JP6861027B2 - Grinding device - Google Patents

Description

The present invention relates to a grinding device for grinding a workpiece such as a cam ring, and particularly to an improvement in processing accuracy thereof.

Conventionally, there has been known a method for grinding the inner surface of a work by rotating the grindstone at a high speed while supplying grinding coolant while rotating the work at a low speed or moving the grindstone shaft to grind the inner surface of the work.

Although it is not internal grinding, for example, a cam grinding method is known in which the supply amount of grinding coolant is changed according to the feeding speed of the grindstone to the cam (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 64-71660

By the way, when an elliptical through hole is provided on the inner surface of the work, there is a difference in taper accuracy of the inner surface between the major axis portion and the minor axis portion. Specifically, it is known that the inner diameter on the grindstone shaft side tends to be larger and the inner diameter on the opposite side tends to be smaller on the long diameter side, but taper hardly occurs on the short diameter side.

Specifically, as shown in FIG. 4 showing the change in the coordinate curve of the foam creation axis (X axis) and the load applied to the electric motor for the grindstone axis, when the supply amount of the grinding coolant is constant, the ellipse is formed. During machining of the inner surface, the load applied to the electric motor for the grindstone shaft fluctuates in conjunction with the shape phase. That is, the load is high in the long diameter portion A and low in the short diameter portion B. It is considered that this is caused by the difference in the machining load due to the difference in the amount of escape (discharge) of the grinding coolant. That is, in the long diameter portion, the gap between the outer circumference of the grindstone and the inner surface of the work is narrow, the escape route of the grinding coolant is narrowed, and the grinding coolant bites between the outer circumference of the grindstone and the inner surface of the work, which becomes a machining load and is the thinnest grindstone. It is easy to bend the shaft and cause a taper on the machined surface. It was found that the fluctuation width h of the load was about 13% in the semi-express process of the grindstone shaft power and about 10% in the finishing process, which were not negligible values.

Furthermore, in order to ensure grinding efficiency, a certain amount of grinding coolant is required for cooling and cutting waste discharge.

On the other hand, as in Patent Document 1, there is a method of increasing or decreasing the amount of grinding coolant according to the feeding speed, but it cannot be applied, for example, when the feeding speed is constant.

In addition, since the inner surface is ground, it is necessary to insert the grindstone into the work, and in order to maintain the thickness of the grindstone, the outer diameter of the grindstone shaft cannot be made too large, and it can withstand load fluctuations. Therefore, the shape of the grindstone shaft cannot be increased.

The present invention has been made in view of this point, and an object of the present invention is to improve the taper accuracy of the inner surface of the work at low cost without relying on the rigidity of the grindstone shaft in non-perfect circular inner surface grinding. is there.

In order to achieve the above object, in the present invention, the supply amount of the grinding coolant is changed in response to the load fluctuation.

Specifically, the first invention presupposes a method of grinding the inner surface of a work by rotating a grindstone at a high speed while supplying a grinding coolant to grind the inner surface of the work.

Then, the supply amount of the grinding coolant is adjusted according to the size of the gap between the outer peripheral surface of the grindstone and the inner surface of the work.

That is, when the gap between the outer circumference of the grindstone and the inner surface of the work is narrowed, the escape route of the grinding coolant is narrowed, and the grinding coolant bites between the outer circumference of the grindstone and the inner surface of the work, which becomes a machining load and causes the grindstone and the grindstone shaft. It is easily deformed to cause a taper on the machined surface. However, according to the above configuration, when the gap is small, the amount of grinding coolant is reduced to reduce the load, and conversely, when the gap is large, the amount of grinding coolant is not reduced so that the load is made uniform as a whole. Can be done. As a result, the machined surface is less likely to be tapered.

In the second invention, in the internal grinding method of the work under the above premise,
When the elliptical through hole of the work is internally ground, the amount of grinding coolant when the grindstone is on the minor axis side of the ellipse is larger than the amount of grinding coolant when the grindstone is on the major axis side of the ellipse. ..

That is, on the long-diameter side where the gap between the outer circumference of the grindstone and the inner surface of the work is narrow, the escape route of the grinding coolant becomes narrower, and the grinding coolant bites between the outer circumference of the grindstone and the inner surface of the work, which becomes a machining load and becomes a machining load. The grindstone shaft is deformed, and the machined surface is likely to be tapered. However, according to the above configuration, the load can be made uniform as a whole by reducing the amount of grinding coolant on the long diameter side to reduce the load, and conversely, by not reducing the amount of grinding coolant on the short diameter side. it can. As a result, the machined surface is less likely to be tapered.

In the third invention, in the internal grinding method of the work under the above premise,
The amount of the grinding coolant is reduced when the value of the electric motor for the grindstone that rotates the rotating shaft of the grindstone is large, and the amount of the grinding coolant is increased when the value of the power meter is small. ..

According to the above configuration, when the value of the wattmeter of the electric motor for the grindstone is large, the reaction force due to the grinding coolant is reduced by reducing the amount of grinding coolant, and conversely, when the value of the wattmeter is small, the value of the grinding coolant is reduced. By increasing the amount, the magnitude of the reaction force due to the grinding coolant can be made uniform as much as possible, and the taper on the inner surface of the work can be prevented from occurring.

In the fourth invention, in the third invention,
The feedback control is used to adjust the change in the value of the wattmeter and the timing of the increase / decrease in the amount of the grinding coolant.

That is, if the grinding coolant is increased or decreased according to the change of the wattmeter, the response will be deviated due to the influence of the path to the nozzle and the like. According to the above configuration, by returning the degree of deviation to the control device and performing feedback control, it is possible to appropriately adjust the change in the value of the wattmeter and the timing of the increase / decrease in the amount of grinding coolant.

The fifth invention is based on the premise of a grinding device that grinds the inner surface of a workpiece by rotating a grindstone at high speed while supplying grinding coolant.
The above grinding device
The grindstone shaft that rotates the grindstone and
An electric motor for the grindstone that rotates the grindstone shaft,
The work rotation axis that rotates the above work and the work rotation axis
A nozzle that discharges the grinding coolant to the inner surface of the work, and
A coolant circuit that sends the grinding coolant to the nozzle,
A supply control valve provided in the coolant circuit to control the supply of grinding coolant,
An increase control valve provided in the coolant circuit to increase the supply amount of grinding coolant,
The coolant pump unit provided in the coolant circuit and
It is equipped with the electric motor for the grindstone and the control device for controlling the pump unit for the coolant.
The above control device
While opening the supply control valve to supply the grinding coolant,
The control valve for increasing the amount is opened to increase the supply amount of the grinding coolant.

That is, when the gap between the outer circumference of the grindstone and the inner surface of the work is narrowed, the escape route of the grinding coolant is narrowed, and the grinding coolant bites between the outer circumference of the grindstone and the inner surface of the work, which becomes a machining load and causes the grindstone and the grindstone shaft. It is easily deformed to cause a taper on the machined surface. However, according to the above configuration, when the gap is small, the increase control valve is closed to reduce the amount of grinding coolant to reduce the load, and conversely, when the gap is large, the increase control valve is opened to reduce the amount of grinding coolant. By not reducing the load, the load can be made evenly as a whole. As a result, the machined surface is less likely to be tapered.

In the sixth invention, in the fifth invention,
When grinding the elliptical through hole of the work on the inner surface, the control device utilizes the information on the positional relationship between the grindstone shaft and the work rotation shaft, and increases the amount when the grindstone is on the major axis side of the ellipse. The control valve is closed, and when it is on the minor axis side of the ellipse, the increase control valve is opened to increase the amount of grinding coolant.

According to the above configuration, the control device reads the information on the positional relationship between the grindstone shaft and the work rotation shaft, and when the grindstone is on the major axis side of the ellipse, the reaction force due to the grinding coolant is reduced by reducing the amount of grinding coolant. On the contrary, when it is on the minor axis side of the ellipse, the amount of grinding coolant can be increased to make the magnitude of the reaction force due to the grinding coolant as uniform as possible and prevent the inner surface of the work from tapering. ..

In the seventh invention, in the fifth or sixth invention,
The control device reads the value of the wattmeter of the electric motor for the grindstone, closes the wattmeter control valve when the value of the wattmeter increases, and closes the wattmeter control valve when the value of the wattmeter decreases. Is configured to open.

According to the above configuration, the control device reads the power meter of the electric motor for the grindstone, and when the value is large, the reaction force due to the grinding coolant is reduced by reducing the amount of grinding coolant, and conversely, the value of the power meter is increased. When it becomes smaller, the amount of the grinding coolant can be increased to make the magnitude of the reaction force due to the grinding coolant as uniform as possible and prevent the inner surface of the work from being tapered.

In the eighth invention, in the seventh invention,
The control device is configured to adjust the change in the value of the wattmeter and the opening / closing timing of the increase control valve by feedback control.

That is, if the grinding coolant is increased or decreased according to the change of the wattmeter, the response will be deviated due to the influence of the path to the nozzle and the like. According to the above configuration, by returning the degree of deviation to the control device and performing feedback control, it is possible to appropriately adjust the change in the value of the wattmeter and the timing of the increase / decrease in the amount of grinding coolant.

As described above, according to the present invention, the amount of grinding coolant supplied according to the size of the gap between the outer peripheral surface of the grindstone and the inner surface of the work, the position of the grindstone, or the position of the wattmeter of the electric motor for the grindstone. By adjusting the above, the taper accuracy of the inner surface of the work can be improved at low cost without relying on the rigidity of the grindstone shaft in the non-perfect circular inner surface grinding.

It is a graph which shows the fluctuation of the load of the grindstone shaft in each process in the inner surface grinding method of a work. It is a perspective view which shows the grindstone shaft insertion process. It is a perspective view which shows the state during cutting. It is a figure which shows the coolant circuit. It is a graph which shows the state of the change of the load applied to the coordinate curve of the X-axis and the electric motor for a grindstone axis.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

-Structure of grinding equipment-
FIG. 2A is a perspective view showing an outline of a grinding device such as an NC machine tool according to an embodiment of the present invention. This grinding device rotates the work W at a low speed and supplies grinding coolant at a high speed. The inner surface of the work W is ground by rotating with. The grinding device includes a grindstone shaft 2 that rotates the grindstone 1 and an electric motor 3 for the grindstone that rotates the grindstone shaft 2. The grinding device includes a work rotation shaft 4 that rotates the work W at a low speed. The work shaft 4 is rotated by a work shaft rotating means 5 such as an electric motor. The electric motor 3 for the grindstone, the work shaft rotating means 5, and the like can be controlled by the control device 6.

Further, the grinding device includes a nozzle 11 for discharging the grinding coolant 10 to the inner surface of the work W, and a coolant circuit 12 for feeding the grinding coolant 10 to the nozzle 11. As shown in FIG. 3, the coolant circuit 12 is provided with a coolant pump unit 13, and the coolant pump unit 13 is provided with a discharge pump 13a and a pump electric motor 13b for driving the discharge pump. There is. The discharge pump 13a is controlled by the control device 6. The coolant circuit 12 is provided with a check valve 15, a first solenoid valve 16 as a supply control valve, and a second solenoid valve 17 as an increase control valve. For example, a fixed throttle valve 18 is provided between the first solenoid valve 16 and the nozzle 11. The first solenoid valve 16 serves to deliver the grinding coolant from the discharge pump 13a at the open position and stop it at the time of closing. The second solenoid valve 17 serves to stop the grinding coolant sent from the first solenoid valve 16 at the time of closing and to send the grinding coolant to the nozzle 11 at the time of opening without passing through the throttle valve 18. The first solenoid valve 16 and the second solenoid valve 17 are operated by the control device 6. The grinding coolant 10 is stored in the coolant tank 19.

With this configuration, the control device 6 opens the first solenoid valve 16 and the second solenoid valve 17 to increase the supply amount of the grinding coolant 10, opens the first solenoid valve 16, and opens the second solenoid valve 17. By closing, the supply amount of the grinding coolant 10 is reduced, that is, it is returned to a predetermined amount.

-Work inner surface grinding method-
Next, the inner surface grinding method of the work W according to the present embodiment will be described. In this inner surface grinding method, the inner surface of the work W is ground by rotating the grindstone 1 at a high speed while supplying the grinding coolant 10 while rotating the work W at a low speed. Then, the supply amount of the grinding coolant 10 is adjusted according to the size of the gap between the outer peripheral surface of the grindstone 1 and the inner surface of the work W.

Specifically, as shown in FIG. 1, first, in step S01, as shown in FIG. 2A, the grindstone shaft 2 is inserted into the inner surface side of the work W. At this time, the first solenoid valve 16 and the second solenoid valve 17 are in the closed state. The work W also rotates slowly, as seen in the X-axis coordinate curve. Since grinding has not started, no load is applied to the grindstone shaft 2.

Next, in the semi-express step of step S02, the first solenoid valve 16 is opened, and the second solenoid valve 17 is opened and closed in accordance with the rotation of the X-axis. For example, the amount of coolant discharged is 90 L / min when the second solenoid valve 17 is opened, and 45 L / min when the second solenoid valve 17 is closed. In this semi-express process, contact detection between the grindstone 1 and the inner surface of the work W is performed. As will be described in detail later, also at this time, by controlling the opening and closing of the second solenoid valve 17, the non-uniform resistance due to the grinding coolant 10 can be eliminated, and the accuracy of contact detection is greatly improved.

Next, the process proceeds to the rough process of step S03. In step S03, both the first solenoid valve 16 and the second solenoid valve 17 are maintained in an open state, and priority is given to efficient cutting. In this case, the maximum amount of the grinding coolant 10 is always ejected from the nozzle 11, the grindstone 1 is cooled, and the grinding debris is efficiently collected. At this time, as described with reference to FIG. 4, the inner diameter of the grindstone shaft 2 side tends to be large and the inner diameter of the opposite side tends to be small on the long diameter portion A side, but the taper hardly occurs on the short diameter portion B side. ..

Next, in the finishing step of step S04, the second solenoid valve 17 is opened and closed according to the movement of the X-axis. Since the depth of cut itself is smaller than that in the rough process, the load itself of the grindstone shaft 2 is reduced, but the fluctuation of the load is reduced by the opening / closing control of the second solenoid valve 17. That is, using the information on the positional relationship between the grindstone shaft 2 and the work rotation shaft 4, when the grindstone 1 is on the major axis side of the ellipse, the second solenoid valve 17 is closed to obtain a normal amount of grinding coolant, and the ellipse is short. Increase the amount of grinding coolant 10 when it is on the radial side. By cutting in this state, the taper generated on the major axis side in the rough process is reduced.

Next, in the spark-out step of step S05, the second solenoid valve 17 is similarly opened and closed according to the movement of the X-axis. By controlling the opening and closing of the second solenoid valve 17, load fluctuations are reduced. That is, when the second solenoid valve 17 is continuously opened, it is possible to prevent the load on the grindstone shaft 2 from being significantly increased or decreased according to the movement of the X-axis as in the case without the SOL2 control shown in FIG. It is considerably reduced as with SOL2 control.

Finally, in step S06, the grindstone shaft 2 is taken out from the inner surface of the work W.

As described above, in the present embodiment, when the elliptical through hole of the work W is internally ground, when the grindstone 1 is on the minor axis side of the ellipse rather than the amount of the grinding coolant 10 when the grindstone 1 is on the major axis side of the ellipse. By increasing the amount of the grinding coolant 10, the taper is suppressed on the major axis side, and the taper accuracy of the inner surface of the work W can be improved inexpensively without relying on the rigidity of the grindstone 1 and the grindstone shaft 2 in the non-perfect circular inner surface grinding. Can be done. Therefore, the elliptical through hole of the work W can be formed into a straight hole without a taper at any position on the inner surface.

For example, when the discharge rate of the grinding coolant was constant at 90 L / min, the taper on the major axis side was 8 μm at a height of 49 mm, but by suppressing the discharge rate to 45 L / min on the major axis side, It was reduced to 4 μm. This was not significantly different from the inclination of the grindstone shaft 2 in grinding with the normal grindstone 1.

-Modification example-
Although not shown, the modified example of the embodiment of the present invention differs from the above embodiment in that the control method of the second solenoid valve 17 is different. In this modification, the same parts as those in FIGS. 1 to 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

The control device 6 takes in the value of the wattmeter 3a of the electric motor 3 for the grindstone, closes the second solenoid valve 17 when the value of the wattmeter 3a becomes large, and closes the second solenoid valve 17 when the value of the wattmeter 3a becomes small. It is configured to open the solenoid valve 17.

Actually, as in the above embodiment, the second solenoid valve 17 is opened on the short diameter side to increase the amount of grinding coolant, and the second solenoid valve is closed on the long diameter side to reduce the amount of grinding coolant (place). Return to quantitative).

In this case, if the opening / closing control of the second solenoid valve 17 is performed according to the change of the power meter 3a, the response is deviated due to the influence of the path to the nozzle 11. Therefore, it is preferable to adjust the timing of the change in the value of the wattmeter and the timing of the increase / decrease in the amount of the grinding coolant 10 by returning the degree of deviation to the control device 6 and performing feedback control (learning).

In this modified example, it is particularly effective for a deformed cross section that is not a regular ellipse. Further, in this modification, the number of resetting items can be reduced each time the model number of the work W is changed. Further, since simple control is required, it can be applied to a grinding machine other than an NC machine tool. Further, even when the height of the work W fluctuates, the value of the power meter 3a fluctuates, so that the amount of the grinding coolant 10 may be increased or decreased accordingly.

(Other embodiments)
The present invention may have the following configuration with respect to the above embodiment.

That is, in the above embodiment, the inner surface shape of the work W is elliptical, but the present invention is not limited to this, and any one having a non-uniform inner surface such as the inner surface of the cam ring can be applied.

It should be noted that the above embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its applications and applications.

1 Whetstone
2 Whetstone shaft
3 Electric motor for grindstone
3a wattmeter
4 Work rotation axis
5 Work shaft rotating means
6 Control device
10 Grinding coolant
11 nozzle
12 Coolant circuit
13 Coolant pump unit
13a Discharge pump
13b Electric motor for pump
15 Check valve
16 1st solenoid valve (supply control valve)
17 Second solenoid valve (control valve for increasing volume)
18 throttle valve
19 Coolant tank

Claims (3)

In a grinding machine that grinds the inner surface of a workpiece by rotating a grindstone at high speed while supplying grinding coolant.
The grindstone shaft that rotates the grindstone and
An electric motor for the grindstone that rotates the grindstone shaft,
The work rotation axis that rotates the above work and the work rotation axis
A nozzle that discharges the grinding coolant to the inner surface of the work, and
A coolant circuit that sends the grinding coolant to the nozzle,
A supply control valve provided in the coolant circuit to control the supply of grinding coolant,
An increase control valve provided in the coolant circuit to increase the supply amount of grinding coolant,
The coolant pump unit provided in the coolant circuit and
It is equipped with the electric motor for the grindstone and the control device for controlling the pump unit for the coolant.
The above control device
While opening the supply control valve to supply the grinding coolant,
It is configured to open the control valve for increasing the amount to increase the supply amount of the grinding coolant.
When grinding the elliptical through hole of the work on the inner surface, the control device utilizes the information on the positional relationship between the grindstone shaft and the work rotation shaft, and increases the amount when the grindstone is on the major axis side of the ellipse. A grinding device characterized in that the control valve for grinding is closed and the control valve for increasing the amount is opened when the ellipse is on the minor axis side to increase the amount of grinding coolant. In a grinding machine that grinds the inner surface of a workpiece by rotating a grindstone at high speed while supplying grinding coolant.
The grindstone shaft that rotates the grindstone and
An electric motor for the grindstone that rotates the grindstone shaft,
The work rotation axis that rotates the above work and the work rotation axis
A nozzle that discharges the grinding coolant to the inner surface of the work, and
A coolant circuit that sends the grinding coolant to the nozzle,
A supply control valve provided in the coolant circuit to control the supply of grinding coolant,
An increase control valve provided in the coolant circuit to increase the supply amount of grinding coolant,
The coolant pump unit provided in the coolant circuit and
It is equipped with the electric motor for the grindstone and the control device for controlling the pump unit for the coolant.
The above control device
While opening the supply control valve to supply the grinding coolant,
It is configured to open the control valve for increasing the amount to increase the supply amount of the grinding coolant.
The control device reads the value of the wattmeter of the electric motor for the grindstone, closes the wattmeter control valve when the value of the wattmeter increases, and closes the wattmeter control valve when the value of the wattmeter decreases. A grinding machine characterized in that it is configured to open. In the grinding apparatus according to claim 2,
The control device is a grinding device characterized in that it is configured to adjust a change in the value of the wattmeter and an opening / closing timing of the increase control valve by feedback control.

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