JP2014234811A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine for achieving light-weight and downsizing, and reduction of fuel consumption.SOLUTION: An internal combustion engine 10 for vertically moving a piston 13 in cylinder bores 14 and 15 by combustion inside a combustion chamber 21 includes: a crank shaft 17; a cam shaft 31; a suction valve 22; an exhaust valve 24; and a swing arm 29. A valve shaft 26 of the suction valve and the exhaust valve is distributed to both sides in a position deviated in an axial direction of the cam shaft, and inclined in a direction toward center axes AX14 and AX 15 of the cylinder bores. A contact roller 29a of the swing arm which comes into contact with a cam surface of the cam shaft is located on the center side of the cylinder bore and arranged so as to be overlapped. The crank shaft, the cam shaft and the contact roller of the swing arm are arranged in a position being off-set in a thrust direction T of the piston.

Description

  The present invention relates to an internal combustion engine, and to a structure that realizes light weight, downsizing, and low fuel consumption.

The internal combustion engine moves the piston up and down by supplying liquid fuel or gaseous fuel to the combustion chamber and combusting it, and by providing a mechanism for converting the reciprocating motion of the piston into rotational drive with a crankshaft, for example, It is mounted on a vehicle as a drive source.
In this type of internal combustion engine, a valve drive mechanism that drives an intake valve and an exhaust valve disposed in a combustion chamber is incorporated in the cylinder head, and the valve drive mechanism transmits the rotational driving force of the crankshaft. The camshaft is generally operated by rotating it.

  In Patent Document 1, an intake valve and an exhaust valve are opened and closed by a single camshaft and a pair of rocker arms. Further, the rotation of the crankshaft is transmitted to the camshaft through a pair of bevel gears and an intermediate shaft, thereby reducing the size of the engine.

JP 2000-230607 A

  However, in the internal combustion engine as described in Patent Document 1, rocker shafts are arranged on both sides of a cam shaft located in the vicinity of the center axis of the cylinder bore, and the outer end portion of the rocker arm through which the rocker shaft passes through the center portion. Since the intake valve and the exhaust valve are operated in this way, the angle between the intake valve and the exhaust valve becomes large, and the combustion chamber cannot be made compact.

  Furthermore, since the piston in the cylinder is connected to the crankshaft via a connecting rod and moves up and down, a phenomenon occurs in which the piston is pressed against the inner wall of the cylinder with a large side force during the expansion stroke during combustion.

As a result, it has become difficult to reduce fuel consumption due to the limitations of downsizing the internal combustion engine and the combustion chamber, and fuel consumption has increased due to side forces applied to the piston.
SUMMARY OF THE INVENTION An object of the present invention is to provide an internal combustion engine that realizes a reduction in weight and size and a reduction in fuel consumption.

  A first aspect of the invention relating to an internal combustion engine that solves the above-described problem is an internal combustion engine that accommodates in a cylinder bore a piston that causes an air-fuel mixture supplied to a combustion chamber to burn and move up and down. A rotating crankshaft; a valve member for each port that opens and closes a pair of ports that open to the combustion chamber; a swing arm that is disposed for each pair of valve members to open and close the valve member; and the swing arm A camshaft having a drive cam that transmits a driving force to the camshaft, and a power transmission mechanism that transmits the rotational drive of the crankshaft to the one end side of the camshaft as the rotational power of the camshaft. A base end side supported by the swing fulcrum; a tip end side contacting the shaft portion of the valve member; and a cam contact portion contacting the cam surface of the drive cam between the two. And said The shaft portions of the pair of valve members are distributed to both sides centered on the cam shaft at positions shifted in the axial direction of the cam shaft, and the posture viewed from the axial direction of the cam shaft is the center of the cylinder bore The swing arm is inclined in a direction toward the shaft, and the cam contact portions are positioned on the center axis side of the cylinder bore rather than both end sides of the swing arm when viewed from the axial direction of the cam shaft, and overlap each other. The crankshaft, the camshaft, and the cam contact portion of the swing arm are arranged at positions offset to the thrust side of the piston with respect to the central axis of the cylinder bore.

According to a second aspect of the invention relating to the internal combustion engine that solves the above problem, in addition to the specific matter of the first aspect, the shaft portion of the pair of valve members has an end portion that contacts the swing arm at the cylinder bore. Is located in the space extending in the direction of the central axis, and the inclination angle of the extension line extending the central axis of the shaft portion in the direction intersecting the central axis of the cylinder bore is greater on the thrust side of the piston. The piston is inclined so as to be larger than the anti-thrust side of the piston.
According to a third aspect of the invention relating to an internal combustion engine that solves the above problem, in addition to the specific matter of the first or second aspect, an intake port and an exhaust port that open to the combustion chamber are used as the pair of ports. In addition, the intake port having a larger area than the exhaust port is disposed on the thrust side of the piston, and the exhaust port is disposed on the anti-thrust side of the piston.

According to a fourth aspect of the invention relating to the internal combustion engine that solves the above problem, in addition to the specific matter of any one of the first to third aspects, the swing arm is formed in the same shape, and the valve member It is characterized by being installed every time.
According to a fifth aspect of the invention relating to the internal combustion engine that solves the above problem, in addition to the specific matter of any one of the first to fourth aspects, the power transmission mechanism includes one end of the crankshaft and the camshaft. The first and second bevel gears arranged at the respective parts, the third and fourth bevel gears that mesh with the first and second bevel gears, respectively, and the third and fourth bevel gears at both ends. And a power transmission shaft installed in a posture orthogonal to the extension lines of the crankshaft and the camshaft.

As described above, according to the first aspect of the present invention, the cam contact portion that contacts the cam surface is disposed between the swing fulcrum of the swing arm and the tip end side. It can be laid out in a free position, and does not hinder downsizing of the combustion chamber or the like. Since the swing arm is arranged so that the cam contact portion is located on the center axis side of the cylinder bore and overlaps, the inclination angle of the shaft portion of the valve member with respect to the cylinder bore center axis can be reduced, and the combustion chamber is made compact. be able to.
Furthermore, by offsetting the cam contact portions of the crankshaft, camshaft and swing arm toward the thrust side of the piston, the camshaft can be brought closer to the crankshaft, and the inner wall can be used during the expansion stroke when the piston in the cylinder is burning. It is possible to reduce the side force that is pressed against the surface. For this reason, the power transmission mechanism between the crankshaft and the camshaft can be downsized in the vertical movement direction of the piston, and fuel consumption can be reduced by making the internal combustion engine compact. In addition, fuel consumption can be reduced by reducing the side force as a load of the piston.

According to said 2nd aspect of this invention, by making the inclination angle of the axial part in a valve member larger in the direction of the valve member arrange | positioned at the thrust side rather than the valve member arrange | positioned at the anti-thrust side of a piston. In addition, the cam contact portion of the camshaft or swing arm can be offset more largely to the thrust side of the piston. For this reason, the size of the valve member arranged on the thrust side of the piston, the size of the power transmission mechanism between the crankshaft and the camshaft, and the size of the side force that becomes the load of the piston can be adjusted as desired. .
According to the third aspect of the present invention, the intake port having a larger opening area than the exhaust port is positioned on the thrust side of the piston (the exhaust port is on the anti-thrust side of the piston). Similarly, the valve member for opening and closing the intake port can be further offset to the thrust side of the piston. For this reason, the camshaft can be largely offset together on the same side.

According to the fourth aspect of the present invention, since the swing arm having the same shape is installed for each valve member, the swing arm can be a common component. For this reason, it is possible to reduce the number of parts, reduce the cost, and improve the assembly workability.
According to the fifth aspect of the present invention, power is transmitted from the crankshaft to the camshaft via the power transmission shaft and the pair of bevel gears respectively disposed at both ends thereof. It can be shortened (miniaturized) to be compact, and the structural member can be made lighter than a chain or belt drive type. For this reason, fuel consumption can be reduced effectively.

1 is a view showing an embodiment of an internal combustion engine according to the present invention, and is a partially sectional perspective elevation view seen from one direction showing the overall configuration. FIG. 2 is a partially sectional perspective elevational view showing an entire configuration including a periphery of a piston as viewed from a direction orthogonal to one direction in FIG. 1. FIG. 2 is a partially sectional perspective elevational view showing the entire configuration including the periphery of a power transmission mechanism as viewed from a direction orthogonal to one direction in FIG. 1. FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 showing a main part configuration of the cylinder head as viewed from above. FIG. 3 is a partially sectional perspective elevational view showing the periphery of the valve drive mechanism viewed from the same direction as FIG. 2. It is a partially transparent bottom view which shows the layout of the valve drive mechanism in the cylinder head seen from the cylinder bore side.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 6 are views showing an embodiment of an internal combustion engine according to the present invention.
1 to 3, an internal combustion engine 10 is manufactured in a monoblock structure in which a cylinder block 11 and a cylinder head 12 are integrated, and is mounted on a vehicle as a drive source for rolling a wheel (not shown). .

  The cylinder block 11 is constructed in two cylinders in which cylinder bores (inner cylinders) 14 and 15 that accommodate a piston 13 in a vertically movable manner are arranged in parallel. The cylinder head 12 is located above the cylinder block 11 and forms a combustion chamber 21 corresponding to each of the cylinder bores 14, 15 between the piston 13. The combustion chamber 21 is formed such that a ceiling surface 21 a having a curved cross section faces the upper surface 13 a of the piston 13, and an intake port (intake port) 23 that is opened and closed by an intake valve (valve member) 22 is formed on the ceiling surface 21 a. And an exhaust port (exhaust port) 25 opened and closed by an exhaust valve (valve member) 24 is opened.

  The internal combustion engine 10 supplies a mixture of a liquid fuel such as gasoline or a gaseous fuel such as CNG (Compressed Natural Gas) and combustion air taken from outside air into the combustion chamber 21 and then sparks and burns with a plug 30. As a result, the piston 13 is moved up and down. At this time, in the internal combustion engine 10, the intake valve 22 opens and closes the intake port 23 at the intake timing to repeatedly supply the air-fuel mixture into the combustion chamber 21, and the exhaust valve 24 opens and closes the exhaust port 25 at the exhaust timing. The exhaust gas after combustion in the combustion chamber 21 is repeatedly exhausted.

  In the cylinder block 11, the pistons 13 in the cylinder bores 14 and 15 are respectively connected to the crankshaft 17 by connecting rods 16, and the vertical movement of the piston 13 is converted into the rotational drive of the crankshaft 17 to roll the wheels. Generate driving force to travel. The crankshaft 17 is housed in a lower case 19 that functions as an oil pan for storing lubricating oil.

In the cylinder head 12, an intake valve 22 and an exhaust valve 24 are disposed as valve members on the opening edges 23 a and 25 a of the intake port 23 and the exhaust port 25 on the ceiling surface 21 a forming the combustion chamber 21.
The intake valve 22 and the exhaust valve 24 include a valve shaft 26 that is a shaft portion, and the valve shaft 26 is closed in close contact with the opening edges 23a and 25a when the coil spring 27 is biased in the pulling direction. .

The upper end portion of the valve shaft 26 is in contact with the distal end portion of a swing arm 29 whose base end portion is swingably supported by the adjuster pin 28. In the swing arm 29, a contact roller (cam contact portion) 29a is rotatably attached to an intermediate portion, and the cam surface 32a of the intake cam 32 or the exhaust cam 33 whose upper portion of the contact roller 29a rotates integrally with the cam shaft 31. , 33a.
With this structure, the intake cam 32 and the exhaust cam 33 function as a drive cam that presses the contact roller 29a that contacts the cam surfaces 32a and 33a when rotating integrally with the cam shaft 31. Accordingly, the swing arm 29 swings with the base end portion 29b supported by the tip end portion 28a (see FIG. 5) of the adjuster pin 28 as a swing fulcrum, and the upper end portion 26b contacts the tip end portion 29c. The shaft 26 can be moved in the forward / backward direction against the urging force of the coil spring 27. As a result, the intake valve 22 and the exhaust valve 24 can be lifted from a state of being in close contact with the opening edges 23a and 25a of the intake port 23 and the exhaust port 25, thereby opening the opening edges 23a and 25a.

  In other words, the valve shafts 26 of the intake valve 22 and the exhaust valve 24 are arranged on both the left and right sides with respect to the cam shaft 31 shown in FIG. The intake valve 22 and the exhaust valve 24 are operated by a swing arm 29 disposed at a predetermined interval in the axial direction of the cam shaft 31 (the front-rear direction in FIG. 2).

That is, as shown in FIG. 5, the swing arm 29 for the intake valve 22 and the swing arm 29 for the exhaust valve 24 are arranged so that the contact rollers 29a overlap each other when viewed from the axial direction of the cam shaft 31 (the cylinder bores 14, 15). Are arranged in the vicinity of the central axes AX14 and AX15). These swing arms 29 are formed in the same shape so that they can be used as common parts for the intake valve 22 and the exhaust valve 24 only by reversing the directions on the front and back in the figure.
The swing arm 29 is laid out so that the contact roller 29a is positioned in the vicinity of the center axes AX14 and AX15 of the cylinder bores 14 and 15, thereby reducing the inclination angle of the valve shaft 26 (the intake valve 22 and the exhaust valve 24). it can. In FIG. 4, the intake port 23 communicates with an intake manifold (pipe) 51. The exhaust port 25 communicates with the exhaust pipe 52 and further communicates with the catalyst 53. The internal combustion engine 10 is started by the rotational force of the starter 55, and the air compressor 56 is driven by the crankshaft 17.

  As shown in FIG. 1, the cam shaft 31 has a disk-shaped portion (journal portion) 31 a formed on a bearing member 36 that is integrally formed in the cylinder head 12 so as to be positioned at two locations separated in the axial direction. The bearing is rotatably supported. The camshaft 31 is connected to the crankshaft 17 via a power transmission mechanism 40. That is, the camshaft 31 rotates synchronously with the crankshaft 17 so that the intake cam 22 and the exhaust cam 33 are interlocked (rotated) with the vertical movement of the piston 13 to open and close the intake valve 22 and the exhaust valve 24. It has become.

The power transmission mechanism 40 includes a first bevel gear (bevel gear) 41 fixed to one end portion of the crankshaft 17, a second bevel gear 42 fixed to one end portion of the camshaft 31, and the first, Third and fourth bevel gears 43 and 44 meshing with each of the second bevel gears 41 and 42, and an intermediate shaft (power transmission shaft) in which the third and fourth bevel gears 43 and 44 are fixed to both ends in the axial direction. 45). The crankshaft 17 and the camshaft 31 are supported in such a manner that the shaft centers are parallel to each other and that the extension lines of the shaft centers are orthogonal to the intermediate shaft 45. The fourth bevel gears 41 to 44 are connected so as to be engaged with each other.
With this structure, the crankshaft 17 can transmit the rotation to the intermediate shaft 45 by rotating the third bevel gear 43 meshingly connected to the first bevel gear 41. Further, the rotation of the intermediate shaft 45 is transmitted to the second bevel gear 42 which is meshed with and connected to the fourth bevel gear 44, and the cam shaft 31 can be rotated. The intermediate shaft 45 is rotatably supported by a plurality of bearing mechanisms, which are not particularly shown, in a front case 49 disposed at the end of the cylinder block 11.
Therefore, in the power transmission mechanism 40, the rotation of the crankshaft 17 is applied to the camshaft 31 without fixing a pulley or a sprocket to one end of the crankshaft 17 and the camshaft 31 and winding a chain or belt around them. Can communicate. For this reason, in the power transmission mechanism 40, excessive tension is not applied to one end portions of the crankshaft 17 and the camshaft 31, and the bearing strength on the one end portion side of the camshaft 31 can be reduced.

Further, in the internal combustion engine 10 of the present embodiment, the forward and backward directions of the valve shaft 26 in the intake valve 22 and the exhaust valve 24, that is, the extension line of the valve shaft 26 is the center axis AX 14 of the cylinder bores 14 and 15 in the cylinder block 11. It is inclined to pass through AX15.
Specifically, the cylinder head 12 of the internal combustion engine 10 includes an extension line AX26 of the valve shaft 26 in the intake valve 22 and the exhaust valve 24 with respect to the central axis AX14 of the cylinder bore 14 (also on the cylinder bore 15 side). It is constructed so that it may be inclined in the direction along the line and intersect at the inclination angles θ1 and θ2. In other words, the valve head 26 of the intake valve 22 and the exhaust valve 24 is in a tilted posture such that the valve shaft 26 rides on a radial extension line inclined at the tilt angles θ1 and θ2 from the intersecting position on the center axis AX14 of the cylinder bore 14. Is placed inside. Note that the inclination angles θ1 and θ2 of the valve shaft 26 with respect to the cylinder bore 14 are inclination angles when viewed from the direction orthogonal to the cam shaft 31 as shown in FIG. 1, and as shown in FIG. When viewed from the axial direction of the shaft 31, the inclination angles are θ3 and θ4 with respect to the central axis AX14.
With this structure, the internal combustion engine 10 can separate the intake cam 32 and the exhaust cam 33 from the conventional internal combustion engine in which the inclination angles θ1 and θ2 are 0 °. For this reason, on the cylinder bore 15 side, the cam shaft 31 is supported by arranging the disk-shaped part (journal part) 31a and the bearing member 36 on the central axis AX15 using the separation space S. Further, with respect to the cylinder bore 14, a disk-shaped portion (at a position biased toward the end portion side of the cam shaft 31, that is, the side close to the second bevel gear 42 side with respect to the center axis AX 14, using the separation space S. (Journal portion) 31a and bearing member 36 are arranged to support the end of cam shaft 31.
Therefore, in this internal combustion engine 10, an excessive load is not applied to one end portion side of the cam shaft 31 to which the second bevel gear 42 of the power transmission mechanism 40 is fixed. The bearing on the one end side of 31 can be omitted. For this reason, the cam shaft 31 can rotatably support the end portion of the cam shaft 31 without providing a bearing between the intake cam 32 and the second bevel gear 42. As a result, the internal combustion engine 10 can be reduced in size and weight by shortening the camshaft 31 and reducing the number of disk-shaped portions (journal portions) 31a and bearings 36. Fuel consumed by weight can be reduced.

Further, the power transmission mechanism 40 of the internal combustion engine 10 reduces the rotational speed of the crankshaft 17 by half due to the relationship between the reciprocating motion (vertical motion) of the piston 13 and the opening / closing motions of the intake valve 22 and the exhaust valve 24. It is necessary to rotate the cam shaft 31. For this reason, in the power transmission mechanism 40, the number of teeth of the second bevel gear 42 is doubled relative to the number of teeth of the fourth bevel gear 44, and the second bevel gear 42 has a larger diameter than the fourth bevel gear 44. It has become.
With this structure, in the power transmission mechanism 40, the meshing surfaces of the first and third bevel gears 41 and 43 are reduced by performing the deceleration of the camshaft 31 on the meshing surfaces 42a and 44a of the second and fourth bevel gears 42 and 44. The length of the camshaft 31 can be shortened compared with the case where deceleration is performed by 41a and 43a.
Here, in this structure, the diameter of the second bevel gear 42 is made larger than that of the fourth bevel gear 44 in accordance with the gear ratio of the meshing surfaces 42 a, 44 a, and these meshing surfaces 42 a, 44 a It inclines in the direction approaching the orthogonal direction. Therefore, although not shown in particular, the pressure in the orthogonal direction applied to the camshaft 31 is orthogonal to the pressure F applied from the meshing surface 44a of the fourth bevel gear 44 to the meshing surface 42a of the second bevel gear 42. In this case, the pressure in the orthogonal direction applied to the camshaft 31 can be reduced. For this reason, in this power transmission mechanism 40, even if the bearing on the second bevel gear 42 side of the cam shaft 31 is omitted, the power transmission mechanism 40 is a bearing composed of a disk-shaped portion (journal portion) 31a and a bearing member 36 installed in the separation space S. Sufficiently reliable and can be supported rotatably.

In the internal combustion engine 10 of the present embodiment, first, the crankshaft 17 is offset by shifting the axis AX17 by the shift amount OS1 to the left in FIGS. 2 and 3 with respect to the central axes AX14 and AX15 of the cylinder bores 14 and 15. In place.
Meanwhile, the crankshaft 17 rotates in the clockwise direction indicated by an arrow in FIG. 2, whereas the piston 13 is connected to the crankshaft 17 by a connecting rod 16 and moves up and down. Therefore, the piston 13 moves up and down while swinging in the left and right directions in FIG. 2 in the cylinder bores 14 and 15, and the left inner wall of the cylinder bores 14 and 15 in FIG. 2 during the expansion stroke in the combustion chamber 21. Descent while receiving the side force that is pressed against. The direction in which the side force of the crankshaft 17 is received, that is, the left direction in FIG. 2 is referred to as the thrust direction T of the piston 13. Conversely, the right direction in FIG. 2 is referred to as the anti-thrust direction R of the piston 13.
In this structure, since the crankshaft 17 is offset in the thrust direction T side of the piston 13, the piston 13 can be lowered in a posture as vertical as possible, and the piston 13 is pressed against the inner walls of the cylinder bores 14 and 15. The side force generated can be reduced. As a result, the piston 13 can be efficiently moved up and down, in other words, fuel consumption when taking out the same driving force as that without offset can be reduced.

Further, as shown in FIG. 6, the internal combustion engine 10 has an exhaust port on the anti-thrust direction R side opposite to the opening edge 23 a of the intake port 23 on the thrust direction T side of the piston 13 on the ceiling surface 21 a of the combustion chamber 21. The opening is larger in area than the 25 opening edges 25a. Along with this, the diameter of the intake valve 22 that opens and closes the intake port 23 is increased, and the valve shaft 26 located at the center 22c of the intake valve 22 is also shifted to the thrust direction T side accordingly.
For this reason, the cam shaft 31 has its axis AX31 shifted to the left side in FIGS. 2 and 3 with respect to the center axes AX14 and AX15 of the cylinder bores 14 and 15, as in the crankshaft 17 (axis AX17). It is installed at an offset position that is shifted by a small amount. Further, as shown in FIG. 5, the valve shaft 26 of the intake valve 22 makes the inclination angle θ3 of the extension line AX26 with respect to the central axes AX14 and AX15 of the cylinder bores 14 and 15 larger than the inclination angle θ4 on the exhaust valve 24 side. It is so inclined. A swing arm 29 for operating the intake valve 22 and the exhaust valve 24 is separately attached to each valve, and the inclination of the valve shaft 26 can be freely set to some extent (thereby adjusting the inclination of the valve shaft 26). 3, the contact roller 29a on the intake valve 22 side and the camshaft 31 can be offset by a shift amount OS2 as shown in Fig. 3. At this time, in order to make the combustion chamber 21 compact, the valve shaft 26 includes a cylinder bore 14, In this embodiment, the camshaft 31 is offset in the direction close to the crankshaft 17 by utilizing the enlargement of the intake port 23. However, the present invention is not limited to this, and the camshaft 31 is close to the crankshaft 17 even when the intake port 23 and the exhaust port 25 open with the same diameter. It can be offset to the direction.
By adopting this structure, the internal combustion engine 10 can shorten the distance between the crankshaft 17 and the camshaft 31 as compared with the conventional one, and can shorten the length of the intermediate shaft 45 to some extent. Therefore, in the internal combustion engine 10, the height of the cylinder block 11 and the cylinder head 12 can be shortened to reduce the size and weight, and the consumed fuel can be reduced.

  Thus, in the present embodiment, the combustion efficiency can be improved by making the combustion chamber 21 compact, and the side force added to the piston 13 that moves up and down in the cylinder bores 14 and 15 can be reduced to reduce fuel consumption. can do. Moreover, the internal combustion engine 1 can be reduced in weight and fuel consumption can be reduced.

  The scope of the present invention is not limited to the illustrated and described exemplary embodiments, but includes all embodiments that provide the same effects as those intended by the present invention. Further, the scope of the invention is not limited to the combinations of features of the invention defined by the claims, but may be defined by any desired combination of particular features among all the disclosed features. .

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Cylinder block 12 Cylinder head 13 Piston 14, 15 Cylinder bore 17 Crankshaft 21 Combustion chamber 22 Intake valve 23 Intake port 23a, 25a Open edge 24 Exhaust valve 25 Exhaust port 26 Valve shaft 27 Coil spring 28 Adjuster pin 29 Swing arm 29a Contact roller 30 Plug 31 Cam shaft 32 Intake cam 33 Exhaust cam 40 Power transmission mechanisms 41-44 Bevel gears 42a-44a Engagement surface 45 Intermediate shaft AX14, AX15 Center shaft AX26 Extension line AX17, AX31

Claims (5)

An internal combustion engine that accommodates in a cylinder bore a piston that moves up and down by burning an air-fuel mixture supplied to a combustion chamber,
A crankshaft that is rotated by the vertical movement of the piston, a valve member for each port that opens and closes a pair of ports that open to the combustion chamber, and a swing that is disposed for each pair of valve members and opens and closes the valve member An arm, a camshaft having a drive cam that transmits a driving force to the swing arm, and a power transmission mechanism that transmits rotational drive of the crankshaft to the one end side of the camshaft as rotational power of the camshaft. And
The swing arm includes a base end side supported by a swinging fulcrum, a distal end side that contacts the shaft portion of the valve member, and a cam contact portion that contacts a cam surface of the drive cam between the two, Have
The shaft portions of the pair of valve members are distributed to both sides centered on the cam shaft at positions shifted in the axial direction of the cam shaft, and the posture viewed from the axial direction of the cam shaft is the cylinder bore. Inclined in the direction toward the central axis,
The swing arm is disposed so that the cam contact portions are positioned closer to the center axis side of the cylinder bore than the both end sides of the swing arm when viewed from the axial direction of the cam shaft,
The internal combustion engine, wherein the crankshaft, the camshaft, and the cam contact portion of the swing arm are arranged at a position offset toward a thrust side of the piston with respect to a central axis of the cylinder bore.   The shaft portions of the pair of valve members are positioned in a space in which an end portion contacting the swing arm extends in the direction of the central axis of the cylinder bore and intersects the central axis of the cylinder bore. 2. The internal combustion engine according to claim 1, wherein an inclination angle of an extension line obtained by extending a central axis of the portion is inclined so that a thrust side of the piston is larger than an anti-thrust side of the piston. As the pair of ports, an intake port and an exhaust port that open to the combustion chamber,
3. The internal combustion engine according to claim 1, wherein the intake port having a larger area than the exhaust port is disposed on a thrust side of the piston, and the exhaust port is disposed on an anti-thrust side of the piston. organ.   The internal combustion engine according to any one of claims 1 to 3, wherein the swing arm is formed in the same shape and is installed for each valve member.   The power transmission mechanism includes first and second bevel gears disposed at one end portions of the crankshaft and the camshaft, and third and fourth gears engaged with the first and second bevel gears, respectively, and interlockingly rotated. A bevel gear and a power transmission shaft in which the third and fourth bevel gears are disposed at both ends and are installed in a posture orthogonal to the extension lines of the crankshaft and the camshaft. The internal combustion engine according to any one of claims 1 to 4.

Images