JPH0379133B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for determining whether the machining accuracy of a part to be press-fitted is good or bad.

(Prior art and its problems) Conventionally, in order to determine whether the machining accuracy of male and female parts that are press-fitted together is good or bad, a predetermined number of parts are extracted for each part or each lot. Dimensional inspection is generally performed manually or using an automatic inspection machine. At this time, not only when the extracted parts are inspected manually, but also when all the parts are inspected using an automatic inspection machine, the dimensional inspection is performed on a specific part of the inspected part ( For example, in outer diameter inspection, inspection is limited to only a few points (outer diameter), so defective products cannot be completely eliminated. For this reason, there is a risk that the male part may fall out of the female part during use after assembly (if there is insufficient press-fitting allowance) or the female part may crack (if there is excessive press-fitting allowance), leading to serious accidents. be. In order to avoid this risk, in addition to dimensional inspection, there is also a method of reading the press pressure using a gauge when press-fitting the press-fitted parts, but the pressure during press-fitting is not constant, and the pressure time is generally short. Therefore, it is extremely difficult to read.

(Means for Solving the Problems) The present invention has been made to eliminate the above-mentioned conventional drawbacks. Therefore, the present invention provides a method for determining whether the machining accuracy of a part to be press-fitted is good or bad. It is characterized by detecting and recording changes in the pressure of the press while press-fitting, reading out the pressure at a predetermined time during the press-fitting after the press-fitting is completed, and determining pass/fail by comparing the read pressure with a reference pressure. do.

(Function) Press pressure is detected as an electric signal by a pressure sensor, pressure changes are recorded moment by moment during press-fitting using a microcomputer, and after press-fitting is completed, the pressure value at a predetermined point during press-fitting is read out. This is compared with a reference pressure value that represents the desired machining accuracy, and it is determined whether or not the read pressure value is within a predetermined deviation from the reference pressure value, thereby determining whether the machining accuracy is good or bad. The pressure at a predetermined point during press-fitting may be read out after a predetermined time has elapsed from the start of press-fitting, or at one point or multiple points in time when the pressure has risen reversely for a predetermined time after the completion of press-fitting, or from the start of press-fitting until the completion of press-fitting. All read pressures may be read out. Since all operations are processed by a microcomputer, determination of pass/fail is easily and quickly performed. Also,
Since the pressure during press-fitting is recorded, the quality determination can be made at any time after press-fitting is completed, preferably immediately after press-fitting is completed. Furthermore, the pressure can be read out at any point during press-fitting, so depending on the shape, size, material, press-fitting method, etc. of the press-fitted parts, the pressure at the point when it is most effective to determine pass/fail can be read out. can be compared.

(Example) Hereinafter, the content of the present invention will be explained along with examples.

FIG. 1 shows an outline of an apparatus for carrying out the method of the present invention, in which a pressure sensor 3 for converting press oil pressure into an electric signal is attached to a press-fitting press 1 into which a press-fitted part is to be press-fitted, and the signal of the pressure sensor is used for press-fitting. The defect detection device 5 inputs the data and processes it with a microcomputer to determine whether the product is good or bad, and if it is found to be defective, a defect/alarm is issued.

FIG. 2 is a block diagram of this device, in which the press-fit abnormality detection device 5 connects a single-chip microcomputer 11 including a program memory 7 and a data memory 9, and outputs from the pressure sensor 3 to a filter 13, an amplifier 15, and a filter 15, respectively. An input section for inputting digital signals via the A/D converter 17, and an acquisition pitch PITCH that determines the signal acquisition time interval from the pressure sensor, an end pressure PE that determines the end point of signal acquisition, and the microcomputer 11, respectively. Various parameters such as the backward movement time MBC which determines the time from the end of signal acquisition to the pressure read out during press-in, the reference value pressure PG to be compared with the read pressure, and the start pressure PS which determines the point at which signal acquisition starts. A parameter switch 19 for setting, a printer 21 and an X-Y recorder 23 to which the pressure data stored in the data memory 9 and setting values of various parameters are written.
, an LED display 25 that is used to display the pressure value during press-fitting hourly and to indicate pass/fail judgment, and an indicator lamp 27 that displays the pass/fail judgment result in color, which will issue an alarm when a defect is detected and 1 includes an alarm 29 equipped with a relay contact that transmits an operation stop command from the microcomputer 11, and these printer 21, X-Y recorder 23, and LED.
It consists of a control switch 31 that controls ON/OFF of attached devices such as the display 25.

Next, the operation of the press-fit abnormality detection device will be explained with reference to the flowchart shown in FIG. Prior to detection, various parameters are set using the parameter switch 19, and each device is set to the ON state using the control switch 31.
When the power is turned on, the program starts and the above-mentioned setting parameters are read into the data memory 9 (step). When the command to start the press is received (step), the next step is to compare the pressure from the pressure sensor 3 with the starting pressure PS set by the parameter switch (step), and the pressure of the pressure sensor exceeds the starting pressure PS. The preset acquisition pitch PITCH time is counted by the timer and the first pressure data is recorded in the data memory 9 (step). the above,
This operation is repeated (steps) until the pressure from the pressure sensor 3 reaches the preset end pressure PE (for example, the relief pressure of the pressure press when the press-fit part holding jig comes into contact with the stopper), and when the end pressure is reached. At this point, it is known that the press-fitting has been completed and the data acquisition is stopped. Next, the data at the time when the press-fitting is completed by the backward movement time MBC set by the parameter switch 19 is read from the data memory 9 (step), and the value is compared with the reference value PG set by the parameter switch 19. A quality determination is made by determining whether the read pressure value is within a predetermined deviation amount from a reference value (step). If it is determined to be acceptable, the process returns to the next step and the next press-fitted part is judged to be good or bad. If it is determined to be a failure, an alarm 29 is generated and a lamp 2 indicating defective is activated.
7 is turned on (step), and at the same time the operation of the press-fitting press 1 is stopped (step).

The data read in the above steps are printed out by the printer 21, recorded by the X-Y recorder 23, and displayed on the LED display 25 at the same time.

FIGS. 4a and 4b show examples of output of experimental results to a recorder according to the method of the present invention. In this experiment, two valve guides (one for intake and one for exhaust) were simultaneously press-fitted into the cylinder head of an earthmoving vehicle, and a male part of the same size was simultaneously pushed into two female parts of different lengths. I'm reading. The materials and dimensions of the male and female parts used in the experiment, as well as the pressurizing conditions, are as follows.

Male part Material: Alloy cast iron Outer diameter: 16.713±0.008φ [mm] Length: 71.0 [mm] Surface condition: Polished Ra [1.6μm] Female part Material: Cast iron (FC 20) Inner diameter: 16.68±0.013φ [mm] Length: 29.0mm/49.0mm Surface condition: Reamed finish Ra1.6~2.5 [μm] Pressure conditions Press: C-type hydraulic press (maximum press capacity approximately 10 tons) Pressure setting: 75~80Kg・f/ cm ² (maximum press force set at approximately 5 tons) Press-in speed: approximately 1 M/min (17 mm/sec) Figure 4 a shows the results under normal conditions, and Figure 4 b shows the results under abnormal conditions. As can be seen from these graphs, there is a large difference in press force at the intermediate insertion point between normal and abnormal conditions.
It can be seen that, as in the present invention, the effect of comparing the press force during press-fitting with a reference pressure to determine the quality is remarkable.

Note that the present invention is not limited to the shape, size, material, press-fitting method, etc. of the press-fit parts, and can be broadly applied to press-fitting of male and female parts by a press-fit press using hydraulic pressure, water pressure, or air pressure.

(Effects of the Invention) As described above, according to the present invention, a method is provided that can quickly and easily determine whether the machining accuracy of a press-fitted part is good or bad after the press-fitting is completed.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an apparatus for carrying out the method of the present invention, Fig. 2 is a block diagram of the apparatus, Fig. 3 is a flowchart showing the operation of the press-fit abnormality detection device, and Fig. 4 is a diagram of the apparatus according to the present invention. It is a graph showing an example of experimental results.

Claims (1)

[Claims] 1. To determine whether the machining accuracy of a part to be press-fitted is good or bad, the pressure change of the press is detected and recorded while the part is press-fitted by a press, and after the press-fitting is completed, the pressure change at a predetermined time during the press-fitting is detected and recorded. A method for determining the quality of a press-fitted part by reading the pressure at and comparing the read pressure with a reference pressure. 2. The method according to claim 1, wherein the read pressure is a pressure at one point or a plurality of points between the start of press-fitting and the completion of press-fitting. 3. The method according to claim 1, wherein the read pressures are all pressures recorded from the start of pressure to the completion of press-fitting. 4. The method according to any one of claims 1 to 3, wherein the reading of the pressure is performed immediately after the pressure is completed.