JP3785717B2 - Clamping device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a clamping device for holding a workpiece to be machined, and more particularly to a clamping device that is preferably applied to planar processing of a thin plate workpiece using a milling machine.
[0002]
[Prior art]
For example, when grinding a mounting hole in a camshaft housing (work) of an automobile engine, the position of the work support and the pressure of the clamp for holding the work are set to a certain value. It has been proposed to adjust the position of the workpiece support base and the clamp pressure of the workpiece based on the result of measuring the dimension after machining (see, for example, JP-A-7-164,216).
[0003]
As a result, the camshaft housing, which is a workpiece, is ground in a state substantially close to the state assembled to the cylinder head.
[0004]
[Problems to be solved by the invention]
However, the technique disclosed in the above publication cannot be applied as it is to plane machining by a milling machine of thin plate parts such as a control valve body among engine assembly parts. This is because the cutter and the clamp of the milling machine interfere with each other.
[0005]
Therefore, when milling the thin control valve body W, as shown in FIG. 8, the control valve body W is clamped at three locations M1, M2 and M3, and vibration during machining is prevented. Supporting the intended natural clamps N1 to N4 from the back side of the processed surface has been studied.
[0006]
However, when the flatness of the workpiece W after milling is measured at 20 points HE1 to HE20 shown in FIG. 9, it is supported by natural clamps N1 to N4 as shown by the flatness contours in FIG. The result was that the center of the workpiece W was recessed downwards.
[0007]
The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a clamping device capable of obtaining a workpiece with high flatness when milling a thin plate workpiece. And
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the clamping device of the present invention according to claim 1 is a clamping device for holding the workpiece when milling a thin plate workpiece, and at least a position near the center of the workpiece in the longitudinal direction. And a plurality of main clamps for gripping the front and back of the workpiece at the same position, and a plurality of natural clamps arranged around the gripping position of the main clamp and supporting the back surface of the work surface of the workpiece. To do.
[0009]
When a thin plate-like workpiece is milled, a concave distortion occurs in the machining surface due to the clamping stress or cutter stress in addition to the residual stress of the workpiece itself. In the clamping device according to claim 1, the main clamp is at least in the longitudinal direction of the workpiece. In addition to gripping the front and back of the workpiece at the same position near the center, the natural clamp is placed around the gripping position of the main clamp and supports the back side of the work surface of the workpiece, so that processing distortion due to cutter stress is reduced. Therefore, the flatness of the workpiece can be increased.
[0010]
According to a second aspect of the present invention, at least one of the grip portions of the main clamp has a point support structure. By using the main clamp as a point support, distortion due to the main clamp stress can be suppressed. In this case, it is more preferable that both of the grip portions of the main clamp are point-supported. However, even if only one of the grip portions is point-supported, a considerable distortion suppressing effect can be obtained.
[0011]
The clamp device according to claim 3, wherein each of the natural clamps further includes a natural clamp pressure setting unit that adjusts a support pressure with respect to the back surface of the workpiece, and a pressure sensor that detects the support pressure. And Since there is a correlation between the natural clamp pressure and flatness, a workpiece with higher flatness can be obtained by adjusting the natural clamp pressure. In particular, since the clamp pressures of the natural clamps can be adjusted individually, the work can have a high flatness throughout.
[0012]
The clamp device according to claim 4 is characterized in that each of the natural clamps further includes an operation abnormality sensor. By detecting an abnormal operation of the natural clamp, it is possible to prevent a decrease in flatness due to an unexpected natural clamp pressure acting.
[0013]
Furthermore, the clamping device according to claim 5 is a flatness measuring unit that measures the flatness of the workpiece, and a natural clamp pressure calculating unit that calculates a support pressure of the natural clamp based on a measurement result by the flatness measuring unit. The natural clamp pressure setting means is controlled by an output signal from the natural clamp pressure calculation means.
[0014]
In the clamp device according to the fifth aspect, the flatness of the workpiece processed by the flatness measuring means is measured, and the measurement result is taken into the natural clamp pressure calculating means to calculate an appropriate support pressure for the natural clamp. Then, the obtained appropriate support pressure is output to the natural clamp pressure setting means, and the next workpiece is supported by this support pressure. Thus, a workpiece with higher flatness can be obtained by feedback control.
[0015]
【The invention's effect】
According to the clamp apparatus of Claim 1, since the setting position of a main clamp and a natural clamp is appropriate, the process distortion by cutter stress can be suppressed and the flatness of a workpiece | work can be raised.
[0016]
According to the clamp device of the second aspect, since the main clamp is performed with point support, distortion due to the main clamp stress can be suppressed, and a workpiece with high flatness can be obtained.
[0017]
According to the clamp device of the third aspect, since the natural clamp pressure can be adjusted, a workpiece with higher flatness can be obtained. In particular, since the clamp pressures of the natural clamps can be adjusted individually, the work can have a high flatness throughout.
[0018]
According to the clamp device of the fourth aspect, since the abnormal operation of the natural clamp is detected, it is possible to prevent the flatness from being lowered due to an unexpected natural clamp pressure.
[0019]
According to the clamp device of the fifth aspect, the flatness of the workpiece machined by the flatness measuring means is measured, and the next clamping is performed by feedback-controlling the measurement result. Can be obtained at a rate.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the mechanical system of the clamping device of this embodiment will be described.
1 is a plan view showing the setting positions of a main clamp and a natural clamp in the present embodiment, FIG. 2 is a plan view showing a clamp device of the present embodiment, FIG. 3 is a side view of the same, and FIG. 4 is a main view related to the same embodiment. The principal part side view which shows a clamp, FIG. 5 is a side view which shows the natural clamp which concerns on the same embodiment.
[0021]
The clamping device of the present embodiment holds the workpiece W when milling one main surface (surface side in the drawing) of a substantially rectangular and thin plate-like control valve body W as shown in FIGS. It is the clamp device for doing.
[0022]
As shown in FIG. 1 and FIG. 2, this clamp device has three main clamps 10 and six natural clamps 20, and the main clamps 10 are ends in the longitudinal direction of a rectangular workpiece W. Three positions are arranged at positions MS1 to MS3 from the center to the center. On the other hand, the natural clamp 20 is arrange | positioned in the periphery NS1-NS6 of the position MS1-MS3 in which the main clamp 10 was provided. For example, natural clamps NS1, NS2, NS3 are arranged around the main clamp MS1, natural clamps NS4, NS5 are arranged around the main clamp MS2, and natural clamps NS5, NS6 are arranged around the main clamp MS3. Has been.
[0023]
As shown in FIG. 4, each main clamp 10 grips the front and back surfaces of the workpiece W. The sheet 19 abuts on the back surface of the workpiece W, while the swing arm 13 abuts on the surface of the workpiece W. The tip of the swing arm 13 is formed in a curved surface so as to be point supported (see the point support 15). The swing arm 13 is pivotally supported at the tip of the plunger 11, and a link 12 is provided at the center of the swing arm 13. Therefore, when the plunger 11 moves in and out, the swing arm 13 is opened and closed by the link 1 to grip and release the workpiece W. Reference numeral 14 denotes an input port for applying a fluid pressure for locking the swing arm 13.
[0024]
On the other hand, as shown in FIG. 3, the natural clamp 20 abuts on and supports the back surface of the workpiece W. As shown in FIG. Is attached. The pad 24 comes into contact with the back surface of the workpiece W. The plunger 23 moves in and out by the inflow of fluid from the plunger pressure input port 21 and is locked by the inflow of fluid from the lock pressure input port. The natural clamp 20 has a built-in pressure sensor 26 that detects the clamp pressure of the plunger 23 and feeds it back to a natural clamp pressure setting section described later. Furthermore, the natural clamp 20 is provided with an operation abnormality sensor 25 for detecting an operation abnormality of the plunger 23, and feeds back to the control unit of the milling machine described above.
[0025]
In FIG. 2, positioning bars 31 and 32 for positioning the workpiece W are provided at one edge of the workpiece W.
[0026]
Next, the control system of the clamping device of this embodiment will be described.
FIG. 6 is a block diagram showing the configuration of the control system of the embodiment of the clamping device of the present invention, and FIG. 7 is a flowchart showing the control procedure of the block diagram shown in FIG.
[0027]
First, for the main clamp 10, a signal from the milling machine control unit 107 is input to the main clamp drive unit 101, whereby the plunger 11 operates to open and close the main clamp unit 102.
[0028]
On the other hand, the clamping device of this embodiment includes a three-dimensional shape measuring unit 109 for measuring the flatness of the workpiece W, and the measurement result is output to the flatness determining unit 110. The flatness determination unit 110 obtains the difference in flatness between the natural clamp positions NS1 to NS6 with reference to the flatness of the main clamp positions MS1 to MS3 shown in FIG. This determination result is output to the natural clamp pressure calculation unit 111.
[0029]
The natural clamp pressure calculation unit 111 calculates a natural clamp pressure based on the following calculation formula (1), and the result is output to the natural clamp pressure setting unit 108 of each natural clamp 20.
[0030]
[Expression 1]
δMAX (cantilever) = WL3 / 3EI (1)
Here, W represents a load, L represents an overhang distance, E represents a longitudinal elastic modulus, I represents a section modulus, and is represented by I = bh3 / 12 (where b: width, h: effective height). L (i), E (i), and I (i) are eigenvalues for each clamp position. From the above equation (1), W (i) = δMAX · 3EI / L3.
[0031]
For example, the pressure setting value of the natural clamp NS1 shown in FIG. 1 is obtained by a value obtained by subtracting HE4 corresponding to the main clamp position MS1 from HE1 corresponding to NS1 at the flatness measurement position shown in FIG. Next, a load W (i) is obtained from W (i) = δMAX · 3EI / L3 which is a modified expression of the above equation (1), and a natural clamp pressure corresponding to this load is calculated.
[0032]
The natural clamp pressure setting unit 108 takes in the detection value from the pressure sensor 26 built in the natural clamp 20 and outputs a command signal to the natural clamp drive unit 105 based on the command signal from the natural clamp pressure calculation unit 111 described above. Then, the natural clamp portion 104, that is, the plunger 23 is operated. Thereby, the support pressure of the natural clamp is feedback controlled to an appropriate value.
[0033]
Note that a detection signal from the natural clamp operation abnormality sensor 25 provided in the natural clamp 20 is output to the milling machine control unit 107, and is displayed on the milling machine control unit 107 when there is an abnormality.
[0034]
Next, the operation will be described.
As shown in FIG. 7, the flatness of the workpiece after milling is obtained by the three-dimensional shape measuring unit 109 (step 1), and the flatness is judged by the flatness determining unit 110 (step 2). If the measured flatness satisfies the standard, the process proceeds to step 7. If the measured flatness does not satisfy the standard, the process proceeds to step 6, and the natural clamp pressure calculation unit 111 calculates the natural clamp pressure according to the procedure described above. Then, the natural clamp pressure setting unit 108 sets an appropriate natural clamp pressure based on this (step 6).
[0035]
In parallel with this, the workpiece W is positioned (step 4), and the main clamp 10 is locked (step 5).
[0036]
In step 7, each natural clamp 20 set to an appropriate pressure is actuated and locked (step 8). At this time, the output signal of the operation abnormality sensor 25 is monitored (step 9), and if an abnormality occurs, an abnormality is displayed on the milling machine control unit 107 (step 10).
[0037]
Since the setting by the main clamp 10 and the natural clamp 20 is completed, the surface of the workpiece W is milled in step 11. When this milling is completed, each natural clamp 20 is first released (step 12), and each main clamp 10 is released (step 13). When the holding of the workpiece W is released, the workpiece W is moved (step 14), the flatness of the milling process is measured by the three-dimensional shape measuring unit 109 (step 15), and the process returns to step 1.
[0038]
When the thin plate-like workpiece W described above is milled, a concave distortion occurs in the machining surface due to the clamp stress or the cutter stress in addition to the residual stress of the workpiece itself. However, in the clamping device of this embodiment, the main clamp 10 is the workpiece. In addition to gripping the front and back of the workpiece W at least at a position near the center of the longitudinal direction of W, a natural clamp 20 is arranged around the gripping position of the main clamp 10 to support the back surface of the processed surface of the workpiece W. Therefore, the processing distortion due to the cutter stress can be suppressed, and the flatness of the workpiece W can be increased.
[0039]
Moreover, in the clamp apparatus of this embodiment, since the main clamp 10 is point-supported, distortion due to main clamp stress can be suppressed. Moreover, since each natural clamp 20 can adjust the support pressure with respect to the back surface of the workpiece | work W, it can obtain a workpiece | work with higher flatness. This is because there is a correlation between the natural clamp pressure and the flatness. In particular, since the clamp pressure of each of the natural clamps 20 can be adjusted individually, the work W can have a high flatness throughout.
[0040]
Moreover, in the clamp apparatus of this embodiment, since the operation abnormality sensor is provided in each natural clamp 20, by detecting the operation abnormality of each natural clamp 20, it is because an unexpected natural clamp pressure acts. A decrease in flatness can be prevented in advance.
[0041]
Furthermore, the clamping device of the present embodiment measures the flatness of the workpiece W processed by the three-dimensional shape measuring unit 109, takes this measurement result into the natural clamp pressure calculating unit 111, and performs feedback control. A degree of work can be obtained.
[0042]
The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a plan view showing setting positions of a main clamp and a natural clamp in an embodiment of a clamping device of the present invention.
FIG. 2 is a plan view showing an embodiment of the clamping device of the present invention.
FIG. 3 is a side view showing an embodiment of the clamping device of the present invention.
FIG. 4 is a side view of a main part showing a main clamp according to an embodiment of a clamp device of the present invention.
FIG. 5 is a side view showing a natural clamp according to an embodiment of the clamping device of the present invention.
FIG. 6 is a block diagram showing a configuration of a control system of the embodiment of the clamping device of the present invention.
7 is a flowchart showing a control procedure of the block diagram shown in FIG. 6. FIG.
FIG. 8 is a plan view showing setting positions of a main clamp and a natural clamp of a clamping device to be referred to.
FIG. 9 is a plan view showing an example of a measurement position for measuring flatness.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Main clamp 15 ... Point support part 20 ... Natural clamp 25 ... Operation abnormality sensor 26 ... Pressure sensor 108 ... Natural clamp pressure setting means 109 ... Three-dimensional shape measurement part (flatness measurement means)
111 ... Natural clamp pressure calculation unit (natural clamp pressure calculation means)
W ... Work MS1-MS3 ... Main clamp position NS1-NS6 ... Natural clamp position

Claims (5)

In a clamping device that holds the workpiece when milling a thin plate workpiece,
A plurality of main clamps for gripping the front and back of the workpiece at the same position at least near the center of the workpiece in the longitudinal direction;
A clamp apparatus comprising: a plurality of natural clamps arranged around a gripping position of the main clamp and supporting a back surface of a processed surface of the workpiece. The clamping device according to claim 1, wherein at least one of the grip portions of the main clamp has a point support structure. 3. The clamp device according to claim 1, wherein each of the natural clamps further includes a natural clamp pressure setting unit that adjusts a support pressure with respect to a back surface of the workpiece, and a pressure sensor that detects the support pressure. . The clamp device according to claim 1, wherein each of the natural clamps further includes an operation abnormality sensor. A flatness measuring means for measuring the flatness of the workpiece; and a natural clamp pressure calculating means for calculating a support pressure of the natural clamp based on a measurement result by the flatness measuring means,
The clamp apparatus according to claim 3 or 4, wherein the natural clamp pressure setting means is controlled by an output signal from the natural clamp pressure calculation means.

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