Multiple gain trim valve for a selectively engageable friction device

• US 6,155,949 A
• Filed: 06/14/1999
• Issued: 12/05/2000
• Est. Priority Date: 06/14/1999
• Status: Expired due to Term

• Current Assignee: Allison Transmission Incorporated (Allison Transmission Holdings Incorporated)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Dadel, Martin Robert, Long, Charles Francis, Cole, Jeffrey Jay
• Primary Examiner(s): ESTREMSKY, SHERRY LYNN
• Application Number:
  US09/332,848
• Time in Patent Office: 540 Days
• Field of Search: 475/120, 475/127, 475/128, 475/129
• US Class Current: 475/127
• CPC Class Codes: B60W 2050/0022 Gains, weighting coefficients or weighting functions
• CPC Class Codes: F16D 2048/0209 characterised by fluid valves having control pistons, e.g. spools
• CPC Class Codes: F16D 2048/0221 Valves for clutch control systems; Details thereof
• CPC Class Codes: F16D 2500/70294 Valve look-up tables
• CPC Class Codes: F16D 2500/70406 Pressure
• CPC Class Codes: F16D 48/066 Control of fluid pressure, e.g. using an accumulator F16D48/062, F16D48/068 take precedence
• CPC Class Codes: F16H 2061/0253 Details of electro hydraulic valves, e.g. lands, ports, spools or springs
• CPC Class Codes: F16H 61/065 using fluid control means

Abstract

A control for a multi-speed transmission has a multiple gain trim valve that controls the engagement pressure rise in a selectively engageable torque transmitting mechanism. The trim valve has a valve spool and a plug valve longitudinally aligned in a valve bore such that four separate areas are present. One of the areas has the engagement pressure of the torque transmitting mechanism imposed thereon. Another of the areas has a control pressure imposed thereon and the remaining two areas are subjected to the trim pressure. The gain rate between the trim pressure and the engagement pressure determines the rapidity with which the torque transmitting mechanism is engaged. The control pressure reduces the effect of the trim pressure to provide a low gain rate until the product of the trim pressure and one of the areas is equal to or greater than the product of the control pressure and the area on which it operates. By reducing the control pressure to a zero value, a maximum gain rate is attained at the trim valve.

Claims

1. A transmission control system having a trim valve for controlling the engagement pressure of a torque transmitting mechanism comprising:

a pressure source;

means for distributing a trim control pressure, a boost control pressure and a main pressure from said pressure source;

a valve body including a main pressure port connected with said main pressure distributing means, a trim pressure port being connected with said trim control pressure distributing means, a boost control pressure port being connected with said boost control pressure distributing means an exhaust port and a feed port connected with the torque transmitting mechanism;

said trim valve comprising a spool valve slidably disposed in a valve bore in said valve body, a plug valve slidably disposed in said valve bore, said valve bore cooperating with said spool valve to form first responsive area connected with said feed port and second pressure responsive area connected with said trim pressure port, and cooperating with said plug valve to form third pressure responsive area connected with said boost control pressure port and fourth pressure responsive area connected with said trim pressure port, said spool valve being responsive to pressure in said first and fourth pressure responsive areas to control distribution of fluid between said feed port and said main port and said exhaust port when said boost control pressure port is not pressurized, and said spool valve being responsive to pressure in said first pressure responsive area, said second pressure responsive area when said boost control pressure is at a first pressure level and said trim control pressure is at or below a second predetermined level and being responsive to said first pressure responsive area, said third pressure responsive area and said fourth pressure responsive area when said trim pressure is above said second predetermined level and said boost pressure is at said first predetermined level.

2. The transmission control system having a trim valve defined in claim 1 further comprising:

said first and third pressure responsive areas being responsive to pressure therein to urge said spool valve to connect said feed port with said exhaust port and said second and fourth pressure responsive areas being responsive to pressure to urge said spool valve to connect said main port with said feed port.

3. A transmission control system having a trim valve for controlling the engagement pressure (Pc) of a torque transmitting mechanism comprising:

a pressure source;

means for distributing a trim control pressure (Pt), a boost control pressure (Pb) and a main pressure from said pressure source;

a valve body including a main pressure port connected with said main pressure distributing means, a trim pressure port being connected with said trim control pressure distributing means, a boost control pressure port being connected with said boost control pressure distributing means an exhaust port and a feed port connected with the torque transmitting mechanism;

said trim valve comprising a spool valve slidably disposed in a valve bore in said valve body, a plug valve slidably disposed in said valve bore, said valve bore cooperating with said spool valve to form first responsive area (A1) connected with said feed port and second pressure responsive area (A2) connected with said trim pressure port, and cooperating with said plug valve to form third pressure responsive area (A3) connected with said boost control pressure port and fourth pressure responsive area (A4) connected with said trim pressure port;

and a bias spring imposing a force (Fs) on said spool valve; and

said trim valve providing a pressure gain curve defined by the value Pc/Pt, including a first gain curve defined by Pc=Pt*(A4/A1)-(Fs/A1) when a boost control pressure is not present and a second gain curve having a first phase defined by Pc=Pt*(A2/A1)-(Fs/A1) when Pt<

Pb and a second phase defined by Pc=Pt*A4/A1)-Pb*(A3/A1)-(Fs/A1) when Pt>

Pb.