JP6696497B2 - Contamination prevention device and sensor unit using the same - Google Patents

Description

  The present invention relates to a dirt adhesion prevention device that prevents dirt from adhering to a lens for protecting a sensor in a detection device that detects an object by a sensor, and a sensor unit using the dirt adhesion prevention device.

  When performing hot metal plating on a steel sheet, for example, hot dip galvanizing, as shown in FIGS. 12 (a) and 12 (b), a molten metal (plating bath) 102 such as molten zinc in a plating tank 101 is continuously supplied. After immersing the steel plate 103 in a desired manner and adhering the molten metal to the steel plate 103, the steel plate 103 is pulled up from the plating tank 101 in the vertical direction, and a gas is provided above the plating tank 101 so as to face both surfaces of the steel plate 103. Pressurized gas is blown from the expansion device (gas wiping device) 104 to remove excess molten metal adhering to the steel sheet, and adjust to a desired coating adhesion amount.

  In this case, the position control of the steel plate 103 is performed so that the steel plate 103 is always held at the optimum position. The position control of the width direction of the steel sheet at this time is performed by EPC (Edge Position Control) using the edge sensor 105. As the edge sensor 105 used in EPC, an optical sensor having high repeatability is often used. The optical sensor has a light emitting element 105a and a light receiving element 105b as shown in FIG. 13, and the edge portion of the steel plate 103 is detected depending on whether or not the light receiving element receives a signal from the light emitting element.

  A protective lens is installed in front of the optical sensor (each of the light emitting element 105a and the light receiving element 105b) that constitutes the edge sensor 105. In this case, a part of the molten metal removed by blowing the pressurized gas from the gas expansion device (gas wiping device) toward the steel plate floats around the sensor as metal dust, which adheres to the protective lens. Then, the protective lens may become dirty, and it may be difficult to accurately detect the position of the steel plate by the edge sensor.

  Such a problem occurs not only in an apparatus for performing hot metal plating. For example, in Patent Document 1, in a coating line of an automobile, when a vehicle type and a vehicle type of a body are discriminated by using a phototube, a part of the sprayed paint floats as paint dust, which becomes a lens for protecting the phototube. It is described that if adhered, accurate measurement cannot be performed. In Patent Document 1, in order to solve such a problem, the lens 106 is covered with a shielding cover 107 as shown in FIG. 14, and pressure is applied to the inside of the shielding cover 107 via a pressurized air supply passage 109. There is disclosed a device for preventing adhesion of dirt on a photoelectric tube lens, which supplies air and causes pressurized air to flow toward the opening end 107a of the shield cover 107 to prevent dust 108 from adhering to the lens 106. Further, in Patent Document 1, it is possible to prevent entrainment of suspended matter such as paint dust into the shield cover by providing the shield cover 107 with an enlarged diameter portion and making the opening end 107a the maximum diameter portion.

  A similar device for preventing dirt from adhering to a lens is also used in an apparatus for performing molten metal plating. For example, as shown in FIG. 15 which is a side view, a cover member 111 that covers the protective lens 110 that protects the edge sensor and serves as a flow path of the pressurized gas, and a pressurizing gas that supplies the pressurized gas to the inside of the cover member 111. The cover member 111 includes a gas supply unit 112, a gas introduction unit 113 provided at a position distant from the protection lens 110, a gas diffusion unit 114 for diffusing the pressurized gas toward the protection lens 110, and a protection unit. It has a gas discharge part 115 that discharges a pressurized gas at a position corresponding to the lens 110, and when viewed from the direction of arrow A in FIG. 15, the gas diffusion part 114 has a T-shape as shown in FIG. Alternatively, it has a triangular shape as shown in FIG. 17 and has a shape that widens toward the gas discharge portion 115.

JP, 11-33448, A

  By the way, when the flow velocity of the pressurized gas at the opening end of the gas discharge portion becomes smaller than the predetermined flow velocity, dust invades from the opening end and the protective lens becomes dirty. Need to be

  However, in the dirt adhesion preventing device having the cover member having a shape that spreads from the gas introduction part toward the gas discharge part as shown in the above-mentioned Patent Document 1 and FIGS. 16 and 17, at the opening end of the gas discharge part. The flow velocity difference in the width direction of the pressurized gas is large, and in order to prevent dust from entering and effectively prevent the protective lens from being soiled at all positions of the gas discharge part, in order to achieve a predetermined gas flow velocity or more, It has been found that a large amount of pressurized gas is required.

  Therefore, the present invention makes the gas flow rate in the gas discharge part more uniform, and can effectively prevent dirt from adhering to the protective lens with a smaller amount of supply gas, and a dirt adhesion prevention device and the same. It is an object to provide a sensor unit using the.

  In order to solve the above problems, the present invention provides the following (1) to (10).

(1) A dirt adhesion prevention device for preventing dirt adhesion to a protective lens provided so as to cover a surface of a sensor used in an environment where dust is present to transmit or receive a detection signal,
A cover member that covers the protective lens and in which a gas flow path is formed,
A gas supply unit for supplying gas to the inside of the cover member,
The cover member is
A gas introduction unit in which gas is introduced from the gas supply unit at a position away from the protective lens,
A gas diffusion part for diffusing the introduced gas in the direction of the protective lens;
A gas discharge part for discharging the gas from the gas diffusion part in a direction away from the protection lens at a position corresponding to the protection lens,
The dirt adhesion preventing device, wherein the gas diffusion portion has a rectangular parallelepiped shape.

  (2) The dirt adhesion preventing device according to (1), wherein the width of the gas diffusion portion is the same as the width of the gas discharge portion.

  (3) h / w, which is the ratio of the length w from the gas introduction part to the connection part between the gas diffusion part and the gas discharge part and the width w of the gas discharge part, is h / w> 0. .4 is satisfied, The stain | pollution | contamination adhesion prevention apparatus as described in (2) characterized by the above-mentioned.

(4) The average flow velocity at the open end of the gas discharge part is V _ave , the width w of the gas discharge part, the thickness t ′ of the gas discharge part, and the equivalent diameter De = 4 × w × t ′ / (2 × w + 2 × t ′), the Reynolds number Re represented by V _ave × De / ν using the kinematic viscosity coefficient ν of the gas is 30000 or more, and the stain adhesion preventing device according to (2) or (3) ..

  (5) The ratio t / t ', which is the ratio of the thickness t of the gas diffusion portion to the thickness t'of the gas discharge portion, satisfies t / t'> 1. (2) From (2) The dirt adhesion prevention device according to any one of 4).

  (6) Length h from the center of the gas introduction part to the connection part between the gas diffusion part and the gas discharge part, and from the bottom surface of the gas diffusion part to the connection part between the gas diffusion part and the gas discharge part The lens stain prevention device according to any of (2) to (5), wherein h / j, which is the ratio to the length j, satisfies 0.5 <h / j <0.8.

  (7) The dirt adhesion prevention device according to any one of (2) to (6), wherein the gas discharge part has a rectangular parallelepiped shape.

(8) A sensor that transmits or receives a detection signal,
A protective lens provided so as to cover the surface that transmits or receives the detection signal of the sensor,
A sensor unit having the dirt adhesion preventing device according to any one of (1) to (7), which prevents dirt from adhering to the protective lens, and is used in an environment where dust is present. ..

  (9) The sensor unit according to (8), wherein the sensor is an optical sensor whose detection signal is light.

  (10) The sensor unit according to (8), wherein the sensor is an ultrasonic sensor whose detection signal is an ultrasonic wave.

  ADVANTAGE OF THE INVENTION According to this invention, the difference in the flow velocity of the gas in a gas discharge part can be made more uniform, and the adhesion of dirt to a protective lens in the environment where dust exists can be effectively prevented with a smaller amount of supply gas. ..

It is a perspective view showing a sensor unit including a dirt adhesion prevention device concerning one embodiment of the present invention. It is a longitudinal section showing a sensor unit containing a dirt adhesion prevention device concerning one embodiment of the present invention. It is a front view and a side view showing a cover member of a dirt adhesion prevention device concerning one embodiment of the present invention, (a) is a front view and (b) is a side view. FIG. 7 is a diagram showing a flow velocity distribution of the pressurized gas on the X-axis at the opening end of the gas discharge part when the shape of the gas diffusion part is the T-shape shown in FIG. 5 and the triangle shown in FIG. 6. It is the front view and side view which show the cover member which has the conventional T-shaped gas diffusion part, (a) is a front view and (b) is a side view. It is the front view and side view which show the conventional cover member which has a triangular-shaped gas diffusion part, (a) is a front view, (b) is a side view. It is a figure which shows the flow velocity distribution when the flow velocity ratio r is small, and when it is large, and the average flow velocity for making the minimum flow velocity V _{min at} that time more than a minimum minimum flow velocity. It is a figure which shows the relationship between the value of h / w and the value of r (% display) in case the shape of a gas diffusion part is the rectangular parallelepiped shape of this invention, and the triangular shape of a prior art example. It is a figure which shows the relationship between the Reynolds number Re and the value of r (% display). It is a figure which shows the relationship between the value of t / t 'and the value of r (% display). It is a figure which shows the relationship between the value of h and the value of r (% display) at various values of j. It is a figure which shows the apparatus which performs a molten metal plating on a steel plate. It is a figure which shows the edge sensor using the optical sensor which consists of a light emitting element and a light receiving element used for the apparatus which carries out the molten metal plating to a steel plate. It is sectional drawing which shows the dirt adhesion prevention apparatus of the photoelectric tube lens of patent document 1. It is a side view which shows the conventional dirt attachment prevention apparatus of the lens used for the apparatus which performs a molten metal plating. FIG. 11 is a front view showing a cover member of a conventional device for preventing dirt from adhering to a lens having a T-shaped gas diffusion portion, which is used in an apparatus for performing molten metal plating. FIG. 11 is a front view showing a cover member of a conventional device for preventing dirt from adhering to a lens having a triangular gas diffusion portion, which is used in an apparatus for performing molten metal plating.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a perspective view showing a sensor unit including a dirt adhesion preventing device according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the sensor unit, and FIG. 3 is a cover member of the dirt adhesion preventing device according to an embodiment of the present invention. It is a front view and a side view showing.

  The sensor unit 1 includes a sensor 2, a protective lens 3 that protects the sensor 2, and a stain adhesion prevention device 4.

  The sensor unit 1 is for detecting a detection target such as an object or a mark, and is used in an environment where dust is present. For example, it can be used for an edge sensor that detects an edge of a steel plate in an apparatus that performs hot metal plating such as hot dip galvanizing. An optical sensor can be preferably used as the sensor 2. When the sensor unit 1 is used as an edge sensor in an apparatus for performing molten metal plating, a light emitting element or a light receiving element is used as an optical sensor. Then, the sensor unit 1 using a light emitting element as an optical sensor and the sensor unit 1 using a light receiving element as an optical sensor are paired to form an edge sensor. The optical sensor may be of a reflective type. An ultrasonic sensor may be used as the sensor 2.

  The protective lens 3 is provided so as to cover the surface of the sensor 2 that transmits or receives a detection signal. Here, the detection signal is used to detect a detection target such as an object or a mark, and is transmitted from the sensor unit 1, or is reflected by the detection target after being transmitted from the sensor unit 1 and is detected by the sensor unit 1. It refers to a signal that is received, or that is transmitted from the transmission side sensor unit and directly received by the reception side sensor unit, and specifically, light, ultrasonic waves, etc. are exemplified.

  The dirt adhesion prevention device 4 is for preventing dust such as metal dust generated during molten metal plating from adhering to the protective lens 3, and covers the protective lens 3 and provides a flow path for a pressurized gas. It has a cover member 11 in which is formed and a gas supply unit 12 for supplying a gas, for example, a pressurized gas, inside the cover member 11.

  The cover member 11 is provided at a position apart from the protective lens 3, and a gas introducing portion 21 into which the pressurized gas from the pressurized gas supply portion 12 is introduced and a gas for diffusing the pressurized gas toward the protective lens 3. The diffusion unit 22 and the gas ejection unit 23 that ejects the pressurized gas from the gas diffusion unit 22 in a direction away from the protection lens 3 are provided at positions corresponding to the protection lens 3.

  Although the gas introduction part 21 is illustrated as a cylindrical shape, it may have another shape. The gas diffusion portion 22 has a rectangular parallelepiped shape, and has a width w and a thickness t. Further, the length from the center of the gas introduction part 21 to the connection part between the gas diffusion part 22 and the gas discharge part 23 is h. Further, the length from the bottom surface 24 of the gas diffusion portion 22 to the connecting portion between the gas diffusion portion 22 and the gas ejection portion 23 is j. The gas discharge part 23 also has a rectangular parallelepiped shape, the width is w similar to the gas diffusion part 22, the thickness is t ′, and the projection length from the gas diffusion part 22 is l. The opening end 23a of the gas discharge part 23 has a rectangular shape, and the pressurized gas is ejected from the opening end 23a.

  The pressurized gas supply unit 12 pressurizes a gas such as air or nitrogen with a compressor or the like and supplies it as a pressurized gas.

  In the sensor unit 1 configured as described above, when the sensor 2 transmits or receives a detection signal such as light or ultrasonic wave, the detection signal is discharged from the protective lens 3 and the cover member 11 of the dirt adhesion prevention device 4 by gas discharge. The signal is transmitted by passing through the portion 23 or is received by passing through the gas discharge portion 23 and the protective lens 3.

  At this time, since the sensor unit 1 is used in an environment in which dust is present, the dirt adhesion prevention device 4 stains the protection lens 3 so that the dust does not adhere to the protection lens 3 and the protection lens 3 does not become dirty. Prevents adhesion. Specifically, the pressurized gas is supplied from the pressurized gas supply unit 12 to the cover member 11. The pressurized gas is introduced from the gas introduction part 21 of the cover member 11, diffuses in the gas diffusion part 22 toward the protective lens, and is discharged from the opening end 23 a of the gas discharge part 23 at a position corresponding to the protective lens 3. It By discharging the pressurized gas from the opening end 23a of the gas discharge part 23 in this way, it is possible to prevent dust from entering from the gas discharge part 23 and adhering to the protective lens 3.

  However, it has been found that when the conventional T-shaped one and the triangular one are used as the gas diffusion portion, the flow velocity of the gas in the gas discharge portion becomes non-uniform.

  FIG. 4 shows the flow velocity distribution of the pressurized gas on the X-axis of the opening end 23a of the gas discharge part 23 when the shape of the gas diffusion part is T-shaped as shown in FIG. 5 and when it is triangular as shown in FIG. FIG. As shown in FIGS. 5 and 6, the X axis is a straight line passing through the center line of the opening end 23a.

  As shown in FIG. 4, in the case of the conventional T-shaped gas diffusion portion 22 'of FIG. 5, the flow velocity at the central portion of the gas discharge portion is faster than that at the end portion. It is considered that this is because it is difficult for the pressurized gas to spread to the outside in the step portion where the gas diffusion portion 22 'becomes wider. Further, in the case of the triangular gas diffusion portion 22 ″ of FIG. 6, the flow velocity at the end of the gas discharge portion is higher than that at the central portion. This is because the pressure supplied from the pressurized gas introduction portion 21 to the gas diffusion portion 22 ″ is increased. It is considered that the V-shaped wall portion prevents the gas from spreading outward. As described above, when the conventional T-shaped gas diffusing portion and the triangular gas diffusing portion are used, the gas flow velocity difference at the gas discharge portion is large and the flow velocity becomes non-uniform.

Here, when the average flow velocity in the gas discharge portion is V _ave and the minimum flow velocity in the gas discharge portion is V _min , and the flow velocity ratio r = V _min / V _ave is defined, when the flow velocity ratio r = 1, V _ave and V _min Are equal, that is, there is no flow velocity difference as a whole, and the flow velocity distribution is uniform. Further, the smaller the flow velocity ratio r is, the larger the flow velocity difference is, which means that there is a region where the flow velocity is locally reduced. Therefore, in the case of the conventional T-shaped gas diffusion portion 22 'and the triangular gas diffusion portion 22'', r is small.

On the other hand, when the flow velocity from the opening end 23a of the gas discharge portion 23 becomes lower than a certain flow velocity, dust invades from the opening end 23a of the gas discharge portion and the protective lens 3 is soiled. Assuming that the flow velocity is the limit minimum flow velocity as shown in FIG. 7, the minimum flow velocity V _min needs to be a value exceeding the limit minimum flow velocity in order to prevent the protective lens from being contaminated. Need to be adjusted. At this time, the average flow velocity is proportional to the supply gas amount. Here, as shown in FIG. 7, in order to set the minimum flow velocity V _min to a value exceeding the limit minimum flow velocity, when the flow velocity difference is large (when r is small), when the flow velocity difference is small (when r is large). It is necessary to increase the amount of supply gas and to increase the average flow velocity compared with (1).

  Therefore, when the shape of the gas diffusion portion having a large difference in flow velocity is T-shaped or triangular, a large amount of supply gas is required to prevent the protective lens 3 from being soiled.

  On the other hand, in the present embodiment, the shape of the gas diffusion portion 22 is a rectangular parallelepiped. As a result, it is difficult for the pressurized gas to spread to the outside at the stepped portion as in the case of the T-shape, and the spread of gas to the outside is prevented by the V-shaped wall portion as in the case of the triangle. Therefore, the flow velocity at the gas discharge portion can be made more uniform. Therefore, it is possible to efficiently prevent the protective lens 3 from being soiled with a smaller amount of the supplied gas.

It is preferable that the value of the flow velocity ratio r (value of V _min / V _ave ) described above is larger (closer to 1), but may be larger than 0.5. As a result, it is possible to efficiently prevent the protective lens from being soiled. When r is 0.5 or less, the difference in the flow velocities becomes large, so that dirt easily adheres to the portion where the flow velocities are small. This is because the inertial force of the dust itself is larger than the force that the dust receives from the gas in the portion where the flow velocity is low.

  In order to increase the value of r and reduce the flow velocity difference at the open end of the gas discharge part, the length h from the center of the gas introduction part 21 to the connection part between the gas diffusion part 22 and the gas discharge part 23 and the gas It is preferable to increase the ratio (h / w) to the width w of the ejection portion. This is because the pressurized gas that has flowed into the gas diffusion portion 22 gradually diffuses in the gas diffusion portion 22 and needs to become a uniform flow field. For that purpose, diffusion corresponding to the width w of the gas discharge portion 23 is required. This is because a distance (height length h from the center of the gas introduction part 21 to the upper end of the gas diffusion part 22) is required.

  FIG. 8 is a diagram showing the relationship between the value of h / w and the value of r (expressed as a percentage) when the shape of the gas diffusion portion is the rectangular parallelepiped shape of the present invention and the conventional triangular shape. From FIG. 8, it is understood that the gas diffusion portion 22 needs to have a rectangular parallelepiped shape to satisfy r> 50 (%), and h / w> 0.4 is preferable.

The value of r is the average flow velocity V _ave at the opening end 23a of the gas discharge part 23, the width w of the gas discharge part, the thickness t ′ of the gas discharge part, and the equivalent diameter De = 4 × w × t ′ / ( 2 × w + 2 × t ′), which is related to the Reynolds number Re expressed by V _ave × De / ν by using the kinematic viscosity coefficient ν of the pressurized gas. In order to reduce the flow velocity difference at the end, the Reynolds number Re needs to be equal to or greater than a predetermined value.

  FIG. 9 is a diagram showing the relationship between the Reynolds number Re and the value of r (displayed in%). From FIG. 9, it can be seen that r> 50 (%) when the Reynolds number Re is 30,000 or more. Therefore, the Reynolds number Re is preferably 30,000 or more. In hot dip galvanizing equipment and the like, air or nitrogen is generally used as a pressurized gas, and the kinematic viscosity coefficient ν is a substantially fixed value. On the other hand, the Reynolds number Re is preferably equal to or more than the predetermined value because the flow velocity and the equivalent diameter of the gas discharge portion have a difference in flow velocity at the opening end of the gas discharge portion when the value becomes small.

  Furthermore, the value of r is also related to the ratio of the thickness t of the gas diffusion portion 22 to the thickness t ′ of the gas discharge portion 23, t / t ′. FIG. 10 is a diagram showing the relationship between the value of t / t 'and the value of r (expressed in%). It can be seen from FIG. 10 that if t / t ′> 1, then r> 50 (%). Therefore, t / t '> 1 is preferable. If the thickness t ′ of the gas discharge portion becomes larger than the thickness t of the pressurized gas diffusion portion, a flow velocity difference in the thickness direction (vertical direction) of the gas discharge portion will occur.

  Furthermore, the value of r is the length h from the center of the gas introduction part 21 to the connection part between the gas diffusion part 22 and the gas ejection part 23, and the bottom face 24 of the gas diffusion part 22 to the gas ejection part 23. It is also related to the ratio (h / j) to the length j up to. FIG. 11 is a diagram showing the relationship between the value of h / j and the value of r (expressed in%) at various values of j (in FIG. 11, the value of j standardized by w is shown). .. From FIG. 11, it can be seen that 0.5 <h / j <0.8 is desirable for r> 50%. When h / j is 0.8 or more, the pressurized gas supply portion and the surface 24 of the gas diffusion portion are close to each other, so that the amount of pressurized gas flowing around increases. Therefore, a flow velocity difference occurs at the opening end of the gas discharge portion.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the technical idea of the present invention. For example, in the above-described embodiment, the case where the present invention is applied to an apparatus that performs hot metal plating such as hot dip galvanizing has been described as an example, but the present invention is not limited to this, and when performing detection by a sensor in an atmosphere in which dust is present. If applicable, it is applicable. Further, in the above-described embodiment, the case where the pressurized gas is supplied to the cover member has been described as an example, but not limited to the pressurized gas, any gas may be used.

DESCRIPTION OF SYMBOLS 1 Sensor unit 2 Sensor 3 Protective lens 4 Contamination prevention device 11 Cover member 12 Pressurized gas supply unit (gas supply unit)
21 gas introduction part 22 gas diffusion part 23 gas discharge part 23a open end

Claims (9)

A dirt adhesion prevention device for preventing dirt adhesion to a protective lens provided so as to cover a surface for transmitting or receiving a detection signal of a sensor used in an environment where dust is present,
A cover member that covers the protective lens and in which a gas flow path is formed,
A gas supply unit for supplying gas to the inside of the cover member,
The cover member is
A gas introduction unit in which gas is introduced from the gas supply unit at a position away from the protective lens,
A gas diffusion part for diffusing the introduced gas in the direction of the protective lens;
A gas discharge part for discharging the gas from the gas diffusion part,
The gas diffusion portion has a rectangular parallelepiped shape,
The width of the gas diffusion portion and the width of the gas discharge portion are the same length,
The protective lens is provided so as to face a gas flow path of the gas diffusion portion from a wall portion of an end portion of the gas diffusion portion, and the gas discharge portion is an end of the gas diffusion portion where the protective lens is provided. A dirt adhesion preventing device, characterized in that gas is discharged from a portion in a direction orthogonal to the gas diffusion direction of the gas diffusion portion and away from the protective lens. The ratio h / w, which is the ratio of the length w from the gas introduction part to the connection part between the gas diffusion part and the gas discharge part and the width w of the gas discharge part, is h / w> 0.4. The dirt adhesion preventing device according to claim 1 , wherein the device is filled. The average flow velocity at the open end of the gas discharge part is V _ave , the width w of the gas discharge part, the thickness t ′ of the gas discharge part, and the equivalent diameter De = 4 × w × t ′ / (2 × w + 2 × t ′). The Reynolds number Re represented by V _ave × De / ν using the kinematic viscosity coefficient ν of the gas is 30000 or more, and the stain adhesion preventing device according to claim 1 or 2 . The gas wherein the thickness t of the diffusion section ', which is the ratio of the t / t' thickness t of the gas discharge portion, claim 1, characterized in that satisfy t / t '> 1 of claim 3 The dirt adhesion prevention device as set forth in any one of claims. A length h from the center of the gas introduction part to the connection part between the gas diffusion part and the gas discharge part, and a length j from the bottom surface of the gas diffusion part to the connection part between the gas diffusion part and the gas discharge part. the ratio of the h / j is a lens contamination preventive device according to any one of claims 1 to 4, characterized in that satisfy 0.5 <h / j <0.8. The gas discharge section, fouling prevention apparatus according to any one of claims 1 to 5, characterized in that a rectangular parallelepiped shape. A sensor that sends or receives a detection signal,
A protective lens provided so as to cover the surface that transmits or receives the detection signal of the sensor,
It has the dirt adhesion prevention device according to any one of claims 1 to 6 for preventing adhesion of dirt to the protective lens, and is used in an environment where dust is present. Sensor unit. The sensor unit according to claim 7 , wherein the sensor is an optical sensor whose detection signal is light. The sensor unit according to claim 7 , wherein the sensor is an ultrasonic sensor whose detection signal is an ultrasonic wave.

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