Rotation detector

Abstract: To provide a rotation detector facilitating integrating operation performance and preventing occurrence of detection noise. A housing 1 is provided with an inserting portion la into which a wheel shaft is inserted and is mounted to the wheel shaft. The magnet 6 is rotated in synchronism with a wheel mounted to the wheel shaft and the inserting portion la is inserted thereinto. A magnetic conversion element 3 detects a change in magnetic poles of the magnet 6. The housing 1 is comprising a first accommodating portion 1b formed at the periphery of the inserting portion la for accommodating the magnet 6 and a second accommodating portion ld for arranging the magnetic conversion element 3 at the proximity of the magnet 6.

Description: The present invention relates to a rotation detector of an electric type for transmitting a rotation number of two- cycle wheels of, for example, a motorcycle, a bicycle or the like to a speedometer or the like. Prior art wheel speed sensing devices are known from US-A-3915266, EP-A-0190879 and FR-A-2669728. A conventional rotation detector has been disclosed in Japanese Unexamined Patent Publication No. JP-2-264817. When such a rotation detector is used as a rotation detector for a two-cycle vehicle (for example, motorcycle), a magnetic conversion element (Hall IC) mounted to a circuit board and a magnet are arranged in a resin case in a substantially cylindrical shape having a detecting face for detecting an object for detection along the detecting face, and the circuit board, the magnetic conversion element and the magnet are sealed by a sealing member comprising epoxy etc. thereby constituting a rotation detector. Further, it is general to install the rotation detector to a transmission case or a sprocket cover for detecting a blade edge etc. of a transmission gear or a sprocket rotating at the inside thereof as the object for detection. When a tooth etc. of a transmission gear or a sprocket is detected as the object for detection by using such a rotation detector, more or less clearance is present at the object for detection and therefore, a vibration is caused in the object for detection depending on the rigidity of the body of a vehicle (two-cycle vehicle) or an amount of exhaust etc. whereby a gap between the object for detection and a detecting position of the rotation detector is varied, causing a change in magnetism in the rotation detector and the change produces a noise in detection, which gives rise to cause erroneous operation of, for example, an indicating instrument displaying the speed in accordance with output data outputted from the rotation detector. Further, the shape and the size of the object for detection are varied according to the kind of vehicle and therefore, it is necessary to adjust the gap for detection between the object for detection and the rotation detector, which complicates the integrating operation performance. Hence, the present invention provides a rotation detector facilitating the integrating operation performance and preventing the detection noise from occurring by paying attention to the above-described problems. In order to solve the above-described problems, the present invention provides a rotation detector comprising a housing, a magnet and a magnetic conversion element, characterized in that the housing has an inserting portion for inserting a wheel shaft and mounted to the wheel shaft, the inserting portion being inserted into the magnet such that the magnet is rotated in synchronism with a wheel mounted to the wheel shaft and the magnetic conversion element is arranged at a portion of the housing in proximity to the magnet. In a particular embodiment, said magnet includes a plurality of rotation support pieces for rotating in synchronism with a wheel mounted to the wheel shaft, and a cylindrical portion into which said inserting portion is inserted, said cylindrical portion being magnetized; and said magnetic conversion element is mounted to a circuit board for detecting a change in magnetic poles of the cylindrical portion; said housing includes a first accommodating portion formed at a periphery of the inserting portion for accommodating said magnet, and a second accommodating portion for said magnetic conversion element; and said circuit board is located along a guide portion formed in said second accommodating portion. Also, a magnetic detecting face, corresponding to a detecting face of the magnetic conversion element arranged at the second accommodating portion, may be formed on an inner wall of the first accommodating portion. Further, a holding piece projected in a direction of the wheel and a flange portion extended outwardly from the holding piece may be formed at the periphery of the first accommodating portion of the housing, and an elastic member arranged on the flange portion along the holding piece may be provided. Additionally, a groove portion may be formed at a side end face of the elastic member. The rotation detector of the present invention is provided with a housing having a cylindrical inserting portion for inserting a wheel shaft, which is mounted to the wheel shaft, a magnet having rotation support pieces for rotating in synchronism with a wheel mounted to the wheel shaft and a cylindrical portion into which the inserting portion is inserted and which is magnetized to the cylindrical portion and a magnetic conversion element for detecting a change in magnetic poles magnetized to the cylindrical portion, wherein a first accommodating portion formed at the periphery of the inserting portion for accommodating the magnet and a second accommodating portion for arranging the magnetic conversion element in the proximity of the magnet, are formed at the housing and a circuit board for mounting the magnetic conversion element is accommodated in the second accommodating portion whereby the magnetic conversion element is arranged in the proximity of the magnet. For example, when the rotation detector is directly installed to the wheel shaft of, for example, a motorcycle etc., the magnet is rotated in synchronism with the rotation of the wheel and the change in the magnetic poles of the magnet can be detected by the magnetic conversion element. Therefore, accurate rotation detection is provided since it does not receive influence of detection noise caused by vibration of an object for the detection as in the conventional case. Further, the magnetism detecting face corresponding to the detecting face of the magnetic conversion element that is arranged to the second accommodating portion via the circuit board, is formed on the inner wall of the first accommodating portion by which the detection distance between the detecting face of the magnetic conversion element and the magnet can preferably be secured, therefore, accurate rotation detection is provided. Also, a troublesome adjusting step for adjusting the detection distance between the object for detection and the detecting face of the rotation detector as in the conventional case is dispensed with whereby the integrating operation performance of the rotation detector can be promoted. Further, the holding piece projected in the direction of the wheel at the periphery of the first accommodating portion of the housing and the flange portion extended outwardly from the holding piece, are formed. The elastic member at the side end face of which a groove portion for coating a lubricant such as grease is formed, is press-fitted to the holding piece whereby it is arranged at the flange portion. Thereby, at a portion where a hub of the wheel and the rotation support pieces of the magnet are brought into contact with each other, vibration of the wheel caused in running a vehicle is attenuated by the elastic member, the burden on the rotation support pieces is alleviated and the rotation of the wheel is preferably secured. Moreover, water, mud, dust or the like can be prevented from invading a portion the hub of the wheel where the rotation detector is attached. An explanation will be given of the present invention based on embodiments in reference to the attached drawings, by taking an example of detecting the rotation number of the wheel of, for example, a motorcycle, as follows. Fig. 1 is an exploded perspective view of a rotation detector of the present invention, Fig. 2 is a sectional view of essential portions of the rotation detector of the present invention; and Fig. 3 is a view showing a state of attaching the rotation detector of the present invention. Referring to Fig. 1 and Fig. 2, a rotation detector A is constituted by a housing 1 made of a resin material, a circuit board 2 provided with a predetermined wiring pattern, not illustrated, a magnetic conversion element 3 comprising Hall ICs or the like, an elastic member 4 made of a rubber material, a spacer 5 made of a resin material, a magnet 6 and wiring cords 7 electrically connected to the magnetic conversion element 3 via the circuit board 2. The housing 1 is made of a resin material such as polybutylene terephthelate, nylon or the like. A cylindrical inserting portion 1a made of a metal material into which a wheel shaft, mentioned later, is inserted, is formed by inserting it into a substantially central portion of the housing 1. A first accommodating portion 1b in a cylindrical shape for rotatably arranging a magnet 6, mentioned later in details, at the outer periphery of the inserting portion 1a, is formed at the periphery of the inserting portion 1a. A second accommodating portion 1d for accommodating the magnetic conversion element 3 mounted to the circuit board 2 and having a guide groove (guiding portion) for guiding and supporting the circuit board 2, is formed outside of other end of the first accommodating portion 1b. Further, a holding piece 1e projecting in a direction of a front wheel, mentioned later, and a flange portion 1f extended outwardly from the holding piece 1e for arranging the elastic member 4, mentioned later in details, are formed at the periphery of the first accommodating portion 1b. Also, a magnetism detecting face 1g corresponding to a detecting face 3a of the magnetic conversion element 3 arranged to the second accommodating portion 1d via the circuit board 2, mentioned later in details, is formed on the inner wall of the above-described first accommodating portion 1b. According to the circuit board 2, a predetermined wiring pattern is formed on a substrate made of an insulating material such as paper phenol, glass epoxy or the like and the magnetic conversion element 3 and electronic parts, not illustrated, comprising condensers and the like are electrically fixed thereto by solder or the like. Further, according to the circuit board 2, the wiring cords 7 for supplying the magnetic conversion element 3 with power supply and transmitting an output signal from the magnetic conversion element 3 to an indicating instrument (for example, speedometer), not illustrated, are electrically connected to predetermined portions of the circuit board 2 by soldering. The circuit board 2 is arranged at the second accommodating portion 1d along the guide groove 1c such that the detecting face 3a of the magnetic conversion element 3 is brought into contact with the inner side face of the magnetic detecting face 1g that is formed at the first accommodating portion 1b of the housing 1, arranged in the second accommodating portion 1d along the guide groove 1c and thereafter, fixed to the second accommodating portion 1d by filling thereto a sealing member 8 made of epoxy or the like. The elastic member 4 is made of a rubber material of a nitril or silicone type material etc. The elastic member 4 is constituted by a thin cylindrical shape where a groove portion 4a having a sectional shape of a substantially V-like form at the side end face thereof, and an erected portion 4b extended upwardly from the groove portion 4a, are formed. Further, a holding member 4c made of a metal material having the sectional shape of a substantially L-like form, is formed by inserting it into the inside of the erected portion 4b and the inner periphery of the erected portion 4b is formed smaller than the outer periphery of the holding piece 1e of the housing 1 and therefore, the erected portion 4b and the flange portion 1f of the housing 1 are arranged to be brought into contact with each other by press-fitting it to the holding piece 1e. The spacer 5 is provided with a flat plane shape having an insertion hole 5a for inserting the inserting portion 1a of the housing 1, and is made of a resin material such as polyacetal, nylon or the like. The spacer 5 is arranged between an inner bottom portion 1h of the first accommodating portion 1b of the housing 1 and the magnet 6 for preventing wear of the respective members. The magnet 6 is comprising, for example, a plastic magnet or the like, in which a cylindrical portion 6a for inserting the inserting portion 1a of the housing 1 is formed and a plurality of rotation support pieces 6b extended outwardly from the periphery of the cylindrical portion 6a for rotating the cylindrical portion 6a in synchronism with the front wheel, are formed on the side of a contact face of the cylindrical portion 6a for getting in contact with a hub of the front wheel, mentioned later. The above-described plurality of rotation support pieces 6b are formed to fit to a stopper portion formed at the hub of the front wheel and with regard to the cylindrical portion 6a, 8 poles are magnetized on the surface of the cylindrical portion 6a. According to the rotation detector A constituted by the above-described respective portions, the elastic member 4 is press-fitted to the holding piece 1e of the housing 1, the erected portion 4b of the elastic member 4 is arranged to get in contact with the flange portion 1f, the spacer 5 is arranged at the inner bottom portion 1f of the first accommodating portion 1b of the housing 1 and thereafter, the magnet 6 is arranged in the first accommodating portion 1b such that the inserting portion 1a of the housing 1 is inserted into the cylindrical portion 6a of the magnet 6 (A lubricant such as grease etc. is coated between the outer periphery of the inserting portion 1a and the inner face of the cylindrical portion 6a of the magnet 6, and between the cylindrical portion 6a of the magnet 6 and the spacer 5). Further, the circuit board 2 to which the magnetic conversion element 3 and electronic parts and the like, not illustrated, are mounted and the wiring cords 7 are electrically connected, is arranged to the second accommodating portion 1d of the housing 1 along the guide groove 1c of the housing 1 such that the detecting face 3a of the magnetic conversion element 3 is brought into contact with the inner face of the magnetism detecting face 1g formed on the inner face of the first accommodating portion 1b of the housing 1. The sealing member 8 such as epoxy or the like is filled in the second accommodating portion 1d in a state where, for example, a predetermined pressure is applied on the end face of the circuit board 2 on the side of connecting the wiring cords 7 such that the circuit board 2 does not float up, and is cured whereby the rotation detector A is completed. Next, an explanation will be given of a case where the rotation detector A having such a constitution is attached to a front wheel of a motor cycle in reference to Fig. 3. Numeral 9 designates a front fork supporting a front wheel of a motor cycle, numeral 10 designates a front wheel (wheel) and numeral 11 designates a wheel shaft rotatably supporting the front wheel 10. After coating a lubricant such as grease etc. to the groove portion 4a, the wheel shaft 11 inserted into a through hole 10b formed at the center of a hub 10a of the front wheel 10, is inserted into the inserting portion 1a of the housing 1, the rotation support pieces 6b formed in the magnet 6 are fitted into a stopper portion 10c formed in the hub 10a and the side face of the elastic member 4 forming the groove portion 4a is arranged to get in contact with the inner periphery of a cylindrical erected portion 10d formed in the hub 10a by which the rotation detector A is mounted between the front fork 9 and the front wheel 10. According to the rotation detector A having such a constitution, the magnet 6 is rotated in synchronism with the rotation of the front wheel 10, a change in the magnetic poles magnetized on the cylindrical portion 6a of the magnet 6, is detected by the magnetic conversion element 3 arranged at the magnetism detecting face 1g formed in the housing 1 and the detected signal is transmitted to an outside indicating instrument, not illustrated, via the wiring cords 7, whereby accurate detection of rotation can be provided since the detector does not receive influence of detection noise due to the vibration of an object for detection (tooth of a transmission gear, sprocket gear or the like) as in the conventional case. The magnetism detecting face 1g is formed on the inner wall of the first accommodating portion 1b in correspondence with the detecting face 3a of the magnetic conversion element 3 arranged in the second accommodating portion 1d of the housing 1 via the circuit board 2, by which the detection distance between the detecting face 3a of the magnetic conversion element 3 and the cylindrical portion 6a of the magnet 6 can preferably be secured and a troublesome adjusting step of adjusting the detection distance between the object for detection and the detecting face of the rotation detector in the conventional case is dispensed with whereby the integrating operation performance of the rotation detector A can be improved. Also, the holding piece 1e protruded in the direction of the wheel 10 and the flange portion 1f extended outwardly from the holding piece 1e, are formed at the periphery of the first accommodating portion 1b of the housing 1 and the elastic member 4 at the side end face of which the groove portion coated with a lubricant such as grease etc. is formed, is arranged at the flange portion 1f by press-fitting it to the holding piece 1e by which at a portion where the hub 10a of the wheel 10 and the rotation support pieces 6b of the magnet 6 are brought into contact with each other, the vibration from the wheel caused in running the vehicle is attenuated, the burden on the rotation support pieces 6b in contact with the hub 10a is attenuated and the rotation of the wheel 10 is preferably secured and invasion of water, mud, dust and the like to the portion of the hub 10a for attaching the rotation detector A can be prevented. Incidentally, although the magnet 6 according to the embodiment is integrally formed with the magnetized cylindrical portion 6a and the rotation supporting pieces 6b by using a plastic magnet material, the present invention is not limited to the embodiment and, for example, the cylindrical portion and the rotation supporting pieces may separately be formed and the respective portions may be assembled so far as the magnet body is rotated in synchronism with the rotation of the wheel in respect of the inserting portion provided in the housing. Although the magnetism detecting face 1g is formed at the first accommodating portion 1b of the housing 1, the magnetism detecting face 1g may not be necessarily provided in the rotation detector of the present invention so far as the detection distance between the magnet 6 and the magnetic conversion element 3 is preferably secured. For example, the magnetism detecting face 1g can be dispensed with by molding the magnetic conversion element in the housing by insertion forming and maintaining preferably the detection distance between the magnetic body and the magnetic conversion element. Further, although according to the embodiment, the guide groove 1c is formed at the second accommodating portion 1d of the housing 1 and the guide portion is constituted to guide and support the circuit board 2, the guide portion may be constituted by, for example, two of guides supporting the end faces of the circuit board 2. According to the present invention, the housing having the inserting portion for inserting the wheel shaft and mounted to the wheel shaft, the magnet to which the inserting portion is inserted such that the magnet is rotated in synchronism with the wheel mounted to the wheel shaft and the magnetic conversion element for detecting the change in the magnetic poles of the magnet, are provided, the first accommodating portion formed at the periphery of the inserting portion for accommodating the magnet and the second accommodating portion for arranging the magnetic conversion element at the proximity of the magnet, are formed in the housing. Especially, the housing having the cylindrical inserting portion into which the wheel shaft is inserted and mounted to the wheel shaft, the magnet having the rotation support pieces for rotating in synchronism with the wheel mounted to the wheel shaft and the cylindrical portion into which the inserting portion is inserted, which is magnetized to the cylindrical portion and the magnetic conversion element mounted to the circuit board for detecting the change in the magnetic poles magnetized at the cylindrical portion, are provided, the first accommodating portion formed at the periphery of the inserting portion for accommodating the magnet and the second accommodating portion for arranging the magnetic conversion element, are formed in the housing and the circuit board is arranged along the guide portion formed in the second accommodating portion whereby the magnetic conversion element is arranged at the proximity of the magnet. The magnet is rotated in synchronism with the rotation of the wheel and the change in the magnetic poles magnetized at the cylindrical portion of the magnet can be detected by the magnetic conversion element whereby accurate detection of rotation can be provided since the detector does not receive influence of detection noise due to the vibration of an object for detection (tooth of a transmission gear, sprocket gear etc.) as in the conventional case. Further, the magnetism detecting face corresponding to the detecting face of the magnetic conversion element arranged in the second accommodating portion, is formed on the inner wall of the first accommodating portion and the detection distance between the detecting face of the magnetic conversion element and the magnet can preferably be secured whereby accurate detection of rotation can be provided and the integrating operation performance of the rotation detector can be improved since the troublesome adjusting step of adjusting the detection distance between an object for detection and the detecting face of the rotation detector in the conventional case is dispensed with. Further, the holding piece projected in the direction of the wheel and the flange portion extended outwardly from the holding piece are formed at the periphery of the first accommodating portion of the housing and the elastic member arranged on the flange portion along the holding piece, is provided and the groove portion is formed at the side end face of the elastic member by which at the portion where the hub of the wheel and the rotation supporting pieces of the magnet are brought into contact with each other, the vibration from the wheel caused in running the vehicle is attenuated by the elastic member, the burden on the rotation supporting pieces is attenuated and the rotation of the wheel is preferably secured and invasion of water, mud, dust and the like to the portion of the hub of the wheel for attaching the rotation detector can be prevented.

Claims: A rotation detector (A) comprising a housing (1), a magnet (6) and a magnetic conversion element (3), characterized in that the housing (1) has an inserting portion (1a) for inserting a wheel shaft (11) and mounted to the wheel shaft (11), the inserting portion (1a) being inserted into the magnet (6) such that the magnet (6) is rotated in synchronism with a wheel (10) mounted to the wheel shaft (11) and the magnetic conversion element (3) is arranged at a portion of the housing (11) in proximity to the magnet (6). A rotation detector according to claim 1, wherein: said magnet (6) includes a plurality of rotation support pieces (6b) for rotating in synchronism with a wheel (10) mounted to the wheel shaft (11), and a cylindrical portion (6a) into which said inserting portion (1a) is inserted, said cylindrical portion (6a) being magnetized; and said magnetic conversion element (3) is mounted to a circuit board (2) for detecting a change in magnetic poles of the cylindrical portion (6a); said housing includes a first accommodating portion (1b) formed at a periphery of the inserting portion (1a) for accommodating said magnet (6), and a second accommodating portion (1d) for said magnetic conversion element (3); and said circuit board (2) is located along a guide portion (1c) formed in said second accommodating portion (1d). A rotation detector according to claim 2, wherein a magnetism detecting face (1g) corresponding to a detecting face (3a) of the magnetic conversion element (3) accommodated in the second accommodating portion (1d) is formed on an inner wall of the first accommodating portion (1b). A rotation detector according to claim 2 or claim 3 further comprising: a holding piece (1e) projected in a direction of the wheel (10) and a flange portion (1f) extended outwardly from the holding piece (1e) are formed at a periphery of the first accommodating portion (1b) of the housing (1) and an elastic member (4) arranged on the flange portion (1f) is provided along the holding piece (1e). A rotation detector according to claim 4, wherein a groove portion (4a) is formed at a side end face of the elastic member (4).

Inventors: OGURO YUJI, OGURO, YUJI
Applicants: NIPPON SEIKI CO LTD, NIPPON SEIKI CO., LTD.
Application year: 1997
Main classification: G01P1
IPC codes: G01P1, G01D11, G01P3, G01D5