Patent Application
20050046193
1. Field of the Invention
The present invention relates to a starter for cranking an internal combustion engine, and more particularly to a starter having a member for restricting rotation of a pinion gear for establishing engagement between the pinion gear and a ring gear of the engine.
2. Description of Related Art
Examples of this type of starter are disclosed in JP-A-9-217672 and JP-A-10-18950. The starter has a pinion unit spline-coupled to an output shaft that is driven by an electric motor and a pinion-rotation-restricting member that engages with the pinion unit to restrict rotation thereof. When the electric motor rotates, the pinion unit is shifted on the output shaft toward a ring gear of the engine while rotation of the pinion unit is restricted. After the engagement between the pinion unit and the ring gear is established, the pinion unit is rotated at a full speed to thereby crank up the engine.
In this starter, a magnetic switch for driving a crank bar that in turn drives the pinion-rotation-restricting member is positioned at an axial end opposite to the other axial end where the pinion unit is positioned. Therefore, it is unavoidable to make the crank bar long so that it extends one axial end to the other axial end of the starter. In addition, since the crank bar has a crank-shape, it is not easy to install the crank bar in the starter in an assembling process. In particular, it is difficult to assemble the starter from its front housing side by stacking components one by one. Accordingly, the process of assembling the starter has been time-consuming and costly.
Further, it has been difficult in the conventional starter to keep a clearance or a gap small between the crank bar and a component to which the crank bar is connected. This is because certain clearances have to be provided in various components to allow the crank-shaped bar to be mounted in the starter. If the gap or clearance between the crank bar and the magnetic switch is large, movement of the magnetic switch is not efficiently transferred to the crank bar. To decrease the gap or clearance, both ends of the crank bar have to be bent precisely. This also increases the manufacturing costs.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved starter which can be easily assembled using a crank bar manufactured at a low cost.
The starter for cranking an internal combustion engine is composed of: an electric motor; an output shaft driven by the electric motor; a pinion unit spline-coupled to the output shaft; a pinion-rotation-restricting member; a magnetic switch for supplying electric current to the electric motor; and a crank bar connecting the magnetic switch to the pinion-rotation-restricting member to bring the pinion-rotation-restricting member into engagement with the pinion unit.
Upon closing a key-switch, the magnetic switch is energized, and rotation of the pinion unit is restricted by the pinion-rotation-restricting member. Then, the electric motor is slowly rotated to bring the pinion unit into engagement with a ring gear of the engine while rotation of the pinion unit is restricted. After the engagement between the pinion unit and the ring gear is established, the motor is rotated at a full speed to there by crank up the engine. After the engine is cranked up, the key-switch is opened to thereby de-energize the magnetic switch and to return the pinion unit to its initial position.
The crank bar connecting the magnetic switch and the pinion-rotation-restricting member is composed of a driving portion coupled to the pinion-rotation-restricting member, a coupling portion coupled to the magnetic switch, and a straight portion connecting the driving portion and the coupling portion. The straight portion and the driving portion are integrally formed (as a first part), and the coupling portion (as a second part) is formed separately from the first part. The first part and the second part are assembled into the starter and correctly positioned therein, and then the coupling portion is firmly connected to the straight portion, so that there exists no contacting gap in the direction in which the crank bar is driven by the magnetic switch.
Since the crank bar is composed of two parts when it is assembled into the starter, a process of assembling the starter components including the crank bar can be easily carried out. After the coupling portion and the driving portion are correctly positioned to make close contact with respective components, the coupling portion is firmly connected to the straight portion by fastening a nut, or the like. Therefore, no contact gaps are made in the operating direction, and movement of the magnetic switch is effectively transmitted to the pinion-rotation-restricting member via the crank bar.
The crank bar may be separated in other ways. That is, it may be separated into two parts, a first part including the coupling portion and the straight portion and a second part consisting of the driving portion. Alternatively, the crank bar may be separated into three portions, the coupling portion, the straight portion and the driving portion. After all of the separated parts or portions are correctly positioned in the starter, they are firmly connected to one another without forming contacting gaps in the direction in which the crank bar is driven by the magnetic switch.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.
A first embodiment of the present invention will be described with reference to
The electric motor 2 is a known type of motor that is composed of a stator 8 for supplying a magnetic field and an armature 10 rotatably disposed in the stator 8, the armature 10 having a commutator 9 through which electric current is supplied to the armature 10 via brushes 11. The electric motor 2 is held between a front housing 12 and the end cover 13. The stator 8 is composed of a cylindrical yoke 8a and permanent magnets 8b disposed inside the yoke 8a. The armature 10 includes an armature core 10b around which an armature coil 10c is wound, an armature shaft 10a press-fitted into a center hole of the armature core 10b. Coil ends of the armature coil 10c bent on a rear axial end surface of the armature core 10b are utilized as the commutator 9. Brushes 11 slidably contact on the surface of the commutator 9 in the axial direction of the armature 10.
The output shaft 3 is coaxially disposed with the armature shaft 10a at the front side of the starter 1 and is rotatably supported by a bearing 14 held in the front housing 12 and another bearing 15 held in a center case 16 that is disposed inside the front housing 12. A known type of a planetary gear speed reduction mechanism and a one-way clutch are interposed between the armature shaft 10a and the output shaft 3.
The planetary gear speed reduction mechanism is composed of a sun gear formed at the front end of the armature shaft 10a and planetary gears 17 engaging with the sun gear. Each planetary gear 17 rotates around a gear shaft 17a, and all the planetary gears orbit around the sun gear. The one-way clutch is composed of a clutch outer 18 to which the gear shafts 17a are fixed, a clutch inner 19 formed integrally with the output shaft 3, and clutch rollers 20 disposed between the clutch outer 18 and the clutch inner 19. The clutch outer 18 rotates together with the orbital rotation of the planetary gears 17, and transmits a rotational torque of the armature 10 to the clutch inner 19 via the rollers 20. Thus, the rotation of the armature 10, speed of which is reduced by the planetary gear reduction mechanism, is transmitted to the output shaft 3. Transmission of the rotational torque from the output shaft 3 to the armature 10 is interrupted by the one-way clutch.
The pinion unit 4 is composed of a pinion gear 4b and a flange 21 formed at a rear side of the pinion gear 4b. The flange 21 has a diameter larger than that of the pinion gear 4b, and a series of depressions 21a are formed on the outer periphery of the flange 21. A female spline 4a is formed in the inner bore of the pinion unit 4, and a male spline 3a is formed on the outer periphery of the output shaft 3. Both splines 3a and 4a are coupled to each other, and thereby the pinion unit 4 is spline-coupled to the output shaft 3 so that the pinion unit 4 slidably moves on the output shaft 3 in the axial direction while the output shaft 3 rotates and rotation of the pinion unit 4 is restricted. The pinion unit 4 is biased toward the rear side by a pinion spring 28 disposed between the front end of the front housing 12 and the pinion unit 4.
A thrust washer 22 are positioned at the rear side of the pinion unit 4 so that the thrust washer 22 freely rotates relative to the pinion unit 4. As shown in
The pinion-rotation-restricting member 5 is made of a metallic bar wound in a coil shape that includes a first end 5b and a second end 5a, both being bent at right angle toward the front side of the starter 1. The pinion-rotation-restricting member 5 is disposed in a space between the plate 25 and the center case 16 and biased by a return spring 29 in X-direction shown in
The structure of the magnetic switch 7 will be described with reference to
As shown in
The auxiliary switch “B” is connected in parallel to the main switch “A” as shown in
As shown in
As shown in
The straight portion 6a and the coupling portion 6c can be connected in various manners other than that shown in
The coupling portion 6c tends to be bent or distorted when it is pulled by the plunger 33. To prevent such bending or distortion, a cross-sectional shape of the coupling portion 6c is made in a shape that is difficult to be distorted in the direction pulled by the plunger 33. For example, the cross-sectional shape is made in a rectangular shape having long sides located in the direction of the pulling force. The end of the coupling portion 6c contacts a contacting surface 46a formed in the hook 46, as shown in
The crank bar 6 is assembled to the starter 1, so that gaps do not exist in the driving direction between the driving portion 6b and the first end 5b of the pinion-rotation-restricting member 5 and between the coupling portion 6c and the hook 46 of the plunger 33. This is because the driving force of the plunger 33 is not effectively transferred to the pinion-rotation-restricting member 5 through the crank bar 6 if there are gaps at contacting portions. To eliminate the contacting gaps, the crank bar 6 is assembled to the starter 1 in the following manner. First, the straight portion 6a is held by the pair of bearings 45. Then, the driving portion 6b is positioned to abut the first end 5b of the pinion-rotation-restricting member 5 which is pushed upward by the return spring 29 to the position shown in
Operation of the starter 1 described above will be explained below. Upon closing the key-switch 30, electric current is supplied to the coil 32 of the magnetic switch 7. The plunger 33 disposed inside the coil 32 is moved upward (in
On the other hand, the auxiliary switch B is closed according to the movement of the plunger 33. Electric current, an amount of which is limited by the resistor 41, is supplied to the armature 10. The armature 10 slowly rotates the output shaft 3, while rotation of the pinion unit 4 is restricted. The pinion unit 4 helical-coupled to the output shaft 3 is pushed forward on the output shaft 3 toward the ring gear R of the engine. Thus, the pinion gear 4b engages with the ring gear R.
When the engagement between the pinion gear 4b and the ring gear R is established, the second end 5a of the pinion-rotation-restricting member 5 is disengaged with the depression 21a and is positioned behind the swing ring 24, releasing the pinion unit 4 from restriction. At the same time, the pinion unit 4 is prevented from moving backward (toward the rear side of the starter 1) by the swing ring 24. Then, the main switch A is closed, thereby supplying a full current to the armature 10. The pinion gear 4b is rotated by the armature 10 at a high speed, while being engaged with the ring gear R. Thus, the engine is cranked up.
After the engine is cranked up, the key-switch 30 is opened, and the current supply to the coil 32 is terminated. The magnetic force in the coil 32 disappears, and the plunger 33 is returned to its initial position (the position shown in
Advantages attained in the first embodiment are as follows. Since the crank bar 6 is separated into two parts, the first part and the second part, the crank bar 6 is easily assembled to the starter 1, avoiding interference with other components. This makes it possible to assemble the starter 1 from one side. For example, the front housing 12 may be placed at the bottom most position, and all the components may be stacked one by one from the front side of the starter 1. In this manner, the assembling process can be speeded up.
The driving portion 6b of the crank bar 6 is positioned to closely contact the first end 5b of the pinion-rotation-restricting member 5, and the coupling portion 6c of the crank bar 6 is positioned so that it closely contacts the contacting surface 46a of the plunger 33. While maintaining those close contacts, the straight portion 6a and the coupling portion 6c is firmly connected to each other. In other words, the first part including the straight portion 6a and the driving portion 6b and the second part consisting of the coupling portion 6c are firmly connected to each other, while eliminating the contacting gaps in the direction in which the crank bar 6 is driven. Therefore, the movement of the plunger 33 is effectively transmitted to the pinion-rotation-restricting member 5 via the crank bar 6.
Since the crank bar 6 is separated into the first part and the second part, two parts can be made of respectively different materials suitable to the respective functions. For example, the first part may be made of S35C and the second part may be made of SPCC. The cross-sectional shape of both parts can be made in respectively different shapes. For example, the second part constituting the coupling portion 6c may be formed in a rectangular cross-section so that the coupling portion 6c is not easily distorted by the pulling force of the plunger 33. The first part including the straight portion 6a may be formed in a round cross-section so that the straight portion 6a is not easily twisted by a rotational force.
Since one end of the coupling portion 6c slidably engages with the hook 46, the coupling portion 6c has to be strong against abrasion. Accordingly, the coupling portion 6c is hardened by heat-treatment such as carbonitriding. Further, the first part and the second part of the crank bar 6 are connected to each other after they are assembled or coupled to other components. Therefore, dimensional fluctuations of the components contacting the crank bar 6 can be absorbed in the process of connecting the first part and the second part. This means that a high level of precision in component dimensions and assembling is not required, and therefore the manufacturing costs of the starter can be made lower.
A second embodiment of the present invention will be described with reference to
A third embodiment of the present invention will be described with reference to
While the present invention has been shown and described with reference to the foregoing preferred embodiments, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-307388 | Aug 2003 | JP | national |
This application is based upon and claims benefit of priority of Japanese Patent Application No. 2003-307388 filed on Aug. 29, 2003, the content of which is incorporated herein by reference.
