JP2004251231A - Lubricating device for four cycle engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating device for a four cycle engine capable of feeding oil and lubricating by utilizing change of pressure in a crankcase effectively without increasing its size, complicating its structure, and increasing machining cost. <P>SOLUTION: In this lubricating device for the four cycle engine, oil is fed into the crankcase 4 and a valve gear chamber 11 storing each valve mechanism for suction/exhaust from an oil sump chamber 6 provided in the vicinity of the crankcase 4 supporting a crankshaft 7 to lubricate each part. Only an oil feeding passage 13 communicating the oil sump chamber 6 with the inside of the crankcase 4 is provided to supply oil. The oil feeding passage 13 is opened when the inside of the crankcase 4 has negative pressure to pump up oil from the oil sump chamber 6 in order to feed oil into the crankcase 4. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lubricating device for a four-stroke engine, and more particularly, to a lubricating device for a small four-stroke engine used in a portable brush cutter, a backpack type power sprayer, etc., in which the inclined position is one of the working positions. About.
[0002]
[Prior art]
2. Description of the Related Art In general, an engine that is a driving source of a working machine that is carried or carried by a worker himself, such as a portable brush cutter (trimmer) or a backpack type power sprayer for plants, tilts the working machine. It is required to operate stably even in the event of a failure. In a two-stroke engine, which is a type of engine, for example, a reed valve-type engine uses a negative pressure generated when a piston rises to suck a fuel mixture of fuel and lubricating oil into the engine. However, since a mechanism for lubricating each movable portion is provided, a structure that can be used at any angle can be easily realized. As in this example, a two-stroke engine is widely used in the portable work machine. On the other hand, a four-stroke engine, which is another type of engine, can be manufactured small and light due to advances in design and processing techniques, but in most cases, the oil sump (oil pan), which is a component of the lubricating device, has a crankshaft. Since a structure is provided at the lower part of the chamber and lubricates each movable part by jumping up or pumping up oil from the position, it is basically used in an upright state. In other words, the degree of freedom in inclined operation was inferior to that of the two-cycle engine.
However, the two-cycle engine has problems such as a large amount of hydrocarbons in the exhaust gas and a large noise.
In recent years, there has been an increasing demand for purification of exhaust gas and prevention of deterioration of the working environment, and it has become impossible for a two-stroke engine to meet the demand. Therefore, the establishment of a technique for increasing the degree of freedom in tilting operation has been awaited so that a four-stroke engine having good exhaust gas characteristics and low noise can be used for a portable work machine.
Therefore, the present applicant has previously proposed a lubricating device for a four-stroke engine utilizing the fact that the pressure in the crank chamber changes according to the elevating operation of the piston (for example, Patent Document 1).
In this proposal, after completely shutting off the oil chamber and the crank chamber, the crank chamber and the oil chamber are communicated from the oil chamber to a part of the rotation trajectory of the crankshaft so that the negative pressure of the crank chamber is reduced. The oil supply means is provided with an intermittent oil supply means for sucking oil from the oil reservoir and feeding the oil into the crank chamber, and the oil supply means has a passage for communicating the crank chamber with the oil reservoir when the pressure in the crank chamber becomes negative. Is provided inside the crankshaft.
[0003]
[Patent Document 1]
JP-A-10-288019 (paragraph "0023", FIG. 1)
[0004]
[Problems to be solved by the invention]
The configuration disclosed in Patent Literature 1 has an advantage that lubrication in the crank chamber and the valve operating chamber can be performed only by using the pressure change in the crank chamber, but there is a possibility that the device structure becomes relatively large.
That is, there is a passage formed inside the crankshaft as one of the communication passages between the crank chamber and the oil reservoir. For this reason, as a size of the crankshaft, a dimension for securing a passage is required in addition to a dimension for securing strength, and as a result, the diameter of the crankshaft must be increased. In addition, a passage shape is required that bends radially in the middle of the crankshaft instead of penetrating in the axial direction, and that the accuracy of alignment between the passages needs to be increased, which may lead to an increase in machining cost. There is also.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to reduce the pressure change in the crank chamber without increasing the size, complicating the structure, and increasing the machining cost in view of the above-described problems in the conventional four-stroke engine, particularly a small lubricating device for a four-stroke engine. It is an object of the present invention to provide a lubricating device for a four-stroke engine that can perform oil feeding lubrication by utilizing the lubrication.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided an oil reservoir (6) provided near a crank chamber (4) which supports a crank shaft (7). In a lubricating device for a four-stroke engine in which oil is supplied to a valve operating chamber (11) in which the oil is stored and the oil is circulated, the oil storage chamber (6) and the crank chamber ( 4) Only an oil supply passage (13) that can communicate with the inside is provided, and the oil supply passage (13) opens when the pressure in the crank chamber (4) becomes negative, and the oil reservoir (13) opens. It is characterized in that the oil is pumped into the crank chamber (4) by pumping up the oil from (6).
[0007]
According to a second aspect of the present invention, in the lubricating device for a four-stroke engine according to the first aspect, the opening (13A) on the crank chamber side in the oil supply passage (13) is provided with a piston (8) in the crank chamber (4). ) Is provided at a position where the opening area can be fully opened or gradually increased from the position near the top dead center to the top dead center.
[0008]
According to a third aspect of the present invention, in the lubricating device for a four-stroke engine according to the first or second aspect, the opening (13A) of the oil supply passage (13) on the crank chamber (4) side is at a top dead center position. The skirt portion (8A) of the piston (8) is positioned on the lower dead center direction side.
[0009]
According to a fourth aspect of the present invention, in the lubricating device for a four-stroke engine according to any one of the first to third aspects, the oil supply passage (13) has a negative pressure in the crank chamber (4). A check valve (19) having a function of opening when the valve is opened.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram for explaining a lubrication route of a four-cycle engine using a lubrication device according to an embodiment of the present invention. In particular, FIG. 1 shows a case where the piston is located at the top dead center.
[0011]
As shown in FIG. 1, a four-cycle engine 1 includes a crankcase 5 including a cylinder block 3 in which a cylinder head 2 is integrated and a crankcase 4, and an oil sump provided near the crankcase 4. A room 6 is provided.
The oil reservoir 6 is partitioned from the crankcase 4 to form a closed space as a whole.
[0012]
In FIG. 1, a suction section 30 described later is provided in the oil reservoir 6, and a one-way valve 40 is provided in the crankcase 4. The one-way valve 40 responds to a change in pressure in the crank chamber 5. The oil reservoir 6 can be opened and closed and closed when there is no pressure change, so that no oil leaks to the outside even if the oil reservoir 6 is in any inclined state.
[0013]
As shown in FIG. 1, a crankshaft 7 is rotatably supported by the cylinder block 3 and the crankcase 4. The piston 8 connected to the crankpin of the crankshaft 7 via a connecting rod is slidably fitted in a cylinder 3A provided inside the cylinder block 3.
[0014]
In FIG. 1, an intake port and an exhaust port communicating with a carburetor (not shown) and an exhaust muffler (not shown) are formed on the upper wall of the cylinder 3A, and each of these ports has an intake valve for opening and closing the port. And an exhaust valve (in FIG. 1, only one valve is indicated by a symbol V for convenience).
As shown in FIG. 1, the valve drive unit 10 that drives these valves is configured by components such as a valve drive gear 10A, a cam gear 10B, and a rocker arm (not shown).
Among the components of the valve drive unit 10, the valve drive gear 10 </ b> A and the cam gear 10 </ b> B are connected to the cylinder block 3 so that the valve chamber 11 formed at the head of the cylinder block 3 communicates with the crank chamber 4. It is arranged in a communication passage 12 formed on the side of the crankcase 5.
[0015]
Between the cylinder block 3 and the oil reservoir 6, an oil feeding means constituted by the suction portion 30 and the oil feeding passage 13 is provided.
In FIG. 1, the suction portion 30 is composed of a tube 30A that can be easily bent by an elastic material such as rubber, and a weight 30B with a suction port provided at the tip thereof. In other words, the weight 30B can always move vertically downward due to its gravity, so that even if the oil reservoir 6 is inclined, the tip of the weight 30B sinks below the oil level of the oil. You can make it.
[0016]
The oil feed passage 13 having one opening located in the suction portion 30 is located at the position of the other opening 13 </ b> A, and the oil reservoir chamber 6 and the crankcase 4 when the pressure in the crank chamber 4 is reduced in the cylinder block 3. A position communicating with the inside of the room 4 is set.
The other opening 13 </ b> A in the oil feed passage 13 connects the inside of the crank chamber 4 with the oil storage chamber 6 when the inside of the crank chamber 4 tends to be negative pressure due to the rise of the piston 8, and Is a portion that can be pumped up and introduced into the crank chamber 4. For this reason, the position of the opening 13A is a position where the piston 8 is fully opened when the piston 8 reaches the vicinity of the top dead center, and the lower skirt portion 8A of the lower part of the piston 8 located near the top dead center is located on the bottom dead center direction side (see FIG. 1, the right side). Therefore, the opening 13A is fully opened when the piston 8 reaches the vicinity of the top dead center, and this state is maintained until the piston 8 reaches the top dead center.
[0017]
The opening 13A is provided not only at a position where the piston 8 can be fully opened in the vicinity of the top dead center, but also gradually opened until the piston 8 reaches the vicinity of the top dead center and reaches the top dead center. It can be provided at a position where the area can be increased. That is, when the piston 8 reaches the vicinity of the top dead center, the opening 13A starts to open, gradually increases the opening area until reaching the top dead center, and becomes fully open when the top dead center is reached. Position.
On the other hand, an opening 14A having substantially the same shape as the opening 13A is opened on the side of the cylinder block 3 facing the opening 13A, and the opening 14A and the oil reservoir 6 are connected by the mist passage 14. Are in communication.
An opening portion 14B of the mist passage 14 in the oil reservoir 6 is opened at a substantially central portion of the oil reservoir 6, and the oil mist is mainly sucked from the opening portion 14B. In FIG. 1, reference numeral 20 denotes a check valve similar to the check valve 19.
[0018]
The above-described one-way valve 40 is provided between the crank chamber 4 and the communication passage 12, and the pressure in the crank chamber 4 is reduced to a negative pressure by the rise of the piston 8 and the valve hole formed in the lower part of the crank case 4. It consists of a valve plate 40A that closes the valve hole when it becomes.
[0019]
On the other hand, in FIG. 1, a breather pipe 15 is provided at an upper portion of the cylinder block 3, and one end of the breather pipe 15 is connected and opened in the valve operating chamber 11, and the other end is connected to the air cleaner 16. ing.
A return oil passage 17 is provided in the valve operating chamber 11, and one end of the return oil passage 17 is open to the valve operating chamber 11 and the other end is disposed in the oil reservoir 6.
The other end of the return oil passage 17 located in the oil reservoir 6 is positioned at a substantially central position in the thickness dimension S of the oil reservoir 6. In the oil reservoir 6, the amount of oil contained is defined so that the other end of the return oil passage 17 is always positioned above the oil level. Thus, even when the oil reservoir 6 is inclined or turned over, the other end of the return oil passage 17 is opened above the oil level so that the oil can be recirculated.
The same applies to the opening portion 14B of the mist passage 14 described above. The air cleaner 16 is also provided with a return oil passage 18 for recirculating the oil gas-liquid separated by the oil separator 16A to the oil reservoir 6.
[0020]
Since the present embodiment is configured as described above, the valve chamber 11 of the engine 1 is positioned upward, that is, in a so-called upright state, when the piston 8 is not in the elevating operation, the crank chamber 4 An appropriate amount of lubricating oil is stored in the oil reservoir 6 and the valve chamber 11. When the engine 1 changes from the upright state to the inverted or inclined state, the weight 30B of the oil supply unit 30 can move to the position where the oil is stored in the oil storage chamber 6, so that the position of the weight 30B in the oil is always maintained. To keep the oil ready for pumping. Further, since the amount of oil in the oil reservoir 6 is such that the opening of the return oil passage 17 always projects from the oil level, the oil recirculation passage can be maintained even in the non-erected state. A state in which the oil can be returned from the valve operating chamber 11 to the oil reservoir 6 without being immersed in the oil is maintained. As a result, it is possible to prevent a situation in which the amount of oil circulating in other portions is insufficient due to an excessive amount of oil in the valve operating chamber 11.
[0021]
When the engine 1 is started, a pressure change occurs in the crank chamber 4 due to the raising and lowering operation of the piston 8, and when the piston 8 rises, the crank chamber 4 is depressurized and tends to have a negative pressure. Pressure tendency.
[0022]
When the pressure in the crank chamber 4 becomes negative, a pressure difference is generated between the crank chamber 4 and the oil reservoir 6, and the opening 13A of the oil feed passage 13 starts to open as the piston 8 moves near the top dead center. , Is fully opened when the piston 8 moves to the vicinity of the top dead center. As a result, the negative pressure in the crank chamber 4 acts on the oil supply passage 13 so that oil is sucked from the oil reservoir 6 and sent toward the crank chamber 4. Since the inside of the oil supply passage 13 is fully opened until the piston 8 moves from the vicinity of the top dead center to the top dead center position, the negative pressure in the crank chamber 4 is sufficiently applied, and the oil supply is performed. The quantity can be sufficient.
[0023]
The oil sent into the crank chamber 4 is pulverized by the piston 8, the crankshaft 7 and the like to become an oil mist.
[0024]
In FIG. 1, when the piston 8 descends, the pressure in the crank chamber 4 becomes positive, and a differential pressure is generated between the crank chamber 4 and the oil reservoir 6.
In this case, the valve plate 40A of the one-way valve 40 opens the valve hole, and sends the oil mist stored in the crank chamber 4 and the cylinder 3A together with the pressurized air from the crank chamber 4 to the communication path 12.
The oil mist sent to the communication passage 12 is pressure-fed to the valve operating chamber 11 by positive pressure, and lubricates each part of the valve drive unit 10 on the way.
The oil mist that has lubricated the components of the valve drive unit 10 reaches the valve operating chamber 11, where the air in the oil storage chamber 6 is sucked in from the passage 14, and the oil in the oil storage chamber 6 is suctioned by the oil supply unit 30. As a result, the pressure in the oil reservoir 6 becomes negative, and the oil is recovered to the oil reservoir 6 through the return passage 17.
Further, a part of the oil mist and the blow-by gas in the valve operating chamber 11 is opened into the air cleaner 16 through the breather pipe 15 to be separated into oil and blow-by gas. To be collected.
[0025]
In the present embodiment, a check valve 19 is provided in the oil feed passage 13 provided between the crank chamber 4 and the oil reservoir 6.
The check valve 19 has a habit of being opened when the pressure in the crank chamber 4 is reduced to a negative pressure and allowing oil to flow from the oil reservoir 6, and when the pressure in the crank chamber 4 becomes a positive pressure. Is closed to prevent backflow from the inside of the crank chamber 4 and to enable a smooth supply of oil.
The thin tube 21 is a small-diameter passage that connects the bottom of the crankcase 4 and the case 22 of the valve drive unit 10. The small tube 21 discharges residual oil in the crankcase 4 to the case 22 when the engine stops rotating. It is a passage.
[0026]
In the present embodiment, as a configuration for lubricating the inside of the crank chamber 4, the oil flow path using the negative pressure in the crank chamber 4 is fully opened or gradually opened by moving the piston 8 near the top dead center of the piston 8. Since the opening having the enlarged configuration is merely connected to the crankcase, the processing becomes extremely easy unlike the case where the oil supply means in the crankcase is provided on the crankshaft.
FIG. 2 shows a configuration disclosed in Japanese Patent Application Laid-Open No. 2002-276321, which is a prior application of the present applicant. In this configuration, an oil discharge portion (for convenience, In FIG. 2, reference numeral 13A ') is provided (in the same publication, paragraph "0029"), but as a flow path leading to the oil discharge portion 13A', the return oil from the valve operating chamber 11 and the oil storage chamber ( For the sake of convenience, the flow path of the oil (indicated by reference numeral 6 in FIG. 1) is combined with the oil flow path, so that the piping path may be complicated. On the other hand, in the present embodiment, a single flow path from the oil reservoir 6 to the crank chamber 4 suffices, so that the configuration and processing are extremely simple.
[0027]
【The invention's effect】
According to the first aspect of the present invention, as a configuration for lubricating the crankcase, only an oil supply passage that can pump up oil from the oil reservoir when the pressure in the crankcase becomes negative is provided. There is no need to create a passage into the crankshaft. As a result, it is possible to obtain a lubricating device that has a simple lubricating structure, prevents an increase in the size and complexity of the device, and can reduce an increase in cost.
[0028]
According to the second and third aspects of the present invention, the oil supply passage having a structure in which the opening area is gradually changed from the vicinity of the top dead center of the piston to the top dead center or from the vicinity of the top dead center to the top dead center is provided. Therefore, a maximum amount of lubrication can be secured when the negative pressure in the crank chamber is at a maximum.
[0029]
According to the fourth aspect of the present invention, since the oil feed passage is provided with the check valve which is opened only when the pressure in the crank chamber becomes negative, the oil can be smoothly supplied.
[Brief description of the drawings]
FIG.
FIG. 3 is a schematic diagram showing a state in which a piston is at a top dead center in order to explain a lubrication path in a four-stroke engine to which a lubrication device according to an embodiment of the present invention is applied.
FIG. 2
FIG. 2 is a schematic diagram showing a lubrication path in a four-cycle engine for explaining a difference in operation from the embodiment shown in FIG. 1.
[Explanation of symbols]
Reference Signs List 1 engine 4 crank chamber 6 oil reservoir 8 piston 11 valve operating chamber 13 oil feed passage 13A opening 19 check valve

Claims (4)

A valve operating chamber (11) accommodating the crank chamber (4) and intake and exhaust valve mechanisms from an oil sump chamber (6) provided near a crank chamber (4) that supports the crank shaft (7). ), Lubricating each part and circulating the oil
In order to supply oil, only an oil supply passage (13) capable of communicating between the oil reservoir (6) and the crank chamber (4) is provided, and the oil supply passage (13) is provided in the crank chamber (4). The lubrication of a four-stroke engine is characterized in that the lubrication system is configured to open when a negative pressure is applied to the inside and to pump oil from the oil reservoir (6) to feed the oil into the crank chamber (4). apparatus. The lubricating device for a four-stroke engine according to claim 1,
The opening (13A) on the crank chamber side in the oil supply passage (13) is fully opened or gradually opened from the position near the top dead center to the top dead center of the piston (8) in the crank chamber (4). A lubricating device for a four-stroke engine, wherein the lubricating device is provided at a position where the opening area can be increased. The lubricating device for a four-stroke engine according to claim 1 or 2,
The opening (13A) of the oil supply passage (13) on the side of the crank chamber (4) is positioned on the lower dead center direction side of the skirt (8A) of the piston (8) at the top dead center. Characteristic lubrication system for 4-cycle engine. The lubricating device for a four-stroke engine according to any one of claims 1 to 3,
A lubrication system for a four-stroke engine, characterized in that a check valve (19) having a function of opening when a negative pressure is generated in the crank chamber (4) is arranged in the oil supply passage (13). apparatus.

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