Shift control system for a multiple ratio automatic transmission

• US 5,646,842 A
• Filed: 07/31/1995
• Issued: 07/08/1997
• Est. Priority Date: 10/14/1994
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Motor Company
• Inventors: Schulz, Winfried Franz-Xaver, Kirchhoffer, Johann
• Primary Examiner(s): PARK, COLLIN
• Application Number:
  US08/509,571
• Time in Patent Office: 708 Days
• Field of Search: 364/424.1, 477/34, 477/52, 477/62, 477/63, 477/127, 477/130, 477/131, 477/143, 477/149, 477/153, 477/155, 477/158, 475/269, 475/296, 475/116, 475/127, 475/138, 475/128, 475/129
• US Class Current: 701/51
• CPC Class Codes: F16H 2059/082 with different modes
• CPC Class Codes: F16H 2059/385 Turbine speed
• CPC Class Codes: F16H 2059/467 of torque converter
• CPC Class Codes: F16H 2061/0037 characterised by controlled fluid supply to lubrication circuits of the gearing see also lubrication control F16H57/0446
• CPC Class Codes: F16H 2061/0258 Proportional solenoid valve
• CPC Class Codes: F16H 2061/026 On-off solenoid valve
• CPC Class Codes: F16H 2061/044 when a freewheel device is disengaged or bridged
• CPC Class Codes: F16H 2061/0485 during range shift from neutral (N) to reverse (R)
• CPC Class Codes: F16H 2061/145 for controlling slip, e.g. approaching target slip value
• CPC Class Codes: F16H 2061/146 for smoothing gear shift shock
• CPC Class Codes: F16H 2312/02 Driving off
• CPC Class Codes: F16H 59/36 Inputs being a function of speed
• CPC Class Codes: F16H 59/44 dependent on machine speed of the machine, e.g. the vehicle
• CPC Class Codes: F16H 59/72 dependent on oil characteristics, e.g. temperature, viscosity
• CPC Class Codes: F16H 61/0021 Generation or control of line pressure
• CPC Class Codes: F16H 61/0206 Layout of electro-hydraulic control circuits, e.g. arrangement of valves for control of actuators selecting and moving final output members, e.g. shift forks F16H61/2807
• CPC Class Codes: F16H 61/061 using electric control means
• CPC Class Codes: F16H 61/067 using an accumulator
• CPC Class Codes: F16H 61/068 using an orifice control valve F16H61/067 takes precedence
• CPC Class Codes: F16H 61/08 Timing control
• CPC Class Codes: F16H 61/143 : using electric control means

Abstract

A control system for a multiple ratio transmission including two overrunning couplings acting in cooperation with friction clutches and brakes to effect controlled shifts between ratios to reduce inertia torque upon engagement of friction brakes associated with speed ratio downshifts that occur in time-controlled stages following a command for a downshift and for establishing an electronic pressure accumulator effect upon speed ratio upshifts following a command for an upshift.

Claims

1. A shift control system for multiple ratio transmissions having gearing defining plural torque flow paths from a driving shaft to a driven shaft, said gearing having a low speed ratio, a high speed ratio and at least one speed ratio intermediate said high speed ratio and said low speed ratio and selectively engageable clutch means and brake means for effecting changes between said speed ratios;

a forward drive clutch connecting said driving shaft to a torque input element of said gearing during operation in said low speed ratio, in said intermediate speed ratio and in said high speed ratio;

said brake means including an intermediate speed ratio reaction brake and an intermediate speed ratio brake servo for actuating said intermediate speed ratio brake, said brake servo having a servo cylinder and a double acting piston in said servo cylinder defining a brake apply pressure chamber and a brake release pressure chamber;

a pressure source and a main pressure regulator valve means communicating with said pressure source for developing a line pressure;

a control valve circuit connecting said pressure source selectively to said clutch means and said brake means including a first shift valve having a first position corresponding to a low speed ratio and a second position corresponding to intermediate speed ratio, a second shift valve having a first position corresponding to intermediate speed ratio and a second position corresponding to high speed ratio;

said control valve circuit including further a multiple-position manual valve connecting said pressure source to said shift valves;

a modulator valve means in fluid communication with said main regulator valve means for modulating said line pressure and developing a modulated servo pressure;

separate shift solenoid valve means for actuating said first and second shift valves;

an electronic microprocessor control means for activating said shift solenoid valve means in response to operating variables;

said first and second shift valves, in response to commands of said microprocessor control means, establishing and disestablishing a connection between said brake apply pressure chamber and said modulator valve means and between said brake release pressure chamber and exhaust, whereby said modulated servo pressure develops an intermediate speed ratio brake force independently of said line pressure whereby brake application rate is controlled by said microprocessor while said brake release chamber is exhausted during a low speed ratio to intermediate ratio upshift.

2. The system as set forth in claim 1 wherein said microprocessor control means comprises pressure control solenoid valve means communicating with signal output portions of said microprocessor control means whereby the magnitude of said modulated servo pressure is determined by said operating variables, the rate of engagement of said intermediate speed ratio brake servo thereby being controlled to establish a brake engagement accumulator effect on an upshift from said low speed ratio.

3. The system as set forth in claim 2 wherein said separate shift solenoid valve means communicate with signal output portions of said microprocessor whereby speed ratio changes between said low speed ratio and said intermediate speed ratio and the engagement capacity of said intermediate speed ratio brake servo on a downshift from said intermediate speed ratio is determined by the states of activation and deactivation of said separate shift solenoid valve means.

4. The system as set forth in claim 3 wherein said shift control system further includes means for monitoring said intermediate speed ratio brake servo capacity and said microprocessor means includes means for calculating the percentage of shift completion based upon monitored values for said brake servo capacity and for distributing a control signal to said shift solenoid valve means to interrupt application of said intermediate speed ratio brake servo if intermediate speed ratio reaction brake slip exceeds a predetermined value on a downshift from said intermediate speed ratio to said low speed ratio.

5. The system as set forth in claim 4 wherein said transmission has four forward driving ratios and includes further a low speed ratio overrunning brake means for holding a first reaction element of said gearing to establish said low speed ratio, a high speed ratio clutch means for clutching together two elements of said gearing to establish a high speed ratio and an overdrive brake means for anchoring an overdrive reaction gear element of said gearing;

said microprocessor including means for varying said modulated servo pressure during an upshift from said low speed ratio to said intermediate ratio thereby establishing intermediate speed ratio brake servo capacity accumulation;

said microprocessor further including means for controlling said intermediate speed ratio brake servo capacity during a downshift from said intermediate speed ratio to said low speed ratio, thereby accomplishing a smooth engagement of said low speed ratio.

6. The system as set forth in claim 5 wherein said circuit includes calibrated flow control orifice structure communicating with said high ratio clutch means and with said brake release chamber whereby pressure applied to said high ratio clutch means affects the rate of release of said intermediate speed ratio brake servo.

7. The control system as set forth in claim 4 wherein said gearing includes an overrunning coupling for anchoring a reaction element of said gearing during low speed ratio operation, the capacity of said intermediate speed ratio brake servo being monitored based upon said percentage of shift completion on a downshift to said low speed ratio whereby smooth overrunning coupling engagement is effected.

8. The system as set forth in claim 4 including timer means for interrupting application of said intermediate speed ratio brake means when said percentage of shift completion is less than a predetermined value within a calibrated time limit.

9. The system as set forth in claim 2 wherein said circuit includes an overdrive ratio brake means having an overdrive brake release chamber and an overdrive brake apply chamber, said overdrive brake apply chamber communicating with said modulator valve means whereby capacity of said overdrive ratio brake means is controlled upon application and release of said overdrive ratio brake means.

10. The shift solenoid system as set forth in claim 1 wherein said microprocessor means includes timing means for calculating the percentage of shift completion during a downshift interval following initiation of a speed ratio change from said intermediate speed ratio to said low speed ratio, and means for controlling release of braking capacity of said intermediate speed ratio brake servo monitored by the percent of shift completion during a speed ratio change from said intermediate speed ratio to said low speed ratio.