JP2016070073A - Oil pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil pump which is simply constructed to pressure-feed oil.SOLUTION: An oil pump is provided for an engine 1 which includes a cam shaft 40 provided in a crank case 20, and a tappet 60 for reciprocating following a cam 43 to transmit driving force to a dynamic valve. The oil pump includes a piston 70 provided on the tappet, a cylinder 24 into which the piston is inserted, suction oil paths 25, 26 for introducing oil into the cylinder, discharge oil paths 27, 28 for discharging the oil from the cylinder, and a rotary valve having a valve element 44 to be rotated in association with the rotation of the cam shaft, for communicating the suction oil paths with each other and shutting the discharge oil paths off from each other when the piston is moved in the direction of being pulled out of the cylinder and for shutting the supply oil paths off from each other and communicating the discharge oil paths with each other when the piston is moved in the direction of being pushed into the cylinder.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an oil pump that pumps oil to a location where lubrication is necessary in an engine, and more particularly to a pump that can pump oil with a simple structure.

Conventionally, the lubrication of general-purpose engines mounted as drive power sources in various equipment such as industrial equipment, generators, gardening equipment, etc. has been conventionally performed by splash lubrication in which the oil stored in the lower part of the crankcase is scraped. It was.
However, since such splash lubrication generates a large amount of oil mist, the structure of the breather that separates and discharges the blow-by gas by gas-liquid separation tends to be complicated.
In addition, a part of the oil mist is discharged together with the blow-by gas to increase the amount of oil consumption, and the property of the exhaust gas is deteriorated by burning the oil.

In order to cope with such a problem, even in a general-purpose engine, there is a demand for forced lubrication in which oil is pumped by an oil pump to necessary portions such as an oil jet and each sliding portion on the back side of the piston.
By adopting forced lubrication in a general-purpose engine and optimally supplying oil to each part, it is possible to suppress excessive generation of oil droplets and simplify the breather system.
On the other hand, since a general-purpose engine is strongly required to be low in cost and simplified in structure, it is demanded to enable forced lubrication with a simple structure as much as possible.

  As conventional techniques related to the simplification of an oil pump for an engine, for example, Patent Documents 1 and 2 disclose that oil is sucked and discharged by using a reciprocating motion of a tappet that drives an intake and exhaust valve of an automobile engine, and an oil passage. Describes an oil pump provided with a check valve to prevent backflow of oil.

Japanese Utility Model Publication No. 2-31313 Japanese Utility Model Publication 2-31314

As in the techniques described in Patent Documents 1 and 2, when a check valve is provided to prevent the backflow of oil, the number of parts such as the valve body and the urging means is increased, making manufacturing and assembly complicated. Therefore, since the cost and weight also increase, it is difficult to apply to a general-purpose engine with severe restrictions on cost and the like.
In view of the above-described problems, an object of the present invention is to provide an oil pump capable of pumping oil with a simple structure.

The present invention solves the above-described problems by the following means.
The invention according to claim 1 includes a camshaft provided on a crankcase and having a cam for driving a valve, and a tappet that reciprocates following the cam surface of the cam and transmits a driving force to the valve. An oil pump provided in an engine, wherein a piston provided in the tappet, a cylinder into which the piston is inserted, a suction oil passage for introducing oil into the cylinder, and a discharge oil for discharging the oil from the cylinder And a valve body that rotates in conjunction with rotation of the camshaft, and when the piston moves in a direction of being pulled out of the cylinder, the suction oil passage is communicated and the discharge oil passage is shut off, An oil comprising a rotary valve that shuts off the supply oil passage and communicates the discharge oil passage when the piston moves in a direction to be pushed into the cylinder. It is a pump.
According to this, by forming a cylinder into which the piston provided in the tappet is inserted, the communication between the supply oil path to the cylinder and the discharge oil path from the cylinder is switched by the rotary valve interlocked with the camshaft. Thus, an oil pump capable of pumping oil can be configured with a simple configuration.

The invention according to claim 2 is characterized in that the cylinder is formed in a cylindrical shape having an opening into which an outer peripheral surface portion of the tappet is inserted in a central portion by a resin material having a specific gravity lighter than a material constituting the tappet. The oil pump according to claim 1.
According to this, by attaching the piston, which is a separate resin part, to the tappet, it is possible to reduce the weight of the valve drive system part, improve the followability, and prevent the occurrence of valve surging and the like.
In addition, among the intake and exhaust tappets, the intake and exhaust side tappet parts can be shared by attaching a separate piston to only the tappet on the side where the cylinder is provided (the side used as an oil pump). Can do.

The invention according to claim 3 is characterized in that the piston is elastically deformed in a direction in which an axial dimension is compressed in accordance with an increase in hydraulic pressure in the cylinder. It is.
According to this, the piston is elastically deformed by the input received from the oil, thereby preventing the hydraulic pressure in the cylinder from changing suddenly, suppressing the pulsation of the discharge pressure and improving the durability of the oil pump. it can.

  As described above, according to the present invention, an oil pump capable of pumping oil with a simple structure can be provided.

It is a figure which shows the structure of the oil pump periphery in the general purpose engine which has Example 1 of the oil pump to which this invention is applied. It is a figure which shows operation | movement of the oil pump of FIG. It is a schematic diagram which shows the structure of the piston in Example 2 of the oil pump to which this invention is applied.

  The present invention has the object of providing an oil pump capable of pumping oil with a simple structure. A piston is provided on a tappet which is provided in a crankcase and reciprocates according to the rotation of the camshaft, and is formed on a part of the camshaft. The problem was solved by switching between communication and shutoff of the supply oil passage and the discharge oil passage by the rotary valve.

Embodiments of an oil pump to which the present invention is applied will be described below.
The oil pump according to the embodiment is, for example, provided in an OHV general-purpose engine that drives an intake / exhaust valve provided in a cylinder head by a camshaft housed in a crankcase and driven by a crankshaft.
FIG. 1 is a diagram illustrating a configuration around an oil pump in a general-purpose engine having an oil pump according to a first embodiment, and is a cross-sectional view taken along a plane including a camshaft and a central axis of a tappet.

  The engine 1 includes a cylinder 10, a crankcase 20, a bearing cover 30, a camshaft 40, an intake side tappet 50, an exhaust side tappet 60, a piston 70, and the like.

The cylinder 10 protrudes from the crankcase 20 and is a portion where a cylinder bore having a cylindrical inner surface into which a piston (not shown) is inserted is formed.
A plurality of cooling fins 11 are formed on the outer peripheral surface of the cylinder 10.
The cylinder 10 is formed with a bolt hole 12 used for fastening a cylinder head (not shown).
The cylinder head is attached to the end of the cylinder 10 opposite to the crankcase 20, and includes a combustion chamber, a spark plug, an intake port, an exhaust port, an intake valve that opens and closes each port at a predetermined valve timing, and an exhaust. It has a valve.

The crankcase 20 is a case-like portion in which a crankshaft (not shown) that is an output shaft of the engine 1 is accommodated.
The cylinder 10 and the crankcase 20 are integrally formed, for example, by casting an aluminum-based alloy, and then manufactured by machining a necessary portion.
One end of the crankcase 20 in the crankshaft direction (the right end in FIG. 1) is open and is closed by the bearing cover 30.

The crankcase 20 includes a camshaft holding portion 21, an intake side tappet holding portion 22, an exhaust side tappet holding portion 23, a cylinder portion 24, oil passages 25 to 28, and the like.
The camshaft holding portion 21 is a cup-shaped concave portion in which a valve body portion 44 that is an end portion on the opposite side of the bearing cover 30 side of the camshaft 40 is inserted and rotatably supported.
The camshaft holding portion 21 has a function as a valve body when the valve body portion 44 of the camshaft 40 functions as a valve body of a rotary valve, and is configured to communicate with the oil passages 25 to 28.

The intake side tappet holding part 22 and the exhaust side tappet holding part 23 respectively support the intake side tappet 50 and the exhaust side tappet 60 so as to be able to reciprocate in a direction perpendicular to the central axis of the camshaft 40 (vertical direction in FIG. 1). It is a part to do.
The intake side tappet holding part 22 and the exhaust side tappet holding part 23 are each formed in a through hole shape into which the outer peripheral surfaces of the shaft parts 51 and 61 of the intake side tappet 50 and the exhaust side tappet 60 are inserted and guided.

The cylinder part 24 is a part into which a piston 70 attached to the exhaust side tappet 60 is inserted.
The cylinder portion 24 is configured by partially expanding the vicinity of the end portion on the camshaft 40 side of the exhaust side tappet holding portion 23.
The cylinder portion 24 has a cylinder bore having a uniform inner diameter along the central axis direction, and the piston 70 is inserted from the opening on the camshaft 40 side.
The inner peripheral surface of the cylinder part 24 is slidable with the outer peripheral surface of the piston 70.

The oil passage 25 sucks oil (lubricating oil) stored in an oil reservoir provided in the lower portion of the crankcase 20 and introduces it into the camshaft holding portion 21.
An end portion of the oil passage 25 on the camshaft holding portion 21 side communicates with a space portion formed in the vicinity of the end surface of the camshaft 40.
The oil passage 26 introduces oil introduced into the camshaft holding portion 21 from the oil passage 25 into the cylinder portion 24.
The end of the oil passage 26 on the camshaft holding portion 21 side is disposed to face the outer peripheral surface in the vicinity of the end of the camshaft 40.
The oil passage 25 and the oil passage 26 communicate with each other through a notch 45 formed at the end of the camshaft 40 when the camshaft 40 is in a predetermined angle range, and are blocked in other cases ( Not communicate).
The end of the oil passage 26 on the cylinder portion 24 side is open to the inner peripheral surface portion of the cylinder portion 24.

The oil passage 27 introduces the oil pushed out from the cylinder portion 24 by the piston 70 into the camshaft holding portion 21.
The oil passage 28 is a discharge passage that conveys the oil introduced from the oil passage 27 to the camshaft holding portion 21 to a location that requires lubrication.
The ends of the oil passage 27 and the oil passage 28 on the camshaft holding portion 21 side are arranged substantially symmetrically with respect to the central axis of the camshaft 40 at the axially central portion of the inner peripheral surface of the camshaft holding portion 21. Yes.
The ends of the oil passage 27 and the oil passage 28 on the camshaft holding portion 21 side are formed so that oil can be supplied to the outer peripheral surface portion of the valve body portion 44 over a predetermined range in the circumferential direction.
When the camshaft 40 is within a predetermined angle range, the oil passage 27 and the oil passage 28 communicate with each other through a communication hole 46 formed in the camshaft 40, and are blocked in other cases. ing.

The bearing cover 30 is a lid-like member that substantially closes the opening of the crankcase 20.
The bearing cover 30 holds a bearing 31 that rotatably supports the end of the camshaft 40 and a main bearing (not shown) that rotatably supports the end of the crankshaft.
An oil seal 32 that prevents oil leakage is provided outside the bearing 31.

The camshaft 40 is a rotating shaft that rotates at half the speed in conjunction with the crankshaft and drives the intake and exhaust valves.
The end of the camshaft 40 on the bearing cover 30 side is supported by a bearing 31.
An end portion (valve element portion 44) of the camshaft 40 on the camshaft holding portion 21 side is rotatably supported by using the camshaft holding portion 21 as a sliding bearing.
The camshaft 40 includes a driven gear 41, an intake cam 42, an exhaust cam 43, a valve body 44, a notch 45, a communication hole 46, and the like.

  The driven gear 41 is driven by a drive gear provided on the crankshaft. The driven gear 41 has twice as many teeth as the drive gear.

The intake cam 42 and the exhaust cam 43 are rotating cams having a cam profile in which a part on the circumference of the cam shaft 40 protrudes to the outer diameter side, and the intake side tappet 50 and the exhaust side tappet 60 are arranged at a predetermined valve timing. Each is pressed to open and close the intake and exhaust valves.
The intake cam 42 and the exhaust cam 43 are sequentially arranged from the driven gear 41 side (bearing cover 30 side).

The valve body portion 44 is a cylindrical portion formed at the end of the camshaft 40 opposite to the bearing cover 30 side, and is inserted into the camshaft holding portion 21.
The valve body 44 is a valve of a rotary valve that switches communication and blocking between the oil passage 25 and the oil passage 26 and communication and blocking between the oil passage 27 and the oil passage 28 according to the rotation of the camshaft 40. Functions as a body.

The valve body portion 44 is formed with a notch 45 and a communication hole 46.
The notch 45 is a recess formed so as to communicate from the end surface side to the outer peripheral surface side in a part of the circumference of the valve body portion 44.
The notch 45 is formed between the oil passage 25 and the oil passage when the camshaft 40 is in a predetermined angle range in which the lift of the exhaust valve decreases (the piston 70 moves out of the cylinder portion 24 (withdrawn)). 26, the suction oil passage is made available, and in other cases, the oil passage 25 and the oil passage 26 are blocked.

The communication hole 46 is a through hole formed along the radial direction at an intermediate portion in the axial direction of the valve body portion 44.
When the camshaft 40 is in a predetermined angular range in which the camshaft 40 moves in a direction in which the lift of the exhaust valve increases (the piston 70 enters (pushes in) the cylinder portion 24), the communication hole 46 is connected to the oil passage 27 and the oil passage. 28, the discharge oil passage is made available, and in other cases, the oil passage 27 and the oil passage 28 are blocked.

The intake-side tappet 50 and the exhaust-side tappet 60 are driven by the reaction force of the intake cam 42, the cam surface of the exhaust cam 43, and a valve spring (not shown), respectively, and the intake valve and exhaust via the push rod P and the rocker arm (not shown). Each valve is driven.
The intake-side tappet 50 and the exhaust-side tappet 60 have cam follower portions 52 and 62 that are formed so as to protrude in an umbrella shape on the outer diameter side at the end portions of the cylindrical shaft portions 51 and 61 on the camshaft 40 side. It is configured.
The shaft portions 51 and 61 are arranged in parallel so as to be orthogonal to the central axis of the camshaft 40.
The shaft portions 51 and 61 and the cam follower portions 52 and 62 are integrally formed of, for example, a metal material such as an iron-based alloy or an aluminum-based alloy, or a resin material.
A concave portion into which the end portion of the push rod P is inserted is formed on the end surface of the shaft portions 51 and 61 opposite to the camshaft 40 side.
The intake side tappet 50 and the exhaust side tappet 60 have shaft portions 51 and 61 supported by an intake side tappet holding portion 22 and an exhaust side tappet holding portion 23 formed in the crankcase 20 so as to be movable in the axial direction. Yes.

The piston 70 is a cylindrical member that is inserted into the cylinder portion 24 and sucks oil into the cylinder portion 24 or discharges oil from the cylinder portion 24.
The piston 70 is integrally formed of, for example, a resin material that is lighter in specific gravity than the material of the exhaust side tappet 60 and has elasticity.
The piston 70 has a through hole in which the shaft portion 61 of the exhaust side tappet 60 is press-fitted and fixed near the central axis.
The end of the piston 70 on the camshaft 40 side is in contact with the cam follower 62 of the exhaust side tappet 60.
The end of the piston 70 opposite to the camshaft 40 side is formed flat along a plane substantially perpendicular to the central axis.

Hereinafter, the operation of the oil pump according to the first embodiment will be described.
FIG. 2 is a diagram illustrating the operation of the oil pump according to the first embodiment.
FIG. 2A shows a state during inhalation, and FIG. 2B shows a state during discharge.
FIG. 2 basically shows a state cut by a plane including the rotation axis of the camshaft (the same plane as that in FIG. 1). It is shown in the state seen from.

At the time of suction shown in FIG. 2 (a), after the exhaust valve is opened and the lift is maximized, the lift is decreasing (moving in the closing direction), that is, the piston 70 is a cylinder. It is in a state of moving in the direction of being pulled out from the portion 24.
At this time, in the camshaft holding portion 21, the notch 45 is in a position where the oil passage 25 and the oil passage 26 communicate with each other, and the oil flows from the oil reservoir (not shown) into the oil passage 25, the notch 45, and the oil passage 26. Are sequentially sucked into the cylinder portion 24.
At this time, the oil passage 27 and the oil passage 28 are blocked by the outer peripheral surface of the valve body 44.

On the other hand, at the time of discharge shown in FIG. 2B, the exhaust valve moves in a state where the lift is increasing (moving in the opening direction), that is, in the direction in which the piston 70 is pushed into the cylinder portion 24. It is in a state of being.
At this time, in the camshaft holding portion 21, the communication hole 46 is in a position where the oil passage 27 communicates with the oil passage 28, and the oil flows from the cylinder portion 24 into the oil passage 27, the communication hole 46, and the oil passage 28. Are sequentially discharged to a location in the engine 1 where lubrication is necessary.
Such an intake state and a discharge state are sequentially repeated according to the rotation of the camshaft 40 during the operation of the engine 1, whereby oil can be pumped to each part of the engine 1.

According to Example 1 demonstrated above, the following effects can be acquired.
(1) The cylinder portion 24 into which the piston 70 provided on the exhaust side tappet 60 is inserted is formed in the crankcase 20, and the oil passages 25 and 26 that are supply oil passages to the cylinder portion 24 and the discharge from the cylinder portion 24. An oil pump capable of pumping oil with a simple configuration is configured by switching between communication and blocking of the oil passages 27 and 28, which are oil passages, with a rotary valve having a valve body portion 44 formed on the camshaft 40. Can do.
For this reason, forced lubrication is easy even in general-purpose engines with severe cost constraints, and the amount of oil mist generated inside the engine is greatly reduced compared to splash lubrication, reducing oil consumption and exhaust gas properties. Can be improved. It is also possible to simplify the breather system for processing oil mist.
(2) By attaching the resin-made piston 70 to the exhaust side tappet 60, it is possible to reduce the weight of the valve drive system parts, improve the followability, and prevent the occurrence of valve surging and the like.
In addition, by attaching a separate piston to only the exhaust side tappet 60, the parts of the intake side tappet 50 and the exhaust side tappet 60 can be shared.

Next, an oil pump according to a second embodiment to which the present invention is applied will be described.
In the second embodiment, portions that are substantially the same as those in the first embodiment described above are denoted by the same reference numerals, description thereof is omitted, and differences are mainly described.

FIG. 3 is a schematic diagram illustrating a configuration of a piston in the oil pump according to the second embodiment.
The piston 70 according to the second embodiment is provided with a low-rigidity portion 71 that lowers the rigidity against a compressive load in the central axis direction and is easily elastically deformed at an intermediate portion in the central axis direction (reciprocating direction).
In the low-rigidity portion 71, a plurality of annular portions 72 are arranged at intervals in the central axis direction, and the annular members 72 of each layer are connected to each other by a connecting portion 73.
The annular portion 72 is a flat disk-shaped member formed along a plane orthogonal to the central axis of the piston 70.
An opening is formed at the center of the annular portion 72, and the shaft portion 61 of the exhaust side tappet 60 is inserted.
The annular portion 72 and the connecting portion 73 are integrally formed of an elastic resin material together with the other portion of the piston 70.

A plurality of connecting portions 73 are arranged in the circumferential direction at the outer peripheral edge of the annular portion 72 in a distributed manner.
The connecting portions 73 erected from one surface portion of a certain annular portion 72 are alternately arranged offset from the connecting portion 73 erected from the other surface portion in the circumferential direction of the piston 70.
For this reason, when the hydraulic pressure from the oil in the cylinder portion 24 acts on the crown surface (the upper surface in FIG. 3) of the piston 70, the annular member 72 of each layer bends, thereby causing the piston 70 to move in the central axis direction (FIG. 3). The elastic deformation compressed along the vertical direction in FIG.

  According to the second embodiment described above, in addition to the effects substantially similar to the effects of the first embodiment described above, the piston 70 is elastically deformed by the input received from the oil, so that the hydraulic pressure in the cylinder portion 24 is rapidly increased. It is possible to prevent the change, suppress the pulsation of the discharge pressure, and improve the durability of the oil pump.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
The structure, shape, material, manufacturing method, arrangement, quantity, and the like of each constituent member constituting the oil pump and the engine can be appropriately changed without being limited to the embodiments.
For example, the engine of the embodiment is an OHV, but the present invention is not limited to this, and the present invention can also be applied to a side valve (SV) engine.
In the embodiment, the piston is provided on the exhaust side tappet, but it may be provided on the intake side tappet.
In the embodiment, a part of the camshaft is used as a valve body of the rotary valve. However, the present invention is not limited to this, and a part of the crankshaft or a part of another rotating member linked with the camshaft is used as the valve body. It may be used as
Also, the configuration for communicating the oil passage according to the angular position of the camshaft is not limited to the notch and the communication hole as in the embodiment, and can be changed as appropriate.
Further, the configuration for allowing the elastic deformation of the piston is not particularly limited.

DESCRIPTION OF SYMBOLS 1 Engine 10 Cylinder 11 Fin 12 Bolt hole 20 Crankcase 21 Camshaft holding part 22 Intake side tappet holding part 23 Exhaust side tappet holding part 24 Cylinder part 25-28 Oil path 30 Bearing cover 31 Bearing 32 Oil seal 40 Camshaft 41 Driven gear 42 intake cam 43 exhaust cam 44 valve body 45 notch 46 communication hole 50 intake side tappet 51 shaft 52 cam follower 60 exhaust side tappet 61 shaft 62 cam follower P push rod 70 piston 71 low rigidity part 72 annular part 73 Connecting part

Claims (3)

A camshaft having a cam provided on the crankcase and driving a valve;
An oil pump provided in an engine having a tappet that reciprocates following the cam surface of the cam and transmits a driving force to a valve,
A piston provided on the tappet;
A cylinder into which the piston is inserted;
A suction oil passage for introducing oil into the cylinder;
A discharge oil passage for discharging the oil from the cylinder;
A valve body that rotates in conjunction with rotation of the camshaft; and when the piston moves in a direction of being pulled out of the cylinder, the suction oil passage is communicated and the discharge oil passage is shut off; An oil pump comprising: a rotary valve that shuts off the supply oil passage and communicates the discharge oil passage when moving in a direction of being pushed into the cylinder. 2. The cylinder according to claim 1, wherein the cylinder is formed in a cylindrical shape having an opening into which an outer peripheral surface portion of the tappet is inserted in a central portion by a resin material having a specific gravity lighter than a material constituting the tappet. Oil pump. The oil pump according to claim 1, wherein the piston is elastically deformed in a direction in which an axial dimension is compressed in accordance with an increase in hydraulic pressure in the cylinder.

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