JP3881831B2 - Four cycle engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a handheld four-cycle engine mainly serving as a power source for trimmers and other portable work machines, and in particular, from a crankcase having a crank chamber, a cylinder block having a cylinder bore, and a cylinder head having an intake port and an exhaust port. The engine body, the crankshaft supported by the crankcase and housed in the crankcase, the intake and exhaust valves attached to the cylinder head to open and close the intake and exhaust ports, and the rotation of the crankshaft The present invention relates to an improvement of a four-cycle engine including a valve operating mechanism that opens and closes an intake valve and an exhaust valve, and a power take-off mechanism that is provided at one end of a crankshaft projecting outward from the engine body.
[0002]
[Prior art]
  Such a hand-held four-cycle engine is already known as disclosed in, for example, Japanese Patent Laid-Open No. 10-28801.
[0003]
[Problems to be solved by the invention]
  The four-cycle engine is effective in ensuring the health of the user who carries the engine as well as preventing environmental pollution since the exhaust gas is relatively clean. However, since its structure is more complex than a two-cycle engine, there is a difficulty that it is difficult to reduce the weight. Weight reduction is one of the important issues for improving workability, especially for handheld four-cycle engines.
[0004]
  However, in the four-cycle engine disclosed in the above publication, the valve operating mechanism that opens and closes the intake and exhaust valves provided on the cylinder head is configured to use a push rod and a lower arm. Since the valve operating chamber for accommodating the camshaft and the like for driving the engine is formed on the side wall of the engine body, the engine body inevitably increases in size, making it difficult to reduce the weight of the engine.
[0005]
  The present invention has been made in view of the above points, and an object of the present invention is to provide a four-cycle engine that can reduce the size of the engine body and is lightweight and has good workability.
[0006]
[Means for Solving the Problems]
  To achieve the above object, the present invention includes a crankcase having a crank chamber, a cylinder block having a cylinder bore, and an intake port and an exhaust port.With a breather chamber (69)An engine body consisting of a cylinder head, a crankshaft supported by a crankcase and housed in a crankcase, an intake valve and an exhaust valve attached to the cylinder head to open and close an intake port and an exhaust port, and rotation of the crankshaft In a four-cycle engine having a valve mechanism that interlocks and opens and closes an intake valve and an exhaust valve, and a power take-off mechanism that is provided at one end of the crankshaft projecting outward from the engine body, An oil tank with the other end of the crankshaft facing the inside is disposed outside the mechanism, and a timing transmission device for a valve mechanism connected to the crankshaft in the oil tank. Lubricate the timing gear with the oil inside,Further, the valve chamber is partitioned into a first valve chamber communicating with the oil tank and a second valve chamber communicating with the crank chamber via a one-way valve, and the first valve chamber and the second valve chamber are separated from each other. The liquefied oil separated by the breather chamber is returned to the oil tank through the oil return passage.First feature.
[0007]
  According to this first feature, it is not necessary to provide a special chamber for accommodating the timing transmission device on the side wall of the engine body itself, and the overall height of the engine is lowered by the lateral arrangement of the oil tank, and therefore the side wall of the engine body is reduced. By reducing the thickness and size of the engine, the overall engine weight can be significantly reduced.
[0008]
  Moreover, the power take-off mechanism arranged on one side of the engine body and the timing transmission and oil tank arranged on the other side provide a good weight balance at both ends of the crankshaft so that the center of gravity of the engine It will be as close to the center as possible, and combined with weight reduction, the engine workability can be improved.
[0009]
  Also, during engine operation, the load applied to the timing transmission and power take-off mechanism is distributed to both ends of the crankshaft, avoiding concentration of load on the crankshaft and its bearings, and improving their durability. Can be improved.
[0010]
  Furthermore, since the timing transmission is directly lubricated with the oil in the oil tank, the lubrication system can be simplified.
[0011]
  The power take-out mechanism corresponds to a centrifugal clutch 49 in an embodiment of the present invention described later.
[0012]
  In addition to the first feature, the present invention has a second feature that a cooling fan having a larger diameter than the power take-off mechanism is fixed to the crankshaft between the engine body and the power take-out mechanism.
[0013]
  According to the second feature, it is possible to avoid an increase in the size of the engine E as much as possible while increasing the blowing capacity of the cooling fan.
[0014]
  In addition to the first feature of the present invention, a cam device for transmitting the rotation of the driven side of the timing transmission device to the intake and exhaust valves as an opening / closing force is disposed in the valve chamber provided in the cylinder head. A third feature is that oil mist generating means is connected to the crankshaft so as to generate oil mist supplied to the valve operating chamber in the oil tank.
[0015]
  According to the third feature, the lubrication system of the valve operating mechanism includes a system that lubricates the timing transmission device with oil in the oil tank, a system that lubricates the cam device with oil mist generated in the oil tank, and Therefore, the load on each lubrication system is reduced, and the entire valve mechanism can be lubricated uniformly.
[0016]
  The valve operating chamber corresponds to a second valve operating chamber 21b in an embodiment of the present invention to be described later, and the oil mist generating means corresponds to oil slinger 56a, 56b.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described based on examples of the present invention shown in the accompanying drawings.
[0018]
  1 is a perspective view showing an example of use of the hand-held four-cycle engine of the present invention, FIG. 2 is a longitudinal side view of the four-cycle engine, FIG. 3 is a sectional view taken along line 3-3 in FIG. 2, and FIG. 4 is a cross-sectional view taken along line 4-4, FIG. 5 is an enlarged cross-sectional view of the main portion of FIG. 2, FIG. 6 is an exploded view of the main portion of FIG. 8 is a sectional view taken along line 9-9 of FIG. 8, FIG. 10 is a sectional view taken along arrow 10-10 of FIG. 5 (bottom view of the head cover), and FIG. 11 is a sectional view taken along line 11-11 of FIG. FIG. 12, FIG. 12 is a lubrication route diagram of the engine, FIG. 13 is a diagram corresponding to FIG. 4 showing the inverted state of the engine, and FIG. 14 is a diagram corresponding to FIG. 4 showing the engine lying sideways.
[0019]
  As shown in FIG. 1, the handheld four-cycle engine E is attached to the drive unit as a power source of a power trimmer T, for example. Since the power trimmer T is used with the cutter C directed in various directions depending on the working state, the engine E is also greatly inclined or inverted each time, and the driving posture is not constant.
[0020]
  First, the structure of the outer periphery of the handheld four-cycle engine E will be described with reference to FIGS.
[0021]
  A carburetor 2 and an exhaust muffler 3 are attached to the front and rear of the engine body 1 of the handheld four-cycle engine E, respectively, and an air cleaner 4 is attached to the inlet of the carburetor 2. A synthetic resin fuel tank 5 is attached to the lower surface of the engine body 1.
[0022]
  Both ends of the crankshaft 13 project from the engine body 1 and the oil tank 40 disposed adjacent to the outside of the engine body 1 and are transmitted to a driven member 84 fixed to the one end. , A connectable recoil starter 42 is attached to the outer surface of the oil tank 40. Further, a timing transmission device 22a of the valve mechanism 22 described later is disposed on one side of the engine body 1 with its drive side facing the oil tank 40.
[0023]
  A cooling fan 43 that also serves as a flywheel is fixed to the other end of the crankshaft 13. A plurality of mounting bosses 46 (one of which is shown in FIG. 2) are formed on the outer surface of the cooling fan 43, and a centrifugal shoe 47 is pivotally supported by each mounting boss 46 so as to be swingable. Is done. The centrifugal shoe 47 constitutes the centrifugal clutch 48 together with a clutch drum 48 fixed to the drive shaft 50, which will be described later. When the rotational speed of the crankshaft 13 exceeds a predetermined value, the centrifugal shoe 47 is subjected to its centrifugal operation. The output torque of the crankshaft 13 is transmitted to the drive shaft 50 by being pressed against the inner peripheral wall of the clutch drum 48 by force. The cooling fan 43 has a larger diameter than the centrifugal clutch 48.
[0024]
  An engine cover 51 that covers the engine main body 1 and attached devices other than the fuel tank 5 is fixed to an appropriate position of the engine main body 1, and a cooling air intake 19 is provided between the engine cover 51 and the fuel tank 5. Therefore, the outside air is taken in from the cooling air intake 19 by the rotation of the cooling fan 43 and is used for cooling each part of the engine E.
[0025]
  A frustum-shaped bearing holder 75 arranged coaxially with the crankshaft 6 is fixed to the engine cover 51, and the bearing holder 75 supports a drive shaft 50 that rotationally drives the cutter C via a bearing 59.
[0026]
  Thus, with the engine body 1 in between, the oil tank 40, the timing transmission device 22a and the starter 42 are disposed on one side, and the cooling fan 43 and the centrifugal clutch 49 are disposed on the other side. The weight balance of the engine E is good, the center of gravity of the engine E can be brought close to the center of the engine body 1, and the handling performance of the engine E becomes good.
[0027]
  Further, since the cooling fan 43 having a diameter larger than that of the centrifugal shoe 47 is fixed to the crankshaft 13 between the engine body 1 and the centrifugal shoe 47, the engine E can be increased in size as much as possible while increasing the blowing capacity of the cooling fan 43. It can be avoided.
[0028]
  Further, during operation of the engine E, the load applied to the timing transmission 22a and the centrifugal clutch 49 is distributed to both ends of the crankshaft 13 to avoid concentration of loads on the crankshaft 13 and its bearings. Durability can also be improved.
[0029]
  Next, the structure of the engine body 1 and the oil tank 40 will be described with reference to FIGS. 2 to 5, 6, 10, and 11.
[0030]
  2 to 5, the engine body 1 includes a crankcase 6 having a crank chamber 6a, a cylinder block 7 having one cylinder bore 7a, and a combustion chamber 8a and suction and exhaust ports 9 and 10 opened to the chamber 8. A plurality of cooling fins 38 are formed on the outer periphery of the cylinder block 7 and the cylinder head 8.
[0031]
  The crankshaft 13 accommodated in the crank chamber 6a is rotatably supported on the left and right side walls of the crankcase 6 via ball bearings 14 and 14 '. At this time, the left ball bearing 14 is provided with a seal, and an oil seal 17 is provided adjacent to the outside of the right ball bearing 14 '. A piston 15 fitted to the cylinder bore 7a is connected to the crankshaft 13 via a connecting rod 16 as usual.
[0032]
  An oil tank 40 adjacent to the outside is integrally connected to the left side wall of the crankcase 6, and the oil tank 40 is disposed so that the end of the crankshaft 13 on the side of the ball bearing with seal 14 passes therethrough. . An oil seal 39 is attached to the outer wall of the oil tank 40 that passes through the crankshaft 13.
[0033]
  On the ceiling wall of the oil tank 40, a belt guide tube 86 having a flat cross-section that extends vertically and penetrates the top and bottom ends and is open at both ends is integrally provided. The lower end of the belt guide tube 86 extends to the vicinity of the crankshaft 13 in the oil tank 40, and the upper end portion is integrally connected to the cylinder head 8 so as to share the cylinder head 8 and the partition wall 85. . A series of annular seal beads 87 are formed at the upper peripheral edges of the cylinder head 8 and the belt guide tube 86, and the partition wall 85 projects upward from the seal beads 87.
[0034]
  On the other hand, as shown in FIGS. 6, 10, and 11, an annular seal groove 88 a corresponding to the seal bead 87 is formed on the lower end surface of the head cover 36, and an annular seal groove 88 a is formed on the inner surface of the cover 36. A linear seal groove 88b communicating between both sides is formed, an annular seal 89a is mounted on the annular seal groove 88a, and a linear seal 89b integrally formed with the annular seal 89a is installed in the linear seal groove 88b. Installed. The head cover 36 is coupled to the cylinder head 8 by bolts 37 so that the seal beads 87 are pressed against the annular packing 89a and the partition walls 85 are pressed against the linear packing 89b.
[0035]
  Thus, the first valve operating chamber 21a is defined by the belt guide tube 86 and one half of the head cover 36, and the second valve operating chamber 21b is defined by the cylinder head 8 and the other half of the head cover 36. The valve chambers 21 a and 21 b are partitioned by the partition wall 85.
[0036]
  2 to 5 again, the engine main body 1 and the oil tank 40 are divided into two, an upper block Ba and a lower block Bb, on a plane passing through the axis of the crankshaft 13 and orthogonal to the axis of the cylinder bore 7a. That is, the upper block Ba is formed by integrally connecting the upper half of the crankcase 6, the cylinder block 7, the cylinder head 8, the upper half of the oil tank 40, and the belt guide tube 86, and the lower block Bb 6 and the lower half of the oil tank 40 are integrally connected. The upper and lower blocks Ba and Bb are individually casted and processed into a plurality of bolts. 12 (see FIG. 4).
[0037]
  The cylinder head 8 is provided with an intake valve 18i and an exhaust valve 18e that open and close the intake port 9 and the exhaust port 10, respectively, in parallel with the axis of the cylinder bore 7a, and an ignition plug 20 is connected to the center of the combustion chamber 8a. It is screwed in close proximity to.
[0038]
  Next, the valve mechanism 22 for opening and closing the intake valve 18i and the exhaust valve 18e will be described with reference to FIGS.
[0039]
  The valve mechanism 22 includes a timing transmission device 22a disposed from the oil tank 40 to the first valve chamber 21a, and a cam disposed from the first valve chamber 21a to the second valve chamber 21b. And the device 22b.
[0040]
  The timing transmission device 22a includes a driving pulley 23 fixed to the crankshaft 13 in the oil tank 40, a driven pulley 24 rotatably supported on the upper portion of the belt guide tube 86, the driving and driven pulleys 23, The cam 26 forming a part of the cam device 22b is integrally coupled to the end face of the driven pulley 24 on the partition wall 85 side. In this way, the cam 26 is disposed with the driven pulley 24 on one side of the cylinder head 8. The driving and driven pulleys 23 and 24 are toothed, and the driving pulley 23 drives the driven pulley 24 through the belt 25 with a reduction ratio of 1/2.
[0041]
  A support wall 27 is integrally formed on the outer wall of the belt guide tube 86 so as to stand up inside the annular seal bead 87 and come into contact with or close to the inner surface of the head cover 36. Both ends of the support shaft 29 are rotatably supported by the hole 28a and the bottomed hole 28b provided in the partition wall 85, and the driven pulley 24 and the cam 26 are rotatably supported by the intermediate portion of the support shaft 29. The support shaft 29 is inserted into the shaft hole 35 and the bottomed hole 28b of the driven pulley 24 and the cam 26 from the through hole 28a before the head cover 36 is attached. After the insertion, the head cover 36 is inserted into the cylinder head 8. When the head cover 36 is joined to the belt guide tube 86, the inner surface of the head cover 36 faces the outer end of the support shaft 29 to prevent it from coming off.
[0042]
  The partition wall 85 is integrally formed with a pair of bearing bosses 30i and 30e protruding in parallel with the support shaft 29 on the second valve chamber 21b side. The cam device 22b includes the cam 26 and the bearing boss 30i. , 30e are rotatably supported by an intake rocker shaft 31i and an exhaust rocker shaft 31e, respectively, and fixed to one end of these rocker shafts 31i, 31e in the first valve operating chamber 21a, and the tip is slidably contacted with the lower surface of the cam The intake cam follower 22i and the exhaust cam follower 22e to be driven, and the second valve chamber 21b are fixed to the other ends of the intake and exhaust rocker shafts 31i and 31e, respectively, and the intake is brought into contact with the upper ends of the intake valve 18i and the exhaust valve 18e. An intake valve mounted on the rocker arm 33i and the exhaust rocker arm 33e, and the intake valve 18i and the exhaust valve 18e, respectively, and biases them in the valve closing direction. 34i and is made from an exhaust spring 34e.
[0043]
  As described above, the support shaft 29 and the intake and exhaust rocker shafts 31 i and 31 e are disposed above the cylinder head 8 and the annular seal bead 87 at the upper end of the belt guide tube 86.
[0044]
  Thus, when the crankshaft 13 rotates, the driving pulley 23 that rotates together with the crankshaft rotates the driven pulley 24 and the cam 26 via the belt 25, and the cam 26 swings the intake and exhaust cam followers 32i and 32e in a timely manner. These swings are transmitted to the intake and exhaust rocker arms 33i and 33e via the corresponding rocker shafts 31i and 31e to swing them, and in cooperation with the intake and exhaust springs 34i and 34e, The intake and exhaust valves 18i and 18e can be opened and closed at appropriate times.
[0045]
  In the timing transmission device 22a, the driven pulley 24 and the cam 26 are rotatably supported on a support shaft 29, and the support shaft 29 is also rotatably supported on both side walls of the first valve chamber 21a. During rotation of the cam 24 and the cam 26, the support shaft 29 is also rotated by friction and the rotational speed difference between the driven pulley 24 and the cam 26 and the support shaft 29 is reduced, and wear of the rotary sliding portion is reduced. Can contribute to the improvement of durability.
[0046]
  By the way, the relatively large-diameter cam 26 is disposed on one side of the cylinder head 8 together with the driven pulley 24. The intake and exhaust rocker arms 33i and 33e and the relatively small-diameter intake and exhaust rocker shaft 31i are directly above the cylinder head 8. , 31e is not disposed, the valve operating mechanism 22 is not greatly bulky above the cylinder head 8, and the overall height of the engine E can be reduced, and thus the engine E can be made compact.
[0047]
  Further, the support shaft 29 and the intake and exhaust rocker shafts 31i and 31e are disposed above a series of annular seal beads 87 at the upper ends of the cylinder head 8 and the belt guide tube 86. Therefore, in a state where the head cover 36 is removed. The support shaft 29 and the intake and exhaust rocker shafts 31i and 31e can be assembled and disassembled without being obstructed by the seal bead 87, and the assemblability and maintainability are extremely good.
[0048]
  Next, the lubrication system of the engine E will be described with reference to FIGS.
[0049]
  4 and 5, the oil tank 40 stores a predetermined amount of lubricating oil O injected from the oil supply port 40a. In the oil tank 40, a pair of oil slinger 56a, 56b arranged in the axial direction with the drive pulley 23 interposed therebetween is fixed to the crankshaft 13 by press fitting or the like. These oil slinger 56a, 56b are directed to opposite radial directions and bent so that their tips are separated from each other in the axial direction. When the oil slinger 56a, 56b is driven to rotate by the crankshaft 13, At least one of the both oil slinger 56a and 56b stirs and scatters the stored oil O in the oil tank 40 to generate oil mist. At this time, the generated oil splashes are sprinkled on the part of the timing transmission device 22a exposed in the oil tank 40 from the first valve operating chamber 21a or enter the first valve operating chamber 21a to adjust the oil. The hour transmission device 22a is directly lubricated, and this is one lubrication system.
[0050]
  As shown in FIGS. 3 to 5 and FIG. 12, the other lubrication system includes a through hole 55 provided in the crankshaft 13 to communicate between the inside of the oil tank 40 and the crank chamber 6a, and a crank chamber. An oil feed conduit 60 disposed outside the engine body 1 to connect the lower part of 6a to the lower part of the second valve chamber 21b, and a cylinder head 8 for sucking up the liquefied and accumulated oil in the second valve chamber 21b. An oil suction chamber 74 provided in the cylinder, an oil return passage 78 formed between the cylinder head 8 and the oil tank 40 to communicate the oil suction chamber 74 with the oil tank 40 through the first valve chamber 21a, a crank And a one-way valve 61 that is installed in the lower portion of the chamber 6a and allows oil mist to flow from the crank chamber 6a to the oil feed conduit 60 in only one direction.
[0051]
  The opening end 55a of the through hole 55 into the oil tank 40 is always exposed on the liquid level of the oil O in the oil tank 40 in any posture of the engine E. Arranged at or near the center. The drive pulley 23 to which the crankshaft 13 is fixed and the one oil slinger 56a are arranged with the opening end 55a therebetween so as not to block the opening end 55a.
[0052]
  The one-way valve 61 (see FIG. 3) is constituted by a reed valve in the illustrated example, and closes when the crank chamber 6a becomes negative pressure due to the reciprocating motion of the piston 15, and opens when positive pressure is reached. It is supposed to do.
[0053]
  The lower end of the oil feed conduit 60 is a lower connecting pipe 62a (see FIG. 3) protruding from the outer surface of the crankcase 6, and the upper end is an upper connecting pipe protruding from the outer surface of the cylinder head 8. 62b (see FIG. 4 and FIG. 8) are respectively fitted and connected. The inside of the upper connecting pipe 62b communicates with the lower part of the second valve chamber 21b via a communication path 63 (see FIGS. 8 and 9) having a large passage area formed on the cylinder head 8 on the one hand, The oil return passage 78 communicates with the orifice-shaped bypass 64 (see FIG. 8).
[0054]
  As shown in FIGS. 5, 10, and 11, the ceiling wall of the head cover 36 includes a plurality of partition plates 65 that project from the ceiling wall and define a breather chamber 69 in the upper part of the cover 36. The breather chamber 69 is attached by a column 66 and a clip 67 locked to the column 66, and the breather chamber 69 is a communication pipe having a large flow area protruding toward the second valve chamber 21b formed integrally with the partition plate 65. 68 and a gap g between the inner surface of the head cover 36 of the partition plate 65 and the second valve chamber 21b, and the air cleaner 4 is communicated with the air cleaner 4 via a breather pipe 70. The breather chamber 69 performs gas-liquid separation of mixed oil and blow-by gas, and a maze wall 72 for promoting the gas-liquid separation projects from the inner surface of the ceiling wall of the head cover 36.
[0055]
  A T-shaped box 79 is welded to the partition plate 65 between the upper surface of the partition plate 65 and the oil suction chamber 74 in a plan view, so that the oil suction chamber 74 is also T-shaped.
[0056]
  The partition plate 65 is integrally provided with two suction pipes 75 communicating respectively with two locations corresponding to both ends of the T-shaped horizontal bar of the oil suction chamber 74. These suction pipes 75 have their respective distal ends extending to the vicinity of the bottom surface of the second valve operating chamber 21b, and the respective distal end openings serve as orifices 75a.
[0057]
  Further, on the upper wall of the box 79, three sucking pipes 76 that respectively communicate with three positions corresponding to the tip portions of the T-shaped horizontal bar and vertical bar of the oil sucking chamber 74 are integrally projected. These suction pipes 76 have their respective distal ends extending to the vicinity of the ceiling surface of the breather chamber 69, and their distal end openings serve as orifices 76a.
[0058]
  Further, the upper wall of the box 79 is provided with an orifice 80 that communicates the depression 65 a on the upper surface thereof with the suction chamber 74.
[0059]
  The partition plate 65 is integrally provided with a single conduit 81 communicating with the portion of the oil suction chamber 74 that contacts the tip of the T-shaped vertical bar. The tip of the conduit 81 is connected to the second valve chamber. A grommet 82 is fitted into the inlet 78a of the oil return passage 78 that opens to the bottom surface of 21b. Thus, the suction chamber 74 is connected to the oil return passage 78. The conduit 81 is disposed in the vicinity of one inner side surface of the second valve operating chamber 21b, and an oil suction orifice that communicates the second valve operating chamber 21b in the conduit 81 with a portion close to the inner side surface. 81a is drilled.
[0060]
  Thus, since the breather chamber 69 communicates with the air cleaner 4 via the breather pipe 70, the pressure of the breather chamber 69 is maintained at substantially atmospheric pressure even during operation of the engine E, and flows into the breather chamber 69. The second valve operating chamber 21 b communicating with the communication pipe 68 having a small path resistance has substantially the same pressure as the breather chamber 69.
[0061]
  Since the crank chamber 6a discharges only the positive pressure component of the pressure pulsation generated by the raising and lowering of the piston 15 during the operation of the engine E from the one-way valve 61 to the oil feed conduit 60, the crank chamber 6a is in an average negative pressure state. Thus, the second valve operating chamber 21b receiving the positive pressure communicates with the breather chamber 69 through the communication pipe 68 having a small flow path resistance, and therefore has substantially the same pressure as the breather chamber 69. The negative pressure in the crank chamber 6a is transmitted to the oil tank 40 through the through hole 55 of the crankshaft 13, and further transmitted to the suction chamber 74 through the oil return passage 78. Therefore, the suction chamber 74 is connected to the second valve chamber. The oil tank 40 and the first valve operating chamber 21a have a lower pressure than the suction chamber 74.
[0062]
  Therefore, as shown in FIG. 12, the pressure of the crank chamber 6a is Pc, the pressure of the oil tank 40 is Po, the pressure of the first valve chamber 21a is Pva, the pressure of the second valve chamber 21b is Pvb, and the suction chamber 74 , Ps, and Pb of the breather chamber 69, the magnitude relationship can be expressed by the following equation.
[0063]
            Pvb = Pb> Ps> Po = Pva> Pc
  As a result, the pressure in the second valve chamber 21b and the breather chamber 69 moves to the suction chamber 74 through the suction pipes 75 and 76 and the orifice 80, further to the oil tank 40 through the oil return passage 78, and to the crank chamber 6a.
[0064]
  During operation of the engine E, oil mist is generated in the oil tank 40 by the oil slinger 56a, 56b rotated by the crankshaft 13 stirring and scattering the lubricating oil O. The splash of oil generated at that time is sprinkled on a part of the timing transmission device 22a exposed from the belt guide tube 86 into the oil tank 40, that is, a part of the drive pulley 23 and the timing belt 25, or the first valve valve. As described above, the timing transmission device 22a is directly lubricated by entering the chamber 21a.
[0065]
  The oil mist generated in the oil tank 40 is sucked into the crank chamber 6a through the through hole 55 of the crankshaft 13 according to the pressure flow described above, and lubricates the piston 15 around the crankshaft 13. Next, when the crank chamber 6a reaches a positive pressure due to the lowering of the piston 15, the one-way valve 61 opens, and the oil mist rises along with the blow-by gas generated in the crank chamber 6a along the oil feed conduit 60 and the communication passage 63 to the second motion. It is supplied to the valve chamber 21b and lubricates each part of the cam device 22b in the chamber 21b, that is, the intake and exhaust rocker arms 33i and 33e.
[0066]
  In this case, a part of the oil mist passing through the communication path 63 is short-circuited from the orifice-shaped bypass 64 to the oil return path 78. Therefore, the amount of oil mist supplied to the second valve chamber 21b can be adjusted by appropriately setting the flow path resistance of the bypass 64.
[0067]
  When oil mist and blow-by gas in the second valve chamber 21 b move to the breather chamber 69 through the gap g around the communication pipe 68 and the partition plate 65, the oil mist and blow-by gas are caused by the expansion action and the collision action with the maze wall 72 at that time. The gas-liquid separation is performed, and the blow-by gas is sucked into the engine E through the breather pipe 70 and the air cleaner 4 in order during the intake stroke of the engine E.
[0068]
  In the erecting state of the engine E, the oil liquefied in the breather chamber 69 accumulates in the recess 65a on the top surface of the box 79, or flows down through the communication pipe 68 and the gap g and accumulates on the bottom surface of the second valve chamber 21b. These are sucked up to the suction chamber 74 by the orifice 80 or the suction pipe 75 waiting in the place. In the inverted state of the engine E, the liquefied oil accumulates on the ceiling surface of the head cover 36, and is therefore sucked up into the suction chamber 74 by the suction pipe 76 waiting at that location.
[0069]
  The oil sucked into the suction chamber 74 in this way returns to the oil tank 40 from the conduit 81 through the oil return passage 78. In this case, as shown in the example, when the oil return passage 78 is communicated with the oil tank 40 via the second valve chamber 21b, the oil that has exited the oil return passage 78 is sprinkled on the timing transmission device 22a. It will contribute to lubrication and is convenient.
[0070]
  On the other hand, in the oil tank 40, when the engine E is turned upside down as shown in FIG. 13, the stored oil O moves to the ceiling side of the tank 40, that is, the first valve chamber 21a side. The opening end of the valve operating chamber 21a into the oil tank 40 is set by the belt guide tube 86 so as to occupy a position higher than the liquid level of the stored oil O. Therefore, the valve valve chamber 21a is stored in the second valve operating chamber 21b. Inflow of oil O is not allowed, excessive oiling of the timing transmission 22a can be prevented, a predetermined amount of oil is secured in the oil tank 40, and oil mist is continuously generated by the oil slinger 56a, 56b. Is possible.
[0071]
  As shown in FIG. 14, when the engine E is placed on its side, the stored oil O moves to the side surface of the tank 40. However, the open end of the first valve chamber 21a into the oil tank 40 Is set so as to occupy a position higher than the liquid level of the stored oil O by the belt guide cylinder 86. Therefore, in this case as well, the inflow of the stored oil O into the second valve operating chamber 21b is not allowed and the timing is adjusted. Excess oiling of the transmission 22a can be prevented, and a predetermined amount of oil can be secured in the oil tank 40, and oil mist can be continuously generated by the oil slinger 56a, 56b.
[0072]
  Thus, the lubrication system of the valve mechanism 22 includes a system that lubricates part of the oil tank 40 and the timing transmission device 22a and the cam device 22b in the first valve chamber 21a with the scattered oil in the oil tank 40, and the first system. Since the oil mist transferred to the second valve chamber 21b is divided into two systems, the system that lubricates the remaining portion of the cam device 22b in the second valve chamber 21b, the burden on each lubrication system is reduced. Thus, the entire valve mechanism 22 can be lubricated uniformly. In addition, the use of oil splashes and oil mist can reliably lubricate each part of the engine in any operating position of the engine.
[0073]
  Also, since the oil mist in the oil tank 40 is circulated using the pressure pulsation of the crank chamber 6a and the one-way transfer function of the one-way valve 61, the oil mist is circulated. An oil pump is unnecessary, and the structure can be simplified.
[0074]
  In addition to the oil tank 40, the oil feed conduit 60 that connects between the crank chamber 6a and the second valve chamber 21b is disposed outside the engine body 1, and thus prevents any reduction in the thickness and size of the engine body 1. Therefore, the engine E can be greatly reduced in weight. In particular, the externally arranged oil feed conduit 60 is not easily affected by heat from the engine body 1 and easily dissipates heat, so that cooling of the oil mist passing therethrough can be promoted.
[0075]
  Further, since the oil tank 40 is disposed on the outer side of the engine body 1, the overall height of the engine E can be greatly reduced, and a part of the timing transmission device 22a is housed in the oil tank 40, so that the engine The increase in the lateral width of E can be suppressed as much as possible, and the size can be reduced.
[0076]
  The present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the scope of the gist thereof. For example, instead of the one-way valve 61, it is possible to provide a rotary valve that operates in conjunction with the crankshaft 13 so that the oil feed conduit 60 is turned on when the piston 15 is lowered and shut off when the piston 15 is raised. Further, the number and installation locations of the oil suction pipes 75 and 76 and the suction orifices 80 and 81a can be freely selected.
[0077]
【The invention's effect】
  As described above, according to the first feature of the present invention, an engine body comprising a crankcase having a crank chamber, a cylinder block having a cylinder bore, and a cylinder head having an intake port and an exhaust port, and the crankcase is supported by the crankcase. A crankshaft housed in the crankcase, an intake valve and an exhaust valve attached to the cylinder head to open and close the intake port and exhaust port, and a valve that drives the intake valve and exhaust valve to open and close in conjunction with the rotation of the crankshaft In a four-cycle engine comprising a mechanism and a power take-off mechanism provided at one end of the crankshaft protruding outward from the engine body, the other end of the crankshaft is located outside the engine body on the opposite side of the power take-out mechanism. Of the oil tank that faces the inside and the valve mechanism connected to the crankshaft in this oil tank Since the timing device is lubricated by the oil in the oil tank, there is no need to provide a special chamber for accommodating the timing device on the side wall of the engine body. Due to the lateral arrangement of the tank, the overall height of the engine is lowered, so that the engine body side wall can be made thinner and more compact, and the overall weight of the engine can be significantly reduced. Moreover, the power take-off mechanism arranged on one side of the engine body and the timing transmission and oil tank arranged on the other side provide a good weight balance at both ends of the crankshaft so that the center of gravity of the engine It will be as close to the center as possible, and combined with weight reduction, the engine workability can be improved. Also, during engine operation, the load applied to the timing transmission and power take-off mechanism is distributed to both ends of the crankshaft, avoiding concentration of load on the crankshaft and its bearings, and improving their durability. Can be improved. Furthermore, since the timing transmission is directly lubricated with the oil in the oil tank, the lubrication system can be simplified.
[0078]
  According to the second feature of the present invention, the cooling fan having a larger diameter than the power take-off mechanism is fixed to the crankshaft between the engine body and the power take-out mechanism. The enlargement of E can be avoided as much as possible.
[0079]
  Further, according to the third feature of the present invention, a cam device for transmitting the rotation of the driven side of the timing transmission device to the intake and exhaust valves as an opening / closing force is disposed in the valve chamber provided in the cylinder head. Since the oil mist generating means is connected to the crankshaft to generate oil mist to be supplied to the valve chamber in the oil tank, the lubrication system of the valve mechanism is a system that directly lubricates the timing transmission with the oil in the oil tank. And the system that lubricates the cam device by the oil mist generated in the oil tank, the burden on each lubrication system is reduced, and the entire valve mechanism is lubricated uniformly. be able to.
[Brief description of the drawings]
FIG. 1 is a perspective view showing one use example of a four-cycle engine of the present invention.
FIG. 2 is a longitudinal side view of the four-cycle engine.
3 is a cross-sectional view taken along line 3-3 in FIG.
4 is a cross-sectional view taken along line 4-4 of FIG.
FIG. 5 is an enlarged cross-sectional view of the main part of FIG.
6 is an exploded view of the main part of FIG.
7 is a cross-sectional view taken along line 7-7 in FIG.
8 is a cross-sectional view taken along line 8-8 in FIG.
9 is a cross-sectional view taken along line 9-9 in FIG.
10 is a view taken along arrow 10-10 in FIG. 5 (a bottom view of the head cover).
11 is a sectional view taken along line 11-11 in FIG.
FIG. 12 is a lubrication route diagram of the engine.
FIG. 13 is a view corresponding to FIG. 4, showing the engine in an inverted state.
14 is a view corresponding to FIG. 4, showing the engine on its side.
[Explanation of symbols]
E ··· Four-cycle engine
O ... oil
1. Engine body
6 .... Crankcase
6a ... Crank chamber
7. Cylinder block
7a: Cylinder bore
8. Cylinder head
9. Intake port
10 ... Exhaust port
13 ... Crankshaft
18i ... Intake valve
18e ... Exhaust valve
21a ... Valve chamber (first valve chamber)
21b ... Valve chamber (second valve chamber)
22 ... Valve mechanism
22a ··· Timing transmission device
22b... Cam device
40: Oil tank
43 ... Cooling fan
49 ... Power take-off mechanism (centrifugal clutch)
56a, 56b ... Oil mist generating means (oil slinger)
61 ... One-way valve
69 ... Breeza room
78 ... Oil return passage

Claims (3)

Crankcase (6) having a crank chamber (6a), cylinder block (7) having a cylinder bore (7a), and a cylinder head having a breather chamber (69) having an intake port (9) and an exhaust port (10) (8) the engine body (1), the crankshaft (13) supported by the crankcase (6) and housed in the crank chamber (6a), and the cylinder head (8) attached to the intake port (9 ) And an intake valve (18i) and an exhaust valve (18e) for opening and closing the exhaust port (10), and an operation for driving the intake valve (18i) and the exhaust valve (18e) to open and close in conjunction with the rotation of the crankshaft (13). A four-cycle engine comprising a valve mechanism (22) and a power take-off mechanism (49) provided at one end of the crankshaft (13) protruding outward from the engine body (1). In emissions,
An oil tank (40) with the other end of the crankshaft (13) facing the inside of the engine body (1) opposite to the power take-off mechanism (49), and a crank in the oil tank (40) A timing transmission device (22a) of a valve mechanism (53) connected to the shaft (13), and the timing transmission device (22a) is lubricated with oil in the oil tank (40);
Furthermore, the first valve chamber (21a) that communicates the valve chamber with the oil tank (40) and the second valve chamber (21b) that communicates with the crank chamber (6a) via the one-way valve (61). A partition, the first valve chamber (21a) and the second valve chamber (21b) communicate with each other via an oil return passage (78), and the liquefied oil separated by the breather chamber (69) is oiled. A four-cycle engine characterized in that the oil is returned to the oil tank (40) through the return passage (78) . The four-cycle engine according to claim 1,
A four-cycle engine characterized in that a cooling fan (43) having a larger diameter than that of the power take-off mechanism (49) is fixed to the crankshaft (13) between the engine body (1) and the power take-out mechanism (49). . The four-cycle engine according to claim 1,
A cam device (22b) for transmitting the rotation of the driven side of the timing transmission device (22a) to the intake and exhaust valves (18a, 18e) as an opening / closing force is arranged in the valve chamber (21b) provided in the cylinder head (8). The oil mist generating means (56a, 56b) is connected to the crankshaft (13) so as to generate oil mist supplied to the valve operating chamber (21b) in the oil tank (40). Four cycle engine.

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