JP2009209843A - Starter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant mesh type starter equipped with a shock absorbing function capable of reducing shock occurring during engine stop and engine stall. <P>SOLUTION: This starter is equipped with a reverse rotation preventing clutch 8 for preventing reverse rotation of an armature. The reverse rotation preventing clutch 8 has a clutch outer 81 having the shock absorbing function. Namely, the clutch outer 81 is composed of a fixed outer part 81a fixed non-rotatably to a housing, and a movable outer part 81b press-fitted in the inner periphery of the fixed outer part 81a and restricted in rotation with respect to the fixed outer part 81a by prescribed sliding torque. When load torque (torque generated by reverse rotation of the engine) larger than the sliding torque is applied to an armature shaft, the movable outer part 81b slides in the circumferential direction with respect to the fixed outer part 81a so that the generated shock can be reduced by absorbing the load torque. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a constant mesh starter in which a pinion gear is always meshed with a ring gear on an engine side.

2. Description of the Related Art Conventionally, there is known a constant mesh starter in which a pinion gear is always meshed with an engine side ring gear directly or via an intermediate gear (see Patent Document 1). In this constant mesh starter, the pinion gear does not disengage from the ring gear after the engine is started, and is always meshed. Therefore, restart before the engine stops is possible.
However, in the always-mesh starter, for example, when the engine rotates backward due to the swing of the crankshaft that occurs when the engine stops, or when the engine rotates backward when the vehicle moves backward due to the stall on the climbing path, The reverse rotation is transmitted from the ring gear to the pinion gear, and the rotational force in the direction opposite to that when starting the engine is transmitted to the output shaft of the starter. As a result, the armature of the motor is rotated at the number of rotations multiplied by the gear ratio between the ring gear and the pinion gear (in the case of a starter having an internal reduction gear, the number of rotations multiplied by the internal reduction ratio). In addition to causing a decrease, there is a concern that the armature is damaged by centrifugal force.

Therefore, the present applicant has proposed a starter provided with a reverse rotation prevention clutch capable of preventing reverse rotation of the armature (see Patent Document 2).
The reverse rotation prevention clutch has a wedge-shaped cam chamber formed between an inner provided on the armature shaft of the motor and an outer peripheral surface of the inner, and an outer cam fixed to the housing in a non-rotatable manner. When the engine is started, the roller idles to allow the armature to rotate, and when the reverse rotation of the engine is transmitted to the armature shaft, the roller is narrowed in the cam chamber. By moving in the direction and being locked between the inner and the outer, it has a function of preventing reverse rotation of the armature.

When the reverse rotation of the engine is transmitted to the armature shaft, if the reverse rotation prevention clutch is activated (the roller is locked between the inner and the outer), a large impact is generated in the torque transmission path of the starter. In particular, when the vehicle is stalled, the inertia of the entire vehicle is received by the reverse rotation prevention clutch, so that a very large impact is generated.
On the other hand, the above-mentioned Patent Document 2 proposes setting a frictional torque limiter between the armature and the output shaft on the assumption of an excessive impact input. As a result, when an excessive impact is input from the engine side, the excessive impact can be cut by sliding the friction plate (rotating disk), so that the impact generated in the torque transmission path can be reduced.
JP 2004-225544 A JP 2006-226146 A

However, when a torque limiter is set between the armature and the output shaft, the torque limiter works even when the engine is started by the starter. The problem here is ensuring the torque necessary to start the engine reliably.
In other words, if the friction plate of the torque limiter slips when the engine is started, the torque generated by the motor cannot be transmitted to the ring gear, and the engine cannot be started. Therefore, in order to ensure that the engine can be started even at low and high temperatures, the maximum friction of the engine at low and high temperatures is assumed and the torque required for start-up is calculated. Torque is set (see FIG. 5). In other words, the minimum slip torque of the torque limiter is determined so that the friction plate does not slip and the engine cannot be started, and the slip torque cannot be lowered below this minimum slip torque.

For this reason, even if the excessive impact input from the engine side is reduced by the torque limiter, it is governed by the slip torque of the torque limiter required when starting the engine, so there is a limit to reducing the generated impact. .
Moreover, since the torque limiter described in Patent Document 2 is configured using an internal gear of an internal speed reducer (planetary gear speed reducer), the torque limiter is not used for a structure without an internal speed reducer. Setting was difficult.
The present invention has been made based on the above circumstances, and its purpose is to provide a constant mesh starter having an impact absorbing function capable of improving performance capable of reducing impact generated when the engine is stopped or stalled. Is to provide.

(Invention of Claim 1)
The present invention is a motor that generates a rotational force on an armature shaft, an output shaft that is rotated by transmission of the rotational force of the motor, and an outer periphery of the output shaft that is disposed so as to be relatively rotatable via a bearing, A pinion gear that is always meshed with the ring gear on the engine side and transmits the rotational force generated by the motor to the ring gear, and a reverse rotation prevention clutch that prevents the armature shaft from rotating in the direction opposite to the rotation direction when the engine is started.
The reverse rotation prevention clutch is disposed in the cam chamber, a clutch inner provided on the armature shaft, a clutch outer that is arranged concentrically with the clutch inner, and forms a wedge-shaped cam chamber between the outer periphery of the clutch inner. And when the reverse rotation of the engine is transmitted to the armature shaft, the roller moves in the narrowing direction of the cam chamber and is locked between the clutch outer and the clutch inner. The inner shaft is prevented from rotating to prevent the armature shaft from rotating backward.
The clutch outer used in the reverse rotation prevention clutch forms a cam chamber between a fixed outer portion fixed so as not to rotate and an outer peripheral surface of the clutch inner disposed inside the fixed outer portion. In contrast, a reverse rotation input from the engine side is transmitted to the armature shaft, and a load torque larger than the slip torque is applied to the armature shaft. Sometimes, the movable outer part has a function of absorbing load torque by sliding in the circumferential direction with respect to the fixed outer part.

In the reverse rotation prevention clutch of the present invention, when the rotational force generated by the motor is transmitted from the pinion gear to the ring gear to start the engine (when the engine is started), the roller rotates idly to allow the armature to rotate. In other words, the reverse rotation prevention clutch does not work when the engine is started (the roller is locked between the clutch outer and the clutch inner), and the engine can be normally started.
On the other hand, if the engine reverses when the vehicle is moved backward due to crankshaft swinging or engine stall on the climbing path, and the reverse rotation is input to the starter, the reverse rotation prevention clutch will work. Thus, reverse rotation of the armature can be prevented.

  By the way, when the reverse rotation of the engine is transmitted to the armature shaft and the reverse rotation prevention clutch is operated, an impact is generated in the torque transmission path of the starter. In particular, when the vehicle is stalled, the inertia of the entire vehicle is received by the reverse rotation prevention clutch, so that a very large impact is generated. On the other hand, the reverse rotation prevention clutch of the present invention can reduce the generated impact by the impact absorbing function provided to the clutch outer. That is, since the movable outer portion is restricted from rotating with a predetermined slip torque with respect to the fixed outer portion, the clutch outer is movable when a load torque (torque generated by reverse rotation) larger than the slip torque is applied to the armature shaft. When the outer part slides in the circumferential direction with respect to the fixed outer part, it is possible to reduce the impact generated by absorbing the load torque.

  When the movable outer portion slides with respect to the fixed outer portion, both the roller and the clutch inner begin to move (rotate), so that the armature shaft provided with the clutch inner also rotates (reversely rotates). However, excessive load torque is applied depending on the set value of the slip torque, but when it receives an impact with a very high input speed, it does not occur for a long time. It will not continue to rotate. That is, when the load torque is applied to the armature shaft, the reverse rotation prevention clutch momentarily allows the armature to reversely rotate by sliding, but the load torque is absorbed by the sliding of the movable outer portion. After that, the reverse rotation of the armature can be prevented by the original function.

In the reverse rotation prevention clutch of the present invention, the roller does not run idle when the engine is started and the shock absorbing function does not work. Therefore, it is not necessary to set the slip torque assuming the maximum friction of the engine. That is, the sliding torque of the movable outer portion with respect to the fixed outer portion can be arbitrarily set without being affected by the torque required when starting the engine. Thereby, since the slip torque can be set lower than the conventional friction type torque limiter, the generated impact can be reduced.
Further, by reducing the generated impact, each strength component (for example, a reverse rotation prevention clutch, a planetary gear speed reducer, etc.) can be reduced in size and weight, and cost can be reduced by using a low strength material. .
Furthermore, since the shock absorbing function provided to the clutch outer does not use an internal speed reducer, the constant mesh starter that does not have an internal speed reducer also has a shock absorbing function using a reverse rotation prevention clutch. Can be made.

(Invention of Claim 2)
The starter according to claim 1, wherein the clutch outer is configured such that the movable outer portion is press-fitted into an inner periphery of the fixed outer portion, and a fixing force with respect to rotation in a circumferential direction obtained by the press-fitting is set as a slip torque. To do.
The shock absorbing function of the clutch outer can be provided by a simple structure in which the movable outer portion is press-fitted to the inner periphery of the fixed outer portion, and the press-fit load (fixing force against circumferential rotation obtained by press-fitting) can be provided. The slip torque can be adjusted accordingly.

(Invention of Claim 3)
The starter described in claim 2 is characterized in that a lubricant is applied to a press-fit portion between the fixed outer portion and the movable outer portion.
By applying a lubricant to the press-fit portion, the variation in the friction coefficient can be reduced, so that the target value of the sliding torque can be set to be severe (strict). Further, since the wear of the press-fit surface can be suppressed, durability can be improved.

(Invention of Claim 4)
The starter according to any one of claims 1 to 3, wherein an excessive torque is transmitted from the engine side to the output shaft via a pinion gear when the engine is started, and the reduction gear that decelerates the rotation of the motor and transmits it to the output shaft. And a torque limiter that absorbs the excessive torque, and the speed reducer includes a sun gear provided on the armature shaft, an annular internal gear arranged concentrically with the sun gear, a sun gear, and an internal gear. And a planetary gear speed reducer in which the revolving motion of the planetary gear is transmitted to the output shaft, and the torque limiter is rotatably engaged with the internal gear, and Having a rotating disk whose rotation is restricted by the frictional force, when the excessive torque exceeding the sliding torque of the rotating disk obtained by the frictional force is applied to the internal gear, the rotating disk slides against the frictional force. And by, characterized by absorbing the excessive torque.

The shock absorbing function provided to the clutch outer does not work when the engine is started. However, even when the engine is started, an excessive shock may occur due to, for example, erroneous engine explosion or restart immediately before the engine stops.
On the other hand, the starter of the present invention includes a friction plate (rotating disk) type torque limiter that uses a speed reducer, so that it is possible to reduce the impact generated when the engine is started.

(Invention of Claim 5)
The starter according to any one of claims 1 to 4 is used for an engine automatic stop / restart system that automatically controls stop and restart of the engine.
A vehicle equipped with an automatic engine stop / restart system inevitably increases the number of times the engine is started by the starter. For this reason, when a starter that does not have a reverse rotation prevention clutch is employed in the above system, the frequency of reverse rotation of the armature that occurs each time the engine is stopped greatly increases, which affects the life of the brush. In addition, the number of times an abnormal noise (sliding noise) is generated when the brush slides on the commutator increases, giving the user an unpleasant feeling.
On the other hand, in the present invention, by providing the reverse rotation prevention clutch, the reverse rotation of the armature can be prevented, so that the life of the brush can be improved and the uncomfortable feeling given to the user can be eliminated.

  The best mode for carrying out the present invention will be described in detail with reference to the following examples.

FIG. 1 is a cross-sectional view of a constant mesh starter 1.
As shown in FIG. 1, a starter 1 according to the first embodiment includes a motor 2 that generates a rotational force in an armature 2a, and a main circuit that is provided in a motor circuit for energizing the armature 2a from a battery (not shown). An electromagnetic relay 3 that opens and closes contacts (to be described later), a speed reducer 4 that slows down the rotation of the armature 2a (see FIG. 2), and an output shaft 5 through which the drive torque of the motor 2 is transmitted via the speed reducer 4 And a pinion gear 7 fitted to the outer periphery of the output shaft 5 via a bearing 6, a reverse rotation prevention clutch 8 for preventing reverse rotation of the armature 2a, and the like. The starter 1 can be used for an engine automatic stop / restart system (also called an idle stop, an eco-run system, or the like) that automatically controls engine stop and restart.

The motor 2 is provided with a commutator 9 on one end side (right side in the drawing) of the armature shaft 2b that outputs the rotation of the armature 2a, and the armature 2a is connected to the armature 2a via a brush 10 disposed on the outer periphery of the commutator 9. It is a known commutator motor that is energized. The armature shaft 2b has an end on one end where the commutator 9 is provided rotatably supported by the end frame 12 via a bearing 11, and an end on the counter-commutator side (the other end) has an output shaft. 5 is inserted into the inner periphery of a recess formed in the motor side end through a bearing 13 (see FIG. 2) so as to be relatively rotatable.
The end frame 12 is fitted and assembled to the end opening of the yoke 14 that forms the magnetic circuit of the motor 2, and a plurality of through bolts (not shown) are fastened to the housing 15 and fixed.

The electromagnetic relay 3 is configured by a solenoid that incorporates an electromagnetic coil 16 and a plunger 17, and a main contact is disposed inside a resin cover 18 that is fixed to the solenoid.
The solenoid has a well-known function of attracting the plunger 17 by forming an electromagnet by energizing the electromagnetic coil 16, and the main contact is closed by a movable contact 19 that moves integrally with the plunger 17. When the energization of the electromagnetic coil 16 is stopped and the attraction force of the electromagnet disappears, the reaction force stored in the return spring 20 causes the plunger 17 to be pushed back in the left direction in the figure to open the main contact.

  The main contact is connected to the B potential contact (battery side) of the motor circuit via the B terminal bolt 21 and to the low potential side (motor side) of the motor circuit via the M terminal bolt 23. The fixed contact 24 is formed between the fixed contacts 22 and 24 by the movable contact 19. That is, when the movable contact 19 abuts on both the fixed contacts 22 and 24 and the fixed contacts 22 and 24 are brought into conduction, the main contact is closed, and the movable contact 19 is separated from both the fixed contacts 22 and 24 and fixed on both sides. When the continuity between the contacts 22 and 24 is interrupted, the main contact is opened.

  B terminal bolt 21 and M terminal bolt 23 are respectively fixed to resin cover 18, and a terminal of a battery cable (not shown) is connected to B terminal bolt 21 protruding in the axial direction (right direction in FIG. 1) from resin cover 18. Similarly, the terminal of the motor lead wire 25 is connected to the M terminal bolt 23 protruding in the axial direction from the resin cover 18. The end of the motor lead wire 25 on the side opposite to the terminal (motor side) is drawn into the motor 2 via a rubber grommet 26 sandwiched between the yoke 14 and the end frame 12, and is on the positive electrode side. The brush 10 is electrically connected.

As shown in FIG. 2, the speed reducer 4 is a planetary gear speed reducer that can be decelerated coaxially with the armature shaft 2b. The sun gear 27 formed on the side opposite to the commutator of the armature shaft 2b will be described below. A planetary gear 30 that outputs rotation motion of the planetary gear 29, and a planetary carrier 30 that outputs the revolving motion of the planetary gear 29. A carrier 30 is provided integrally with the output shaft 5.
As shown in FIG. 2, the torque limiter includes a fixed disk 32 that is fixed to the center case 31 so as not to rotate, and a rotating disk that is sandwiched between the fixed disk 32 and the center case 31 and whose rotation is restricted by a frictional force. 33, and a disc spring 34 or the like that sandwiches the rotating disk 33 between the center case 31 and the fixed disk 32 and imparts elasticity in the axial direction, and an excessive torque exceeding the sliding torque of the rotating disk 33 is generated by the internal gear. When applied to 28, the rotating disk 33 slides (rotates) against the frictional force, allowing the internal gear 28 to rotate and interrupting transmission of excessive torque.

The center case 31 is disposed inside the housing 15 at right angles to the output shaft 5, abuts against a step provided on the inner periphery of the housing 15, is positioned in the axial direction, and rotates in the circumferential direction with respect to the housing 15. It has been stopped.
The output shaft 5 is disposed on the same axis as the armature shaft 2b, and the end portion on the side opposite to the speed reducer is rotatably supported on the tip end portion of the housing 15 via a bearing 35 (see FIG. 1). An end on the machine side is rotatably supported by the center case 31 via a bearing 36 (see FIG. 2).
The pinion gear 7 is always meshed with a ring gear 37 on the engine side, and is connected to the output shaft 5 via an impact absorbing device described below.

As shown in FIG. 1, the impact absorbing device includes a ring drive 38 connected to the pinion gear 7, a ring drive 39 connected to the output shaft 5, and a ring space 40 between the ring drive 38 and the ring drive 39. It comprises a plurality of rubber dampers 41 and the like that are incorporated via the vias.
The ring drive 38 is provided with a cylindrical boss portion 38 a at the center in the radial direction, and this boss portion 38 a is spline-fitted to the outer periphery of the cylindrical portion 7 a provided integrally with the pinion gear 7. They are connected so that they cannot rotate relative to each other.
Similar to the ring drive 38, the ring drive 39 is provided with a cylindrical boss portion 39 a at the center in the radial direction, and this boss portion 39 a is spline fitted to the outer periphery of the output shaft 5 to They are connected so that they cannot rotate relative to each other.

The ring space 40 is disposed between the ring drive 38 and the ring drive 39, and is rotatably fitted to the outer periphery of a boss portion 39 a provided in the ring drive 39.
A plurality of damper spaces for accommodating the rubber dampers 41 are formed in the circumferential direction between the ring drive 38 and the ring space 40 facing each other in the axial direction and between the ring space 40 and the ring drive 39. ing.
Each of the rubber dampers 41 is accommodated in the above-described damper space (a total of 6 pieces of 3 × 2 stages per stage in FIG. 1), and through this rubber damper 41, the ring drive 38, the ring space 40, and A ring space 40 and a ring drive 39 are provided so as to be relatively rotatable.

Next, the reverse rotation prevention clutch 8 according to the present invention will be described.
As shown in FIG. 3, the reverse rotation prevention clutch 8 includes a clutch inner 80 provided on the armature shaft 2 b, a clutch outer 81 disposed concentrically with the clutch inner 80, and a clutch inner 80 and a clutch outer 81. The roller 82 is configured to intermittently transmit torque, and the spring 83 biases the roller 82.
The clutch inner 80 is provided on the counter commutator side of the armature shaft 2b and has an outer diameter larger than the tooth tip diameter of the sun gear 27 (see FIG. 2). The clutch inner 80 according to the present embodiment is provided integrally with the armature shaft 2b. For example, a ring shape is provided separately from the armature shaft 2b and is press-fitted to the outer periphery of the armature shaft 2b. May be combined.

The clutch outer 81 is a movable outer portion that forms a wedge-shaped cam chamber 84 between a fixed outer portion 81a that is fixed so as not to rotate and an outer peripheral surface of the clutch inner 80 that is disposed inside the fixed outer portion 81a. 81b.
The fixed outer portion 81a has an outer wall portion 81c extending outward in the radial direction, and the outer peripheral portion of the outer wall portion 81c is between the yoke 14 of the motor 2 and the spacer member 42 (see FIG. 2). A pair of engaging portions 81d (see FIG. 3) which are sandwiched between the two and are positioned in the axial direction and provided on the outer periphery of the outer wall portion 81c are formed in an engaging recess (not shown) on the inner periphery of the housing 15. ) And the rotation is restricted.
The spacer member 42 has a cylindrical shape that covers the space between the center case 31 and the outer wall portion 81c in the axial direction. As shown in FIG. 2, the spacer member 42 has a stepped portion provided on the outer peripheral portion of the center case 31 in the axial direction. The front end is fitted and positioned in the radial direction.

The movable outer portion 81b is press-fitted into the inner periphery of the fixed outer portion 81a, is restricted in rotation with a predetermined slip torque with respect to the fixed outer portion 81a, and a plurality of movable outer portions 81b are provided between the outer peripheral surface of the clutch inner 80 and the like. The cam chamber 84 is formed. A lubricant such as grease is applied to the press-fit portion between the fixed outer portion 81a and the movable outer portion 81b.
As shown in FIG. 4A, the space formed between the cam chamber 84 and the outer peripheral surface of the clutch inner 80 is gradually narrowed from one side (spring 83 side) in the circumferential direction toward the other side. It is formed in a wedge shape, and is formed wider than the outer diameter (roller diameter) of the roller 82 on one side in the circumferential direction, and narrower than the roller diameter on the other side in the circumferential direction.
The roller 82 is disposed in the cam chamber 84 and is urged by a spring 83 in a direction (narrow direction) in which the space of the cam chamber 84 is narrowed.

Next, the operation and effect of the starter 1 will be described.
When the main contact of the motor circuit is closed by the electromagnetic relay 3, the armature 2a is energized from the battery to generate a rotational force on the armature shaft 2b. At this time, as shown in FIG. 4 (b), the reverse rotation prevention clutch 8 rotates the clutch inner 80 provided on the armature shaft 2b in the counterclockwise direction indicated by the arrow in the drawing, so that the roller 82 is spring-loaded. The armature shaft 2b is allowed to rotate by moving in the direction in which the space of the cam chamber 84 is widened while idling 83 and shrinking. That is, when the engine is started, the reverse rotation prevention clutch 8 does not work.
The rotation of the armature shaft 2b is decelerated by the speed reducer 4 and transmitted to the output shaft 5, and further transmitted from the output shaft 5 to the pinion gear 7, and the rotation of the pinion gear 7 is transmitted to the ring gear 37 to crank the engine. To do. The impact generated during the cranking (for example, the impact caused by the ring gear 37 hitting the pinion gear 7) is absorbed by the impact absorbing device. That is, the ring drive 38 and the ring drive 39 rotate relative to each other via the ring space 40, and the rubber damper 41 is bent (compressed and deformed) in the circumferential direction to absorb the impact.

Further, when an excessive shock that cannot be absorbed by the shock absorbing device, for example, an excessive shock occurs due to an erroneous explosion of the engine or a restart immediately before the engine is stopped, the rotating disk 33 of the torque limiter slides against the frictional force. This interrupts the transmission of impact force. Thereby, an excessive impact is not applied to the torque transmission path of the starter 1, and damage due to the impact received from the engine side can be avoided.
When the engine completes explosion and the engine speed exceeds the starter speed, for example, a one-way clutch (not shown) built in the ring gear 37 idles, and torque is generated between the engine crankshaft and the ring gear 37. Therefore, the engine rotation is not transmitted to the pinion gear 7 and the overrun of the armature 2a can be prevented.

  By the way, when reverse rotation occurs in the engine, for example, when the engine rotates backward when the vehicle moves backward due to the crankshaft swinging when the engine stops, or when the engine reverses due to the climb on the climbing road, The one-way clutch built in 37 is engaged. For this reason, the reverse rotation of the engine is transmitted from the ring gear 37 to the pinion gear 7 → the output shaft 5 → the shock absorbing device → the speed reducer 4 → the armature shaft 2b. As shown in FIG. When rotating in the clockwise direction indicated by the middle arrow, the roller 82 moves in the narrow direction of the cam chamber 84 and is locked between the clutch inner 80 and the movable outer portion 81b, thereby preventing the clutch inner 80 from rotating. The As a result, it is possible to prevent the armature shaft 2b from rotating in the direction opposite to that when starting the engine.

  Further, when the reverse rotation prevention clutch 8 is operated when the reverse rotation of the engine is transmitted to the armature shaft 2b, an impact is generated in the torque transmission path of the starter 1. In particular, when the vehicle is stalled, the inertia of the entire vehicle is received by the reverse rotation prevention clutch 8, so that a very large impact is generated. At this time, when a load torque larger than the sliding torque of the movable outer portion 81b with respect to the fixed outer portion 81a of the clutch outer 81 is applied to the armature shaft 2b, the movable outer portion 81b slides (rotates) in the circumferential direction with respect to the fixed outer portion 81a. Therefore, the impact generated by absorbing the load torque can be reduced.

  When the movable outer portion 81b slides relative to the fixed outer portion 81a, both the roller 82 and the clutch inner 80 start to move (rotate), so the armature shaft 2b provided with the clutch inner 80 also rotates. However, although the excessive load torque is applied depending on the set value of the slip torque, it is when it receives an impact with a very high input speed and does not occur for a long time. Will never continue to rotate. That is, the reverse rotation prevention clutch 8 allows the armature 2a to rotate backward instantaneously by sliding the movable outer portion 81b when an excessive load torque is applied to the armature shaft 2b, but the movable outer portion 81b slides. Thus, after the load torque is absorbed, the reverse rotation of the armature 2a can be prevented by the original reverse rotation prevention function.

  Further, the reverse rotation prevention clutch 8 does not need to set the slip torque assuming the maximum friction of the engine because the roller 82 does not idle at the time of engine start and the shock absorbing function does not work. In other words, as shown in FIG. 5, in the conventional friction type torque limiter, the minimum slip torque is determined with a predetermined margin with respect to the maximum friction of the engine. Can not lower the sliding torque. For this reason, even if the excessive impact input from the engine side is reduced by the torque limiter, it is governed by the slip torque of the torque limiter required when starting the engine, so there is a limit to reducing the generated impact. .

On the other hand, in the starter 1 of the present embodiment, the clutch outer 81 of the reverse rotation prevention clutch 8 is provided with an impact absorbing function, so that it can be moved relative to the fixed outer portion 81a without being affected by the torque required when starting the engine. The sliding torque of the outer part 81b can be set arbitrarily. As a result, as shown in FIG. 5, since the slip torque can be set lower than that of the conventional torque limiter, the generated impact can be reduced as compared with the conventional arrow A as shown by the arrow A in the figure.
Further, by reducing the generated impact, each strength component of the starter 1 (for example, the reverse rotation prevention clutch 8, the planetary gear speed reducer 4 and the like) can be reduced in size and weight, and the cost due to the use of a low strength material. Reduction is also possible.
Further, the starter 1 described in the first embodiment includes the internal speed reducer 4, but the shock absorbing function provided to the clutch outer 81 of the reverse rotation prevention clutch 8 is the internal speed reducer (planetary gear speed reducer 4). Therefore, a constant meshing starter that does not have an internal speed reducer can also be provided with an impact absorbing function by using the reverse rotation prevention clutch 8.

Further, the shock absorbing function of the clutch outer 81 can be realized by a simple structure in which the movable outer portion 81b is press-fitted and fitted to the inner periphery of the fixed outer portion 81a, and a press-fit load (a circumferential rotation obtained by press-fitting). The sliding torque can be arbitrarily adjusted according to the fixing force).
Further, by applying a lubricant such as grease to the press-fitted portion between the fixed outer portion 81a and the movable outer portion 81b, the variation in the friction coefficient can be reduced, so that the target value of the sliding torque can be set to be severe (strict). Moreover, since the wear of the press-fit surface can be suppressed by the lubricant, the durability can be improved.

The starter 1 of this embodiment can be used for an engine automatic stop / restart system that automatically controls stop and restart of the engine because the pinion gear 7 is always meshed with the ring gear 37. In a vehicle equipped with this engine automatic stop / restart system, the number of times the engine is started by the starter inevitably increases. For this reason, when a starter that does not have the reverse rotation prevention clutch 8 is employed in the above system, the frequency of reverse rotation of the armature 2a that occurs each time the engine is stopped is greatly increased, which affects the life of the brush 10. Further, when the brush 10 slides on the outer periphery of the commutator 9, the number of times that abnormal noise (sliding noise) is generated increases, which makes the user uncomfortable.
On the other hand, since the starter 1 of the present embodiment can prevent the armature 2a from rotating backward by the reverse rotation prevention clutch 8, the life of the brush 10 can be improved and the discomfort given to the user can be eliminated.

It is sectional drawing of a starter. It is sectional drawing of a reverse rotation prevention clutch and a torque limiter. It is sectional drawing which shows the structure of a reverse rotation prevention clutch. (A) Enlarged sectional view showing a part of the reverse rotation prevention clutch, (b) Operation explanatory diagram of the clutch at the time of starting the engine, (c) Operation explanatory diagram of the clutch when reverse rotation of the engine is inputted. . It is explanatory drawing which shows the relationship between the slipping torque of a reverse rotation prevention clutch, and an engine friction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Starter 2 Motor 2b Armature shaft 4 Reduction gear 5 Output shaft 6 Bearing 7 Pinion gear 8 Reverse rotation prevention clutch 27 Sun gear 28 Internal gear 29 Planetary gear 33 Rotating disk 37 Ring gear 80 Clutch inner 81 Clutch outer 81a Fixed outer part 81b Movable outer Part 82 roller 84 cam chamber

Claims (5)

A motor that generates rotational force on the armature shaft;
An output shaft that rotates when the rotational force of the motor is transmitted;
A pinion gear that is arranged on the outer periphery of the output shaft so as to be relatively rotatable via a bearing, is always meshed with a ring gear on the engine side, and transmits the rotational force generated by the motor to the ring gear;
A reverse rotation preventing clutch that prevents the armature shaft from rotating in a direction opposite to the rotation direction at the time of starting the engine;
This reverse rotation prevention clutch
A clutch inner provided on the armature shaft, a clutch outer disposed concentrically with the clutch inner and forming a wedge-shaped cam chamber between the clutch inner and an outer peripheral surface of the clutch inner, and the cam chamber. And when the reverse rotation of the engine is transmitted to the armature shaft, the roller moves in the narrowing direction of the cam chamber and is locked between the clutch outer and the clutch inner. The starter prevents rotation of the clutch inner and prevents reverse rotation of the armature shaft,
The clutch outer forms a cam chamber between a fixed outer portion that is fixed in a non-rotatable manner and an outer peripheral surface of the clutch inner and is disposed inside the fixed outer portion. A movable outer portion whose rotation is restricted by a predetermined slip torque, reverse rotation input from the engine side is transmitted to the armature shaft, and a load torque larger than the slip torque is applied to the armature shaft. When the movable outer portion slides in the circumferential direction with respect to the fixed outer portion, the starter has a function of absorbing the load torque. The starter according to claim 1,
In the clutch outer, the movable outer portion is press-fitted into an inner circumference of the fixed outer portion, and a fixing force against circumferential rotation obtained by the press-fitting is set as the slip torque. The starter according to claim 2,
A starter, wherein a lubricant is applied to a press-fit portion between the fixed outer portion and the movable outer portion. The starter according to any one of claims 1 to 3,
A decelerator that decelerates the rotation of the motor and transmits it to the output shaft;
A torque limiter that absorbs the excessive torque when the excessive torque is transmitted to the output shaft from the engine side via the pinion gear when the engine is started,
The speed reducer has a sun gear provided on the armature shaft, an annular internal gear arranged concentrically with the sun gear, and a planetary gear meshing with the sun gear and the internal gear, A planetary gear reducer in which the revolving motion of the planetary gear is transmitted to the output shaft;
The torque limiter has a rotating disk that is rotatably engaged with the internal gear and that is restricted in rotation by a frictional force, and exceeds an excessive slip torque of the rotating disk obtained by the frictional force. A starter characterized in that when the torque is applied to the internal gear, the rotating disk absorbs the excessive torque by sliding against the frictional force.   5. The starter according to claim 1, wherein the starter is used in an engine automatic stop / restart system that automatically controls stop and restart of the engine.

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