System and method for decreasing ratio changing time in electronically enhanced powertrain systems

Abstract

A system and method for decreasing the time required to complete a ratio change in an electronically enhanced powertrain system is provided. The powertrain system includes a number of devices for providing a retarding torque to engine rotation to increase the decay rate of the engine speed during an upshift. These devices include an engine brake and an input shaft brake. A retarding torque is also provided by increasing engine accessory load by controlling various engine accessories such as a cooling fan, an air compressor, a hydraulic pump, an air conditioning compressor, and an alternator.

Description

RELATED APPLICATIONSThis application is related to copending applications U.S. Ser. No. 08 / 103,947, filed Aug. 10, 1993, titled CONTROL SYSTEM / METHOD FOR ENGINE BRAKE-ASSISTED SHIFTING and U.S. Ser. No. 08 / 179,060, filed Jan. 7, 1994, titled ENGINE BRAKE-ENHANCED UPSHIFT CONTROL METHOD / SYSTEM, and assigned to the same assignee, EATON CORPORATION, as this application.TECHNICAL FIELDThe present invention relates to a system and method for decreasing the time required to complete a ratio change in an electronically enhanced engine and transmission system.BACKGROUND ARTElectronically enhanced transmission systems have been well developed in the prior art as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,595,986; 4,648,290; 4,722,248; and 5,050,427, the specifications of which are hereby incorporated by reference in their entirety. Transmission systems such as these have been utilized to provide a variety of gear ratios to enhance the flexibility and torque multiplication of an ...

AI Technical Summary

Benefits of technology

It is, therefore, an object of the present invention to provide a system and method for reducing the time required to complete a ratio change, in particular, an upshift ratio change, in a manual, semi-automatic or fully automatic transmission.

It is an additional object of the present invention to provide a system which reduces the time required to achieve synchronous speed by increasing a retarding force acting on engine rotation.

Another object of the present invention is to provide a system which automates control of an engine compression brake to decrease ratio changing time in a manual, semi-automatic or fully automatic transmission.

A still further object of the present invention is to provide a system which increases engine load to supply a variable retarding force so as to improve ratio changing times in a manual, semi-automatic or fully automatic transmission.

Yet another object of the present invention is to provide a system which reduces driveline disturbances during an upshift by utilizing an engine brake when a transmission neutral condition is sensed.

In carrying out the above object and other objects and features of the present invention, a control system is provided for reducing the ratio changing time of a mechanical transmission system. The transmission system includes an engine selectively coupled by a master friction clutch to a mechanical change gear transmission. The system also includes an electronic control unit for receiving a plurality of input signals indicative of an engine speed, an output shaft speed, and a neutral gear state of the transmission. The electronic control unit also generates command signals for controlling the engine and the transmission. The transmission includes a plurality of gear ratio combinations, and a neutral gear state, selectively engageable between a transmission input shaft and a transmission output shaft. The control system utilizes a sensor for sensing the neutral gear state which occurs after disengaging a current gear ratio and before effecting a target gear ratio in the transmission. The system also includes devices for applying a retarding torque to the engine in response to a command from the electronic control unit. The retarding torque is applied to the engine while the engine speed is above the synchronous speed at which the target gear ratio is effected, so as to increase engine deceleration and reduce ratio changing time. A method is also provided for use with the system and similar systems.

Problems solved by technology

In these applications, inefficiency in ratio changing may accumulate to a significant amount of wasted time.

First, the operator must interrupt the transfer of torque from the engine through the transmission to the driveline.

However, input shaft brakes with sufficient capacity to decrease ratio changing time add cost and complexity to the transmission system and require accurate sequencing of events for satisfactory operation, so many transmissions only utilize simple versions of these devices.

This results in a correspondingly longer time to complete a ratio change.

Exhaust brakes do not offer the responsiveness or flexibility of engine compression brakes although they are less expensive to employ.

For this application, manual operation of the engine brake often results in large torque disturbances to the vehicle driveline due to inappropriate timing in applying and releasing the engine brake.

This reduces drivability of the vehicle and may also adversely affect the durability of powertrain components.

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