Method and apparatus for controlling a transfer case clutch to improve vehicle handling
First Claim
1. In a transfer case having a first output, a method for controlling a clutch, through which the first output and a second output are driveably connected, the method comprising the steps of:
- producing input torque at the clutch;
determining the current clutch slip;
establishing a first desired portion of the input torque to be transmitted by the clutch to the second 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 second output in proportion to the current clutch slip; and
changing the magnitude of torque transmitted by the clutch to the sum of the first and second magnitudes.
2 Assignments
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Accused Products
Abstract
In a motor vehicle driveline having an automatic transmission driveably connected to a transfer case whose output is continually connected to a first output, a clutch, selectively engaged in response to a control signal, driveably connects a second output to the first output. A digital computer continually monitors the occurrence of a change of clutch slip, input torque and a torque rate change to control the torque transmitted by the clutch to the second output. The control causes the clutch to transmit torque to the second output having a constant fraction of the input clutch torque and another portion that is proportional to the clutch slip. This result simulates the torque slip characteristics produced by transfer case having both a center differential mechanism and a viscous clutch.
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Citations
14 Claims
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1. In a transfer case having a first output, a method for controlling a clutch, through which the first output and a second output are driveably connected, the method comprising the steps of:
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producing input torque at the clutch;
determining the current clutch slip;
establishing a first desired portion of the input torque to be transmitted by the clutch to the second 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 second output in proportion to the current clutch slip; and
changing the magnitude of torque transmitted by the clutch to the sum of the first and second magnitudes. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for controlling, with the aid of a digital computer, a clutch through which a first output and a second output are driveably connected, the method comprising the steps of:
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inputting to the computer a data base including at least the current torque produced by an engine, a first desired portion of an input torque to be transmitted by the clutch to the second output, and a proportional constant;
repetitively providing the computer with the speed of the first output and speed of the second output;
repetitively calculating in the computer at frequent intervals;
the current clutch slip;
the input torque at the clutch;
a first magnitude of clutch torque to be transmitted to the second output corresponding to the first desired portion of input torque;
a second magnitude of clutch torque, the product of the current clutch slip and the proportional constant, to be transmitted to the second output; and
a clutch duty cycle corresponding to the sum of the first and second magnitudes of clutch torque; and
subsequently outputting from the computer to a solenoid a signal representing the clutch duty cycle, whereby the magnitude of torque transmitted by the clutch is changed in response to the signal. - View Dependent Claims (9, 10, 11)
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12. A system for controlling a clutch, through which a first output and a second output are driveably connected, the system comprising:
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means for generating a first signal representing the current speed of the first output and a second signal representing the current speed of the second output;
means responsive to the first and second signals for determining the current clutch slip;
means for calculating the magnitude of input torque at the clutch;
means for determining a first magnitude of clutch torque corresponding to a first desired portion of input torque to be transmitted by the clutch to the second output;
means for determining a second magnitude of clutch torque to be transmitted to the second output in proportion to the current clutch slip; and
means producing an output signal for changing the magnitude of torque transmitted by the clutch to the sum of the first and second magnitudes of clutch torque. - View Dependent Claims (13, 14)
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Specification