JPH0611330A - Detection switch - Google Patents

Abstract

PURPOSE:To automatically set the sensitivity of a detection switch without adjusting a variable resistor, etc., for adjusting the sensitivity of the switch. CONSTITUTION:An object to be inspected is positioned to a set position at the time of making power supply and the output of a sensor circuit 2 is written in a memory 7 as a threshold Vth. When such an arrangement is made, the threshold Vth can be automatically set at the time of making power supply. Thereafter, a comparing means 12 compares a signal Vin obtained from the sensor circuit 2 with the threshold Vth read out from the memory 7 through a memory reading-out means 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection switch, such as a proximity switch or a photoelectric switch, which is characterized by sensitivity adjustment.

[0002]

2. Description of the Related Art Sensitivity adjustment of a conventional detection switch such as a photoelectric switch or a proximity switch is set in advance using a variable resistor so that a predetermined detection distance is obtained at the time of manufacture in a switch of a type in which the detection distance is fixed. Or, it is adjusted using laser trimming or the like. Further, even in a detection switch such as a photoelectric switch or a pressure switch whose detection level can be adjusted from the outside, the same adjustment is performed at the time of manufacture so that the adjustment range becomes a predetermined range. FIG. 6 is a diagram showing a manufacturing procedure of a conventional proximity switch. In this figure, a hybrid IC (HIC) is assembled and attached to the sensor unit, and after performing an intermediate inspection, the sensitivity is adjusted. Then fill the voids with epoxy resin etc.
After shipping inspection, they are shipped.

[0003]

However, in such sensitivity adjustment at the time of manufacturing, it is necessary to adjust the trimming resistor and the variable resistor on the printed circuit board in a state where the detection switch itself is incomplete. Therefore, there is a problem in that the sensitivity is distorted due to the distortion of parts due to the assembly after the adjustment.

Particularly, in the proximity switch in which the detection coil and the electronic circuit section are filled with epoxy resin, the resin is filled once except for the variable resistor and the trimming resistor, and after adjustment, all voids are filled with the resin. Need to be filled.
For this reason, there is a drawback that the sensitivity is not correct and the assembling workability is poor. Further, since the trimming resistor needs to be arranged at an adjustable position, the wiring on the printed circuit board becomes complicated, and the wiring becomes long, and the noise resistance is lowered.

The present invention has been made in view of such conventional problems, and it is a technical subject to make it possible to easily set the sensitivity with high accuracy without using a variable resistor.

[0006]

According to the present invention, a sensor circuit that outputs a signal of a level corresponding to a distance to an object, a non-volatile memory that stores a threshold value, and a level that corresponds to an output of the sensor circuit after power is turned on. Is written as a threshold value in the memory, memory reading means for reading the threshold value held in the memory, and the threshold value read by the memory reading means and the output of the sensor circuit are compared to determine the object detection signal. And comparing means for outputting.

[0007]

According to the present invention having such a feature, the object is arranged in advance at the position which becomes the threshold value of the detection switch, and the detection switch is powered on. Then, the output from the sensor circuit obtained at that time is written as a threshold value in the memory by the memory writing means. Thereafter, the written threshold value is read by the memory reading means, and the presence of an object can be determined by comparing the threshold value with the output from the sensor circuit by the comparing means.

[0008]

2 is a schematic view showing the appearance of a proximity switch according to an embodiment of the present invention. As shown in the figure, the proximity switch 1 has a detection surface on the front surface and detects an object located at a predetermined distance from the front surface. FIG. 3 shows a change in the amplitude level with respect to the distance to the object, which is output so as to be in the ON state when the object approaches the predetermined threshold value Vth.

FIG. 1 is a block diagram showing the configuration of a proximity switch according to an embodiment of the present invention. In the figure, the sensor circuit 2 includes, for example, an oscillation circuit including an oscillation coil, a detection circuit that detects and rectifies the output of the oscillation circuit, and a discrimination circuit that discriminates the output of the oscillation circuit with a predetermined threshold value. Is given to the microcomputer 4 via. A power supply circuit 5, an output circuit 6 and a memory 7 are connected to the microcomputer 4. The memory 7 is a non-volatile E
EPROM or a memory backed up by a battery. The microcomputer 4 is provided with an A / D converter 10 for converting the output of the amplifier 3 into a digital signal and a noise removing means 11 for removing an abnormal level signal of the output of the A / D converter 10. Output is comparison means 1
2, provided to the memory writing means 13. The memory writing means 13 writes the output of the noise removing means 11 in the memory 7 when the power supply circuit 5 is powered on. The memory reading means 14 reads the threshold value Vth held in the memory and gives it to the comparing means 12. The comparing means 12 compares the input signal Vin with the threshold value Vth, and gives an output to the output circuit 6 when Vin exceeds Vth. The reset means 15 resets the memory 7 via the memory writing means 13. As the reset means, for example, a reset signal can be input by short-circuiting a predetermined terminal of the printed board.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. When the power is turned on, first, initial setting is performed in step 21, and then step 22
Then, the process proceeds to step S6 and the threshold value Vth held in the memory 7 is read out. Assuming that the memory 7 is preset with a threshold value of 0 in advance, the process proceeds to step 23 to check whether the threshold value is 0 or not. If it is 0, the threshold value has not been set yet. Therefore, the detection object 8 is arranged at a position that becomes the detection distance threshold value of the proximity switch 1, and the signal Vin obtained after the noise removal is taken as Vth, Writing to the memory 7 from the memory writing means 13 (steps 24 and 2)
5). If Vth is not 0, the process proceeds to step 26 without performing such processing, and it is checked whether the reset signal is input. If there is no reset signal, the routine proceeds to step 27, where the input value Vin obtained at that time is compared with the threshold value Vth. If Vth is larger, step 2
In step 8, the output is turned on and the object detection signal is output to the outside. If Vin is larger than the threshold value Vth, step 29.
Then, the output is turned off and the process returns to step 26. If there is a reset input in step 26, step 30
Proceed to and write Vth = 0 as a threshold value in the memory 7. When the power is turned on again in this way, the same processing is repeated and a new threshold value Vth can be set. Here, the microcomputer 4 achieves the function of the memory reading means 14 for reading the threshold value Vth from the memory in step 22, and achieves the function of the memory writing means 13 for writing the threshold value in the memory in steps 23 to 25. There is. Further, the microcomputer 4 achieves the function of the comparison means 12 which compares the threshold value read in steps 26 to 29 with the input signal.

The proximity switch of this embodiment is assembled in the process shown in FIG. 5, for example. That is, the hybrid IC portion of the proximity switch is assembled in step 41, and attached to the sensor portion in step 42. Then, in step 43, an intermediate inspection is performed. At this time, since it is necessary to turn on the power, at this time, some threshold value V
th will be remembered. Therefore, as described above, the predetermined terminals on the printed circuit board are short-circuited and reset (step 44). Then, in step 45, it is assembled in the case and the inside is filled with the filling material to complete the process. Then, according to the flowchart as shown in FIG.
The power is turned on with the detection object 8 arranged at a predetermined position. In this way, the sensitivity is automatically set (step 46). Then, in step 47, a shipping inspection is performed to complete the proximity switch.

In this embodiment, the set value can be reset only at the time of assembly. However, if this reset terminal is led out of the proximity switch, the user can readjust the sensitivity when necessary. it can. It is also possible to externally control the mode of the sensor so that the threshold value can be set only in the sensitivity setting mode.

Although the present embodiment has been described with respect to a high frequency oscillation type proximity switch, it goes without saying that the present invention is not limited to proximity switches and can be applied to various other detection switches such as photoelectric switches.

[0014]

As described above in detail, according to the present invention, it is not necessary to adjust the sensitivity by using the variable resistor or the trimming resistor, and the sensitivity is automatically adjusted when the power is turned on. It can be carried out. Further, since the sensitivity can be set in a state where the filling material or the like is filled inside, there is an effect that the sensitivity can be set accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a detection switch according to an embodiment of the present invention.

FIG. 2 is a diagram showing a positional relationship between a proximity switch and an object according to this embodiment.

FIG. 3 is a graph showing a change in amplitude with respect to a detection distance of the proximity switch according to the present embodiment.

FIG. 4 is a flowchart showing a sensitivity setting operation after power is turned on in the present embodiment.

FIG. 5 is a flowchart showing an assembling procedure of the present embodiment.

FIG. 6 is a flowchart showing a procedure for assembling a conventional proximity switch.

[Explanation of symbols]

 1 Proximity Switch 2 Sensor Circuit 3 Amplifier 4 Microcomputer 5 Power Supply Circuit 6 Output Circuit 7 Memory 10 A / D Converter 11 Noise Removal Means 12 Comparison Means 13 Memory Writing Means 14 Memory Reading Means 15 Reset Means

Claims (2)

[Claims] 1. A sensor circuit that outputs a signal of a level corresponding to a distance to an object, a non-volatile memory that stores a threshold value, and a threshold value in the memory that corresponds to the output of the sensor circuit after power is turned on. A memory writing unit for writing, a memory reading unit for reading a threshold value held in the memory, a threshold value read by the memory reading unit and an output of the sensor circuit are compared, and an object detection signal is output. A detection switch comprising: a comparison unit. 2. The device according to claim 1, further comprising reset means for resetting the threshold value set in the memory.
The detection switch described.