JPH0655300A - Method for measuring press load - Google Patents

Abstract

PURPOSE:To make the longitudinal direction of the device and the pressure sensor so as not to be made larger by introducing the press load by summing resistance values of strain gages provided at each column. CONSTITUTION:For example, in a press device having four numbers of columns, four numbers of columns are respectively provided with each load measuring part 9, strain gages are attached in the inside in the longitudinal direction so that the longitudinal strain of the column 3 in the die clamping time is changed to the electric resistance value corresponding to the strain. When the press device is started, and the strain is generated in four numbers of columns 3, and the value of strain gages attached to each column is changed and the potential difference is generated. Due to the size of potential difference, the press load is obtained. Further, if the press load measuring method is assembled in the press device having plural numbers of columns, the total device can be avoided from being made larger caused by the assembly of the press load measuring method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press machine, and more particularly to a method for measuring the load of a press machine having a plurality of columns.

[0002]

2. Description of the Related Art Among press machines having a plurality of columns,
The following description will be given by taking a press machine having four columns as an example.

FIG. 1 shows a pressing device having four columns according to the prior art. Upper and lower fixed bolsters 1,
Between the two, four columns 3 are fastened, and the moving bolsters 4 are slidably arranged on the columns 3. Upper and lower press dies 5, 6 are placed between the movable bolster 4 and the upper bolster. Above the lower bolster 2, a pressure detection sensor 7 for measuring the press load, a pressure generating mechanism 8,
Are arranged. The pressure generating mechanism 8 transfers the lower press die 6 in the direction of the upper press die 5, together with the moving bolster 4, and abuts and clamps the die. The pressure generating mechanism 8 may be any mechanism such as a hydraulic cylinder system, a screw feed system, a toggle system, or a combination thereof. The pressure detection sensor 7 detects the reaction force of the mold clamping force generated by the pressure generation mechanism 8 and measures the press load. However, the pressure generation mechanism 8 and the pressure detection sensor 7 need to be arranged in series with respect to the direction of the mold clamping force to be detected, which has a drawback that the press device has to be large in the longitudinal direction. You Further, there is a drawback that the pressure detection sensor 7 also becomes large in size in accordance with an increase in the press pressure.

[0004]

The problems to be solved by the present invention are that the press device incorporating the conventional press load measuring method must be increased in the longitudinal direction of the device, and the press pressure increases. That is, the pressure sensor also becomes large in size.

[0005]

[Means for Solving the Problems] In order to solve the problems,
In the present invention, the press load is derived by the sum of the resistance values of the strain gauges provided for each column.

[0006]

[Embodiment 1] FIG. 2 shows a press device incorporating the method for measuring a press load device of the present invention. In this embodiment, a press device having four columns will be described below as an example.

Between the upper and lower fixed bolsters 1, 2 and 4,
The column 3 of the book is fastened, and the moving bolster 4,
It is slidably arranged on the column 3. Between the moving bolster 4 and the upper bolster 1, the upper and lower press die devices 5,
6 is placed.

On the lower bolster 2, there is a pressure generating mechanism 8,
Are arranged, and the lower press die 6 is moved in the direction of the upper press die 5, together with the moving bolster 4, and abutting and clamping are performed. The pressure generating mechanism 8 may be any mechanism such as a hydraulic cylinder system, a screw feed system, a toggle system, or a combination thereof.

A load measuring section 9 is provided on each of the four columns 3, and strain gauges R1 to R4 are provided inside the columns to measure the strain in the longitudinal direction of the columns 3 when the mold is clamped. It is attached in the longitudinal direction of the column so that the electric resistance value changes. Details of the strain gauge mounting portion on the column 3 according to the first embodiment are shown in FIGS.

FIG. 4 shows a Wheatstone bridge electric circuit for converting changes in resistance values of strain gauges R1 to R4, which are respectively attached to the four columns 3, into press loads.

R in the figure represents a fixed resistance. In the initial state, R1 = R2 = R3 = R4 and R1 + R2 + R3 + R4 = R, and a potential difference E1 is applied between A1 and B1 in advance. Therefore, in the initial state, there is no potential difference between C1 and D1.

When the press machine is activated and the four columns 3 are distorted, a strain gauge R1 attached to each column
~ R4, resistance value changes, R1 + R2 + R3 + R4 ≠ R,
And a potential difference e1 is generated between C1 and D1. The pressing load is determined by the magnitude of the potential difference e1.

[0013]

Second Embodiment Next, a second embodiment of the present invention will be described with reference to the drawings. The second embodiment is a method capable of compensating for the measured tension difference due to thermal expansion of the column itself when molding is performed using a mold in a high temperature state such as an injection mold press device or a transfer mold device.
The structure of the pressing mechanism is the same as that of the pressing device shown in FIG. 2 in the first embodiment, and the description of the mechanism is omitted.

The details of the load measuring portion on the column 3 according to the second embodiment are shown in FIG. Each of the four columns 3 has R1 to R4 in the longitudinal direction and R11 to R1 at right angles to them.
Two strain gauges are attached for each set of 4 and 4.

R1 to R4 are for detecting the longitudinal strain of the column 3 during mold clamping as in the first embodiment, while R11 to R14 are due to the thermal expansion of the column 3. It is for detecting the distortion. FIG. 6 shows a Wheatstone bridge electric circuit for converting the strain gauges R1 to R4 and R11 to R14 into resistance value press loads. R,
Is a fixed resistance.

In the initial state, R1 = R2 = R3 = R4 = R11 = R
12 = R13 = R14, and R1 + R2 + R3 + R4 = R11 + R12
+ R13 + R14 = R, and A2, B2 in advance, E2 between
Is applied. Therefore, in the initial state, there is no potential difference between C2 and D2.

When the press machine is activated and the four columns 3 are distorted in the longitudinal direction, the resistance values of the strain gauges R1 to R4 mounted in the longitudinal direction of each column change, and R
1 + R2 + R3 + R4 ≠ R, and the potential difference e between C2 and D2
2, occurs. The press load is obtained from the magnitude of the potential difference e2. When thermal expansion occurs in the column 3, the strain due to the thermal expansion is added to the strain due to the press load, and the resistance value changes.

However, in this embodiment, since the strain gauges R11 to R14 are attached to each column in the direction perpendicular to the longitudinal direction of the column, they detect strain due to thermal expansion.
R1 to R4, resistance change due to thermal expansion and R11 to R14,
The amount of change in resistance is the same, and R11 to R14 in FIG.
As shown in, it is canceled on the bridge circuit. Therefore, as a result, an accurate press load can be obtained without being affected by heat.

Two sets of strain gauges for detecting longitudinal strain and two strain gauges for detecting thermal expansion are attached as shown in FIG. 7, and the press load is determined by the bridge circuit shown in FIG. In this case, since the doubled potential difference is generated under the strain amount under the same conditions as those in FIGS. 5, 6 and 6, the press load detection accuracy is doubled.

[0020]

[Effects of the Invention] Even if the press load measuring method according to the present invention is incorporated in a press device having a plurality of columns, it is possible to avoid an increase in size of the entire device due to the incorporation of the press load measuring method.

[0021]

[Brief description of drawings]

FIG. 1 Press machine by conventional press load measuring method

FIG. 2 is a press device according to a press load measuring method of the present invention.

FIG. 3 is a detailed view of a load measuring unit according to the first embodiment.

FIG. 4 is a Wheatstone bridge electric circuit according to the first embodiment.

FIG. 5 is a detailed view of a load measuring unit according to a second embodiment.

FIG. 6 is a Wheatstone bridge electric circuit according to a second embodiment.

[Fig. 7] Detailed view of double-precision load measuring unit

FIG. 8 Double precision Wheatstone bridge electric circuit

[Explanation of sign]

 1, upper bolster 2, lower bolster 3, column 4, moving bolster 5, upper mold 6, lower mold 7, pressure detection sensor 8, pressure generation mechanism 9, load measuring unit R, fixed resistances R1 to R34, strain gauge

Claims (3)

[Claims] 1. A method for measuring a press load, wherein in a press device having a plurality of columns, the press load is derived from a total resistance value of strain gauges provided for each column. 2. In a press device having a plurality of columns, a strain gauge is provided in each column in a vertical direction and a horizontal direction with respect to a load, and a Wheatstone bridge electric circuit is provided in order to compensate a temperature change of the press device. Method for measuring press load characterized by deriving the press load 3. In a press device having a plurality of columns, a total of four strain gauges are provided for each column in the vertical and horizontal directions with respect to the load, and a total of four strain gauges are provided to compensate for temperature changes in the press device. In order to measure the press load with double precision in the Wheatstone bridge electric circuit