JPH10170649A - Ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a user to manually set a blind zone with a simple operation, and to easily and rapidly react any change of obstruction arrangement after attachment of a sensor. SOLUTION: CPU 1 includes a detecting-operation controlling circuit 2 which totally controls detecting operation. After the detecting-operation controlling circuit 2 receives a setting signal from a blind-zone setting switch 3, it writes the set contents into a reloadable non-volatile memory 4 and shows them on a display 5. When the detecting-operation controlling circuit 2 detects the distance of its object and the detected distance is within the blind-zone region defined by the blind-zone setting switch 3, the circuit 2 controls a detecting phase circuit 12 through a blind-zone setting/running circuit 15 and eliminates its reflected wave so that any object within the blind-zone region is not detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor for detecting a distance to an object by transmitting and receiving ultrasonic waves.

[0002]

2. Description of the Related Art An ultrasonic sensor such as an ultrasonic level sensor and an ultrasonic level relay is installed inside a container such as a chemical device and used to detect a distance to a liquid surface to be detected. There are many. In this case, since various obstacles such as various devices and protrusions are arranged inside the container, the ultrasonic sensor is installed at the mounting position of the ultrasonic sensor so that the obstacle is not erroneously detected as a liquid surface. Need to be very careful. However, an obstacle may be positioned between the sensor and the liquid surface depending on the arrangement of obstacles in the container and the usage conditions of the container.

In such a case, it is unavoidable that the ultrasonic sensor detects an obstacle, so that a dead zone is conventionally set. In setting this dead zone, the sensor manufacturer surveys the user's usage environment in advance, sets upper and lower limits above and below obstacles,
Normally, this is performed by setting the range between the upper and lower limits as the dead zone.

[0004]

As described above, if the mounting position of the obstacle is known in advance, the setting of the dead zone by the manufacturer prevents the ultrasonic sensor from erroneously detecting the obstacle as a liquid level. Can be prevented. However, after the ultrasonic sensor is mounted in the container, the arrangement state of the obstacle and the use conditions may be changed. In such a case,
Although it is necessary to set the dead zone again, the setting of the dead zone can only be performed by the manufacturer.The user must stop using the container and reset the dead zone each time. I had to ask.

The present invention has been made in view of the above circumstances, and has as its object to provide an ultrasonic sensor that allows a user to set a dead zone by himself.

[0006]

As means for solving the above problems, the invention according to claim 1 transmits an ultrasonic wave toward an object to be detected and detects a reflected wave of the ultrasonic wave. In the ultrasonic sensor that detects the position of the detection target by measuring the time from the transmission time to the reflected wave detection time, a dead zone setting switch for setting a dead zone for the reflected wave detection, A display for displaying an area of the dead zone set by the dead zone setting switch, and a reflected wave from an obstacle existing in the area of the dead zone set by the dead zone setting switch not being detected And a detection operation control circuit for controlling the detection operation as described above.

According to a second aspect of the present invention, in the first aspect of the present invention, the control mode of the detection operation control circuit includes a low sensitivity mode and a high sensitivity mode classified according to a detection distance. The operation control circuit controls the detection operation by alternately switching between the two modes.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the detection operation control circuit temperature-compensates a value of a non-sensing zone set based on an input of an atmosphere detection temperature. It is characterized by the following.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the dead zone is an area formed between an upper limit and a lower limit. Is closer to the sensor side than the lower limit value, and the detection operation control circuit performs a detection process by setting a region farther than a position having a value twice as large as the upper limit value of the dead zone as a detection prohibition region. There is a feature.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the ultrasonic level sensor according to the present embodiment. In this figure,
The CPU 1 is provided with a detection operation control circuit 2 that performs overall control of the detection operation of the ultrasonic level sensor. When the detection operation control circuit 2 receives a setting signal from the dead zone setting switch 3, it writes the setting contents to the rewritable nonvolatile memory 4 and displays the setting contents on the display 5. Here, various types of the dead zone setting switch 3 and the display 5 are conceivable, but in this embodiment, each time the user presses the push button type dead zone setting switch 3 with a finger, the display is turned off. It is assumed that the upper limit value and the lower limit value of the dead zone are sequentially digitally displayed on the screen 5. The detection operation control circuit 2 is also adapted to input a detection signal about the ambient temperature from the temperature detector 6, and based on this temperature detection, the temperature of the upper limit value and the lower limit value of the dead zone is detected as described later. Compensation is provided.

When the detection operation control circuit 2 outputs an ultrasonic emission command to the reference pulse generation circuit 7, the reference pulse generation circuit 7 generates a reference pulse. This pulse is sent to the sensor drive circuit 9 via the pulse modulator 8, and the sensor drive circuit 9 sends an ultrasonic wave from the ultrasonic transmission / reception unit 10 toward the liquid surface as the detection target. Next, the reflected wave of the ultrasonic wave reflected on the liquid surface is received by the ultrasonic transmission / reception unit 10 and sent to the amplification circuit 11. The signal of the reflected wave amplified by the amplification circuit 11 is demodulated by the detection circuit 12, amplified again by the amplification circuit 13, and sent to the detection operation control circuit 2.

The detection operation control circuit 2 has two control modes, a low sensitivity mode and a high sensitivity mode. The detection operation control circuit 2 switches between the two modes for each one-shot transmission of ultrasonic waves, and performs detection control by ultrasonic waves. It is supposed to do. Here, the low sensitivity mode is for detecting a short distance, and the high sensitivity mode is for detecting a long distance. The sensitivity switching circuit 14 switches between such a low-sensitivity mode and a high-sensitivity mode.
In addition, by controlling the amplifier circuit 13, the pulse width at the time of transmitting the ultrasonic wave and the amplification degree at the time of receiving the ultrasonic wave are switched. The technique of performing detection while switching between the low-sensitivity mode and the high-sensitivity mode has already been presented by the applicant in Japanese Patent Application No. 7-155294. When detecting the distance of the detection target, the detection operation control circuit 2 sets the dead zone when the detected distance is included in the dead zone area set by the dead zone setting switch 3. The detection circuit 12 is controlled via the execution circuit 15 to cut off the reflected wave so that the object in the dead zone area is not detected.

The power supply circuit 16 supplies power to each circuit shown in FIG. 1 and other circuits not shown. The relay drive circuit 17 drives various control devices on the user side. It is for.

FIG. 2 shows the detection operation control circuit 2 shown in FIG.
5 is a flowchart showing main control operations of the first embodiment. The detection operation control circuit 2 first performs an initial setting (step 5).
1) In this initial setting, the upper limit and the lower limit of the dead zone previously written in the rewritable nonvolatile memory 4 are read. Next, the firing program is executed (step 52), and the ambient temperature is read from the temperature detector 6 to perform temperature compensation of the dead zone (step 53). The temperature compensation of the dead zone will be described later with reference to FIG. Thereafter, the detection operation control circuit 2 determines whether or not the detection distance calculated based on the reflected wave from the detection target is a distance included in the dead zone, and based on this determination, the reflection input by the detection circuit 12 is performed. The processing of cutting or not cutting the wave signal is performed via the dead zone setting execution circuit 15 (step 54). If the cut has not been made, the previously calculated distance is determined as the final reflected wave measurement distance (step 55), and the distance is displayed on the display 5. Thus, after the first ultrasonic pulse is emitted and received, the process returns to step 51 and the emission and reception of the second and subsequent ultrasonic pulses are repeated.

Next, the temperature compensation of the dead zone in step 53 will be described with reference to FIG. Generally, the propagation speed of an ultrasonic wave varies depending on the ambient temperature. Particularly, in a container such as a chemical device, the temperature change is large, so that the necessity of performing temperature compensation of a dead zone increases. In the present embodiment, as shown in FIG.
° C and correction coefficients δ1, δ2, ... δ90, δ for each temperature.
91 is set and stored in a memory not shown.

The detection operation control circuit 2 first samples the detected temperature from the temperature detector 6 at a predetermined cycle (step 101) and determines the current temperature (step 102).
Then, a correction coefficient corresponding to the determined temperature is obtained from FIG. 4 (step 103). Next, the obtained correction coefficient is multiplied by the currently set upper limit value and lower limit value, respectively (steps 104 and 105), and is corrected to the upper limit value and the lower limit value suitable for the ambient temperature in the container. in this way,
In the present embodiment, since the upper limit value and the lower limit value are corrected for each one-shot of the ultrasonic pulse, the dead zone region is always appropriately set even in a container such as a chemical device where a rapid temperature change occurs. Can be.

Next, the control contents in the distance determination in step 55 will be described in detail with reference to the flowchart of FIG. First, the detection operation control circuit 2 converts a detection distance previously calculated from a reflected wave from the detection target into a temperature-corrected distance (step 71). This temperature correction can be performed in substantially the same manner as the temperature correction of the dead zone described with reference to FIG.

Then, it is determined whether the current distance detection is performed in the low-sensitivity mode or in the high-sensitivity mode (step 72). (Steps 73 to 7)
5) If the mode is the high sensitivity mode, a correction process for the high sensitivity mode is performed (steps 76 to 78).

That is, if it is determined in step 72 that the mode is the low sensitivity mode, it is determined whether or not the falling part of the pulse of the reflected wave matches the upper limit of the dead zone (step 73). This is because whether or not the detection distance belongs to the dead zone is determined by whether or not the falling part of the pulse of the reflected wave belongs to the dead zone. If the falling portion of the pulse of the reflected wave coincides with the upper limit value of the dead zone, the previously detected detection distance is not corrected (step 74). This is because the correction in this case is performed according to the pulse width, but the pulse width cannot be detected accurately because the falling part of the pulse enters the dead zone. On the other hand, if the falling part of the pulse of the reflected wave does not match the upper limit of the dead band, the detection distance previously detected does not belong to the dead band region but belongs to the detectable region. Then, the detection distance is corrected according to the pulse width (step 75).

Steps 76-78 also include steps 73-75
The description is omitted here. Note that the correction processing in steps 73 to 78 is performed to correct an error in the detection distance generated due to a vibration delay on the ultrasonic vibration surface of the detection target. The technical contents of the correction processing are disclosed in another application. Therefore, the details of the content of the correction processing are omitted here.

Next, after completing the low sensitivity mode correction processing, it is determined whether or not the obtained detection distance is within the low sensitivity mode detectable area (step 79). The processing is performed on the assumption that the detection target has been detected (step 80). On the other hand, if the obtained detection distance is not within the detectable area of the low-sensitivity mode, the detection distance is not finally adopted and is left to the detection operation in the low-sensitivity mode or the high-sensitivity mode for the next and subsequent times. become.

After completion of the correction processing in the high sensitivity mode, it is determined whether or not the obtained detection distance is within the detectable area of the high sensitivity mode (step 81). Further, it is determined whether or not the detected object is also present in the detectable area in the low sensitivity mode (step 82). If the detected object does not exist in the detectable area in the low-sensitivity mode, the processing is performed assuming that the detection target is not detected (step 83). If there is, since the detection is performed in the high sensitivity mode this time, this detection distance is not finally adopted, and is left to the detection operation in the next and subsequent low sensitivity modes.

If it is determined in step 81 that the obtained detection distance is within the detectable area in the high sensitivity mode, it is further determined whether or not the detected object is also present in the detectable area in the low sensitivity mode. Is determined (step 84).
If the detected object is also within the detectable area of the low-sensitivity mode, the detection operation in the low-sensitivity mode is prioritized. Try to adopt distance. On the other hand, if the detected object does not exist in the detectable area in the low sensitivity mode, the process is performed assuming that the detection target is detected (step 80). In the above example, if the determination in step 81 is YES, step 84 is interposed to give priority to the low-sensitivity mode detection operation. However, step 84 can be omitted. .

Next, the dead zone processing of the ultrasonic level sensor according to the present embodiment will be specifically described with reference to the explanatory diagram of FIG. 6 and the flowchart of FIG. The ultrasonic level sensor according to the present embodiment is 40 to 300 in the low sensitivity mode.
cm, in the high sensitivity mode, a detectable area of 80 to 300 cm. As described above, since the detectable area is smaller in the high-sensitivity mode, the detection operation control circuit 2 according to the position of the dead zone with reference to the position of 80 cm.
Needs to perform dead zone processing. FIG. 6A shows a case where both the upper limit and the lower limit are shorter than 80 cm (upper limit: 5).
0 cm, lower limit: 70 cm), and FIG. 6B shows a case where both the upper limit and the lower limit are longer than 80 cm (the upper limit: 110).
cm, lower limit: 140 cm), and FIG.
The case where the length is shorter than 0 cm and the lower limit is longer than 80 cm (upper limit: 60 cm, lower limit: 100 cm) is shown. In the present embodiment, the shorter distance, that is, the side closer to the sensor is set as the upper limit value, and the longer distance is set as the lower limit value. Considering the value of the detection distance as a reference, the shorter distance should be originally referred to as the lower limit, and the longer distance should be referred to as the upper limit. Considering the positional relationship between the upper and lower sides of the liquid surface as a reference, the shorter distance is used as the upper limit.

In this embodiment, when the dead zone is set, the detectable area is set to a distance up to 2 × the upper limit. This takes into account the case where multiple reflections of ultrasonic waves occur. That is, for example, assuming that an obstacle is disposed at a position of 60 cm and the ultrasonic wave is reflected twice on the obstacle, the sensor detects the position of the obstacle in this case as 120 cm, and actually, the sensor detects the position of the obstacle. An obstacle that is arranged in the dead zone and should not be detected is detected. In order to prevent such a situation, in the present embodiment, the 2 × upper limit is set as the maximum value of the detectable area.

First, the operation will be described in order from the case where the dead zone is set as shown in FIG. Detection operation control circuit 2
Determines whether the control mode that emitted the current ultrasonic wave is the low sensitivity mode or the high sensitivity mode (step 1). If the control mode is the low sensitivity mode, determines whether the distance calculated by the reflected wave is shorter than 40 cm. (Step 2). If the distance is shorter than 40 cm, the reflected wave is cut because the distance belongs to the detection prohibited area (step 3).

If it is determined in step 2 that the distance is longer than 40 cm, then it is determined whether the distance is shorter than the upper limit (50 cm) (step 4). If the distance is shorter than the upper limit, the reflected wave is measured as it is because the distance belongs to the detectable area (step 5). Step 4
If it is determined that the distance is longer than the upper limit value, it is further determined whether or not this distance is shorter than the lower limit value (70 cm) (step 6). If the distance is shorter than the lower limit, the reflected wave is cut because the distance belongs to the dead zone (step 7).

If it is determined in step 6 that the distance is longer than the lower limit, it is next determined whether the distance is shorter than 2 × the upper limit (100 cm) (step 8). If it is shorter than 2 x upper limit, this distance belongs to the detectable area,
This reflected wave is measured as it is (step 5).
If the length is longer than the upper limit value, this area belongs to a detection prohibited area in consideration of multiple reflection, and therefore, this reflected wave is cut (step 7).

If it is determined in step 1 that the current control mode is the high sensitivity mode, the detection operation control circuit 2 determines whether the lower limit of the dead zone is shorter than 80 cm (step 9). In this case, since the lower limit is 70 cm, it is naturally determined that the distance is shorter than 80 cm. In this case, it is further determined whether or not the calculated distance is shorter than 80 cm (step 10). Cuts the reflected wave because it belongs to the detection prohibited area in the high sensitivity mode (step 11).

If it is determined in step 10 that the distance is longer than 80 cm, it is further determined whether or not this distance is shorter than 2 × the upper limit (step 12). If the distance is shorter than 2 × the upper limit, the reflected wave is measured as it is because the distance belongs to the detectable area (step 13).
X If the length is longer than the upper limit, this area belongs to the detection prohibited area, so this reflected wave is cut (step 1).
1).

Next, a case where a dead zone is set as shown in FIG. 6B will be described. In this case, step 1
6 to 8 are the same as in the case of FIG.
Since it is set to 40 cm, the determination in step 9 is NO. Next, the detection operation control circuit 2 further determines whether or not the upper limit value is longer than 80 cm (step 14). In this case, since the upper limit value is set to 110 cm, this determination is YES.

Then, it is determined whether or not the calculated distance is shorter than 80 cm (step 15). If the calculated distance is shorter, the reflected wave is cut off because this area belongs to the detection prohibited area (step 11). If it is determined that the distance is longer than 80 cm, it is further determined whether this distance is shorter than the upper limit (110 cm) (step 16). If the distance is shorter than the upper limit value, the reflected wave is measured as it is because the distance belongs to the detectable area (step 13). If the distance is longer than the upper limit, it is further determined whether or not the distance is shorter than the lower limit (step 17). If the distance is shorter, the reflected wave is cut off because the distance belongs to the dead zone (step 1).
1).

At step 17, the distance is set to the lower limit (140c
m), it is determined that the length is longer than 2 × the upper limit (22
0 cm) is determined (step 18).
If the distance is shorter than 2 × the upper limit, the reflected wave is measured as it is because the distance belongs to the detectable area (step 1).
3) If the distance is longer than 2 × upper limit, the reflected wave is cut because the distance belongs to the detection prohibited area (step 11).

Next, a case where a dead zone is set as shown in FIG. 6C will be described. In this case, step 1
6 to 9 are the same as in the case of FIG.
Since it is set to 0 cm, the determination in step 14 is NO. Next, if the calculated distance is shorter than the lower limit (100 cm), the detection operation control circuit 2 determines that the distance always belongs to either the dead zone or the detection prohibited zone. Is cut (step 20).

If it is determined in step 19 that the distance is longer than the lower limit, the distance is further increased by 2 × the upper limit (120 cm).
It is determined whether or not it is shorter than (step 21). If the distance is shorter than 2 × the upper limit, this distance belongs to the detectable area, so the reflected wave is measured as it is (step 22),
If the distance is longer than 2 × the upper limit, this distance belongs to the detection prohibited area, and the reflected wave is cut (step 2).
0).

According to the above-described ultrasonic level sensor, the setting of the dead zone can be easily performed only by operating the dead zone setting switch 3 while watching the numerical value digitally displayed on the display 5. Therefore, the user can easily reset the dead zone after the change of the obstacle arrangement status by himself / herself, which has conventionally relied on the sensor maker.

It should be noted that the upper limit and lower limit of the dead zone and the numerical values of the detectable area in the description of the above embodiment are, of course, used for convenience of description, and these numerical values can be variously changed. Needless to say, In addition, an ultrasonic level sensor is taken as an example of an ultrasonic sensor, and the case where the detection target is a liquid surface in a container such as a chemical device has been described. You can think of things.

[0038]

As described above, according to the present invention, the user can set the dead zone with his / her own hand by a simple operation. Therefore, it is possible to easily and quickly cope with a change in the arrangement state of the obstacles after the sensor is mounted.

Further, the detection operation control circuit in the sensor of the present invention has a function of maintaining switching control between the low sensitivity mode and the high sensitivity mode regardless of the setting of the dead band, and a function of performing temperature compensation of the dead band. Since a function for preventing erroneous detection due to multiple reflection can be added, a more accurate detection operation can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ultrasonic level sensor according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining a main control operation of a detection operation control circuit 2 in FIG. 1;

FIG. 3 is a flowchart for explaining temperature compensation of a dead zone in FIG. 2;

FIG. 4 is a chart showing a relationship between an ambient temperature of a non-sensing zone and a correction coefficient of the non-sensing zone.

FIG. 5 is a flowchart illustrating a control operation for determining a distance in FIG. 2;

FIG. 6 is an explanatory diagram showing a setting area of a dead zone in the embodiment of the present invention.

FIG. 7 is a flowchart for explaining dead zone processing in the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 CPU 2 detection operation control circuit 3 dead zone setting switch 4 rewritable nonvolatile memory 5 display 6 temperature detector 7 reference pulse generation circuit 8 pulse modulator 9 sensor drive circuit 10 ultrasonic transmission / reception unit 11 amplification circuit 12 detection circuit 13 Amplifier circuit 14 Sensitivity switching circuit 15 Dead zone setting execution circuit 16 Power supply circuit 17 Relay drive circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Etsuo Terui 4-1-1-18 Yushima, Bunkyo-ku, Tokyo Inside Kandenko Co., Ltd. (72) Inventor Haruo Ishii 3-chome Nishishinbashi, Minato-ku, Tokyo No. 20-4 Tokyo Denki Service Co., Ltd.

Claims (4)

[Claims] An ultrasonic wave is transmitted toward an object to be detected, a reflected wave is detected, and the time from the ultrasonic wave transmission time to the reflected wave detection time is measured to determine the position of the object to be detected. In the ultrasonic sensor to detect, a dead zone setting switch for setting a dead zone for the reflected wave detection, and a display for displaying an area of the dead zone set by the dead zone setting switch, A detection operation control circuit for controlling a detection operation so that a reflected wave from an obstacle existing in an area of the dead zone set by the dead zone setting switch is not detected. Sound wave sensor. 2. The ultrasonic sensor according to claim 1, wherein the control mode of the detection operation control circuit includes a low sensitivity mode and a high sensitivity mode divided according to a detection distance. An ultrasonic sensor, wherein the detection operation is controlled by alternately switching between the two modes. 3. The ultrasonic sensor according to claim 1, wherein the detection operation control circuit temperature-compensates a value of a non-sensing band region set based on an input of an atmosphere detection temperature. An ultrasonic sensor characterized by the above-mentioned. 4. The ultrasonic sensor according to claim 1, wherein the dead zone is an area formed between an upper limit and a lower limit, and the upper limit is higher than the lower limit. Is also close to the sensor side, and the detection operation control circuit performs a detection process using a region farther than a position of a value twice the upper limit value of the dead zone as a detection prohibition region. Ultrasonic sensor featuring.