1. Field of the Invention
The present invention relates to a multi-plate type friction engaging apparatus used in an automatic transmission of a vehicle and the like, and more particularly, it relates to a bush used in such a multi-plate type friction engaging apparatus.
2. Related Background Art
In general, in a friction engaging apparatus used in an automatic transmission, a housing or drum having a clutch portion is supported rotatably with respect to an inner race or a shaft. A bush as a bearing is interposed between the drum and the shaft.
Such a friction engaging apparatus is disclosed in Japanese Patent Application Laid-open No. 8-261247 (1996) in which a bush is provided between a housing or power transmitting drum and an inner race.
In recent years, due to the fact that a high speed and compactness of a vehicle have been realized and the number of stages of the automatic transmission has been increased, a high speed rotation of a rotary member of a clutch used in the automatic transmission is requested. Thus, an amount of heat generated in a bearing for supporting the friction engaging apparatus is increased, with the result that there arises a problem regarding seizure of the bush.
Thus, an object of the present invention is to provide a multi-plate type friction engaging apparatus and a bush used in such a multi-plate type friction engaging apparatus, which can reduce an amount of heat generated in sliding areas of the bush and seizure of the bush.
To achieve the above object, the present invention provides a multi-plate type friction engaging apparatus in which a power is transmitted by engagement of plural friction elements housed in a housing and wherein it comprises a hub provided on an inner periphery of the housing and a bush interposed between the hub and a shaft on which the hub is slid, and a groove extending in an axial direction is formed in an outer peripheral surface of the bush.
Further, to achieve the above object, the present invention also provides a bush which is used in a multi-plate type friction engaging apparatus for transmitting a power by engagement of a plurality of friction elements housed in a housing and which is interposed between a hub provided on an inner periphery of the housing and a shaft on which the hub is slid and wherein a groove extending in an axial direction is formed in an outer peripheral surface or outer and inner peripheral surfaces of the bush.
Since the groove(s) are formed in the outer peripheral surface or the outer and inner peripheral surfaces of the bush, lubricating oil supplied from the shaft passes through the groove(s) and absorbs heat from the outer diameter portion of the bush, thereby preventing or reducing seizure in sliding areas.
Further, since the groove extending in the axial direction is formed in the outer peripheral surface of the bush, the lubricating oil which was supplied from the shaft and which cooled the outer diameter portion of the bush is supplied to a clutch side of the friction engaging apparatus efficiently, with the result that a smooth operation of the friction engaging apparatus can be obtained and the endurance to the seizure can be extended.
Further, the multi-plate type friction engaging apparatus 50 includes a piston 6 which serves to urge and firmly connect the separator plates 2 and the friction plates 3 (which constitute a clutch portion 30) in the axial direction, and a stop ring 4 provided on the inner periphery of the housing 1 to hold axial one ends (corresponding to the open end of the housing 1) of the separator plates 2 and the friction plates 3 via a packing plate 5 in a fixed condition.
A coned disc spring 7 for providing pre-pressure is interposed between the separator plate 2 nearest to a closed end of the housing 1 and the piston 6. That is to say, the piston 6 serves to tighten the clutch portion 30 via the coned disc spring 7.
As shown in
Predetermined pressurized oil is supplied to the hydraulic chamber 10 via an oil path (not shown) from an oil supply path 19 formed within a shaft or output shaft 9 and connected to a pressurized oil source (not shown), thereby shifting the piston 6 in the axial direction in order to tighten the clutch portion 30. When the oil pressure in the hydraulic chamber 10 is released, the piston 6 is returned to its original position by a biasing force of a return spring 11 disposed between a canceller 8 and the piston 6, thereby releasing the tightening of the clutch portion 30.
In the multi-plate type friction engaging apparatus 50 so constructed, the clutch is engaged and disengaged as follows.
From this condition, in order to engage the clutch, the pressurized oil is supplied to the hydraulic chamber defined between the piston 6 and the housing 1. As a result, by the oil pressure, the piston 6 is shifted to the right along the axial direction in opposition to the biasing force of the return spring 11 to closely contact the separator plates 2 with the friction plates 3. In this way, the clutch is engaged.
In order to disengage the clutch, the pressurized oil is removed from the hydraulic chamber 10. When the pressurized oil is removed, the piston 6 is shifted by the biasing force of the return spring 11 until the piston 6 abuts against the closed end of the housing 1. In this way, the clutch is disengaged.
Next, a bush 20 used in the multi-plate type friction engaging apparatus 50 according to the present invention will be fully explained with reference to
On the other hand, the oil flow B shown by the arrow B passes through the groove 21 of the bush 20 and is directed toward the clutch portion 30 to lubricate the clutch portion 30. Further, the lubricating oil is also directed toward a space between the bush 20 and the output shaft 9 to lubricate an interface therebetween. The groove 21 and grooves 22 to 25 (described later) also serves as paths for lubricating oil lubricating other parts.
FIGS. 3 to 6 are partial perspective views for explaining examples of groove(s) formed in the outer peripheral surface or inner and outer peripheral surfaces of the bush 20.
Similar to the example shown in
As can be seen from
In the above-mentioned multi-plate type friction engaging apparatus, although the plural grooves are formed in the bush along the circumferential direction, the number of the grooves may be selected voluntarily, and a single groove may be used. Further, the grooves can be formed in the outer peripheral surface or inner and outer surfaces of the bush, and all of the grooves can be formed in only the outer peripheral surface or formed in both inner and outer surfaces, or grooves having different shapes can be combined. Further, it should be noted that the circumferential width and depth of the groove can be selected voluntarily. In addition, the grooves can be formed by press working or cutting working.
This application claims priority from Japanese Patent Application No. 2005-014423 filed on Jan. 21, 2005, which is hereby incorporated by reference herein.
Number | Date | Country | Kind |
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2005-014423 | Jan 2005 | JP | national |