Apparatus and method of neutral start control of a power transmission
First Claim
1. A control system for a vehicle transmission of the type including an input shaft coupled to a vehicle engine, an output shaft for driving the vehicle, a plurality of intermeshing gears, and a plurality of fluid clutches associated with the gears, the clutches being selectively engageable in predetermined combinations via fluid valving to establish desired gear ratios between the input shaft and the output shaft, the control system comprising:
- a sensor for generating an engine running signal representative of whether the vehicle engine is running;
an operator-movable command device for generating at least a neutral command signal;
a clutch engagement circuit including a plurality of solenoid coils associated with the clutches and selectively energizable to engage the clutches, and a driver circuit coupled to the solenoid coils for selectively energizing the coils; and
a control circuit coupled to the sensor, the command device and the clutch engagement circuit, the control circuit prevents engagement in a gear ratio by disabling the solenoid coils upon startup of the vehicle engine until the engine running signal represents that the vehicle engine is running and the command device generates a neutral command signal.
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Accused Products
Abstract
A control system for a work vehicle transmission includes a sensor for detecting the output speed of the vehicle engine and an operator-movable command device for placing the transmission in a neutral condition. The transmission includes a plurality of intermeshing gears, and clutches associated with certain of the gears for selectively placing the transmission in various gear ratios for driving the vehicle. The clutches are engaged and disengaged by fluid valving in response to energization of solenoid coils driven by valve driver circuits. The sensor, the command device and the driver circuits are coupled to a control circuit, preferably including a microprocessor, for controlling engagement and disengagement of the transmission clutches. Upon startup, the control circuit disables the driver circuits to place the transmission in a neutral condition despite the position of the command device. The control circuit maintains the driver circuits disabled until the vehicle engine is running, as indicated by the speed sensor, and a neutral command signal is received. The neutral start routine serves as a redundant system with an analog neutral start circuit that normally disables the vehicle starter unless a neutral transmission condition is commanded upon startup. The system thus provides a neutral start feature in the event the neutral start circuit fails or is defeated, such as by jump starting the vehicle engine.
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Citations
21 Claims
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1. A control system for a vehicle transmission of the type including an input shaft coupled to a vehicle engine, an output shaft for driving the vehicle, a plurality of intermeshing gears, and a plurality of fluid clutches associated with the gears, the clutches being selectively engageable in predetermined combinations via fluid valving to establish desired gear ratios between the input shaft and the output shaft, the control system comprising:
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a sensor for generating an engine running signal representative of whether the vehicle engine is running; an operator-movable command device for generating at least a neutral command signal; a clutch engagement circuit including a plurality of solenoid coils associated with the clutches and selectively energizable to engage the clutches, and a driver circuit coupled to the solenoid coils for selectively energizing the coils; and a control circuit coupled to the sensor, the command device and the clutch engagement circuit, the control circuit prevents engagement in a gear ratio by disabling the solenoid coils upon startup of the vehicle engine until the engine running signal represents that the vehicle engine is running and the command device generates a neutral command signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A control system for a vehicle transmission, the vehicle including an engine, a starter coupled to the engine, and a transmission including an input shaft coupled to the engine, an output shaft for driving the vehicle, a plurality of intermeshing gears, and a plurality of fluid clutches associated with the gears, the clutches being selectively engageable in predetermined combinations via fluid valving to establish desired gear ratios between the input shaft and the output shaft, the control system comprising:
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a clutch engagement circuit including a plurality of solenoid coils associated with the clutches and selectively energizable to engage the clutches, and a driver circuit coupled to the solenoid coils for selectively energizing the coils in response to control signals; an analog electrical neutral start circuit for placing the transmission in a neutral condition upon startup of the engine; and a digital control circuit coupled to the clutch engagement circuit, the control circuit redundantly placing the transmission in a neutral condition upon startup of the engine and until the engine is in a running condition and a neutral condition is commanded by an operator. - View Dependent Claims (10, 11, 12, 13)
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14. A method for controlling a transmission in a vehicle of the type including an engine, a transmission coupled between the engine and a drive train, and an operator-movable command device for placing the transmission in preselected forward, neutral and reverse drive conditions, the method comprising the steps of:
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(a) sensing a parameter representative of whether the vehicle engine is running and generating an engine running signal representative thereof; (b) sensing a position of the command device and generating a command signal representative thereof; (c) disabling electronic driver circuits for shifting transmission control solenoid valves to place the transmission in a neutral condition; and (d) enabling the electronic driver circuits to permit the transmission to be shifted to forward and reverse gear ratios and thereby to transmit power from the engine to the drive train when the engine running signal and the command signal indicate a neutral condition is commanded and the vehicle engine is running. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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Specification