Distance measurement device

Abstract

A mirror (18) of a distance measurement device (1) scans light to the outside by being driven by an actuator (20) to swing. A base (11) has the mirror (18) provided therein. A swing shaft (13, 130) has the mirror (18) fixed thereto, and is rotatably supported by the base (11) with at least one end thereof projecting from the base (11). A position-holding part (16) has a biasing member (165) that biases the swing shaft (13, 130) to one side in the axial direction and a position-regulating part (161, 132) that regulates movement in the direction in which the swing shaft (13) is biased, and holds the axial position of the swing shaft (13). An abutting member (31) is fixed to the swing shaft (13) on the outside of the base (11). The distance between a housing part (50) and an end of the abutting member (31) on the side to the opposite direction from the direction in which the swing shaft (13) is biased is smaller than the distance between the base (11) and an end of the mirror (18) on the side to the opposite direction from the direction in which the swing shaft (13) is biased.

Description

distance measuring device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2023-122214, filed on July 27, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a distance measuring device.

[0003] Conventionally, there has been known a rotary reciprocating actuator used for LiDAR (Light Detection and Ranging). For example, in Patent Document 1, a rotary shaft to which a mirror part is attached is rotatably attached to left and right wall parts of a base via bearings.

[0004] Japanese Patent Application Laid-Open No. 2022-127381

[0005] In a structure in which a mirror is disposed between opposing wall surfaces as in Patent Document 1, when the axial position is restricted by, for example, a preload spring or the like, there is a risk that the mirror may come into contact with the wall surface and be damaged if it receives an impact that exceeds the load generated by the preload spring. An object of the present disclosure is to provide a distance measuring device that can prevent damage to the mirror.

[0006] The distance measuring device disclosed herein measures the distance to an object by scanning light externally and detecting the light reflected by the object, and is equipped with a mirror, a base, a swing axis, a position holding part, and an abutment member.

[0007] The mirror is driven to swing by an actuator to scan light to the outside. The mirror is provided inside the base. The swing shaft has the mirror fixed thereto and is swingably supported on the base with at least one end protruding from the base. The position holding portion has a biasing member that biases the swing shaft toward one side in the axial direction, and a position restricting portion that restricts movement of the swing shaft in the biasing direction, and holds the axial position of the swing shaft. The abutting member is fixed to the swing shaft outside the base.

[0008] The part that includes the base and is not driven by the actuator is called the housing. The distance between the end of the contact member opposite the biasing direction of the oscillation shaft and the housing is smaller than the distance between the end of the mirror opposite the biasing direction of the oscillation shaft and the base. This prevents damage to the mirror.

[0009] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a schematic diagram showing a distance measuring device according to a first embodiment, Fig. 2 is a cross-sectional view showing a swing actuator according to the first embodiment, and Fig. 3 is a cross-sectional view showing a swing actuator according to a second embodiment.

[0010] A distance measuring device according to the present disclosure will be described below with reference to the drawings. In the following, substantially identical components in multiple embodiments will be assigned the same reference numerals and descriptions thereof will be omitted.

[0011] 1 and 2 show a first embodiment. As shown in Fig. 1, a distance measuring device 1 is a LiDAR (Light Detection and Ranging) device that measures the distance to an object by emitting light and detecting reflected light from the object. The distance measuring device 1 is mounted on, for example, a vehicle and used to detect an object present in front of the vehicle.

[0012] The distance measuring device 1 includes a light emitting unit 91, a light receiving unit 92, and a swing actuator 5, and is housed in a housing 93. The light emitting unit 91 intermittently outputs a light beam B. The output light beam B is reflected by a mirror 18 that is driven to swing, and is emitted to the outside through an optical window 94. The light receiving unit 92 receives light reflected from an object that is irradiated with the light beam B. The light detected by the light receiving unit 92 is converted into an electrical signal, which is used to calculate the distance to the object.

[0013] As shown in Fig. 2, the swing actuator 5 includes a mirror unit 10, a swing motor 20, and an encoder 30. The mirror unit 10 includes a base 11, a spindle 13, a position holder 16, a holder 17, and a mirror 18. The base 11 includes a mounting unit 111 and holding walls 112 and 113, which are integrally formed from, for example, metal. The mounting unit 111 is attached to a base housing (not shown) with bolts or the like. The holding walls 112 and 113 are provided substantially perpendicularly on both ends of the mounting unit 111.

[0014] The spindle 13 is disposed substantially parallel to the mounting portion 111 and is rotatably supported on the base 11 by bearings 14 and 15 provided on the retaining walls 112 and 113. In this embodiment, the bearings 14 and 15 are ball bearings, but bearings other than ball bearings may also be used. The spindle 13 is formed to extend from the bearing 15 side to the outside of the base 11 toward the swing motor 20 and encoder 30. Hereinafter, the swing axis direction of the spindle 13 will be referred to simply as the "axial direction" where appropriate.

[0015] The position retaining portion 16 has an E-ring 161 and a preload spring 165, and positions the axial position of the spindle 13 while being pressed to one side in the axial direction. The E-ring 161 is provided on the axial outer side of the bearing 14, and functions to prevent the spindle 13 from coming off.

[0016] The preload spring 165 is provided between the rotor magnet 22 and the bearing 15, with one end abutting against the inner ring of the bearing 15 and the other end abutting against the rotor magnet 22. A separate member may be provided between the rotor magnet 22 and the preload spring 165. The preload spring 165 biases the spindle 13 toward the encoder 30 (toward the left in FIG. 2 ). That is, in this embodiment, no member for maintaining the axial position of the spindle 13 is provided inside the base 11, and therefore optical consideration for the position maintaining unit 16 is not required.

[0017] The holder 17 is press-fitted and fixed to the spindle 13. The mirror 18 is formed in a flat plate shape and is attached to the holder 17 so as to be symmetrical about the swing axis. By forming the holder 17 and the mirror 18 symmetrical about the swing axis, the moment of inertia during swing can be made equal in both directions.

[0018] The holder 17 and the mirror 18 are disposed inside the base 11 so that the mirror surface 181 faces away from the mounting portion 111, and are driven to swing by a swing motor 20. The mirror 18 reflects the light beam B output from the light emitting portion 91 with the mirror surface 181, and emits the light beam B to the outside in a direction according to the swing position of the mirror 18, thereby scanning the light beam B within a preset scanning range.

[0019] The oscillation motor 20 is provided on one axial side of the mirror unit 10. The oscillation motor 20 includes a stator 21 and a rotor magnet 22. The stator 21 is fixed to the holding wall 113 with bolts or the like. The stator 21 is provided with an electromagnetic coil and a fixed magnet (not shown). The rotor magnet 22 is a cylindrical two-pole magnet, and the spindle 13 is inserted into an axial hole 221 and fixed to the spindle 13 by a magnet fixing member 23.

[0020] The rotor magnet 22 is a so-called inner rotor that is disposed inside the stator 21, and oscillates around a stationary position when current is applied to the electromagnetic coil. Here, "oscillation" refers to a motion that periodically repeats forward and reverse rotation within a predetermined angular range less than 360°. When current is turned off to the electromagnetic coil, the rotor magnet 22 returns to its stationary position due to the magnetic force of the fixed magnet and becomes stationary. The size of the rotor magnet 22 can be designed as desired depending on mounting constraints, the required magnetic force, etc.

[0021] The encoder 30 is, for example, a reflective optical encoder, and has a disk hub 31, a disk 32, and a detection element 33, and is housed in a case 35. The disk hub 31 is press-fitted and fixed to the spindle 13. The disk 32 is attached to the disk hub 31 and rotates integrally with the spindle 13. Reflective and non-reflective patterns are formed on the disk 32 in the circumferential direction.

[0022] The detection element 33 is mounted on a substrate 34. The detection element 33 is an optical sensor that emits LED light, receives light reflected in response to the rotation of the disk 32, and detects the rotation position of the disk 32 based on changes in the amount of received light. This allows the encoder 30 to detect the oscillation positions of the oscillation motor 20 and the mirror 18. The substrate 34 is fixed to a case 35 with screws or the like (not shown). A through hole 341 is formed in the substrate 34, and the spindle 13 is inserted through it.

[0023] The case 35 is formed in a cylindrical shape with a bottom that opens on the side opposite the mirror unit 10, and is fixed to the stator 21 by, for example, a through bolt (not shown). An insertion hole 352 is formed in the bottom 351, and the spindle 13 is inserted through the insertion hole 352. The bottom 351 is located between the rotor magnet 22 and the disk hub 31. In this embodiment, the base 11, the stator 21, and the case 35, which do not move even when the oscillating motor 20 is driven, are referred to as the housing unit 50.

[0024] In this embodiment, the axial position of the spindle 13 is restricted by the E-ring 161 and the preload spring 165, and the spindle 13 is biased in the opposite direction to the E-ring 161 (i.e., to the left on the page) by the preload spring 165. If vibration or impact is applied to the swing actuator 5 and the spindle 13 moves in the axial direction, the mirror 18 may come into contact with the base 11, potentially damaging the mirror 18.

[0025] When an impact is applied to the swing actuator 5, the movement of the spindle 13 to the left in the drawing is restricted by the E-ring 161. On the other hand, when an impact exceeding the load of the preload spring 165 is received, there is a risk that the spindle 13 will move to the right in the drawing. In order to be able to withstand a larger impact, it is possible to increase the spring force of the preload spring 165, but in that case, the size of the spindle 13 will increase. Hereinafter, the direction in which the spindle 13 moves when an impact exceeding the spring force of the preload spring 165 is received (i.e., the right in the drawing) will be referred to as the "axial movement direction."

[0026] In this embodiment, there is provided a location where the clearance between the member fixed to the spindle 13 and the housing 50 is smaller than the clearance C1 between the mirror 18 and the retaining wall 112 of the base 11 in the axial movement direction. Specifically, the clearance C2 between the disk hub 31 and the bottom 351 of the case 35 is smaller than the clearance C1 between the mirror 18 and the retaining wall 112.

[0027] As a result, when an impact greater than the load of the preload spring 165 is applied to the swing actuator 5 and the spindle 13 moves in the axial movement direction, the disk hub 31 abuts against the case 35 before the mirror 18 abuts against the base 11, so the mirror 18 does not collide with the base 11 and damage to the mirror 18 can be prevented.

[0028] Furthermore, if the disk hub 31 comes into contact with the case 35 due to movement of the spindle 13 caused by vibration or impact, and the disk hub 31 is deformed or damaged, the positional relationship between the disk 32 and the detection element 33 becomes abnormal, causing a sensing abnormality. This makes it possible to detect an abnormality in the swing actuator 5.

[0029] As described above, the distance measuring device 1 of this embodiment measures the distance to an object by scanning light externally and detecting the light reflected by the object, and is equipped with a mirror 18, a base 11, a spindle 13, a position holding unit 16, and a disk hub 31.

[0030] The mirror 18 is driven to swing by a swing motor 20, thereby scanning the light to the outside. The mirror 18 is provided inside the base 11. The spindle 13 has the mirror 18 fixed thereto and is rotatably supported by the base 11 with at least one end thereof protruding from the base 11. The position holder 16 has a preload spring 165 that biases the spindle 13 toward one side in the axial direction, and an E-ring 161 that restricts movement of the spindle 13 in the biasing direction, and holds the axial position of the spindle 13. The disk hub 31 is fixed to the spindle 13 outside the base 11.

[0031] The fixed portion that includes the base 11 and is not driven by the swing motor 20 is referred to as the housing 50. The distance between the end of the disk hub 31 on the side opposite to the biasing direction of the spindle 13 and the housing 50 is smaller than the distance between the end of the mirror 18 on the side opposite to the biasing direction of the spindle 13 and the base 11. Specifically, the clearance C2 between the disk hub 31 and the bottom 351 of the case 35 is smaller than the clearance C1 between the mirror 18 and the retaining wall 112.

[0032] As a result, when an impact greater than the load of the preload spring 165 is applied to the oscillation actuator 5, the disk hub 31 abuts against the case 35, preventing the mirror 18 from colliding with the base 11. Therefore, damage to the mirror 18 can be prevented. Furthermore, when providing a structure inside the base 11 that abuts against the base 11 before the mirror 18, optical considerations such as avoiding high reflection are necessary. In this embodiment, the disk hub 31, which is the abutting member, is provided outside the base 11, so optical considerations and restrictions for providing an abutting structure can be reduced.

[0033] The distance measuring device 1 is provided with an oscillating motor 20 and an encoder 30 capable of detecting the oscillating position of the mirror 18 on the outside of the base 11. The encoder 30 has a disk 32 that is driven integrally with the spindle 13, a disk hub 31 that is fixed to the spindle 13 and to which the disk 32 is attached, and a detection element 33 that detects the driving state of the disk 32. In detail, the detection unit is the encoder, and the detection element 33 is an optical sensor that detects light reflected by the disk 32.

[0034] In this embodiment, the contact member is the disk hub 31. By configuring the disk hub 31 to contact the case 35 when an impact is applied to the oscillating actuator 5, an abnormality in the oscillating actuator 5 can be detected.

[0035] The position holding unit 16 is provided outside the base 11. In other words, no member related to maintaining the axial position of the spindle 13 is provided inside the base 11. The position restricting unit is an E-ring 161 provided on the opposite side of the base 11 from the preload spring 165. This allows the axial positioning of the spindle 13 to be determined without affecting the light scanning by the mirror 18.

[0036] Second Embodiment A second embodiment is shown in FIG. 3 . In this embodiment, the shape of the spindle 130 differs from that of the above-described embodiment, and this point will be mainly described. In the spindle 130 of this embodiment, a shaft portion 131 and a position restricting portion 132 are integrally formed. The position restricting portion 132 is provided axially outside the bearing 14, protruding radially outward from the shaft portion 131, and functions to prevent the spindle 130 from coming off. That is, in this embodiment, the preload spring 165 and the position restricting portion 132 constitute the position retaining portion 16. Even with this configuration, the same effects as the above-described embodiment can be achieved.

[0037] In the embodiment, the spindles 13 and 130 correspond to the "oscillating shaft," the E-ring 161 and the position regulating portion 132 correspond to the "position regulating portion," the preload spring 165 corresponds to the "biasing member," the encoder 30 corresponds to the "detection portion," the disk hub 31 corresponds to the "contact member" and "holding member," and the disk 32 corresponds to the "detected portion."

[0038] (Other Embodiments) In the above embodiment, the clearance C2 between the disk hub 31 and the bottom 351 of the case 35 is smaller than the clearance C1 between the mirror 18 and the retaining wall 112. In other embodiments, the abutting member may be a member other than the disk hub. That is, a location may be provided where the clearance between the end of a member other than the disk hub on the axial movement direction side and the housing is smaller than the clearance C1. Note that if the abutting member is provided inside the base, optical considerations must be taken so as not to interfere with reflection on the mirror, so it is desirable to provide the abutting member on the outside of the base.

[0039] In the above embodiment, the detection element is an optical sensor. In other embodiments, something other than an optical sensor (for example, a magnetic sensor) may be used to detect the drive state of the oscillation shaft, and something other than an encoder may be used as the detection unit. Also, in other embodiments, the actuator and mirror unit may have different configurations and arrangements from those in the above embodiment as long as they can oscillate the mirror. As described above, the present disclosure is not limited to the above embodiment and can be implemented in various forms without departing from the spirit thereof.

[0040] The present disclosure has been described based on the embodiments. However, the present disclosure is not limited to the embodiments and structures. The present disclosure also encompasses various modifications and variations within the scope of equivalents. Furthermore, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A distance measuring device that scans light outward and measures the distance to an object by detecting light reflected by the object, comprising: a mirror (18) that scans light outward by being driven to swing by an actuator (20); a base (11) in which the mirror is provided; a swing shaft (13, 130) to which the mirror is fixed and which is swingably supported by the base with at least one end protruding from the base; a position retaining section (16) that has a biasing member (165) that biases the swing shaft to one side in the axial direction and a position restricting section (161, 132) that restricts movement of the swing shaft in the biasing direction, and that retains the axial position of the swing shaft; and an abutment member (31) fixed to the swing shaft on the outside of the base, wherein if a fixed section that includes the base and is not driven by the actuator is a housing section (50), then: A distance measuring device, wherein the distance between the end of the abutment member on the side opposite to the biasing direction of the oscillating shaft and the housing portion is smaller than the distance between the end of the mirror on the side opposite to the biasing direction of the oscillating shaft and the base.

2. A detection unit (30) capable of detecting the actuator and the oscillating position of the mirror is provided on the outside of the base, the detection unit having a detectable part (32) that is driven integrally with the oscillating shaft, a holding member (31) fixed to the oscillating shaft and to which the detectable part is attached, and a detection element (33) that detects the driving state of the detectable part, and the abutment member is the holding member.A distance measuring device as described in claim 1.

3. A distance measuring device according to claim 2, wherein the detection section is an encoder, and the detection element is an optical sensor that detects light reflected by the detection target section.

4. A distance measuring device as described in any one of claims 1 to 3, wherein the position maintaining portion is provided on the outside of the base, and the position regulating portion is an E-ring provided on the opposite side of the base to the biasing member.

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