Starter including noise reduction filter

The starter includes a noise reduction filter having at least one capacitor, a positive side lead plate connected to a first end of the capacitor and a negative side lead plate connected to a second end of the capacitor, the positive side lead plate being connected to a motor lead wire of a motor through a connection fitting, the negative side lead plate being fixed and ground-connected to a frame of the motor. The connection fitting includes a connection arm connected to the positive side lead plate and a cylindrical joint section integrally formed with the connection arm, the joint section being fitted in a root section of the motor lead wire drawn outside the frame through a grommet attached to the frame to be electrically connected to the motor lead wire.

This application claims priority to Japanese Patent Application No. 2011-219934 filed on Oct. 4, 2011, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a starter including a noise reduction filter for reducing noise emitted from a motor of the starter.

2. Description of Related Art

There is an increasing number of vehicles provided with a system for automatically stopping the engine by cutting supply of fuel to the engine when the vehicle is stopped at an intersection for example (the system being generally called “idling stop system”) in order to reduce carbon dioxide emission and improve fuel economy of the vehicle. When a vehicle driver of such a vehicle performs an operation to start the vehicle after the engine was stopped by the idling stop system, the starter of the vehicle starts to operate to automatically start the engine in accordance with a command received from an ECU (Electronic Control Unit). Meanwhile, if the starter is of the type including a commutator motor, since sparks occur between the commutator and brushes when the motor is rotating, it may occur that the vehicle driver and passengers feel uncomfortable each time the engine is automatically restarted because such sparks cause noise in a radio receiver or the like.

German patent application laid-open No. 102008001570 describes a structure where a noise reduction filter including a capacitor circuit is connected in parallel with a motor of a starter to cope with this problem.

However, in this structure, a motor lead wire is welded to a metal terminal connected to the brush of the motor and drawn outside the starter, and the noise reduction filter is electrically and mechanically connected to this metal terminal. For starters whose metal terminal is not drawn outside, it is not possible to carry out the step to connect the noise reduction filter to the metal terminal in the starter assembly line.

SUMMARY

An exemplary embodiment provides a starter including:an electromagnetic switch including an electrical contact interposed in a power supply line through a battery terminal and a motor terminal thereof, and configured to open and close the electrical contact in interlock with on/off operation of a solenoid thereof;a motor for generating torque by being supplied with electric power from a battery through a motor lead wire connected to the motor terminal when the electrical contact is closed; anda noise reduction filter connected to the power supply line in parallel with the motor for suppressing noise emitted from the motor;whereinthe motor lead wire is connected to a brush or a field winding of the motor at a first end thereof drawn inside a frame of the motor through a grommet attached to the frame, and connected to the motor terminal at a second end thereof drawn outside the frame through the grommet,the noise reduction filter includes at least one capacitor, a positive side lead plate connected to a first end of the capacitor and a negative side lead plate connected to a second end of the capacitor, the positive side lead plate being connected to the motor lead wire through a connection fitting, the negative side lead plate being fixed and ground-connected to the frame, andthe connection fitting includes a connection arm connected to the positive side lead plate and a cylindrical joint section integrally formed with the connection arm, the joint section being fitted in a root section of the motor lead wire drawn outside the frame of the motor through the grommet to be electrically connected to the motor lead wire.

According to the exemplary embodiment, there is provided a starter having the structure enabling retrofitting a noise reduction filter to the frame of a motor of the starter even if the starter is not provided with such a metal terminal connected to a brush of the motor and drawn outside the frame.

Other advantages and features of the invention will become apparent from the following description including the drawings and claims.

PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1is a rear view of a starter1including a noise reduction filter as viewed from the side of the rear end of the starter (from the side of the end frame of the starter) according to an embodiment of the invention. As shown inFIG. 3, the starter1includes a motor3, an output shaft4, a clutch5, a pinion6, a shift lever7, an electromagnetic switch8and a noise reduction filter9. The motor3generates torque when supplied with power from a battery2(seeFIG. 4). The output shaft4is driven by the motor3. The rotation of the output shaft4is transmitted to the pinion6through the clutch5. The electromagnetic switch8drives the shift lever7using the attraction force of an electromagnet thereof to push out the pinion6integrally with the clutch6in the opposite motor direction (in the leftward direction inFIG. 3), and interrupts a current supplied to the motor3by opening and closing a later-explained main contact. The noise reduction filter9is for suppressing noise emitted from the motor3.

The motor3is a DC commutator motor including a field system constituted of permanent magnets or a field winding disposed inside a yoke10which forms a magnetic circuit, an armature3a(seeFIG. 4) rotatably disposed inside the field system and brushes11(seeFIG. 4) which slide on the outer periphery of a commutator when the armature3arotates. The output shaft4is disposed coaxially with the armature3aby the provision of a not-shown reduction gear (a planetary reduction gear, for example). The torque generated by the motor3and increased by the reduction gear is transmitted to the output shaft4causing the output shaft4to rotate. The clutch5is a one-way clutch which transmits the torque of the output shaft4from the outer5athereof to the inner tube5bthereof, while interrupting torque transmission from the inner tube5bto the outer5a. The pinion6is spline-fitted to the outer periphery of the inner tube5bso that it rotates together with the inner tube5b.

As shown inFIG. 4, the electromagnetic switch8includes terminal bolts14and15, a solenoid SL having an excitation coil12, a plunger13and a resin cover16(seeFIG. 3). The terminal bolts14and15are fixed to the resin cover16. The solenoid SL serves as an electromagnet for attracting the plunger13when the excitation coil12is energized. The main contact is disposed inside the resin cover16. The terminal bolt14is a B-terminal bolt (battery terminal) connected to the positive terminal of the battery2through a cable17. The terminal bolt15is an M-terminal bolt (motor terminal) connected with a later explained motor lead wire18. As shown inFIG. 4, the main contact is constituted of a pair of fixed contacts19and a movable contact20. The fixed contacts19are interposed in a power supply line of the motor3through the B-terminal bolt14and the M-terminal bolt15. The movable contact20makes and breaks electrical connection between the fixed contacts19in interlock with movement of the plunger13.

As shown inFIG. 2, the motor lead wire18is connected to the positive side brush11at its one end which is inserted through a gum grommet21fitted to the frame of the motor3and drawn inside the frame, and is connected to the M-terminal bolt15(seeFIG. 3) at its other end drawn outside through the grommet21. Incidentally, in a case where the field system of the motor3is constituted of not permanent magnets but a field winding, it is possible to connect one end of the motor lead wire18to the field winding through a connection bar. As shown inFIG. 3, the frame of the motor3is constituted of the yoke10and an end fame22fitted to the opening of the rear end (the right end inFIG. 3) of the yoke10so as to close the opening. The end frame22is fixed to a front housing22of the starter by tightening through bolts24.

The noise reduction filter9includes at least one capacitor9a(seeFIG. 4), a positive side lead plate25connected to one end of the capacitor9aand a negative side lead plate26connected to the other end of the capacitor9a. The noise reduction filter9is connected to the power supply line through the lead plates25and26in parallel with the motor3. More specifically, as shown inFIG. 1, the positive side lead plate25is connected to the motor lead wire18through a connection fitting27, and the negative side lead plate26is fixed to a pedestal22aformed in the end frame22of the motor3by a bolt28. As shown inFIG. 1, the pedestal22ais formed so as to project radially outward from the outer periphery of the end frame22.

As shown inFIG. 2, the connection fitting27includes a connection arm27aconnected to the positive side lead plate25, and a cylindrical joint section27bformed integrally with this connection arm27a. The joint section27bis fitted in a root section of the motor lead wire18drawn outside the motor3through the grommet21to be electrically connected to the motor lead wire18. The connection fitting27ahas a screw hole formed using a burring tap or the like. The positive side lead plate25and the connection arm27aare electrically connected and mechanically fixed to each other by aligning a circular hole formed in the positive side lead plate25and the screw hole to each other, inserting a screw29into the circular hole and tightening the screw29to the screw hole.

The joint section27b, which is formed by burring work or the like, is pressure-inserted and fixed to the outer periphery of a compressed section formed in one end side of the motor lead wire18. The motor lead wire18is a twisted wire constituted of thin conductor wires twisted one another. The one end side of the motor lead wire18is compressed in the radial direction to form the compressed section. As shown inFIG. 2, the diameter of a portion of the compressed section inserted into the grommet21(referred to as the “grommet-inserted portion18a” hereinafter) is different from the diameter of a portion of the compressed section fitted with the joint section27b(referred to as the “joint-fitted portion18b” hereinafter). The grommet-inserted portion18ais slightly thinner than the joint-fitted portion18b, so that a step is present between the grommet-inserted portion18aand the joint-fitted portion18b. This step serves as a positioning reference with respect to the grommet21. That is, as shown inFIG. 2, the motor lead wire18is mounted such that the grommet-inserted portion18ais inserted into the grommet21until the step abuts against the outer periphery of the grommet21. The joint section27bis fitted to the outer periphery of the joint-fitted portion18bdrawn outside from the grommet21(the root portion of the motor lead wire18), and the front end surface of the joint section27babuts against the outer periphery of the grommet21.

The embodiment of the invention described above provides the following advantages. The positive side lead plate25of the noise reduction filter9can be electrically connected to the motor lead wire18through the connection fitting27by fitting the cylindrical joint section27bformed in the connection fitting27to the joint fitting section18b(the root portion) of the motor lead wire18. Therefore, it is not necessary to join the connection fitting27to the motor lead wire18within the motor3, and it is possible to retrofit the noise reduction filter9to the outside of the frame after the starter1is assembled. Hence, according to this embodiment, it is not necessary to make changes to the existing assembly line of the starter1.

The noise reduction filter9can be easily connected to the connection fitting27by overlapping the positive side lead plate25on the connection arm27ain the thickness direction and screwing them together. The noise reduction filter9is fixed by tightening the negative side lead plate26to the pedestal22aformed in the end frame22of the motor3using the bolt28. This structure enables fixing the noise reduction filter9easily to the end frame22of the motor3utilizing the negative side lead plate26without using an additional part such as a stay. Hence, according to this embodiment, it is possible to improve resistance to vibration of the starter.