JPH09318511A - Method and apparatus for measuring compressive strength of foundry sand - Google Patents

Abstract

(57) Abstract: When pressing molding sand in a test cylinder by a servo cylinder to create a test piece, the pressing force of the servo cylinder is kept constant. A first load cell 7 is attached to a tip of a piston rod 4 of a servo cylinder 3 to detect an actual pressing force of the servo cylinder 3 when a test piece S is created, and the detection result is used as a current applied to a servo motor 5. The output torque of the motor 5 is controlled by feedback.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an apparatus for automatically measuring the compressive strength of foundry sand.

[0002]

The present applicants have developed a device for automatically measuring the compressive strength of foundry sand using a servo cylinder,
Applying for utility model registration (Actual Kaihei 5-71752)
issue). In this device, as a first step, the molding sand in the test cylinder is compressed by a servo cylinder at a predetermined pressure to create a test piece, and as a second step, the test piece is increased by a predetermined ratio by the same servo cylinder. The compression strength (coercive pressure) is measured by pressurizing to the breaking limit. In this case, the pressing force of the servo cylinder is adjusted (maintained at a predetermined pressure) and controlled (controlled to draw a predetermined boost curve). This is done by adjusting and controlling the output torque of the servo motor, and further adjusting the output torque of the servo motor,
The control is performed by adjusting and controlling the current applied to the servo motor.

[0003]

By the way, recently, the drive of the servomotor is changing from the conventional analog system to the digital system, and the size of the servomotor itself is also decreasing. As a result, it is difficult to use the servo cylinder for measuring the compressive strength of foundry sand. More specifically, when the molding sand in the test cylinder is compressed by the servo cylinder to create a test piece, when a current of a predetermined value is applied to the servo motor, the output torque of the servo motor is determined by the rotation angle of the motor. It fluctuates greatly depending on. This fluctuation range is as much as ± 10 to 15% of the average output torque, and the pressing force of the servo cylinder also fluctuates within the same range. As a result, the compressive strength (coercive pressure) of the prepared test piece varies, and the compressive strength of the foundry sand cannot be accurately measured.

[0004]

In order to solve the above problems, the present invention attaches a load cell to the piston rod of a servo cylinder to detect the actual pressing force of the cylinder when a test piece is prepared. Is fed back to the current applied to the servomotor to control the output torque of the motor, so that the pressing force of the cylinder is kept constant. Then, a pressing force is applied to the thus-prepared test piece to measure the compressive strength (coercive force) immediately before the fracture.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment. FIG. 1 is an overall configuration diagram of a foundry sand compressive strength measuring device used for carrying out the method of the present invention, FIG.
3 is an operation explanatory view of the apparatus. In the figure, a servo cylinder 3 is fixed upward to a horizontal support member 2 provided at an intermediate level of the portal frame 1. The piston rod 4 of the cylinder 3 is rotated forward and backward by the servo motor 5,
The support member 2 is pierced to move up and down. Reference numeral 6 is an encoder for detecting the rotation speed of the servo motor. A first load cell 7 for detecting the pressing force of the rod 4 is fixed to the upper end of the piston rod 4, and a disc-shaped pressure plate 9 is fixed to the upper end of the first load cell 7. The pressing rod 8 is erected vertically. The rotation speed of the servo motor 5 is proportional to the ascending / descending distance of the pressure plate 9. Therefore, the ascending / descending distance of the pressure plate 9 can be controlled by controlling the rotation speed. A test cylinder 11 oriented in the vertical direction is provided at a position directly above the piston rod 4 in the servo cylinder 3 via a horizontal support member 12, and the pressure plate 9 moves up and down in the test cylinder 11. Has been Above the test tube 11, guide rods 12, 12 forming a pair in front and back are horizontally arranged with both ends thereof being supported by the side wall of the portal frame 1.

Between the guide rods 12 and 12, a first surface plate 14 having guide tubes 13 and 13 on both sides is slidably fitted on the guide rods 12 and 12. They are arranged together. The first surface plate 14 is guided by the guide rods 12 and 12 by a driving means (not shown) so as to reciprocate in the horizontal direction. The first
The bottom of the surface plate 14 is formed into a flat surface capable of closing the upper end opening of the test tube 11. To the left of the first surface plate 14, there is arranged a second load cell 15 whose bottom surface is formed so as to be opposed to the upper end opening of the test tube 11 with a predetermined space therebetween, and the second load cell 15 is supported. It is integrated with the first surface plate 14 via the member 16. The chute 17 is located on the top of the gate mount 1 just above the test tube 11.
Is provided, and the molding sand is introduced into the test tube 11 through the chute 17.

FIG. 4 is a block diagram of a control circuit in the servo cylinder 3. In the figure, a central processing unit 18 including a plurality of microcomputers and the like is connected with the encoder 6, the first load cell 7 and the second load cell 15 on the input side of a control signal,
On the output side of the control signal, a rotation speed converter 19 that controls the frequency of the servo motor 5 based on the signal from the encoder 6, an output torque converter 20 that controls the current value of the servo motor 5, and the above. Panel 21 for displaying the compressive strength of foundry sand based on the detected load of the second load cell 15.
Is connected. The central processing unit 18 stores the reaching target pressing force of the servo cylinder 3 and the target boosting curve up to this, and the load detected by the target boosting curve and the first load cell, that is, the servo cylinder 3 is stored. The actual pressing force of is compared momentarily, so that the detected value reaches the target pressing force along the target boost curve,
A signal is output to the output torque converter 20, and the current value applied to the servo motor 5 is controlled momentarily based on this signal.

The case of measuring the compressive strength of foundry sand with the above-mentioned device will be described. The piston rod 4 of the servo cylinder 3 is contracted to position the pressure plate 9 at a predetermined level in the test cylinder 11 ( (State of FIG. 1). The level of the pressure plate 9 at this time is positioned so that the height of the test piece after compression molding becomes a predetermined dimension (for example, 50 mmH) based on the compactability value of the molding sand measured in advance. In such a state, first, the foundry sand is loaded into the test tube 11 through the chute 17 in a heap. Secondly, the driving means (not shown) is operated to move the first surface plate 14 to the left, and the upper end opening of the test tube 11 is closed by the bottom surface of the first surface plate 14.
At this time, excess sand on the upper end of the test cylinder 11 is scraped off by the first surface plate 14. In this state, thirdly, when the servomotor 5 is normally driven at a predetermined rotation speed, the pressure plate 9 rises so that the molding sand in the test tube 11 and the first pressure plate 9 move.
Compressed between the bottom surface of the surface plate 14 and a predetermined height (for example,
A test piece S of 50 mm) is prepared (state of FIG. 2). During this period, the load applied to the first load cell 7 is input to the central processing unit 18 every moment in the form of an electric signal and compared with the stored target boosting curve. Then, a signal is output to the output torque converter 20 so that the detected value follows the target boost curve, and the applied current value of the servomotor 5, that is, the output torque of the motor 5 is controlled. Then, when the detected value reaches the target pressing force, the rotation of the motor 5 is stopped.

Fourthly, the first surface plate 14 is moved to the right, and secondly.
The bottom surface of the load cell 15 is located directly above the test tube 11. Then, fifth, when the servomotor 5 is again driven in the normal rotation at a predetermined rotation speed and output torque, the test piece S is pushed up by the pressure plate 9 and pulled out from the test tube 11. Then, just before the top surface of the test piece S comes into contact with the bottom surface of the second load cell 15, the rotation speed of the servomotor 5 is switched to a low speed by a command from the rotation speed converter 19, and the pressure plate 9 rises gently ( (State of FIG. 3). After that, sixthly, the servo motor 5 is forwardly driven at a predetermined rotation speed to raise the pressure plate 9 at a predetermined speed (for example, 0.2 mm / s) to compress the test piece S. And test piece S
The load of the second load cell 15 just before the breakage is calculated by the central processing unit 18 and displayed on the compressive strength display panel 21. The compressive strength (coercive pressure) of the test piece S is
It is determined by dividing the above load by the cross-sectional area of the test piece S.

[0010]

Other Embodiments In the above embodiment, the compressive strength (coercive pressure) of the test piece S is measured by the second load cell 15, but instead of this, the second load cell 15 is simply a platen, and
You may make it measure with the load cell 7. Generally, since the pressing force of the servo cylinder at the time of making the test piece is 200 to 300 kg, the first load cell 7 having a rated capacity of about 500 kg is used. On the other hand, the test piece is compressed (compressive strength)
Since the pressing force when breaking for measurement is generally 20-40kg, the rated capacity of the second load cell 15 is 50-100kg.
I am using something of a degree. Therefore, the first load cell 7
When measuring the compressive strength (coercive pressure) of the test piece, the measurement accuracy is slightly deteriorated, but the cost of the apparatus can be reduced by reducing one expensive load cell.

[0011]

As is apparent from the above description, the present invention is an apparatus for automatically measuring the compressive strength of foundry sand, in which a test piece is prepared by compressing foundry sand by a cylinder in a test tube. The pressing force of the cylinder is detected by the first load cell, and the detection result is fed back to the current applied to the servomotor, that is, the output torque of the motor. As a result, the pressing force of the cylinder is kept constant, and the compression strength (coercive pressure) of the prepared test piece does not vary, and the compressive strength (coercive pressure) of the foundry sand can be accurately measured.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

2 to 3 are operation explanatory views of the device of the present invention.

FIG. 4 is a block diagram of an electric control circuit of the present invention.

[Explanation of symbols]

 3 Servo Cylinder 4 Piston Rod 5 Servo Motor 7 1st Load Cell 8 Push Rod 9 Pressure Plate 11 Test Cylinder 14 1st Surface Plate 15 2nd Load Cell 20 Output Torque Transducer 21 Compressive Strength Display Panel S Specimen

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Kato 16-2, Kahara, Ishida, Shinshiro-shi, Aichi (72) Inventor Zensumi Senda 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Corporation

Claims (3)

[Claims] 1. A load cell is attached to a piston rod of a servo cylinder, the pressing force when pressing the molding sand thrown into the test cylinder by the load cell is detected by the load cell, and the detection result is applied to a servo motor. To produce a test piece while controlling the output of the servo motor by feeding back the current, and then applying a pressing force to the test piece to measure the compressive strength immediately before the fracture of the casting sand. Method of measuring compressive strength. 2. A servo cylinder 3 arranged upward and having a first load cell 7 fixed to the tip of a piston rod 4.
A pressing rod 8 erected on the first load cell 7, and a disk-shaped pressure plate 9 fixed to the tip of the pressing rod 8.
And a test cylinder 11 disposed directly above the piston rod 4 in which the pressure plate 9 is moved up and down, and a test cylinder 11 disposed above the test cylinder 11 so as to be traversable and at the bottom. A first surface plate 14 having a flat surface capable of closing the upper end opening of 11, a horizontal surface supported by the first surface plate 14 so as to be traversable above the test tube 11, and an upper end opening of the test tube 11 at the bottom. A second load cell 1 having a flat surface which is opposed to and spaced at a predetermined interval.
5, an output torque converter 20 for controlling the output torque of the servo motor 5 in the cylinder 3, and a current value applied to the servo motor 5 according to the load detected by the first load cell 7 is changed every moment. A casting for controlling the output torque converter 20 so as to allow the panel to display the compressive strength of the test piece S based on the load detected by the second load cell 15. Sand compression strength measuring device. 3. A servo cylinder 3 arranged upward and having a first load cell 7 fixed to the tip of a piston rod 4.
A pressing rod 8 erected on the first load cell 7, and a disk-shaped pressure plate 9 fixed to the tip of the pressing rod 8.
And a test cylinder 11 disposed directly above the piston rod 4 in which the pressure plate 9 is moved up and down, and a test cylinder 11 disposed above the test cylinder 11 so as to be traversable and at the bottom. A first surface plate 14 having a flat surface capable of closing the upper end opening of 11, a horizontal surface supported by the first surface plate 14 so as to be traversable above the test tube 11, and an upper end opening of the test tube 11 at the bottom. A second platen having a flat surface that can face each other at a predetermined interval, an output torque converter 20 for controlling the output torque of the servomotor 5 in the cylinder 3, and a load detected by the first load cell 7. Accordingly, the control means for controlling the output torque converter 20 so as to change the current value applied to the servomotor 5 every moment, and the compressive strength of the test piece S based on the load detected by the first load cell 7. Show That a panel 21, the compressive strength measuring device of the casting sand, comprising the.