Starter device for an internal combustion engine

A starter device for an internal combustion engine includes a starter housing, an electric motor and an engagement pinion driven in rotation by the motor around the pinion rotation axis, the pinion being movable in a translational motion along its pinion rotation axis between a retracted position and an engaging position for engaging a gear connected to the internal combustion engine, the translational motion being caused by the rotation of the electric motor, the starter device further comprising a non-rotatable element which is blocked in rotation with respect to the starter housing, a rotatable element driven in rotation by the electric motor, a helical linkage between the non rotatable element and the rotatable element for causing the translational motion of the pinion. The non rotatable element is fixed in translation along the pinion rotation axis with respect to the starter housing, the rotatable element can translate with respect to the starter housing, and translation of the rotatable element causes translation of the pinion towards its engaging position. The non-rotatable element includes a retractable clutching member with a pin movable in translational movement, so that the helical linkage can be deactivated.

BACKGROUND AND SUMMARY

The invention relates to a starter device for aft internal combustion engine.

Automotive vehicles, such as tracks, are often equipped with a starter device which drives the internal combustion engine of the vehicle during a starting phase. The starter device includes a pinion which selectively engages a gear connected to the internal combustion engine, e.g. a ring mounted on the flywheel of the engine. The starter device is used only during some sequences and the starting rotation speed may be inferior to the nominal engine rotation speed. To protect the starter motor, which is generally electrically driven, from damages provoked by overspeed and wear, the pinion is engaged with the ring gear only during the starting phase. The starter device therefore comprises an actuation system which engages or disengages the pinion with the ring gear. The actuation system also needs to operate the electrical connection of the starter motor to a power supply of the vehicle.

Known actuation systems comprise an electrical solenoid which moves a plunger linked to a mechanical coupler and an electrical contactor. When electrical current is provided to the solenoid, the subsequent movement of the plunger causes the mechanical coupler to engage the pinion with the ring gear. The electrical contactor then closes an electrical circuit which feeds the starter motor, so that it delivers torque to the internal combustion engine.

The use of such a solenoid implies major drawbacks. This solenoid is made of a significant amount of copper, which is a costly material. As it must generate a relatively long displacement, the volume of the solenoid is significant. The solenoid is therefore relatively heavy and difficult to package within the internal combustion engine arrangement.

To solve this issue, it is known, for example from FR-A-2 886 688, to engage the pinion with the ring gear by using the rotation of the starter motor to cause, the translation of the pinion. A member is engaged to a helical groove of a shaft driven by the starter motor, achieving a helical linkage which drives in translational motion a part which pushes the pinion toward the tins sear.

Such a technique involves a relatively high number of parts including an intermediate part which axially pushes the pinion. Moreover, this intermediate part is also involved in the helical linkage and roust therefore be blocked in rotation, involving additional blocking means and means to permit relative rotation between the pinion and the intermediate part. The starter is therefore complex to assemble.

It is desirable to provide a new starter device in which the helical linkage which produces the translation of the pinion involves fewer parts and works in a less complex way than in the prior art.

An aspect of the invention concerns a starter device for an internal combustion engine, said starter device comprising a starter housing, an electric motor and an engagement pinion driven in rotation by said motor around the pinion rotation axis, the pinion being movable in a translational motion along its pinion rotation axis between a retracted position and an engaging position for engaging a gear connected to the internal combustion engine, the translational motion being caused by the rotation of the electric motor, the starter device further comprising a non-rotatable element which is blocked in rotation with respect to the starter housing, a rotatable element driven in rotation by the electric motor, and a helical linkage between the non-rotatable element and the rotatable element for causing the translational motion of the pinion. This starter device is characterized in that the non-rotatable element is fixed in translation along the pinion rotation axis with respect to the starter housing in that the rotatable element can translate with respect to the starter housing, and in that translation of the rotatable element causes translation of the pinion towards its engaging position.

Thanks to an aspect of the invention, the non-rotatable element of the helical linkage is fixed in translation, instead of being movable in translation to engage the pinion with the flywheel ring. The translation is therefore directly transmitted to the rotatable element, avoiding the use of means to allow relative rotation between the pinion and the rotatable element.

According to further aspects of the invention which are advantageous but not compulsory, such a starter device may incorporate one or several of the following features:The helical linkage can be deactivated. This permits to more easily return the pinion to its non-engaging position, without needing to reverse the rotation direction of the starter motor.The non-rotatable element may comprise a retractable clutching member mounted in the starter housing. The retractable clutching member may be movable between a first deactivated position and an activated position with respect to the starter housing. A helical groove may be provided on an outer surface of the rotatable. The retractable clutching member may be engaged in the helical groove when the retractable clutching member is in its activated position.The rotatable element may comprise a transmission shaft driven by the electric motor and movable in translational movement with respect to the housing, between a first position, in which the pinion is in its non-engaging position, and a second position, in which the pinion can be in its engaging position.The starter device may comprise a resilient element adapted to urge the transmission shaft towards its first position. This permits to pull back the pinion towards its non-engaging position automatically, without using positive power from the motor for example.The helical linkage may be deactivated by retracting the retractable clutching member from the helical groove.An end of the helical groove may open in a peripheral groove, radial to a rotation axis of the rotatable member, in which the retractable clutching member may be received when the pinion is completely engaged with the ring gear. This permits to allow rotation of the pinion without inducing translation of the pinion, without necessarily deactivating the clutching member.The retractable clutching member can be movable between its first deactivated position and its activated position along a translational movement along a transversal axis.The retractable clutching member may be movable from its first deactivated position, to a second position where its clutching portion is hi contact with the outer surface of the rotatable element, to a third position where its clutching portion is received in the helical groove and to a fourth position where its clutching portion is received in the peripheral groove. One advantage of this feature is that, by detecting the position retractable clutching member, it can possible to determine in which state the starter is.

The starter device may comprise a resilient element which urges the retractable clutching member towards its deactivated position.The feeding of the starter motor with electrical current may be controlled by the movement of the retractable clutching member.The retractable clutching member may comprise a main contact plate adapted to close a high power circuit for the starter motor (M), for example by making a contact with a first and a second connecting tabs in order to allow nominal power in the starter motor, when the retractable clutching member is in the groove radial to the rotation axis of the pinion, so as to drive the starter motor at a nominal torque or rotation speed. In other words, the main contact plate closes a high power circuit for the starter motor.The retractable clutching member may comprise a preliminary contact plate adapted to close a low power circuit, for example by making a contact with a third and a fourth connecting tabs in order to allow reduced power in the starter motor, when the retractable clutching member is in the helical groove, so as to drive the starter motor at a low torque or rotation speed. In other words, the preliminary contact plate closes a low power circuit for the starter motor. The depth of the helical groove may be inferior to the depth of the peripheral groove. This permits to engage the pinion with minimal potential damages.

In the deactivated position of the retractable clutching member, the main and preliminary contact plates and the connecting tabs may be located so that, during the movement of the retractable clutching member towards the helical groove, the contact between the preliminary contact plate and the third and fourth connecting tabs is made before the contact between the main contact plate and the first and second connecting tabs. Thereby, the preliminary contact plate closes the low power circuit before the main contact plate closes the high power circuit.

The preliminary contact plate may close the low power circuit, for example by connecting the third and fourth connecting tabs, when the retractable clutching member is in its second and third positions and the main contact plate may close the high power circuit, for example by connecting the first and second connecting tabs, when the retractable clutching member is in its fourth position.

The main and preliminary contact plates may be movable in translation with respect to the retractable clutching member along a longitudinal axis of the retractable clutching member.

The electrical contact between the preliminary contact plate and the third and fourth connecting tabs may be kept, thereby keeping the low power circuit closed, by a resilient element mounted between the main contact plate and the preliminary contact plate, and the electrical contact between the main contact plate and the first and second connecting tabs may be kept, thereby keeping the high power circuit closed, by a resilient element mounted between the first contact plate and a collar of the retractable clutching member.

The pinion may be movable hi translational movement with respect to the rotatable element, and wherein a resilient element urges the pinion towards an end of the rotatable element located on the side of the ring gear. In case of a tooth-against-tooth situation, this permits to effectively engage the pinion by allowing it to rotate in the right angular position.

DETAILED DESCRIPTION

As represented onFIGS. 1 to 3, a starter device D for an internal combustion engine comprises a starter motor M and an actuation system S which permits to cause the engagement of a pinion10of the starter device with a ring gear12of the internal combustion engine. Pinion10is driven by starter motor M. In some embodiments, starter motor M may be connected either through a first low power electrical circuit C, in order to deliver reduced power and to obtain a low toque or rotation speed, for engaging pinion10with ring gear12, or through a second high power circuit C2, in order to deliver a nominal power to obtain a nominal torque or rotation speed of motor M, for starting the internal combustion engine. Electrical, circuits C1and C2may respectively comprise a low power set of coils and a high power set of coils in the motor, and/or may comprise low and high power sources of electrical current. The electrical current may be delivered by a battery set of an automotive vehicle, such as a truck, on which the internal combustion engine and starter device D may be integrated.

According to a non-shown embodiment of the invention, starter motor M may controlled only at high power, and pinion10may be engaged with ring gear12directly at the nominal torque or rotation speed of starter motor M.

Starter motor M may comprise an output shaft2rotating around a rotation axis X-X′, which is a longitudinal axis of output shaft2. In this embodiment, axis X-X′ forms the rotation axis of pinion10. In this embodiment, output shaft2may be divided into three sections2a,2band2c. First section2ais directly driven by starter motor M. Second section2bis coupled in rotation to first section2avia an optional reduction gear3. Third section2eis coupled in rotation to second section2bvia a one-way clutch4. One-way clutch4operates so that, second section2bcan drive third section2conly in one direction, while third section2ccannot drive second section2balong that direction. This means third section2ccan rotate at a higher rotation speed than second section2b.

The translational motion of pinion10towards ring gear12from a retracted position, towards an engaging position is caused by the rotation of starter motor M. The rotational motion of starter motor M is transformed into a translation motion by means of a helical linkage between a rotatable element, which is driven in rotation by starter motor M by being coupled in rotation with output shaft2, and a non-rotatable element with respect to which the rotatable element rotates and which is blocked in rotation, around the rotation axis of the rotatable element with respect to a housing H of starter device D.

The non-rotatable element is fixed in translation with respect to housing H along axis X-X′, while the rotatable element can translate with respect to housing H along axis X-X′. Translation of the rotatable element causes translation of pinion10towards its engaging position. The rotatable element is coupled in rotation to the pinion, so that rotation of the pinion10element is directly linked to the rotation of the rotatable element.

The rotatable element may be a transmission shaft6. Transmission shaft6may be coupled in rotation with output shaft2via its third section2cthanks to splines2cl. Indeed, the end of third section2cwhich is opposed to one-way clutch4may comprise rectilinear splines2cl. The splines2caof the output shaft may cooperate with non-shown rectilinear splines of transmission shaft6. Splines2clallow translation of transmission shaft6with respect to the housing H. In this embodiment, output shaft2and transmission shaft6extend along the same axis, i.e. rotation axis X-X′. However, they could be arranged along two parallel but distinct axes.

Pinion10is mounted on an end64of transmission shaft6opposed to third section2c. Pinion10is coupled in rotation with the transmission shaft, for example via respective mating splines on the pinion and on the end64of the transmission shaft. Transmission shaft6is movable in translation along axis X-X′ with respect to output shaft2between a first position, represented onFIG. 1, in which pinion10is not engaged with ring gear12, and a second position represented onFIG. 2, in which pinion10can be fully engaged with ring gear12(although it will be described further that further means may be provided to allow the transmission shaft to reach its second position even if the pinion is blocked before its engaging position by the ring gear). Transmission shaft6is preferably urged towards its first position by a resilient element, such as a spring72.

The rotation of transmission shaft6may be allowed by a rolling bearing8mounted between transmission shaft6and housing H starter device D. An outer ring80of rolling bearing8is coupled in rotation to housing H, while an inner ring82of rolling bearing8is coupled in rotation to transmission shaft6. Transmission shaft6is free to move along axis X-X′ with respect to inner ring82thanks to non-shown sliding means, such as splines, of via a plain bearing.

In the shown embodiment, the non-rotatable element involved in the helical linkage is a controlled retractable clutching member, which can for example be electrically controlled. In this embodiment, the retractable clutching member comprises a pin14, which is movable in translational movement with respect to housing H along a transversal axis Y-Y′ which may be perpendicular to axis X-X′ and which forms a longitudinal axis of pin14. The translational movement of pin14with respect to housing H may be allowed by a bearing ring18, which is mounted in a hole of housing H represented onFIG. 3.

Alternatively, in a non-represented embodiment, the retractable clutching member may be movable in rotational movement with respect to housing H, for example around an axis perpendicular to axis X-X′, and may comprise a radially extending member for activating the helical linkage.

Transmission shaft6comprises a peripheral groove60which is radial to axis X-X′. Transmission shaft6also comprises a peripheral helical groove62which is adjacent to peripheral groove60. An end of helical groove62opens in groove60. Grooves60and62are realized in an outer surface61of transmission shaft6.

The retractable clutching member comprises a clutching portion able to engage the grooves, so as to form a fixed abutment for the groove along the direction of translation of the rotatable member when if is engaged. The clutching portion is compatible in shape with the grooves inasmuch as is must be received in the grooves without blocking the rotation of the rotating member. In the case of a retractable clutching member in the form of a pin, as in the shown embodiment, the tip of the pin forms a clutching portion of the retractable clutching member. However, the clutching portion could exhibit other shapes, such as a shape complementary to that of the helical groove, for example in the form of sector of a helical tooth so as to increase the contact surface between the helical grove and the clutching portion.

Pin14is spring biased towards a retracted position, represented onFIGS. 1 and 3, by a spring16. In its retracted position, pin14is remote from transmission shaft6, so that the helical linkage is deactivated.

Pin14comprises a central portion141which is made of a metallic magnetic material. Central portion141is mounted radially within a solenoid19which surrounds central portion141. Solenoid19is electrically connected to the battery set of the vehicle, via a controller191adapted to activate or deactivate the passage of electrical current in solenoid19. Passage of current in solenoid19urges pin14towards helical groove62, against the action of spring16.

When the tip of pin14, which may be formed by a ball143, is received in helical groove62the helical linkage between pin14and transmission shaft6is activated and causes a translational movement of transmission, shaft6along axis X-X′, towards ring gear12, when motor M drives output shaft2. Ball143allows relative rotation between transmission shaft6and pin14and limits friction in between.

In the shown embodiment, feeding of starter motor M with electrical current is controlled by the motion of the retractable clutching member. In this embodiment, the feeding of starter motor M is controlled by the translational motion of pin14. As represented onFIG. 3only, pin14comprises, on a side of central portion141opposite to axis X-X′, a rod142which extends along axis Y-Y′. Around rod142and perpendicularly to axis Y-Y′, pin14comprises two contact plates144and146, each made of an electrically conducting material. A main contact plate146is located further away from central portion141than a preliminary contact plate144. Contact plates144and146are respectively adapted to close some electrical circuits C1and C2corresponding to low power and high power circuits for the starter motor M.

An insulating sleeve148is mounted between, rod142and contact plates144and146, so that no electrical contact can take place between contact plates144and146and rod142, or between contact plates144and146themselves. Contact plates146and144are mounted around insulating sleeve148, so that they can move in translational movement along axis Y-Y′ with respect to rod142of pin14. As can be seen onFIG. 3, the sleeve148has two abutment surfaces which define the rest positions of the plates144,146. As shown onFIG. 3, these abutment surfaces may be formed by annular surfaces of the sleeve formed by three consecutive portions of decreasing diameters of the sleeve148. Each abutment surface is formed at the limit between two consecutive portions of different diameter of the sleeve. The abutment surfaces are turned away from the transmission shaft6. The abutment surfaces could also be formed by elastic rings mounted in corresponding annular grooves formed in the exterior surface of the sleeve.

A first spring149is mounted around insulating sleeve148between the preliminary contact plate144and the main contact plate146. Spring149tends to move contact plate144away from contact plate146, towers the helical groove and, in the rest position ofFIG. 3, it presses the preliminary contact144plate against the corresponding abutment surface of the sleeve.

A second spring151is mounted around insulating sleeve148between contact plate146and a collar153which is fixed on rod142and extends radially from rod142at the end of rod142located opposite from central portion141. Spring151tends to move contact plate146away from collar153, towards the transmission shaft. In the rest position ofFIG. 3, the spring151presses the main contact plate146against the corresponding abutment surface of the sleeve.

The stiffness of spring151may be superior to the stiffness of spring149so that, at the rest position, the two contact plates144and146are pressed against their corresponding abutment surfaces.

In order to prevent any electrical contact between contact plates144and146and springs149and151, the portions of contact plates144and146on which springs149and151are mounted comprise a layer of insulating material, which is not represented on the figures for the sake of clarity.

In case pinion10is engaged directly at the nominal torque or rotation speed of starter motor M, pin14only comprises one contact plate146for closing the high power electrical circuit C2so that the motor M delivers directly its nominal torque or speed.

Actuation system S works in the following way: actuation pin14is initially retracted in its position ofFIGS. 1 and 3, away from the transmission shaft6, under the action of spring16. In this position, the contact plates144and146are in their respective rest position and do not contact the tabs T1to T4, so that both circuits C1and C2are open. The starter motor M is at standstill. When the internal combustion engine must be started, a starting signal is transmitted to controller191so that electrical current passes in solenoid19. This causes pin14to move towards axis X-X′, i.e. towards the transmission shaft6, as represented by arrow A1onFIG. 3. Because of the movement of pin14along axis Y-Y′, preliminary contact plate144contacts a fixed connecting tab T1of actuation system S. Preliminary contact plate144also contacts a fixed connecting tab T2which is electrically connected to motor M. Connecting tabs T1and T2correspond to the low power circuit C1. Thus, the contact between preliminary contact plate144and connecting tabs T1and T2allows passage of electrical current towards starter motor, which begins to rotate at a low torque or rotation speed. Once preliminary contact plate144is in contact with connecting tabs T1and T2, preliminary contact plate144is kept in contact against connecting tabs T1and T2by spring149, but allows further movement of the pin14.

During its translational motion along arrow A1, pin14may enter in contact with outer surface61. As starter motor has begun to rotate under the action of low power circuit C1, helical groove62rotates together with transmission shaft6. As pin14is permanently pushed towards axis Y-Y′, helical groove62rotates until ball143of pin14enters helical groove62so that the pin is then engaged in the helical groove. Because of the helical shape of groove62, the cooperation of helical groove62and pin14causes transmission shaft6to move along axis X-X′ towards ring gear12, as represented by arrow A2onFIG. 1. During this translational movement, pinion10comes closer to ring gear12until the teeth of pinion10and the teeth of ring gear12engage with each other.

As long as the tip of pin14formed by ball143lies within helical groove62, the movement of pin14in the direction of arrow A1is limited by the fact that ball143abuts against the bottom of helical groove62.

When pinion10and ring gear12are properly engaged as represented onFIG. 2, the transmission shaft has translated along its axis to such an extent that the ball of the pin has travelled the full length of the helical groove62and now faces the peripheral groove60. Therefore, the ball143of pin14gets into peripheral groove60, at the end of helical groove62. The depth of groove60is superior to the depth of helical groove62. As pin14is still pushed along axis Y-Y′ by solenoid19, pin14moves farther towards axis X-X′ until it reaches a position in which main contact plate146comes in contact with a fixed connecting tab T3of actuation system S and with a connecting tab T4which is electrically connected to starter motor M, the connecting tabs T3and T4corresponding to high power circuit C2. The contact between connecting tabs T3and T4and main contact plate146closes the high power electrical circuit C2which allows the starter-motor M to deliver high power or rotation speed. Starter motor M therefore begins to drive output shaft2at its nominal rotation speed, in order to transmit starting torque to gear ring12and start the internal combustion engine. During the starting operation, main contact plate146is kept in contact with connecting tabs T3and T4by spring151.

To guarantee that the force exerted by spring149does not cause main contact plate146from losing contact with connecting tabs T3and T4, the stiffness of spring151may be chosen superior to the stiffness of spring149in such a way that the effort of spring149on main contact plate146is lower than the effort of spring151on main contact plate.

In order to guarantee that the engagement between pinion10and ring gear12works properly, pinion10should preferably first be rotated at a low rotation speed. To this end, starter motor M should preferably be operated at low power, to deliver low torque and rotation speed, until the pinion is properly engaged on the ring gear, before being operated at its nominal power, for delivering its nominal torque or rotation speed. In the retracted position of pin14, contact plates144and146and connecting tabs T1to T4are positioned with respect to each other so that, when the movement of pin14along arrow A1begins, contact is first made between connecting tabs T1and T2and contact plate144. The contact between connecting tabs T3and T4and contact plate146is not made until ball143of pin14reaches peripheral groove60.

In case pinion10is directly engaged with ring gear12at the nominal torque or rotation speed of motor M, starter device D only comprises connecting tabs T3and T4, and the depth of helical groove62may be equal to the depth of groove60.

When pin14reaches groove60, a sensor may generate a signal which warns the driver of the vehicle that pinion10has been properly engaged with ring gear12. Such sensor can be in fact the controller191is said controller can determine the position of pin14along its axis Y-Y′.

In case the teeth of pinion10and ring gear12are aligned along the same axis, pinion10and ring gear12cannot engage with each other properly, because the teeth of ring gear12block the translational movement of pinion10in the direction of arrow A2. Pinion10is therefore mounted on transmission shaft6so that pinion10is movable, along axis X-X′, with respect to end64. Transmission shaft6comprises rectilinear splines66which cooperate with non-shown inner rectilinear splines of pinion0.

The translational movement of pinion10with respect to transmission shaft6opposite to end64is limited by a resilient element, such as a spring68, which urges pinion10towards end64. The translational movement of pinion10towards end64is blocked by an elastic ring70.

Thanks to the relative translational movement possibility between pinion10and transmission shaft6, the translational movement of transmission shaft6in the direction of arrow A2goes on, even if pinion0and ring gear12are in a tooth-against-tooth situation.

Pinion10is therefore moved away from elastic ring70along axis X-X′ in the opposite direction to arrow A2, against the action of spring66, because of the resistance of ring gear12. As transmission shaft6goes on rotating around axis X-X′, pinion10also rotates with respect to ring gear12and the teeth of pinion10and ring gear12become angularly offset, so that pinion10and ring gear12can properly engage with each other. At this moment, under the action of spring66, pinion10is pushed back towards ring gear12and against elastic ring70until the teeth of pinion10and ring gear12are fully engaged with each other, as shown onFIG. 2.

When the internal combustion engine is properly started, pinion10begins to rotate at a rotation speed which is superior to the nominal rotation speed of starter motor M. Thanks to one-way clutch4, transmission shaft6and third section2crotate at the rotation speed of the internal combustion engine, while first and second sections2aand2bcontinue to rotate at the nominal rotation speed of starter motor M. This prevents damages on starter motor M.

When starter motor must be switched-off, pinion10must be retracted from ring gear12. A signal is emitted to controller191, for example from an automated controller which watches the operation of the internal combustion engine, to stop passage of electrical current in solenoid19. As pin14is no more driven along axis Y-Y′ by solenoid19, pin14is pushed back towards its retracted position ofFIG. 3by spring16. Pin14does not block transmission shaft6in its position ofFIG. 2anymore, and transmission shaft6is then pushed back towards its position ofFIG. 1by spring72, as shown by arrow A3onFIG. 2. The retraction of pin14in its first position also suppresses the contacts between first contact plate144and connecting tabs T1and T2and between second contact plate146and connecting tabs T3and T4. The rotation of starter motor M therefore stops.

According to a non-shown embodiment of the invention, the feeding of starter motor M with electrical current may be controlled by the position of transmission shaft6along axis X-X′ instead of the position of pin14along axis Y-Y′.

The features of the above-described embodiments can be combined within the scope of the invention.