Interrelated power delivery controls – including engine control – Clutch control – Condition responsive control
Reexamination Certificate
2001-02-28
2004-02-17
Bonck, Rodney H. (Department: 3681)
Interrelated power delivery controls, including engine control
Clutch control
Condition responsive control
C477S079000, C477S154000, C192S10900B
Reexamination Certificate
active
06692409
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hydraulic change speed system for a working vehicle having a gear type change speed device shiftable by an actuator, a hydraulic clutch connected to a power transmission line including the gear type change speed device, a valve unit for switching operative states of the hydraulic clutch, and a controller for controlling the valve unit. In this hydraulic change speed system, the controller depressurizes the hydraulic clutch to begin disengaging the hydraulic clutch in response to a start of operation of the actuator, and pressurizes the hydraulic clutch to start engaging the hydraulic clutch in response to a finish of operation of the actuator. The operation of the valve unit is interlocked to the operation of the actuator. The hydraulic clutch is pressurized rapidly from for a set time from start of an operation to engage the hydraulic clutch, and pressurized gradually after the set time.
2. Description of the Related Art
In the hydraulic change speed system for a working vehicle noted above, the valve unit switches the hydraulic clutch in response to an operation of the actuator for shifting the gear type change speed device. This eliminates the trouble of manually operating the clutch to break power transmission temporarily during a gear shifting operation. Further, for the set time from the start of an operation to engage the hydraulic clutch, the controller increases the speed of pressuring the hydraulic clutch by the valve unit. A reduced time is required for engaging the hydraulic clutch, compared with the case of gradually pressuring the hydraulic clutch by the valve unit. After the set time, the controller controls the valve unit to pressurize the hydraulic clutch gradually, thereby suppress a shock occurring with a clutch engagement.
In such a mechanism for a working vehicle, an engaging operation of the hydraulic clutch is started upon completion of a gear shifting operation from neutral position when the vehicle is started. At this time, pressure oil is supplied to the hydraulic clutch completely empty of pressure oil. On the other hand, when an engaging operation of the hydraulic clutch is started upon completion of a gear shifting operation while the vehicle is running, pressure oil is supplied to the hydraulic clutch not completely empty of pressure oil. Thus, different quantities of pressure oil are required, after a shifting operation in time of starting the vehicle and after a shifting operation during a run, at an initial stage of an operation to engage the hydraulic clutch and immediately before a clutch engagement while reducing time consumed in engaging the hydraulic clutch.
Conventionally, the above set time is extended for a gear shifting operation performed when starting the vehicle, and shortened for a gear shifting operation performed during a run. After a shifting operation performed when starting the vehicle and after a shifting operation performed during a run, different quantities of pressure oil (pressurizing characteristics) are obtained during the set time at an initial stage of the operation to engage the hydraulic clutch from start of the clutch engaging operation. Depending on whether the shifting operation is performed when starting the vehicle or during a run, the time required after the shifting operation to engage the hydraulic clutch is appropriately shortened, while suppressing a shock occurring with a clutch engagement.
However, the quantity of pressure oil drained from the hydraulic clutch during a shifting operation carried out by operating the actuator is variable with the duration of the shifting operation and viscosity of the pressure oil. The quantity of pressure oil supplied to the hydraulic clutch per unit time after the shifting operation is variable with the viscosity and flow rate of the pressure oil. In the prior art noted above, only the set time is varied for a shifting operation performed when starting the vehicle and a shifting operation performed during a run. It is impossible to carry out an appropriate operation to engage the hydraulic clutch by taking the duration of the shifting operation and the viscosity and flow rate of pressure oil into account.
SUMMARY OF THE INVENTION
An object of this invention is to provide a hydraulic change speed system for a working vehicle having an excellent shifting performance with a hydraulic clutch engageable appropriately after a gear shifting operation, which is achieved by taking the duration of the shifting operation and the viscosity and flow rate of pressure oil into account, and considering various factors overlooked in conventional hydraulic change speed systems.
Another object of this invention is to reduce a dead time from completion of a shifting operation with a finish of actuator operation to a clutch engagement.
The above objects are fulfilled, according to this invention, by a hydraulic change speed system as noted in the outset hereof, comprising a time measuring device for measuring a shifting time of the gear type change speed device, wherein, based on the shifting time measured, the controller sets a predetermined time for pressurizing the hydraulic clutch rapidly from a start of engagement of the hydraulic clutch.
The longer time the shifting operation by the actuator takes, the longer time is consumed in the disengaging operation of the hydraulic clutch by the depressurizing action of the valve unit started with a start of operation of the actuator. This increases the quantity of pressure oil drained from the hydraulic clutch. A correspondingly increased quantity of pressure oil is needed to operate the hydraulic clutch appropriately until immediately before a clutch engagement during an initial stage of an operation to engage the hydraulic clutch. The system according to this invention takes this fact into account. The longer the time taken in the shifting operation is as measured by the time measuring device, the longer time is set by the controller for opening the valve unit. Thus, an increased quantity of pressure oil is obtained during the predetermined time. The quantity of clutch operating pressure oil increased with the length of time of the shifting operation is attained promptly for appropriately operating the hydraulic clutch until immediately before a clutch engagement. This effectively avoids a dead time produced by the opening degree of the valve unit restricted from a stage considerably before a clutch engagement to pressurize the hydraulic clutch gradually, which would occur where the predetermined time is fixed despite an extended time for shifting the gear type change speed device by the actuator.
Conversely, the shorter time the shifting operation by the actuator takes, the shorter time is consumed in the disengaging operation of the hydraulic clutch by the depressurizing action of the valve unit started with a start of operation of the actuator. This decreases the quantity of pressure oil drained from the hydraulic clutch. A correspondingly decreased quantity of pressure oil is needed to operate the hydraulic clutch appropriately until immediately before a clutch engagement during an initial stage of an operation to engage the hydraulic clutch. The shorter the time taken in the shifting operation is as measured by the time measuring device, the shorter time is set by the controller for opening the valve unit. Thus, a decreased quantity of pressure oil is obtained during the predetermined time. The quantity of clutch operating pressure oil decreased with the length of time of the shifting operation is attained promptly for appropriately operating the hydraulic clutch until immediately before a clutch engagement. This effectively avoids a shock produced by engagement of the hydraulic clutch occurring during the predetermined time where the predetermined time is fixed despite a shortened time for shifting the gear type change speed device by the actuator.
That is, in engaging the hydraulic clutch after a shifting operation of the gear type change speed device by
Fukumoto Toshiya
Hattori Akio
Machida Satoshi
Okano Akihisa
Bonck Rodney H.
Kubota Corporation
Le David D.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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