Motors: expansible chamber type – Three or more cylinders arranged in parallel radial or... – Radially disposed cylinders
Patent
1998-06-25
2000-04-18
Thorpe, Timothy S.
Motors: expansible chamber type
Three or more cylinders arranged in parallel radial or...
Radially disposed cylinders
91482, F01B 106, F03C 136
Patent
active
060501731
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a cam motor apparatus used as a motor for traveling a construction machine or a motor for other purposes, and specifically relates to a cam motor apparatus configured such that the motor capacity is changed between large and small stages so that the rotation is changed between a low-speed mode rotating at low speed and a high-speed mode rotating at a speed higher than that in the low-speed mode.
BACKGROUND ART
As a cam motor apparatus of such kind, there is known a conventional cam motor apparatus configured such that a plurality of pistons and cylinders are divided into four groups and the condition of distribution of working oil to the pistons and cylinders included in each group is changed between two stages through the operation of a selector valve (See, for example, FIG. 2 in Japanese Patent Application Laid-Open Gazette No. 55-153871). In this motor, when the selector valve is changed to a low-speed mode, working oil is supplied to each cylinder included in two groups selected from among the four groups, whereas each cylinder included in the other two groups is connected to an oil tank so as to discharge working oil thereto. Thereby, the motor capacity of the cam motor apparatus becomes a maximum value so that the motor is rotated at relatively low speed and high output torque.
On the other hand, when the selector valve is changed to a high-speed mode, working oil is supplied to each cylinder included in one of the selected two groups, working oil is discharged from each cylinder included in one of the other two groups, and cylinders included in the remaining two groups are connected to each other to form a closed circuit. Thereby, the motor capacity becomes half the value in the low-speed mode so that high-speed rotation is made at a speed approximately twice as fast as the low-speed mode.
In the conventional cam motor apparatus above-described, however, since each cylinder included in the two groups in which neither oil supply nor oil discharge is made in the high-speed mode has a closed circuit, no escape route is left for pressurized oil in the cylinder so that large resistance to the motor rotation may be produced. To cope with this, it can be considered that each cylinder included in the above-mentioned two groups is communicated with the oil tank. In this case, however, the oil pressure of each cylinder included in the two groups becomes close to the atmospheric pressure so that slide contact between the piston and the cam surface in the cylinder cannot be held by the oil pressure. As a result, undesirable beat sounds are produced due to collision between the piston and the cam surface, and the piston and the cam surface are decreased in durability.
To eliminate the above problems, it is necessary to dispose a spring between the piston and the bottom surface of the cylinder room as in the conventional cam motor apparatus so as to press the piston against the cam surface by the spring. In this case, however, the component count of the apparatus is increased. This increases the weight of the apparatus and complicates the structure thereby involving much expense in time and effort for assembly.
In view of the foregoing problems, the present invention has been made. Therefore, an object of the present invention is to hold slide contact between the piston and the cam surface thereby increasing silentness and durability and to decrease component count thereby reducing weight and increasing ease of assembly.
DISCLOSURE OF THE INVENTION
To attain the above object, in the present invention, pressurized oil is supplied from a charging pump, provided for supplying working oil to the working oil supply system of the cam motor apparatus so as to cope with leakage of the working oil, to the piston which falls into a state that no driving force is produced in a high-speed mode. As a result, slide contact between the piston and the cam surface can be held.
More specifically, as shown in FIGS. 1 and 2, the present invention premises a cam motor apparatus compris
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patent: 4898076 (1990-02-01), Bigo et al.
patent: 5220790 (1993-06-01), Allart et al.
patent: 5435135 (1995-07-01), Lallier et al.
Kotake Yoichiro
Naruse Toshihiro
Sakai Toshiyuki
Suhara Masaaki
Daikin Industries Ltd.
Robinson Eric J.
Studebaker Donald R.
Thorpe Timothy S.
Torrente David J.
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