192 clutches and power-stop control – Clutch and brake – Vehicle type
Patent
1993-02-22
1994-12-27
Lorence, Richard M.
192 clutches and power-stop control
Clutch and brake
Vehicle type
192 12C, 91521, 91524, 180 62, B62D 1108, F16D 6704
Patent
active
053756860
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for controlling hydraulic steering clutches and brakes used for a crawler vehicle such as a bulldozer.
BACKGROUND OF THE INVENTION
The structures of hydraulic steering clutches and brakes will be explained with reference to FIG. 4. In an actual vehicle, left and right clutches and brakes in pairs are mounted on an axle 9. However, only those on the left side are exemplified in this figure.
During normal advance, the steering clutch 10 is turned on while the brake 11 is turned off so that a power from an input shaft 12 is transmitted to a left output shaft 13 by way of the axle 9 and the left steering clutch 10, and accordingly, a drive sprocket 14 is driven.
In the case of steering, when for example a left steering lever 15 is pulled back from its neutral position, the operation of a hydraulic control valve 17 is started through the intermediary of a link 16, and accordingly, oil from a pump 6 flows into a left clutch piston 7 at a position intermediate of a stroke so that the left steering clutch 10 is turned off.
Thus, the power on the axle is transmitted only to a right output shaft while a left output shaft 13 falls into a free condition, thereby the bulldozer turns moderately to the left.
From this condition, when the left steering lever 15 is pulled further, oil flows also into a left brake cylinder 8 by way of the hydraulic control valve 17 so that the left brake 11 is turned on through the intermediary of a link 18, and accordingly, the left output shaft 13 is made to be stationary, thereby the bulldozer turns sharply to the left.
Incidentally, when a brake pedal 19 is depressed, the left and right brakes are turned on through the intermediary of a link 20, and accordingly, braking is performed in a straight travel condition.
However, such a conventional control device inevitably uses a large size hydraulic control valve which is therefore disposed in an extra space in the vehicle body and which is coupled to the steering lever through a linkage. Accordingly, the structure is complicated, resulting in an increase in manufacturing cost.
Further, in order to enhance the steering ability in a monolever system which is manipulated by a single lever, it is necessary to arrange left and right hydraulic control valves in the vicinity of the steering lever. However, such an arrangement has been difficult for the conventional large size control valve.
The present invention is devised in order to solve the above-mentioned problems inherent to the conventional arrangement, and accordingly, one object of the present invention is to provide a device for controlling hydraulic steering clutches and brakes, which is simple in its structure and which can be manipulated by a monolever.
DISCLOSURE OF THE INVENTION
A device for controlling hydraulic clutches and brakes, according to the present invention, is composed of a single steering lever, four proportional pressure control valves manipulated by the steering lever, and left and right steering clutch pistons and left and right brake cylinders which are connected to the output ports of the proportional pressure control valves by means of conduits.
These four proportional pressure control valves consist of two sets of valves: one set of two proportional pressure control valves for steering clutches, in which the timing of the rise of hydraulic pressure is earlier, and one set of two proportional pressure control valves for brakes, in which the timing of the rise of hydraulic pressure is later than the former.
At first, when the steering lever is tilted, the proportional pressure control valves for steering clutches are operated so as to move the steering clutch pistons to turn off the clutches, accordingly, a moderate turn is performed. When the steering lever is further tilted, the proportional pressure control valves for the brakes are operated to actuate the brake cylinders, and accordingly, braking is effected, thereby a sharp turn is performed. With this arrangement, the steering with the u
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patent: 3747472 (1973-07-01), Knutson
patent: 3830438 (1974-06-01), Kobelt
patent: 5235811 (1993-08-01), Arii et al.
Kabushiki Kaisha Komatsu Seisakusho
Lorence Richard M.
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