Hydraulic control system for automatic transmissions

• US 6,508,741 B1
• Filed: 10/03/2000
• Issued: 01/21/2003
• Est. Priority Date: 10/08/1999
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Oshima, Koji, Nagashima, Nobuyuki, Nomoto, Hisanori, Umeyama, Mitsuhiro, Osada, Tomoe, Ohtake, Masanori, Murakami, Akira
• Primary Examiner(s): Marmor, Charles A
• Assistant Examiner(s): PANG, ROGER L
• Application Number:
  US09/678,693
• Time in Patent Office: 840 Days
• Field of Search: 477/2, 477/3, 477/4, 477/5, 477/70, 477/71, 477/75, 477/79, 477/94, 477/86, 477/95, 477/125, 477/126, 477/149, 192/3.37, 192/216
• US Class Current: 477/95
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60K 6/543 the transmission being a continuously variable transmission
• CPC Class Codes: B60W 10/10 including control of change-speed gearings
• CPC Class Codes: F16H 57/05 of chains
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y10S 903/91 Orbital, e.g. planetary gears
• CPC Class Codes: Y10S 903/918 Continuously variable
• CPC Class Codes: Y10S 903/945 Characterized by control of gearing, e.g. control of transmission ratio

Abstract

A hydraulic control system for an automatic transmission, which has a frictional engagement unit adapted to be kept in a slipping state when in a predetermined speed changing state and in an applied state when in another gear ratio changing state; and a drain oil establishing member for establishing a drain oil when the frictional engagement unit is kept in the slipping state comprises a drain pressure switching mechanism for supplying the drain oil to the frictional face of the frictional engagement unit when the frictional engagement unit is kept in the slipping state.

Claims

1. A hydraulic control system for an automatic transmission, which has a frictional engagement unit adapted to be kept in a slipping state while being in a redetermined gear ratio changing state and in an applied state while being in another gear ratio changing state;

and a drain oil establishing member for establishing a drain oil when the frictional engagement unit is kept in the slipping state, comprising;

a drain port formed at the drain oil establishing member for outputting the drain oil from the drain oil establishing member,

a lubricating oil passage for feeding the oil to a frictional face of said frictional engagement unit, and

a drain pressure switching mechanism for supplying said drain oil to a frictional face of said frictional engagement unit connecting the drain port to the lubricating oil passage when said frictional engagement unit is kept in the slipping state, and for connecting the drain port to a drainage when the frictional engagement unit is released.

2. A hydraulic control system for an automatic transmission according to claim 1,

wherein said frictional engagement unit includes a frictional engagement unit adapted to be kept in the slipping state for a predetermined period while it is changed from a released state to an applied state.

3. A hydraulic control system for an automatic transmission according to claim 1,

wherein said frictional engagement unit includes a frictional engagement unit adapted to be kept in the slipping state for a predetermined period while it is changed from a released state to an applied state when a vehicle mounting said automatic transmission thereon starts.

4. A hydraulic control system for an automatic transmission according to claim 1, further comprising:

a first motive power source connected to said automatic transmission; and

a second motive power source connected to said automatic transmission and having a lower output than that of said first motive power source,

wherein said frictional engagement unit includes a frictional engagement unit adapted to be kept in the slipping state when the vehicle is started by said first motive power source.

5. A hydraulic control system for an automatic transmission according to claim 4,

wherein said first motive power source includes an internal combustion engine, and

wherein said second motive power source includes one of a motor and a motor/generator.

6. A hydraulic control system for an automatic transmission according to claim 5,

wherein said frictional engagement unit includes a frictional engagement unit adapted to be kept in the slipping state when the vehicle is started backward by said internal combustion engine and in the applied state when the vehicle is started backward by said motor or said motor/generator.

7. A hydraulic control system for an automatic transmission according to claim 5,

wherein said frictional engagement unit includes a frictional engagement unit adapted to be kept in the slipping state when the vehicle is started backward by said internal combustion engine and in the applied state when an electric power is generated by said motor/generator.

8. A hydraulic control system for an automatic transmission according to claim 1,

wherein said automatic transmission includes:

an input element to which a torque is inputted;

a stationary rotary element of which rotation is blocked; and

an output element for outputting a torque,

wherein said frictional engagement unit includes a frictional engagement unit for stopping the rotation of said stationary rotary element gradually, and

wherein said drain oil establishing member includes a pressure regulating mechanism for regulating the oil pressure of another frictional engagement unit for connecting said output element to a predetermined output member.

9. A hydraulic control system for an automatic transmission according to claim 1,

wherein said drain pressure switching mechanism includes:

a change-over valve having;

an input port to be supplied with said drain oil;

an output port communicating with said frictional face;

a drain port; and

a valve member for causing said input port to communicate selectively with said drain port; and

a control oil pressure establishing mechanism for establishing a control oil pressure for moving said valve member.

10. A hydraulic control system for an automatic transmission according to claim 9, further comprising:

a check valve disposed in an oil passage leading from said output port to said frictional face for blocking the flow of oil from said frictional face to said output port,

wherein said input port and said output port are always made to communicate with each other.

11. A hydraulic control system for an automatic transmission according to claim 9,

wherein said control oil pressure establishing mechanism includes a solenoid valve adapted to be electrically controlled ON/OFF for outputting a control oil pressure.

12. A hydraulic control system for an automatic transmission according to claim 1, further comprising:

a shutting mechanism for shutting the oil pressure for controlling said frictional engagement unit into the slipping state while said drain pressure switching mechanism is acting in a state in which drain oil is not supplied to said frictional face.