TRANSMISSION SHIFTING WITH SPEED DITHER AND TORQUE DITHER
First Claim
1. A method of engaging a transmission of a series hydraulic hybrid system having at least one pump/motor selectively connectable to an output drive shaft of the transmission, the method comprising the steps of:
- calculating a desired speed of an output shaft of the at least one pump/motor;
operating the at least one pump/motor at a target speed that is the desired output shaft speed plus a desired speed dither; and
engaging the output shaft of the pump/motor with the output shaft of the transmission when the target speed is reached within a prescribed speed error threshold;
wherein the operating includes regulating the flow of fluid to and from an accumulator to the pump/motor to achieve the target speed.
1 Assignment
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Accused Products
Abstract
A system and method of dithering speed and/or torque for shifting a transmission of a vehicle having an engine, a reversible, variable displacement hydraulic motor/pump which can be driven by the engine, a hydraulic accumulator supplied by said motor/pump, and at least one reversible hydraulic driving motor for propelling the vehicle supplied with fluid by the hydraulic accumulator and/or by said motor/pump operating as a pump. A transmission unit connects the engine with the variable displacement hydraulic motor/pump during a first mode of operation (city mode) and connects the engine to a vehicle drive wheel during a second mode of operation. The system utilizes stored hydraulic energy to dither the output of the driving motor in order to achieve quick and smooth shifts between city and highway mode, or between various ranges within the city mode.
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Citations
15 Claims
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1. A method of engaging a transmission of a series hydraulic hybrid system having at least one pump/motor selectively connectable to an output drive shaft of the transmission, the method comprising the steps of:
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calculating a desired speed of an output shaft of the at least one pump/motor; operating the at least one pump/motor at a target speed that is the desired output shaft speed plus a desired speed dither; and engaging the output shaft of the pump/motor with the output shaft of the transmission when the target speed is reached within a prescribed speed error threshold; wherein the operating includes regulating the flow of fluid to and from an accumulator to the pump/motor to achieve the target speed. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of disengaging a transmission of a series hydraulic hybrid system having at least one pump/motor selectively connectable to an output drive shaft of the transmission, the method comprising the steps of:
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calculating a desired torque of an output shaft of the at least one pump/motor, operating the at least one pump/motor at a target torque that is the desired torque plus a desired torque dither; disengaging the output shaft of the pump/motor with the output shaft of the transmission when the target torque is commanded; wherein the operating includes regulating a flow of fluid to and from an accumulator to the pump/motor to achieve the target torque. - View Dependent Claims (8, 9)
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10. A hybrid transmission system for a vehicle comprising:
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a primary hydraulic pump/motor; a secondary hydraulic pump/motor connected to the primary hydraulic pump/motor via a high pressure manifold; and an accumulator for storing pressurized fluid connected to both the primary and secondary pump/motors via the high pressure manifold; wherein the transmission has an input shaft for receiving power from a prime mover, an output drive shaft, power transmission components for selectively coupling the input shaft to at least one of the primary hydraulic pump and the output drive shaft and for selectively coupling the secondary hydraulic pump/motor to the output drive shaft, and a controller for calculating a desired speed of an output shaft of the secondary pump/motor, operating the secondary pump/motor at a target speed that is the desired speed plus a desired speed dither, and engaging the output shaft of the secondary pump/motor with the output drive shaft unit when the target speed is reached within a prescribed speed error threshold; wherein the controller controls the high pressure manifold to supply fluid from the accumulator to the secondary pump/motor for operating the secondary pump/motor at the target speed. - View Dependent Claims (11, 12, 13, 14, 15)
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Specification