An auxiliary rotation-system starter includes a starter motor, a main circuit portion having a main contact portion, an auxiliary circuit portion having a driving coil portion for opening or closing the main contact portion, and a fuse for cutting the current flow to the driving coil portion by fusing at a predetermined temperature. The main circuit portion is connected between the starter motor and a power source. The auxiliary circuit portion is connected in parallel with the main contact portion. The fuse is provided in the auxiliary circuit portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an auxiliary rotation-system starter which is used in starting an engine of an automobile for example.

2. Description of the Related Art

FIG. 8is an electrical connection diagram showing a configuration of a conventional auxiliary rotation-type starter disclosed in Japanese Utility Model Laid-open No. Sho 57-174760. Referring now toFIG. 8, in a conventional auxiliary rotation-system starter101, a starter motor102is electrically connected to a battery power source105through a main circuit portion103and an auxiliary circuit portion104connected in parallel with the main circuit portion103. The main circuit portion103has a main contact portion106for enabling or disabling the electrical connection between the battery power source105and the starter motor102. The auxiliary circuit portion104has a driving coil portion107for opening or closing the main contact portion106. The auxiliary circuit portion104is provided with a relay108for enabling or disabling the electrical connection between the battery power source105and the driving coil portion107. In addition, the main circuit portion103is provided with a fuse109. The fuse109is disposed between the main contact portion106and the starter motor102.

A pinion gear110which serves to be moved axially along with the opening or closing of the main contact portion106is coupled to the starter motor102. In addition, a ring gear111which is coupled to an engine is disposed in the vicinity of the pinion gear110. The pinion gear110is engaged with the ring gear111due to the movement thereof resulting from the closing of the main contact portion106.

Next, the operation of the auxiliary rotation-system starter101will hereinbelow be described. First of all, closing the relay108energizes and activates the driving coil portion107and the starter motor102, respectively. At this time, since the starter motor102is activated through the driving coil portion107, a relatively small torque is supplied to an output shaft of the starter motor102to put it into a state of auxiliary rotation. In addition, since the driving coil portion107is energized, closing of the main contact portion106starts along with the pinion gear110being moved towards the side of the ring gear111. As a result, the pinion gear110is moved as it is being auxiliarly rotated.

The pinion gear110is brought into contact with the surface of the ring gear111due to this movement. At this time, since this operation entails the auxiliary rotation, the pinion gear110is slid while being pressed against the surface of the ring gear111. At this time, when the teeth of the pinion gear110have reached the insertion position between the teeth of the ring gear111due to the sliding, the teeth of the pinion gear110are inserted between the teeth of the ring gear111so that the pinion gear110is engaged with the ring gear111. In addition, concurrently with the engagement, the main contact portion106is closed. Closing the main contact portion106causes a current to flow through the main circuit portion103to rotate the starter motor102at high speed, thereby cranking the engine.

Although in such an auxiliary rotation-system starter101, there is a fear that the temperature of the main circuit portion103and the auxiliary circuit portion104can become extremely high due to, for example long current flow during cranking, the overruns or the like, the fuse109provided in the main circuit portion103will fuse, thereby preventing this extremely high temperature state from occurring.

However, since the value of the current made to flow through the starter motor102during the cranking is larger than that of the current made to flow through the starter motor102during the auxiliary rotation, the melting capacity of the fuse109provided in the main circuit portion103is set with the value of the current made to flow therethrough during cranking as the reference. With such capacity setting for the fuse109, however, no current during the auxiliary rotation is cut off. For this reason, in the case where the pinion gear110is not perfectly engaged with the ring gear111due, for example, to catching on an alien substances, scratches or the like for example so that the auxiliary rotation of the starter motor is continuously carried out, there is encountered the problem that the current is made to flow continuously through the driving coil portion107for a long time, causing the coil thin film to fuse.

SUMMARY OF THE INVENTION

In the light of the foregoing, the present invention has been made in order to solve the above-mentioned problems associated with the prior art, and it is, therefore, an object of the present invention to provide an auxiliary rotation-system starter which is capable of preventing a driving coil portion from being thermally damaged due to a long current flows during start-up.

According to the present invention, an auxiliary rotation-system starter includes a starter motor, a main circuit portion having a main contact portion, an auxiliary circuit portion having a driving coil portion for opening or closing the main contact portion, and a fuse for cutting the current flow to the driving coil portion by fusing at a predetermined temperature. The main circuit portion is connected between the starter motor and a power source. The auxiliary circuit portion is connected in parallel with the main contact portion. The fuse is provided in the auxiliary circuit portion.

Consequently, auxiliary rotating state is prevented from being maintained for a long time due to the fusing, which makes it possible to prevent the driving coil portion from being melted or thermally damaged.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1is an electrical connection diagram showing a configuration of an auxiliary rotation-system starter according to a first embodiment of the present invention. Referring now toFIG. 1, in an auxiliary rotation-system starter1, a starter motor3is electrically connected to a power source2through both a main circuit4and an auxiliary circuit portion5connected in parallel with the main circuit portion4. The main circuit4has a main contact portion7for enabling or disabling the electrical connection between the power source2and the starter motor3. The auxiliary circuit portion5has a driving coil portion8for opening or closing the main contact portion7. In addition, the auxiliary circuit portion5is provided with a fuse6, and a relay contact portion13for enabling or disabling the electrical connection formed from the power source2to the driving coil portion8and the starter motor3. The fuse6is disposed between the power source2and the relay contact portion13. Also, the fuse6is electrically connected to the power source2through a connection terminal32and also is electrically connected to the relay contact portion13through the connection terminal33.

In addition, a start-up circuit portion14is electrically connected to the power source2. The start-up circuit portion14is provided with a relay coil portion15for opening or closing the relay contact portion13, and a key switch16for enabling or disabling the electrical connection between the relay coil portion15and the power source2.

Furthermore, a holding coil portion17for opening or closing the main contact portion7and keeping the main contact portion7closed is connected in parallel with both the driving coil portion8and the starter motor3. It should be noted here that both the driving coil portion8and the holding coil portion17are electrically connected to the relay contact portion13through a connection terminal34.

The main contact portion7includes a power source side fixed contact9which is electrically connected to the power source2through a connection terminal28, a starter motor side fixed contact10which is electrically connected to the starter motor3through a connection terminal29, and a movable contact11which is movably provided in such a way as to be able to contact or part from both the power source side fixed contact9and the starter motor side fixed contact10. The movable contact11is mounted to a rod-like movable portion12which serves to be driven by causing a current to flow through the driving coil portion8and the auxiliary coil portion17.

The relay contact portion13includes a first fixed contact19which is electrically connected to the power source2through a connection terminal30, a second fixed contact20which is electrically connected to the driving coil portion8through a connection terminal31, and a relay movable contact21which is movably provided in such a way as to be able to contact or part from both the first fixed contact19and the second fixed contact20.

Here, the main coil portion18is constituted by the driving coil portion8and the holding coil portion17. In addition, an electromagnetic switch24is constituted by the main contact portion7, the main coil portion18and the movable portion12. Moreover, a relay switch37is constituted by the relay contact portion13and the relay coil portion15.

FIG. 2is a sectional side elevation view of the auxiliary rotation-system starter of the first embodiment shown inFIG. 1, andFIG. 3is a front view when viewed along arrow A of FIG.2. Referring now toFIGS. 2 and 3, the starter motor3is mounted together with the electromagnetic switch24to a housing39. The pinion gear23which serves to be engaged with the ring gear26coupled to the engine is coupled to an output shaft of the starter motor3through an over-running clutch22. In addition, the electromagnetic switch24is provided adjacent to the starter motor3in such a way that the axis of the movable portion12becomes parallel with the axis of the starter motor3. The movable contact11is attached to one end portion12aof the movable portion12, and an engagement portion25having a small diameter portion25aand a disc portion25bis formed on the other end portion12bthereof.

In addition, the movable portion12and the output shaft of the starter motor3are coupled to each other through a lever27. The lever27is pivotably provided on a pin member36which is disposed between the axis of the movable portion12and the axis of the starter motor3. Moreover, one end portion27aof the lever27is disposed in the small diameter portion25aof the engagement portion25, and the other end portion27bthereof is disposed between the starter motor3and the over-running clutch22.

The relay switch37is mounted to the housing39through a mounting member40. In addition, the relay switch37is unitized loaded with the fuse6.

Here, the fuse6has a meltable member35which can be melted due to rises in temperatures there at due to the current flow therethrough. The meltable member35is adapted to fuse when a time period of the current flow through the main coil portion18is longer than that of the current flow therethrough in the normal auxiliary rotating operation. That is to say, the melting temperature of the meltable member35is set in such a way that the member35should fuse before the driving coil portion8has been thermally damaged due to the current flow. The meltable member35is made of zinc (Zn: melting temperature of 420° C.) as a material having a lower melting temperature than that of copper (melting temperature of 1,083° C.). The fuse6is provided so as to be exposed to the outside in order to allow exchange.

It should be noted here that the connection terminals28,29and34are all mounted to the electromagnetic switch24. In addition, the connection terminals30and31are both mounted to the fuse6. Moreover, each of these connection terminals28to34is constituted by a bolt and a nut.

The auxiliary rotation-system starter1constructed as described above operates in the start-up of an engine as follows. First of all, the key switch16is turned ON to cause a current to flow through the relay coil portion15. Then, the relay contact portion13is closed through the electromagnetic operation of the relay coil portion15due to that current flow. Upon closing the relay contact portion13, a current is supplied from the power source2to the starter motor3through the auxiliary circuit portion5. While this current flow drives the starter motor3, since the current is made to flow through the driving coil portion8as well which is connected in series with the starter motor3, a relatively small torque is supplied to the output axis of the starter motor3to provide an auxiliary rotating state. At this time, the movable portion12is also moved through the electromagnetic operation of the driving coil portion8and the holding coil portion17. Along with the movement of the movable portion12, the movable contact11of the main contact portion7is moved towards the power source side fixed contact9and the starter motor side fixed contact10, and the one end portion27aof the lever27is also moved to pivot around the pin member36while being engaged with the engagement portion25. Along with this pivotal movement, the over-running clutch22is pressed by the other end portion27bof the lever27to be moved together with the pinion gear23in the pressing direction.

Thereafter, the pinion gear23is brought into contact with the surface of the ring gear26. At this time, since this movement entails the auxiliary rotation, the pinion gear23is slid while being pressed against the surface of the ring gear26. At the time when the teeth of the pinion gear23have reached the insertion position between the teeth of the ring gear26through this sliding movement, the teeth of the pinion gear23are inserted between the teeth of the ring gear26so that the pinion gear23is engaged with the ring gear26. At this time, the movable contact11of the main contact portion7also comes into contact with both the power source side fixed contact9and the starter motor side fixed contact10to close the main contact portion7.

Since the potential difference barely develops across the connection terminals29and30of the driving coil portion8after the main contact portion7has been closed, only a small quantity of current required to keep the main contact portion7closed is made to flow through the holding coil portion17, while most of the current is supplied to the starter motor3through the main circuit portion4. At this time, a large torque is supplied to the output axis of the starter motor3to provide the cranking state.

In the case where the pinion gear23is not perfectly engaged with the ring gear26for some reason or other, e.g., deformation or the like of the pinion gear23or the ring gear26, even if a current is made to flow through the auxiliary circuit portion5, the main contact portion7is not closed at all. In such a manner, if the state in which the main contact portion7is not closed, even though the current is made to flow through the auxiliary circuit portion5, i.e., the auxiliary rotating state continues, then the temperature of the auxiliary circuit portion5rises. Thereafter, the meltable member35of the fuse6is fused before the auxiliary circuit portion5becomes abnormally hot due to the rise in the temperature.

Consequently, in such an auxiliary rotation-system starter1, even when the pinion gear23is not perfectly engaged with the ring gear26for some reason or other, the auxiliary rotating state is prevented from being maintained for a long time due to the fusing, which makes it possible to prevent the coil thin film of the driving coil portion8from being melted or thermally damaged.

In addition, since the fuse6is not provided in the main circuit portion4through which a large current is made to flow in the cranking state, but is provided in the auxiliary circuit portion5to which the driving coil portion8is connected, it is possible to set the cut-off capacity to the value of the current flowing through the driving coil portion8as the reference, and also it is possible to prevent the coil thin film of the driving coil portion8from being melted or thermally damaged with the value of the current flowing through the main circuit portion4in the cranking state being ensured.

In addition, since the meltable member35of the fuse6is made of zinc having a lower melting temperature than that of copper, it is possible to suppress that thermal damage, etc, to the peripheral parts or components, e.g., a supporting member for the fuse6. Moreover, since the meltable member35can be made in such a way that its temperature reaches its melting temperature due to the long current flow without its cross section being made extremely small, the cut-off capacity at a small level can be ensured while strength is maintained. As a result, for the meltable member35, the occurrence of cutting due to vibration for example is also suppressed.

In addition, since the fuse6is mounted so as to be exposed to the outside, even when it fuses, it can be readily exchanged for a new one.

Second Embodiment

FIG. 4is an electrical connection diagram showing a configuration of an auxiliary rotation-system starter according to a second embodiment of the present invention. Also,FIG. 5is a front view showing construction of the auxiliary rotation-system starter of the second embodiment shown in FIG.4. Referring now toFIGS. 4 and 5, a fuse6in an auxiliary rotation-system starter41is provided between a relay contact portion13and a main coil portion18of an auxiliary circuit portion5. That is to say, a connection terminal33for the fuse6is electrically connected to a connection terminal31of a relay contact portion13, and a connection terminal32therefore is electrically connected to a terminal34of a main coil portion18. It should be noted here that connection terminal28and connection terminal30are electrically connected to each other without going through a fuse.

Other constituent elements in the configuration are the same as those of the first embodiment.

Consequently, since the fuse6is provided in the auxiliary circuit portion5of in the auxiliary rotation-system starter41as well, it is possible to set the cut-off capacity with the value of the current flowing through the drive coil portion8as the reference and to prevent the coil thin film of the driving coil portion8from being melted or thermally damaged with the value of the current flowing through the main circuit portion4in the cranking state being secured.

In addition, since the meltable member35of the fuse6is made of zinc having a lower melting temperature than that of copper, it is possible to suppress thermal damage in peripheral parts or components, e.g., a supporting member for the fuse6, and the like. Moreover, since the meltable member35can be made in such a way that it reaches melting temperature due to long current flow without its cross section being made extremely small, the cut-off capacity can be ensured at a lower level while still maintaining strength. As a result, for the meltable member35, the occurrence of breakage due to vibration, for example, is also suppressed.

In addition, since the fuse6is mounted so as to be exposed to the outside, even when it fuses, it can be readily exchanged for a new one.

Third Embodiment

FIG. 6is an electrical connection diagram showing a configuration of an auxiliary rotation-system starter according to a third embodiment of the present invention. Also,FIG. 7is a front view showing construction of the auxiliary rotation-system starter of the third embodiment shown in FIG.6. Referring now toFIGS. 6 and 7, a fuse6in an auxiliary rotation-system starter51is provided in an auxiliary circuit portion5. In addition, the fuse6is provided between a driving coil portion8and a starter motor3. That is to say, a connection terminal33for the fuse6is electrically connected to the driving coil portion8, and a connection terminal32therefore is electrically connected to a connection terminal29. In addition, the fuse6is not mounted to a relay switch37, but is mounted to an electromagnetic switch24. It should be noted here that connection terminal28and connection terminal30are electrically connected to each other without going through a fuse.

Other constituent elements in this configuration are the same as those of the first embodiment.

Consequently, the auxiliary rotation-system starter51of the third embodiment offers the same effect as that of the first embodiment. Also, since the fuse6is mounted to the electromagnetic switch24, even when the relay switch37is not mounted on from the auxiliary rotation-system starter51, a generally used relay switch is connected to the auxiliary rotation-system starter51, whereby it is possible to prevent the auxiliary rotating state from being maintained for a long time. Consequently, any of the relay switches can be applied irrespective of specification as long as it has a contact point opening/closing capacity with which a current flowing through the auxiliary circuit portion5in the normal auxiliary rotating operation can be cut off.

It should be noted here that in the first and second embodiments as well, since in the auxiliary rotation-system starter, the fuse6may also be mounted to the electromagnetic switch24, similar to the foregoing, any relay switch which are generally used may also be applied thereto.

In addition, in the above-mentioned first to third embodiments, since the meltable member of the fuse may also be made of a material having a lower melting temperature than that of copper, the meltable member may be made of a material which is selected from the group consisting of zinc alloy, tin (Sn: melting temperature 232° C.), lead (Pb: melting temperature 327° C.), alloy thereof and aluminum (Al: melting temperature 660° C.) for example. Since the meltable member made of such a material has a larger cross section than that of the meltable member made of copper, both of anti-shock characteristics and the cut-off capacity are ensured. Consequently, the meltable member may be made of any of electrically conductive materials a melting temperature of which is in the range of about 200 to about 700° C.

While the present invention has been particularly shown and described with reference to the preferred embodiments and the specified modifications thereof, it will be understood that various changes and other modifications will occur to those skilled in the art without departing from the scope and spirit of the invention. The scope of the invention is, therefore, to be determined solely by the appended claims.