HALL EFFECT TYPE SENSING DEVICE AND A MAGNETIC CIRCUIT DEVICE FOR A HALL EFFECT TYPE SENSOR

Abstract: A Hall effect type sensor comprises a magnet (45) and a magnetic flux guide (42a, 42b) which cooperate to form a magnetic circuit and a Hall IC (41) disposed in the mag­ netic circuit. These elements are fixed to a frame (40) through holding members (40A, 40B, 43, 44) so that the magnetic flux guide and the Hall IC are placed at correct positions on the frame.

Description: The present invention relates to a Hall effect type sensing device according to the first part of claim 1. There have been known various types of sensing device such as a position sensor, an angle sensor, a speed sensor and so on which utilize Hall effect. Further, a Hall IC formed by integrating and packaging Hall transducing elements used for such sensing device has also been known. Further, there has been known a Hall effect tape sensing device of the type mentioned in the first part of claim 1 for controlling ignition timing in an internal combustion engine in which the Hall IC and a magnetic circuit device are assembled in a casing or a frame and are fixed by a resinous material (US-A-4, 235,-213). In the conventional Hall effect type sensing device having the construction described above, it was necessary to use a jig in order to determine the position of the Hall IC and the magnetic circuit elements to the frame, to inject a thermosetting resin under the condition of fixing them, and to cure the resin in a heating furnace. Accordingly, accuracy in determining the positions of the structural elements was poor. It was therefore not suitable for a large scale production, and it was difficult to obtain accurate signals. In a conventional magnetic circuit device for a Hall effect type sensor in which a magnet is fixed to a magnetic flux guide by an adhesive, it was necessary to use a jig to attach the magnet because the magnetic flux guide had a flat magnet-fitting portion. Even by using the jig, accuracy in determining the position of the magnet was poor, and it was difficult to obtain correct signals in the sensor thus produced. It is the problem underlying the present invention to provide a Hall effect type sensing device and a magnetic circuit device used for a Hall effect type sensor which facilitate to determine correct positions for the structural elements, increase the accuracy of signals and facilitate to use an automated assembling system. In accordance with the present invention, there is provided a Hall effect type sensing device having the features of claim 1. In drawings: Figure 1 is a longitudinal cross-sectional view of a distributor in which an embodiment of the Hall effect type sensing device of the present invention is used; Figur 2a is a front view of an embodiment of the Hall effect type sensing device as shown in Figure 1; Figure 2b is a cross-sectional view taken along a line B-B in Figure 2a; Figure 2c is a side view of the sensing device as in Figure 1; Figure 3 is a perspective view in a diassembled state of the sensing device as in Figures 1 and 2; Figure 4a is a front view of another embodiment of the Hall effect type sensing device of the present invention; Figure 4b is a cross-sectional view taken along a line C-C in Figure 4a; Figure 4c is a side view thereof; Figure 5 is a perspective view of the sensing device as in Figure 4; and Figure 6 is a longitudinal cross-sectional view of another embodiment of a part of the sensing device of the present invention. Preferred embodiments of the Hall effect type sensing device of the present invention will be described. In Figure 1, a reference numeral 1 designates a housing as an element of a distributor, and a numeral 2 designates a shaft which is inserted in the central portion of the housing 1 so as to be freely rotable. The shaft 2 is connected to, for instance, a cam shaft (not shown) in an internal combustion engine through a coupling 21 and is driven in synchronism with the rotation of the engine. A numeral 3 designates a magnetic flux shutter of a magnetic material connected to the shaft 2 so as to be rotatable therewith, a numeral 4 designates a Hall effect type sensing device connected to the housing 1, a numeral 5 designates a rotor for the distributor attached to an end of the shaft 2 so as to be rotatable therewith, and a numeral 6 designates a cap for the distributor. As shown in Figures 2 and 3, the Hall effect type sensing device 4 comprises a frame 40, a holder 44 for supporting a Hall IC 41, a magnetic flux guide 42a and a plate 43 made of a non-magnetic material such as stainless steel, an another magnetic flux guide 42b and a magnet 45 attached to the magnetic flux guide 42b. The holder 44 is formed of a resinous material by molding and has a second holding block 40A in a generally channel-like form in which a pair of grooves 40a are formed in the vertical direction of the opposing inner side surfaces of the channel-like holding block 40A, a first holding block 40B which consists of two rectangular prism-like pieces each having a vertical groove 40b facing to each other, a connecting portion 40c and connecting conductors 40d, which are integrally formed with the frame 40. An end portion of each of the connecting conductors 40d is exposed in the connecting portion 40c to form a conneting pin so that it is electrically connectable to an outer circuit, and the other end portion of them is connected to each lead wire 41a at an exposing portion A by welding as shown in Figure 2b. The holder 44 is also formed by molding a resinous material and has a pair of vertically extending projections 44a to be engaged with the grooves 40a of the frame 40, a first recessed portion 44b for receiving and holding the Hall IC 41, a second recessed portion 44c formed in the first recessed portion 44b so as to extend in the vertical direction so that the magnetic flux guide 42a is received, and four projections 44d extending laterally to support the plate 43. Plate 43 is provided with through holes 43a to be fitted to the four projections 44d of the holder 44. The magnetic flux guide 42b is provided with a pair of vertically extending projections 42ba which are to be fitted to the grooves 40b formed in the first holding block 40B of the frame 40. As shown in Figures 2 and 3, the Hall IC 41, the magnetic flux guide 42a and the plate 43 are fitted to the holder 44, and then, the holder 44 is assembled to the frame 40 by fitting the projections 44a to the grooves 40a. The magnetic flux guide 42b is also fitted to the frame 40 by fitting the projections 42ba to the grooves 40b. Thus, assembling work of the structrual elements of the sensing device can be easy, and the positions of the structural elements for constituting a magnetic circuit and the Hall IC 41 can be correctly determined. Then, a gel-like thermosetting resin is injected into a space S around the Hall IC 41. By curing the thermosetting resin, the positional relationship among the structural elements of the Hall effect type sensing device is fixed. No special jig is required as the conventional sensing device does. Further, an automated assembling system can be easy adopted. Injection of the gel-like thermosetting resin assures the structural elements to be immovable and air-tight properties, hence the Hall IC 41 is protected from moisture and corrosive gas. The plate 43 functions as a dam to prevent the resin from overflowing. A sufficient air gap G is provided between the magnetic flux guides 42a, 42b and between the magnet 45 and the plate 43 so as to pass the magnetic flux shutter 3. In the Hall effect type sensing device having the construction described above, when the shaft 2 is rotated by actuating the engine, the magnetic flux shutter 3 integrally attached to the shaft 2 is also rotated so as to move in the magnetic circuit including the Hall IC 41. The magnetic flux shutter 3 has its circumferential portion formed in a cascade form although omitted in the figures. Accordingly, a change of magnetic flux depending on the revolution speed of the shaft 2 can be given to the Hall IC 41. The Hall IC 41 converts the change of magnetic flux into an electric signal corresponding to the revolution of the internal combustion engine, which is taken through the connecting portion 40c. Thus, by processing the output signal of the Hall IC 41 by a processing circuit (not shown), a crank angle is detected, whereby ignition timing can be controlled. In the above-mentioned embodiment, the positions of the Hall IC 41, the magnetic flux guide 42a and so on to the frame 40 are determined by means of the holder 44. However, these elements may be directly supported by the frame 40 without using the holder 44. The frame 40 may be of a container-like body or may be a container itself. Further, the shape and the number of the holding blocks 40a, 40b, the grooves 40a, 40b and the way of splitting the magnetic flux guides and the position of the magnet are not limited to the above-mentioned embodiment. Description has been made as to a case wherein an angle of crank is detected to control ignition timing for an internal combustion engine. However, another type of sensing device may be used for the present invention. For instance, the magnetic flux shutter 3 may be of a linearly movable type. Thus, in accordance with the present invention, a Hall effect type sensing device capable of facilitating position-determining, generating accurate signals and adopting an automatic system can be obtained. Figures 4 and 5 show another embodiment of the Hall effect type sensing device according to the present invention. In Figures 4 and 5, the same reference numerals designate the same part as in the first embodiment, and therefore, description of these parts is omitted. In Figures 4 and 5, a magnetic circuit device 7 comprises a magnet 71, a first magnetic flux guide 72 and a second magnetic flux guide 73. A recess 73a is formed in the second magnetic flux guide 73 so as to determine the position of the magnet 71, and the magnet 71 is firmly connected to the recess 73a by bonding. The first magnetic flux guide 72 is to be received in the recess 44c formed in the holder 44 which is the same as the first embodiment. The second magnetic flux guide 73 is provided with a pair of extensions 73b which are to be fitted to the grooves 40b of the frame 40 which are the same as the first embodiment. The magnetic circuit device 7 is fitted to the frame 40 by engaging the pair of extensions 73b of the second magnetic flux guide 73 with the pair of grooves 40b of the frame 40 after the magnet 71 has been attached to the recess 73a of the second magnetic flux guide 73 with an adhesive. Further, as shown in Figures 4 and 5, the holder 44 is fitted to the frame 40 by engaging the two extensions 44a with the grooves 40a of the holder after the Hall IC 41, the first magnetic flux guide 72 and the plate 43 have been assembled to the holder 44. Thus, the structural elements of the sensing device can be correctly positioned and firmly supported by the frame 40. Then, lead wires 41a are electrically connected to the connecting conductors 40d by, for instance, spot welding. A thermosetting resin is injected in a space S around the Hall IC 41 so that the Hall IC 41 becomes immovable by curing the resin. Figure 6 is a cross-sectional view of the second magnetic guide 73 and the magnet 71 as another embodiment of the present invention. In this embodiment, the surface area of the bottom wall portion of the recess 73a is made large so that an effective bonding surface to the magnet 71 is increased. And then, an adhesive 8 is applied to the side wall portion 73c as well as the bottom wall portion of the recess 73a. According to this embodiment, position-determining and fixing the magnet 71 become further reliable. It is preferable that the inner surface of the recess 73a has a rough surface in order to strongly bond the magnet 71. Thus, in accordance with the present invention, the magnet 71 can be easily attached to the magnetic flux guide at a correct position. A Hall effect type sensor capable of providing accurate signals can be obtained. Further, an automatic manufacturing system can be easily adopted because the positioning of the structural elements of the sensing device can be easy.

Claims: A Hall effect type sensing device comprising a magnet (45; 71) and a magnetic flux guide (42a, 42b; 72, 73) which cooperate to form a magnetic circuit and a Hall IC (41) disposed in the magnetic circuit, said elements being fixed to a frame (40), characterized in that said frame (40) supports a holder (44) which holds one part (42a; 72) of said magnetic flux guide and said Hall IC (41) in determined positions and to which a plate (43) for covering said hall IC is attached, and in that another part (42b; 73) of said magnetic flux guide is held directly in determined position at said frame (40). The device according to aclaim 1, characterized in that said frame (40) is a resinous material formed by molding and is integrally provided with a first holding block (40B) for holding said other part (42b; 73) of said magnetic flux guide (42a, 42b; 72, 73) and a second holding block (40A) for holding said holder (44) in which said Hall IC (41) and said one part (42a; 72) of said magnet flux guide is supported. The device according to claim 2, characterized in that the other part (42b; 73) of said magnetic flux guide and said holder (44) are respectively held by said first and second holding blocks (40B, 40A) by means of respective projection and groove pairs (40a, 40b). A device according to one of claims 1 to 3, characterized in that said other part (42b; 73) of said magnetic flux guide has a recess (73a) and said magnet (71) is firmly attached by bonding to said recess. The device according to claim 4, characterized in that the surface area of the bottom wall portion of said recess (73a) is made larger so that an effective bonding surface to said magnet (71) is increased.

Inventors: MURATA, SHIGEMI MITSUBISHI DENKI K.K., OHASHI, YUTAKA MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1989
Main classification: G01D5
IPC codes: G01D5