Relay valve with latch area for controlling a friction device

• US 6,077,182 A
• Filed: 06/14/1999
• Issued: 06/20/2000
• 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 (General Motors Company)
• Inventors: McCauley, Phillip Franklin, Long, Charles Francis
• Primary Examiner(s): ESTREMSKY, SHERRY LYNN
• Application Number:
  US09/333,149
• Time in Patent Office: 372 Days
• Field of Search: 475/16, 475/127, 475/128, 477/125, 477/131, 477/906
• US Class Current: 475/128
• CPC Class Codes: F16H 2059/006 Overriding automatic control
• CPC Class Codes: F16H 2061/1204 for malfunction caused by simultaneous engagement of different ratios resulting in transmission lock state or tie-up condition
• CPC Class Codes: F16H 2061/1232 Bringing the control into a predefined state, e.g. giving priority to particular actuators or gear ratios
• CPC Class Codes: F16H 2061/1236 using fail priority valves
• CPC Class Codes: F16H 2061/1244 Keeping the current state
• CPC Class Codes: F16H 2061/1268 Electric parts of the controller, e.g. a defect solenoid, wiring or microprocessor
• CPC Class Codes: F16H 2306/00 Shifting
• CPC Class Codes: F16H 61/12 Detecting malfunction or potential malfunction, e.g. fail safe in control of hydrostatic gearing F16H61/4192; Circumventing or fixing failures
• CPC Class Codes: F16H 61/686 with orbital gears
• CPC Class Codes: Y10S 477/906 Means detecting or ameliorating the effects of malfunction or potential malfunction

Abstract

A powertrain has a multi-speed transmission with an electro-hydraulic control system for establishing the operating conditions of the transmission. The control system has a plurality of shift or relay valves that are each alternatively positioned by a spring or a solenoid controlled pressure bias. One of the relay valves, which controls two friction devices, has a latching mechanism which will retain the valve in the pressure set condition until the pressure in one of the friction devices is decreased below a predetermined pressure. The latch mechanism will also serve to retain the transmission in a low forward ratio if an electrical discontinuance should occur when the transmission is conditioned for the low forward ratio. The control will also permit retention in the highest forward ratio if electrical discontinuance occurs during operation in this ratio. Following an engine shutdown and restart, the transmission can be selectively operated in a reverse ratio, a neutral condition or the third forward ratio.

Claims

1. A control system for a multi-ratio powertrain having a plurality of selectively engageable friction devices for selectively establishing a reverse ratio, a neutral condition and five forward drive ratios, said control comprising:

two control valves for selectively issuing variable pressure command signals;

a plurality of valves means for issuing shift command pressures

a plurality of shift valves each having a spring set position and a pressure set position for controlling fluid distribution, said pressure set position being established by respective ones of said valve means, a first of said shift valves being effective in said pressure set position to deliver said command signal from a first of said control valves to a first of said friction devices to selectively engage said first friction device in the reverse ratio, the neutral condition and a first and lowest of the forward drive ratios, and being effective in said spring set position to deliver said command signal from said first control valve to a third of said friction devices which is selectively engaged in at least one forward drive ratio separated from said first forward drive ratio by at least a second of said forward drive ratios, said first shift valve having a differential area responsive to said command signal being issued to said first friction device during said first forward ratio to maintain said first shift valve in said pressure set position when said command pressure from said valve means is prematurely discontinued.

2. The control system defined in claim 1 further comprising:

said first friction device having a torque capacity proportional to the variable pressure command signal and said first shift valve being retained in said pressure set position by said pressure command signal acting on said differential area until said torque capacity of said first friction device is below a predetermined torque valve.

3. A control system for a multi-ratio powertrain having a plurality of friction devices which are selectively engaged in pairs to selectively provide a reverse ratio and five forward ratios, one of said friction devices being engaged in a neutral condition, a first of said friction devices being engaged during the reverse ratio, the neutral condition and a first and lowest of the forward ratios, a second of the friction devices being engaged during a second of said forward ratios, and a third of the friction devices being engaged during the reverse ratio, a third and a fifth forward ratio, said control comprising:

a source of fluid pressure;

a plurality of electrically actuated variable pressure output valves connected with said source;

a plurality of electrically actuated control valves;

first, second and third shift valves each having a spring set position and a pressure set position, said pressure set position of each shift valve being controlled by a respective one of said control valves;

said first of said shift valves being operable in said spring set position to control distribution of pressure from a first of said variable pressure output valves to the third friction device and in the pressure set position to control distribution of pressure from said first variable pressure output valve to the first friction device, a differential area formed on said first shift valve being subjected to the pressure in the first friction device during engagement thereof and being effective to delay movement of said first shift valve to said spring set position until the pressure level of the first friction device is reduced below a predetermined value to thereby prevent fluid distribution to said third friction device when said first friction device is being disengaged.

4. The control system defined in claim 3 further comprising:

said first variable pressure output valve being operable to have maximum pressure output when the electrical function is off, said first variable pressure output valve being operable to maintain pressure at said differential area in the event of the electrical function discontinues during first ratio operation of the powertrain to thereby retain the powertrain in the first ratio at least until the neutral condition is selected or the pressure source is discontinued.