Lubrication system for internal combustion engines

Abstract

This invention provides a lubrication system for an internal combustion engine that can improve lubrication performance by separating the oil discharge port of the scavenging pump from the oil intake port of the feed pump. [Solution] An oil pump unit 50 is formed by integrally connecting scavenging pumps 51L and 51R on both sides of a feed pump 51C and driving it with a common pump drive shaft 58. In the lubrication system of an internal combustion engine 10 located below the crankcase 21, the discharge ports 57L and 57R of the scavenging pumps 51L and 51R on both sides are connected by a connecting pipe 70. The oil discharged from the two discharge ports 57L and 57R merge within the connecting pipe 70 and is then discharged from a connecting pipe outlet 70a provided on the connecting pipe 70.

Description

Technical Field

[0001] The present invention relates to a lubrication device for an internal combustion engine.

Background Art

[0002] Some lubrication devices for internal combustion engines are provided with, in addition to a feed pump that supplies oil to each lubrication site of the internal combustion engine, a scavenging pump that draws in oil that has finished lubricating each lubrication site of the internal combustion engine. Among internal combustion engines, there is an example of a lubrication device having a plurality of scavenging pumps (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] In the lubrication device disclosed in Patent Document 1, an oil pump unit in which scavenging pumps are integrally connected to both sides of a feed pump and driven by a common pump drive shaft is disposed below the crank chamber. The crank chamber is a sealed space, and the two scavenging pumps forcibly draw in the oil that has fallen onto the bottom surface of the crank chamber, thereby reducing the stirring resistance caused by residual oil in the crank chamber and reducing the pressure inside the crank chamber, so that the rotational resistance of the crankshaft can be reduced.

[0005] In the oil pump unit disclosed in Patent Document 1, scavenging pumps are integrally connected to both sides of the central feed pump, a suction pipe extends downward from the central feed pump, and a strainer connected to the suction pipe is disposed in the oil pan to draw in oil. On the other hand, the scavenging pumps on both sides of the feed pump each have an oil discharge port on the outer side in the pump drive shaft direction, and discharge oil from the two oil discharge ports to drain it into the oil pan.

[0006] Oil is discharged into the oil pan from the oil outlets of the scavenging pumps on both sides of the oil pump unit, and a strainer extending downward from the feed pump in the center of the oil pump unit draws in the oil stored in the oil pump. [Overview of the project] [Problems that the invention aims to solve]

[0007] When the scavenging pump sucks up oil that has fallen to the bottom of the crankcase, a large amount of air is mixed into the oil. As this oil containing a large amount of air is discharged into the oil pan from the oil outlets of the scavenging pumps on both sides, the oil containing a large amount of air discharged from the oil outlets of the scavenging pumps is injected into both sides of the strainer that draws in the oil stored in the oil pan. Therefore, the oil that the strainer draws in is likely to contain air.

[0008] When oil containing air enters the oil line, even if it is supplied to the lubricating parts, the oil containing air will reduce its lubrication performance.

[0009] The present invention has been made in view of the above, and its objective is to provide a lubrication device for an internal combustion engine that has an oil pump unit in which scavenging pumps are integrally connected on both sides of a feed pump, and in which the lubrication performance can be improved by separating the oil discharge port of the scavenging pump from the oil intake port of the feed pump. [Means for solving the problem]

[0010] To achieve the above objective, the present invention The internal combustion engine comprises a scavenging pump that sucks up oil that has fallen to the bottom of the crank chamber in the crankcase and discharges it to the outside of the crank chamber in the crankcase, and a feed pump that sucks up oil from the oil reservoir and supplies oil to each lubrication part of the internal combustion engine. The scavenging pumps are integrally connected to both sides of the feed pump, forming an oil pump unit driven by a common pump drive shaft. The oil pump unit is a lubrication system for an internal combustion engine, which is located below the crankcase. The discharge ports of the scavenging pumps on both sides are connected by a connecting pipe. The present invention provides a lubrication system for an internal combustion engine, characterized in that the oil discharged from the two discharge ports merges within the connecting pipe and is then discharged from a connecting pipe outlet provided in the connecting pipe.

[0011] In this configuration, the discharge ports of the scavenging pumps on both sides of the feed pump are connected by a connecting pipe, and the oil that merges within the connecting pipe is discharged from a connecting pipe outlet provided on the connecting pipe. Therefore, the position of the connecting pipe outlet can be arbitrarily set depending on the shape and mounting condition of the connecting pipe. Therefore, even if the discharge port is configured to discharge oil into the oil storage chamber, the position of the connecting pipe discharge port can be set so that the oil is discharged at a distance from the intake port where the feed pump draws oil from the oil storage chamber. This reduces the possibility of the feed pump drawing in oil containing air discharged from the connecting pipe discharge port, thereby improving lubrication performance. Furthermore, if the oil is discharged from the connecting pipe outlet to areas other than the oil reservoir, such as the transmission chamber, there is no possibility of the feed pump drawing in oil containing air.

[0012] Furthermore, since an oil pump unit equipped with two scavenging pumps is located on the underside of the crankcase, the two scavenging pumps forcibly suck up the oil that has fallen to the bottom of the crankcase. This reduces the stirring resistance caused by residual oil in the crankcase and reduces the pressure inside the crankcase, thereby reducing the rotational resistance of the crankshaft.

[0013] In a preferred embodiment of the present invention, The connecting pipe is characterized by being screw-fastened to the scavenging pump body of the scavenging pump.

[0014] In this configuration, the ends of the connecting pipe are screw-fastened to the scavenging pump bodies of the scavenging pumps on both sides of the feed pump in the oil pump unit, which is integrally connected to both sides of the feed pump. This allows for a stronger connection between the feed pump and the scavenging pumps on either side, thereby increasing the rigidity of the oil pump unit.

[0015] In a preferred embodiment of the present invention, The aforementioned connecting pipe outlet is characterized by being positioned closer to one of the scavenging pumps.

[0016] With this configuration, even if the connecting pipe outlet is configured to discharge oil into the oil storage chamber, by positioning the connecting pipe outlet closer to one side of the scavenging pumps on both sides, the oil can be discharged to a location further away from the port where the central feed pump draws oil from the oil storage chamber, thereby reducing the possibility of the feed pump drawing in oil containing air discharged from the connecting pipe outlet.

[0017] In a preferred embodiment of the present invention, The discharge port closer to the connecting pipe outlet is located at a lower position than the discharge port further from the connecting pipe outlet. The connecting pipe is characterized by extending downward inclined from the discharge port at a higher position toward the discharge port at a lower position, and being fastened to the scavenging pump bodies of the scavenging pumps on both sides.

[0018] According to this configuration, the connecting pipe extends obliquely downward from the discharge port at the higher position toward the discharge port at the lower position, so that the oil discharged from the discharge port at the higher position flows through the inclined connecting pipe toward the discharge port at the lower position, merges with the oil discharged from the discharge port at the lower position, and is discharged from the connecting pipe discharge port close to the merging position. Accordingly, the oil flows smoothly and efficiently, so that the suction efficiency of the scavenging pump can be improved.

[0019] In a preferred embodiment of the present invention, A bolt fastening portion formed at one end of the connecting pipe is in contact with a fastening surface where the discharge port at the higher position of the scavenging pump body of one of the scavenging pumps opens, and is fastened by a bolt at a position lower than the discharge port at the higher position, A bolt fastening portion formed at the other end of the connecting pipe is in contact with a fastening surface where the discharge port at the lower position of the scavenging pump body of the other scavenging pump opens, and is fastened by a bolt at a position higher than the discharge port at the lower position.

[0020] According to this configuration, in the connecting pipe that is inclined downward from the discharge port at the higher position toward the discharge port at the lower position, the bolt fastening portion at one end is bolted to the fastening surface where the discharge port at the higher position opens at a position lower than that discharge port, and the bolt fastening portion at the other end is bolted to the fastening surface where the discharge port at the lower position opens at a position higher than that discharge port, so that the vertical width of the inclined connecting pipe including the bolt fastening portions at both ends can be kept small, and the connecting pipe can be compactly attached to the oil pump unit.

[0021] In a preferred embodiment of the present invention, The oil storage chamber is an oil pan provided below the crankcase, An extended discharge pipe extends from the connecting pipe discharge port into the oil pan.

[0022] With this configuration, an extension discharge pipe is installed from the connecting pipe's outlet into the oil pan. As a result, the discharged oil is guided downwards into the oil pan by the cylindrical extension discharge pipe from the connecting pipe's outlet, allowing the oil inside the crankcase to be quickly collected into the oil pan and the oil to flow efficiently.

[0023] In a preferred embodiment of the present invention, The aforementioned internal combustion engine constitutes a power unit equipped with a transmission within the crankcase. The aforementioned transmission is installed in a transmission chamber adjacent to the crank chamber. The outlet of the connecting pipe is characterized by spraying oil toward the transmission.

[0024] With this configuration, the connecting pipe's outlet sprays oil towards the transmission located in the transmission chamber adjacent to the crankcase, thus improving the lubrication of the transmission using the connecting pipe. Furthermore, the feed pump will not directly suck in the oil containing air discharged from the connecting pipe outlet.

[0025] In a preferred embodiment of the present invention, The aforementioned internal combustion engine constitutes a power unit equipped with a transmission within the crankcase. The aforementioned transmission is provided adjacent to the crank chamber, A discharge pipe extending upward from the connecting pipe outlet to the transmission discharges oil into the transmission.

[0026] With this configuration, a discharge pipe extends from the discharge port of the connecting pipe upwards to the transmission, and oil is discharged from the discharge pipe to the transmission from above. This allows for a stable supply of oil to the transmission and improves the lubrication performance of the transmission. Furthermore, the feed pump will not directly suck in the oil containing air discharged from the connecting pipe outlet.

[0027] In a preferred embodiment of the present invention, The oil storage chamber is an oil tank located inside or outside the internal combustion engine. A discharge pipe is provided extending from the discharge port of the connecting pipe into the oil tank.

[0028] This lubrication system is a dry sump type. With this configuration, a discharge pipe extends from the discharge port of the connecting pipe into the oil tank. Therefore, even if oil containing air is discharged into the oil tank from the discharge pipe, the feed pump draws oil from the bottom of the oil tank, making it difficult for oil containing air to be drawn in. Furthermore, by placing the oil tank outside the internal combustion engine, the rise in oil temperature can be suppressed. [Effects of the Invention]

[0029] In this invention, the discharge ports of the scavenging pumps on both sides of the feed pump are connected by a connecting pipe, and the oil that merges in the connecting pipe is discharged from an outlet provided in the connecting pipe, so the position of the discharge port can be set arbitrarily. Therefore, even if the discharge port is configured to discharge oil into the oil storage chamber, the position of the discharge port can be set so that the oil is discharged at a distance from the intake port where the feed pump draws oil from the oil storage chamber. This reduces the possibility of the feed pump drawing in oil containing air discharged from the discharge port, thereby improving lubrication performance. Furthermore, if the oil is discharged from the outlet to areas other than the oil reservoir, such as the transmission chamber, there is no possibility of the feed pump drawing in oil containing air. [Brief explanation of the drawing]

[0030] [Figure 1] This is an overall left side view of a motorcycle equipped with an internal combustion engine having a lubrication device according to one embodiment of the present invention. [Figure 2] This is a right-side view of the same internal combustion engine. [Figure 3] This is a disassembled perspective view of the oil pump unit and connecting pipe. [Figure 4] This is a left side view of the oil pump unit. [Figure 5] This is a cross-sectional view taken along line VV in Figure 4. [Figure 6] This is a cross-sectional view taken from VI-VI in Figure 5. [Figure 7] This is a cross-sectional view taken along line VII-VII in Figure 5. [Figure 8] This is a right side view showing the main components of the lubrication system of an internal combustion engine. [Figure 9] This is a rear view showing the main components of the lubrication system of an internal combustion engine. [Figure 10] This is a schematic right-side view of an internal combustion engine illustrating a modified lubrication system. [Figure 11] This is a schematic right-side view of an internal combustion engine illustrating another modified lubrication system. [Modes for carrying out the invention]

[0031] Hereinafter, one embodiment of the present invention will be described with reference to Figures 1 to 9. Figure 1 is a side view of a motorcycle 1, which is a saddle-type vehicle equipped with an internal combustion engine according to one embodiment to which the present invention is applied. In this specification, the forward, backward, left, and right directions will follow the usual standard where the forward direction of the motorcycle 1 according to this embodiment is considered to be forward. In the drawings, FR indicates the front, RR indicates the rear, LH indicates the left, and RH indicates the right.

[0032] As shown in Figure 1, the body frame 2 of the motorcycle 1 comprises a head pipe 3 that supports the front fork 7 that pivotally supports the front wheel FW in a steerable manner, a pair of left and right main frames 4 that extend downward from the head pipe 3, a pair of left and right pivot frames 5 that are connected to the rear end of the main frame 4 and extend downward, and a pair of left and right seat rails 6 that extend upward from the rear of both main frames 4. A swingarm 8, whose front end is pivoted to the pivot frame 5, extends to the rear, and the rear wheel RW is pivotally supported at its rear end.

[0033] The vehicle frame 2 has an internal combustion engine 10 mounted on it, suspended below the main frame 4. A chain 18 is stretched between the output shaft 17 of the internal combustion engine 10 and the rear axle 19 of the rear wheel RW, and the power of the internal combustion engine 10 is transmitted to the rear wheel RW via the chain 18.

[0034] Referring to Figure 2, the internal combustion engine 10 constitutes a so-called power unit, which includes a transmission 16 inside the crankcase 20. This internal combustion engine 10 is a V-type 4-cylinder internal combustion engine in which the crankshaft 11 is oriented in the vehicle width direction (left-right direction). The crankcase 20 comprises a crank chamber 21 that houses the crank web 12 and crank pin 13 of the crankshaft 11, and a transmission chamber 22 behind the crank chamber 21 that houses the transmission 16. An oil pan 23 is mounted from below to the bottom of the crankcase 20. An oil pump unit 50, which will be described later, is mounted from below on the lower side of the crank chamber 21 of the crankcase 20.

[0035] From the front of the crankcase 20, where the crank chamber 21 is located, a forward-tilting cylinder 24 stands upright, pointing diagonally upward and forward, while a rearward-tilting cylinder 25 stands upright, pointing diagonally upward and rearward. A piston 14 is inserted into each of the cylinders of the forward-tilting cylinder 24 and the rear-tilting cylinder 25 so as to be able to reciprocate.

[0036] The piston 14 is connected to the crankpin 13 of the crankshaft 11 via a connecting rod 15, and the reciprocating motion of the piston 14 is converted into rotation of the crankshaft 11 via the connecting rod 15. The rotational driving force of the crankshaft 11 is transmitted to the transmission 16 via a clutch (not shown), which changes the gear ratio and transmits the force to the output shaft 17. As described above, the rotation of the output shaft 17 is transmitted to the rear wheel RW via a chain 18.

[0037] Referring to Figures 2 and 7, the crank chamber 21 forms a pair of independent, sealed crank chambers 21a on the left and right sides. The pair of sealed crank chambers 21a are aligned in the vehicle width direction, and each sealed crank chamber 21a communicates with the inside of either the forward-tilting cylinder 24 or the rearward-tilting cylinder 25. Each sealed crank chamber 21a is separated from the transmission chamber 22 and the oil pan 23 by a partition wall within the crankcase 20.

[0038] Referring to Figure 7, the lower partition wall 20a that partitions the area below the crank chamber 21 has a pair of openings 20h that open each sealed crank chamber 21a downwards. An oil pump unit 50, described later, is attached to this lower bulkhead 20a from below, and the oil suction ports 56Lh and 56Rh of the pair of left and right scavenging pumps 51L and 51R of the oil pump unit 50 are connected to and communicate with each opening 20h in the lower bulkhead 20a from below.

[0039] The mounting surface 50s of the oil pump unit 50, which is attached to the lower bulkhead 20a, is positioned approximately horizontally when the internal combustion engine is mounted in a vehicle (see Figure 6). The mounting surface 50s of the oil pump unit 50 may be inclined downwards towards the rear (see Figure 7).

[0040] Referring to Figure 2, the oil pan 23, which is mounted below the crankcase 20, is mounted so as to protrude downward from the substantially horizontal lower end surface of the crankcase 20. The upper end opening of the container-shaped oil pan 23 is joined from below to the lower end opening of the crankcase 20. The inside of the oil pan 23 is connected to the lower space below the lower partition wall 20a of the crankcase 20, and together with the inside of the oil pan 23, this lower space constitutes the oil storage space 23a (see Figures 2 and 7).

[0041] An oil pump unit 50 is installed in the lower space of the crankcase 20. In other words, the oil pump unit 50 is located on the lower side of the crankcase 21. A baffle 26 is provided below the oil pump unit 50 (see Figures 8 and 9).

[0042] Referring to Figures 3 to 7, the oil pump unit 50 is configured such that scavenging pumps 51L and 51R are integrally connected to both sides of a central feed pump 51C, and are driven by a common pump drive shaft 58. In the vehicle width direction (crankshaft direction), the left scavenging pump 51L, feed pump 51C, and right scavenging pump 51R are arranged in that order, and the common pump drive shaft 58 is oriented in the vehicle width direction.

[0043] The feed pump 51C and the left and right scavenging pumps 51L and 51R are all trochoid pumps. Referring to Figure 5, the left scavenging pump body 52L with a left side wall, the feed pump body 52C, the feed pump side wall 52ca, and the right scavenging pump body 52R with a right side wall are stacked in that order and fastened together as a single unit by bolts B1, B2, and B3.

[0044] Referring to Figures 5 and 6, the feed pump 51C comprises an annular outer rotor 53C rotatably fitted to the inner circumferential surface of the feed pump body 52C, and an inner rotor 54C fitted to a pump drive shaft 58 incorporated inside the outer rotor 53C. The pump drive shaft 58, which is the central axis of the inner rotor 54C, is located eccentrically with respect to the outer rotor 53C. The outer rotor 53C has internal teeth that mesh with fewer external teeth than the eccentric inner rotor 54C, and an oil chamber is formed between the internal and external teeth whose volume changes with rotation.

[0045] The configuration of the left and right scavenging pumps 51L and 51R, as well as the outer rotors 53L and 53R and inner rotors 54L and 54R inside the left and right scavenging pump bodies 52L and 52R, is the same as that of the feed pump 51C.

[0046] As shown in Figure 5, the pump drive shaft 58 has its right end protruding to the right outside of the right scavenging pump body 52R. An input gear 59 is fitted to the protruding right end of the pump drive shaft 58, and the rotation of the crankshaft 11 is transmitted to the input gear 59 (see Figure 8). The rotation of the pump drive shaft 58 simultaneously rotates the inner rotors 54L, 54C, and 54R of the left scavenging pump 51L, the feed pump 51C, and the right scavenging pump 51R, which are coaxially supported on the pump drive shaft 58, thereby driving the pumps.

[0047] Referring to Figures 3 to 6, the feed pump body 52C of the feed pump 51C has a suction port 56C (see Figure 5) formed in the right side feed pump side wall 52ca of the rotor housing section that houses the outer rotor 53C and the inner rotor 54C, from which a suction pipe 60 extends downward. Referring to Figures 8 and 9, the suction pipe 60 passes through the baffle 26 and is connected to the strainer 61. The strainer 61 is deeply inserted into the oil pan 23.

[0048] A discharge port 57C is formed on the left side of the rotor housing (see Figure 5), and a discharge pipe 62 extends downward from the discharge port 57C. The discharge pipe 62, located in front of the intake pipe 60, passes through the baffle 26 and immediately bends forward (see Figure 8). The discharge pipe 62 is connected to an oil line (not shown), and the oil pumped into the oil line is supplied to each lubrication part of the internal combustion engine. A relief valve 63 is provided on the side of the discharge port 57C (see Figure 5).

[0049] As described above, the central feed pump 51C of the oil pump unit 50 draws oil stored in the oil pan 23 through the strainer 61 to the intake port 56C, discharges it from the discharge port 57C to the discharge pipe 62, pumps it into the oil line, and supplies it to each lubrication part of the internal combustion engine through the oil line.

[0050] Referring to Figures 3 to 5 and Figure 7, the left scavenging pump body 52L of the left scavenging pump 51L and the right scavenging pump body 52R of the right scavenging pump 51R are equipped with suction ports 56L, 56R (see Figure 7) and discharge ports (not shown), respectively, that communicate with the rotor housings that house the outer rotors 53L, 53R and the inner rotors 54L, 54R.

[0051] Referring to Figures 3 and 7, the upper surfaces of the left scavenging pump body 52L and the right scavenging pump body 52R are formed with rectangular oil suction ports 56Lh and 56Rh, respectively, and each oil suction port 56Lh and 56Rh communicates with the suction ports 56L and 56R formed on the upper side of the rotor housing.

[0052] When the oil pump unit 50 is attached from below to the lower partition wall 20a that partitions the lower part of the crankcase 21 using bolts B4, B5, B5, B6, B6, the left and right oil intake ports 56Lh and 56Rh on the upper surfaces of the left and right scavenging pump bodies 52L and 52R are joined to the left and right openings 20h formed in the lower partition wall 20a, respectively, so that the intake ports 56L and 56R communicate with the crankcase 21.

[0053] Bolt B4 fastens the front of the feed pump body 52C to the lower bulkhead 20a; bolts B5, B5 fasten the diagonally front edges of the oil intake ports 56Lh, 56Rh of the left and right scavenging pump bodies 52L, 52R to the lower bulkhead 20a; and bolts B6, B6 fasten the rear ends of the protruding portions 52Lp, 52Rp that protrude rearward from the left and right scavenging pump bodies 52L, 52R to the lower bulkhead 20a.

[0054] Referring to Figure 7, the left and right scavenging pump bodies 52L and 52R are equipped with a pair of left and right reed valves 67. Rectangular valve openings 65, 65 are formed at the top of the forward-sloping front walls 52Lf, 52Rf of the left and right scavenging pump bodies 52L, 52R, and bulging spaces 66, 66 that protrude in front of the suction ports 56L, 56R are opened at the valve openings 65, 65.

[0055] Referring to Figure 7, the oil pump unit 50 is installed protruding from the oil storage space 23a below the crankcase 21, so that the oil storage space 23a and the bulging space 66 are in communication via the valve opening 65. Since the bulging space 66 is in communication with the intake ports 56L and 56R and also with the sealed crank chamber 21a, the valve opening 65 connects the sealed crank chamber 21a with the oil storage space 23a.

[0056] A reed valve 67 is provided in this valve opening 65. The reed valve 67 includes a valve body 67v that opens and closes the valve opening 65 and a stopper 67s that restricts the movement of the valve body 67v when the valve is open. The valve body 67v is shaped like a rectangular plate, and the stopper 67s is shaped like a rectangular frame, identical in shape to the valve body 67v. The stopper 67s, which is placed on top of the valve body 67v, is brought into contact with the front walls 52Lf and 52Rf from the oil reservoir space 23a side so as to block the valve opening 65 of the forward-sloping front walls 52Lf and 52Rf of the left and right scavenging pump bodies 52L and 52R, and the upper part is fixed with bolt B7.

[0057] The reed valve 67 opens and closes the valve opening 65 in response to the internal pressure of the sealed crank chamber 21a, with the valve body 67v causing the valve opening 65 to open and close. When the left and right scavenging pumps 51L and 51R are driven, the sealed crank chamber 21a is normally under negative pressure, so the reed valve 67 has a valve body 67v that closes the valve opening 65. However, when the internal pressure of the sealed crank chamber 21a increases, the valve body 67v opens the valve opening 65, and oil flows out of the sealed crank chamber 21a into the oil storage space 23a. Furthermore, the spilled oil strikes the outer surface of the lower fastening portion 52d of the front wall 52Lf, 52Rf, separating the air contained in the oil, and the oil from which the air has been separated flows down into the oil pan 23.

[0058] Referring to Figure 3, the rear walls of the left and right scavenging pump bodies 52L and 52R have triangularly protruding fastening portions 52La and 52Ra, and the fastening portions 52La and 52Ra have triangular fastening surfaces 52Lf and 52Rf facing backward. Discharge ports (not shown) that communicate with the sides of the rotor housings of the left and right scavenging pump bodies 52L and 52R extend rearward and open as discharge ports 57L and 57R on the fastening surfaces 52Lf and 52Rf. A relief valve 68 is provided on the side of the discharge port (see Figure 5).

[0059] The left and right fastening surfaces 52Lf and 52Rf are at approximately the same height, but the discharge port 57L opening on the left fastening surface 52Lf is located lower than the discharge port 57R opening on the right fastening surface 52Rf. Bolt fastening holes 52Lb and 52Rb are formed in the left and right fastening surfaces 52Lf and 52Rf, respectively. On the left fastening surface 52Lf, the bolt fastening hole 52Lb is provided above the discharge port 57L, while on the right fastening surface 52Rf, the bolt fastening hole 52Rb is provided below the discharge port 57R.

[0060] A connecting pipe 70 is attached to the left and right fastening surfaces 52Lf and 52Rf, respectively, and has triangular flange portions 70Lf and 70Rf at its left and right ends. As shown in Figure 3, the connecting pipe 70 has its left and right ends bent forward at the bent portions 70Lb and 70Rb, with flange portions 70Lf and 70Rf formed at the bent ends.

[0061] The left and right flange portions 70Lf and 70Rf of the connecting pipe 70, which abuts against the left and right fastening surfaces 52Lf and 52Rf of the left and right scavenging pump bodies 52L and 52R respectively, have pipe holes opening opposite the left and right discharge ports 57L and 57R that open on the left and right fastening surfaces 52Lf and 52Rf, respectively, and bolt holes 70Lb and 70Rb are formed opposite the bolt fastening holes 52Lb and 52Rb formed on the left and right fastening surfaces 52Lf and 52Rf, respectively.

[0062] Therefore, the fastening surfaces on the front of the left and right flange portions 70Lf and 70Rf of the connecting pipe 70 are brought into contact with the left and right fastening surfaces 52Lf and 52Rf, and the bolts 72L and 72R inserted into the bolt holes 70Lb and 70Rb drilled in the flange portions 70Lf and 70Rf are screwed into the bolt fastening holes 52Lb and 52Rb of the fastening surfaces 52Lf and 52Rf to fasten them.

[0063] The connecting pipe 70 attached to the left and right scavenging pump bodies 52L and 52R connects the left outlet 57L to the right outlet 57R, which is located higher than the left outlet 57L. Therefore, as shown in Figure 9, the connecting pipe 70 is inclined downward from the right-side discharge port 57L, which is at a higher position, to the left-side discharge port 57L, which is at a lower position.

[0064] Then, at the bent portion 70Lb of the connecting pipe 70, which bends toward the left-side discharge port 57L located at a lower position, a discharge pipe end 70ap is formed, which has a downward-facing connecting pipe discharge port 70a (see Figure 3). Referring to Figures 8 and 9, an extension discharge pipe 71 is connected to the discharge pipe end 70ap of the connecting pipe 70, and the extension discharge pipe 71 extends downward, passes through the baffle 26, and opens into the oil pan 23. Furthermore, a fixing plate 27 is provided below the baffle 26 to secure the extension discharge pipe 71, which is connected to the suction pipe 60 of the feed pump 51C and the discharge pipe end 70ap of the connecting pipe 70.

[0065] When the inner rotors 54L, 54R and outer rotors 53L, 53R of the oil pump unit 50 are rotated, the left and right scavenging pumps 51L, 51R draw oil from the sealed crankcase 21a through the oil intake ports 56Lh, 56Rh to the intake ports 56L, 56R. Furthermore, the ACG chamber of the AC generator (not shown), which is adjacent to the sealed crank chamber 21a on the left side, may also be connected to the oil intake port 56Lh on the left side, and the oil discharged into the ACG chamber is also drawn in from the left oil intake port 56Lh to the intake port 56L of the left scavenging pump 51L.

[0066] The oil drawn into the intake ports 56L and 56R is discharged from the left and right outlets 57L and 57R into the pipe holes at the left and right ends of the connecting pipe 70. The oil discharged from the pipe holes at the left and right ends merges at the left bend 70Lb inside the connecting pipe 70, passes through the connecting pipe outlet 70a, and is discharged into the oil pan 23 from the extension discharge pipe 71.

[0067] When the scavenging pumps 51L and 51R are driven, oil is drawn into the sealed crank chamber 21a, forcibly creating a negative pressure inside the sealed crank chamber 21a. This reduces the pumping loss caused by the reciprocating motion of the piston 14, and the discharge of excess oil from the sealed crank chamber 21a reduces the resistance of the crankshaft 11 to agitating the oil, thereby suppressing friction loss.

[0068] The embodiment of the lubrication device for an internal combustion engine according to the present invention, as described in detail above, provides the following effects. The left and right scavenging pumps 51L and 51R draw in oil that has been agitated by the crankshaft, so the oil they draw in contains a lot of air. This oil containing air is discharged into the connecting pipe 70 and then discharged into the oil pan 23 from an extension discharge pipe 71 that extends downward from the connecting pipe outlet 70a at the left bend 70Lb of the connecting pipe 70. On the other hand, the central feed pump 51C is connected to a suction pipe 60 that extends downward from the feed pump body 52, and a strainer 61 that extends further downward draws in oil from the oil pan 23.

[0069] As shown in Figure 3, the connecting pipe 70 is mounted behind the oil pump unit 50, and its outlet 70a is located on the side of the bent portion 70Lb at the left end of the connecting pipe 70. Therefore, the outlet 70a can be located away from the central feed pump 51C of the oil pump unit 50.

[0070] Therefore, as shown in Figures 8 and 9, the extension discharge pipe 71, which extends downward from the connecting pipe outlet 70a, can be positioned away from the strainer 61, which extends downward from the central feed pump 51C. Therefore, the feed pump 51C is less likely to suck in oil containing air discharged from the extension discharge pipe 71 through the strainer 61, thus improving lubrication performance.

[0071] As shown in Figures 8 and 9, an extension discharge pipe 71 is provided from the connecting pipe outlet 70a of the connecting pipe 70 into the oil pan 23. Therefore, the discharged oil is guided downward into the oil pan 23 by the cylindrical extension discharge pipe 71 from the connecting pipe outlet 70a of the connecting pipe 70. As a result, the oil inside the crankcase 20 is quickly collected into the oil pan 23, and the oil flows efficiently.

[0072] As shown in Figures 3 and 9, the connecting pipe 70 has flange portions 70Lf and 70Rf at both ends fastened to the scavenging pump bodies 52L and 52R of the scavenging pumps 51L and 51R on both sides of the oil pump unit 50, which has scavenging pumps 51L and 51R integrally connected to both sides of the feed pump 51C, by bolts 72R and 72L, respectively. This allows the connection between the feed pump 51C and the scavenging pumps 51L and 51R on both sides to be made stronger by the connecting pipe 70, thereby increasing the rigidity of the oil pump unit 50.

[0073] As shown in Figures 3 and 9, the connecting pipe 70 extends downward from the higher outlet 57R to the lower outlet 57L. Therefore, the oil discharged from the higher outlet 57R flows along the inclined connecting pipe 70 towards the lower outlet 57L, merges with the oil discharged from the lower outlet 57L, and is then discharged from the connecting pipe outlet 70a closest to the point of convergence. Therefore, the oil flows smoothly and efficiently, improving the suction efficiency of the scavenging pumps 51L and 51R.

[0074] As shown in Figures 3 and 9, the connecting pipe 70, which is inclined downward from the higher outlet 57R to the lower outlet 57L, has a flange portion 70Rf at one end, which is a bolted fastening portion, fastened to the fastening surface 52Rf where the higher outlet 57R opens, by bolt B7 below the outlet 57R, and a flange portion 70Lf at the other end, which is a bolted fastening portion, fastened to the fastening surface 52Lf where the lower outlet 57L opens, by bolt B7 above the outlet 57L. Therefore, the vertical width of the inclined connecting pipe 70, including the flange portions 70Lf and 70Rf at both ends, is kept small, and it can be compactly attached to the oil pump unit 50.

[0075] Next, a modified example of the lubrication device will be explained based on Figure 10. This lubrication device is substantially the same as the lubrication device described above, and in Figure 10, the same reference numerals are used for the same components, including the internal combustion engine. In the lubrication system described above, oil was discharged from the connecting pipe outlet 70a of the connecting pipe 70 to the oil pan 23 below. However, in this modified example, the connecting pipe 80 of the lubrication system is located behind the oil pump unit 50 and extends in the vehicle width direction below the transmission 16 in the transmission chamber 22, which is adjacent to the crankcase 21 at the rear. In addition to the connecting pipe outlet 70a at the left end of the connecting pipe 80, multiple connecting pipe outlets 80a are provided in the vehicle width direction to spray oil towards the transmission 16 above.

[0076] By using the connecting pipe 80, oil can be injected from the connecting pipe outlet 80a to the transmission 16, thereby improving the lubrication of the transmission 16. Furthermore, the feed pump will not directly suck in the oil containing air discharged from the connecting pipe outlet 80a.

[0077] Referring to the same Figure 10, another modified example is provided in which another connecting pipe outlet 80b is added to the connecting pipe 80, and a discharge pipe 81 is extended from the connecting pipe outlet 80b above the transmission 16, with the discharge pipe 81 discharging oil from above to the transmission 16. By using the connecting pipe 80 and discharging oil from the discharge pipe 81, which extends to the connecting pipe outlet 80b, to the transmission 16 from above, a stable supply of oil to the transmission can be achieved, thereby improving the lubrication performance of the transmission 16. Furthermore, the feed pump will not directly suck in the oil containing air discharged from the connecting pipe outlet 80b.

[0078] Another variation of the lubrication device will be explained with reference to Figure 11. This modified example is a dry-sump lubrication system that has an oil tank 95 inside or outside the internal combustion engine instead of an oil pan. Therefore, there is no oil pan located below the crankcase.

[0079] Furthermore, a discharge pipe 91 extends from the discharge port 90a of the connecting pipe 90 into the oil tank 95. The suction pipe 92 of the feed pump 51C extends to the oil tank 95 and is connected to an opening in the bottom wall of the oil tank 95.

[0080] Therefore, the scavenging pumps 51L and 51R are driven to draw in oil from the sealed crankcase 21a, the drawn-in oil is discharged into the connecting pipe 70, and then discharged into the oil tank 95 through the discharge pipe 91 from the connecting pipe outlet 90a. The oil stored in the oil tank 95 is drawn in from the bottom of the oil tank 95 through the suction pipe 92 by the drive of the feed pump 51C, pumped into the oil line, and supplied to each lubrication part of the internal combustion engine.

[0081] Even when oil containing air is discharged into the oil tank 95 from the discharge pipe 91 by the operation of the scavenging pumps 51L and 51R, the feed pump 51C draws oil from the bottom of the oil tank 95, making it difficult for oil containing air to be drawn in. Furthermore, by placing the oil tank 95 outside the internal combustion engine, the rise in oil temperature can be suppressed.

[0082] Although a lubrication device according to an embodiment of the present invention has been described above, the embodiments of the present invention are not limited to the above embodiments and include a variety of embodiments that can be implemented within the scope of the gist of the present invention. [Explanation of Symbols]

[0083] 1...Motorcycle, 2...Body frame, 3...Head pipe, 4...Main frame, 5...Pivot frame, 6...Seat rail, 7...Front fork, 8...Swing arm 10...Internal combustion engine, 11...Crankshaft, 12...Crank web, 13...Crankpin, 14...Piston, 15...Connecting rod, 16...Transmission, 17...Output shaft, 18...Chain, 19...Rear axle 20...Crankcase, 20a...Lower bulkhead, 21...Crank chamber, 21a...Sealed crank chamber, 22...Transmission chamber, 23...Oil pan, 23a...Oil reservoir, 24...Forward-tilting cylinder, 25...Rearward-tilting cylinder, 26...Baffle, 27...Fixing plate, 50…Oil pump unit, 50s…Mounting surface, 51C…Feed pump, 51L…Left scavenging pump, 51R…Right scavenging pump, 52C…Feed pump body, 52ca…Feed pump side wall, 52L…Left scavenging pump body, 52R…Right scavenging pump body, 52d…Lower fastening part, 52La, 52Ra…Fastening part, 52Lf, 52Rf…Fastening surface, 53C, 53L, 53R... Outer rotor, 54C, 54L, 54R... Inner rotor, 56C, 56L, 56R... Intake port, 56Lh, 56Rh... Oil intake port, 57C... Discharge port, 57L, 57R... Discharge port, 58... Pump drive shaft, 59... Input gear, 60...Intake pipe, 61...Strainer, 62...Discharge pipe, 63...Relief valve, 65...Valve opening, 66...Bulge space, 67...Reed valve, 67v...Valve body, 67s...Stopper, 68...Relief valve, 70...Connecting pipe, 70a...Connecting pipe outlet, 70ap...Discharge pipe end, 70Lb, 70Rb...Bend, 70Lf, 70Rf...Flange, 70Lb, 70Rb...Bolt hole, 71...Extension discharge pipe, 72L, 72R...Bolt, 80...Connecting pipe, 80a...Connecting pipe outlet, 80b...Connecting pipe outlet, 81...Discharge pipe, 90...Connecting pipe, 90a...Connecting pipe outlet, 91...Discharge pipe, 92...Intake pipe, 95...Oil tank.

Claims

1. The internal combustion engine includes a scavenging pump (51L, 51R) that sucks up oil that has fallen to the bottom of the crank chamber (21) of the crankcase (20) and discharges it to the outside of the crank chamber (21) inside the crankcase (20), and a feed pump (51C) that sucks up oil from the oil storage chamber (23; 95) and supplies oil to each lubrication part of the internal combustion engine, The feed pump (51C) is connected to both sides of the scavenging pumps (51L, 51R) in an oil pump unit (50) which is driven by a common pump drive shaft (58). The oil pump unit (50) is a lubrication system for an internal combustion engine, which is located below the crankcase (21). The discharge ports (57L, 57R) of the scavenging pumps (51L, 51R) on both sides are connected by connecting pipes (70; 80; 90). A lubrication system for an internal combustion engine, characterized in that the oil discharged from the two aforementioned discharge ports (57L, 57R) merges within the connecting pipe (70; 80; 90) and is discharged from connecting pipe outlets (70a; 80a; 80b; 90a) provided on the connecting pipe (70; 80; 90).

2. The lubrication device for an internal combustion engine according to claim 1, characterized in that the connecting pipe (70) is screw-fastened to the scavenging pump body (52L; 52R) of the scavenging pump (51L, 51R).

3. The lubrication device for an internal combustion engine according to claim 1, characterized in that the connecting pipe outlet (70a) is provided closer to one of the scavenging pumps (51L).

4. The discharge port (57L) that is closer to the connecting pipe outlet (70a) is located at a lower position than the discharge port (57R) that is further away from the connecting pipe outlet (70a). The lubrication device for an internal combustion engine according to claim 3, characterized in that the connecting pipe (70) extends downward inclined from the discharge port (57R) located at a higher position toward the discharge port (57L) located at a lower position.

5. On the other hand, the bolt fastening portion (70Rf) formed at one end of the connecting pipe (70) is in contact with the fastening surface (52Rf) where the discharge port (57R), located at a higher position on the scavenging pump body (51R) of the scavenging pump (51R), opens, and is fastened by a bolt (72R) below the discharge port (57R), which is located at a higher position. The lubrication device for an internal combustion engine according to claim 4, characterized in that a bolt fastening portion (70Lf) formed at the other end of the connecting pipe (70) is in contact with a fastening surface (52Lf) on which the discharge port (57L), located at a lower position on the scavenging pump body (52L) of the other scavenging pump (51L), opens, and is fastened with a bolt (72L) above the discharge port (57L), which is located at a lower position.

6. The oil storage chamber is an oil pan (23) located below the crankcase (20), The lubrication device for an internal combustion engine according to claim 1, characterized in that an extension discharge pipe (71) is provided from the connecting pipe outlet (70a) into the oil pan (23).

7. The aforementioned internal combustion engine constitutes a power unit equipped with a transmission (16) inside the crankcase (20). The transmission (16) is provided in a transmission chamber (22) adjacent to the crank chamber (21), The lubrication device for an internal combustion engine according to claim 1, characterized in that the connecting pipe outlet (80a) injects oil toward the transmission (16).

8. The aforementioned internal combustion engine constitutes a power unit equipped with a transmission (16) inside the crankcase (20). The transmission (16) is provided in a transmission chamber (22) adjacent to the crank chamber (21), The lubrication device for an internal combustion engine according to claim 1, characterized in that a discharge pipe (81) extending upward from the connecting pipe outlet (80b) to the transmission (16) discharges oil to the transmission (16).

9. The oil storage chamber is an oil tank (95) located inside or outside the internal combustion engine. The lubrication device for an internal combustion engine according to claim 1, characterized in that a discharge pipe (91) extends from the connecting pipe discharge port (90a) into the oil tank (95).

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