JP2013252582A - Gear processing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear processing machine which achieves improvement in machining accuracy of even a gear having a small module or a small number of teeth by enabling correct phase positioning of a hob using simple configuration.SOLUTION: A gear processing machine is configured in such a way that: a sensor turning part 133 supports a laser displacement sensor 131 so as to be turnable using an optical axis, which is formed by connecting a light projection part to a light reflection point of the gear 200, as a rotation axis; the laser displacement sensor 131 is positioned so that a triangle formed by connecting the light projection part, the light reflection point, and a light reception part is made perpendicular to a tooth trace direction; and the laser displacement sensor 131 is adjusted with respect to a tooth profile so that a diffuse reflection laser beam can easily be received.

Description

  The present invention relates to a gear processing machine for manufacturing gears.

  Conventional gear processing has been performed in the following procedures: (1) cutting (hobbing), (2) quenching, and (3) grinding with a gear grinder.

(1) Cutting (hobbing)
This hobbing is a process of manufacturing a gear by rough (rough) cutting.
(2) Quenching This is a step of quenching (heat treatment) the gear after cutting in order to increase the mechanical strength of the gear.
(3) Grinding finish by gear grinding machine This is a process of finishing (grinding) after quenching.

In accordance with a normal processing method in the machine field, quenching is performed after gear cutting is performed with high accuracy without rough (rough) cutting.
However, in gear machining, the above-described machining method has been employed because the tooth portion is thermally deformed by this quenching or the like and the shape accuracy is deteriorated. In particular, the precision of the gears was improved by correcting the thermal deformation by the grinding finish of (3).

  However, the conventional gear machining has a problem in the grinding finish of (3). Grinding is expensive due to the use of an expensive gear grinder and the poor production efficiency due to manual work by skilled craftsmen. For this reason, there were many cases in which the profitability did not match, the improvement in accuracy was given up, the steps (1) and (2) were performed, and the hardened gear was used as it was. This had a great adverse effect on the quality of gear products.

Accordingly, skiving processing using a hobbing machine (re-hobbing: rehabilitation using a hob) has been performed instead of the grinding processing of (3).
In gear machining that performs skiving, (a) rough (rough) cutting of gear (pre-hob machining) is performed in anticipation of thermal deformation, leaving a correction margin of about 0.2 mm for shoulder thickness, (b) A quenching process is performed, and (c) a skiving process is performed to remove the correction allowance by re-hobing the quenched gear using a skiving hob, and finish it to a normal dimension.

  This skiving process is a dry cut in which a carbide hob is used for cutting without using a cutting agent. In general, the skiving process is performed with a hob in which a TiAlN coating is applied to a dry cut super steel material. By adopting dry cut in this way, a cutting agent that deteriorates the work environment, such as bad odors and dirt due to scattering, is unnecessary, and the problem of environmental deterioration due to air pollution when processing the waste agent is solved. This machining method achieves machining efficiency equivalent to that of conventional hobbing, and the machine price is kept below half the value of a gear grinding machine. Therefore, the machining cost is significantly reduced compared to gear grinding.

  Furthermore, the gear accuracy by skiving is JIS N5 to N6, which is comparable to hobbing, and is not as good as JIS N4 to N5 for grinding by gear grinding. Yes. Skiving can easily and inexpensively improve gear accuracy to a predetermined level, greatly contributing to the quality of the final product.

  The gear finishing process by hard hobbing was developed as a new processing method with the spread of dry cutting. Hard hobbing is a method of finishing a hardened tooth surface with a hardness of about HRC 50 to 60 with a carbide hob with high accuracy. There is no clear definition of hard hobbing, but to say it is a process of finishing hardened tooth surfaces that are hardened by both skiving and hard hobbing, and the feature of skiving hob is a large module up to 30th module This is a carbide brazed large hob with a negative squeeze angle of around -30 °, but the hard hobbing hob on the contrary is a small solid carbide hob of module 0.3 to module 2.5. Many of them have angles around 0 °. This hard hobbing processing method is partly wet processing, but is almost dry-cut processing and environmentally friendly. It is expected to be a low cost gear finishing method.

  Thus, in the gear manufacturing which performs skiving processing and hard hobbing processing, which are inexpensive and highly efficient correction methods, on the thermally deformed gear after quenching, a highly accurate gear can be manufactured by a simple process. These skiving and hard hobbing processes have become very valuable as high-precision gear finishing methods for workpieces.

  In general, gear grinding is still used to obtain a highly accurate gear. Therefore, depending on the purpose of the gear, the gear finishing method (3) is divided into grinding using a grinder and skiving / hard hobbing using a hobbing machine. Comparison points between grinding using a grinder and skiving / hard hobbing using a hobbing machine are as follows.

Gear grinding is 1 to 3 Rz, bias tooth profile and the like can be corrected, and gear grinding is employed in gear machining that requires high tooth profile accuracy.
Hard hobbing has a tooth surface roughness of about 1Rz (adjustable feed) and high tooth profile accuracy, but does not require accuracy that can be achieved by gear grinding, and does not pursue accuracy until tooth profile correction. Then, hard hobbing is adopted.

Gear grinding requires a skilled craftsman to use a grinding machine, which is costly and requires several trials for tooth thickness management.
Hard hobbing is usually easy to operate with an extension of the hobbing machine and can keep the cost low, and the tooth thickness management can reliably cut to the target value.

Gear grinding is a wet cut that uses a cutting agent, and the environment is disadvantageous.
Hard hobbing is a dry cut that uses air instead of a cutting agent and has a good environment.
Hard hobbing is generally advantageous except that the processing accuracy of hard hobbing is slightly inferior. Note that skiving has the same advantages as hard hobbing.

  In the skiving processing and hard hobbing processing described above, the gear shape formed by the pre-hob is read by a sensor, and re-hobbing is performed based on the read data. As a prior art of the gear machining apparatus that reads the gear shape by the sensor as described above, for example, Patent Document 1 (Japanese Patent Laid-Open No. 08-1187144, name of invention “Gear finishing method of hobbing machine”) The described invention is known.

  In the invention described in Patent Document 1, the position of the cutting blade of the hob is detected by a sensor, the deviation of the position of the generating center line and the cutting blade is calculated by a numerical controller, and the calculated value is used as the rotation angle value of the gear to be processed. The converted value is used as the first rotation angle value, the gear to be processed is rotated by an appropriate angle, the position of the tooth groove of the gear to be processed is detected by a sensor, and the generating center line and the tooth groove are detected by a numerical controller. , The calculated value is converted into the rotation angle value of the gear to be processed, the converted value is used as the second rotation angle value, the second rotation angle value is added to the first rotation angle value, The angular position of the workpiece gear is shifted by the total value, and thereby the hob cutting blade and the gear groove of the workpiece gear are aligned. Such a polishing apparatus provides an effective hobbing gear finishing method.

  In addition, as another prior art of a gear processing device that reads a gear shape by a sensor, for example, an invention described in Patent Document 2 (Japanese Patent Laid-Open No. 2004-25333, name of invention “Gear Processing Machine”) It has been known. In the gear machining machine described in Patent Document 2, when a workpiece composed of a gear to be machined is finished with a hob, the workpiece is processed prior to the meshing of the hobbed teeth and the tooth grooves of the workpiece. Based on the detection data obtained by detecting the teeth of the workpiece with the sensor in the state of continuous rotation in one direction, the pitch and position of the workpiece teeth are determined, and based on the determination result, the workpiece and the hob At least one of the rotational phases is corrected so that the rotational phases coincide with each other. In such a gear processing machine, the teeth of the workpiece can be detected easily and accurately without imposing a burden on the rotation transmission system of the machine, and the rotational phase alignment between the workpiece and the hob is performed based on the detection result. It can be done properly.

Japanese Patent Laid-Open No. 08-1187144 JP 2004-25333 A

However, all of the above conventional techniques have problems.
In the hobbing machine, when re-hobbing parts that have been heat-treated after rough cutting and re-hobbing to correct accuracy, the tooth surface of the workpiece (the gear that has been heat-treated after rough cutting) In order to detect the phase (assuming that the phase of the hob is known), a method is adopted in which the proximity sensor is brought close to the outer peripheral surface of the workpiece, and the workpiece is arbitrarily rotated by the rotating shaft of the gear to detect the phase at a specific position on the tooth surface. It has been.

  For example, when inspecting the gear 600 having 6 teeth with the proximity sensor 500 having the sensor head diameter φ3 in the module 1.0 as shown in FIG. 7, the right tooth surface detection of FIG. The left tooth surface detection in FIG. 7B and the right / left middle in FIG. However, as shown in FIGS. 8 (a), 8 (b), and 8 (c), the proximity sensor 500 having a sensor head diameter φ3 with respect to the gear 600 having six teeth in the module 0.4 is used. When inspecting, the following problems occurred.

(1) Since the measurement accuracy of the proximity sensor 500 is not so good in the first place, the error of the phase detection position is large.
(2) When the proximity sensor 500 is a small module and the number of teeth increases and the tooth interval becomes narrow, adjacent teeth are also detected, and accurate correction becomes difficult due to erroneous measurement. Module 0.5 was the limit with the smallest sensor head diameter of the prior art.

(3) The sensor head is replaced according to the size (module and number of teeth) of the gear 600. As described above in (2), the proximity sensor 500 detects a plurality of teeth based on the interval and size of the teeth of the gear 600. Therefore, when the module of the gear 600 is small, it is necessary to replace it with a smaller proximity sensor 500 corresponding to the gear 600 and bring it closer to the tooth surface. That is, when the tooth profile of the gear 600, the tooth pitch, and the like change, it is necessary to replace and adjust the proximity sensor 500, which is troublesome.

(4) The proximity sensor 500 has a different detection distance depending on the sensor, and the sensor head needs to be brought closer to the gear 600 as the diameter of the sensor head becomes smaller, and adjustment work is required when setting the distance to the gear outer diameter. But it was time consuming.

(5) Since it is necessary to retract the proximity sensor 500 during processing, a telescopic arm mechanism is required.
(6) As a process for detecting the phase of the tooth surface, an arm expansion / contraction process is necessarily required, which is added to the machining time.

  Such problems have the same problem in the hobbing machine described in the cited document 1 and the gear machining machine described in the cited document 2.

  As described above, in rehobbing, there are restrictions on the number of modules and the number of teeth. In particular, when the module is small, detection by a proximity sensor becomes difficult, and there is a problem in creating a highly accurate gear.

  Accordingly, the present invention has been made in view of the above-described problems, and its purpose is to enable accurate phasing of the hob with a simple configuration, and to improve machining accuracy even with a module or a gear having a small number of teeth. An object of the present invention is to provide a gear processing machine that can be improved.

The invention according to claim 1 of the present invention is
In gear processing machines that create gears by hob cutting,
A light projecting unit that irradiates the gear with linear laser light substantially perpendicularly to the rotation axis of the gear, and a laser displacement sensor that has a light receiving unit that receives reflected light from the tooth surface of the gear;
The laser displacement sensor is supported by a sensor rotation axis that matches the laser optical axis connecting the light projecting part and the reflection point, and the triangle connecting the light projecting part, the reflection point, and the light receiving part is oriented in the direction of the tooth trace. A sensor rotating unit that positions the teeth at right angles to the teeth and adjusts the position of the light receiving unit of the laser displacement sensor so that the diffuse reflected light of the laser is easily received with respect to the tooth shape;
It was set as the gear processing machine characterized by providing.

The invention according to claim 2 of the present invention is
The gear processing machine according to claim 1, further comprising a lid provided on a front surface of the laser displacement sensor for opening and closing.

  According to the present invention as described above, it is possible to provide a gear processing machine that can accurately determine the phase of the hob with a simple configuration, and can improve the processing accuracy even with a module or a gear having a small number of teeth. it can.

1 is a perspective external view of a gear processing machine for carrying out the present invention. It is a perspective enlarged view of a gear processing machine. It is explanatory drawing of a laser sensor part. FIGS. 4A and 4B are explanatory views for explaining gear laser measurement and rotation of the laser sensor unit. FIG. 4A is a side view, FIG. 4B is a rear view, and FIG. FIG. FIG. 5A is an explanatory diagram of laser measurement, FIG. 5A is an explanatory diagram of laser measurement before rotation adjustment, and FIG. 5B is an explanatory diagram of laser measurement after rotation adjustment. It is a flowchart of re-hobbing. It is explanatory drawing of the tooth surface inspection of the gearwheel by a proximity sensor. It is explanatory drawing of the tooth surface inspection of the gearwheel by a proximity sensor.

  Then, the form for implementing this invention is demonstrated, referring FIGS. 1-6. The gear processing machine 100 is a horizontal hobbing machine that processes gears by cutting, and is provided so that the rotation axis of the gear 200 as a workpiece is in the horizontal direction and the rotation axis of the hob is in the vertical direction. The present invention relates to the “finishing process” in which the gear 200 hardened after the pre-hobing in the above (c) is re-hobbed by using a hob for hard hobbing and skiving, and finished to a normal dimension by re-hobbing. The improvement of the tooth matching process is realized.

  The gear processing machine 100 includes a bed 1, a guide rail 2, a moving base 3, a Z-axis motor 4, an X-axis motor 5, a hob turning motor (A axis) 6, a hob shift motor (Y axis) 7, and a hob axis motor (B Shaft) 8, head 9, hob 10, spindle motor (C axis) 11, support portion 12, and laser sensor portion 13. The gear processing machine 100 performs a finishing process by re-hobing on the gear 200 that has been quenched after rough cutting.

  A guide rail 2 is disposed on the bed 1, and a movable base 3 is slidably supported on the guide rail 2 so as to move in the Z direction. The moving base 3 is positioned in the Z-axis direction by the Z-axis motor 4. An X axis motor 5, a hob turning motor (A axis) 6, a hob shift motor (Y axis) 7, and a hob axis motor (B axis) 8 are attached to the moving base 3.

  For example, a carbide hob 10 is disposed on the head 9. In order to realize dry cutting, a carbide hob is used to suppress wear of the hob 10. Such a hob 10 is driven and rotated by a hob shaft motor (B-axis) 8. The hob 10 is positioned on the moving base 3 by a hob shift motor (Y axis) 6, a hob turning motor (A axis) 7, and an X axis motor 8.

  A gear 200 that is a workpiece is horizontally held between a main shaft motor (C-axis) 11 and a support portion 12, and the main shaft motor (C-axis) 11 drives and rotates the gear 200 around a horizontal rotation axis. Controls necessary for generating the gear, such as rotation of the gear 200, rotation of the hob 10, and cutting feed, are performed based on commands from a control unit (not shown).

  Next, a laser sensor unit that characterizes the present invention will be described with reference to the drawings. As shown in FIG. 2, the laser sensor unit 13 includes a laser displacement sensor 131, a sensor storage box 132, and a sensor rotation unit 133. On the outside of the sensor storage box 132, a lid 134 is provided as shown in FIG.

  As shown in FIG. 4A, the laser displacement sensor 131 further includes a light projecting unit 131a and a light receiving unit 131b. The laser optical axis of the linear laser light emitted from the light projecting unit 131 a is made to coincide with the axis that passes from the light projecting unit 131 a to the rotation axis of the gear 200. As shown in FIGS. 4B and 4C, the linear laser light has a horizontally long linear shape in the tooth trace direction.

  Here, the reason for using the linear laser beam will be described. A general laser displacement sensor often uses a point laser beam having a small spot diameter. However, the laser beam tends to be irregularly reflected on a rough machined surface as in the present invention. Will not return and measurement will be impossible. On the other hand, by applying the linear laser beam, it is possible to stably obtain the average value data of the linear region irradiated with the laser beam. This is because the linear laser beam is excellent in this respect.

  As shown in FIG. 2, the sensor storage box 132 is fixed to the slide device of the lower support portion 12 and moves together with the support portion 12 and the gear 200, and the gear 200 and the sensor storage box 132 maintain a certain distance. . As shown in FIG. 3, a lid 134 is provided on the outer surface of the sensor storage box 132 and facing the gear 200 that is a workpiece. The sensor rotation unit 133 is fixed inside the sensor storage box 132, and the sensor rotation unit 133 rotates the laser displacement sensor 131.

  The lid part 134 is rotated by a lid part rotation drive unit (not shown), and opens and closes the front surface of the laser sensor unit 13. Prior to re-hobbing, when the tooth surface data and phase data of the gear 200 are acquired, the lid 134 rotates and the front surface of the laser displacement sensor 131 is opened. As will be described later, the laser displacement sensor 131 is protected from cutting scraps and the like that are closed when the lid 134 is closed during re-hobbing.

  Next, angle adjustment by the sensor rotation unit 133 will be described. As a premise, it is assumed that it is arranged so as to be substantially perpendicular to the rotation axis of the gear 200 that is a workpiece as viewed from above. The distance from the laser displacement sensor 131 to the gear 200 is kept constant. As shown in FIG. 4A, the laser displacement sensor 131 is supported by a sensor rotation unit 133 so as to be rotated by a sensor rotation axis coaxial with the emitted light. When it rotates, as shown in FIGS. 4B and 4C, it tilts when viewed from the back. This angle adjustment is arranged using the sensor rotation unit 133 so as to be substantially perpendicular to the tooth trace direction of the gear. For example, when the gear is a spur gear or the like, the angle is substantially right when the laser displacement sensor 131 is not tilted, and the tilt angle is 0 ° with respect to the vertical direction as shown in FIG. 4B.

  However, for example, when the gear is inclined like a helical gear, the linear laser beam and the tooth surface interfere with each other unless the twist angle is adjusted as shown in FIG. It is easy to get out and it becomes easy to generate erroneous measurement. Moreover, since the reflected light itself is difficult to return to the light receiving unit, a situation in which measurement cannot be performed easily occurs.

  In order to eliminate such interference, the tilt angle of the laser displacement sensor 131 is adjusted by the sensor rotating unit 133, and the light projecting axis and the light receiving axis are aligned in the tooth trace direction. For example, coarse adjustment is performed based on the previously determined gear twist angle, and then the angle is finely adjusted so that the amount of received light is maximized. The rotation of the sensor rotation unit 133 is set to be the same rotation axis as the laser optical axis that is the emitted light shown in FIG. 4A, and as shown in FIG. The laser displacement sensor 131 is tilted.

  The laser displacement sensor 131 is rotated by a rotation axis coinciding with the laser optical axis and is perpendicular to the tooth trace direction, that is, the triangle connecting the light projecting part, the reflection point and the light receiving part is perpendicular to the tooth surface. Thus, the laser light is adjusted so that the diffusely reflected light of the laser is easily received by the light receiving portion 131b, and rotated so as to have an angle θ. As shown in FIG. 5B, the linear laser light is aligned with the twist angle of the gear, so that interference of the laser light is suppressed, multiple reflected light is reduced, and occurrence of erroneous measurement is suppressed. Further, the reflected light itself is easily returned to the light receiving unit 131b and is reliably measured. The angle adjustment by the sensor rotation unit 133 is such.

  Subsequently, re-hobbing is started. The re-hobbing is performed according to the procedure shown in the flowchart of FIG. After completion of the work setting by performing the above-mentioned angle adjustment by the sensor rotation unit 133 in the laser sensor unit 13 in which the gear 200 that has been quenched after the pre-hob is attached by an operator and the lid unit 134 is opened ( In step S11), the laser displacement sensor 131 irradiates the gear 200 supported around the substantially horizontal central axis with linear laser light (step S12).

  Specifically, as shown in FIG. 4A, the light emitted from the light projecting unit 131a is reflected at the reflection point of the gear 200, and the reflected light is received by the light receiving unit 131b, from the light projecting unit 131a. The distance to the gear 200 is measured. The laser beam axis of the linear laser beam emitted from the light projecting unit 131 a passes through the rotation axis of the gear 200. The detected distance is data based on the distance from the light projecting unit 131a to the tooth surface, but consideration is given so that it can be easily converted into tooth surface data that is the distance from the rotation axis to the tooth surface. This distance becomes a value along the tooth surface, the tooth surfaces of the first and second teeth are detected (step S13), and the angular difference between the first and second teeth is calculated (step S14), and the tooth Surface data and phase data can be obtained. Then, after the data acquisition, the emission of the linear laser beam is stopped (step S15). Note that the lid 134 is closed immediately after the light emission is stopped.

  Thus, the state of the tooth surface of the gear 200 after quenching is determined by laser measurement. And since the specification of the gear to be actually manufactured is known in advance, the rehob is performed so as to cut the difference between the tooth surface of the gear obtained by measurement and the tooth surface of the gear according to the specification.

  Specifically, the angle difference from the C-axis synchronization angle is calculated (step S16). If this angle difference is outside the allowable angle range, the workpiece is ended as a defective workpiece (NO in step S17), but if it is within the allowable angle range, the process proceeds to rehobbing (YES in step S17).

  When re-hobbing is performed, the C-axis synchronization angle is corrected (step S18), and after synchronization, re-hobbing is performed on the gear 200 (step S19). In addition, at the time of processing by re-hob, the lid part 134 covers the front surface of the laser sensor part 13 to prevent chips and the like from entering the laser sensor part 13. As a result, the laser displacement sensor 131 can be used with high accuracy over a long period of time.

  In the reworking, the cutting start position of the feed axis (Z axis) is determined based on the synchronization angle, and the cutting start position of the cutting axis (X axis) is determined based on the synchronization angle. Then, feeding of the feed shaft (Z axis) is started while rotating the main shaft (hob shaft), and cutting is started from the cutting start position. Even during the cutting process, synchronization is obtained by the previous tooth surface data and phase data, and the gear 200 is controlled to perform only the correction. When the feed axis (Z axis) reaches the machining end point, the cutting axis (X axis) is returned to the origin, and then the main axis (hob axis) is stopped. At this time, the cutting agent is not supplied to the hob 10 during cutting, and the tooth profile is corrected by dry cutting. Re-hobbing is done in this way.

The gear processing machine 100 of the present invention has been described above.
In the laser sensor unit, although not shown, if the entire sensor box is configured to move parallel to the workpiece axis (Z axis) while maintaining the above conditions, the Z axis direction of the gear 200 Thus, tooth surface data and phase data at a plurality of different positions can be acquired, and more accurate re-hobbing can be performed. Such a configuration may be adopted.

  Such a gear processing machine of the present invention is not limited to a horizontal type, and may be applied to a vertical type gear processing machine. For example, if the laser displacement meter is placed at a 90 ° inclination on a gear processing machine in which the rotation axis of the gear 200 as a workpiece is vertical and the rotation axis of the hob is horizontal, the vertical gear Applicable to processing machines. Various other configurations can also be selected.

As described above, according to the gear processing machine described above, a laser displacement sensor having a detection range wider than that of the proximity sensor is adopted as the sensor unit, so that it is possible to detect gears of module 0.5 or less, which was difficult to detect with the proximity sensor. Thus, the detection is not limited to the number of modules and the number of teeth, and the sensor head can be detected without replacement.
Further, since the laser displacement sensor has a wider detection range than the proximity sensor, it is not necessary to bring the laser displacement sensor close to the gear, which leads to shortening of the machining operation.

In addition, since the installation position of the laser sensor unit is out of the processing operation range, the detection cycle and the processing cycle can be separated, leading to a reduction in cycle time.
In addition, the laser sensor unit has a sensor rotation unit, and the laser displacement meter can be rotated according to the inclination angle of the teeth, so that accurate phase detection can be performed, and helical gear detection can also be supported. it can.

  Moreover, the laser sensor part has a cover part, and can protect the sensor from cutting powder in processing after detection.

  The gear processing machine according to the present invention as described above solves the problems of conventional proximity sensors, makes it possible to create special gears such as helical gears at low cost with high accuracy, and enhances industrial utility value. ing.

100: gear processing machine 1: bed 2: guide rail 3: moving base 4: Z-axis motor 5: X-axis motor 6: hob turning motor (A-axis)
7: Hob shift motor (Y axis)
8: Hob shaft motor (B axis)
9: Head 10: Hob 11: Spindle motor (C axis)
12: support part 13: laser sensor part 131: laser displacement sensor 131a: light projecting part 131b: light receiving part 132: sensor storage box 133: sensor rotating part 134: lid part

200: Gear

Claims (2)

In gear processing machines that create gears by hob cutting,
A light projecting unit that irradiates the gear with linear laser light substantially perpendicularly to the rotation axis of the gear, and a laser displacement sensor that has a light receiving unit that receives reflected light from the tooth surface of the gear;
The laser displacement sensor is supported by a sensor rotation axis that matches the laser optical axis connecting the light projecting part and the reflection point, and the triangle connecting the light projecting part, the reflection point, and the light receiving part is oriented in the direction of the tooth trace. A sensor rotating unit that positions the teeth at right angles to the teeth and adjusts the position of the light receiving unit of the laser displacement sensor so that the diffuse reflected light of the laser is easily received with respect to the tooth shape;
A gear processing machine comprising:   The gear processing machine according to claim 1, further comprising a lid that is provided on a front surface of the laser displacement sensor and opens and closes.

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