Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-12-05
2003-10-07
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C290S03800C, C074S00700R
Reexamination Certificate
active
06630760
ABSTRACT:
DESCRIPTION OF THE INVENTION
1. Field of the Invention
This invention relates to a starter motor assembly for starting an engine and, more particularly, to a starter motor assembly that has a return spring spaced from a pinion assembly of the starter motor assembly. This application is being filed concurrently with U.S. patent application Ser. No. 10/022,166, entitled Engagement and Disengagement Mechanism for a Coaxial Starter Motor Assembly, with inventors David A. Fulton and James D. Stuber, and assigned to Delco Remy America, Inc.
2. Background of the Invention
Starter motor assemblies to assist in starting engines, such as engines in vehicles, are well known. The conventional starter motor assembly broadly includes an electrical motor and a drive mechanism, which generally includes a mechanism for engaging and disengaging a pinion-type gear with an engine flywheel. The electrical motor is energized by a battery upon the closing of an ignition switch. The drive mechanism transmits the torque of the electrical motor through various components to the engine flywheel, thereby cranking the engine until the engine starts.
In greater detail, the closing of the ignition switch (typically by turning a key) energizes a solenoid with low current. Energization of the solenoid moves a metal solenoid shaft or plunger in an axial direction. The movement of the solenoid plunger closes electrical contacts, thereby applying full power to the electrical motor. The movement of the solenoid plunger also biases a pinion-type gear into engagement with a ring gear of the engine flywheel. Once the vehicle engine is started, the operator of the vehicle will open the ignition switch. The solenoid is thus turned off (i.e., deenergized), but the electrical contacts are still closed. To prevent run-on of the electrical motor, and subsequent damage, the engagement and disengagement mechanism must be designed to break the electrical contacts and disengage the pinion-type gear from the engine flywheel.
Starter motors assemblies can be either “biaxial” or “coaxial.” These terms relate to the location of the solenoid and solenoid plunger with respect to the armature shaft of the electrical motor. In a biaxial starter motor, the solenoid and the solenoid plunger are attached to the motor casing, with the solenoid plunger spaced away from and generally parallel to the armature shaft. In a coaxial starter motor, the solenoid is typically placed in the motor casing so that the solenoid plunger is aligned in the same axis with the armature shaft. The coaxial assembly is considered to be more compact and universally adaptable than the biaxial assembly. The present invention is directed to a coaxial assembly.
Once the electrical contacts are closed and full power is applied from the battery to the electrical motor, the motor's armature shaft subsequently rotates at a high speed. A planetary gear assembly, coupled to the armature shaft, reduces the speed of rotation of the armature shaft. The planetary gear assembly includes a drive shaft that rotates at that reduced speed. The end of the drive shaft opposite the planetary gear assembly is coupled with a pinion, preferably by a pinion shaft. Thus, the pinion rotates due to the rotation of the planetary gear drive shaft, which in turn rotates (again, at a reduced speed) due to the rotation of the electrical motor armature shaft.
Starter motor assemblies typically include a one-way clutch that is utilized to allow the planetary gear drive shaft to rotate at higher speeds and/or in the opposite direction from the cranking of the engine and to ensure that these higher rotational speeds or opposite directional velocities are not transmitted to the electrical motor armature shaft. In coaxial starter motor assemblies, the clutch is sometimes built around a ring gear positioned between the planetary gear drive shaft and the electrical motor armature shaft.
As stated above, energization of the solenoid also moves the solenoid plunger in the axial direction to move the pinion into engagement with the engine flywheel. In coaxial starter motor assemblies, typically the plunger is coupled to the pinion such that the movement of the plunger in turn moves the pinion in that same axial direction.
The pinion includes a plurality of gear teeth on its external surface for engagement with the engine flywheel. Thus, when the pinion is biased toward engagement of the flywheel and is rotating, the engagement of the pinion with the ring gear of the flywheel in turn causes the flywheel to rotate, thereby cranking the vehicle engine.
For the energization of the solenoid assembly to move the solenoid plunger and hold the plunger for pinion-flywheel engagement, solenoid assemblies typically utilize two coils, a pull-in coil and a hold-in coil. In particular, both coils energize the plunger of the solenoid assembly to bias the plunger in the axial direction for engagement with the engine flywheel. The hold-in coil then holds the plunger in place to hold the pinion in the engagement position with the ring gear of the engine flywheel.
After the operator of the vehicle opens the ignition switch, which deenergizes the solenoid assembly, the magnetic field that caused the solenoid plunger to move decreases and at some point is overcome by a return spring. In particular, the return spring continually pushes against the pinion away from engagement with the engine flywheel. However, it is only at those times when the force of the return spring is greater than the magnetic field generated by the solenoid biasing the plunger toward the flywheel, as well as an axial thrust force, that the pinion is moved away from engagement from the flywheel.
Conventional return springs often contact the pinion or some part rigidly connected with the pinion, such as the pinion shaft or the drive shaft, in order to exert a force on the pinion to bias the pinion away from the engine flywheel. For example, U.S. Pat. No. 6,109,122, issued to Bori et al. (“the Bori et al. patent”), and assigned to Delco Remy International, discloses a pinion shaft that includes a pinion spring surrounding it, with a pinion engaging one end of the pinion shaft. U.S. Pat. No. 4,924,717, issued to Aimo, discloses a spring fitted around an appendage of the pinion. U.S. Pat. No. 4,838,100, issued to Tanaka, discloses a spring that surrounds the pinion shaft between a bearing, which is rigidly fitted on the inner wall of tubular inner contact member in which the pinion shaft is disposed, and a retaining ring, which is secured to the periphery of the rear end portion of the pinion shaft. Similarly, U.S. Pat. No. 4,852,417, issued to Tanaka, discloses that the pinion shaft is returned by the action of a spring that is provided around the rear end of the pinion shaft.
Thus, the return springs discussed above will be in constant contact with the pinion or the pinion shaft and, thus, will be pushing against a part that is rotating. In some instances, the contact between the return spring and the pinion or the pinion shaft causes the return spring to rotate with the pinion or the pinion shaft as well.
Starter motor assemblies having return springs that contact the pinion or the pinion shaft suffer from several disadvantages. In particular, one disadvantage is the wear on the return spring due to the constant contact and/or rotation with the pinion or the pinion shaft. In addition, the rotation of the return spring may occur at high speeds, which can result in breakage of the spring.
SUMMARY OF THE INVENTION
The present invention is directed to a starter motor assembly having a housing. An electrical motor is provided in the housing having a rotatable armature shaft. A rotatable drive shaft is provided that is engageably linked with the armature shaft. A pinion assembly is provided in the housing that is engageable at one end with the drive shaft. The pinion assembly includes a pinion at the other end engageable with a flywheel of an engine. A solenoid assembly is provided in the housing for selectively energizing the electrical motor, wherein the
Fulton David A.
Stuber James D.
Delco Remy America, Inc.
Jones Judson H.
Ramirez Nestor
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