192 clutches and power-stop control – Clutches – Automatic
Reexamination Certificate
2000-03-14
2001-06-26
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Clutches
Automatic
C192S222000, C074S339000
Reexamination Certificate
active
06250445
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an inertia brake for a vehicle transmission. More specifically, the present invention relates to an inertia brake for a vehicle transmission where a ball ramp actuator is used to load a clutch pack according to a control signal.
DESCRIPTION OF THE PRIOR ART
Transmissions that have their shifting accomplished using actuators controlled by a microprocessor in response to a driver request and various sensor inputs have been developed and are just now entering the marketplace. Sophisticated electronic transmission controls are being used to control shift actuators that act to shift a gear change transmission independent of the driver. When a transmission countershaft and gear assembly are accelerated with the engine, a shift requires the shaft to be released usually by release of a master clutch. Shifting of such a multiple speed gear transmission without synchronizers requires that the speeds of the gears that are to be meshed be matched so that a smooth clutch tooth engagement can take place. For example, in order to upshift, a gear on a spinning shaft that exceeds the desired mesh speed (synchronous speed) must be allowed to slow before the gear shift can be effectuated. While the shaft is slowing, there is no driveline link between the engine and the transmission. If the vehicle is on an upgrade, especially when pulling a loaded trailer, disconnection of the transmission from the engine allows the vehicle to rapidly slow. Thus, while waiting for the transmission gear shaft to slow to synchronous speed, the vehicle itself slows enough that the gear ratio originally selected for the shift is no longer appropriate.
The next shift must then be calculated and selected by the electronic control package. Once again, as the electronic controller waits for the gear shaft to slow to synchronous, the vehicle continues to rapidly decelerate until the second selected downshift is no longer appropriate. Eventually, the vehicle may come to a stop without a successful upshift being accomplished. Problems in quickly executing a shift due to the length of time required for a transmission gear shaft to decelerate to synchronous speed with the engine results in operational problems as heretofore described.
To date, various traditional type braking devices have been used to reduce the rotational speed of a spinning transmission shaft. For example, shoe type brakes and disc clutches using springs for loading of a clutch pack have been used. The inertia brake devices can be connected to any shaft that is connected to rotate with the input shaft of the transmission including one or more countershafts. U.S. Pat. No. 5,528,950 entitled “Transmission Inertia Brake With Ball Ramp Actuator”, assigned to the assignee of the present invention, the disclosure of which is incorporated herein by reference, discloses using a ball ramp actuator to load a clutch pack.
In a transmission inertia brake, such as the inertia brake disclosed in U.S. Pat. No. 5,528,950 oil is provided to the clutch pack for cooling. Insufficient oil in the clutch pack can cause excess heat which may result in premature wear of friction material. Therefore, there exists a need to provide a transmission inertia brake that assures an adequate oil supply will be provided to the clutch pack.
SUMMARY OF THE INVENTION
The present invention provides for the braking and subsequent slowing of the rotation of a selected transmission shaft in a gear change transmission by means of an inertia brake. The inertia-brake of the present invention has a clutch pack comprised of a plurality of clutch friction pads which are clamped together by means of a ball ramp actuator.
The degree of activation of the ball ramp actuator and hence the axial loading on the clutch pack, is controlled by an electrical coil which acts to electromagnetically pull an armature into frictional contact with the end plate thereby providing a braking torque to the control ring of the ball ramp actuator. The ball ramp actuator then expands axially applying a braking force to the control ring which causes the clamping force to be applied to the clutch pack of the ball ramp actuator.
A detailed disclosure of the construction and operation of a ball ramp actuator device can be found in U.S. Pat. Nos. 2,091,270; 2,605,877; 2,649,941; 3,000,479 and 5,372,106, the disclosures of which are hereby incorporated by reference. The response time of the ball ramp actuator is quite rapid and the actuator has the unique characteristic of generating a very high axial force as compared to the braking force applied to the control ring by the electromagnetic action of the coil, typically in a ratio of over 50:1.
The clutch pack is made up of a plurality of clutch stationary plates grounded to a housing through a bolted hub and a similar number of clutch driven plates rotating with a shaft of the transmission which are compressed together upon energization of a ball ramp mechanism to apply a rotational retarding torque to the spinning transmission shaft to facilitate rapid gear changes in the transmission.
The inertia brake of the present invention can be applied to any rotating shaft in the transmission that requires reduction in its rotating speed to effectuate an event such as a gear ratio change. Thus, application of the inertia brake to the transmission input shaft and/or counter shaft or even to a power take off gear would be possible to assist in rapid gear ratio changes.
The use of the present invention would allow a transmission gear change event to be completed more rapidly and more reliably especially when sophisticated automatic electronic controls are utilized to perform the shift sequence including activation of the inertia brake. The transmission shifting controller cannot select the correct gear when the vehicle is on a steep grade if the transmission cannot be synchronized quickly to complete an upshift. In fact, the vehicle may decelerate so quickly that the transmission cannot be shifted into a correct gear and thus the vehicle will come to a complete stop or begin rolling in a rearward direction due to the inability to successfully shift the transmission after synchronization due to the inertia of the engine, shafts and gearsets within the transmission. The present invention allows the engine and the transmission shafts to be quickly slowed and brought into synchronization so that a shift can be quickly and reliably completed. The ball ramp actuator of the present invention can be used to axially load the clutch pack and provides a device with a more rapid response with low energy consumption and reduce packing size for the forces created as compared to prior art devices.
The inertia brake is bolted to the case of the transmission such that a transmission gear meshes with a gear section of a one-piece drive assembly in the inertia brake. The drive assembly consists of the gear section, an extension section, a clutch section and a bearing section. The one-piece construction lowers costs and makes for a more robust component.
To prevent inadvertent activation of the ball ramp mechanism due to oil drag on the control ring, an isolator assembly comprised of two thrust bearings each of which contact a thrust plate which is nonrotatably linked to the drive assembly. The first thrust bearing reacts against the inertia brake housing through an end plate while the second thrust bearing reacts against the control ring.
One provision of the present invention is to provide a compact, rapid response inertia brake for slowing a rotating transmission shaft.
Another provision of the present invention is to provide a compact, rapid response inertia brake for slowing a rotating transmission shaft utilizing a ball ramp actuator to load a clutch pack.
Another provision of the present invention is to provide a compact, rapid response inertia brake for slowing a rotating transmission shaft utilizing a ball ramp actuator to load a plurality of friction plates which are connected to rotate with the transmission shaft and others are connected to grou
Eaton Corporation
Gordon Howard D.
Marmor Charles A
Musial, II Mitchell M.
Rodriguez Saul
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