Method and system for controlling a transfer case clutch to protect against excessive heat
First Claim
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1. A method for controlling a clutch that driveably connects an input and an output, comprising the steps of:
- producing input torque at the clutch;
operating the clutch partially engaged;
determining the current clutch slip;
establishing a first desired portion of the input torque to be transmitted by the clutch to the output;
determining a first magnitude of clutch torque corresponding to the first desired portion;
determining a second magnitude of clutch torque to be transmitted to the output in proportion to the current clutch slip;
changing the magnitude of torque transmitted by the clutch to the sum of the first and second magnitudes;
calculating a temperature of the clutch;
establishing a reference clutch temperature;
comparing the calculated clutch temperature and reference clutch temperature; and
if the calculated clutch temperature equals or exceeds the reference clutch temperature, then increasing the degree of clutch engagement sufficiently to reduce the calculated temperature of the clutch.
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Abstract
In a motor vehicle driveline including a transfer case whose output is continually connected to a first output, a clutch, operating partially engaged, responds to a control signal to change the degree of clutch engagement, whereby a second output is connected driveably to the first output. A digital computer continually calculates a change in clutch temperature at frequent intervals and updates a running sum of clutch temperature changes. The control causes the clutch to more fully engage if the current calculated clutch temperature exceeds a predetermined reference clutch temperature.
29 Citations
11 Claims
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1. A method for controlling a clutch that driveably connects an input and an output, comprising the steps of:
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producing input torque at the clutch; operating the clutch partially engaged; determining the current clutch slip; establishing a first desired portion of the input torque to be transmitted by the clutch to the output; determining a first magnitude of clutch torque corresponding to the first desired portion; determining a second magnitude of clutch torque to be transmitted to the output in proportion to the current clutch slip; changing the magnitude of torque transmitted by the clutch to the sum of the first and second magnitudes; calculating a temperature of the clutch; establishing a reference clutch temperature; comparing the calculated clutch temperature and reference clutch temperature; and if the calculated clutch temperature equals or exceeds the reference clutch temperature, then increasing the degree of clutch engagement sufficiently to reduce the calculated temperature of the clutch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a transfer case having first and second outputs, a system for controlling a clutch that driveably connects the first output and second output, comprising:
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means for operating the clutch partially engaged; means for calculating the temperature of the clutch; establishing a reference clutch temperature; means for comparing the calculated temperature of the clutch and reference clutch temperature; and means for producing an output signal for increasing the degree of clutch engagement sufficiently to reduce the calculated temperature of the clutch, if the calculated temperature of the clutch equals or exceeds the reference clutch temperature. - View Dependent Claims (10, 11)
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Specification