JP6843699B2 - Identification device and identification method - Google Patents

Description

The present invention relates to an identification device and an identification method for identifying a work on a transport line. More specifically, when a plurality of types of workpieces having different specifications are mixed and conveyed on a transfer line, the identification device and identification method for identifying the workpieces for each specification (or type) are particularly non-contact. Suitable for what you do.

In recent years, customers' demands for product specifications have been diversified, and in order to meet the diversified demands, cases where product specifications differ depending on the destination of the product are increasing. At the same time, new models have been added to meet the needs of users, and the number of product types is increasing.

Therefore, there is an urgent need to remodel conventional equipment that has been used for low-mix, high-volume production to manufacture small-lot, high-mix models (high-mix low-volume production) without lowering the operating rate.

There are various problems when manufacturing a wide variety of products by mixing them with conventional equipment (lines), but the most important problem is to correctly determine multiple types of workpieces flowing through the line (for example, an assembly line). Then, it is definitely necessary to carry out different assembly or processing work for each type of product.

For example, an automobile engine manufacturing factory has a transport line for cylinder blocks such as castings, and in many cases, a plurality of types of cylinder blocks coexist and flow as workpieces on this transport line. Therefore, at the inlet or outlet of such a transport line, it is necessary to determine the type of cylinder block and sort it according to the type. Then, what is generally used is to form a bar code having a convex portion on a casting or the like flowing through a transport line instead of a contact type displacement sensor, and irradiate this bar code with light diagonally from a light emitting source. It is known that a shadow of a barcode is formed, and the shadow is photographed by a TV camera to perform predetermined information processing to determine the type of the casting or the like.

In addition, a bar code consisting of convex parts is integrally cast on the outer peripheral surface of the cylinder block, which is the casting to be discriminated, by a reference bar, and the model number, mold number, etc. are expressed by the number of convex parts and the distance between them. It is being detected by a TV camera.

Further, in order to reduce the number of integrally cast convex portions, that is, the number of reference bars, the width and height of the bar are obtained to determine the casting, etc., and the height or width of the bar is changed for each type of casting, etc. It is known that a plurality of types of castings and the like can be discriminated from each other, and for example, it is described in Patent Document 1.

In addition, it is known that the distance to the work surface is determined by the displacement laser sensor, which is an optical measuring device, to determine the presence or absence of blind holes on the work surface and their positions in order to correctly identify various types of work to be put on the conveyor. For example, it is described in Patent Document 2.

Further, it is known that by optically inspecting the outer shape in a non-contact manner instead of the contact type displacement sensor, the detection can be performed with high accuracy without being adversely affected by the displacement of the work, for example, Patent Document 3. It is described in.
Furthermore, in the ultrasonic sensor, in order to avoid erroneous detection due to the difference in the amount of reflection and transmission of ultrasonic waves depending on the material of the object and to enable stable detection, the ultrasonic waves are reflected from the timing of irradiation. The distance calculation unit calculates the distance to the object based on the time until the wave is detected, and the type of the object is detected based on the calculated distance and the received amount received by the ultrasonic transmission / reception unit. It is known, for example, described in Patent Document 4.

Japanese Unexamined Patent Publication No. 8-287175 Japanese Unexamined Patent Publication No. 2008-1197886 Japanese Unexamined Patent Publication No. 2004-294095 Japanese Unexamined Patent Publication No. 2006-292634

In the above-mentioned prior art, in the case where the workpiece is discriminated by the contact type during the assembly or processing transfer line, not only is it difficult to detect the workpiece with high accuracy due to the displacement of the workpiece, but also there is a risk of failure or destruction due to impact. Yes, not realistic.

Further, those using an optical TV camera and a displacement laser sensor are affected by the environment in which the transport line is placed. For example, in machine tools such as machining centers that have an automatic tool change function and perform different types of machining such as milling, boring, drilling, and threading according to the purpose, it is necessary to identify the model immediately before machining. In the formula, in the environment of oil mist or dust which is fine particles, light and laser are diffused due to the influence, and accurate discrimination is difficult, and it is extremely difficult to discriminate multiple models.

Furthermore, when an eddy current displacement sensor that uses a high-frequency magnetic field that is said to be resistant to dust, water, oil, etc. is used, the accuracy and response speed are fast, but the measurable distance is as short as a few mm, and the machining center, etc. Not suitable for use in transport lines.

Furthermore, the one using an ultrasonic displacement sensor using sound waves as a medium is suitable for use in a transport line because the measurement distance is long, but the accuracy is low compared to other methods just by using it, and the measurement surface. The size of the work had to be increased, and in order to distinguish between multiple models, the measurement surface of the workpiece had to be increased accordingly.
In particular, when discriminating multiple models using an ultrasonic displacement sensor, a threshold value is set for each model and the rank is compared with the arrival time in order to discriminate using the arrival time of ultrasonic waves reflected on the work surface. It is discriminating.

Further, the one described in Patent Document 4 simply sets the threshold value of the received amount and the threshold value of the distance as the threshold values in advance in the setting unit for identification, and considers that the arrival time varies depending on the measurement environment. Not. Therefore, even if each threshold value is specified as a constant value and is set in a range, it is difficult to discriminate between multiple models, especially depending on the measurement environment such as temperature. In particular, if a value is set as a threshold value in a range that simply allows variation, the threshold value has a margin more than necessary. In that case, it is necessary to reduce the number of models that can be discriminated when discriminating a plurality of models.

An object of the present invention is to solve the above-mentioned problems of the prior art and to convey a plurality of types of workpieces in a mixed manner on an assembly or processing transfer line, or even in an environment where oil mist or dust is present. The purpose is to reliably determine the type at the entrance or exit of the line. In particular, in the cylinder block transfer line in an automobile engine manufacturing factory, the work of discriminating many models, changing the processing for each model, and sorting for each model becomes more accurate and reliability is improved. There is.

In order to achieve the above object, the identification device of the present invention is an identification device for identifying the type of an article provided with an identification unit at a predetermined position, and transmits ultrasonic waves to the identification unit to receive reflected waves. A master sensor and a slave sensor for measuring the time from transmission to reception are provided, and the type of the article is discriminated by using the difference between the values measured by the master sensor and the slave sensor.

Since the type of article is determined using the difference between the values measured by the master sensor and the slave sensor, the effects of temperature, oil mist, dust, etc. in measuring the distance from the sensor to the identification unit should be offset. Can be done. Therefore, even in an environment such as a cylinder block manufacturing line, it is possible to accurately determine the types of many articles with a sufficient operating distance that does not interfere with processing.

Further, in the above, the master sensor and the slave sensor are arranged at positions facing the identification unit, and the surface of the identification unit facing the master sensor and the surface of the identification unit facing the slave sensor It is desirable to determine the type of the article by detecting the step.

As a result, the measurement range can be clarified by making the identification portion a step, and it becomes possible to discriminate more types of articles.
Further, in the above, it is desirable that the ultrasonic waves are transmitted alternately between the master sensor and the slave sensor.
It is possible to prevent ultrasonic waves from interfering with each other in the master sensor and the slave sensor.

Further, in the above, it is desirable that the oscillation frequency of the ultrasonic wave is 200 to 400 kHz.
As a result, the beam size of the ultrasonic wave can be reduced and the area of the identification portion can be reduced.

Further, in the above, it is desirable that the master sensor generates a clock signal serving as a reference time for transmitting ultrasonic waves, and the slave sensor transmits ultrasonic waves in synchronization with the clock signal.
Even if the measurement is repeated many times, interference can be avoided for a long time without shifting the ultrasonic transmission timing.

Further, in the above, it is desirable that the distance from the master sensor and the slave sensor to the identification unit is 150 to 200 mm.
In the cylinder block manufacturing line, since it is not necessary to bring the sensors close to each other, it is easy to control the position where the article is stopped, and the sensor position does not hinder the processing.

Further, in the above items, the article may be a cylinder block, and the transport line may be used for processing the cylinder block.
In the manufacturing process of the cylinder block, it can be suitable in terms of environment, accuracy, measurement area and the like.

Further, in the above items, it is desirable to identify the type of the article by measuring the step, which is changed by a predetermined amount for each type of the article.
Thereby, the number of discrimination of the type of the article can be increased.

According to the present invention, the master sensor and the slave sensor transmit ultrasonic waves to the identification unit provided at a predetermined position of the article, and measure the time from the transmission to the reception of the reflected wave. Since the type of the article is determined by using the difference in values, the type of the article can be reliably determined without being affected by the temperature, oil mist, dust, and the like. In particular, in a cylinder block transfer line in an automobile engine manufacturing factory, it is possible to accurately determine the types of a plurality of articles and improve reliability.

A block diagram showing a case where the work identification device according to the embodiment of the present invention is applied to a machine tool or the like. Block diagram showing discrimination processing in one embodiment Explanatory drawing showing identification shape and processing of work in one Embodiment Explanatory drawing which shows assignment (mastering) of work number in one Embodiment Explanatory drawing which shows determination of work number in one Embodiment Graph showing the relationship between the beam spot diameter of the ultrasonic displacement sensor and the oscillation frequency and distance Graph showing the relationship between the energy density of the ultrasonic displacement sensor and the oscillation frequency and distance A graph showing the relationship between the beam spot diameter of the ultrasonic displacement sensor in one embodiment, the oscillation frequency, and the distance. Graph showing output value vs. time in conventional ultrasonic displacement sensor Graph showing output value vs. time in ultrasonic displacement sensor in one embodiment Explanatory drawing of discriminant effect on temperature change in ultrasonic displacement sensor in one Embodiment Explanatory drawing which shows measurement interval in ultrasonic type displacement sensor in one Embodiment A flowchart showing a method of setting a threshold value in one embodiment. A graph showing the threshold allocation state for each work number in one embodiment.

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

In the production of automobiles, it is desired to produce a large number of models in small quantities in order to meet the diversifying needs of consumers for automobiles. Under such multi-model low-volume production, it is possible to support multiple models rather than assembling products on a dedicated line for each model from the viewpoints of production efficiency, the total length of the line, the cost of incidental equipment, and the operating rate of the line. It is preferable to assemble the product on a multi-model mixed line that can be used. However, the types of work required for assembling the product, the man-hours required for completing the product, the time required for each work, and the like differ greatly depending on the model.

FIG. 1 shows a configuration diagram in which a work identification device according to an embodiment of the present invention is applied to a machining center which is a machine tool. Reference numeral 6 denotes a work, which is a cylinder block in which a plurality of pistons are accommodated and a crankshaft is attached to a lower crankcase portion.

A cast iron or aluminum alloy cast product is generally used for the cylinder block, and various types of workpieces 6 are mixed and put into the transport line. An automobile engine manufacturing factory has a cylinder block transport line, and in many cases, a plurality of types of cylinder blocks coexist as workpieces in this transport line. Therefore, at the inlet or outlet of such a transport line, it is necessary to identify the model that is the type of cylinder block.

The machining center is a numerically controlled machine tool that performs various machining such as milling, drilling, boring, and screwing without changing the mounting of the workpiece. In FIG. 1, for example, 5 is drilling. It is a machine tool. Further, the tool magazine stores a large number of cutting tools, automatically performs machining by a command of computer numerical control, and has an automatic tool changing device. Further, there are known ones in which a work table can be rotated at a high speed and a cutting tool can be attached to a spindle for turning, a grinding wheel can be used instead of a milling tool, and a probe for measuring dimensions can be mounted. Since the main purpose is processing, therefore, in the environment where the machining center is installed, fine particles of oil mist and dust are present, and an ultrasonic displacement sensor is used to discriminate castings such as cylinder blocks among them. Is desirable.

The cylinder block, which is the work 6, is placed on the transport line and is fed in the direction of arrow A to stop. Reference numeral 1 and 2 are ultrasonic displacement sensors, 1 is a master sensor, 2 is a slave sensor, and ultrasonic waves are transmitted to an identification unit provided at a predetermined position of the work 6 at a position where the work 6 is stopped. The reflected wave is received to determine the model.

Reference numeral 3 denotes a sensor unit that performs measurement and discrimination by the master sensor 1 and the slave sensor 2, receives an instruction to start measurement from the machine tool controller 4, and transmits the discrimination result. After receiving the determination result, the machine tool controller 4 instructs the work 6 to move to the processable position indicated by the broken line. Then, the discrimination result received from the sensor unit 3, that is, the machine tool 5 is instructed to perform processing depending on the model. The machining instructions are, for example, the hole size and position as specifications in drilling, and the rotation speed and the like as machining conditions.

Here, ultrasonic waves have excellent focusing and directivity, and because they are sparse and dense waves of air, the influence of scattering by fine particles in the air is smaller than that of the optical type, and the oil mist and dust on which the machine tool 5 is installed Stable measurement is possible even in an environment. In addition, if ultrasonic waves are used, measurement of all materials such as metal, wood, glass, rubber, powder, and liquid can be performed non-contact as the object to be measured (work 6), and the work 6 to several hundred mm. It can be done over long distances.

The ultrasonic displacement sensor transmits ultrasonic waves toward an object by a transmitter and receives the reflected waves by a receiver to detect the presence or absence of the object and the distance to the object. An ultrasonic element is used to transmit and receive ultrasonic waves. The ultrasonic element is an element that applies electric energy to generate ultrasonic waves or converts ultrasonic vibration energy into an electric signal. A barium titanate oscillator utilizing a piezoelectric phenomenon can be used.

The piezoelectric element vibrates when an AC voltage is applied, has a unique frequency, and vibrates efficiently by applying an AC voltage of the same frequency as that frequency. Generally, 40 kHz is often used, a low frequency is used for measuring a long distance, and a high frequency is used for accurately measuring a short distance.

In addition, the ultrasonic displacement sensor can measure all materials such as metal, wood, glass, rubber, powder, and liquid, and since it is non-contact, there is no problem of viscosity or corrosion. It has features such as long-distance detection, which does not interfere with moving objects on the transport line, and stable level measurement in adverse environments.

Further, the ultrasonic displacement sensor measures the length by measuring the time from the transmission of the sound wave to the reception. Therefore, the ultrasonic displacement sensor is stable because it is not affected by the surface roughness unlike the optical type because the arrival time does not change even if the surface roughness of the object to be measured is large or the intensity changes. Measurement is possible. In particular, when the work 6 is a cast cylinder block, this advantage can be utilized, and even when the cylinder block has heat, it is not affected.

In addition, the speed of sound in the air changes depending on the air temperature, and the measurement results of the ultrasonic displacement sensor are affected by changes in the atmosphere. Therefore, each of the master sensor 1 and the slave sensor 2 is an ultrasonic displacement sensor that measures the time from transmission to reception, and the sensor unit 3 uses the difference between the measured values of the master sensor 1 and the slave sensor 2. Make a judgment.

Since the model is determined using the difference between the values measured by the master sensor 1 and the slave sensor 2, the temperature, oil mist, dust, etc. at the distance from the master sensor 1 and the slave sensor 2 to the identification part of the work 6 are determined. The impact can be offset. Therefore, even in an environment such as a cylinder block manufacturing line, many models can be accurately identified with a sufficient operating distance that does not interfere with processing.

FIG. 2 is a block diagram showing a discrimination process, and each of the master sensor 1 and the slave sensor 2 has a configuration capable of measuring the distance to the work 6. FIG. 3 shows the shape of the identification portion that is the measurement surface of the work 6. The shape of the identification portion is integrated with the work 6, and a step is provided between the surface facing the master sensor 1 and the surface facing the slave sensor 2, and the unevenness thereof is several mm.

In the measurement, the measurement surface must face the master sensor 1 and the slave sensor 2 at the stop position of the work 6 as shown in FIG. 3, and the size of the measurement surface is the stop position accuracy and the ultrasonic displacement sensor. Determined by beam size. However, the cylinder block is a casting and is required to have a smaller measurement area. By making the identification unit a step, the measurement range can be clarified and more models can be identified.

Further, by taking the difference between the measured values of the master sensor 1 and the slave sensor 2, the length measurement process between the sensor and the work 6 is canceled, and the measurement is limited to the unevenness only. Further, if two ultrasonic sensors are simply used side by side, the sound waves interfere with each other, resulting in a measurement error. However, the master sensor 1 and the slave sensor 2 alternately oscillate ultrasonic waves so as to avoid interference. Therefore, it is possible to prevent the master sensor 1 and the slave sensor 2 from interfering with each other by ultrasonic waves.

As shown in FIG. 2, the master sensor 1 and the slave sensor 2 have the same configuration, have ultrasonic elements 31 and 32, respectively, and are switched by the CPUs 33 and 34 to perform transmission and reception. The memories 35 and 36 temporarily store the measurement data, and the CPU 33 and 34 control the storage and reading. The master sensor 1 and the slave sensor 2 are connected to each other, and the ultrasonic element 32 of the slave sensor 2 oscillates in synchronization with the clock signal generated by the master sensor 1. The measurement data of the slave sensor 2 is transmitted to the CPU 33 of the master sensor 1. As a result, even if the measurement is repeated many times, the transmission timing of the ultrasonic waves does not shift, and interference can be avoided for a long time.

The configuration shown in FIG. 2 is an example, and any configuration can be adopted as long as it exhibits the same function. For example, instead of using two CPUs of CPUs 33 and 34, it is possible to adopt a configuration in which one CPU controls the master sensor 1 and the master sensor 2, or one memory can be used for the master sensor 1 and the master sensor. A configuration in which 2 is operated may be adopted.

The CPU 33 of the master sensor 1 is connected to the machine tool controller 4, the machine tool controller 4 instructs the start of measurement, and the determination result is transmitted from the CPU 33 to the machine tool controller 4. After receiving the discrimination result, the machine tool controller 4 moves and stops the work 6, and gives a machining instruction to the machine tool 5 according to the discrimination result.

In order to avoid interference, the master sensor 1 and the slave sensor 2 generate a clock signal that serves as a reference time for transmitting ultrasonic waves in the master sensor 1, and the slave sensor 2 synchronizes with the generated clock signal on the master sensor 1 side. The master sensor 1 and the slave sensor 2 alternately oscillate so as to transmit ultrasonic waves, and the oscillation / transmission interval is set to a time sufficient to eliminate the reverberation due to the reflected wave from the work 6. Since the reverberation due to the reflected wave depends on the operating distance between the master sensor 1, the slave sensor 2 and the work 6, the operating distance is determined by setting the transmission (transmission) interval.

The measurement is started by first transmitting ultrasonic waves from the ultrasonic element 31 of the master sensor 1 and then transmitting ultrasonic waves from the ultrasonic element 32 of the slave sensor 2. This is set as one set, and after repeating a predetermined number of sets, transmission is stopped. As shown in FIG. 3, the identification shape serving as the measurement surface of the work 6 is an uneven pattern shape provided on the surface. In the example of FIG. 3, the distance from the master sensor 1 to the work 6 is 200 mm as the operating distance, the distance from the slave sensor 2 to the work 6 is 197 mm, and the slave sensor 2 side has a convex step toward the ultrasonic displacement sensor side of 3 mm. It has become.

The value of the step is preferably about 1/40 to 1/200 of the operating distance from the viewpoint of measurement error and the like. As a result, the resolution of the sensor can be ensured even when the number of models to be discriminated is large. Ultrasonic waves are transmitted from the ultrasonic element 31 of the master sensor 1, and the time until the reflected wave from the recess of the work 6 reaches the master sensor 1 is counted as measurement data and stored in the memory 35. Next, ultrasonic waves are transmitted from the ultrasonic element 32 of the slave sensor 2 at different timings so as not to interfere with each other, and the time until the reflected wave returns to the slave sensor 2 is counted and stored in the memory 36.

After the transmission is stopped, the slave sensor 2 outputs the measurement data stored in the master sensor 1. The master sensor 1 calculates the difference between its own measurement data stored in the memory 35 and the measurement data output from the slave sensor 2. Then, the CPU 33 of the master sensor 1 determines that the slave sensor 2 side is convex by 3 mm as the pattern of the measurement surface.

FIG. 4 is an explanatory diagram illustrating a mode (mastering mode) in which a threshold value as a reference for assigning a work number and determining is stored in a memory 35. For the cylinder block mounted on the transport line to be actually measured, a reference master work 11 is separately prepared for the required type and set in the master sensor 1 and the slave sensor 2. The measuring unit places the master work 11 corresponding to the work number 1 on the transport line of the work to be actually measured, and measures the master work 11. The read difference value between the master sensor 1 and the slave sensor 2 is stored, and is associated with the work number 1 and registered as the work number 1 in the discrimination data table 12 which is a reference for the discrimination as shown in the figure. The discrimination data table 12 is stored in the memory 35 of the master sensor 1 as a table structure.

Further, since the arrival time varies depending on the measurement environment, the measuring unit performs a plurality of measurements on the master work 11 corresponding to each work number. It is desirable to set the threshold value with a predetermined range from the statistics of the obtained data group in order to increase the number of discriminating models.

FIG. 5 is an explanatory diagram for explaining the discrimination mode in which the work number is discriminated and the cylinder block (work 6) placed on the transport line is measured and discriminated. The work 6 is measured as described above, and the difference value between the measured master sensor 1 and the slave sensor 2 is compared with the discrimination data table 12 to obtain a matching work number. If it matches the work number 1, the machine tool controller 4 is output that the work number is 1. The machine tool controller 4 executes a machining instruction or the like according to the work number 1.

The identification shape of the work 6 as the measurement surface is such that the slave sensor 2 side is convex toward the master sensor 1 side by 3 mm toward the ultrasonic displacement sensor side. Work numbers are assigned in 4 steps of 1 mm each.

Since the cylinder block is a casting made by pouring metal into a mold, it is not possible to obtain the accuracy of 0.1 mm or 0.01 mm required for machined metal products, and the metal taken out from the mold is Since it is rough and uneven, the predetermined amount for stepping the step is preferably 0.7 to 1.4 mm, preferably about 1 mm. This facilitates the manufacture of the cylinder block even if the number of model identifications increases.

It is possible to identify four types of patterns in which the slave sensor 2 side is convex, such as work numbers 1 and 4 mm for steps 3 mm, work numbers 2 and 2 mm for 2 mm, and work numbers 3 and 1 mm for 1 mm. At this time, it is desirable that the work numbers are not assigned in the order of the size of the steps, but are close to the center value of the steps for which the work numbers of a large number of models are set. That is, when there are many models with the work number 1, it is preferable to assign it to 3 mm, which is close to the center value of the step (the center value in the case of 5 steps).
The reason is that it is more reliable to distinguish large steps than to distinguish small steps. For example, it is more reliable to identify 3 mm and 5 mm as a step than to identify 5 mm and 4 mm. Therefore, exception determination can be easily performed by assigning a large number of models to the center value of the step, for example, 3 mm, and assigning an exceptional model to 5 mm.

Further, as another pattern, the master work 11 is prepared in which the unevenness is reversed, the master sensor 1 side is convex with respect to the slave sensor 2 side, and the step is similarly changed. Thereby, 4 × 4 = 16 types of models can be discriminated. Thus, it is possible to reduce the input and output lines of the master sensor 1 and the machine tool controller 4 4 bits (2 ^{4 =} 16 types compatible with 4 bits) and. Of course, in order to increase the number of model discriminations, the number of divisions of the steps may be increased, or a pattern without steps may be provided.

FIG. 13 is a flowchart showing a method of setting the threshold value, and the measuring unit performs a plurality of measurements on the master work 11 corresponding to each work number. The calculation unit obtains a threshold value for identifying the model. The threshold is set with a range. First, the master work 11 as a reference for discrimination is installed in the execution environment of model discrimination, for example, at the start of operation of the cylinder block transfer line (S1). Next, the measurement of the time D is repeated a plurality of times, for example, 32 times (S2) for one master work 11 corresponding to the work number 1 at predetermined time intervals, and is stored in the memory 35 as a data group of the times D1 to D32. (S3).

The calculation unit obtains the mean value Da and the standard deviation σ from the times D1 to D32 of the obtained data group (S4). The threshold value for the work number 1 is set in the discrimination data table 12 as ± 3σ with the average value Da as the center, that is, Da ± 3σ (S5). The master sensor 1 and the slave sensor 2 transmit ultrasonic waves to the identification unit and receive the reflected wave to the work 6 mounted on the transport line, and the identification determination unit discriminates the difference between the measured values. If the work 6 falls within the threshold range set in the data table 12, it is determined that the work 6 is the work number 1. If the work 6 is known to be the work number 1, the machine tool controller 4 is output that the work number is 1. The machine tool controller 4 executes a machining instruction or the like according to the work number 1.

FIG. 14 is a graph showing the allocation state of the threshold value for each work number, and as an example, the work numbers 1 to 6 are assigned as a step of 1 mm. Six master works 11 having different steps are prepared for each work number, the data group, the mean value Da, and the standard deviation σ are obtained respectively according to FIG. 13, and the threshold value is centered on the average value indicated by the black circle of each work number. Is set in the range indicated by the vertical line. In the case of a casting such as a cylinder block, if the step is set to 0.7 to 1.4 mm, preferably about 1 mm, it is shown that the set values can be sufficiently determined so as not to overlap.

According to the determination of the threshold value as described above, the threshold value is determined not only based on the numerical value but also based on the value measured at the start of operation of the transport line of the work 6 under the actual measurement environment using the master work 11. Due to the fact that the measured values vary in the measurement environment, the statistical error is taken into consideration, etc., the threshold value does not have an unnecessarily large margin, and it is possible to handle a large number of models and improve reliability. Can be done.

Further, although the explanation has been made by focusing on the average value of the data group, the mode may be the center of the threshold value. Further, the standard deviation σ was obtained and set as the average value Da ± 3σ in the discrimination data table 12, but it is possible to set ± σ and ± 2σ instead of ± 3σ depending on the numerical distribution status of the data group. Further, it is also effective to learn a large number of measured values of each master work 11 a plurality of times or measured values at the time of identification determination of the work 6, use the results as empirical values, and determine the threshold value and range from the empirical values. ..

Normally, ultrasonic waves tend to have a wide beam size with respect to the work 6 to be measured, as well as the measured value being affected by the temperature. As a result, the measurement area has to be increased, and in the case of a cylinder block, the surface shape of the casting and the roughness have a large effect, which makes practical use difficult. Further, although the beam size can be reduced by providing an ultrasonic horn which is a reflector for focusing and emitting ultrasonic waves in a certain direction or receiving waves, only sound waves traveling straight from the object to be measured can be received. Therefore, it is desirable to utilize the fact that the straightness of ultrasonic waves increases in proportion to the height of the frequency and the beam size can be reduced.

Further, when the frequency is the same and the oscillator dimensions are different, the directivity becomes sharp when the oscillator dimensions are large, and the beam width is large at a short distance, but the ultrasonic beam does not spread so much at a long distance. On the other hand, if the size of the oscillator is small, the directivity becomes dull and the beam width is small at a short distance, but the spread of the beam becomes large at a long distance and the echo height is significantly reduced depending on the distance.

FIG. 6 shows the relationship between the beam size of the ultrasonic displacement sensor, the oscillation frequency, and the distance. The alternate long and short dash line is 40 kHz, the broken line is 100 kHz, and the solid line is 300 kHz. On the other hand, FIG. 7 shows the relationship between the energy density of the ultrasonic displacement sensor and the oscillation frequency and the distance, and the energy density related to the output intensity is attenuated as the oscillation frequency is higher as shown in the figure. Similar to FIG. 6, the alternate long and short dash line is 40 kHz, the broken line is 100 kHz, and the solid line is 300 kHz.

FIG. 8 shows the measured values of the beam size when the oscillation frequencies are 40 kHz and 300 kHz, and when the oscillation frequency is set to 300 kHz, the operating distance from the work 6 (cylinder block) to the master sensor 1 is 200 mm, and 20 mm corresponding to an appropriate measurement area. Can be. The oscillation frequency can be 200 to 400 kHz, the operating distance can be 150 to 250 mm, and the beam size can be 15 to 25 mm, which is a practical value for the cylinder block. Further, since the distance from the master sensor 1 and the slave sensor 2 to the identification unit is set to 150 to 200 mm, it is not necessary to bring the sensors close to each other in the cylinder block manufacturing line, so that the position control for stopping the work 6 becomes easy. , The sensor position does not interfere with the machining of the work 6.

Further, since the cylinder block is a casting, the unevenness of the measurement surface is limited to a step of about 1 mm. On the other hand, when the oscillation frequency is 40 kHz and the beam size is about 60 to 80 mm as in the conventional ultrasonic displacement sensor, the resolution is about 1 mm, and it is impossible to measure a step of 1 mm.

If the oscillation frequency is 200 to 400 kHz and the operating distance is 150 to 250 mm, the resolution can be improved to about 0.1 mm, and the identification of the limit of 1 mm that can be stepped in the casting takes into consideration the influence of the surface roughness of the casting. However, it is possible enough. By setting the oscillation frequency of the ultrasonic wave to 200 to 400 kHz, the beam size of the ultrasonic wave can be reduced and the area of the identification unit can be reduced. Further, since the beam size of the transmitting ultrasonic wave in the identification unit is set to 15 to 20 mm, the production of the identification unit does not become an obstacle even if the shape is complicated by casting such as a cylinder block. However, when an electric signal close to the resonance frequency is pulsed to the ultrasonic elements 31 and 32, a phenomenon occurs in which the ultrasonic vibration mechanically continues for a short time even after the electric signal disappears, which is a reflection type. Therefore, if this phenomenon continues for a long time, it becomes difficult to detect.

FIG. 9 shows the time change of the output voltage from oscillation to reception when the oscillation frequency is set to about 40 kHz as in the conventional case. The peak of the graph on the far right side of the drawing in FIG. 9 is the detection of multiple reflected ultrasonic waves. As described above, since the ultrasonic wave having a low frequency has a small amount of attenuation after transmission, multiple reflections are likely to occur, and the conventional ultrasonic distance measuring instrument may erroneously detect this multiple reflections. On the other hand, when the oscillation frequency is set to 200 to 400 kHz, the attenuation of the ultrasonic wave is large, so the reflected wave is also large as shown in the peak of the graph on the rightmost side of the drawing in FIG. It is attenuated, the influence of multiple reflections can be reduced, and the variation in measurement can be reduced.

FIG. 11 shows the discriminating effect on the air temperature when the master sensor 1 and the slave sensor 2 are used as one set. When the temperature rises by 10 ° C, the speed of sound rises, so if the temperature rise by 10 ° C is not corrected, the distance of 200 mm is measured as 196.5 mm, but this effect is ignored because the difference is measured and calculated. It can be made as small as possible. Actually, the change in the temperature rise of 10 ° C. on the step of 1 mm is about 0.017 mm.

FIG. 12 shows the timing of oscillating ultrasonic waves when the master sensor 1 and the slave sensor 2 are used as one set. The oscillation of the slave sensor 2 is delayed with respect to the oscillation of the master sensor 1 for a sufficient time that the two ultrasonic waves do not interfere with each other, and a time longer than the time for reciprocating the operating distance of 200 mm and not transmitting at the same time. Further, the CPUs 33 and 34 control each other in order to synchronize the two timings with a common clock so that the timings do not deviate from each other. Further, in order to reduce the variation in the measured values, it is desirable to repeat the number of measurements 32 to 64 times in one identification. In addition, it is desirable to calculate the median value of repeated measured values as in a median filter, and to prominently exclude different values and stabilize them.

In the above embodiment, the discrimination target is a casting, but the discrimination target is not particularly limited as long as it can form irregularities. For example, it is also possible to integrally form a plastic molded product on the work 6.

1 Master sensor 2 Slave sensor 3 Sensor unit 4 Machine tool controller 5 Machine tool 6 Work 11 Master work 12 Discrimination data table 31, 32 Ultrasonic element 33, 34 CPU
35, 36 memory

Claims (8)

In an identification device that identifies the type of article provided with an identification unit at a predetermined position
The identification unit has a step that is changed by a predetermined amount for each type of the article.
A master sensor and a slave sensor that transmit ultrasonic waves to the identification unit, receive reflected waves, and measure the time from transmission to reception .
A discrimination data table in which data relating to the step for each type of the article, which is a reference for discrimination of the article, is stored, is provided.
The master sensor and the slave sensor measure the step and
An identification device for discriminating the type of an article by comparing a difference value of values measured by the master sensor and the slave sensor with the discriminating data table. The master sensor and the slave sensor are arranged at positions facing the identification unit.
The identification device according to claim 1, wherein the type of the article is determined by detecting a step between the surface of the identification unit facing the master sensor and the surface of the identification unit facing the slave sensor. .. The identification device according to claim 1 or 2, wherein the ultrasonic waves are transmitted alternately between the master sensor and the slave sensor. The identification device according to any one of claims 1 to 3, wherein the oscillation frequency of the ultrasonic wave is set to 200 to 400 kHz. Any one of claims 1 to 4, wherein a clock signal serving as a reference time for transmitting ultrasonic waves is generated by the master sensor, and ultrasonic waves are transmitted by the slave sensor in synchronization with the clock signal. The identification device described in. The identification device according to any one of claims 1 to 5, wherein the distance from the master sensor and the slave sensor to the identification unit is 150 to 200 mm. An identification method that identifies the type of goods
An identification unit having a step that is changed by a predetermined amount for each type of article is provided at a predetermined position of the article.
The master sensor and slave sensor transmit ultrasonic waves to the identification unit, receive reflected waves, and measure the time from transmission to reception.
The difference value of the values measured by the master sensor and the slave sensor is compared with the discrimination data table in which the data relating to the predetermined amount of the step for each type of the article, which is the reference for discrimination of the article, is stored. A method for identifying the type of the article. The identification method according to claim 7 , wherein the ultrasonic waves are transmitted alternately between the master sensor and the slave sensor.