Motor drive switch |
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申请号 | EP11177198.6 | 申请日 | 2011-08-11 | 公开(公告)号 | EP2423932A1 | 公开(公告)日 | 2012-02-29 |
申请人 | Makita Corporation; | 发明人 | Maegawa, Masahiro; Nishikimi, Junichi; | ||||
摘要 | A motor drive switch (20) is disclosed which prevents a motor stator winding (11) from being damaged even when contact sticking occurs. In the motor drive switch (20), configuration is made with respect to a start operation of the motor such that the switching of a first contact (21) to a power source P-side terminal (3) is effected earlier than the switching of a second contact (22) to an armature P-side terminal (6), and respect to a stop operation of the motor configuration is made such that the switching of the second contact (22) to an armature N-side terminal (4) is effected earlier than the switching of the first contact (22) to an armature P-side terminal (1). | ||||||
权利要求 | |||||||
说明书全文 | This application claims priority to Japanese patent application serial number The present invention relates to a motor drive switch that can be used in a motor control circuit. Japanese Laid-Open Patent Publication No. As shown in The first contact 101 of the motor drive switch 100 is connected to one end (12) of a motor stator winding 112, and can be switched between a power source P-side terminal (3) connected to the P side of a power source E and an armature P-side terminal (1) connected to the P side of an armature 104. The second contact 102 is connected to the other end (5) of the motor stator winding 112, and can be switched between an armature P-side terminal (6) and an armature N-side terminal (4) connected to the N side of an armature 104. And, as shown in As shown in Between the armature N-side terminal (4) of the second contact 102 and the N terminal of the armature 114, there is provided a resistor 116 for restricting a brake current. In the above motor drive switch 100, the first contact 101 and the second contact 102 are switched substantially simultaneously. Thus, in a case where contact sticking occurs at the first contact 101 and the second contact 102 due to aging or the like, it is impossible to determine at which of the positions (1), (3), (4), and (6) such contact sticking occurs. For example, as shown in Thus, there is a need in the art to prevent the stator winding of a motor from being damaged even when contact sticking of a motor drive switch occurs. One construction for a motor drive switch includes a first contact which is connected to one end of a stator winding of a motor and which can be switched between a power source P-side terminal connected to a P side of a power source and an armature P-side terminal connected to a P side of an armature. The motor drive switch further includes a second contact which is connected to the other end of the stator winding and which can be switched between the armature P-side terminal and an armature N-side terminal connected to an N side of the armature. The motor drive switch used in a motor control circuit is configured such that the first contact is switched to the power source P-side terminal, and that the second contact is switched to the armature P-side terminal by a start operation of the motor, whereby the stator winding and the armature are connected in series between the P side and the N side of the power source thereby to start the motor. The motor drive switch is further configured such that by a stop operation of the motor, the first contact is switched to the armature P-side terminal and the second contact is switched to the armature N-side terminal, with the result that the stator winding and the armature form a closed loop to brake the motor. In the start operation of the motor, the switching of the first contact to the power source P-side terminal is configured to be effected earlier than the switching of the second contact to the armature P-side terminal, and in the stop operation of the motor, the switching of the second contact to the armature N-side terminal is configured to be effected earlier than the switching of the first contact to the armature P-side terminal. According to this construction, in the start operation of the motor, the switching of the first contact to the power source P-side terminal is configured to be effected earlier than the switching of the second contact to the armature P-side terminal. Thus, an electric current flows through the stator winding and the armature of the motor at the time when the second contact is switched to the armature P-side terminal. Thus, if contact sticking is to be occurred with the passage of time, it occurs between the second contact and the armature P-side terminal. If contact sticking occurs at the armature P-side terminal of the second terminal and then the stop operation is performed on the motor drive switch and the first contact is switched to the armature P-side terminal, no electric current flows through the stator winding of the motor. That is, no abnormal current flows through the stator winding of the motor due to contact sticking. Further, in the stop operation of the motor, configuration is made such that the switching of the second contact to the armature N-side terminal is effected earlier than the switching of the first contact to the armature P-side terminal. Thus, an electric current flows through the stator winding and the armature of the motor at the time when the first contact is switched to the armature P-side terminal. Thus, if contact sticking is to be occurred with the passage of time occurs, it occurs between the first contact and the armature P-side terminal. If contact sticking occurs at the armature P-side terminal of the first contact and then start operation is performed on the motor drive switch and the second contact is switched to the armature P-side terminal, the motor does not start and no electric current flows through the stator winding of the motor. That is, no abnormal current flows through the stator winding of the motor due to contact sticking. According to another construction, there is provided a trigger that can perform the start operation of the motor by sliding of the trigger from a stop position to a start position and perform the stop operation of the motor by returning of the trigger from the start position to the stop position. The trigger has a first protrusion and a second protrusion that can respectively press the first contact and the second contact during the sliding, and each of the first contact and the second contact is formed in a scale-like arcuate configuration whose center is supported by a fulcrum. Further, each of the first contact and the second contact tilts around the fulcrum when each contact is pressed by the first protrusion and the second protrusion respectively, thereby effecting switching of the contacts. And the first protrusion and the second protrusion are arranged so as to be offset in the sliding direction, whereby there is a difference in switching time between the first contact and the second contact. According to another construction, there is provided a trigger that can perform the start operation of the motor by sliding of the trigger from a stop position to a start position and perform the stop operation of the trigger by returning of the trigger from the start position to the stop position. The trigger has a first protrusion and a second protrusion that respectively presses the first contact and the second contact during the sliding, and each of the first contact and the second contact is formed in a scale-like arcuate configuration whose center is supported by a fulcrum. Further, each of the first contact and the second contact tilts around the fulcrum when each contact is pressed by the first protrusion or the second protrusion, thereby effecting switching of the contacts. And bending positions of the first contact and the second contact are offset in the sliding direction, whereby there is a difference in switching time between the first contact and the second contact. According to another construction, there is provided a trigger that can perform the start operation of the trigger by sliding of the trigger from a stop position to a start position and perform the stop operation of the trigger by returning of the trigger from the start position to the stop position. Each of the first contact and the second contact is accommodated in a case respectively, and operating pins protruding from the case are pressed or depressed to effect switching of the contacts. The trigger has a first pressing surface and a second pressing surface which are configured to press an operating pin for the first contact and an operating pin for the second contact respectively and which are formed to be offset from each other in the sliding direction. According to the above, even if contact sticking occurs in the motor drive switch, no abnormal current flows through the stator winding of the motor. Thus, there is no possibility of the stator winding being damaged, which reduces the burdens of servicing. Additional objects, features, and advantages, of the present invention will be readily understood after reading the following detailed description together with the claims and the accompanying drawings, in which:
Each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings to provide improved motor drive switch. Representative examples of the present teaching, which examples utilize many of these additional features and teachings both separately and in conjunction with one another, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Moreover, various features of the representative examples and the dependent claims may be combined in ways that are not specifically enumerated in order to provide additional useful examples of the present teachings. In the following, a motor drive switch of the present invention will be described with reference to First, a summary of a motor drive switch 20 will be described with reference to The motor drive switch 20 is a double-pole double-throw switch used in a control circuit 10 of a series-wound motor (hereinafter referred to as the motor) in which a stator winding and an armature winding are connected in series. The motor drive switch 20 is mounted on an electric tool main body (not shown). By performing pull operation of a trigger 30 (refer to As shown in Due to the above construction, as shown in As shown in As described above, when pull operation is performed on the trigger 30, the first contact 21 is first switched, and then the second contact 22 is switched as shown in Further, when returning operation is performed on the trigger 30 in this state, the first contact 21 is switched to the armature P-side terminal (1) as shown in When returning operation is performed on the trigger 30 with the motor drive switch 20 being in the normal state, the second contact 22 is first switched, and then the first contact 21 is switched as shown in Next, when pull operation is performed on the trigger 30, the second contact 22 is switched to the armature P-side terminal (6) as shown in As shown in Further, as shown in The terminal (1) of the first contact 21 corresponds to the armature P-side terminal (1), the terminal (2) thereof corresponds to one end side terminal (2) of the stator winding 11, and the terminal (3) thereof corresponds to the power source P-side terminal (3). The terminal (4) of the second contact 22 corresponds to the armature N-side terminal (4), the terminal (5) thereof corresponds to the other end side terminal (5) of the stator winding 11, and the terminal (6) thereof corresponds to the armature P-side terminal (6). As shown in When the first contact 21 is tilted around the fixed end 21c at the center (the terminal (2)) so as to be lower on the rear side, the rear side movable end 21h is connected to the terminal (3), and the front side movable end 21f is kept away from the terminal (1) as shown in Similarly, the second contact 22 includes a strip-like metal plate curved into a substantially arcuate configuration so as to be convex on the lower side, with its fixed end 22c at the center being supported from below by the terminal (5) in the form of a scale. Further, operation is performed in a manner similar to that in the case of the first contact 21, enabling movable ends 22f and 22h provided at the front and rear ends of the second contact 22 to be respectively connected to the terminal (4) and the terminal (5). In the operating portion 32 of the trigger 30 there are embedded a first protrusion 36 pressing the upper surface of the first contact 21 and a second protrusion 37 pressing the upper surface of the second contact 22. The first protrusion 36 and the second protrusion 37 are pin-like members with the same length, with their distal ends being beveled into a hemispherical configuration. Further, the first protrusion 36 and the second protrusion 37 are respectively accommodated in vertical holes formed in the lower surface of the operating portion 32 of the trigger 30, with their distal end portions protruding therefrom. As shown in As shown in When returning operation is performed on the trigger 30 and the first protrusion 36 and the second protrusion 37 slide in the forward direction on the upper surfaces of the first contact 21 and the second contact 22 respectively, the second protrusion 37 which is situated on the front side of the first protrusion 36 in the sliding direction first connects the second contact 22 to the terminal (4), and then the first protrusion 36 connects the first contact 21 to the terminal (1). That is, transferring from the state shown in In the motor drive switch 20 of this example, configuration is made with respect to the motor start operation such that, the first contact 21 is switched to the power source P-side terminal (3) earlier than the switching of the second contact 22 to the armature P-side terminal (6), as shown in As shown in As shown in As shown in Thus, the stator winding of the motor may not be damaged, which can reduce the burden of servicing. The above construction may not be limited by the above-described example and may various changes may be made without departing from the scope of invention. For example, the above example shows that the mounting positions of the first protrusion 36 and the second protrusion 37 are arranged to be offset from each other in the sliding direction of the trigger 30 (a longitudinal direction) by the distance X, so that there is a time lag in operational timing between the first contact 21 and the second contact 22. However, it is also possible to provide a time lag in operational timing between the first contact 21 and the second contact 22 by mounting the first protrusion 36 and the second protrusion 37 at the same position in the sliding direction (See That is, it is also possible to adopt a construction in which when sliding the trigger 30 in the backward direction, the first contact 21 is turned ON at a position on the front side of the second contact by the distance X as shown in Further, as shown in More specifically, the first switch 210 is provided with a case 21c including the first contact 22 and the terminals (1), (2), and (3), with an operating pin 21p being attached to the case 21c so as to be capable of being displaced in the vertical direction. Further, the operating pin 21p can be slid down against a spring force, whereby the first contact 21 tilts to the left, with a movable end of the first contact 21 being connected to the terminal (3) as shown in the lower portion of The second switch 220 is of the same structure as the first switch 210. As shown in the upper portion of There are formed on the operating portion 32 of the trigger 30 a first pressing surface 32a and a second pressing surface 32b capable of pressing the operating pin 21p of the first switch 210 and the operating pin 22p of the second switch 220 respectively, in the course of sliding. The first pressing surface 32a and the second pressing surface 32b are inclined to the same degree, and the first pressing surface 32a is arranged to be offset with respect to the second pressing surface 32b by the distance X in the sliding direction, as shown in By the returning operation of the trigger 30, the second pressing surface 32b is caused to keep away from the operating pin 22p of the second switch 220 firstly, and the second contact 22 is connected to the terminal (4). Then, the first pressing surface 32a is caused to keep away from the operating pin 21p of the first switch 210, and the first contact 21 is connected to the terminal (1). As described above, the motor drive switch of the present invention can be used in a motor control circuit. Especially, it can also be used in electric power tools such as miter saws, grinders, and electric screwdrivers etc. It is explicitly stated that all features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure as well as for the purpose of restricting the claimed invention independent of the composition of the features in the embodiments and/or the claims. It is explicitly stated that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure as well as for the purpose of restricting the claimed invention, in particular as limits of value ranges. |