EP2093415A2

EP2093415A2 - Torque transmission apparatus for transmitting driving torque from starter motor to internal combustion engine

Info

Publication number: EP2093415A2
Application number: EP09001110A
Authority: EP
Inventors: Mitsuhiro Murata
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2008-02-20
Filing date: 2009-01-27
Publication date: 2009-08-26
Also published as: EP2093415A3; JP5377863B2; JP2009197657A

Abstract

In a torque transmission apparatus 1, an oil seal 7 is placed at an outer periphery of a clutch 6 in its diameter direction. The clutch 6 has an outer 6a, an inner 6b, and a link member 6c. A lip part 7a of the oil seal 7 slides on the outer periphery of the outer 6a fixed to a primary rotary body 3. A bearing 4 placed at the inner periphery of the clutch 6 in the diameter direction is a ball bearing with a seal. In particular, a filling ratio of a lubricant with which a filling space formed between the bearing 4 and the oil seal 7 is filled is not more than 60 %. When an engine rotates, this structure suppresses the inner pressure of the oil seal 7 from increasing and a torque loss from increasing. The above structure decreases the fuel consumption of the engine.

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to torque transmission apparatus for transmitting a driving torque from a starter motor to an internal combustion engine. In more detail, the torque transmission apparatus is capable of transmitting the driving torque of the starter motor to a crank shaft of the internal combustion engine through a ring gear equipped with a built-in clutch in order to start the rotating motion of the internal combustion engine.

2. Description of the Related Art

Recently, measurement of engine exhaust gas has been developed. This is one of global warning countermeasure. For example, idling stop systems have been developed and mounted to vehicles in order to stop the operation of an internal combustion engine mounted to a vehicle when the vehicle stops on a street intersection when a traffic signal is red.
Japanese patent laid open publication No. JP 2006-312891 has disclosed the structure of a conventional torque transmission apparatus to be assembled to the idling stop system. The torque transmission apparatus disclosed in JP 2006-312891 is comprised of a flywheel and a one-way clutch. The flywheel is assembled to the crank shaft of the internal combustion engine of a vehicle. The ring gear always engages with a pinion gear of a starter motor.
The one way clutch is comprised of an outer, an inner, and a link member. The link member is comprised of a cam, a sprag, and a roller. The outer is fixed to the flywheel. The inner is mounted to the ring gear. The link member performs and halts the transmission of the driving torque, namely, intermittently transmits the driving torque between the outer and the inner in the one way clutch. When the ring gear is driven to rotate by the driving torque of the starter motor, this driving torque is then transmitted from the inner to the outer through the link member in the one way clutch. Thereby the flywheel starts to rotate. This enables the internal combustion engine to crank up.
On the other hand, when the rotation speed of the flywheel reaches and then exceeds that of the ring gear, the clutch falls into racing, and interrupts the driving torque transmission from the flywheel to the ring gear.
By the way, the conventional torque transmission apparatus having the above structure disclosed in JP 2006-312891 is equipped with an oil seal. The oil seal is placed in the radial direction at the outer periphery of the clutch in order to prevent a lubricant for the clutch leaking. In this structure of the conventional torque transmission apparatus, the clutch and the oil seal are placed close to each other along the axial direction of the clutch. Thus, because the clutch and the oil seal are wrapped together in the axial direction, the torque transmission apparatus has a compact size observed from the axial direction of the torque transmission apparatus. Having the torque transmission apparatus with a compact size is very important from the viewpoint of miniaturizing the placement of the transmission assembly and the internal combustion engine in the vehicle to be changed.
However, in the structure of the conventional torque transmission apparatus in which the oil seal is placed at the outer periphery of the clutch in the conventional torque transmission apparatus described above, the lip part of the oil seal always slides on the outer periphery of the outer while the internal combustion engine rotates, namely, the outer fixed to the flywheel is rotating. This causes a torque loss and decreases the fuel consumption of the internal combustion engine. In particular, during the rotation of the internal combustion engine, a large amount of centrifugal force is applied to the lubricant in the clutch, the pressure of the inside of the seal thereby increases, and as a result, the lip part of the oil seal is forcedly pushed to the outer periphery of the outer. This causes the torque loss of the torque transmission apparatus to increase.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a torque transmission apparatus having an improved structure for transmitting a driving torque from a starter motor to an internal combustion engine. In the structure of the torque transmission apparatus, an oil seal is placed in a radial direction on the outer periphery of a clutch. The torque transmission apparatus according to the present invention is capable of decreasing the magnitude of torque loss while the internal combustion engine rotates.
To achieve the above purpose, the present invention provides a torque transmission apparatus 1 for transmitting a driving torque from a starter motor 9 to an internal combustion engine. In more detail, the torque transmission apparatus 1 transmits the driving torque of the stator motor 9 to a crank shaft 2 of the internal combustion engine in order to start the internal combustion engine 1 to rotate. The torque transmission apparatus 1 has a primary rotary body 3, a secondary rotary body 5, a one way clutch 6, a primary sealing member 7, a secondary sealing member 4, and a lubricant. The primary rotary body 3 is mounted to the crank shaft 2. The secondary rotary body 5 is supported by the primary rotary body 3 through a bearing 4. The secondary rotary body 5 is always engaged with a pinion gear 10 of the starter motor 9. The one way clutch 6 has an outer 6a, an inner 6b, and a link member 6c. The outer 6a is placed at the primary rotary body 3. The inner 6b is placed at the secondary rotary body 5. The link member 6c performs and halts the transmission of the driving torque, namely, intermittently transmits the driving torque between the outer 6a and the inner 6b. The one way clutch 6 is placed between the primary rotary body 3 and the secondary rotary body 5. The one way clutch 6 transmits the driving torque from the primary rotary body 3 to the secondary rotary body 5 when the secondary rotary body 5 rotates by the driving torque of the starter motor 9. The one way clutch 6 interrupts the transmission of the torque from the primary rotary body 3 to the secondary rotary body 5 when the primary rotary body 5 rotates by the internal combustion engine. The primary sealing member 7 is placed at one side of the one way clutch 6. The secondary sealing member 4 is placed at the other side of the clutch. A sealing space formed between the primary sealing member 7 and the secondary sealing member 4 is filled with the lubricant. In the torque transmission apparatus 1 having the above structure, the primary sealing member 7 and the one way clutch 6 are co-located in the axial direction of the torque transmission apparatus 1. The primary sealing member 7 is placed on the outer periphery in the diameter direction of the clutch 6, and slides on the outer circumferential surface of the outer 6b. In particular, a filling ratio of the lubricant in the filling space is not more than 60 %.
In the above structure of the torque transmission apparatus according to the present invention, the oil seal 7 as the primary sealing member and the one way clutch 6 are wrapped in the axial direction of the torque transmission apparatus, and the oil seal 7 is placed at the outer periphery of the one way clutch 6 in the diameter direction of the one way clutch 6. This can provides the torque transmission apparatus 1 with a compact size in the axial direction when compared with the structure of a conventional torque transmission apparatus in which the oil seal is placed adjacent to the clutch in the axial direction of the torque transmission apparatus.
The inventor according to the present invention obtained the experimental results. That is, the inner pressure of the oil seal 7 is increased by applying centrifugal force to the lubricant when the internal combustion engine rotates. As a result, the torque loss is increased by pressing the lip part 7a of the oil seal 7 onto the outer 6a of the clutch 6. According to the experimental results shown in FIG. 3 (will be explained in the embodiment section in detail), the magnitude of the torque loss increases when the filling ratio of the lubricant exceeds 60 %. On the other hand, the magnitude of the torque loss decreases when the filling ratio of the lubricant is not more than 60 %. Thus, setting the filling ratio of the lubricant in the sealing space formed between the oil seal 7 as the primary sealing member and the secondary sealing member 4 to not more than 60 % can decrease the torque loss, and contributes to the fuel consumption efficiency.
In the torque transmission apparatus as another aspect of the present invention, the primary rotary body 3 has a boss part 3a fixed to the crank shaft 2, and the boss part 3a and the inner 6b are wrapped and placed in the axial direction, the bearing 4 as the secondary sealing member is a ball bearing with a seal. The primary sealing member 7 is an oil seal with a lip part which slides on the outer circumferential surface of the outer 6a.
Using the ball bearing with a seal acts as both the bearing 4 and the secondary sealing means can decrease the total number of components which form the torque transmission apparatus, and thereby provide the torque transmission apparatus with a compact size. Placing the ball bearing with a seal between the boss part 3a and the inner 6b which are wrapped in the axial direction can provide the torque transmission apparatus with a compact size observed from the axial direction of the torque transmission apparatus 1.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

FIG.1 is a cross sectional view of a half part of a torque transmission apparatus for transmitting a driving torque to start an internal combustion engine;
FIG. 2 is a cross sectional view of a starter motor and the torque transmission apparatus for transmitting the driving torque from the starter motor to the internal combustion engine; and
FIG. 3 is a graph showing a relationship between a filling ratio of a lubricant and a torque loss ratio.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the various embodiments, like reference characters or numerals designate like or equivalent component parts throughout the several diagrams.

Embodiment

A description will be given of a torque transmission apparatus according to an embodiment of the present invention with reference to FIG. 1 to FIG. 3.
FIG.1 is a cross-sectional view of a half part of a torque transmission apparatus 1 for transmitting the driving torque from a starter motor 9 to an internal combustion engine. FIG. 2 is a cross sectional view of the starter motor 9 and the torque transmission apparatus 1 for transmitting the driving torque from the starter motor 9 to the internal combustion engine.
As shown in FIG. 1, the torque transmission apparatus 1 is comprised of a primary rotary body 3, a secondary rotary body 5, a one way clutch 6, and an oil seal 7, and others. The primary rotary body 3 is fixed to a crank shaft 2 of the internal combustion engine (omitted from the drawings). The secondary rotary body 5 is rotatably supported by the primary rotary body 3 through a bearing 4. The one way clutch 6 is placed between the primary rotary body 3 and the secondary rotary body 5. The oil seal 7 prevents a lubricant (such as grease) for the one way clutch 6 flowing out.
The torque transmission apparatus 1 according to the embodiment is applied to an automatic engine starting/restarting system which automatically controls the internal combustion engine to start and restart. The automatic engine starting/restarting system automatically stops the internal combustion engine when the vehicle stops on a street intersection when a traffic signal is red or the vehicle drives on a traffic jam.
The automatic engine starting/restarting system then automatically restarts the internal combustion engine in response to a predetermined starting operation (for example, when the vehicle driver leaves the brake pedal of the vehicle). Such an automatic engine starting/restarting system is also called to as the "idling stop system" or "economy running system".
The primary rotary body 3 is a flywheel or a drive plate for an automatic transmission (AT) vehicle. A boss part 3a of a ring shape is placed in the diameter direction at the central part of the primary rotary body 3. The boss part 3a is fixed to an end part of the crank shaft 2 through a bolt 8.
The secondary rotary body 5 is a ring gear having teeth formed on the outer periphery thereof. The pinion gear 10 of the starter motor 9 (see FIG. 2) is always engaged with this ring gear.
The inner circumferential surface of the secondary rotary body 5 is engaged in the diameter direction with an inner 6b of the one way clutch 6. The inner 6b and the boss part 3a of the primary rotary body 3 are wrapped together in the axial direction. In other words, the secondary rotary body 5 is placed at the outside of the boss part 3a in the diameter direction through the bearing 4. Because the structure and operation of the stator motor 9 were well known, the explanation thereof is omitted here.
The bearing 4 is composed of an outer ring 4a, an inner ring 4b, and a plurality of balls. Those balls 4c are placed between and rotatably supported by the outer ring 4a and the inner ring 4b. The bearing 4 serves as a seal function. That is, the bearing 4 serves as a second seal means having the sealing function to seal the inner periphery side of the one way clutch 6. The bearing 4 as the second seal means contrasts with the oil seal 7 as the primary sealing member having the function to seal the outer periphery of the one way clutch 6. Thus, the bearing 4 seals one side of the one way clutch 6 and the oil seal 7 seals the other side of the one way clutch 6.
The one way clutch 6 has an outer 6a, an inner 6b, and a link member 6c. The link member 6c is comprised of a cam, a sprag, and a roller.
The outer 6a is pressed and fixed to the primary rotary body 3. In the one way clutch 6, the inner 6b is placed at the inner diameter side of the outer 6a. The inner 6a is mounted to the secondary rotary body 5. The link member 6c performs and halts the transmission of the driving torque, namely, intermittently transmits the driving torque between the outer 6a and the inner 6b in the one way clutch 6.
The oil seal 7 is placed in a concave part formed in the secondary rotary body 5. This concave part is a space formed in the outside of the outer 6a observed in the diameter direction. The oil seal 7 seals one side of the clutch 6. That is, the lip part 7a of the oil seal 7 slides on the outer circumferential surface of the outer 6a. This lip part 7a is made of resin.
By the way, a sealing space into which the clutch 6 is placed is formed between the oil seal 7 and the bearing 4. The sealing space is filled with a lubricant to lubricate the clutch 6 in working. This sealing space corresponds to the sealing space written in the claims according to the present invention.
This sealing space for the clutch 6 is sealed by the oil seal 7 placed at one side (at the outer periphery side) of the clutch 6 and the bearing 4 placed at the other side (at the inner periphery side) of the clutch 6. In the structure of the torque transmission apparatus according to the embodiment of the present invention, it is set so that the filling ratio of the lubricant in the sealing space is not more than 60 % of the entire volume of the sealing space.
A description will now be given of the operation of the torque transmission apparatus 1 according to the embodiment of the present invention.

(a) At the start of the internal combustion engine

When receiving the driving torque transmitted from the starter motor 9, the secondary rotary body 5 starts to rotate, the clutch 6 enters the engagement state in which the outer 6a is engaged with the inner 6b through the link member 6c. The driving torque from the secondary rotary body 5 is propagated to the primary rotary body 3, and the crank shaft 2 in order. This propagation of the driving torque initiates the cranking operation.

(b) After the start of the internal combustion engine

After the cranking operation, the internal combustion engine reaches a usual rotation speed. When the rotation speed of the primary rotary body 3 exceeds that of the secondary rotary body 5, the clutch 6 races, and the driving torque transmitted from the primary rotary body 3 to the secondary rotary body 5 is interrupted.

(Effect of the torque transmission apparatus 1 of the embodiment)

In the structure of the torque transmission apparatus 1 according to the embodiment, the oil seal 7 as a primary sealing means and the clutch 6 are wrapped in the axial direction of the torque transmission apparatus 1. In addition, the oil seal 7 is placed at the outer periphery of the clutch 6 observed from the diameter direction. This arrangement provides the torque transmission apparatus 1 with a compact size in the axial direction when compared with the conventional structure in which the oil seal is placed adjacent to the clutch in the axial direction.
Still further, because of using the ball bearing with a seal as the bearing 4, and because the ball bearing acts as the secondary sealing member written in the claims according to the present invention, it is possible to reduce the number of the components forming the torque transmission apparatus 1. It is further possible to form the torque transmission apparatus 1 with a compact size. Still further, because the bearing 4 is placed between the boss part 3a and the inner 6b which are wrapped in the axial direction, it is possible to provide the torque transmission apparatus 1 with a compact size observed from the axial direction.
In the structure of the torque transmission apparatus 1 according to the embodiment of the present invention, the sealing space is formed between the oil seal 7 and the bearing 4 (with a seal), and is filled with a lubricant to lubricate the clutch 6. This structure increases an inner pressure of the oil seal 7 when the centrifugal force generated by the rotation of the internal combustion engine is applied to the lubricant. This causes increases the torque loss ratio because the lip part 7a is pressed onto the outer circumferential surface of the outer 6a unless the filling ratio of the lubricant is set to not more than 60%. This structural feature of the present invention was obtained based on the following experimental results shown in FIG. 3.
FIG. 3 is a graph showing a relationship between the filling ratio of the lubricant and the torque loss ratio.
The experiment was performed to obtain the relationship between the filling ratio of the lubricant and the torque loss ratio in the torque transmission apparatus 1. As shown in FIG. 3, the experimental result clearly indicates that the torque loss ratio can be decreased as long as the filling ratio of the lubricant in the sealing space is not more than 60 %. Further, when the filling ratio of the lubricant in the sealing space exceeds 60 %, the torque loss ratio is decreased. According to the experimental result, the structure of the torque transmission apparatus 1 according to the present invention uses the filling ratio of not more than 60 % of the lubricant in the sealing space formed between the oil seal 7 and the bearing 4 in the structure of the torque transmission apparatus 1 according to the present invention.
This structure can suppress the inner pressure of the oil seal 7 increasing, and decrease the torque loss ratio while the internal combustion engine rotates, and contribute the fuel consumption improvement.
While specific embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limited to the scope of the present invention which is to be given the full breadth of the following claims and all equivalent thereof.

Claims

A torque transmission apparatus (1) for starting an internal combustion engine, which transmits a driving torque of a stator motor (9) to a crank shaft (2) of the internal combustion engine when the internal combustion engine starts in work, comprising:
a primary rotary body (3) mounted to the crank shaft (2) of the internal combustion engine;

a secondary rotary body (5), that is supported by the primary rotary body (3) through a bearing (4), being always engaged with a pinion gear (10) of the starter motor (9);

a one way clutch (6) comprising: an outer (6a) placed at the primary rotary body (3); an inner (6b) placed at the secondary rotary body (5); and a link member (6c) that intermittently transmits the driving torque transmission between the outer (6a) and the inner (6b), the one way clutch (6) being placed between the primary rotary body (3) and the secondary rotary body (5), transmitting the driving torque from the primary rotary body (3) to the secondary rotary body (5) when the secondary rotary body (5) rotates by the driving torque of the starter motor (9), and interrupting the transmission of the driving torque from the primary rotary body (3) to the secondary rotary body (5) when the primary rotary body (5) rotates by the internal combustion engine;

a primary sealing member (7) placed at one side of the one way clutch (6);

a secondary sealing member (4) placed at the other side of the one way clutch (6); and

a lubricant with which a sealing space formed between the primary sealing member (7) and the secondary sealing member (4) is filled,
wherein the primary sealing member (7) and the clutch (6) are co-located in the axial direction, and the primary sealing member (7) is placed at the outer periphery of the clutch (6) in the diameter direction, and slides on the outer circumferential surface of the outer (6b), and
a filling ratio of the lubricant in the filling space is not more than 60 %.
The torque transmission apparatus as claimed in claim 1, wherein the primary rotary body (3) has a boss part (3a) fixed to the crank shaft (2), and the boss part (3a) and the inner (6b) are wrapped and placed in the axial direction, the bearing (4) as the secondary sealing member is a ball bearing with a seal, and
the primary sealing member (7) is an oil seal with a lip part made of resin which slides on the outer circumferential surface of the outer (6a).
The torque transmission apparatus as claimed in claim 1 or 2,
wherein the link member (6c) of the clutch (6) is comprised of a cam, a sprag, and a roller.