JP3038265B2 - Sensor switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor switch which performs a switching operation based on a change in a physical quantity such as pressure, light, magnetic field and the like.

[0002]

2. Description of the Related Art In recent years, for example, in an automated manufacturing line in a factory, a transfer device that sucks a work by using a vacuum force and transfers the work to a predetermined position is often used. In this method, as shown in FIG. 6, a suction head 3 addressed to a work 2 is provided on a movable transfer head 1 and the suction pad 3 is switched between a vacuum source and a compressed air source (or atmosphere). This is a configuration for selectively communicating with each other via the valve 4. In the apparatus having this configuration, when the work 2 is lifted and conveyed, the suction pad 3 is addressed to the work 2 in a state where the suction pad 3 is connected to a vacuum source. To a compressed air source (or atmosphere).

In such a vacuum suction type transfer apparatus, it is necessary to establish a sequence in which the transfer head 1 is moved after confirming that the work 2 has been sucked by the suction pad 3. Therefore, this kind of device has a suction pad 3
A pressure-type sensor switch for measuring the degree of vacuum (pressure) in the inside is provided, and a switching operation is performed when it is detected that the work 2 is completely sucked and the degree of vacuum in the suction pad 3 is sufficiently increased. It has become.

As an electrical configuration for realizing such a function, it is common to provide a binary comparator for comparing the level of a measurement signal obtained by amplifying a signal from the pressure sensor with a predetermined judgment reference value. is there. FIG. 7A shows a typical change pattern of the level of the measurement signal SP obtained from the pressure sensor when the suction and release of the work 2 are repeated. In the figure, the level of the measurement signal Sp increases when the degree of vacuum increases (pressure decreases). As shown here, when the suction pad 3 is open, the degree of vacuum of the suction pad 3 is increased. Is balanced at an open vacuum slightly higher than atmospheric pressure, and the measurement signal Sp
Is at the "open level". Further, when the work 2 is completely sucked by the suction pad 3, the degree of vacuum in the suction pad 3 reaches a sufficiently high suction vacuum from the equilibrium release vacuum and equilibrates. Level and stabilize. Then, when compressed air is sent into the suction pad 3, the degree of vacuum drops sharply. Therefore, the signal level once drops below the atmospheric pressure level, and after the work 2 is opened, it is communicated with the vacuum source and the "open level" And repeat the above. In this case, the comparator performs a switching operation using the determination reference value as a threshold value, and a switching waveform as shown in FIG.

On the other hand, in this type of apparatus, when air leaks to the suction pad 3 or the like or the filter is clogged, the degree of equilibrium vacuum at the time of suction or at the time of opening changes. If the equilibrium suction vacuum degree does not become sufficiently high, the work 2 may drop during the conveyance, and if the equilibrium release vacuum degree does not become sufficiently low, the work 2 which is sucked will not separate from the suction head 3. Cause. Therefore, the degree of vacuum at the time of suction of the work 2 (equilibrium suction vacuum degree) and the degree of vacuum at the time of opening the work (equilibrium release vacuum degree) are obtained by the pressure sensor.
It is necessary to determine whether these are sufficiently higher or lower than a predetermined value.

Therefore, there is a conventional technique for realizing such a function described in Japanese Utility Model Laid-Open No. 58-57135. This is because, as shown in FIG. 8, an unstable region is set so as to include the determination reference value, and the time during which the level of the measurement signal SP from the sensor stays within the unstable region,
The configuration is such that a reference time set in a timer is compared with a reference time, and an alarm signal is output when the time during which the signal level remains within the unstable region exceeds the reference time.

When the change pattern of the pressure (degree of vacuum) is normal and the measurement signal level changes as shown in the section A1 in FIG. 1, the time required for the measurement signal level to pass through the unstable region is short. No signal is output. However, for example, when the vacuum source side filter is clogged and the suction vacuum degree does not sufficiently decrease, the measurement signal level at the time of suction becomes lower than the stable suction level,
The time during which the measured signal level remains in the unstable region becomes longer, and when this exceeds a predetermined reference time TS, an alarm signal is output.

[0008]

However, the above-mentioned method has a drawback that it is not practical because it may malfunction depending on the specification of a vacuum suction device that repeats suction and release of a work. That is, when the weight of the work to be lifted by the vacuum suction device is relatively heavy, the suction pad is large and the exhaust amount is large, and the exhaust time and the suction / release cycle time are long. In particular, when the evacuation time required from the degree of open vacuum to the degree of suction vacuum is long, the measurement signal level from the sensor remains in the unstable region for a relatively long time, which is a fixed reference time. There is a possibility that an alarm signal will be output even in a normal state exceeding Ts. Conversely, if the suction / release cycle time is shorter than the reference time, no alarm signal can be output.

It is conceivable that such a situation can be solved by using an on-delay timer. However, the time during which the level of the measurement signal remains in the unstable region is
As described above, it varies depending on the displacement of the vacuum pump, the size of the suction pad, the specification of the switching valve, and the like. In practice, the fluctuation range may exceed a range of several hundred times. Therefore, in order to realize the above-described conventional configuration, an on-delay timer is provided, and the adjustment is repeated individually to meet the specifications of the vacuum suction device to be applied. This requires a difficult initial setting operation of setting the parameters.

The present invention has been made in view of the above circumstances, and an object thereof is to detect an unstable state irrespective of a change pattern of a measurement signal level from a sensor, and to facilitate initial setting work. An object of the present invention is to provide a certain sensor switch.

[0011]

According to the present invention, there is provided a sensor switch for converting a physical quantity such as pressure, light, a magnetic field or the like into an electric signal corresponding to the magnitude thereof, and a level of a measurement signal based on a signal from the sensor. And a sensor main circuit for operating the switching element according to the comparison result with the predetermined reference level, wherein the pressure, light,
The switching is performed according to a change pattern of a physical quantity such as a magnetic field, and when the change pattern of the physical quantity such as the pressure, light, and magnetic field is normal, the time during which the level of the measurement signal is within the predetermined range. And a reference time setting means for setting and storing a reference time based on the reference time, and comparing the time when the level of the measurement signal is within a predetermined range with the reference time, and the time is different from the reference time. It is characterized in that a warning means for outputting a warning signal is provided on condition that the above condition is satisfied.

[0012]

According to the reference time setting means having the above structure, when the change pattern of the physical quantity such as pressure, light, magnetic field, etc. is normal, the time during which the level of the measurement signal is within a predetermined range is measured. The reference time is set. This makes it easy to set an optimum reference time according to the specifications and use conditions specific to the device incorporating the sensor switch.

After that, the pressure,
If the change pattern of the physical quantity such as light or magnetic field becomes different from the normal pattern, the time during which the level of the measurement signal is within the predetermined range becomes different from the reference time. A signal is output.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a pressure-type sensor switch incorporated in a vacuum suction device will be described below with reference to FIGS.

The electrical configuration is as shown in FIG. 1, and the pressure sensor 11 is a vacuum (pressure) in the suction pad of the vacuum suction device.
Is output, and this is amplified by the amplifier 12. The pressure measurement signal Sp output from the amplifier 12 is given as a digital signal to the CPU 14 via the A / D converter 13 and is read by the CPU 14 at a predetermined sampling cycle. Each process is executed.

The CPU 14 includes a storage unit 15 having a ROM and a RAM, an input unit 16 including various key switches,
A display section 17 composed of an LED and an output section 18 having switching elements for a main circuit and an alarm are connected. The operation program of the CPU 14 is written in the ROM section of the storage section 15, and various operation signals can be given to the CPU 14 from the key switches of the input section 16. The LED of the display unit 17 indicates the operation state of the sensor switch, and each switching element of the output unit 18 is
The switching operation is performed based on the signal from.

Now, the CPU 14 determines that the measurement signal S
The level of p is compared with a predetermined reference level (judgment reference value), and functions as a sensor main circuit for operating the switching element of the output unit 18 according to the comparison result, and as a warning unit and a reference time setting unit. Also works.
Hereinafter, these functions will be described in detail. In the following description, the terms “stable suction level”, “stable release level”, “suction level” and “release level” are used in addition to the above “judgment reference value”. Correspond to the following degree of vacuum (pressure), and how to set them will be described later.

"Judgment reference value": a vacuum degree of a threshold value for judging whether the suction pad is opened or the work is sucked. "Open level": the suction pad is connected to a vacuum source. , The degree of equilibrium vacuum when the work piece is not suctioned and the suction pad is open (also referred to as “equilibrium release vacuum degree”). "Suction level": The suction pad is connected to a vacuum source,
In addition, the degree of equilibrium vacuum when the work is suctioned in a normal state (also referred to as "equilibrium suction vacuum degree"). "Stable release level": A vacuum level recognized as the upper limit of the equilibrium release vacuum level when the vacuum suction device is in a normal state and the suction pad is open. "Stable adsorption level": A vacuum that is recognized as the lower limit of the equilibrium adsorption vacuum degree when the vacuum suction device is in a normal state and the work is being adsorbed on the suction pad.

In the following description, a range between the "stable release level" and the "stable adsorption level" may be referred to as an "unstable area".

<Function as Sensor Main Circuit> Since the pressure sensor 11 of this embodiment is incorporated in a vacuum suction device for transporting a work, the pressure sensor is normally used when the vacuum suction device is functioning normally. The measurement signal Sp based on the signal from 11 repeatedly changes in a pattern as shown in FIG.

On the other hand, although not shown, the CPU 14 periodically executes a suction determination routine for comparing the level of the measurement signal Sp read therein and the determination reference value, for example, by a timer interrupt. As a result, when the measurement signal Sp repeatedly changes in a pattern as shown in FIG. 7A, as shown in FIG. 7B, it turns on when the level of the measurement signal Sp exceeds the determination reference value, The output unit 18 outputs a detection signal that is turned off when the voltage falls below this.

<Function as Alarm Means> For example, the suction pad of the vacuum suction device loses flexibility, and air leaks from between the suctioned work and clogging of the filter on the vacuum source side. If the air cannot be sufficiently sucked, the degree of vacuum in the suction pad does not sufficiently increase while the work is being sucked, so that the equilibrium suction vacuum degree decreases. Therefore, the measurement signal Sp changes as shown in the section X1 of FIG. 3A in a normal state, whereas the measurement signal Sp changes in a pattern as shown in the section X2 of the above-mentioned case in an abnormal state. become.

The operation of the CPU 14 in this case relates to an alarm routine as shown in FIG. 2, which is executed periodically. Here, first, it is sequentially determined whether the level of the measurement signal Sp is equal to or higher than the stable release level, equal to or lower than the stable suction level, and whether the timer is started (step 1).
01 to 103). Here, if the level of the measurement signal Sp is not in the unstable region (between the stable release level and the stable suction level), the process immediately returns and shifts to other necessary processing. After activating the timer (step 104), the process returns. After the start of the timer, it is determined in step 105 whether the reference time TR has elapsed. The reference time TR is set by a teaching routine described later.

As shown in a section X2 of FIG. 3, the measurement signal Sp
Becomes "YES" in step 105 when the level remains within the unstable region for more than the reference time TR, so that step 106 is executed and an alarm signal is output (see time t1 in FIG. 3 (c)). ). Thereby, it can be notified that an abnormality has occurred such that the stable adsorption level is located in the unstable region.

It is also assumed that the level of the measurement signal Sp changes as shown in a section X3 in FIG. In addition, such a phenomenon that the equilibrium open vacuum degree becomes higher than the vacuum degree corresponding to the stable open level tends to easily occur in a configuration in which compressed air is sent to the suction pad when the work is opened. In this case, when the alarm routine is executed,
An alarm signal is output at time t2 in the same manner as in the above section X2.

<Function as reference time setting means>
Each level such as the above-mentioned judgment reference value and the reference time TR
The “teaching routine” for setting “1” and “2” will be described. This description should clarify the functional configuration of the reference time setting means.

This routine has the contents shown in FIG.
Normally, when the sensor switch is set, the sensor switch is activated by the operator performing a predetermined operation on the input unit 16. Therefore, a teaching routine will be described together with an operation procedure to be performed by an operator.

The operations to be performed by the operator are as follows. First, the vacuum suction device is started, and the suction pad connected to the vacuum source is kept open. Next, the above-described teaching routine is started, and after a while, the suction pad is sucked to the work. When it is confirmed that the work is sucked to the suction pad with sufficient strength, the work to be performed by the worker is completed. By performing the above operation, the degree of vacuum in the suction pad draws a change pattern as shown in FIG.

On the sensor switch side, when an operation for starting the teaching routine is performed, first, at step 20.
At step 1, the sampling data of the measurement signal Sp is read, and at step 202, it is determined whether or not the value is constant over a plurality of samplings. When the sampling data of the measurement signal Sp is constant over a plurality of samplings after the start of the vacuum suction device, it means that the degree of vacuum in the suction pad has reached the equilibrium open vacuum degree. It is stored as an open level (step 203).

Thereafter, the sampling data is read again (step 204), and it is determined whether or not this indicates an increase in the degree of vacuum (step 205). Here, the increase in the degree of vacuum means that the work has begun to be sucked by the suction pad. Therefore, when it is determined that the degree of vacuum has increased, the sampling data is read again (step 206), and the process waits until the data does not change over a plurality of samplings. The fact that the sampling data becomes constant after the work is adsorbed on the suction pad ("yes" in step 207) means that the degree of vacuum in the suction pad has reached the equilibrium suction vacuum degree. It is stored as the suction level (step 208). With the above processing, the release level and the suction level are set.

Next, step 209 is executed, and each value of the judgment reference value, the stable release level and the stable suction level is calculated. The determination reference value is calculated as a median between the release level and the suction level set as described above, the stable release level is calculated as a median between the release level and the determination reference value, and the stable suction level is calculated. Is calculated as the median between the adsorption level and the determination reference value. That is, assuming that the release level is Po, the suction level is PS, the determination reference value is Pr, the stable release level is Pso, and the stable suction level is Pss, the relationship between the values is as follows. These are shown in FIG.

Determination reference value Pr = (PS-Po) / 2 Stable release level Pso = (Pr-Po) / 2 Stable adsorption level Pss = (Ps-Pr) / 2

Each value calculated as described above is stored in the storage unit 15.
Is written and stored in a rewritable ROM portion (step 210).

Next, the process proceeds to step 211, where the number of sampling data between the stable release level and the stable suction level is counted, and the time T is calculated by multiplying the count value by the sampling period ts (step 21).
2). This time T corresponds to the time during which the level of the measurement signal Sp remains within the unstable region, as is apparent from FIG. Then, the process proceeds to step 213, where the reference time TR is calculated by multiplying the time T by a coefficient k (1-2 in this embodiment), and is also written and stored in the rewritable ROM portion of the storage unit 15. (Step 213).

Thus, the execution of the teaching routine is completed, and the reference time TR is automatically set.

Incidentally, since the sensor switch is generally a general-purpose component, the operating conditions required by the device in which the sensor switch is incorporated are variously different. Even in the pressure-type sensor switch as in the present embodiment, the reference time TR, which is a reference for judging the leakage of the suction pad and the abnormality of the vacuum source, has various values depending on the device in which the sensor switch is incorporated. Is required. Therefore, its reference time TR
It is more preferable to set these individually on the side of the installer of these devices than to set in advance by the manufacturer before the sensor switch is shipped from the factory. However, in the conventional sensor switch, there is a problem that if the setting is left to individual work on the side of the equipment installer, the setting work is extremely troublesome and impractical.

In this regard, according to the sensor switch of the present embodiment, if the operator starts the vacuum suction device and performs the operation of starting the teaching routine, the operation is performed to actually suck the work to the suction pad. The optimum reference time TR for the device can be automatically set.

Further, in this embodiment, in particular, the judgment reference value as a reference for performing the switching operation, the stable release level and the stable suction level for defining the unstable region can be automatically set by executing the teaching routine. Therefore, the initial setting work can be performed more easily while increasing the versatility.

Of course, while the initial setting operation is easy as described above, it is possible to cope with a change pattern of the measurement signal Sp as shown in the section X3 in FIG. 3, and there is no inferior performance.

The present invention is not limited to the above embodiment, but can be modified as follows.

(1) In the above embodiment, not only the reference time TR, but also the judgment reference value and each level of the unstable area can be automatically set by executing the teaching routine. Even if it performs, the intended purpose can be sufficiently achieved. As a configuration for manual setting, for example, a required pressure value is input from an input unit using a digital switch or a variable resistor, or the pressure sensor side is adjusted to a required pressure, and then the input unit is When a specific key switch is operated, the value may be set and stored in the storage unit.

(2) In the above embodiment, an example in which the present invention is applied to a pressure-type sensor switch has been described. However, the present invention is not limited to this. For example, a photoelectric switch, an electromagnetic proximity switch, an ultrasonic sensor switch, and the like. Similarly, the present invention can be applied to a switch that measures a physical quantity other than the pressure described above.

In addition, the present invention is not limited to the embodiment described above and shown in the drawings, and can be carried out with various modifications without departing from the scope of the invention.

As described above, according to the sensor switch of the present invention, when the change pattern of the physical quantity such as pressure, light, and magnetic field is normal, the time during which the level of the measurement signal is within the predetermined range is obtained. Is measured, and the reference time is set based on this. Therefore, an unstable state can be detected irrespective of the change pattern of the measurement signal level from the sensor, and an excellent effect that the initial setting work becomes easy is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing an alarm routine.

FIG. 3 is a timing chart showing a change pattern of a measurement signal and a signal output.

FIG. 4 is a flowchart showing a teaching routine.

FIG. 5 is a diagram showing a change pattern of a measurement signal at the time of initial setting.

FIG. 6 is a perspective view showing a part of the vacuum suction device.

FIG. 7 is a timing chart showing a relationship between a change pattern of a measurement signal from a pressure sensor and a detection signal.

FIG. 8 is a timing chart showing a relationship between a change pattern of a measurement signal from a pressure sensor and an alarm output.

[Explanation of symbols]

 11 pressure sensor 14 CPU (reference time setting means, alarm means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G08B 23/00-31/00 G01D 1/18 G01R 33/00 H03K 17/94

Claims (1)

(57) [Claims] 1. A sensor for converting a physical quantity such as pressure, light, magnetic field or the like into an electric signal corresponding to the magnitude thereof, and comparing a level of a measurement signal based on a signal from the sensor with a predetermined reference level. A sensor main circuit for operating a switching element in accordance with a comparison result, and performing switching in accordance with a pattern of change in a physical quantity such as the pressure, light, and magnetic field that repeatedly changes, wherein the pressure, light, and magnetic field are changed. Reference time setting means for measuring a time during which the level of the measurement signal is within a predetermined range when the change pattern of the physical quantity such as is normal, and setting and storing a reference time based on the measurement signal; Alarm means for comparing a time during which the level is within the predetermined range with the reference time, and outputting an alarm signal on condition that the time is different from the reference time. Sensor switch that.