Method for controlling transmission control clutches

• US 5,449,329 A
• Filed: 08/20/1993
• Issued: 09/12/1995
• Est. Priority Date: 07/20/1993
• Status: Expired due to Term

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Jeffries, Dennis L., Brandon, David E., Falck, Peter L.
• Primary Examiner(s): Wright, Dirk
• Assistant Examiner(s): TA, KHOI QUANG
• Application Number:
  US08/095,434
• Time in Patent Office: 753 Days
• Field of Search: 477/70, 477/76, 477/78, 477/86, 477/174, 477/143, 364/424.1
• US Class Current: 477/70
• CPC Class Codes: F16H 2059/6807 Status of gear-change operation, e.g. clutch fully engaged
• CPC Class Codes: F16H 2061/0255 Solenoid valve using PWM or duty-cycle control
• CPC Class Codes: F16H 2061/062 for controlling filling of clutches or brake servos, e.g. fill time, fill level or pressure during filling
• CPC Class Codes: F16H 61/061 using electric control means
• CPC Class Codes: F16H 61/08 Timing control

Abstract

A system and method for controlling the clutches in a vehicle powershift transmission. The control system includes a microprocessor which periodically executes an algorithm and which has a memory in which is stored a sequential set of time reference values and a sequential set of pressure values. The control system applies to each oncoming element a fill pressure pulse for fill periods which are unique for each element. The control system determines shift time values, subsequent to filling of the control elements, as a function of the fill period. The control system applies pressure signals to the control elements at times represented by the shift time values which are unique for each element. The control system determines, subsequent to a realignment time, realignment shift time values which are the same for all of the control elements. The control system also applies pressure signals to the control elements subsequent to the realignment time, at times determined as a function of the realignment shift time values.

Claims

1. In a vehicle powershift transmission having a plurality of hydraulic pressure operated control elements for shifting the transmission, a control system for controlling pressurization of the control elements, the control system comprising:

means for applying to each oncoming element a fill pressure pulse for fill periods which are unique for each element;

means for determining shift time values, subsequent to filling of the control elements, as a function of the fill period;

means for applying pressure signals to the control elements at times represented by the shift time values, wherein the shift time values for each element are unique;

means for determining, subsequent to a realignment time, realignment shift time values which are the same for all of the control elements; and

means for applying pressure signals to the control elements subsequent to the realignment time, at times determined as a function of the realignment shift time values.

2. The control system of claim 1, further comprising:

a memory for storing a sequential set of time reference values and a sequential set of pressure command values, each pressure command value corresponding to one of the time reference values;

means for comparing the shift time values to one of the stored reference time values and selecting one of the stored pressure command values as a function of said comparison; and

means for applying to the control elements pressure signals corresponding to the selected pressure command values.

3. The control system of claim 2, further comprising:

means for updating the selected time reference value to a next sequential time reference value if the time shift-value is not less than the one time reference value.

4. The control system of claim 1, further comprising:

a memory for storing a sequential set of time reference values, a sequential set of pressure command values and a sequential set of pressure slope values, each pressure command value and pressure slope value corresponding to one of the time reference values; and

means for applying to the control element a pressure corresponding to a selected one of the pressure command values plus the product of a selected one of the slope values multiplied by a time interval value.

5. In a vehicle powershift transmission having a hydraulic pressure operated control element for shifting the transmission, a microprocessor-based system for controlling pressurization of the control element, the system comprising:

a memory having stored therein a sequential set of time reference values and a sequential set of pressure command values, each pressure command value corresponding to one of the time reference values;

means for, prior to application to the control element of a fill pressure pulse, periodically incrementing an absolute time value and setting a shift time value equal to the absolute time value;

means for generating a wakeup command;

means for, in response to the wakeup command, periodically incrementing a base pulse time value, periodically incrementing the absolute time value and preventing incrementing of the shift time value;

means for, when the base pulse time value is equal to a predetermined wakeup time value, setting a wakeup flag, incrementing the absolute time value and setting the shift time value equal to the absolute time value plus a maximum time value less a fill duration time value;

means for, after the wakeup flag is set and the control element is filled, incrementing the absolute time value, comparing the absolute time value to a realignment time value, and if the absolute time value is less than the realignment time value, setting the shift time value equal to the absolute time value plus the maximum time value less the fill duration time value, and if the absolute time value is not less than the realignment time value, setting the shift time value equal to the absolute time value plus the maximum time value;

means for comparing the shift time values to one of the time reference values and selecting one of the stored pressure command values from memory; and

means for applying to the control element a pressure corresponding to the selected pressure command value.

6. In a vehicle powershift transmission having a hydraulic pressure operated control element for shifting the transmission, a method of controlling pressurization of the control element, the method comprising:

a) generating a wakeup command;

b) applying a fill pressure pulse to the control element;

c) filling the control element with hydraulic fluid;

d) storing in a memory a sequential set of time reference values and a sequential set of pressure command values, each pressure command value corresponding to one of the time reference values;

e) prior to application to the control element of a fill pressure pulse, periodically incrementing an absolute time value and setting a shift time value equal to the absolute time value;

f) in response to the wakeup command, periodically incrementing a base pulse time value, periodically incrementing the absolute time value and preventing incrementing of the shift time value;

g) when the base pulse time value is equal to a predetermined wakeup time value, setting a wakeup flag, incrementing the absolute time value and setting the shift time value equal to the absolute time value plus a maximum time value less a fill duration time value;

h) after the wakeup flag is set and the control element is filled, incrementing the absolute time value, comparing the absolute time value to a realignment time value, and if the absolute time value is less than the realignment time value setting the shift time value equal to the absolute time value plus the maximum time value less the fill duration time value, and if the absolute time value is not less than the realignment time value setting the shift time value equal to the absolute time value plus the maximum time value; and

i) after each of the steps e), f), and g), comparing the shift time values to one of the time reference values and selecting one of the stored pressure command values from memory, and applying to the control element a pressure corresponding to the selected pressure command value.

7. The method of claim 6, further comprising:

updating the time reference value to the next sequential time reference value if the time shift value is not less than the time reference value.

8. The method of claim 6, further comprising:

storing in the memory a sequential set of pressure slope values, each pressure slope value corresponding to one of the time reference values; and

applying to the control element a pressure corresponding to the selected pressure command value plus the product of the slope value multiplied by a time interval value.

9. In a vehicle powershift transmission having a hydraulic pressure operated control element for shifting the transmission, a method of controlling pressurization of the control element, the method comprising:

generating a wakeup command;

applying a fill pressure pulse to the control element;

filling the control element with hydraulic fluid;

storing a set of pressure command values in a memory, each pressure command value corresponding to a time reference value;

prior to application to the control element of a fill pressure pulse, periodically incrementing an absolute time value and setting a shift time value equal to the absolute time value;

in response to the wakeup command, applying to the control element the fill pressure pulse, and during application of the fill pressure pulse, periodically incrementing a base pulse time value, periodically incrementing the absolute time value and preventing incrementing of the shift time value;

when the base pulse time value is equal to a predetermined wakeup time value, setting a wakeup flag, incrementing the absolute time value and setting the shift time value equal to the absolute time value plus a maximum time value less a fill duration time value;

after the wakeup flag is set and the control element is filled, incrementing the absolute time value, comparing the absolute time value to a realignment time value, and if the absolute time value is less than the realignment time value setting the shift time value equal to the absolute time value plus the maximum time value less the fill duration time value, and if the absolute time value is not less than the realignment time value, setting the shift time value equal to the absolute time value plus the maximum time value; and

comparing the shift time values to the time reference values and selecting one of the stored pressure command values from memory;

applying to the control element a pressure corresponding to the selected pressure command value.