Hydraulic control system for continuously variable transmission
First Claim
1. A control system for a continuously variable transmission having a primary pulley and a secondary pulley, a belt intercoupling the pulleys, a chamber in the primary pulley for admitting and discharging fluid to change the effective pulley diameter and correspondingly change the transmission ratio, a chamber in the secondary pulley for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, a fluid-actuated clutch operable to transfer drive torque from the secondary pulley to an associated drivetrain, which clutch includes a chamber for receiving fluid to apply the clutch and from which fluid is discharged to release the clutch, a main line connected directly to the secondary pulley fluid chamber so that fluid at line pressure is always supplied to the secondary pulley fluid chamber a pump assembly connected to supply fluid under pressure from a first output connection to said main line, a first electromechanical control assembly having an input fluid connection coupled to said main line and an output fluid connection coupled to said clutch and chamber, a second electromechanical control assembly, having an input fluid connection coupled to said main line and an output fluid connection coupled to said primary pulley chamber, and a third electromechanical control assembly coupled to said main line, and means for supplying three electrical control signals, respectively applied to said electromechanical control assemblies, to individually regulate application and release of said clutch, the transmission ratio, and fluid pressure in said main line.
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0 Petitions
Accused Products
Abstract
A control arrangement for a continuously variable transmission includes an electronic control system and a hydraulic control system. In the hydraulic control system three separate electromechanical control assemblies are used to regulate the pressure in the secondary sheave chamber (to hold the belt tension), the fluid flow to and from the primary sheave chamber (to regulate the CVT ratio), and to control the pressure in the apply line for the clutch chamber. The pump assembly of the hydraulic control system has a first output connection for providing fluid at line (high) pressure in the main line, and a second, low pressure output connection for providing fluid at a low pressure to satisfy the clutch cooling requirements. The high pressure and low pressure systems are essentially independent of each other.
54 Citations
8 Claims
- 1. A control system for a continuously variable transmission having a primary pulley and a secondary pulley, a belt intercoupling the pulleys, a chamber in the primary pulley for admitting and discharging fluid to change the effective pulley diameter and correspondingly change the transmission ratio, a chamber in the secondary pulley for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, a fluid-actuated clutch operable to transfer drive torque from the secondary pulley to an associated drivetrain, which clutch includes a chamber for receiving fluid to apply the clutch and from which fluid is discharged to release the clutch, a main line connected directly to the secondary pulley fluid chamber so that fluid at line pressure is always supplied to the secondary pulley fluid chamber a pump assembly connected to supply fluid under pressure from a first output connection to said main line, a first electromechanical control assembly having an input fluid connection coupled to said main line and an output fluid connection coupled to said clutch and chamber, a second electromechanical control assembly, having an input fluid connection coupled to said main line and an output fluid connection coupled to said primary pulley chamber, and a third electromechanical control assembly coupled to said main line, and means for supplying three electrical control signals, respectively applied to said electromechanical control assemblies, to individually regulate application and release of said clutch, the transmission ratio, and fluid pressure in said main line.
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3. A control system for a continuously variable transmission having a primary pulley and a secondary pulley, a belt intercoupling the pulleys, a chamber in the primary pulley for admitting and discharging fluid to change the effective pulley diameter and correspondingly change the transmission ratio, a chamber in the secondary pulley for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, a fluid-actuated clutch operable to transfer drive torque from the secondary pulley to an associated drivetrain, which clutch includes a chamber for receiving fluid to apply the clutch and from which fluid is discharged to release the clutch, a main line connected to supply fluid under pressure to the secondary pulley fluid chamber, a pump assembly connected to supply fluid under pressure from a first output connection to said main line, three electromechanical control assemblies, two of which have an input fluid connection coupled to said main line and which also have an output fluid connection respectively coupled to said clutch and primary pulley chamber, the third of said electromechanical control assemblies being coupled to said main line, means for supplying three electrical control signals, respectively applied to said electromechanical control assemblies, to individually regulate application and release of said clutch, the transmission ratio, and fluid pressure in said main line, and further comprising a control line, means including a modulator valve coupled to said main line for establishing in said control line a fluid pressure which is regulated to be substantially constant and lower than the main line fluid pressure, and means coupling said control line to each of said electromechanical control assemblies for applying fluid at the pressure in said control line to each of said assemblies.
- 5. A control system for a continuously variable transmission having a primary pulley and a secondary pulley, a belt intercoupling the pulleys, a chamber in the primary pulley for admitting and discharging fluid to change the effective pulley diameter and correspondingly change the transmission ratio, a chamber in the secondary pulley for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, a fluid-actuated, fluid-cooled clutch operable to transfer drive torque from the secondary pulley to an associated drivetrain, which clutch includes a chamber for receiving fluid to apply the clutch and from which fluid is discharged to release the clutch, a main line connected to supply fluid under line pressure to the secondary pulley fluid chamber, a pump assembly connected to supply fluid at a first pressure from a first output connection to said main line, three electromechanical control assemblies, two of which have an input fluid connection coupled to said main line and which also have an output fluid connection respectively coupled to said clutch and primary pulley chambers, the third of said electromechanical control assemblies being coupled to said main line, means including an electronic control system for supplying three electrical control signals, respectively applied to said electromechanical control assemblies, to individually regulate application and release of said clutch, the transmission ratio, and fluid pressure in said main line, said pump assembly including a second output connection for supplying fluid at a second pressure substantially lower than the first fluid pressure in said main line, and a clutch cooling cutoff valve, coupled between the pump assembly second output connection and the fluid-cooled clutch, for regulating the flow of cooling fluid to the clutch.
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6. A control system for a continuously variable transmission having a primary pulley and a secondary pulley, a belt intercoupling the pulleys, a chamber in the primary pulley for admitting and discharging fluid to change the effective pulley diameter and correspondingly change the transmission ratio, a chamber in the secondary pulley for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, a fluid-actuated, fluid-cooled clutch operable to transfer drive torque from the secondary pulley to an associated drivetrain, which clutch includes a chamber for receiving fluid to apply the clutch and from which fluid is discharged to release the clutch, a main line connected to supply fluid under line pressure to the secondary pulley fluid chamber, a pump assembly connected to supply fluid at a first pressure from a first output connection to said main line, three electromechanical control assemblies, two of which have an input fluid connection coupled to said main line and which also have an output fluid connection respectively coupled to said clutch and primary pulley chambers, means coupling the third of said electromechanical control assemblies to the main line, means including an electronic control system for supplying three electrical control signals, respectively applied to said electromechanical control assemblies, to individually regulate application and release of said clutch, the transmission ratio, and fluid pressure in said main line, said pump assembly including a second output connection for supplying fluid at a second pressure substantially lower than the first fluid pressure, a clutch cooling cutoff valve, coupled between the pump assembly second output connection and the fluid-cooled clutch, for regulating the flow of cooling fluid to the clutch, in which the electromechanical control assemblies coupled to the main line comprise a high pressure system essentially independent of the clutch cooling cutoff valve coupled to the pump assembly second output connection for providing a low pressure solely for clutch cooling, a first feedback connection from the clutch chamber to the clutch cooling cutoff valve to urge the valve into a position to provide clutch cooling when the clutch is applied, and a second feedback connection from the primary pulley chamber to the clutch cooling cutoff valve to urge the valve into a position to prevent clutch cooling when the transmission is in overdrive ratio.
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7. A control system for a continuously variable transmission having a primary pulley and a secondary pulley, a belt intercoupling the pulleys, a chamber in the primary pulley for admitting and discharging fluid to change the effective pulley diameter and correspondingly change the transmission ratio, a chamber in the secondary pulley for admitting and discharging fluid to maintain tension in the belt as the transmision is driven, a fluid-actuated clutch operable to transfer drive torque from the secondary pulley to an associated drivetrain, which clutch includes a chamber for receiving fluid to apply the clutch and from which fluid is discharged to release the clutch, a main line connected to supply fluid under pressure to the secondary pulley fluid chamber, a pump assembly connected to supply fluid under pressure from a first output connection to said main line, three electromechanical control assemblies, two of which have an input fluid connection coupled to said main line and which also have an output fluid connection respectively coupled to said clutch and primary pulley chambers, means coupling the third of said electromechanical control assemblies to the main line, means for supplying three electrical control signals, respectively applied to said electromechanical control assemblies, to individually regulate application and release of said clutch, the transmission ratio, and fluid pressure in said main line, and further comprising a control line, means including a modulator valve coupled to said main line for establishing in said control line a fluid pressure which is regulated to be substantially constant and lower than the main line fluid pressure, and means coupling said control line to each of said electromechanical control assemblies for applying fluid at the pressure in said control line to each of said assemblies.
Specification