the grinding force F is controlled constant, the degree of taper of the grinding surface is the smallest, that is, the cylindricity of the grinding surface is the most. It shows that it is high.

Since the deflection angle of the grindstone shaft 3a depends on the magnitude of the grinding force F, by controlling the grinding force F to be constant, the deflection angle of the grindstone shaft 3a can be kept constant. However, even if the grinding force F is controlled constant, the normal direction grinding force F,
decreases to some extent, so the deflection angle (θ in Fig. 4) of the grinding wheel shaft 3a in the horizontal plane decreases by the decrease in the normal grinding force FM, and a slight taper of the grinding surface can be avoided. do not have.

In the case of the conventional technology that controls the normal direction grinding force F9 to be constant,
Although the normal grinding force FN is kept constant, the tangential grinding force F□ increases as the grinding wheel diameter decreases, causing the grinding wheel shaft 3
The deflection angle of a increases, and as a result, the degree of taper of the ground surface increases.

In the case of the conventional technology that controls the tangential grinding force Ft constant,
As the grinding wheel diameter decreases, the normal direction grinding force F decreases, and the grinding force F becomes smaller, and the deflection angle of the grindstone shaft 3a decreases significantly compared to the deflection angle at the start of grinding, and the workpiece W. The parallelism between the axial center and the axial center of the grindstone 3 is disrupted, and as a result, the grinding surface becomes tapered.

When the grinding force F is controlled to be constant in this way, the deflection angle of the grindstone shaft 3a is kept constant, the degree of taper of the grinding surface is extremely reduced, and the cylindricity of the grinding surface is significantly improved. become.

Furthermore, the effect of controlling the cutting speed so that the grinding force F is constant will be explained.

Assuming that the grindstone drive motor 7a is driven at a set rotation speed and a set power, as the grindstone diameter decreases, the tangential grinding force Fa increases and the grinding performance improves. As a result, the normal grinding force F tends to decrease, but if grinding is performed without reducing the normal grinding force FH, the grinding efficiency will improve but the roughness of the ground surface will deteriorate. .

However, in the case of this embodiment, since the cutting speed is controlled so that the grinding force F as a vector resultant of the normal grinding force F2 and the tangential grinding force FT is constant, as the grinding wheel diameter decreases, the tangential grinding force F7 When the cutting speed increases, the normal grinding force FM is reduced by lowering the cutting speed.

As a result, the roughness of the ground surface is maintained substantially well.

Next, a modification of the control system and detection system of the grinding machine 1 will be described.

(11 As shown in Fig. 10, the control unit 1
5A receives detection signals from the FH detection magnetic sensor 14a and the FT detection magnetic sensor 14b and converts them into A/D.
An A/D converter 22 for conversion, an operation panel 23 for inputting and setting grinding conditions, an input/output ink face 24 for receiving signals from the A/D converter 22, and an input/output ink face 2.
A CPU 25 (central processing unit) connected to the CPU 25 via a data bus or the like, and a ROM 26 (read-only memory) and a RAM 27 connected to the CPU 25 via a data bus or the like, respectively.
(random access memory), and from the input/output ink face 24 are a main shaft motor drive circuit 28, a cutting motor drive circuit 29, a swivel drive motor drive circuit 30, a grindstone drive motor drive circuit 31, and a grindstone table drive motor drive. Control signals are output to the circuits 32 and 32, respectively.

The ROM 26 stores control programs for controlling each motor 4a, 5, 7a, 9, and 13 based on setting signals from the operation panel 23, as well as detection signals from the F, detection magnetic sensor 14a, and Ft detection magnetic sensor 14b. A control program for reading and calculating the grinding force F as a vector resultant force as described above and controlling the cutting motor 5 so that the grinding force F becomes constant is stored in advance.

The control routine consists of steps such as reading a detection signal, calculating the grinding force F, and outputting a control signal to the cutting motor drive circuit 29.

It is also possible to control both the cutting motor 5 and the grindstone drive motor 7a so that the grinding force F is constant.

In that case, even if the grinding wheel diameter decreases as grinding progresses, it is possible to maintain the normal grinding force FN and tangential grinding force FT at substantially the same values as in the initial stage of grinding, and to perform ideal grinding. .

Further, even if the grindstone drive motor 7a is not controlled as described above, it is also possible to control the swivel angle of the swivel table 11 in response to the decrease in the normal grinding force F8.

(2) Instead of the magnetic sensors 14a and 14b, various detection devices such as an electric micrometer, an air micrometer, and an optical micrometer can be used.

In addition, the normal direction grinding force FM detection means may be configured as shown in FIG. 11 or FIG. 12, for example.

That is, in the case shown in FIG. 11, the grinding wheel shaft 3a is adjusted based on the rotational speed signal of the cutting motor 5 (detected by the rotational speed sensor) and the diameter signal of the grinding inner peripheral surface measured by the in-process gauge 32. The amount of deflection is determined, and the grinding force FM in the normal direction is determined from the amount of deflection. In addition, the one shown in FIG. 12 detects the diameters of the grinding inner peripheral surface of the workpiece W at two locations in the axial direction using a pair of in-process gauges 32, determines the deflection angle of the grindstone shaft 3a from the difference in diameter, and calculates the deflection angle of the grindstone shaft 3a. The normal direction grinding force F is determined from the corner. In addition, code 1 in the figure
5B is a control unit similar to that shown in FIG.

On the other hand, the tangential grinding force Fa converts the voltage of the electric power supplied to the grindstone drive motor 7a into a potential transformer.
In addition, the current is detected by a current transformer, the rotation speed of the grindstone drive motor 7a is determined by a rotation speed sensor, etc., and the tangential grinding force Fy is determined based on the detected voltage, the detected current, and the detected rotation speed. It's okay.

[Brief explanation of drawings]

The drawings relate to an embodiment of the present invention, and FIG. 1 is a plan view of the grinding machine, FIG. 2 is a front view of the same, FIG. 3 is a side view of the same, and FIG. 5 is an explanatory diagram showing the normal grinding force, tangential grinding force, and grinding force acting on the workpiece from the grindstone; FIG. 6 is F, the magnetic sensor for detection, and F7. Fig. 7 is a plan view of the main parts, Fig. 8 is a configuration diagram of the control system for the cutting motor, and Fig. 9 shows each control system including the conventional technology. An explanatory diagram of the machining radius when controlling with
Figure 10 is a configuration diagram of an example of the control system of the entire grinding machine, Figure 11
FIG. 12 is a configuration diagram showing an example of a normal direction grinding force detection means. 1. Grinding machine, 3. Grinding wheel, 5. Cutting motor,
F8...Normal direction grinding force, F...Tangential direction grinding force, F...Grinding force, 14a...Magnetic sensor for 2M detection, 14b...Magnetic sensor for Ft detection, 15
・15A-15B...Control unit, I6
...Grinding force setting device, 32...In-process gauge, W
··work. Patent applicant Mazda Motor Corporation Figure 1 Figure 4 Figure 5 Figure 9

Claims (2)

[Claims] (1) When grinding with a grinder, detect the grinding force in the normal direction and the grinding force in the tangential direction, and find the grinding force that is the vector resultant of the normal grinding force and the tangential grinding force, A method for controlling a grinding machine characterized by controlling the grinding force so that it is constant. (2) When grinding with a grinder, detect the grinding force in the normal direction and the grinding force in the tangential direction, and calculate the grinding force that is the vector resultant of the normal grinding force and the tangential grinding force, A method for controlling a grinding machine characterized by controlling the cutting speed between a grindstone and a workpiece so that the grinding force, which is the vector resultant force, is constant.