Driveline torque reducer

A vehicular powertrain system includes a prime mover having an output, a multi-ratio transmission having an input, and a torque reduction coupling system coupling the prime mover output and the multi-ratio transmission input. The exemplary torque reduction coupling system includes a clutch and a planetary gear set selectively coupling the prime mover output to the multi-ratio transmission input. The exemplary planetary gear set includes one components of the planetary gear set being selectively coupled to the clutch.

BACKGROUND

The present system and method relate generally to vehicular drivelines. More specifically, the present system and method relate to reducing the torque transferred from an engine to a transmission portion of a vehicular driveline.

Automobile manufacturers are constantly working to improve fuel efficiency in motor vehicles. Improvements in fuel efficiency for larger vehicles, such as vehicles that incorporate diesel or other large engines, often translate to a reduction in the engine speed. Consequently, recent developments in the design of vehicular drivelines for larger vehicles have resulted in drivelines exhibiting relatively low engine speeds.

While a reduction in engine speed does increase fuel efficiency in larger vehicles, the decrease in engine speed takes a toll on driveline components. For example, a reduction in engine speed results in a corresponding increase in torque transferred through the driveline. Prior art powertrain systems were not sized to handle the maximum torque loading that often occurs at low-speed operation. Specifically, the effective life of transmissions associated with traditional powertrain systems is reduced as a result of the lower engine speeds. Consequently, current drivelines for larger vehicles are often limited in horsepower output by the amount of torque that can be handled by the powertrain transmission. Additionally, the increase in torque provided by the engines operating at lower speeds increased the amount of torque absorbed by the powertrain clutches during shift events. That is, with an increase in powertrain torque, engagement of a powertrain clutch meant transferring an increased amount of torque to the clutch, causing increased wear and lower effective life.

SUMMARY

A vehicular powertrain system includes a prime mover having an output, a multi-ratio transmission having an input, and a torque reduction coupling system coupling the prime mover output and the multi-ratio transmission input. The exemplary torque reduction coupling system includes a clutch and a planetary gear set selectively coupling the prime mover output to the multi-ratio transmission input. The exemplary planetary gear set includes a gear selectively coupled to the clutch.

An exemplary method of operating a vehicular powertrain system includes selecting a first prime mover having an output, providing a multi-ratio transmission having an input, incorporating a torque reduction coupling system coupling the prime mover output and the multi-ratio transmission input, and disengaging the clutch in preparation of a shift event. The torque reduction coupling system includes a clutch and a planetary gear set configured to selectively couple the prime mover output to the multi-ratio transmission input, the planetary gear set including a gear selectively coupled to the clutch.

DETAILED DESCRIPTION

Referring toFIG. 1, a multiple ratio powertrain system20is shown in accordance with an embodiment of the present system and method. In the illustrated embodiment, powertrain system20includes a prime mover22, such as a spark-ignited or compression-ignited internal combustion engine coupled to a multi-ratio transmission24, which is subsequently coupled to an axle26. Additionally, as illustrated inFIG. 1, a torque reduction coupling system28is disposed between the prime mover22and the multi-ratio transmission24.FIG. 1further illustrates an electronic control unit30, as well as an engine controller32, a torque reduction coupling system controller34, and a transmission controller36operatively coupled to corresponding components of the powertrain system20. Further details of the exemplary multiple ratio powertrain system20illustrated inFIG. 1are provided below.

As illustrated inFIG. 1, the exemplary powertrain system20may include an electronic control unit (ECU)30for controlling operation of the prime mover22, the torque reduction coupling system28, and the multi-ratio transmission24. In one exemplary configuration, the ECU30includes a programmable digital computer that is configured to receive various input signals that include, without limitation, the operating speed of the prime mover22, transmission input speed, selected transmission ratio, transmission output speed, and vehicle speed.

The ECU30processes these signals according to logic rules to control operation of the powertrain system20. For example, ECU30may be programmed to deliver fuel to the prime mover22when the prime mover functions as an internal combustion engine. To support this control, each of the prime mover22, the torque reduction coupling system28, and the multi-ratio transmission24may include its own controller32,34, and36, respectively. However, it will be appreciated that the present system and method are not limited to any particular type or configuration of ECU30, controllers32,34, and36, or to any specific control logic for governing operation of the multiple ratio powertrain system20.

Continuing withFIG. 1, the prime mover22may be any fuel controlled engine capable of providing kinetic energy in the form of rotational movement (“rotational energy”) to the multi-ratio transmission24. According to one exemplary embodiment, the prime mover22is a fuel-controlled internal combustion engine such as a well-known diesel engine or the like. Alternatively, the prime mover22may be an electric or pneumatic motor.

The multi-ratio transmission24that is configured to receive rotational energy from the prime mover22may include a number of interchangeable gear ratios, as found in any number of change-gear transmissions known in the art. Alternatively, the multi-ratio transmission24may include a less traditional power transmission system, such as a continuously variable transmission (“CVT”). As shown inFIG. 1, the output of the multi-ratio transmission24drives the axle of the powertrain system20. The axle26of the multiple ratio powertrain system20may include independent gearing that may subsequently be used to modify the rotational velocity of the transmission output.

As shown inFIG. 1, the torque reduction coupling system28is disposed between, and rotatably couples the prime mover22and the multi-ratio transmission24. According to the present exemplary embodiment, the torque reduction coupling system28includes a clutch and is configured to selectively provide the rotational energy from the prime mover22to the multi-ratio transmission24. Further, the present torque reduction coupling system28is configured to reduce the torque load on the components of the multiple ratio powertrain system20, thereby enhancing the life of both the clutch and the multi-ratio transmission.

With reference toFIGS. 2A,2B, and3of the accompanying drawings, the components and function of the torque reduction coupling system28will be described in greater detail. According to one exemplary embodiment illustrated inFIG. 2A, the multi-ratio transmission24is coupled to the output of the prime mover22by the torque reduction coupling system28. For the sake of illustration, the prime mover22is shown as an internal combustion engine inFIGS. 2A and 2B, which generally includes a flywheel42and a first shaft40coupled thereto. Similarly, the multi-ratio transmission24includes a transmission input shaft44.

As shown inFIG. 2A, the torque reduction coupling system28includes an input in the form of the first shaft40that is concentrically disposed within a second shaft41such that both shafts may independently rotate without interference. Both the first shaft40and the second shaft41are coupled to a planetary gear set50. The exemplary planetary gear set50illustrated inFIG. 2Ais configured to selectively couple the first shaft40and the second shaft41to the transmission input shaft44. According to the exemplary embodiment illustrated inFIG. 2A, the first shaft terminates with a plurality of overdrive planetary gears62that form a part of the planetary gear set50. Additionally, the sun gear60component of the planetary gear set50is formed on a first portion of the second shaft41. The ring gear48is coupled to the transmission input shaft44that leads to the multi-ratio transmission24.

According to the exemplary embodiment illustrated inFIG. 2A, the second shaft41includes a sun gear60of the planetary gear set50formed thereon for rotation therewith. The outer surface of the sun gear60is meshed with the planet gears62that are rotatably coupled to the first shaft40and the flywheel42. Additionally, as illustrated inFIG. 2A, a ring gear48is meshed with the outer surface of the planetary gears62to complete the planetary gear set50. The ring gear48is coupled to the transmission input shaft44that leads to the multi-ratio transmission24of the present exemplary multi-ratio transmission24. As noted previously, the multi-ratio transmission24may include a number of interchangeable gear ratios, such as a change-gear transmission or a continuously variable transmission.

Continuing withFIG. 2A, the second shaft41is coupled to a clutch system55through one or more clutch flanges64that are formed on a second portion of the second shaft41. According to one exemplary embodiment, the clutch flanges64are configured to interact with a clutch body68and clutch face74of a clutch system55, as will be described in further detail below.

The clutch system55that is coupled to the second shaft41, and consequently to the sun gear60of the planetary gear set50may be any number of clutches currently known in the art such as a hydraulically or electrically operated friction clutch. As used in the present specification, and in the appended claims, the term “engaged,” when mentioned with respect to a clutch, is meant to be understood as resulting in a single or bidirectional clutching action. Similarly, operation in a “disengaged” mode is meant to be understood as permitting freewheeling of the second shaft41or other elements in one or both rotational directions. As shown inFIG. 2A, the clutch is illustrated as having a clutch actuator70that is manipulated to engage and disengage the clutch system55. The clutch actuator70is coupled to a clutch face74that creates interference between the clutch flanges64, the clutch face74, and the grounded clutch body68when the clutch actuator70is actuated. While the clutch actuator70is illustrated as a manually actuated rod and lever configuration, the clutch actuator may be any number of electric or pneumatic actuators. As shown, a biasing agent72, such as a spring, is disposed adjacent to the clutch face74causing it to naturally exist in an engaged state until actuation occurs.

Additionally, as illustrated inFIG. 2A, a clutch brake80is coupled to the transmission input shaft44. The clutch brake80may be any device used to rapidly slow the rotational speed of a transmission input shaft44when the clutch system55is engaged to facilitate the shifting of gears in the transmission24. More specifically, upon engagement of the clutch system55, the sun gear60will begin to slow due to clutch viscous drag from the clutch system55. This reduction in rotational velocity of the sun gear60will cause the transmission input shaft44, if left un-checked, to increase in rotational velocity until gear engagement is not feasible. To prevent this situation, friction elements of the clutch brake80are pressed against a number of extrusions formed on the transmission input shaft44to create frictional drag that slows the rotating transmission input shaft, thereby facilitating gear engagement. While the exemplary clutch brake80illustrated inFIG. 2Ais shown as a mechanically actuated clutch brake80, any number of mechanical, electrical, and/or hydraulic clutch brakes may be used with the present system and method.

Continuing withFIG. 2A, the planetary gear set50is arranged such that when the prime mover22is operating in a first angular direction, the first shaft40is rotated in the same first angular direction at substantially the same rate. Consequently, the planetary gears62are also rotated in the first angular direction at substantially the same rate. During the rotation of the planetary gears62, the sun gear60may be selectively clutched to vary the output of the planetary gear set50. According to one exemplary embodiment, the clutch system55is engaged to prevent rotation of the sun gear60. When the clutch system55is engaged, the second shaft41, and consequently the sun gear60remain relatively stationary. As a result, the rotational power from the first shaft40is transmitted through the planetary gear set50and into the ring gear48at a predetermined overdrive gear ratio. According to one exemplary embodiment, the planetary gears62are configured to provide an overdrive stepdown ratio of between approximately 1 and 2 to provide an increased rotational speed and reduced torque to both the ring gear48and the transmission input shaft44. According to one embodiment, the planetary gears are a 1.5 overdrive planetary gear.

In contrast, when the clutch system55is disengaged, the second shaft41is not grounded by the clutch system55and the sun gear60is allowed to freely rotate. Consequently, the input from the prime mover22will be transmitted through the planetary gears62to the sun gear60. According to this exemplary embodiment, disengagement of the clutch system55will cause the planetary gear set50to operate in planetary mode. That is, allowing the sun gear60to freely rotate causes the rotational energy input provided by the first shaft40to be converted into rotation of the planetary gears and rotation of the sun gear60. As a result, no or very little energy is transferred to the ring gear48or the transmission input shaft44, allowing the transmission to slow or stop rotation in preparation of a shift event or another similar transmission event. Details of the operation of the torque reduction coupling system28are given below with reference toFIG. 3.

FIG. 2Billustrates a torque reduction coupling system28′, according to a second exemplary embodiment. Similar to the exemplary torque reduction coupling system28illustrated inFIG. 2A, the second exemplary embodiment illustrated inFIG. 2Bincludes a prime mover output22selectively coupled to a multi-ratio transmission24by a planetary gear set50and clutch system55′.

As illustrated inFIG. 2B, the second shaft41and the sun gear60of the planetary gear set50of the second exemplary torque reduction coupling system28′ is coupled to ground82, thereby preventing rotation. Additionally, the first shaft40having the planetary gears62of the planetary gear set50formed on a first end thereof is selectively coupled to the flywheel42of the prime mover output22by a clutch system55′. As illustrated in the second exemplary torque reduction coupling system28′, the first shaft40includes a number of clutch flanges64′ formed on the end thereof opposite the planetary gears62. As shown, the clutch flanges64′ are selectively coupled to the flywheel42of the prime mover output22by the clutch system55′.

More specifically, when the clutch system55′ is engaged, the clutch face74′ of the exemplary clutch system55′ is forced against the clutch flanges64′ by a resistive element72′, thereby coupling the clutch flanges64′ to the flywheel42of the prime mover output22. As a result, rotational energy may then be transferred from the flywheel42of the prime mover output22, to the planetary gear set50and on to the multi-ratio transmission24as described above.

In contrast, when the master clutch70is actuated, the clutch system55′ is disengaged by overcoming the force of the resistive element72′ and withdrawing the clutch face74′ from the clutch flanges64′ formed on the first shaft40. Consequently, rotational energy is no longer transmitted from the flywheel42to the first shaft40and the planetary gear set50no longer drives the transmission input shaft44. Similar to the torque reduction coupling system28illustrated inFIG. 2A, the second exemplary torque reduction coupling system28′ reduces the torque load on the components of the powertrain system20. Operation of the torque reduction coupling system28will now be given below with reference toFIG. 3.

FIG. 3illustrates an exemplary method for operating the multiple ratio powertrain system20incorporating the torque reduction coupling system28or28′. As illustrated inFIG. 3, the exemplary method begins by first disengaging the clutch mechanism (step300). According to the exemplary embodiment illustrated inFIG. 2A, the biasing agent72causes the engagement of the clutch system55absent actuation of the clutch actuator70. Consequently, disengaging the clutch system55includes manipulating the clutch actuator70. According to one exemplary embodiment, a controller34configured to manage the operation of the torque reduction coupling system28initiates a manipulation of the clutch actuator70. Once the clutch actuator70is manipulated, the clutch face74is withdrawn from the clutch flange64, allowing the second shaft41and the sun gear60to freely rotate. With the sun gear60freely rotating, the planetary gear set50is operating in planetary mode, reducing or eliminating the transfer of energy to the ring gear48and transmission input shaft44.

Similarly, as shown inFIG. 2B, actuation of the clutch actuator70withdraws the clutch face74′ from the clutch flange64′. As a result, the transfer of energy from the flywheel42to the transmission input shaft44is reduced or eliminated.

With the minimization or elimination of energy being transferred to the multi-ratio transmission24, the multi-ratio transmission24may be shifted to a desired gear ratio (step310). According to one exemplary embodiment, the automobile incorporating the multiple gear powertrain system20may be starting from rest by selecting a first gear ratio.

Once the desired gear ratio has been selected (step310), the clutch system55or55′ is again engaged (step320) to provide the transfer of rotational energy from the prime mover22to the multi-ratio transmission24. According to the exemplary embodiment illustrated inFIG. 2A, the clutch system55is engaged through a manipulation of the clutch actuator70. When the clutch actuator is again manipulated, whether manually or via a signal from the controller34, the clutch face74is forced against the clutch flanges64and the clutch body68. This actuation ceases the free rotation of the second shaft41and the sun gear60formed thereon, grounding the sun gear60to allow the transfer of rotational energy from the overdrive planetary gears62to the ring gear48and the transmission input shaft44. Additionally, during engagement of the clutch system55, the clutch brake80may be actuated to synchronize the rotational velocity of the transmission input shaft44with the output of the planetary gear set50.

Traditionally, the increased torque of the prime mover22resulted in increased wear on transmission clutches. However, the configuration of the present torque reduction coupling systems28and28′ reduce the amount of torque absorbed by the clutch when engaged. More specifically, traditional clutches are typically associated with a shaft that is fixedly coupled to the fly wheel42of the prime mover22. Consequently, traditional clutches absorb substantially all the torque produced by the prime mover22when engaged. In contrast, the present torque reduction coupling systems28and28′ clutch a fraction of the torque produced by the prime mover22. Consequently, the effective life of the clutch systems is increased. According to one exemplary embodiment, the engagement and disengagement of the clutch systems55and55′ are automatically controlled by the electronic control unit30or the torque reduction coupling system controller34.

Once the clutch is again engaged (step320), rotational energy is transferred from the prime mover22, through the planetary gear set50, to the multi-ratio transmission24. While the multiple ratio powertrain system20operates in this condition, the electronic control unit30and the various controllers32,34,36sense operating conditions to determine if another shift event is requested (step330). According to this exemplary embodiment, if a subsequent shift event is requested (YES, step330), including a requested shift to neutral, the method again engages the clutch (step300) and the above process repeats. If, however, no shift event is requested (NO, step330), the above monitoring condition continues and the multiple ratio powertrain system20continues to operate in its existing condition.

While the features of the present system and method are particularly suited for transitioning between operating sequences while the associated vehicle is moving, it is also possible to operate the torque reduction coupling system28to launch the vehicle from a state of rest.

Among other features, the torque reduction coupling system28may be readily installed in an existing vehicle driveline. Once installed, the present system and method provide for reducing the amount of torque experienced by the multi-ratio transmission while providing a clutch that experiences reduced torque problems.

The present exemplary system and method have been particularly shown and described with reference to the foregoing embodiments, which are merely illustrative of the best modes for carrying out the system and method. It should be understood by those skilled in the art that various alternatives to the embodiments of the system and method described herein may be employed in practicing the system and/or method, without departing from the spirit and scope thereof as defined in the following claims. It is intended that the following claims define the scope of the system and method and that the systems and methods within the scope of these claims and their equivalents be covered thereby. This description of the system and method should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.