JP2007263069A - Portable 4-cycle engine and working machine equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a 4-cycle engine applicable to working machines of different types, where no excessive lubrication oil can remain in a valve chamber no matter in any posture. <P>SOLUTION: The 4-cycle engine has three or more oil return passages 27, 28, 29 within a valve chamber 20 for circulating the lubrication oil supplied. These plural oil return passages join into a single oil passage outside the valve chamber 20. The suction port of at least one of these oil return passages is provided below the level of lubricant oil stored in the valve chamber. The opening of a breather passage 42 communicating with the valve chamber 20 is provided around the center of the valve chamber 20, so that at any posture of this 4-cycle engine in use, at least one suction port of these plural oil return passages can be positioned below the opening of the breather passage 42 communicating with the valve chamber 20. The oil return passages 27, 28, 29 are connected with the oil reservoir of the engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a portable four-cycle engine and a working machine equipped with the same, and more particularly to a portable four-cycle engine and a working machine equipped with the portable four-cycle engine in which lubrication performance does not deteriorate even when used in various postures.

  When a 4-cycle engine is mounted on a portable work machine, it is assumed that the 4-cycle engine will be used in various orientations. Therefore, the 4-cycle engine does not deteriorate in lubrication performance even if the work machine is used in various positions. Is required. Therefore, the lubricating devices described in Patent Document 1 and Patent Document 2 have been proposed.

  The 4-cycle engine described in Patent Document 1 includes a return oil passage that communicates the valve operating chamber and the oil reservoir chamber, and has an opening provided directly below the piston that is branched from the return oil passage and is at the top dead center position. An oil absorption passage that communicates is provided, and a check valve that opens when the engine stands upright and closes when the engine is inverted or tilted is provided in an opening connected to the oil reservoir chamber of the return oil passage. In such a four-cycle engine, when the engine is tilted or inverted, the check valve closes the opening, and the lubricating oil flows back from the oil reservoir chamber to the return oil passage so that the lubricating oil is excessive in the valve chamber. Supply is prevented.

  The 4-cycle engine described in Patent Document 2 includes an oil feed passage capable of communicating the oil reservoir chamber and the crank chamber, and a return oil passage communicating the valve train chamber and the oil reservoir chamber. Is configured to allow the supply of lubricating oil from the oil reservoir chamber to the crank chamber when the pressure becomes negative. For this reason, the excessive supply of the lubricating oil supplied from the oil feed passage to the crank chamber and the valve operating chamber communicating with the crankcase is prevented regardless of the change in the posture of the work implement.

JP-A-11-343822 Japanese Patent Laid-Open No. 2004-251231

  The portable four-cycle engine described in Patent Document 1 is provided with two return oil passages for returning the lubricating oil stored in the valve operating chamber to the oil reservoir chamber. Is provided with one return oil passage. Therefore, in any portable four-cycle engine, when the engine is inclined, the suction port at the end of the return oil passage moves onto the oil surface of the stored lubricating oil, and the lubricating oil in the valve operating chamber is stored in the oil reservoir. Occasionally it will not return to the room If the lubricating oil does not return to the oil sump chamber, the misted lubricating oil liquefies and stays in the valve chamber in the process of lubricating the engine drive part, and if this liquefied lubricating oil stays excessively, poor circulation May occur, resulting in poor lubrication of the drive portion, or the release of liquefied lubricating oil from the breather port, resulting in an increase in consumption of the lubricating oil. As described above, the conventional portable four-cycle engine has a problem that the lubricating oil stored in the valve chamber cannot be normally circulated in any posture.

  For this reason, these conventional portable four-cycle engines are basically usable only within a certain allowable inclination range from the basic attitude of the engine. Therefore, depending on the type of work equipment, it is necessary to change the lubrication method according to the basic attitude of the different engines. A 4-cycle engine with various specifications is prepared, such as a brush cutter with horizontal specifications and a cultivator with vertical specifications. Therefore, it is desired to provide a portable four-cycle engine that can be mounted on different types of work machines.

  It is an object of the present invention to provide a portable four-cycle engine that can normally circulate lubricating oil stored in a valve chamber in any posture and can be mounted on different types of work machines, and a work machine equipped with the same. Objective.

  In order to solve such problems, in the present invention, lubricating oil stored in an oil sump chamber disposed in the vicinity of the crank chamber is accommodated in the crank chamber, the valve operating chamber or the like by utilizing the pressure fluctuation of the crank chamber. The drive parts (for example, the crankshaft 15, the intake valve 20a, the exhaust valve 20b, the valve drive gear 35, the cam gear 36, and the rocker arm 37 in the embodiment) are lubricated and circulated to communicate the valve chamber and the air cleaner. In a portable four-cycle engine that includes a breather passage and sends blow-by gas from the valve operating chamber to the breather passage and sends it to the air cleaner, a return oil passage for circulating lubricating oil sent to the valve operating chamber is provided in the valve operating chamber. The plurality of return oil passages are joined to one oil passage outside the valve operating chamber, and the opening communicating with the valve operating chamber in the breather passage is formed in the valve operating chamber. Provided near, the attitude portable four-stroke engine is used, at least one inlet of the plurality of oil return passage beneath the opening, characterized in that position.

  According to this invention, three or more return oil passages for circulating lubricating oil in the valve operating chamber are provided in the valve operating chamber, and these return oil passages join one oil passage outside the valve operating chamber. An opening communicating with the valve operating chamber of the breather passage is provided near the center of the valve operating chamber, and in a posture in which the portable four-cycle engine is used, at least one of the suction ports of the plurality of return oil passages is provided below the opening. By arranging them so that they are located, it is possible to prevent the lubricating oil from staying in the valve operating chamber in any posture in which the portable four-cycle engine is used, the lubrication oil circulation is good, and the lubrication state of the drive part is always maintained. A good portable four-cycle engine can be provided, and the state of staying in the valve operating chamber can be sent out from the valve operating chamber by utilizing the pressure fluctuation of the crank chamber. Furthermore, since the opening of the breather passage is unlikely to be below the surface of the liquid lubricating oil, the release of the lubricating oil from the breather passage is prevented, and an increase in the consumption of the lubricating oil can be prevented.

  The return oil passage of the present invention is connected to an oil reservoir.

  According to this invention, by connecting the return oil passage to the oil reservoir chamber, the lubricating oil can be sent from the valve operating chamber to the oil reservoir chamber, and deterioration of the lubricating oil can be suppressed.

  Further, according to the present invention, a one-way valve is provided in the middle of the lubricating oil circulation path, and the oil sump chamber always tends to be a negative pressure from the valve train chamber and the atmospheric pressure while the portable four-cycle engine is driven. A small hole is provided in the oil supply passage of the lubricating oil that communicates between the chamber and the crank chamber, and the small hole is formed on the oil surface of the lubricating oil stored in the oil reservoir chamber in a posture in which the portable four-cycle engine is used. It is possible to adjust the amount of lubricating oil flowing into the valve chamber by adjusting the size of the small hole, and by adjusting the inner diameter of the return oil passage in a range where the return oil passage is not clogged by dust or the like, The pressure is equal to or slightly more positive than the atmospheric pressure.

  According to this invention, the one-way valve is provided in the middle of the circulation path of the lubricating oil, and the oil reservoir chamber always tends to be negative pressure from the valve operating chamber and the atmospheric pressure during engine operation, and the oil reservoir chamber and the crank chamber are connected to each other. A small hole is provided in the communicating oil feeding passage, and the small hole is positioned on the oil surface of the lubricating oil in the oil reservoir chamber in a posture in which the portable four-cycle engine is used, and the valve chamber is adjusted by adjusting the size of the small hole. The amount of lubricating oil flowing into the valve can be adjusted, and the pressure inside the valve chamber is equal to or slightly more positive than the atmospheric pressure by adjusting the inner diameter of the return oil passage in a range where the return oil passage is not clogged by dust or the like. This prevents the occurrence of poor circulation of the lubricating oil lubrication system due to dust, etc., facilitates adjustment of the pressure in the valve chamber and the oil reservoir, and the amount of lubricating oil flowing into the valve chamber. Easy-to-adjust and portable 4-size with always good lubrication It is possible to provide a Le engine. Further, blow-by gas can be discharged from the lubrication system via the breather passage, and excessive lubrication oil can be prevented from being sent out.

  Furthermore, the suction ports of the plurality of return oil passages of the present invention are rotatably connected to a rotating shaft (for example, a drive shaft in the embodiment) that rotates in response to power from the crankshaft in the valve chamber. It is provided in the width direction both ends of the valve operating chamber by the side of the shaft connection part to support, and the side opposite to the shaft connection part side in a valve operating chamber, It is characterized by the above-mentioned.

  According to the present invention, the suction ports of the plurality of return oil passages are provided on both ends in the width direction of the valve operating chamber on the shaft connecting portion side and on the side opposite to the shaft connecting portion side in the valve operating chamber, whereby the shaft connecting portion When the portable four-cycle engine of the present invention is mounted on a work machine such as a cultivator that is used with its side inclined downward, a work machine with good lubrication performance can be provided.

  Further, the present invention is characterized in that a suction port of a return oil passage provided on the side opposite to the shaft coupling portion side in the valve operating chamber is provided near the center in the width direction of the valve operating chamber.

  According to this invention, the suction port of the return oil passage provided on the side opposite to the shaft coupling portion side in the valve operating chamber is provided in the vicinity of the center in the width direction of the valve operating chamber, thereby reducing the suction port of the return oil passage and It can arrange | position effectively and can suppress the raise of the cost of a portable 4 cycle engine.

  Further, the present invention is characterized in that the suction port of the return oil passage provided in the valve operating chamber is provided in the vicinity of the bottom surface in the valve operating chamber.

  According to the present invention, by providing the suction port of the return oil passage in the vicinity of the bottom surface in the valve operating chamber, the shaft connecting portion side of the portable four-cycle engine is inclined downward from the horizontal posture, and further, the crankshaft The suction port may be located below the surface of the lubricating oil even if the orientation is changed by about ± 90 ° in the lateral direction, or the shaft coupling side is inclined upward from the horizontal position. In addition, a portable four-cycle engine with good lubrication performance can be provided. For this reason, the portable four-cycle engine of the present invention can be mounted on most of the various working machines.

  Further, according to the present invention, the suction port located on the lower side in the vertical direction among the suction ports of the plurality of return oil passages is communicated with the oil reservoir chamber in accordance with the posture in which the portable four-cycle engine is used. An oil passage switching valve (for example, the switching device 70 and the switching component 77 in the embodiment) is provided to bring the suction port positioned on the upper side out of communication with the oil reservoir.

  According to the present invention, the suction port located on the lower side in the vertical direction communicates with the oil reservoir and the suction port located on the upper side in the vertical direction is connected to the oil sump chamber according to the posture in which the portable four-cycle engine is used. By providing an oil passage switching valve that is in a non-communication state, the return passage suction port is always located under the breather passage opening regardless of the orientation of the portable four-cycle engine. It is possible to prevent the lubricating oil from staying in the chamber. At the same time, the return oil passage is switched so that the suction port located on the upper side in the vertical direction is not in communication with the oil reservoir chamber, so the number of return oil passages communicating with the valve chamber and the oil reservoir chamber should be reduced. This makes it easy to adjust the pressure in the valve operating chamber and the oil reservoir chamber. For this reason, it is possible to provide a portable four-cycle engine with good lubrication performance in any posture, and the portable four-cycle engine of the present invention can be mounted on any work machine.

  Moreover, the present invention is a work machine equipped with the portable four-cycle engine according to any one of claims 1 to 7.

  According to the present invention, since the working machine is equipped with the portable four-cycle engine according to any one of claims 1 to 7, the working is performed by the portable four-cycle engine having good lubrication performance and less deterioration of lubricating oil. It is possible to provide a work machine that is driven and has a good work performance and little maintenance.

  According to the present invention, the work machine is a brush cutter.

  According to the present invention, even if the brush cutter is used in various postures by using the working machine as a brush cutter, the performance of the portable four-cycle engine is stable regardless of the working posture, and the working performance is improved. A brush cutter that is always good and requires little maintenance can be provided.

  According to the portable four-cycle engine of the present invention, three or more return oil passages for circulating lubricating oil in the valve chamber are provided in the valve chamber, and these return oil passages are provided outside the valve chamber. In this way, the oil is joined to one oil passage, and at least one suction port of the plurality of return oil passages is provided below the lubricating oil level in the valve chamber before excessive lubrication oil stays. To provide a portable four-cycle engine that can prevent excessive stagnation in a valve chamber and to circulate lubricating oil normally in any posture and can be mounted on different types of work machines, and a work machine equipped with the same. Can do.

  A preferred embodiment of a portable four-cycle engine of the present invention and a work machine equipped with the same will be described below with reference to FIGS. First, before describing the working machine of the present invention, a portable four-cycle engine mounted on the working machine will be described. Note that the portable four-cycle engine will be described in a state where it is in a horizontal posture.

[First embodiment]
A portable four-cycle engine (hereinafter simply referred to as “four-cycle engine 1”) is integrated with a cylinder head 3a as shown in FIG. 1 (an explanatory diagram of a lubrication state) and FIG. 2 (a cross-sectional view). A cylinder block 3, a crankcase 5 that is attached to the lower portion of the cylinder block 3 to form a crank chamber 5 a, and an oil reservoir chamber 7 that is attached to the lower portion of the crankcase 5 are provided. The oil reservoir 7 stores the lubricating oil A and is partitioned from the crankcase 5 to form a sealed space as a whole.

  In the oil reservoir chamber 7, a suction cylinder portion 8 for sucking the lubricating oil A stored therein is provided, and a one-way valve 10 is provided in the middle of an oil feed passage 9 connecting the suction cylinder portion 8 and the crank chamber 5. It has been. The one-way valve 10 is configured to be openable and closable according to a change in pressure in the crank chamber 5a. The suction cylinder portion 8 includes a tube body 8a that is formed of an elastic material such as rubber and can be easily bent, and a weight 8b with a suction port attached to a distal end portion of the tube body 8a. In other words, the weight 8b of the suction cylinder portion 8 is attached so as to be always movable vertically downward due to its gravity, so that even if the oil reservoir 7 is tilted, the suction cylinder portion 8 suctions below the oil level of the lubricating oil A. I can immerse my mouth.

  An opening on the oil reservoir chamber side of the oil feed passage 9 is provided near the upper center of the oil reservoir chamber 7, and the oil level is always maintained regardless of the posture of the four-cycle engine 1 unless the four-cycle engine 1 is reversed and used. Located above and connected to the suction cylinder 8. A small hole 9 a is formed in the vicinity of the opening of the oil feeding passage 9. The diameter of the small hole 9a will be described later. The oil reservoir chamber 7 and the crank chamber 5a are further in communication with each other via a pressure adjusting passage 12. A one-way valve 13 is provided in the pressure adjusting passage 12, and the one-way valve 13 is configured to be openable and closable according to a change in pressure in the crank chamber 5. The opening on the oil reservoir chamber side of the pressure adjusting passage 12 is formed in the vicinity of the upper center of the oil reservoir chamber 7, and the oil level is always maintained no matter what posture is used unless the four-cycle engine 1 is reversed and used. It is designed to be located above.

  A crankshaft 15 is rotatably supported on the crankcase 5, and the piston 16 is connected so as to reciprocate in conjunction with the rotation of the crankshaft 15. The piston 16 is slidably inserted into a cylinder 3 b provided inside the cylinder block 3.

  A shaft coupling portion 18 that couples and supports a work shaft of a working machine (not shown) is provided on the distal end side of one end portion of the crankshaft 15. The cylinder block 3 is formed with an intake port and an exhaust port communicating with a carburetor and an exhaust muffler (not shown). Each of these ports is provided with an intake valve 20a and an exhaust valve 20b for opening and closing the ports, and each port communicates with the combustion chamber 3c by opening and closing each valve. An air cleaner 50 is attached to the vaporizer.

  These valves are driven via components such as a valve drive gear 35, a cam gear 36, a cam follower, a bush rod, and a rocker arm 37. A valve operating chamber 20 is formed in the upper part of the cylinder block 3, and components such as a rocker arm 37 are accommodated in the valve operating chamber 20. The valve operating chamber 20 and the crank chamber 5a communicate with each other via a cam gear chamber 38, and a valve drive gear 35, a cam gear 36, and the like are accommodated in the cam gear chamber 38. A reed valve 5b is provided between the crank chamber 5a and the cam gear chamber 38.

  The valve operating chamber 20 and the oil reservoir chamber 7 communicate with each other via a return oil passage 40, and an opening on the oil reservoir chamber side of the return oil passage 40 is formed near the upper center of the oil reservoir chamber 7. As long as 1 is not reversed and used, it is always positioned on the oil level no matter what posture it is used in.

  The connection ports on the crank chamber side of the oil feeding passage 9 and the pressure adjusting passage 12 are configured to open to the crank chamber 5a when the piston 16 moves up and the crank chamber 5a tends to become negative pressure. The position of the connection port is preferably fully opened when the piston 16 reaches the vicinity of the top dead center, and this state is preferably maintained until the piston 16 reaches the top dead center. When the oil feeding passage 9 and the pressure adjusting passage 12 communicate with the crank chamber 5a, the crank chamber 5a tends to be negative pressure, so that the one-way valves 10 and 13 are opened and the oil reservoir chamber 7 and the crank chamber are opened. 5 a communicates with the oil feed passage 9 and the pressure adjustment passage 12. At this time, the lubricating oil A is sucked up from the oil reservoir chamber 7 through the oil supply passage 9 and supplied to the crank chamber 5a.

  The supply amount of the lubricating oil A supplied to the oil reservoir 7 and the crank chamber 5a is adjusted by the pressure adjusting passage 12 and the small hole 9a described above. The pressure adjusting passage 12 can sufficiently supply the air in the oil reservoir chamber 7 to the crank chamber 5a to obtain a sufficient pressure in the crank chamber 5a, and can limit the suction pressure in the oil feeding passage 9. become. Furthermore, the amount of the lubricating oil A supplied to the crank chamber 5a can be easily adjusted by setting the diameter of the small hole 9a to an arbitrary size.

  The lubricating oil A introduced into the crank chamber 5a is converted into a mist by the driving parts of the crank chamber 5a to become an oil mist, and the inside of the crank chamber 5a is sufficiently lubricated. When the crank chamber 5a tends to have a positive pressure, the reed valve 5b opens, and when the crank chamber 5a tends to have a negative pressure, the reed valve 5b closes. As the piston 16 moves from the top dead center to the bottom dead center, the crank chamber 5a tends to become positive pressure, and the oil mist in the crank chamber 5a is sent to the cam gear chamber 38 and the valve train chamber 20, and the cam gear chamber 38 and Lubricate the driving parts of the valve train chamber 20. The oil mist sent to the valve operating chamber 20 is returned to the oil reservoir 7 through the return oil passage 40 using the pressure difference between the valve operating chamber 20 and the oil reservoir 7.

  Although a large pressure change can be obtained in the crank chamber 5a, the valve operating chamber 20 always tends to be positive with respect to the oil reservoir chamber 7 by the action of the one-way valves 10 and 13 and the reed valve 5b. . The pressure difference between the valve operating chamber 20 and the oil reservoir 7 changes according to the pressure change in the crank chamber 5a, but does not change as much as the pressure change in the crank chamber 5a.

  The valve operating chamber 20 communicates with the air cleaner 50 via the breather passage 42. A one-way valve 43 is provided in the breather passage 42. The breather passage 42 is provided for the purpose of discharging blow-by gas, and the air containing oil mist and blow-by gas in the valve operating chamber 20 flows through the breather passage 42 and is supplied to the air cleaner 50. The one-way valve 43 restricts the backflow of air from the air cleaner 50 to the valve operating chamber 20 side.

  The air cleaner 50 is provided with a return oil passage 45 for circulating the lubricating oil separated from the gas and liquid by the oil separator 50 a to the crank chamber 5 a. The return oil passage 45 is a one-way valve 10 of the oil feed passage 9. It communicates with the oil feeding passage 9 on the further downstream side. The return oil passage 45 is provided with a one-way valve 46 that allows only the flow toward the oil feed passage.

  The air containing oil mist and blow-by gas flowing into the air cleaner 50 from the valve operating chamber 20 through the breather passage 42 is separated into liquefied lubricating oil and blow-by gas in the air cleaner 50, and the blow-by gas is supplied to the vaporizer together with the air. The sent and liquefied lubricating oil is sent to the crank chamber 5a. The opening 42a on the valve operating chamber 20 side of the breather passage 42 is formed near the upper center of the valve operating chamber 20, and even if the oil mist is liquefied and stays in the valve operating chamber 20, the breather passage 42 can be easily formed. Therefore, it is possible to prevent an increase in the consumption amount of the lubricating oil.

  The valve operating chamber 20 is shown in FIG. 1, FIG. 3 (a) (sectional view), FIG. 3 (b) (plan view), and FIG. 4 (plan view corresponding to the arrow III-III in FIG. 3 (a)). Thus, the lower part is partitioned off by the cylinder block 3. A pair of rocker arms 37 are disposed along the crankshaft 15 on both sides of the valve shaft 20 with the crankshaft 15 as the center, and valves 20a and 20b, a valve spring 20c and the like are mounted on each rocker arm 37. ing. The valve train chamber 20 has a side plate portion 22 that surrounds the rocker arm 37 and a top plate portion 23 that is disposed above the rocker arm 37 and closes the upper opening of the side plate portion 22, and is formed in a top box shape. This is an internal space inside the housing 21, and the housing 21 is mounted on the top of the cylinder block 3. A lid member 25 is placed on the upper portion of the housing 21, and the lid member 25 and the housing 21 are fastened to the cylinder block 3 by bolts 26 or the like.

  The top plate portion 23 is provided with return oil passages 27, 28 and 29 extending into the valve operating chamber 20. The return oil passages 27 and 28 are provided at the end portion on the shaft connecting portion 18 side shown in FIG. 2, and the return oil passage 29 is provided on the side opposite to the shaft connecting portion side. The return oil passage 27 is provided in the vicinity of one end in the width direction where the rocker arms 37 are juxtaposed, the return oil passage 28 is provided in the vicinity of the other end in the width direction, and the return oil passage 29 is in the vicinity of the center in the width direction. Each of them extends to a position near the upper surface of the cylinder block 3 serving as a bottom surface, and a suction port is opened at each tip.

  The return oil passages 27, 28, and 29 each have the same inner diameter and communicate with a return oil passage 30 formed between the lid member 25 and the top plate portion 23. The return oil passages 30 join together to be connected to the return oil passage 40. The return oil passage 30 and the return oil passage 40 can be easily connected by using an elastic material tube such as heat-resistant rubber (not shown). The sectional area of the inner diameter of the return oil passage 40 is larger than the sum of the sectional areas of the inner diameters of the three return oil paths 27, 28, and 29.

  A breather port 24 is provided near the center of the top plate part 23. The breather port 24 extends to the vicinity of the center of the valve operating chamber 20 and communicates with a breather passage 31 formed in the lid member 25. Although not shown, the breather passage 31 and the breather passage 42 can be easily connected by using an elastic material tube such as heat-resistant rubber. A heat-resistant packing may be inserted between the lid member 25 and the top plate portion 23 and between the side plate portion 22 and the upper surface of the cylinder block 3.

  As described above, the valve operating chamber 20 always tends to have a positive pressure with respect to the oil reservoir 7, but the valve operating chamber 20 should be equal to the atmospheric pressure or slightly positive from the atmospheric pressure. . Under this condition, it is preferable that the valve chamber 20 has a positive pressure tendency with respect to the oil reservoir chamber 7. Further, it is preferable to reduce the inflow amount of the lubricating oil into the valve operating chamber 20 as much as possible within a range where the driving state of the driving components of the four-cycle engine 1 can be maintained.

  Adjustment of the inflow amount of the lubricating oil into the valve operating chamber 20 is mainly performed by adjusting the diameters of the pressure adjusting passage 12 and the small hole 9a. As described above, the amount of lubricating oil fed from the oil reservoir 7 to the crank chamber 5a is adjusted, and the amount of lubricating oil flowing from the crank chamber 5a through the cam gear chamber 38 into the valve operating chamber 20 is limited. The In this way, the relationship between the valve operating chamber 20, the oil reservoir 7, and the atmospheric pressure is adjusted, and the amount of lubricating oil flowing into the valve operating chamber 20 is adjusted, so that the oil stays in the valve operating chamber 20. The lubricating oil can be easily discharged into the oil reservoir chamber 7.

  The oil mist flowing into the valve operating chamber 20 liquefies and stays in the valve operating chamber 20 for a long time. If this lubricating oil stays excessively, problems occur as described above. , 28, 29, when at least one of the intake ports is below the level of the accumulated lubricating oil, the outflow amount becomes higher than the inflow amount of the lubricating oil into the valve operating chamber 20, and the lubricating oil is excessive in the valve operating chamber 20. It can prevent staying.

  If at least one of the suction ports of the three return oil passages 27, 28, and 29 is positioned below the breather port 24, it is possible to prevent the lubricating oil from staying excessively in the valve operating chamber 20. At the same time, it is difficult for the liquefied lubricating oil to be released from the breather port 24, and an increase in the consumption amount of the lubricating oil can be prevented.

  When the 4-cycle engine 1 configured as described above is mounted on a brush cutter, which is an example of a work machine, the effects of the 4-cycle engine 1 described above can be significantly increased. As shown in FIG. 5 (side view), the brush cutter 60 equipped with the 4-cycle engine 1 is rotatable at the front end portion of the operation rod 61 and the 4-cycle engine 1 mounted on the rear end portion of the operation rod 61. And a safety cover 63 attached to the front end of the operating rod 61 so as to cover the cutting blade 62.

  A gear head 64 is attached to the front end portion of the operation rod 61. A drive shaft (not shown) of the four-cycle engine 1 and the gear head 64 are connected via a drive shaft (not shown) provided in the operation rod 61, and the gear head is connected. The power from the 4-cycle engine 1 can be transmitted to 64. A cutting blade 62 is attached to the gear head 64, and the power of the four-cycle engine 1 is transmitted to the cutting blade 62 via the gear head 64 to rotate.

  A handle 65 is attached to an intermediate portion of the operating rod 61, and a control lever (not shown) for adjusting the power of the 4-cycle engine 1 is attached to the handle 65. The worker M performs the brushing work by holding and operating the handle 65.

  Here, FIGS. 6 (a) to (d) and FIGS. 7 (e) to (k) are side views for explaining an assumed working posture of the brush cutter 60 equipped with the four-cycle engine 1. FIGS. 8A to 8D and FIGS. 9E to 9K illustrate the staying state of the lubricating oil in the valve operating chamber 20 corresponding to the working posture of the brush cutter 60 shown in FIGS. Sectional drawing for doing is shown. Note that the brush cutter 60 shown in FIG. 7 (h) is in the normal working state.

  In the assumed work posture of the brush cutter 60 shown in FIGS. 6 (a) to 6 (d) and FIGS. 7 (e) to (k), FIGS. 8 (a) to 8 (d) and FIGS. ), At least one of the suction ports of the three return oil passages 27, 28, 29 is always located below the breather port 24. Further, even if the lubricating oil A stays inside the valve operating chamber 20, before the lubricating oil A stays on the breather port 24, the lubricating oil A is discharged to the oil reservoir 7 shown in FIG. It is possible to prevent excessive lubricating oil from staying in the valve operating chamber 20.

  In particular, in the working posture shown in FIGS. 6C and 6D, as shown in FIGS. 8C and 8D, the oil level of the lubricating oil A that is assumed and the breather port 24 are assumed. However, since the lubricating oil A staying in the breather port 24 is not easily covered, the liquefied lubricating oil A is not discharged from the breather port 24.

  As described above, even if the above-described four-cycle engine 1 is mounted on the brush cutter 60 whose working posture greatly changes, excessive retention of lubricating oil does not occur in the valve operating chamber 20 in the assumed working posture. Also, the liquefied lubricating oil is not released from the breather port 24. The four-cycle engine 1 described above can also be used for a cultivator that is normally used in a so-called vertical posture in which the shaft connecting portion 18 extends downward.

[Second Embodiment]
Next, a second embodiment of the four-cycle engine 1 of the present invention will be described. In the second embodiment, only differences from the first embodiment described above will be described, and the same reference numerals will be given to the same aspects as those in the first embodiment, and the description thereof will be omitted.

  As shown in FIGS. 1, 10 (a) (sectional view) and 10 (b) (plan view), the valve chamber 20 of the four-cycle engine 1 includes four return oil passages 27, 28, 52, 53 is provided. The return oil passage 52 and the return oil passage 53 are provided on the side opposite to the shaft coupling portion side, the return oil passage 52 is provided in the vicinity of one end side in the width direction where the rocker arms 37 are arranged in parallel, and the return oil passage 53 has a width. It is provided in the vicinity of the other end side in the direction. The four return oil passages 27, 28, 52, 53 each extend to a position near the top surface of the cylinder block 3, which is the bottom surface, and a suction port is opened at the tip of each oil passage. The four return oil passages 27, 28, 52, 53 each have the same inner diameter, communicate with a return oil passage 30 ′ formed between the lid member 25 and the top plate portion 23, and return oil passage 30. 'Are joined together and connected to the return oil passage 40 shown in FIG. The sectional area of the inner diameter of the return oil passage 40 is larger than the sum of the sectional areas of the inner diameters of the four return oil paths 27, 28, 52, 53.

  The pressure adjustment of the valve operating chamber 20 is mainly performed by adjusting the inner diameters of the pressure adjustment passage 12 and the four return oil passages 27, 28, 52, 53. Further, the adjustment of the inflow amount of the lubricating oil A into the valve operating chamber 20 is mainly performed by adjusting the diameters of the pressure adjusting passage 12 and the small hole 9a.

  In the second embodiment, the number of return oil passages is increased from three to four, and if one of the suction ports is below the oil level of the lubricating oil A in which it stays, excessive lubricating oil in the valve operating chamber 20 It is possible to prevent A from staying, and work can be performed in various work postures as compared to the work posture shown in the first embodiment.

  However, if the number of return oil passages is increased from three to four, even if one of the suction ports of the four return oil passages 27, 28, 52, 53 is below the surface of the lubricating oil A, it is easy as it is. In addition, the lubricating oil A cannot be discharged from the valve operating chamber 20. This is because the amount of air sucked from the suction ports of the remaining three return oil passages increases, and the suction capacity of the return oil passages of the suction ports below the oil level decreases.

  Therefore, in order to increase the suction ability of the lubricating oil A, a reservoir (not shown) for storing the lubricating oil A may be provided in the four return oil passages 27, 28, 52, 53 or the return oil passages 30 ′, 40. Lubricating oil A having a high viscosity adheres to the inner surface of each return oil passage, the sectional area of the return oil passage is substantially narrowed, and the suction pressure of each return oil passage is increased. When the suction port of the return oil passage is not below the oil level, the lubricating oil A that has accumulated in the reservoir due to gravity flows backward to the return oil passage or moves to the reservoir and accumulates in the reservoir. The cross-sectional area of the return oil passage can be made substantially smaller. As a result, the pressure balance is established between the four return oil passages 27, 28, 52, 53, and one of the suction ports of the four return oil passages 27, 28, 52, 53 is the oil level of the lubricating oil A. If it is below, the lubricating oil A can be discharged from the valve operating chamber 20.

[Third embodiment]
Next, a third embodiment of the 4-cycle engine of the present invention will be described. In the third embodiment, only differences from the second embodiment described above will be described, and the same reference numerals will be given to the same aspects as in the second embodiment, and description thereof will be omitted.

  In the valve operating chamber 20 of the four-cycle engine 1, FIG. 11 (a) (sectional view), FIG. 11 (b) (plan view), FIG. 12 (a) (partial side view), FIG. As shown in a plan view corresponding to XI-XI in FIG. 11 (a), six return oil passages 27, 28, 29, 52, 53, and 54 are provided. The return oil passage 29 is provided on the opposite side to the shaft coupling portion side and in the vicinity of the center in the width direction where the rocker arm 37 is arranged in parallel, and the return oil passage 54 is near the end portion on the shaft coupling portion side and has a width. Near the center of the direction. The return oil passages 27, 28, and 29 extend to a position near the upper surface of the cylinder block 3 serving as a bottom surface, communicate with a return oil passage 32 formed between the lid member 25 and the top plate portion 23, and return oil passage 32. Have joined together to become one. The return oil passages 52, 53, and 54 are opened near the top plate portion 23 on the upper surface, communicate with a return oil passage 33 formed between the lid member 25 and the top plate portion 23, and the return oil passage 33. Have joined together to become one.

  The return oil passage 32 and the return oil passage 33 are connected to the switching device 70, and the switching device 70 is connected to the return oil passage 40. As shown in FIG. 12C (cross-sectional view), the switching device 70 has a weight 71 movably provided in the switching device 70, and can be moved by gravity according to the work posture of the four-cycle engine 1. . In a posture in which the upper surface of the weight 71 is higher than the bottom surface of the valve operating chamber 20, the weight 71 moves to communicate the three return oil passages 27, 28, 29 and the return oil passage 40, thereby operating the valve operating chamber. In a posture in which the upper surface is below the bottom surface of the weight 20, the weight 71 moves, and the three suction ports 52, 53, and 54 communicate with the return oil passage 40.

  As described above, the six return oil passages 27, 28, 29, 52, 53, and 54 in the third embodiment are provided. However, when the switching device 70 operates, the six return oil passages 27 and 28 are provided. , 29, 52, 53, 54 are automatically closed. For this reason, if the pressure of the valve operating chamber 20 and the inflow amount of the lubricating oil A are set as in the first embodiment, there is no need to provide a reservoir as in the second embodiment.

  In the present embodiment, when at least one of the suction ports of the six return oil passages 27, 28, 29, 52, 53, 54 is below the level of the lubricating oil A that has accumulated, the lubricating oil A is transferred to the valve operating chamber 20. It is possible to prevent excessive retention. Further, since at least one of the six return oil passages 27, 28, 29, 52, 53, 54 is always located below the breather port 24, the liquefied lubricating oil A is hardly released from the breather port 24. Therefore, it is possible to prevent the consumption of the lubricating oil A from increasing, and it is possible to work in any working posture.

[Fourth embodiment]
Next, a fourth embodiment of the four-cycle engine of the present invention will be described. In the fourth embodiment, only differences from the first embodiment described above will be described, and the same reference numerals will be given to the same aspects as those in the first embodiment, and the description thereof will be omitted.

  As shown in FIG. 13A (cross-sectional view) and FIG. 13B (plan view), the valve chamber of the 4-cycle engine 1 includes a switching component 77 in each of the three suction pipes 73, 74, 75. Is inserted. The suction pipe 73 and the suction pipe 74 are provided on the side of the shaft connecting portion, the suction pipe 73 is provided in the vicinity of one end side in the width direction where the rocker arm 37 is arranged in parallel, and the suction pipe 74 is provided in the vicinity of the other end side in the width direction. Is provided. Further, the suction pipe 75 is provided on the side opposite to the shaft coupling portion side and in the vicinity of the center in the width direction. The suction pipes 73, 74, and 75 extend in the vertical direction, and both end portions thereof extend to positions near the bottom surface and the top surface of the valve operating chamber 20. Each suction pipe 73, 74, 75 communicates with a corresponding return oil passage 78, 79, 80 formed in the side plate portion 22 of the housing 21. Each return oil passage 78, 79, 80 is connected to a four-pronged connection passage 81, and the connection passage 81 is connected to the return oil passage 40.

  A switching part 77 is inserted in each of the suction pipes 73, 74, 75. The switching component 77 has a rod-shaped stem 77a and heads 77b provided at both ends thereof. The stem 77a is sufficiently smaller than the inner diameters of the suction pipes 73, 74, 75, and the head 77b has the suction pipe 73, It is formed in a size that can close the openings at both ends of 74 and 75. That is, the switching component 77 moves in the suction pipes 73, 74, and 75, thereby closing one of the openings at both ends of the suction pipe. This switching component 77 moves by gravity according to the working posture of the four-cycle engine 1. When the switching component 77 is in a posture in which the top surface is above the bottom surface of the valve operating chamber 20, the switching component 77 moves to open the bottom side opening of each of the suction pipes 73, 74, 75 to open each suction pipe 73. , 74, 75 and the return oil passage 40 are communicated, and in a posture where the upper surface is below the bottom surface of the valve operating chamber 20, the switching component 77 moves and each of the suction pipes 73, 74, 75 opens on the upper surface side. Is opened, and the suction pipes 73, 74, 75 and the return oil passage 40 are communicated with each other.

  In this embodiment, three suction pipes 73, 74, 75 are prepared and six openings are provided, but three of the openings are automatically closed by the operation of the switching component 77. For this reason, if the pressure of the valve operating chamber 20 and the inflow amount of the lubricating oil A are set as in the first embodiment, there is no need to provide a reservoir as in the second embodiment.

  Further, in the present embodiment, when at least one of the six openings is below the level of the lubricating oil A that has accumulated, the lubricating oil A can be prevented from remaining excessively in the valve operating chamber 20. In addition, since at least one of the six openings is always located below the breather port 24, it is difficult for the liquefied lubricating oil A to be released from the breather port 24, thereby preventing an increase in consumption of the lubricating oil A. It is possible to work in any working posture.

  Thus, in these embodiments described above, the valve operating chamber 20 and the oil reservoir 7 communicate with each other via the return oil passage 40, and the lubricating oil A from the valve operating chamber 20 to the oil reservoir 7 is directly returned. Therefore, compared with the case where the lubricating oil A is returned from the valve operating chamber 20 to the crank chamber 5a, the deterioration of the lubricating oil can be suppressed, and the pressure adjustment between the valve operating chamber 20 and the oil reservoir chamber 7 is easy. The blow-by gas can be easily discharged from the lubrication system via the breather passage 42.

The lubrication state explanatory drawing of the 4-cycle engine concerning the 1st Embodiment of this invention is shown. 1 shows a cross-sectional view of a four-cycle engine of the present invention. The valve chamber of a 4-cycle engine is shown, the figure (a) is sectional drawing of a valve chamber, and the figure (b) is a top view of a valve chamber. The top view of the valve operating chamber equivalent to the III-III arrow of Fig.3 (a) is shown. The side view of the brush cutter which mounts the 4-cycle engine of this invention is shown. The side view of the working posture which a brush cutter assumes is shown. The side view of the working posture which a brush cutter assumes is shown. It is sectional drawing showing the retention state of the lubricating oil in the valve operating chamber corresponding to the working attitude | position of a brush cutter. It is sectional drawing showing the retention state of the lubricating oil in the valve operating chamber corresponding to the working attitude | position of a brush cutter. The valve operating chamber of the 4-cycle engine concerning the 2nd Embodiment of this invention is shown, The figure (a) is sectional drawing of a valve operating chamber, The figure (b) is a top view of a valve operating chamber. . The valve operating chamber of the 4-cycle engine concerning the 3rd Embodiment of this invention is shown, The figure (a) is sectional drawing of a valve operating chamber, The figure (b) is a top view of a valve operating chamber. . The valve operating chamber of the 4-cycle engine concerning 3rd Embodiment is shown, The figure (a) is a side view of a valve operating chamber, The figure (b) is a XI-XI arrow view of Fig.11 (a). It is a top view of a corresponding valve operating chamber, and the figure (c) is a sectional view of a switching device. The valve operating chamber of the 4-cycle engine concerning the 4th Embodiment of this invention is shown, The figure (a) is a cross-sectional surface of a valve operating chamber, The figure (b) is a top view of a valve operating chamber. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Portable 4 cycle engine 5a Crank chamber 7 Oil reservoir chamber 9 Oil supply passage 9a Small hole 10,13 One-way valve 15 Crankshaft (drive parts)
18 Connecting shaft 20 Valve chamber 20a Intake valve (drive component)
20b Exhaust valve (drive parts)
27, 28, 29, 52, 53, 54 Return oil passage 35 Valve drive gear (drive parts)
36 Cam gear (drive parts)
37 Rocker arm (drive parts)
42 Breather passage 50 Air cleaner 60 Brush cutter 70 Switching device (oil path switching valve)
77 Switching parts (oil path switching valve)
A Lubricating oil

Claims (9)

Lubricating oil stored in an oil sump chamber disposed in the vicinity of the crank chamber is sent to driving parts accommodated in the crank chamber and the valve operating chamber using the pressure fluctuation of the crank chamber, and is lubricated and circulated. A portable four-cycle engine comprising a breather passage communicating the valve operating chamber and an air cleaner, and sending blow-by gas from the valve operating chamber to the breather passage and sending the air cleaner to the air cleaner.
Provided in the valve chamber a plurality of three or more return oil passages for circulating the lubricating oil sent to the valve chamber,
These return oil passages merge into one oil passage outside the valve chamber,
An opening communicating with the valve operating chamber in the breather passage is provided near the center of the valve operating chamber, and in a posture in which the portable four-cycle engine is used, a plurality of return oil passages are provided below the openings. A portable four-cycle engine, wherein at least one of the suction ports is located.   The portable four-cycle engine according to claim 1, wherein the return oil passage is connected to the oil reservoir chamber. A one-way valve is provided in the middle of the circulation path of the lubricating oil, and the oil reservoir chamber always tends to be a negative pressure from the valve chamber and the atmospheric pressure while the portable four-cycle engine is driven,
A small hole is provided in an oil supply passage for lubricating oil that communicates between the oil reservoir chamber and the crank chamber, and the small hole is used for lubrication stored in the oil reservoir chamber in a posture in which the portable four-cycle engine is used. It is located on the oil surface of the oil, it is possible to adjust the amount of lubricating oil flowing into the valve operating chamber by adjusting the size of the small hole,
The pressure in the valve operating chamber becomes equal to or slightly positive from the atmospheric pressure by adjusting the inner diameter of the return oil passage in a range in which the return oil passage is not clogged with dust or the like. The portable four-cycle engine as described.   The inlets of the plurality of return oil passages are in the valve operating chamber on the side of the shaft connecting portion that rotatably connects and supports a rotating shaft that rotates in response to power from the crankshaft in the crank chamber. 4. The portable four-cycle engine according to claim 3, wherein the portable four-cycle engine is provided on both ends in the width direction and on the side opposite to the shaft coupling portion side in the valve operating chamber.   The suction port of the return oil path provided on the opposite side of the valve coupling chamber from the shaft coupling portion side is provided near the center in the width direction of the valve chamber. Portable 4-cycle engine.   The portable four-cycle engine according to claim 4 or 5, wherein a suction port of a return oil passage provided in the valve operating chamber is provided near a bottom surface in the valve operating chamber.   Depending on the posture in which the portable four-cycle engine is used, a suction port located on the lower side in the vertical direction among the suction ports of the plurality of return oil passages communicates with the oil reservoir chamber, and is located on the upper side in the vertical direction. The portable four-stroke cycle engine according to any one of claims 2 to 6, further comprising an oil passage switching valve that places a suction port positioned in a state of non-communication with the oil reservoir.   A work machine equipped with the portable four-cycle engine according to any one of claims 1 to 7.   The working machine according to claim 8, wherein the working machine is a brush cutter.

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