Oil filtering device for motor bicycle

Abstract: An oil filtering device (1) for use in a swing-type power unit (8) of a motor bicycle (2) having a four-stroke-cycle engine (4) including a crank case (26), comprises an oil pan (12) for storing oil (11), an oil pump (18) for conveying the oil (11) in the oil pan (12) to engine portions such as a crank shaft (16) involving friction, a lubrication passage through which the oil (11) conveyed by the oil pump (18) is supplied to the engine portions involving friction, an oil strainer (22) provided in the lubrication passage (20) for first filtering the oil (11), and an oil filter (24) for further filtering the oil (11) which has been filtered by the oil strainer (22). The oil (11) to be fed to the crank shaft (16), for example, involving friction is conveyed by way of the oil strainer (22) and the oil filter (24) through the lubrication passage (20) before being supplied thereto. The oil strainer (22) and the oil filter (24) are arranged below and spaced apart from the crank shaft (16) and detachably provided on a surface of the crank case (26) composed of two halves. The swing-type power unit (8) is provided with a suspension arm (8a) having a suspension boss (29) to which the oil filter (24) is provided.

Description: BACKGROUND OF THE INVENTION The present invention relates to an oil filtering device for a motor bicycle and, more specifically, to an oil filtering device for use in a swing-type power unit of a scooter having a four-stroke-cycle engine. Fig. 10 shows an engine 100 having a conventional oil filtering device 101 for a scooter. With this oil filtering device 101, a lubricating oil 102, the flow of which is indicated by arrows in an oil pan, is conveyed to a crank shaft 105 by an oil pump 104 immediately after any relatively large particles of dirt have been filtered out therefrom by an oil strainer 103, serving as a first filtering section, provided on the lower surface of the engine 100. Thereafter, the oil is conveyed to portions of the engine 100 at which a friction occurs, for example, a connecting rod 107 and a cylinder head 108, through a centrifugal oil filter 106 provided on the crank shaft 105 and serving as a second filtering section. The mounting of the oil strainer 103, which is detachably provided on the lower surface of the engine 100, is rather troublesome. Further, since the centrifugal oil filter 106 is formed on the crank shaft 105, its mounting is also rather troublesome. Further, the crank shaft 105, on which the centrifugal oil filter 106 is provided, is subjected to strong vibrations during travelling, so that the oil 102 supplied to the crank shaft 105 is liable to be mixed with air, which results in that the lubricating performance of the lubricating oil 102 is liable to deteriorate. In addition, since the centrifugal oil filter 106 is situated above and spaced apart from the oil strainer 103, the load on the oil pump 104 due to the weight of dust, dirt, etc. which has not been filtered out by the oil strainer 103 is considerably large, which also is not desirable from the viewpoint of the lubricating performance of the lubricating oil 102. SUMMARY OF THE INVENTION An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art and to provide an oil filtering device for a scooter capable of facilitating the replacement of the filtering sections for filtering lubricating oil, such as the strainer and improving the durability of the crank shaft by making the lubricating function of the oil less subject to deterioration. This and other objects of the present invention can be achieved by providing an oil filtering device for use in a swing-type power unit of a motor bicycle having a four-stroke-cycle engine including a crank case, the oil filtering device comprising: an oil pan for storing an oil; an oil pump for conveying the oil in the oil pan to engine portions including a crank shaft involving friction; a lubrication passage means through which the oil conveyed by the oil pump is supplied to the engine portions involving friction; a first filtering section provided in the lubrication passage for first filtering the oil; and a second filtering section for further filtering the oil which has been filtered by the first filtering section, wherein the oil to be fed to the engine portions including the crank shaft involving friction is conveyed by way of the first and second filtering sections before being supplied thereto, the first and second filtering sections being arranged below and spaced apart from the crank shaft and detachably provided on a surface of the crank case. In a preferred embodiment, the first filtering section is an oil strainer and the second filtering section is an oil filter, both the oil strainer and oil filter being arranged in the crank case. The crank case is composed of right- and left-hand case halves to either one of which the oil strainer and the oil filter are arranged. The oil strainer is disposed to the oil pan at its lowermost portion directly below the location of the crank shaft. The swing-type power unit is provided with a suspension arm having a suspension boss to which the oil filter is provided. The lubrication passage means comprises a first passage extending from the first filtering section, a main passage which has an upstream end connected to a downstream end of the first passage and which crosses the crank shaft substantially at a central portion thereof in grade separation and linearly extends along a longitudinal dimension of a motor bicycle body, a second passage connected to a downstream end of the main passage and extending toward the second filtering section and a third passage extending from the second filtering section. According to the structures and characters of the oil filtering device for a motor bicycle, particularly a scooter, of the present invention, the first and second filtering sections are situated below and spaced apart from the crank shaft, one of the engine portions including the crank shaft involving friction, so that they are less subject to the influence of the vibrations of the crank shaft during the travelling thereof than that in the prior art. Furthermore, since the first and second filtering sections are detachably provided on the right- or left-hand side surface of the crank case, they can be easily mounted to the scooter without requiring any special posture by the maintenance technician. In addition, due to the provision of the second filtering section in the suspension boss of the crank case, the rigidity of the second filtering section can be enhanced. The nature and further features of the present invention will be made more clear from the following descriptions made in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: Fig. 1 is an overall side view of a scooter provided with a four-stroke-cycle engine on which a swing-type power unit using the oil filtering device of the present invention is mounted; Fig. 2 is a plan view of the four-cycle-engine scooter of Fig. 1; Fig. 3 is a left-hand side view of the swing-type power unit with a rear wheel attached thereto; Fig. 4 is a left-hand side view of the swing-type power unit, partially cut away; Fig. 5 is a diagram showing the swing-type power unit with a smaller case section thereof removed and its oil pan containing oil; Fig. 6 is a right-hand side view of the swing-type power unit, partially cut away; Fig. 7 is a schematic sectional view taken along line VII-VII of Fig. 4 showing the lubrication route of the lubricating oil conveyed from the oil strainer to the oil filter; Fig. 8 is a schematic sectional view taken along lines VIII-VIII of Fig. 5, showing the lubrication route of the lubricating oil conveyed from the oil filter to the crank shaft; Fig. 9 is a schematic diagram showing the lubrication route of the lubricating oil conveyed from the oil strainer to the crankshaft by way of the oil filter; and Fig. 10 is a schematic diagram for illustrating a conventional structure of an oil filtering device for a scooter. DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will be described hereunder in detail with reference to the accompanying drawings. Referring to Figs. 1 and 2, a scooter 2 has a swing-type power unit 8 consisting of a four-stroke-cycle engine 4 and a transmission 6, which form an integral unit. The swing-type power unit 8 is mounted on a vehicle body frame through the intermediation of a suspension arm 8a provided in the front section thereof. Further, a rear section 8b thereof is attached to the vehicle body frame through the intermediation of a rear cushion 8b. The engine 4 of the power unit 8 is provided with the oil filtering device. As shown in Fig. 3, the oil filtering device comprises an oil pan 12 for storing oil 11, an oil pump 18 for sucking the oil 11 in the oil pan 12 to feed it in a pressurized state to the portions of the engine 4 involving friction, such as a crank shaft 16 and a connecting rod, not shown, a lubrication passage 20 for conveying the oil 11 fed by the oil pump 18 to the crank shaft 16, etc., an oil strainer 22 provided in the lubrication passage 20 and serving as a first filtering section to filter the oil 11 in the oil pan 12, and an oil filter 24 serving as a second filtering section for further filtering the oil 11 which has been filtered by the oil strainer 22, these components of the oil filtering device being contained in a crank case 26. The crank case 26 consists of a larger case section 26a provided on a right-hand side with respect to the travelling direction of the vehicle, and a smaller case section 26b provided on a left-hand side of the same. The oil filtering device 1 is arranged in the larger case section 26a. As can be seen from Figs. 3 and 5, the oil pan 12 is provided in the lowest section of the larger case section 26a. The crank shaft 16 is rotatably supported inside the larger case section 26a by means of ball bearings 17 and has in its interior a main gallery 20a extending in parallel with the axis thereof and constituting a part of the lubrication passage 20. The oil 11, the flow of which in the lubrication passage 20 is indicated by the arrows and which is being pressurized by the oil pump 18, is forced out of the main gallery 20a and supplied to the connecting rod, etc. The oil pump 18 is situated at a position to the front of the oil pan 12 and somewhat higher in the level than the oil surface in the oil pan. As shown in Fig. 7, for example, the lubrication passage 20 is formed in such a way as that the oil 11 in the oil pan 12 is supplied to the cylinder head 16, etc. after being conveyed by way of the oil strainer 22 and the oil filter 24. As can be seen from Figs. 7 and 9, the lubrication passage 20 comprises a passage 20b extending from the oil strainer 22 and having a substantially L-shaped angle configuration, a main passage 20c whose rear end is connected to the front end 20b' of the passage 20b and which crosses the crank shaft 16 substantially at the central portion thereof in grade separation and linearly extends along the longitudinal dimension of the vehicle, a passage 20d connected to the front end 20c' of the main passage 20c and extending toward the oil filter 24, and a passage 20e extending from the oil filter 24 to communicate with the main gallery 20a. The oil strainer 22 and the oil filter 24 are arranged below and spaced apart from the crank shaft 16. More specifically, as is apparent from Figs. 3, 5 and 8, the oil strainer 22 is adjacent to the lowest section of the oil pan 12 and situated substantially directly below and somewhat spaced apart from the crank shaft 16. Further, the oil strainer 22 communicates with the oil pan 12 through a small hole 28. The oil filter 24 is arranged in a suspension boss 29 provided substantially at the center of the suspension arm 8a. The oil strainer 22 and the oil filter 24 are detachably provided on the right-hand side surface 26a of the crank case 26. It is also possible for them to be provided in a similar fashion on the left-hand side surface 26b of the crank case 26. The oil strainer 22 and the oil filter 24 are provided with covers 22a and 24a, respectively, through which they can be mounted to the crank case 26. The operation and effects of the oil filtering device 1 for a scooter of the present invention, constructed as described above, will be described hereunder. When the oil 11 in the oil pan 12, communicating with the oil strainer through the small hole 28, is sucked by the oil pump 18, any relatively large particles of dirt are first filtered out by the oil strainer 22. Then, the oil is fed to the oil filter 24 by way of the passage 20b, the main passage 20c and the passage 20d. The oil filter 24 filters out any fine particles of dust, etc. which have not been filtered out by the oil strainer 22. Thereafter, the oil enters the main gallery 20a by way of the passage 20e, and is then supplied to the engine portions involving friction through an oil hole of the crank shaft 16. According to the oil filtering device 1 for a scooter, since the oil fed to the engine portions involving friction, including the crank shaft 16, is supplied thereto after being conveyed by way of the oil strainer 22 and the oil filter 24, the oil can be made clean through duplicated filtering process. Furthermore, since the oil strainer 22 and the oil filter 24 are arranged below and spaced apart from the crank shaft 16, they are less subject to the vibrations of the crank shaft 16 during its travelling, so that the lubricating function of the oil is less subject to deterioration, whereby an improvement can be attained in terms of the durability of the crank shaft. In addition, since the oil strainer 22 and the oil filter 24 are detachably provided on the right-hand side surface 26a or the left-hand side surface 26b of the crank case 26, they can be easily mounted to the scooter 2 without requiring any special posture by the maintenance technician. Thus, the replacement of the filtering sections for filtering the oil 11, including the oil strainer 22, can be facilitated. Furthermore, since the second filtering section is provided in the suspension boss of the crank case, the rigidity of the second filtering section is enhanced, thereby making the device less subject to trouble.

Claims: An oil filtering device for use in a swing-type power unit (8) of a motor bicycle having a four-stroke-cycle engine (4) including a crank case (26) , the oil filtering device comprising: an oil pan (2) for storing an oil; an oil pump (18) for conveying the oil in the oil pan to engine portions including a crank shaft ( 16 ) involving friction; a lubrication passage means (20) through which the oil conveyed by the oil pump is supplied to said engine portions; a first filtering section (22) provided in said lubrication passage for first filtering the oil; and a second filtering section (24) for further filtering the oil which has been filtered by the first filtering section, characterised in that the oil to be fed to said engine portions is conveyed by way of the first and second filtering sections (22,24) before being supplied thereto, the first and second filtering sections being arranged below and spaced apart from the crank shaft (16) and being detachably provided on a surface of the crank case (26) . An oil filtering device according to claim 1, wherein said first filtering section is an oil strainer (22) and said second filtering section is an oil filter ( 24) , both the oil strainer and oil filter being arranged in the crank case (26). An oil filtering device according to claim 1 or 2, wherein said crank case is composed of right- and left-hand halves (26a,26b) to either one of which said oil strainer and said oil filter are detachably provided. An oil filtering device according to claim 1, 2 or 3 wherein said oil strainer (22) is disposed to the oil pan (2) at its lowermost portion directly below the location of the crank shaft. An oil filtering device according to claim 2, or claim 3 or 4 when dependent on claim 2, wherein the swing-type power unit (8) is provided with a suspension arm ( 8a ) having a suspension boss (29) to which the oil filter is provided. An oil filtering device according to claim 2, or claim 3, 4 or 5 when dependent on claim 2, wherein said oil strainer (22) and said oil filter (24) are provided with covers (22a,24a) for facilitating attachment thereof to the crank case (26) . An oil filtering device according to any preceding claim 4, wherein said lubrication passage means (20) comprises a first passage (20b) extending from the first filtering section, a main passage ( 20)c which has an upstream and connected to a downstream end (20b') of the first passage and which crosses the crank shaft substantially at a central portion thereof in grade separation and linearly extends along a longitudinal dimension of a motor bicycle body, a second passage (20d) connected to a downstream end of the main passage and extending toward the second filtering section, and a third passage (20e) extending from the second filtering section.

Inventors: ARAKAWA HIDETOSHI, ARAKAWA, HIDETOSHI
Applicants: SUZUKI CO LTD, SUZUKI KABUSHIKI KAISHA
Application year: 1993
Main classification: F01M11
IPC codes: F02F1, F01M11, F02B75, F02B61