Engine-overrun-preventing control device for work vehicle

Abstract

An engine-overrun-preventing control device for a work vehicle, the purpose of said control device being to prevent engine overrun without advancing the action of a mechanical brake and to minimize energy loss, thereby solving problems such as poor fuel efficiency and losses in brake-device cooling capacity. If an actual engine speed detected by an engine-speed detection means has exceeded the maximum speed of the engine, a minimum inching ratio is set such that the higher said actual engine speed is, the higher the minimum inching ratio is set, and the displacement of an HST hydraulic pump is adjusted so as to obtain whichever of the following inching ratios is higher: the aforementioned minimum inching ratio set in accordance with the actual engine speed; or an inching ratio set by an inching-ratio setting means in correspondence with the brake stroke of a brake control means. If the actual engine speed detected by the engine-speed detection means has exceeded a commanded engine speed and the rate of change over time of the pressure at the intake side of the HST hydraulic pump is greater than or equal to a prescribed rate, as measured by a pressure time-rate-of-change measurement means, a minimum inching ratio is set such that the higher said rate of change over time of pressure is, the higher the minimum inching ratio is set, and the displacement of the HST hydraulic pump is adjusted so as to obtain whichever of the following inching ratios is higher: the minimum inching ratio set in accordance with the aforementioned rate of change over time of pressure; or the inching ratio set by the inching-ratio setting means in correspondence with the brake stroke of the brake control means.

Description

technical field [0001] The invention relates to an engine overspeed prevention control device of a work vehicle equipped with a hydrostatic transmission (HST; Hydro-Static Transmission). Background technique [0002] Such as figure 1 As shown, among work vehicles 1 such as a forklift, there is a work vehicle equipped with a hydrostatic transmission (HST; Hydro-Static Transmission) 17 . In such work vehicle 1 , the gears are changed by adjusting the inclination angles of the swash plate 16 c of the HST hydraulic pump 16 and the swash plate 18 c of the HST hydraulic motor 18 constituting the HST 17 to change the capacities. [0003] In the work vehicle 1 on which the HST is mounted, an accelerator operating mechanism (for example, an accelerator pedal) 25 , a brake operating mechanism (for example, a brake pedal) 26 , and a working machine operating lever 6 are provided. When the accelerator operating mechanism 25 is stepped on and operated, the engine 8 is controlled so tha...

AI Technical Summary

Problems solved by technology

[0017] The present invention was made in view of these actual conditions, and its object is to prevent the engine from overspeeding without advancing the action of the mechanical brake, thereby suppressing energy loss, and solving the problems of reduced fuel efficiency and low cooling capacity of the brake device

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