Oil strainer for transmission

Abstract

An oil strainer for a transmission including a resin-made upper case which is formed in a side surface of an upper part of a communication port for communication with a pump and which has an upper flange along the outer periphery thereof, a resin-made lower case which is provided with an oil suction port in a lower surface thereof and which has a lower flange joined to the upper flange of the upper case, and a filter member which is disposed in a space formed by joining the upper and lower cases and which filters an oil flowing from the oil suction port to the communication port. The oil strainer is configured to further includes an oil suction port cover member which is so formed as to cover at least an inside upper surface of the oil suction port and which forms a passage for conducting the oil to the filter member.

Description

[0001]This is a continuation of International PCT Application NO. PCT / JP2007 / 057235, filed Mar. 30, 2007, which was not published in English.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an oil strainer for filtering an oil in a transmission case.[0004]2. Description of the Related Art[0005]An oil used as a working fluid or a lubricating oil in a transmission is reserved in a lower part of a transmission casing, is sucked by an oil pump and is supplied to a control valve and other parts to be lubricated. In this case, it is a common practice to disposed an oil strainer in the lower part of the transmission casing and to filter the oil through the strainer before the oil is sucked by the pump. A configuration in which a filter member formed from a non-woven fabric or the like is disposed in a resin-made case to form the oil strainer has been known. In this case, the filter member composed of the non-woven fabric is clamped between an...

AI Technical Summary

Benefits of technology

[0010]Accordingly, it is an object of the present invention to provide an oil strainer for a transmission which is simple in structure and with which it is possible to reduce the total amount of oil and to restrain aeration from being generated.

[0012]According to this configuration, the end position of the oil suction port in the oil conducting direction constitutes a dominant factor in setting the oil surface at the time of a change in the oil surface. Therefore, it is possible to reduce the total amount of the oil in the transmission, and to enhance aeration toughness at the times of changes in the oil surface which are generated at the times of acceleration and deceleration of the vehicle.

[0013]Preferably, the oil suction port cover member is so formed as to cover the left and right sides and the rear side of the oil suction port or the left and right sides and the front side of the oil suction port, as viewed along the forward vehicle running direction. This ensures that the oil flowing in through the oil suction port can be efficiently conducted to the filter member. Preferably, both an end position of the oil suction port in the direction for conducting the oil by the oil suction port cover member and the total amount of the oil in the transmission are so determined that the end position of the oil suction port is located substantially at the intersection between an oil surface at the time of a maximum vehicle acceleration and an oil surface at the time of a maximum vehicle deceleration.

[0014]When the total amount of the oil in the transmission is determined so that the end position of the oil suction port is located substantially at the intersection between the oil surface at the time of a maximum vehicle acceleration and an oil surface at the time of a maximum vehicle deceleration to lower the oil surface as much as possible, it is possible to reduce the total amount of the oil in the transmission, to realize a reduction in weight, and to restrain aeration through a reduction in the oil agitation resistance of gears. Consequently, an improvement in fuel economy can be expected through a reduction of friction.

[0017]According to the configuration as above-mentioned, it is possible to restrain the generation of aeration and to efficiently conduct the oil to the filter member, while minimizing the total amount of the oil required for the transmission.

Problems solved by technology

In the oil strainer disclosed in Japanese Patent Laid-open No. 2001-124188, complete removal of the rib formed along the whole circumference of the flange constituting the joint part between the upper case and the lower case is difficult in view of vibration welding of the cases, so that the site for forming the notch is restricted.

Therefore, there remains the problem of, for example, stagnation of air at the four corners of the oil strainer, and fine aeration possibly caused by the stagnating air.

Therefore, it is difficult to secure an aeration balance in each cases of forward running and rearward running.

In addition, in view of the structure in which a main oil passage to the oil suction port of the strainer is along the forward vehicle running direction, the system in which the strainer is inclined along the front-rear direction leaves some air stagnation area in the oil passage, again causing the fine aeration.

Therefore, when the total amount of the oil in the transmission is large, the weight thereof is also large accordingly, and there is a fear of generation of aeration due to an increase in oil agitation resistance of gears or a fear of worsening of fuel economy attendant on an increase in friction.

If the spacing in the vehicle running direction of the oil suction port formed in the lower case of the oil strainer is narrowed as a countermeasure against the problem mentioned just above, the resistance at the time of sucking the oil would be increased, so that the hydraulic oil in a hydraulic pressure control circuit may be lowered, or the increase in the oil suction resistance may cause an increase in the oil pump driving torque, leading to worsening of fuel economy.

Besides, if the oil suction port is enlarged, aeration toughness at the time of a change in the oil surface would be lowered, so that the total amount of the oil in the transmission must be increased further; thus, a vicious circle is likely to arise.

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