Machine element or mechanism – Gearing – With fluid drive
Patent
1990-11-29
1993-03-16
Braun, Leslie A.
Machine element or mechanism
Gearing
With fluid drive
747301, 747321, 74880, 475 72, 475 78, 475 80, 60490, F16H 4700, F16D 3900
Patent
active
051934167
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a mechanical-hydraulic transmission gear system and a method of controlling power transmission using the gear system, more particularly this invention relates to a power transmission system for use in construction vehicles or construction equipment such as wheel type power shovels and rough terrain cranes, etc and a method of controlling power transmission using the gear system, wherein when the prime mover thereof is rotating at high speeds, the power loss due to fluid pressure is reduced substantially to zero so as to avoid a lowering in power transmission efficiency, and power transmission is effected only through the mechanical transmission gear so as to improve tractive force. When the prime mover is rotating at low speeds, speed control and control of change-over from forward rotation to reversing and vice versa can be made readily, and power transmission is effected only through the hydraulic transmission gear so as to improve the composite maneuverability of implement.
BACKGROUND ART OF THE INVENTION
As the power transmission gear of construction equipment, etc. the following systems have heretofore been used.
In the mechanical-hydraulic power transmission system (HMT), part of the power is transmitted mechanically and the rest of the power is transmitted hydraulically; in other words, a power division type hydraulic transmission system (hydraulic-mechanical power transmission), among which an output division type as shown in FIG. 1 is well known.
However, in the above-mentioned prior art transmission gears, the mechanical power transmission system is excellent in power transmission efficiency, but poor in the control of change-over from forward running to reversing and vice versa. The hydraulic power transmission system (Refer to FIG. 2) is capable of effecting control of change-over from forward rotation to reversing and vice versa, by varying the tilting angle of swash plates of a variable displacement hydraulic pump 51 and a variable displacement hydraulic motor 52. The system and therefore can be operated easily, and is also capable of changing the rotational speed of the output shaft by engagement between gears 53 and 54, engagement between gears 55 and 56 and change-over between clutches 57 and 58. However, such a system is disadvantageous in that when the output shaft is rotating at high speeds the tilting angle of the swash plate of the pump 51 is increased to increase the discharge flow-rate of fluid thus increasing the pressure loss, while the tilting angle of the swash plate of the motor 52 is reduced thus causing a lowering in efficiency. For this reason, when the output shaft of the mechanical-hydraulic power transmission system (Refer to FIG. 1) is rotating at high speeds mechanical power transmission is effected so as to avoid lowering in efficiency. While when the output shaft is rotating at low speeds, hydraulic power transmission is effected so as to facilitate control of change-over from forward rotation to reversing and vice versa. This type of system has been used in various fields.
In FIG. 1, an input shaft 62 is connected to a prime mover 61, and an intermediate portion of the input shaft 62 has a gear 64 fixedly secured thereto and which meshes with a hydraulic pump driving gear 63. Further, a sun gear 65 of a planetary gear device A is fixedly secured to one end of the input shaft 62. The hydraulic pump driving gear 63 is arranged to drive a variable displacement type pump 66 of a hydraulic transmission gear B provided on one side of the input shaft of driving gear 63. This variable displacement type pump 66 is arranged to actuate a fixed displacement motor 67 mounted in juxtaposition thereto and parallel with the axis of the input shaft 62. This fixed displacement motor 67 has an output shaft provided with a gear 68 to which the power developed by the motor 67 is transmitted. The gear 68 is arranged to rotatively drive an internal gear 69-1 of the planetary gear device A through a gear 69 which meshes therewit
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Braun Leslie A.
Henn David E.
Kabushiki Kaisha Komatsu Seisakusho
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