JPS6279925A - Method of deciding press fit force in press work - Google Patents

Abstract

PURPOSE:To enable a correct decision to be performed, by successively storing in memory measuring data of a load cell at every predetermined time and taking out from the memory the data retroactive by a predetermind time, when the data reaches a predetermined extreme preset value, to obtain measured press fit force. CONSTITUTION:When the first part is forced to be pressed into the second part, repeatedly measured data, obtained by a load cell provided in a press fit tool, show a riseup in a press fit start, become a fixed value in a stage pressing the part and rapidly rise by the extreme. Accordingly, the extreme preset value MX and a retroactively sampling number (n) can be previously set in accordance with a work objective part. And a device, repeatedly sampling the measured data of tthe load cell in a predetermined interval to be successively stored in memory and detecting some sampling data to reach the extreme preset value MX while taking out the preceding data from the memory by the predetermined sampling number (n), performs a decision of the result being compared with preset upper and lower limit values.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a press force determination method that is carried out for product quality inspection and control when a press-formed part is press-fitted into another part. .

[Conventional technology]

When press-fitting a first part into a second part by press working, it is necessary to inspect whether the press force between the parts in the finished product is within an appropriate range. It is desirable that the inspection be a 100% inspection. Therefore, a load cell is installed on the press-fitting tool side of the press machine.
By measuring the load applied to the press-fitting tool with this load cell, the press-in force is measured for each press operation,
We are making it possible to conduct 100% inspection. Note that the reaction force of the pressing force is applied to the press-fitting tool of the press machine when the tool press-fits the part, so measuring the force applied to the press-fitting tool is equivalent to measuring the pressing force of the part. Become.

By the way, the pressing force between the parts in the product is not the force during the press process, but the force at the end of the press process. Therefore, a problem arises in that it is necessary to determine which data truly indicates the pressing force in the finished product from among the measurement data obtained moment by moment from the load cell during press working. In the press-fitting process, the cylinder is attached at the end of pressurization, so in order to determine the data indicating the true press force between the parts mentioned above, it is necessary to exclude the load cell measurement data in the cylinder-attached state. This has not traditionally been easy to do.

Figure 5 is a partial cross-sectional side view schematically illustrating a conventional press force determination method, in which 1 is a first part (for example, a parallel pin), 2 is a second part, 6 is a die, and 4 is a press machine. This is a press-fitting tool. Part 1 is press-fitted into part 2 by applying pressure with a press-fitting tool 4. The load cell 5 is pressed. A limit switch 6 is fixed corresponding to a predetermined stroke position of the press-fitting tool 4, and when the press-fitting tool 4 reaches this position, the limit switch 6 is activated. The limit switch 6 is activated at a position immediately before the shell-attached state to generate an output signal, and the load cell measurement data until the limit switch activation output signal is generated is used as data indicating the true press force. Since the measurement data after the limit switch is activated is for the case where the limit switch is activated, it is canceled.

[Problem that the invention seeks to solve]

However, in the conventional method as described above, a considerable degree of precision is required for positioning the limit switch, so it is difficult to accurately determine the press force force.

Particularly when the depth of press-fitting a part is shallow, it is difficult to set the switch activation position to the position at the time of press-fitting, and the switch is often set to the position before press-fitting, thereby selecting measurement data before press-fitting. The problem arises. In that case, even though the press force of the product is within the specified limits, the press force is insufficient and the product is treated as defective. In addition, even if the limit switch is positioned accurately, the press speed is high and there is a time delay in the output of the mint switch, so by the time the limit switch activation output signal is generated, the body is already in position. A problem arises in that the load cell measurement data in the state where the body is mounted is selected. To solve this problem, it would be better to install the limit switch somewhat higher in consideration of the output delay, but it is difficult to position it accurately, and as mentioned above, the press-fit depth is limited. In the case of shallow objects, there is a risk that measurement data before press-fitting may be selected.

[Means for solving problems]

In order to solve the above-mentioned problems, the press force determination method in press working according to the present invention is characterized by roughly dividing into the following three steps.

■Measurement data from a load cell installed to measure the load applied to the press-fitting tool of a press machine is repeatedly sampled during press processing and sequentially stored in memory.

(2) Detecting that the measurement data at the sampling timing reaches a predetermined set value.

retrieving the data from the memory, and using the retrieved measurement data as data indicating the pressing force of the part.

[Action and effect of invention]

FIG. 1 shows an example of the load cell measurement data that is repeatedly sampled and sequentially stored in the memory in the first step. As can be seen from the figure, changes in load cell measurement data (pressing force) during press-fitting have approximately three characteristics. The first step is when the press-fitting force starts to rise as the part begins to be press-fitted. The next stage is when the part is being pushed in, and at this stage it shows almost true pressing force, and the measured data curve is almost flat.

The final stage is the stage where the load cell measurement data rapidly increases due to the loading. In the memory, load cell measurement data that changes in this way is sampled over time and is sequentially stored at each address.

In the second step, it is detected that the load cell measurement data at the sampling timing has reached a predetermined set value. This may be done by checking stored data at each address in the memory, or by checking measured data sampled in real time. The above-mentioned detection is performed by setting this set value to an arbitrary value in advance and comparing it with the load cell measurement data at each sampling timing. By performing this detection, it is possible to know which address in the memory corresponds to the sampling link timing of the measurement data corresponding to the body setting value.

In the third step, measurement data that is a predetermined number of samples (number of addresses) before the sampling timing at which the set value for barreling is reached is retrieved from the memory, and is used as data indicating the true press force. This predetermined number of samples n is set in advance to an arbitrary value. In the case of FIG. 1, the sampling timing at which the set value with the barrel is reached is set as rOJ1, and the measurement data at the sampling timing "-nJ" which is n samples * number of days earlier than that is taken out from the memory as press-in force data.

It should be noted that ideal values for the set value with the shell and the number of samples n to be traced back are known in advance depending on the part to be processed, so it is sufficient to set these ideal values.

Therefore, according to the present invention, data indicating accurate press force between parts can be obtained by excluding measurement data in the mounted state. Moreover, since no limit switch or the like is used, mechanical positioning is not required, and there are no problems such as errors caused by operation time delays, etc., and various other excellent effects are achieved.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram schematically showing the hardware configuration of the determination device used to carry out the present invention, and the load cell 5 is attached to the press-fitting tool of the press machine as described above.

The judgment output of the load cell 5 is analog/
The signal is supplied to a digital converter 8 and converted into digital measurement data. The digitally converted measurement data is C
The measured data is sampled under the control of a PU (central processing unit) 9 and stored in a predetermined measurement data memory area in a RAM (random access memory) 10. 11 is a ROM (read only memory) including a program memory and the like.

Reference numerals 12 to 16 are setting devices for setting various numerical data, and are comprised of, for example, digit switches. The shell material value setter 12 is for setting the above-mentioned shell material setting value,
Data MX indicating the set trunk attachment value is output. The backward sample number setter 16 is for setting the number of samples n to be traced back. Upper limit setter 14 and lower limit setter 15
are for setting the upper limit value UR and lower limit value LR of the acceptance criteria of the press-fit measurement value, respectively, for quality inspection. The data acquisition time setter 16 is for variably setting the time interval for sampling measurement data of the load cell 5.

The measurement/setting mode changeover switch 17 is a switch for selectively switching the operation mode of the CPU 9 to either the measurement mode or the setting mode. The start switch 18 is a switch that starts the measurement mode. Display 1
Reference numeral 9 visually displays the measurement data of the load cell 5. The judgment output circuit 20 is a circuit that outputs a judgment result, and when the judged press force measurement data is between the upper limit reference value UR and the lower limit reference value LR, a G signal indicating that the inspection has been passed is provided.
An o-fold signal is output, and if it is not within that range, an NG signal indicating failure is output. Alternatively, the 1fl11 constant data determined to be the true press-in force value itself may be output.

Next, an example of the content of the determination process executed under the control of the CPU 9 will be explained based on FIGS. 3 and 4. FIG. 3 shows the main flow. First, in step 21, it is checked based on the output of the mode changeover switch 17 whether or not it is the measurement mode. If it is the measurement mode, the process advances to step 22 and it is checked whether the start switch 18 has been turned on. If it is turned on, the process proceeds to step 26, where the display contents of the display 19 and the output contents of the judgment output circuit 20 are cleared, and preparations are made for a new measurement. Next, proceed to step 24, and load cell 5
It is checked whether the measurement data DATA of has reached the set value MX with the body, that is, whether DATA≧MX holds true.

FIG. 4 shows an interwoven routine, which is executed by interrupting the execution of the main flow at regular intervals (for example, 1 millisecond). First, in step 25, the data acquisition time setting device 1
Check whether the data import time set in step 6 has been reached, and select No.
If so, immediately terminate this included routine, but
If YES, proceed to step 26. For example, the data acquisition time is set such that data is acquired every pulse of the interwoven clock. In step 26, A
The measured data DATA output from the /D converter 8 is sampled and stored in an appropriate buffer and also stored in the measured data memory in the RAM 10. The contents of the buffer are updated every time the measurement data DATA is newly sampled, and the measurement data memory sequentially stores the sampled measurement data DATA in the order of sampling time. Note that the storage capacity of this measurement data memory is limited, so when all addresses are filled with sampled measurement data DATA, the memory of the oldest measurement data is cleared, and the most recently sampled measurement data is cleared instead. The measured data shall be stored.

Returning to step 24 in FIG. 3, the measurement data DATA to be determined is the currently sampled measurement data DATA stored in the buffer in step 26 in FIG. Measurement data DATA is set value M
If X has not yet been reached, proceed to step 27;
The content displayed on the display 19 is rewritten to the currently sampled measurement data DATAK stored in the buffer.

From NO in step 24, step 27 is passed through step 2 until the measurement data DATA reaches the set value MX.
The routine returning to step 4 is repeated, and when the step is reached, the process proceeds to step 28.

In step 28, the measurement data DATA (-n) which is temporally earlier than the current sampling timing (that is, the sampling timing at which DATA≧MX is established) by the number of samples n set by the backward sample number setting device 16 is stored.
is read from the measurement data memory in the RAM 10,
Store this in the buffer. In the next step 29,
It is checked whether the measurement data DATA(-n) stored in the buffer and stored n samples ago is between the upper limit reference value UR and lower limit reference value LR set by the setter 14.15. If YES, the process proceeds to step 30, where processing is performed to generate a GO multiplication signal indicating that the test has passed.

If NO, proceed to step 61 and indicate NG indicating inspection failure.
Performs processing to generate a signal. In the final step 62,
Measurement data DATA(-n) stored in the buffer
is displayed on the display 19, and the GO multiplied signal outputs an NG signal.

Note that in the setting mode, step 21 is N.

Then, in step 65 via steps 33 and 34, a process of importing the setting data of each setting device 12 to 16 is performed.

Therefore, during execution of this routine, the operator must set each setting device 12 to 1.
By setting 6 arbitrarily, the setting contents will be changed to CPU9.
is loaded into RAMl0 by. In step 36, the stored data DATA(
-n). In the next step 34, this DATA
(-n) is displayed on the display 19. This allows the measurement data DATA(-n) of n samples to be monitored in the setting mode.

With the above configuration, measurement data DATA(-n) indicating the true press force between the parts can be extracted in the process of step 28. Therefore, the determination in step 29 is made based on accurate press force measurement data, and it is possible to accurately determine pass/fail in product inspection. In addition, since the method calculates the press-in force measurement data by going back a predetermined number of samples from the measurement data that has already been sampled and stored, the press-in force is always accurately measured without being affected by the press-fitting speed or the press-fitting depth. Judgment can be made. In addition, the process of steps 29 to 61 in FIG. 3 may be omitted, and the measurement data DATA(-n) taken out in step 28 a number of n samples ago may be simply sent to the outside as true press-in force measurement data. Good too. Furthermore, the sampling timing of the measurement data is not constant and may be variable. Furthermore, the present invention can be implemented using a discrete dedicated circuit configuration without using a microcomputer.

[Brief explanation of drawings]

FIG. 1 is a graph showing an example of temporal changes in press-in force measurement data during press-fitting and its sampling timing; FIG. 2 is a block diagram schematically showing an example of the hardware configuration of a device used to carry out the present invention; 3 is a flowchart showing an example of a main routine executed by the microcomputer section of FIG. 2; FIG. 4 is a flowchart showing an example of an included routine executed as an interrupt to the flow of FIG. 3; The figure is a partially sectional side view schematically illustrating a conventional press force determination method. 1.2... Parts, 6... Die, 4... Press fitting tool of press machine, 5... Load cell, 6... Limit switch, 10... Random access memory (including measurement data memory) ).

Claims (1)

[Claims] A method for determining the press-fitting force when a first part is press-fitted into a second part by press working, the method being provided for measuring the load applied to a press-fitting tool of a press machine. Repeatedly sampling the measurement data of the load cell during press working and sequentially storing it in a memory; Detecting that the measurement data at a certain sampling timing has reached a predetermined barrel setting value; Based on this detection, the Pressure in press processing characterized by: retrieving measurement data that is temporally earlier than the sampling timing by a predetermined number of samples from the memory, and using the retrieved measurement data as data indicating the pressing force of the part. Input judgment method.