Position detection device

Abstract

Position detection device (20) comprising: a magnet (33) having a first magnetic pole (55) and a second magnetic pole (56); a magnetic sensor (34) detecting a change in magnetic flux (M) generated by a detection target (22) located on the side of the first magnetic pole (55) of the magnet (33) between the magnet (33) and the magnetic sensor (34); a magnetic shield (40, 40B to 40K) comprising a magnetic material arranged on the side of the second magnetic pole (56) of the magnet (33) and configured to shield against an interfering magnetic field;and a housing (23) containing the magnet (33), the magnetic sensor (34) and the magnetic shield (40, 40B to 40K), wherein the magnetic shield (40, 40B to 40K) comprises a first shielding wall (41, 41C, 41D, 41E, 41I, 41K) extending in a direction intersecting a magnetic pole direction in which the first magnetic pole (55) and the second magnetic pole (56) are aligned in parallel, and a second shielding wall (42, 42b, 42F, 42G, 42H, 42J) extending from the first shielding wall (41, 41C, 41D, 41E, 41I, 41K) in the magnetic pole direction such that it is located on one side of the magnet (33), and wherein the magnetic shield (40, 40B to 40K) is arranged in the housing (23) such that a first magnetic gap (X1) is formed between the magnet (33) and the first shielding wall (41, 41C, 41D, 41E, 41I, 41K) and a second magnetic gap (X2, X3) is formed between the magnet (33) and the second shielding wall (42, 42b, 42F, 42G, 42H, 42J).

Description

Technical field The invention relates to a position detection device. State of the art A position detection device for detecting a relative position between two components whose positional relationship changes is known from the prior art. It comprises a magnet and a magnetic sensor for detecting a change in a magnetic flux generated by a detection target that occurs between the magnet and the magnetic sensor. For example, the position sensing device disclosed in US 2003 / 0117000A (Reference 1) comprises a housing having a pair of arm units arranged facing each other, and a magnet and a magnetic sensor spaced apart from each other at two positions by being held separately in the respective arm units. The position sensing device is, for example, arranged in a vehicle seat adjustment mechanism. A design is used in which the position sensing device acts as a seat position sensor to detect a relative position of two sliding rails extending from them in a direction of extension, that is, a seat adjustment position. The housing is attached to one of the slide rails in the position detection device. A detection target, such as a plate-shaped component made of an iron-based metal, is arranged in the slide rail on the opposite side. Furthermore, the detection target is positioned so that the two slide rails forming the seat-shifting device move relative to each other, causing the detection target to enter and exit between the two arm units of the housing.In this way, the position detection device can detect, based on a change in magnetic flux detected by the magnetic sensor, whether the seat sliding position is either in a first position (for example, a front position) where the detection target enters between the two arm units of the housing, or in a second position (for example, a rear position) where the detection target does not enter between the two arm units. This position detection device has a problem in that foreign substances (magnetic bodies) can adhere to the housing and be attracted by the magnet's magnetic force. The foreign substance then gets between the magnetic sensor and the magnet, potentially leading to faulty detection. In light of this, the position detection device described above is, according to the prior art, equipped with a housing, specifically with a cover to close an opening between the two arm units. This cover prevents faulty detection caused by the ingress of foreign substances. However, the technology described above, according to the prior art, employs a setup in which the detection target presses against the cover component and opens it when it enters a detection position set between the two arm units. Consequently, when the detection target comes into contact with the cover component, there is a possibility of generating contact noise or abrasive dust. Furthermore, the inclusion of the cover component can increase manufacturing costs. In this respect, the technology described above has room for improvement. From CH 702 193 A2 and DE 40 07 200 A1 (principal documents 2 and 3) a position detection device is known which strengthens the magnetic force between the magnet and the magnetic sensor, but does not offer any further protection against faulty detection. Finally, US 2004 / 0164826A1 (Reference 4) discloses a position detection device arranged within a seat sliding device made of magnetic material, which thus shields the position detection device from an interfering magnetic field. Brief description There is a need for a position detection device that can prevent foreign substance adsorption through a simpler design and shield against a disruptive magnetic field. According to the invention, the above requirement is met by a position detection device comprising the features of claim 1. In the position detection device according to the invention, a magnetic flux path is formed that passes through a magnetic shield, thereby shielding the magnetic flux of the magnet that runs opposite to the direction in which the magnetic sensor is arranged, i.e., the magnetic flux on the side of the second magnetic pole. This can prevent foreign substance adsorption by means of a simple design. In particular, the magnetic flux of the magnet on the side of the second magnetic pole can be shielded more effectively by the first shielding wall, which propagates in a direction that intersects a magnetic pole direction in which the first and second magnetic poles are aligned in parallel. The shielding effect of the magnetic shield can be further improved by the second shielding wall, which extends from the first shielding wall in the direction of the magnetic poles and is thus arranged on one side of the magnet.As a result, it is more effectively possible to prevent foreign substance adsorption. In the position detection device, it is preferable that the detection target comprises a support section arranged on the side of the magnet and a detection target section that is supported by the support section in such a way that it is positioned between the magnet and the magnetic sensor. The second shielding wall is preferably arranged between the magnet and the support section of the detection target. Specifically, if a magnetic flux path is formed that passes through the detection target, there is a possibility that the magnetic flux passing through the support section located on the side of the magnet will attract the foreign substance on the side opposite to the direction in which the magnetic sensor is oriented, i.e., on the side of the second magnetic pole. However, in the design described above, a magnetic flux collection process of the second shielding wall, which faces the support section of the detection target, can strengthen the magnetic flux path passing through the magnetic shield. This can prevent foreign substance adsorption caused by the magnetic flux passing through the support section of the detection target. In the position detection device, it is preferable that the second shielding wall is arranged in a position in which it is positioned between the magnet in the direction in which the detection target enters. In the position detection device, it is preferable that a distant end section of the second shielding wall is located on the side of the first shielding wall instead of on an end surface of the first magnetic pole of the magnet. This means that a magnetic flux path is formed that passes through the first shielding wall, which is located on the side of the second magnetic pole, thereby strengthening the magnetic force on the side of the first magnetic pole. This increases the magnetic flux passing through the magnetic sensor (the achievable magnetic force), thus improving the accuracy in detecting the target. However, due to the magnetic flux collection process of the second shielding wall, magnetic flux components of the magnet that travel along the magnetic pole direction toward the magnetic sensor side are attracted to the transverse side where the second shielding wall is located. This creates the possibility of a lower magnetic flux passing through the magnetic sensor. In this respect, with the design described above, it is less likely that the magnetic flux components of the magnet will accumulate along the magnetic pole direction on the second shielding wall. This can ensure higher detection accuracy by preventing a decrease in the magnetic flux passing through the magnetic sensor, while simultaneously preventing foreign substance adsorption due to the shielding effect of the second shielding wall. In the position detection device, it is preferable that the first shielding wall has a projection that extends towards the magnet side. With the design described above, it is possible to strengthen the magnetic force of the magnet on the side of the first magnetic pole. This can increase the magnetic flux passing through the magnetic sensor. Therefore, it is possible to improve the accuracy in detecting the target. In the position detection device, it is preferable that the first shielding wall has a curved surface which has a central section at a position where the first shielding wall faces the magnet. With the design described above, a stabilized output of the magnetic force can be expected, in particular an advantageous effect that reduces the influence of a misalignment in the direction intersecting the magnetic pole direction. For the position detection device, it is preferable that it be arranged in a seat-sliding device which has a stationary component and a movable component, the latter being arranged to be relatively movable with respect to the stationary component. Preferably, the magnetic sensor and the magnet are arranged on the side of the movable component of the seat-sliding device. Preferably, the detection target is arranged on the side of the stationary component of the seat-sliding device, and the magnet is arranged below the magnetic sensor. In a design where the magnet is located below the magnetic sensor, it is likely that a foreign substance will be adsorbed onto a surface located on the side of the second magnetic pole. However, because the magnetic shield is located on the side of the second magnetic pole, it is less likely that the magnet's magnetic force will reach the foreign substance on the surface. This can effectively prevent foreign substance adsorption even when the position sensing device is located within the seat sliding mechanism, as in the design described above. The invention therefore makes it possible to prevent foreign substance adsorption by means of a simpler design. Brief description of the drawings The foregoing and further features and characteristics of this invention will become more fully apparent from the following detailed description, which refers to the accompanying drawings, which show: Fig. 1 a schematic configuration drawing of a vehicle seat and a position detection device arranged in a seat sliding mechanism thereof; Fig. 2 a perspective view of the seat sliding mechanism and the position detection device; Fig. 3 a side view of the position detection device; Fig. 4 a sectional view of the position detection device (sectional view along line IV-IV in Fig. 3); Fig. 5 a view to describe a mode of operation of the position detection device and a magnetic shield arranged in the position detection device (when a detection target is not reached); Fig.6 a view to describe a mode of operation of the position detection device and the magnetic shield arranged in the position detection device (when the detection target is reached); Figs. 7A to 7G sectional views showing designs of a magnetic shield according to further examples; Fig. 8 a sectional view of the position detection device showing a design of the magnetic shield according to a further example (sectional view along line VIII-VIII in Fig. 4); and Figs. 9A to 9C sectional views showing designs of the magnetic shield according to further examples. Detailed description The following describes, with reference to the drawings, a position detection device that is arranged in a vehicle seat sliding device. As shown in Fig. 1, a vehicle seat 1 has a seat cushion 2 and a seat backrest 3, which is arranged so that it can be tilted relative to a rear end section of the seat cushion 2. A pair of right and left lower rails 5 are arranged on a floor 4 of the vehicle, extending longitudinally along the vehicle. Furthermore, upper rails 6 are mounted on each of the lower rails 5 and are movable relative to them along one direction of extension. The seat 1 according to the embodiment disclosed herein is supported above a seat sliding device 10, which is formed by the lower rails 5 and the upper rails 6. As shown in Figures 1 and 2, the seat sliding device 10, according to the embodiment disclosed herein, has a position detection device 20 which detects a relative movement position of the upper rails 6 with respect to the lower rails 5 attached to the floor 4, that is, a sliding position of the seat 1 supported above the seat sliding device 10. The lower rail 5 corresponds to a fixed component, and the upper rail 6 corresponds to a movable component. As shown in Figs. 1, 2 to 3, the position detection device 20 according to the embodiment disclosed here more precisely comprises a device main body 21, which is arranged on the side of the upper rail 6 of the seat sliding device 10, and a detection target 22, which is arranged on the side of the lower rail 5. As shown in Figures 2, 3 to 4, the detection target 22, according to the embodiment disclosed herein, comprises a vertical wall section 22a, which is erected on one side of the lower rail 5, and a flange-shaped, horizontal wall section 22b, which extends from an upper end of the vertical wall section 22a in the width direction of the lower rail 5 to the outside (right side in Figure 4). In the embodiment disclosed herein, the detection target 22 is formed by a forming process (rolling process) on a plate component made of an iron-based metal. In the seat-shifting device 10 according to the embodiment disclosed herein, the detection target 22 is assembled with the lower rail 5 such that it is arranged on one side of the lower rail 5. In contrast, the main body of the device 21 according to the embodiment disclosed herein comprises a housing 23 which is attached to the upper rail 6. In particular, in the embodiment disclosed herein, the housing 23 is attached to the upper rail 6 by means of a retaining clip 24 such that it is arranged on one side of the upper rail 6. The housing 23 has a detection opening 25 which is designed such that a side surface 23a on the side of the upper rail 6, which extends in the direction of extension (transverse direction in Fig. 3) of the upper rail 6, is cut into a slot shape. The main body of the device 21 according to the embodiment disclosed herein employs a design in which the horizontal wall section 22b of the detection target 22 described above enters and exits the interior of the detection opening 25 based on the relative movement of the upper rail 6 with respect to the lower rail 5. As shown in Fig. 1, the main body of the device 21, according to the embodiment disclosed herein, is designed to output a detection signal S that can determine whether the horizontal wall section 22b of the detection target 22 has entered the interior of the detection opening 25 or not. According to the embodiment disclosed herein, a connector section 26 for power supply and signal output is arranged at one end of the housing 23 (see Fig. 2 and Fig. 3). Furthermore, the detection signal S output by the main body of the device 21 is input into an ECU 30, which functions as a detection determination unit. In this way, the position detection device 20, according to the embodiment disclosed herein, can detect a relative position of the upper rail 6 with respect to the lower rail 5, that is, a seat displacement position. As shown in Figures 1 and 2, the position detection device 2, according to the embodiment disclosed herein, is brought into a state in which the detection target 22 (the horizontal wall section 22b of the detection target 22) enters the interior of the detection opening 25 formed in the main body of the device 21 when the seat 1, which is carried above the upper rail 6, is moved towards the front of the vehicle. This means that, according to the embodiment disclosed herein, the ECU 30 determines, based on the detection signal S emitted by the main body of the device 21, whether the seat's position is either a first position, where the seat 1 has been moved towards the front of the vehicle, or a second position, where the seat 1 has been moved towards the rear of the vehicle.In this way, the position detection device 20 according to the embodiment disclosed here can, for example, perform optimized deployment control for an airbag (not shown) based on the detected seat displacement position in the vehicle. As shown in Figures 3 and 4, the housing 23, according to the embodiment disclosed herein, more precisely comprises a pair of arm units 31 and 32, which are installed parallel to each other in a vertically opposed position across the detection opening 25 described above. The position detection device 20, according to the embodiment disclosed herein, comprises a magnet 33 and a magnetic sensor 34, which are arranged spaced apart from the two arm units 31 and 32. In particular, the housing 23 is attached to the upper rail 6 such that the magnet 33 is provided in the first arm unit 31, which is arranged on the underside (bottom in each drawing), and that the magnetic sensor 34 is provided in the second arm unit 32, which is arranged on the top side (top in each drawing). According to the embodiment disclosed herein, the magnet 33 is embedded in the first arm unit 31 in such a state that an N-pole (first magnetic pole) 55 faces the top side, that is, in such a state that the N-pole 55 faces the side of the magnetic sensor 34 held by the second arm unit 32. According to the embodiment disclosed herein, the magnetic sensor 34 is embedded in the second arm unit 32 at a position where the magnetic sensor 34 is opposite a magnetic pole center of the magnet 33 (position on the line L in Fig. 4). The housing 23 according to the embodiment disclosed herein is formed in one piece by means of an insert molding process in which the magnet 33 is overmolded with resin. A Hall element is used as the magnetic element of the magnetic sensor 34. The magnetic sensor 34 according to the embodiment disclosed herein is molded with resin in a receiving recess 32a formed in the second arm unit 32. As shown in Fig. 5, the position detection device 20 according to the embodiment disclosed here employs a design in which a magnetic flux M of the magnet 33 held in the first arm unit 31 of the housing 23 passes through the detection opening 25 and the magnetic sensor 34 held in the second arm unit 32. As shown in Fig. 6, the horizontal wall section 22b of the detection target 22 enters the interior of the detection opening 25 due to the relative movement of the upper rail 6 with respect to the lower rail 5, thereby forming a new magnetic flux path that passes through the detection target 22, which is made of a magnetic material. This means that the magnetic flux M of the magnet 33, which extends towards the side of the second arm unit 32 on which the magnetic sensor 34 is arranged, is shielded. In this way, the position detection device 20, according to the embodiment disclosed herein, is designed such that the magnetic flux M of the magnet 33 does not reach the magnetic sensor 34. The magnetic sensor 34 according to the embodiment disclosed herein detects a change in the magnetic flux generated by the detection target 22, which thus enters between the magnetic sensor 34 and the magnet 33. The main body of the device 21 according to the embodiment disclosed herein is designed to output a signal from the magnetic sensor 34, as the detection signal S described above, to the ECU 30. As shown in Fig. 4, the position detection device 20 according to the embodiment disclosed here has a magnetic shield 40 which has a magnetic gap (air gap) X between the magnet 33 and the magnetic shield 40 and which is made of a magnetic material which is arranged below the magnet 33, i.e. on the side of a second magnetic pole (S-pole) 56 opposite to the first magnetic pole (N-pole) 55, which faces the top side on which the magnetic sensor 34 is located.More precisely, the magnetic shield 40 is formed by a deformation process on an iron-based metal (for example, by bending a sheet material). Specifically, the magnetic shield 40 comprises a first shielding wall 41 extending in a direction that intersects a magnetic pole direction (direction along the line L, which runs vertically in Fig. 4) in which the first magnetic pole (N pole) 55 and the second magnetic pole (S pole) 56 of the magnet 33 are aligned parallel, thus extending in its perpendicular plane. Furthermore, the magnetic shield 40 has a second shielding wall 42 extending from one end of the first shielding wall 41 in the magnetic pole direction described above, such that it is located on one side of the magnet 33 (left side in Fig. 4).In the position detection device 20 according to the embodiment disclosed herein, the magnetic shielding 40 in the first arm unit 31 of the housing 23 is held in a state in which the second shielding wall 42 is arranged between the magnet 33 and the vertical wall section 22a of the detection target 22. According to the embodiment disclosed herein, the side surface 23a on the side of the upper rail 6 in the first arm unit 31 has a recess 44 extending in the longitudinal and vertical directions (see the transverse and vertical directions in the drawing in Fig. 3) of the upper rail 6. One end on the lower side of the recess 44 has an insertion recess 45 extending downwards from the magnet 33. The magnetic shield 40 according to the embodiment disclosed herein is attached to the first arm unit 31 such that the first shielding wall 41 is inserted into the insertion recess 45. The second shielding wall 42 is housed in the recess 44 in a state in which a further end section 42a, extending from an end section of the first shielding wall 41, is arranged in a vertical position approximately equal to the position of an end face of the first magnetic pole (end face of the N-pole) 33a of the magnet 33. In this way, according to the embodiment disclosed herein, the magnetic shield 40 forms a predetermined magnetic gap X1 between the first shielding wall 41 and the magnet 33, and a predetermined magnetic gap X2 between the second shielding wall 42 and the magnet 33. In this state, the magnetic shield 40 is held below the magnet 33. As shown in Figures 5 and 6, this means that the magnetic shield 40 is arranged on the side of the second magnetic pole (on the S-pole side) 56 of the magnet 33, thereby forming a magnetic flux path that passes through the first shielding wall 41, which is arranged below the magnet 33, and the second shielding wall 42, which is arranged on the side of the magnet 33. In this way, the position detection device 20, according to the embodiment disclosed herein, is designed to shield the magnetic flux M of the magnet 33, which extends to the underside of the housing 23, in such a way as to prevent a foreign substance from being adsorbed onto the housing 23 (a lower surface 23b of the housing 23). As described above, the following advantageous effects can be achieved according to the embodiment disclosed herein. (1) The magnetic shield 40 comprises the first shielding wall 41, which extends in the direction intersecting the magnetic pole direction in which the first magnetic pole (N-pole) 55 and the second magnetic pole (S-pole) 56 of the magnet 33 are aligned in parallel. The use of this design can effectively shield the magnetic flux M of the magnet 33, which extends to the side opposite to the first magnetic pole (N-pole) 55, which faces the side of the magnetic sensor 34. In this way, it is possible to prevent foreign substance adsorption. Particularly in a configuration where the magnet 33 is located below the magnetic sensor 34, it is likely that a foreign substance on the base 4 will be adsorbed on the side of the second magnetic pole (S-pole) 56. However, according to the configuration described above, it is less likely that the magnetic force (the returning magnetic flux) of the magnet 33 will reach the foreign substance on the base 4. In this way, it is possible to effectively prevent foreign substance adsorption. A magnetic flux path is formed that passes through the magnetic shield 40, which is located on the side of the second magnetic pole (S-pole) 56 of the magnet 33, thereby strengthening the magnetic force on the side of the first magnetic pole (N-pole) 55. This increases the magnetic flux passing through the magnetic sensor 34 (the achievable magnetic force). Accordingly, it is possible to improve the accuracy in detecting the detection target 22. As a result, it is possible to prevent the problem of variations in the separation distance between the magnet 33 and the magnetic sensor 34 caused by manufacturing and assembly errors. Furthermore, the magnetic shielding 40 can block a disruptive magnetic field. This makes it possible to extend the lifespan by minimizing demagnetization caused by the disruptive magnetic field. (2) The magnetic shield 40 comprises the second shielding wall 42, which extends from the first shielding wall 41 in the direction of the magnetic pole such that it is located on the side of the magnet 33. In this way, the shielding effect of the magnetic shield 40 can be improved. As a result, it is more effective in preventing the adsorption of foreign substances. It is then possible to minimize the influence of the interfering magnetic field. Particularly in a configuration where the vertical wall section 22a, which forms the support section of the detection target 22, is located on the side of the magnet 33, it is likely that the magnetic force of the magnet 33 will reach a foreign substance on the floor 4, as a magnetic flux path is formed that passes through the vertical wall section 22a. However, according to the configuration described above, the magnetic flux path passing through the magnetic shield 40 can be strengthened by the magnetic flux collection process of the second shielding wall 22, which is positioned opposite the vertical wall section 22a of the detection target 22. This reduces the magnetic flux reaching the foreign substance on the floor 4 of the vehicle. It is therefore possible to effectively prevent foreign substance adsorption. The embodiment described above can be modified as follows. In the embodiment described above, the magnetic shield 40 comprises the first shielding wall 41, which extends in the plane perpendicular to the magnetic pole direction in which the first magnetic pole (N pole) 55 and the second magnetic pole (S pole) 56 of the magnet 33 are aligned parallel, and the second shielding wall 42, which extends from one end of the first shielding wall 41 in the magnetic pole direction such that it is located on the side of the magnet 33. The second shielding wall 42 is located between the magnet 33 and the vertical wall section 22a of the detection target 22. However, the design of the magnetic shield 40 can be modified at will, without being limited thereto. For example, as in the magnetic shield 40B shown in Fig. 7A, a design can be used in which the second shielding wall 42 is also formed in a different position than the position in which the second shielding wall 42 is arranged between the magnet 33 and the vertical wall section 22a of the detection target 22. As shown in Fig. 8, a design can also be used in which, in the transverse direction of the drawing, i.e., in the direction in which the upper rail 6 moves relative to the lower rail 5, causing the detection target 22 (the horizontal wall section 22b of the detection target 22) to enter and exit the detection opening 25 of the main body of the device 21, the second shielding walls 42 (42b and 42c) of the magnetic shield 40B are formed at two positions, enclosing the magnet 33. That is, a design can be used in which the second shielding wall 42 is provided, which is arranged between the vertical wall section 22a of the detection target 22 and the magnet 33 (see Fig. 4), and in which, in addition, a second shielding wall 42 is arranged such that the magnet 33 is surrounded in three directions. In the design shown in Fig.In the position detection device 20B shown in Figure 8, predetermined magnetic gaps X3 are formed between the second shielding walls 42b and 42c and the magnet 33. This makes it possible to achieve a better shielding effect. A design can be used in which the second shielding wall 42 extends over the entire circumferential edge of the first shielding wall 41. Alternatively, a design can be used in which the second shielding wall 42 is partially omitted at the circumferential edge of the first shielding wall 41. For example, as in the magnetic shield 40C shown in Fig. 7B, a design can be used which has a first shielding wall 41C having a projection 51 that extends towards the side of the magnet 33. In this way it is possible to strengthen the magnetic force more effectively on the side of the first magnetic pole (N-pole) 55. • Furthermore, for example, as in the magnetic shield 40D shown in Fig. 7C, a design can be used which includes a first shielding wall 41D having a curved surface 52 which has a central section 52a at a position opposite the magnet 33 and projecting to the side of the magnet 33.In this way, the magnetic force on the side of the first magnetic pole 55 is strengthened, and a stabilized output of the magnetic force can be expected, in particular an advantageous effect that reduces the influence of a misalignment in the direction intersecting the magnetic pole direction (vertical direction in the drawing). For example, as in the magnetic shield 40E shown in Fig. 7D, a design can be used which comprises a first shielding wall 41E with a curved surface 53 which has a central section 53a at a position opposite the magnet 33 and is recessed towards the side of the magnet 33. Even when this design is used, a stabilized output of the magnetic force can be expected.7E shows a magnetic shield 40F in a design in which the far end section 42a of a second shielding wall 42F, which extends from one end of the first shielding wall 41 along the magnetic pole direction, is located on the side of the first shielding wall 41 (underside in the drawing) instead of on an end surface from the first magnetic pole 33a of the magnet 33. Specifically, due to the magnetic flux collection process of the second shielding wall 42, magnetic flux components of the magnet 33, which propagate along the magnetic pole direction towards the side of the magnetic sensor 34, are attracted to the transverse side on which the second shielding wall 42 is located. This results in a potentially lower magnetic flux passing through the magnetic sensor 34. However, according to the design described above, it is less likely that the magnetic flux components along the magnetic pole direction (vertical direction in the drawing) will be collected on the second shielding wall 42F. This can ensure high detection accuracy by preventing a decrease in the magnetic flux passing through the magnetic sensor 34, while simultaneously preventing foreign substance adsorption and any interfering influence resulting from the shielding effect of the second shielding wall 42F. For example, as in the magnetic shield 40G shown in Fig. 7F, a flange section 54 can be formed in the far end section 42a of a second shielding wall 42G. While this minimizes the decrease in the magnetic flux components along the magnetic pole direction, it can increase the magnetic flux passing through the magnetic sensor 34. For example, as in the magnetic shield 40H shown in Fig. 7G, a design is not excluded in which the far end section 42a of a second shielding wall 42H is located on the side of the magnetic sensor 34 (top side in the drawing) instead of on the end face of the first magnetic pole 33a of the magnet 33. For example, as in the magnetic shield 40I shown in Fig. 9A, a first shielding wall 41I does not necessarily have to extend in a plane perpendicular to the magnetic pole direction. For example, as in the magnetic shield 40I shown in Fig. 9A, a first shielding wall 41I does not necessarily have to extend in a plane perpendicular to the magnetic pole direction.In the magnetic shield 40J shown in Fig. 9B, a second shielding wall 42J does not run parallel to the magnetic pole direction. For example, as in the magnetic shield 40K shown in Fig. 9C, a design can be used that includes a first shielding wall 41K which is configured such that a section opposite the magnet 33 is spaced away from the magnet 33. This means that the magnetic shield does not necessarily have to strengthen the magnetic force on the side of the first magnetic pole 55. In the embodiment described above, the magnet 33 is arranged below the magnetic sensor 34. However, the positional relationship can be changed, for example, by using a design in which the magnetic sensor 34 is arranged below the magnet 33, or a design in which the magnet 33 and the magnetic sensor 34 are arranged horizontally parallel.• In the embodiment described above, the Hall element is used as the magnetic element of the magnetic sensor 34. However, other magnetic elements, such as a magnetoresistive element, can be used. • In the embodiment described above, a configuration has been described in which the N pole of the magnet 33 serves as the first magnetic pole 55, so that the magnetic sensor 34 is arranged on the side of the first magnetic pole 55, and in which the magnetic shield 40 is arranged on the side of the S pole, which serves as the second magnetic pole 56. However, a configuration can be used in which the S pole of the magnet 33 serves as the first magnetic pole 55 and the N pole as the second magnetic pole 56.• In the embodiment described above, the vertical wall section 22a, which forms the support section, and the horizontal wall section 22b, which forms the detection target section, are formed in one piece in the detection target 22 by carrying out a deformation process on a sheet material. However, the design of the detection target 22 can be modified at will, without being limited to this. For example, a design can be used in which a support section and a detection target section, which were formed separately, are assembled. A design can be used in which a flat, plate-shaped detection target is employed. Furthermore, the detection target 22 need not have to be plate-shaped.If the main body of the device 21 is attached to the side of the upper rail 6 as in the embodiment described above, a configuration can be used in which a section of the lower rail 5 is used as the detection target. In the embodiment described above, the main body of the device 21 is arranged on the side of the upper rail 6, which serves as the movable component of the seat sliding device 10, and the detection target 22 is arranged on the side of the lower rail 5, which serves as the stationary component. However, without being limited to this configuration, a configuration can be used in which the detection target 22 is arranged on the side of the movable component of the seat sliding device 10 and in which the main body of the device 21 is arranged on the side of the stationary component.• For example, in the seat sliding device 10, on the side of the moving component, without being limited to the upper rail 6, a support component of the seat 1 arranged on the upper rail 6, or a structural body of the seat 1, can serve as a fixed section. For example, in the seat sliding device 10, on the side of the fixed component, without being limited to the lower rail 5, a support component for supporting the lower rail 5 on the floor 4, or the floor 4 itself, can serve as a fixed section. • In the embodiment described above, in the position detection device 10, which is used to detect the seat sliding position, the magnetic shield 40 is arranged on the side of the second magnetic pole 56 of the magnet 33.Provided that the magnetic sensor 34 is designed to detect a change in magnetic flux generated by the detection target 22 entering between the magnet 33 and the magnetic sensor 34, the magnetic shield 40, which is the same as in the embodiment described above, can also be arranged in position detection devices used for other purposes, without being limited thereto. In the embodiment described above, when the seat 1, which is carried above the upper rail 6, moves towards the front of the vehicle, the detection target 22 is brought into a state in which it enters the interior of the detection opening 25 formed in the main body 21 of the device.However, the detection target 22, without being limited to this, can be brought into a state in which it enters the interior of the detection opening 25 of the device main body 21 when the seat 1 moves towards the rear of the vehicle. In the embodiment described above, the housing 23 is formed in one piece by means of an insert molding process in which the magnet 33 is overmolded with resin. However, the magnet 33 can also be installed in the housing 23 after the housing 23 has been formed. In the embodiment described above, the magnetic sensor 34 is molded with resin into the mounting recess 32a formed in the second arm unit 32. However, the magnetic sensor 34 can, for example, be sealed with another component assembled with it (sealing component).• In the embodiment described above, the magnetic shield 40 is installed in such a way that it is inserted into the mounting recess 44 and the insertion recess 45 formed in the first arm unit 31. However, for example, a design can be used in which the magnetic shield 40 is overmolded and formed integrally with the housing 23. The preceding description outlines the principles, preferred embodiments, and operation of the invention. However, the invention to be protected is not intended to be limited by the specific embodiments disclosed herein. Furthermore, the embodiments described here are to be regarded as illustrations rather than limitations.

Claims

Position detection device (20) comprising: a magnet (33) having a first magnetic pole (55) and a second magnetic pole (56); a magnetic sensor (34) detecting a change in magnetic flux (M) generated by a detection target (22) located on the side of the first magnetic pole (55) of the magnet (33) between the magnet (33) and the magnetic sensor (34); a magnetic shield (40, 40B to 40K) comprising a magnetic material arranged on the side of the second magnetic pole (56) of the magnet (33) and configured to shield against an interfering magnetic field;and a housing (23) containing the magnet (33), the magnetic sensor (34) and the magnetic shield (40, 40B to 40K), wherein the magnetic shield (40, 40B to 40K) comprises a first shielding wall (41, 41C, 41D, 41E, 41I, 41K) extending in a direction intersecting a magnetic pole direction in which the first magnetic pole (55) and the second magnetic pole (56) are aligned in parallel, and a second shielding wall (42, 42b, 42F, 42G, 42H, 42J) extending from the first shielding wall (41, 41C, 41D, 41E, 41I, 41K) in the magnetic pole direction such that it is located on one side of the magnet (33), and wherein the magnetic shield (40, 40B to 40K) is arranged in the housing (23) such that a first magnetic gap (X1) is formed between the magnet (33) and the first shielding wall (41, 41C, 41D, 41E, 41I, 41K) and a second magnetic gap (X2, X3) is formed between the magnet (33) and the second shielding wall (42, 42b, 42F, 42G, 42H, 42J). Position detection device (20) according to claim 1, wherein the detection target (22) comprises a support section (22a) arranged on the side of the magnet (33) and a detection target section (22b) which is supported by the support section (22a) such that it is arranged at a position where the detection target section (22b) enters between the magnet (33) and the magnetic sensor (34), and wherein the second shielding wall (42) is arranged between the magnet (33) and the support section (22a) of the detection target (22). Position detection device (20) according to claim 2, wherein the second shielding wall (42) is arranged in a position to be positioned between the magnet (33) in a direction in which the detection target (22) enters. Position detection device (20) according to one of claims 1 to 3, wherein a further end section (42a) of the second shielding wall (42F) is located on the side of the first shielding wall (41) instead of on an end surface of the first magnetic pole (33a) of the magnet (33). Position detection device (20) according to one of claims 1 to 4, wherein the first shielding wall (41C) has a projection (51) that projects towards the magnet side. Position detection device (20) according to one of claims 1 to 5, wherein the first shielding wall (41D, 41E) has a curved surface (52, 53) which has a central section at a position where the first shielding wall (41D, 41E) is opposite the magnet (33). Position detection device (20) according to one of claims 1 to 6, wherein the position detection device (20) is arranged in a seat sliding device (10) which has a stationary component (5) and a movable component (6) which is arranged such that it is relatively movable with respect to the stationary component (5), wherein the magnetic sensor (34) and the magnet (33) are arranged on the side of the movable component (6) of the seat sliding device (10), wherein the detection target (22) is arranged on the side of the stationary component (5) of the seat sliding device (10) and wherein the magnet (33) is arranged below the magnetic sensor (34). Position detection device (20) according to one of claims 1 to 7, wherein the magnet (33), the magnetic sensor (34) and the magnetic shielding (40, 40B to 40K) are molded with resin in the housing (23). Position detection device (20) according to one of claims 1 to 8, wherein the magnetic shielding (40, 40B to 40K) is configured to prevent foreign substance adsorption by the magnet (33). Position detection device (20) according to one of claims 1 to 9, wherein the second shielding wall (42b) extends from a first end of the first shielding wall (41), wherein the magnetic shielding (40B) comprises a third shielding wall (42c) extending from a second end of the first shielding wall (41) in the magnetic pole direction, and wherein a third magnetic gap (X3) is formed between the magnet (33) and the third shielding wall (42c).

Images