Interrelated power delivery controls – including engine control – Clutch control – Condition responsive control
Reexamination Certificate
2001-08-30
2003-05-20
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Clutch control
Condition responsive control
C477S079000, C477S120000, C701S054000
Reexamination Certificate
active
06565482
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a construction machine such as a motor grader, a rough terrain crane, a power shovel, a wheel loader, a bulldozer and others, or a working vehicle such as a dump truck, a forklift and others, and a speed control method thereof. Further, the present invention relates to a variable power engine capable of changing its power and a power setting method thereof, the engine being used in the above vehicles. Furthermore, the present invention relates to a vehicle with a variable power engine such as described above and a power control method thereof.
2. Description of the Related Art
Recently, in a working vehicle, e.g., a machine such as a motor grader, a gear-contained transmission with an electronically controlled clutch having a gear train and a plurality of hydraulic (fluid pressure) clutches, combination of which can be changed in various ways, is used, and the gear-contained transmission with the clutch controlled by a solenoid operated valve to carry out various operations is increasing.
(Inching Pedal)
In a motor grader, a special work such as leveling the ground by using a blade while turning a corner may be performed. In such a case, a number of revolutions of the engine must be increased in some measure and, in this high velocity revolution, the vehicle speed is also increased from the nature of the case, which makes it difficult to turn a corner while carrying out the necessary work. Therefore, there is a request for reducing the vehicle speed while maintaining the high velocity revolution.
In order to satisfy such a request, a foot-operated inching pedal (clutch pedal) is provided, and stepping on this inching pedal can slide a predetermined clutch of the transmission to decrease the speed, thereby filling the needs of a necessary work and turning a corner and the like.
In case of the working vehicle, when starting the machine from standstill, since starting is possible from a relatively high speed stage as different from a general vehicle, the machine is started at a plurality of speed stage positions. When starting at different speed stage positions in this manner, since an input shaft is different from an output shaft in speed reducing (speed increasing) ratio for each speed stage position, the connection state of the clutch differs even though the inching pedal is stepped on at a similar angle. In other words, when the inching pedal stepping angle is unchanged, the machine can be started and travel at a desired speed at a low speed stage position, whilst the machine can not be started or travel at a lower speed than expected at a higher speed stage position. Therefore, there is a problem that a desired speed can not be obtained unless the inching pedal stepping angle is reduced (unless the pedal is released) at the higher speed stage position.
As a technique for equaling the feel of stepping on the inching pedal which differs in accordance with each speed stage position, there is an invention disclosed in Japanese patent laid-open publication No. Hei 10-246318.
In the invention disclosed in this publication, a solenoid working pressure regulating valve is provided to each clutch constituting each speed stage of the transmission; one solenoid operation manual regulating valve (proportional valve) is provided to some regulating valves out of the above pressure regulating valves on the upstream side; and each valve is controlled by a controller in accordance with an inching pedal stepping angle and a speed stage position, thereby controlling the connecting force of the clutch to be controlled in accordance with a change in the speed stage (selected gear ratio).
According to the invention disclosed in this publication, since the connecting force of the clutch is changed in accordance with the speed stage position, the inching pedal stepping position can be roughly associated with the speed of the machine irrespective of the speed stage position of the transmission, but an input number of revolutions and an output number of revolutions of the transmission are not monitored at all, and the sufficient (detailed) control of the output shaft, i.e., the vehicle speed can not be necessarily performed.
Further, since the pressure regulating valve of each clutch is controlled by one proportional valve provided on the upstream side thereof, there is also such a problem as that the detailed control of each clutch is not necessarily adequate.
(Hyper-slow Mode)
In the motor grader, a work for finishing the road surface or the bank with the extremely high accuracy may be carried out. In such a case, there is a request for realizing the very low speed of, e.g., approximately 1.0 km/h from the necessity of the work.
On the other hand, as to a number of revolutions of the engine, the high speed revolutions in some measures is required from the necessity of the work and, in such a high speed revolution, the vehicle speed is necessarily increased, which makes it difficult to realize the very low speed running while carrying out the necessary work. Therefore, there is a need for decreasing the vehicle speed while maintaining the high speed revolution.
In order to satisfy the above needs, there have been proposed many variable displacement torque converters, i.e., torque converters capable of automatically converting attitudes or shapes of three vanes, namely, an impeller, a turbine vane and a stator of the torque converter in accordance with a range of the high and low speeds.
With the working vehicle having the above-described variable displacement torque converter, running at a very low speed and a predetermined finishing operation can be efficiently carried out.
However, since the variable displacement torque converter has the complicated structure, it is very expensive, resulting in an increase in the price of the vehicle itself.
Further, the rising interest in the recent environmental concerns leads to an issue of noise reduction of the working vehicle.
That is, a number of steady-state revolutions of a conventional engine is determined to be approximately 2,500 RPM and a number of revolutions in the low idling is determined to be approximately 800 RPM.
On the other hand, in view of the noise reduction, a number of steady-state revolutions of approximately 2,000 RPM and a number of revolutions in the low idling of 800 RPM are required. This brings up the following new problem when realizing the very low running such as described above.
That is, if a forward first speed in the first in forward in a conventional number of steady-state revolutions is set to, for example, 3.45 km/h, the vehicle speed in the low idling becomes 1.1 (=3.45×800/2,500) km/h, which is the hyper-slow running with which the finishing work is possible.
Meanwhile, if a number of steady-state revolutions is set to 2,000 RPM without changing the structure of the transmission, the vehicle speed in the low idling becomes 1.38 (=3.45×800/2,000) km/h.
However, the vehicle speed of 1.38 km/h is too high for the finishing work using the motor grader.
Thus, a working vehicle having a simplified structure by which a number of steady-state revolutions of the engine can be reduced and the very low speed running is also enabled is desired.
(Variable Power Engine)
The following can be true to the above-described engine of a working vehicle.
An engine power is usually set so as to obtain a given fixed maximum power. However, there is a request for changing a set value of a maximum power in accordance with circumstances depending on vehicles and machines.
For example, in case of the construction machine, a large power directly relates to the high work efficiency. However, in a low speed range, since the speed decreasing ratio of the transmission is large, a large power may cause the drive force to exceed a road surface adhesive coefficient of a wheel or a crawler and, in such a case, the wheel or the crawler go into a slide. Slippage of the wheel and the like leads to difficulty in the work and the deteriorated drive c
Kobayashi Tetsuo
Nishimaki Kazuhito
Takahashi Hitoshi
Armstrong Westerman & Hattori, LLP.
Estremsky Sherry
Komatsu Ltd.
Lewis Tisha D.
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