JP4625490B2 - Exhaust control device for 4-cycle engine - Google Patents

Description

  According to the present invention, a combustion chamber that faces the top of a piston that is slidably fitted in a cylinder bore of a cylinder block is formed between a cylinder head coupled to the cylinder block and the cylinder block, and the combustion chamber An intake valve and an exhaust valve that can open and close an intake valve port and an exhaust valve port that are provided in the cylinder head facing each other are disposed in the cylinder head so as to be openable and closable. A timing transmission mechanism having an endless cam chain is provided between one end of a camshaft and a crankshaft included in the valve device, and a cam chain chamber is formed in the cylinder block and the cylinder head for running the cam chain. Regarding the 4-cycle engine, in particular, the exhaust control device in the 4-cycle engine. About the good.

  An engine exhaust control device in which a butterfly valve for controlling in-cylinder pressure is arranged in an exhaust port connected to an exhaust valve port in a four-cycle engine is known from Patent Document 1.

Further, in a two-cycle engine, an exhaust control device is known from Patent Document 2 in which a rotary valve for switching whether exhaust flows to a low-rotation exhaust pipe or a high-rotation exhaust pipe is disposed in an exhaust port. Yes.
JP-A-2-049936 Japanese Patent No. 3786148

  However, in the one disclosed in Patent Document 1, the butterfly valve is arranged at the approximate center of the exhaust port, and the passage cross-sectional area of the exhaust port is reduced when the butterfly valve is fully opened. On the other hand, in the one disclosed in Patent Document 2, a rotary valve is arranged in the exhaust port, and the passage sectional area of the exhaust port is not reduced when fully opened, but the rotary valve is large and heavy. Yes, it is desirable to set the weight balance of the engine body appropriately while controlling the exhaust with a rotary valve, and to reduce the size of the engine body while avoiding interference between the rocker arm and other parts installed in the engine body. It is desirable to plan.

  The present invention has been made in view of such circumstances. A first object of the present invention is to appropriately set the weight balance of the engine body while controlling the exhaust with a rotary valve disposed in the exhaust port. A second object of the present invention is to provide an exhaust control device for a four-cycle engine that can control the exhaust with a rotary valve arranged at a port and avoid interference with other parts of the rotary valve to make the engine body compact. And

  In order to achieve the first object, according to the first aspect of the present invention, a combustion chamber facing the top of a piston slidably fitted in a cylinder bore of the cylinder block is coupled to the cylinder block. An intake valve and an exhaust valve, which are formed between the cylinder head and the cylinder block and can open and close the intake valve port and the exhaust valve port respectively provided on the cylinder head facing the combustion chamber, are arranged on the cylinder head so as to be openable and closable. And a timing transmission mechanism having an endless cam chain between one end of a camshaft and a crankshaft provided in a valve operating device that opens and closes the intake valve and the exhaust valve, and the cylinder block and the cylinder In a four-cycle engine in which a cam chain chamber for running the cam chain on the head is formed, A rotary valve that can change the opening area of the exhaust port provided in the cylinder head connected to the exhaust valve port is rotatable to the cylinder head at a position offset from the center of the exhaust port to the cam chain chamber side. It is characterized by being arranged.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, an engine main body configured in a water-cooled manner with the cylinder block and the cylinder head as part of constituent elements, and a front of the engine main body. Is mounted on a body frame of the motorcycle, and a water outlet and an exhaust port for guiding cooling water from the cylinder head to the radiator side are opposite to the cam chain chamber with respect to the exhaust port. The water outlet is disposed on the side of the cylinder head, and is provided on a front side surface of the cylinder head.

  In order to achieve the second object, according to a third aspect of the present invention, a combustion chamber that faces the top of a piston that is slidably fitted into a cylinder bore of the cylinder block is coupled to the cylinder block. An intake valve and an exhaust valve, which are formed between the cylinder head and the cylinder block and can open and close the intake valve port and the exhaust valve port respectively provided on the cylinder head facing the combustion chamber, are arranged on the cylinder head so as to be openable and closable. And a timing transmission mechanism having an endless cam chain between one end of a camshaft and a crankshaft provided in a valve operating device that opens and closes the intake valve and the exhaust valve, and the cylinder block and the cylinder Exhaust control of a 4-cycle engine in which a cam chain chamber is formed in the head for running the cam chain The rotary valve that can change the opening area of the exhaust port provided in the cylinder head connected to the exhaust valve port is offset from the center of the exhaust port to the side opposite to the cam chain chamber. The head is rotatably arranged.

  According to a fourth aspect of the present invention, in addition to the configuration of the first aspect of the present invention, an exhaust side cam provided on the camshaft disposed above the intake valve further includes the exhaust side cam. The rotary valve is linked and connected to the exhaust valve via a rocker arm that swings when driven, and the rotary axis of the rotary valve is set substantially parallel to the axis of the cylinder bore.

  According to a fifth aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the exhaust port has a straight portion that extends in a straight line and is provided in the cylinder head. The rotary valve is disposed on the straight portion.

  According to a sixth aspect of the present invention, in addition to the configuration of the first aspect of the present invention, a valve housing that rotatably accommodates the rotary valve is configured to assemble the rotary valve from above. The upper end surface of the valve housing is formed integrally with the cylinder head so as to be opened upward as possible, and the upper end surface of the valve housing is formed flush with the coupling surface of the cylinder head to the head cover.

  Furthermore, in addition to the structure of the invention according to any one of claims 1 to 6, the invention according to claim 7 constitutes a part of a body frame of a motorcycle and faces the frame member extending vertically, and the cylinder The exhaust port is provided in a head, and the rotary valve is rotatably disposed on the cylinder head on the side opposite to the frame member with respect to the center of the exhaust port.

  The down frame 18 of the embodiment corresponds to the frame member of the present invention.

  According to the first aspect of the present invention, since the rotary valve is disposed in the exhaust port, the passage cross-sectional area of the exhaust port does not decrease when the rotary valve is fully opened, and the rotary valve having a relatively large weight is a cylinder. Even if it is disposed on the head, the rotary valve is disposed on the cylinder head on the side closer to the hollow cam chain chamber, so that the weight balance of the engine body can be set appropriately.

  According to the second aspect of the present invention, the water outlet for guiding the cooling water from the cylinder head to the radiator side is disposed on the side opposite to the cam chain chamber with respect to the exhaust port, so that it is connected to the water outlet. The rotary valve can be arranged so as not to interfere with the water pipeline.

  According to the third aspect of the present invention, since the rotary valve is disposed in the exhaust port, the passage sectional area of the exhaust port does not decrease when the rotary valve is fully opened, and a relatively large rotary valve is disposed in the cylinder head. Even if it is installed, the rotary valve is arranged on the cylinder head at a position offset from the center of the exhaust port to the opposite side of the cam chain chamber, so that the camshaft is part of the timing transmission mechanism. It is easy to avoid the interference of the rotary valve with the driven sprocket to be provided, whereby the size of the cylinder head can be reduced.

  According to the fourth aspect of the present invention, the valve operating device drives the exhaust valve so as to swing following the camshaft disposed above the intake valve and the exhaust cam provided on the camshaft. The angle formed by the operation axes of the intake valve and the exhaust valve can be set small in a projection view on a plane orthogonal to the axis of the crankshaft, and the rotary valve can be rotated. Since the axis is set substantially parallel to the axis of the cylinder bore, the engine body can be made compact in a direction perpendicular to the axis of the cylinder bore and crankshaft.

  According to the fifth aspect of the present invention, the rotary valve is disposed in the straight portion of the exhaust port, so that the rotary valve is simplified to facilitate the processing of the rotary valve and exhaust by the rotary valve. Controllability can be improved.

  According to the sixth aspect of the present invention, the valve housing opened upward so that the rotary valve can be assembled from above is provided integrally with the cylinder head so as to rotatably accommodate the rotary valve. Since the upper end surface of the valve housing is formed flush with the coupling surface of the cylinder head to the head cover, the workability of the valve housing can be improved and the rotary valve can be easily assembled.

  According to the seventh aspect of the present invention, the rotary valve is rotatably disposed on the cylinder head on the opposite side of the center of the exhaust port from the frame member that forms a part of the vehicle body frame. And interference of the frame member can be avoided.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 7 show a first embodiment of the present invention. FIG. 1 is a right side view of a main part of a motorcycle, and FIG. 2 is a vertical left side view of a four-cycle engine. FIG. 3 is an enlarged sectional view taken along line 3-3 of FIG. 2, FIG. 4 is a sectional view taken along line 4-4 of FIG. 3, and FIG. 5 is a fully opened (a) and fully closed position of the rotary valve. FIG. 6 is a cross-sectional view showing the state of (b) along line 5-5 in FIG. 4, FIG. 6 is a block diagram showing a control system of the rotary valve, and FIG. 7 is a diagram showing a change in output accompanying a change in the opening of the rotary valve. is there.

  1, a motorcycle body frame F, which is a small vehicle, includes a head pipe 15 at its front end, a pair of left and right main frames 16 extending rearwardly downward from the head pipe 15, and the main frames 16. A pair of left and right pivot plates 17 connected to the rear and extending downward, a down frame 18 extending downward from the head pipe 15, and a pair of left and right connecting the lower end of the down frame 18 and the pivot plates 17. A four-cycle water-cooled single cylinder engine body 24A is surrounded by the main frame 16, the pivot plate 17, the down frame 18 and the lower frame 19 ... It is supported by the vehicle body frame F so as to be arranged in a space. Further, radiators 25... Divided into left and right sides of the down frame 18 are arranged in front of the engine main body 24 </ b> A, and these radiators 25 are supported by the down frame 18.

  Referring also to FIG. 2, the engine body 24A includes a crankcase 27 that uses a crankshaft 26 that has an axis extending in the left-right direction of the motorcycle, and a cylinder bore 28. A cylinder block 29 coupled to the upper part, a cylinder head 30A coupled to the upper part of the cylinder block 29, and a head cover 31 coupled to the upper part of the cylinder head 30A are provided. Moreover, when the engine body 24A is mounted on the vehicle body frame F, the cylinder block 29 is coupled to the crankcase 27 so that the axis CB of the cylinder bore 28 is slightly inclined upward.

  A piston 32 is slidably fitted to the cylinder bore 28, and the piston 32 is connected to the crankshaft 26 via a connecting rod 33. A combustion chamber 34 is formed between the cylinder block 29 and the cylinder head 30A so that the top of the piston 32 faces.

  By the way, the crankshaft 26 rotates in the rotational direction indicated by the arrow 35 in accordance with the reciprocating sliding of the piston 32 in the cylinder bore 28. The axis CB of the cylinder bore 28 is more than the axis CC of the crankshaft 26. By setting the axis CB of the cylinder bore 28 to be offset with respect to the axis CC of the crankshaft 26 in this way, the piston 32 on the inner surface of the cylinder bore 28 is set. Wear due to sliding contact can be suppressed, and the cylinder block 29 and the combustion chamber 34 can be prevented from becoming high temperature due to the wear.

  The cylinder head 30A is provided with a pair of intake valve ports 36 and a pair of exhaust valve ports 37 facing the combustion chamber 34. A pair of intake valves 38 that individually open and close the intake valve ports 36 and a pair of exhaust valves 39 that individually open and close the exhaust valve ports 37 are disposed in the cylinder head 30A so as to be openable and closable. The two intake valves 38 are energized in the valve closing direction by the valve springs 40, and the exhaust valves 39 are energized in the valve closing direction by the valve springs 41, respectively.

  With further reference to FIG. 3, a valve operating device 44 for opening and closing the intake valves 38 and the exhaust valves 39 is accommodated between the cylinder head 30A and the head cover 31. The valve operating device 44 has an axis parallel to the crankshaft 26 and is disposed above the intake valves 38 and is rotatably supported by the cylinder head 30A, and the camshaft. , And a pair of valve lifters 46 interposed between the intake valves 38 and a pair of exhaust side cams 49 provided on the camshaft 45, respectively. Thus, the exhaust valve 39 is paired with a pair of rocker arms 47 that open and close to form an SOHC type.

  The valve lifters 46 are formed in a bottomed cylindrical shape with the upper end as a closed end, and are fitted into the cylinder head 30A so as to slide in the axial direction coaxial with the operation axis of the intake valves 38. The The upper ends of the stems 38a of the intake valves 38 are in contact with the inner surfaces of the closed ends of the valve lifters 46, and the intake cams 48 are in contact with the outer surfaces of the closed ends of the valve lifters 46. A plug insertion cylinder 50 is attached to the cylinder head 30A by inserting a spark plug (not shown) that is screwed into the cylinder head 30A so that the front end faces the combustion chamber 34. The plug insertion cylinder 50 is attached to the cylinder head 30A. The two rocker arms 47 arranged on both sides of the camshaft 45 are rotatably supported by a rocker shaft 51 having an axis parallel to the camshaft 45 and supported by the cylinder head 30A. Moreover, rollers 52 which are in rolling contact with the exhaust side cams 49 are respectively pivotally supported at one end portions of the rocker arms 47, and the other end portions of the rocker arms 47 are the stems 39a of the exhaust valves 39. It is contact | abutted at an upper end, respectively.

  In such a SOHC type valve gear 44, the angle α formed by the operation axes of the intake valves 38 and the exhaust valves 39 is set to be relatively small on the projection onto the plane orthogonal to the axis of the crankshaft 26. It is possible to reduce the size of the cylinder head 30A by arranging the intake valves 38 and the exhaust valves 39 closer to each other.

  The rotational power of the crankshaft 26 is transmitted by the timing transmission mechanism 53 at a reduction ratio of 1/2 to one end of the camshaft 45, which is the left end when the engine body 24A is mounted on the vehicle body frame F. The timing transmission mechanism 53 includes a drive sprocket (not shown) provided on the crankshaft 26 and a driven sprocket 55 fixed to one end of the camshaft 45. Wrapped around. In addition, the cylinder block 29 and the cylinder head 30A are provided with a cam chain chamber 57 for running the cam chain 56. The cam chain chamber 57 is mounted on the vehicle body frame F of the engine body 24A. 29 and the left end of the cylinder head 30A.

  The cylinder head 30A is provided with a single intake port 58 that communicates in common with the intake valve ports 36, and forms a part of the intake port 58 so as to be rearward from the rear side surface of the cylinder head 30A. An intake side connection pipe portion 59 provided integrally with the cylinder head 30A so as to project is formed with an intake passage 60 communicating with the intake port 58, and a throttle body 61 disposed behind the cylinder head 30A has an insulator. 62 is connected. A throttle valve 63 that changes the opening area of the intake passage 60 is rotatably supported on the throttle body 61, and a fuel injection valve 64 that injects fuel toward the intake port 58 is attached to the throttle body 61.

  Further, the cylinder head 30A is provided with a single exhaust port 65 that communicates in common with the exhaust valve ports 37, and a part of the exhaust port 65 is formed so that the front side surface of the cylinder head 30A is forward. An exhaust-side connecting pipe portion 66 that protrudes into the cylinder head 30A is integrally provided. An exhaust pipe 68 is connected to the exhaust side connection pipe portion 66 so as to form an exhaust passage 67 including the exhaust port 65, and the exhaust port 65 passes through the upstream end. The exhaust muffler 69 (see FIG. 1) is connected. Thus, a part of the cylinder head 30A integrally having the exhaust side connecting pipe portion 66 and the exhaust pipe 68 constitute an exhaust passage forming means 70 that cooperates to form an exhaust passage 67.

  The exhaust side connecting pipe portion 66 has a straight portion 65aa in part, but is integrally connected to the cylinder head 30A so that a part of the exhaust port 65 forms a bent portion 65a as a whole. The bent portion 65a is bent in the horizontal direction so as to protrude in the right direction in this embodiment in the left-right direction of the motorcycle when the engine body 24A is mounted on the vehicle body frame F. The exhaust-side connecting pipe portion 66 is formed so as to bend to the left behind the down frame 18 so as to avoid the down frame 18 and is integrally connected to the cylinder head 30A.

  The upstream end of the exhaust pipe 68 is connected to the exhaust side connection pipe section 66. The exhaust pipe 68 is formed in the exhaust side connection pipe section 66 as shown in FIG. A hanging tube portion 68a that extends slightly to the left in the extending direction and then extends downward so as to wrap around the front of the down frame 18, and is bent to the right from the lower end of the hanging tube portion 68a and extends obliquely upward to the right. A first ascending pipe portion 68b and a second ascending pipe portion 68c that bends leftward from the rear end of the first ascending pipe portion 68b and extends rearward as it slightly rises toward the center in the width direction of the vehicle body frame F. .

  Referring also to FIG. 4, the curved cross-sectional area of the curved portion 65 a formed by a curved portion, that is, a part of the exhaust port 65, which is disposed at a position closest to the exhaust valve port 37. The rotary valve 71 is an exhaust control valve. The rotary valve 71 is disposed in the straight portion 65aa of the bent portion 65a.

  The rotary valve 71 is configured to change a partial passage cross-sectional area inside the bent portion 65a by projecting a part from the inner wall of the exhaust port 65 in the exhaust passage 67 into the exhaust port 65 when the rotary valve 71 is closed. Is disposed on the exhaust side connecting pipe portion 66 of the cylinder head 30A and is offset from the center CL of the bent portion 65a toward the inside of the curve, in this embodiment, from the center CL of the exhaust port 65, the cam. A rotary valve 71 having an axis of rotation CR that is offset to the chain chamber 57 side and is oriented in the vertical direction substantially parallel to the axis CB of the cylinder bore 28 at a position opposite to the down frame 18 with respect to the center CL is provided on the exhaust side connecting pipe portion. 66.

  When the rotary valve 71 is fully opened as shown in FIGS. 4 and 5A, a part of the exhaust port 65 in the exhaust passage 67 is formed on a valve main body 72 having a cylindrical outer surface centered on the rotation axis CR. The valve body 72 is formed so as to cut out a part of the valve main body 72. At both ends of the valve main body 72, rotation shaft parts 72a and 72b that are coaxial with the rotation axis CR are formed. Projecting coaxially and integrally. When the rotary valve 71 is closed, the outer surface of the rotary valve 71, that is, a part of the outer surface of the valve main body 72 protrudes from the inner wall of the exhaust port 65 in the exhaust passage 67, as shown in FIG. . Moreover, since the valve main body 72 is cylindrical, the outer surface of the rotary valve 71 in the closed state protrudes into the exhaust passage 67 and faces the upstream side at least from the inner wall protruding from the inner wall. Then, since the rotation axis CR of the rotary valve 71 is located at a position crossing the exhaust passage 67, the protruding front end side outer surface of the rotary valve 71 that protrudes into the exhaust passage 67 and faces the upstream side is projected from the inner wall. Is gradually increased from the upstream side of the exhaust passage 67 toward the downstream side, and the portion facing the upstream side of the protruding tip side is bent in the same direction as the bending direction of the exhaust port 65 in the exhaust passage 67. .

  The rotary valve 71 is accommodated in a valve housing 74 that is provided integrally with an exhaust-side connecting pipe portion 66 that is integral with the cylinder head 30A. The valve housing 74 includes an accommodating portion 74a that accommodates the valve main body 72 in a rotatable manner, and a box-shaped portion 74b that is integrally connected to an upper portion of the accommodating portion 74a. It is formed in a rectangular shape extending from the portion 74a to the opposite side to the cam chain chamber 57 and having an upper portion opened.

  The housing portion 74a is formed with a housing hole 75 that crosses the straight portion 65aa of the bent portion 65a of the exhaust port 65 at a portion near the cam chain chamber 56, and a smaller diameter than the housing hole 75. A bottomed lower support hole 76 that is coaxially connected to the hole 75 is provided, and an annular lower support surface 77 that faces upward is formed between the accommodation hole 75 and the lower support hole 76. The upper end of the accommodating hole 75 is opened in a flat coupling surface 78 formed at the upper end of the accommodating portion 74 a so as to face the box-shaped portion 74 b, and the coupling surface 78 has a valve main body of the rotary valve 71. A holding member 79 that sandwiches 72 between the lower support surface 77 and the lower support surface 77 is coupled by a plurality of bolts 80, 80, for example.

  That is, the valve main body 72 is inserted into the receiving hole 75 from above so that the rotation shaft portion 72a is rotatably fitted in the lower support hole 76, and holds the valve main body 72 from above. In this way, the pressing member 79 is fastened to the coupling surface 78. In addition, the holding member 79 is provided with an upper support hole 81 through which the rotation shaft portion 72b of the valve main body 72 is pivotably passed. An annular seal is provided between the holding member 79 and the rotation shaft portion 72b. A member 82 is interposed.

  A return spring 83 is provided between the rotary shaft portion 72 b and the pressing member 79 of the rotary valve 71, and the rotary shaft portion 72 b, that is, the rotary valve 71 is opened by the spring force of the return spring 83, that is, As shown in FIG. 5, the passage portion 73 is biased to the rotational position side that is flush with the inner surface of the exhaust port 65.

  The upper end surface of the valve housing 74, that is, the upper end surface of the box-shaped portion 74b is formed so as to be flush with the coupling surface 84 to the head cover 31 of the cylinder head 30A. A lid member 86 that forms an operation chamber 85 is fastened between the valve housing 74 and the valve housing 74.

  In the working chamber 85, a drum 87 is fixed to a rotating shaft portion 72b of the rotary valve 71, and a closed side cable 88 for rotating the rotary valve 71 to the closing side when towing is attached to the drum 87. And one end of an open-side cable 89 that rotates the rotary valve 71 to the valve-opening side when towed are wound around and engaged with each other.

  The closing cable 88 and the opening cable 89 are formed by inserting inner cables 88b and 89b movably through the outer cables 88a and 89a, and one end portions of the outer cables 88a and 89a are separated from the drum 87. Thus, one end of the inner cables 88b and 89b fixed to the side wall of the box-shaped portion 74b and projecting from one end of the outer cables 88a and 89a is connected to the drum 87.

  On the other hand, the other ends of the closing side cable 88 and the opening side cable 89 are connected to an actuator 90 having a forward and reverse electric motor and supported by the vehicle body frame F. By the actuator 90, the closing side cable 88 is connected. By pulling 88, the rotary valve 71 rotates in the valve closing direction, and by pulling the opening-side casing 89, the rotary valve 71 rotates in the valve opening side.

  By the way, on the front side surface of the cylinder head 30A, water for guiding cooling water from the water jacket 91 provided on the cylinder block 29 and the cylinder head 30A to the radiator 25. An outlet 92 is provided, and the water outlet 92 is disposed on the side opposite to the cam chain chamber 57 with respect to the exhaust port 65.

  In FIG. 1, a water pump 94 driven by power transmitted from the crankshaft 26 is attached to the outer surface of the right cover 93 fastened to the right side surface of the crankcase 27. Is connected to a pipe 95 for guiding cooling water from the lower part of the radiator 25. On the other hand, the cooling water discharged from the water pump 94 is introduced into the lower part of the water jacket 91 through the right cover 93, the crankcase 27 and the cylinder block 29, and is connected to the upper part of the water jacket 91. The water outlet 92 provided in the cylinder head 30 </ b> A and the upper portions of the radiators 25 are connected via a pipe 96.

  In FIG. 6, the operation of the actuator 90 is controlled by a control unit 98, and the control unit 98 includes an engine speed NE detected by an engine speed detector 99 and a gear position detector 100. The detected gear position GP of the transmission is input, and the control unit 98 controls the operation of the actuator 90 to open and close the rotary valve 71 based on the engine speed NE and the gear position GP. It should be noted that the throttle opening may be used instead of the engine speed NE, or both the engine speed NE and the throttle opening may be used.

  Thus, the control unit 98 fully opens the rotary valve 71 during high-speed operation of the engine, and closes more than half (for example, 57%) of the cross-sectional area of the exhaust port 65 in the exhaust passage 67 during medium-low speed operation of the engine. The actuator 90 is controlled to be in a fully closed state.

  The control unit 98 determines whether or not the motorcycle is decelerating based on at least one of the engine speed NE and the throttle opening and the gear position. When it is determined that the motorcycle is decelerating, the engine brake is applied. Accordingly, the actuator 90 is operated so as to close the rotary valve 71.

  Further, the control unit 98 determines whether or not the motorcycle is suddenly accelerating based on at least one of the engine speed NE and the throttle opening and the gear position. The actuator 91 is operated so as to temporarily close the rotary valve 71 in order to create an output reservoir.

  Next, the operation of the first embodiment will be described. Of the exhaust passage 67 formed by the exhaust passage formation means 70, the cross-sectional area of the curved portion at the curved portion 65a of the exhaust port 65 closest to the exhaust valve port 37. Among them, the partial passage cross-sectional area inside the curve is changed by the rotary valve 71, so that the rotary valve 71 is arranged at a portion where the exhaust flow velocity is close to the combustion chamber 34 and is fast even inside the curve. The exhaust control effect can be maximized without increasing the size of 71. Further, when the rotary valve 71 is closed, the exhaust gas flows only in the curved portion 65a where the exhaust gas flow velocity is fast, so that good exhaust control is possible. Further, the rotary valve 71 is disposed at a position close to the combustion chamber 34, and the pressure control in the combustion chamber 34 by the rotary valve 71 and the opening timing of the exhaust valves 39 and the intake valves 38 are overlapped. Blow-through can be suppressed.

  In addition, the bent portion 65a of the exhaust port 65 has a straight portion 65aa extending in a straight line at a part thereof, and the rotary valve 71 is disposed on the straight portion 65aa, thereby simplifying the shape of the rotary valve 71. Thus, processing of the rotary valve 71 can be facilitated and exhaust control by the rotary valve 71 can be improved.

  Further, the rotary valve 71 is flush with the inner surface of the exhaust port 65 in the exhaust passage 67 when fully opened, and the outer surface is gently connected with the inner surface of the exhaust port 65 upstream of the rotary valve 71 when the valve is closed. Therefore, when the rotary valve 71 is fully opened, the rotary valve 71 does not reduce the cross-sectional area of the exhaust port 65 in the exhaust passage 67. A control unit 98 that controls an actuator 90 that opens and closes the rotary valve 71 opens the rotary valve 71 when the engine is operating at a high speed, and the passage cross-sectional area of the exhaust port 65 in the exhaust passage 67 when the engine is operating at a medium and low speed. The actuator 90 is controlled so that more than half (for example, 57%) of the actuator is in a fully closed state.

  Here, when the exhaust port 65 is in a fully open state, and when the exhaust port 65 is in a fully closed state in which more than half (for example, 57%) of the passage cross-sectional area of the exhaust port 65 is closed, the engine output changes in the operating state of the engine. As shown in FIG. 7, the exhaust gas from the combustion chamber 34 is better discharged without reducing the cross-sectional area of the exhaust port 65 in the exhaust exhaust passage 67 during high-speed operation. Combustion efficiency can be improved by introducing fresh air effectively, and the pressure in the combustion chamber 34 can be increased while slowing the discharge of the exhaust from the combustion chamber 34 and preventing the blow-off of fresh air during medium and low speed operation. The engine output can be improved by increasing the engine output.

  Since the control unit 98 controls the operation of the actuator 90 to open and close the rotary valve 71 based on at least one of the engine speed NE and the throttle opening and the gear position, the control unit 98 represents the state of the combustion chamber 34. The optimal opening / closing control of the rotary valve 71 can be performed in accordance with at least one of the index, that is, the throttle opening degree and the engine speed NE, and the gear position of the transmission.

  Further, the control unit 98 determines whether or not the motorcycle is decelerating, and when it determines that the motorcycle is decelerating, the actuator 90 is operated so as to close the rotary valve 71 so as to apply the engine brake. The engine brake can be applied at the time of deceleration by the rotary valve 71.

  Further, the control unit 98 determines whether or not the motorcycle is suddenly accelerating, and when it is determined that the motorcycle is suddenly accelerating, the actuator 90 is operated so as to temporarily close the rotary valve 71 so as to create a reservoir for engine output. Therefore, the rotary valve 71 can be temporarily closed at the time of rapid acceleration, and the output can be temporarily reduced without impairing the acceleration operation feeling, so that the wheel grip can be improved.

  Incidentally, the rotary valve 71 has a rotation axis CR at a position offset from the center Cl of the exhaust port 65 so that a part of the rotary valve 71 projects into the exhaust port 65 from the inner wall of the exhaust port 65 when the valve is closed. In addition, even when the rotary valve 71 is closed, the opening area of the exhaust port 65 can be made relatively large. In addition, the outer surface of the rotary valve 71 in the closed state that protrudes into the exhaust passage 67 and faces the upstream side protrudes at least from the inner wall of the projecting tip side, in this embodiment, the outer surface of the projecting tip side projects from the inner wall. The amount gradually increases from the upstream side of the exhaust passage 67 toward the downstream side, and the portion facing the upstream side on the protruding tip side is bent in the same direction as the bending direction of the exhaust port 65 in the exhaust passage 67. Therefore, even when the exhaust gas flow rate is high, the exhaust gas is smoothly circulated along the surface of the rotary valve 71 as shown by the arrow in FIG. Good exhaust control by opening and closing the valve 71 can be realized.

  Further, the rotary valve 71 has a valve body 72 having a cylindrical outer surface shape centered on the rotation axis CR, and a passage portion 73 that constitutes a part of the exhaust port 65 when the valve is fully opened. It is formed by notching and the workability of the rotary valve 71 can be improved.

  Further, the rotary valve 71 can change the opening area of the exhaust port 65 provided in the cylinder head 30A, and is offset from the center CL of the exhaust port 65 toward the cam chain chamber 57 side. Since the rotary valve 71 that is relatively heavy is disposed in the cylinder head 30A, the rotary valve 71 is disposed on the side near the cam chain chamber 57 that is a cavity. Since it is disposed in the cylinder head 30A, the weight balance of the engine body 24A can be set appropriately.

  Further, the rotary valve 71 is rotatably disposed on the exhaust side connection pipe portion 66 of the cylinder head 30A on the opposite side of the center CL of the exhaust port 65 from the down frame 18, so that the rotary valve 71 and the down frame 18 Interference can be avoided.

  Further, a water outlet 92 for guiding cooling water from the cylinder head 30A to the radiator 25. Since it is provided on the side surface, the rotary valve 71 can be arranged so as not to interfere with the pipe 96 connected to the water outlet 92.

  By the way, in the valve gear 44 that opens and closes the intake valves 38... And the exhaust valves 39..., The exhaust cams 49 provided on the camshaft 45 disposed above the intake valves 38. It is linked to and connected to the exhaust valve 39 through rocker arms 47 that swing when driven, and such a valve operating device 44 is an intake valve on a plan view orthogonal to the axis of the crankshaft 26. 38 and the exhaust valve 39 can be set to be relatively small in angle α, and the intake valve 38 and the exhaust valve 39 are arranged closer to each other to reduce the size of the cylinder head 30A. However, since the rotation axis CR of the rotary valve 71 is set substantially parallel to the axis CB of the cylinder bore 28 in the cylinder block 29, the cylinder bore 28 and the cylinder It can be made compact engine body 24A in a direction orthogonal to the axis of the link shaft 26.

  Moreover, the rotary valve 71 is rotatably accommodated in a valve housing 74 that is integrally provided in the exhaust side connecting pipe portion 66 that is integral with the cylinder head 30A. Therefore, a valve housing that accommodates the rotary valve 71 is specially prepared. Is unnecessary, and the number of parts can be reduced.

  When the engine body 24A is mounted on the vehicle body frame F, the exhaust-side connecting pipe portion 66 is formed such that a part of the exhaust port 65 forms a bent portion 65a that bulges rightward and curves horizontally in the motorcycle. Since the rotary valve 71 is accommodated in the valve housing 74 with its rotation axis CR oriented in the vertical direction, the cylinder head 30A of the valve housing 74 is connected to the cylinder head 30A. It is possible to prevent the rotation shaft portions 72a and 72b of the rotary valve 71 from separating from the combustion chamber 34 and to prevent the rotation shaft portions 72a and 72b from reaching a high temperature. Further, the drum 87, which is a drive mechanism for driving the rotary valve 71, the closing side cable 88, the opening side cable 89, and the like are arranged on the upper portion of the valve housing 74, whereby the drum 87, the closing side cable 88 and the opening side cable 89 are arranged. Etc. can be easily protected from stepping stones from below.

  Further, the valve housing 74 is provided integrally with the outside-side connecting pipe portion 66 integral with the cylinder head 30A so that the rotary valve 71 can be assembled from above and is opened upward. However, since the cylinder head 30A is formed flush with the coupling surface 84 of the cylinder head 30A to the head cover 31, the workability of the valve housing 74 is improved and the assembly of the rotary valve 71 of the valve housing 74 is facilitated. Can do.

  Further, the engine main body 24A is configured such that the axis CB of the cylinder bore 28 is offset from the axis CC of the crankshaft 26 in the rotational direction 35 of the crankshaft 26, so that the piston to the inner surface of the cylinder bore 28 is arranged. The friction caused by the sliding contact of 32 can be suppressed, the temperature of the cylinder block 29 and the combustion chamber 34 can be prevented from becoming higher, and the thermal effect on the rotary valve 71 disposed in the exhaust port 65 can be reduced. it can.

  FIG. 8 shows a second embodiment of the present invention, which is a cross-sectional view corresponding to FIG. 3, in which parts corresponding to the first embodiment are shown with the same reference numerals and illustrated. Detailed description is omitted.

  The cylinder head 30B of the engine body 24B is provided with a single exhaust port 116 that communicates in common with the exhaust valve port 37 (see the first embodiment). A cylinder is formed by forming a part of the exhaust port 116. An exhaust-side connecting pipe portion 117 protruding forward from the front side surface of the head 30B is provided integrally with the cylinder head 30B. An exhaust pipe 119 is connected to the exhaust side connecting pipe portion 117 so as to form an exhaust passage 118 including the exhaust port 116 and to let the exhaust port 116 pass through an upstream end. Thus, a part of the cylinder head 30B integrally having the exhaust side connecting pipe portion 117 and the exhaust pipe 119 constitute an exhaust passage forming means 120 that cooperates to form the exhaust passage 118.

  The exhaust side connecting pipe part 117 has a straight part 116aa in part, but is integrally connected to the cylinder head 30B so that a part of the exhaust port 116 forms a bent part 116a as a whole. The bent portion 116a is bent in the horizontal direction so as to protrude in the left direction in this embodiment in the left-right direction of the motorcycle when the engine body 24B is mounted on the vehicle body frame F. The exhaust side connecting pipe portion 117 is formed so as to be bent to the right at the rear of the down frame 18 so as to avoid the down frame 18, and is integrally connected to the cylinder head 30B.

  A curved cross-sectional area of the curved portion 116a formed by a curved portion disposed at a position closest to the exhaust valve port 37 in the exhaust passage 118, that is, a portion of the exhaust port 116, is a rotary valve 71 which is an exhaust control valve. The rotary valve 71 is disposed on the straight portion 116aa of the bent portion 116a.

  The rotary valve 71 is configured to change a partial passage cross-sectional area inside the bent portion 116 by projecting a part from the inner wall of the exhaust port 116 in the exhaust passage 118 into the exhaust port 116 when the rotary valve 71 is closed. Is disposed on the exhaust side connecting pipe portion 117 of the cylinder head 30B and is offset from the center CL of the bent portion 116a toward the inside of the curve, in this embodiment, from the center CL of the exhaust port 116 to the cam chain. A rotary valve 71 having a rotational axis CR that is offset to the opposite side to the chamber 57 and oriented in the vertical direction at a position opposite to the down frame 18 with respect to the center CL is disposed in the exhaust side connecting pipe 117. .

  The rotary valve 71 is accommodated in a valve housing 74 that is provided integrally with the exhaust-side connecting pipe portion 117 that is integral with the cylinder head 30B. The valve housing 74 is configured to extend toward the cam chain chamber 57 opposite to the first embodiment, but has basically the same structure as the valve housing 74 of the first embodiment. Therefore, the same reference numerals are assigned to the portions corresponding to the first embodiment, and the detailed description is omitted.

  According to the second embodiment, since the rotary valve 71 is disposed in the exhaust port 116, the passage sectional area of the exhaust port 116 does not decrease when the rotary valve 71 is fully opened, and a relatively large rotary valve 71 is provided. The rotary valve 71 is disposed in the exhaust side connection pipe 117 at a position offset from the center CL of the exhaust port 116 to the opposite side of the cam chain chamber 57 even if it is disposed in the exhaust side connection pipe 117 of the cylinder head 30B. Therefore, it is easy to avoid the interference of the rotary valve 71 with the driven sprocket 55 provided on the camshaft 45 so as to constitute a part of the timing transmission mechanism 53, thereby reducing the size of the cylinder head 30B. Can be achieved. Further, the rotary valve 71 is rotatably disposed on the exhaust side connecting pipe portion 117 of the cylinder head 30B on the opposite side of the down frame 18 with respect to the center CL of the exhaust port 116, so that the rotary valve 71 and the down frame 18 Interference can be avoided.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

1 is a right side view of a main part of a motorcycle according to a first embodiment. FIG. 4 is a longitudinal left side view of the 4-cycle engine, and is a longitudinal side view taken along line 2-2 in FIG. 3. FIG. 3 is an enlarged sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. It is sectional drawing which shows the state at the time of full opening (a) and a full closure (b) of a rotary valve along the 5-5 line | wire of FIG. It is a block diagram which shows the control system of a rotary valve. It is a figure which shows the output change accompanying the opening degree change of a rotary valve. It is sectional drawing corresponding to FIG. 3 of 2nd Example.

Explanation of symbols

18 ... Down frame 24A as a frame member ... Engine body 25 ... Radiator 26 ... Crankshaft 28 ... Cylinder bore 29 ... Cylinder block 30A, 30B ... Cylinder head 32 ... Piston 34 ... Combustion chamber 36 ... Intake valve port 37 ... Exhaust valve port 38 ... Intake valve 39 ... Exhaust valve 44 ... Valve operating device 45 ... Camshaft 53 ... Timing transmission mechanism 56 ... cam chain 57 ... cam chain chambers 65, 110 ... exhaust ports 65aa, 110aa ... straight part 71 ... rotary valve 74 ... valve housing 84 ... coupling Surface 92 ... Water outlet CL ... Center of exhaust port F ... Body frame

Claims (7)

  A cylinder head (30A) coupled to the cylinder block (29) has a combustion chamber (34) facing the top of a piston (32) slidably fitted in a cylinder bore (28) of the cylinder block (29). ) And the cylinder block (29), and the intake valve port (36) and the exhaust valve port (37) provided in the cylinder head (30A, 30B) facing the combustion chamber (34) can be opened and closed, respectively. An intake valve (38) and an exhaust valve (39) are disposed in the cylinder head (30A) so as to be openable and closable, and are operated to open and close the intake valve (38) and the exhaust valve (39). A timing transmission mechanism (53) having an endless cam chain (56) between one end of the camshaft (45) and the crankshaft (26), In the 4-cycle engine in which the cam chain chamber (57) for running the cam chain (53) is formed in the cylinder block (29) and the cylinder head (30A, 30B), it is connected to the exhaust valve port (37). A rotary valve (71) capable of changing the opening area of the exhaust port (65) provided in the cylinder head (30A) is offset from the center (CL) of the exhaust port (65) toward the cam chain chamber (57). An exhaust control device for a four-cycle engine, wherein the exhaust control device is rotatably disposed on the cylinder head (30A) at the position where the engine is operated.   An engine main body (24A) configured to be water-cooled with the cylinder block (29) and the cylinder head (30A) as a part of components, and a radiator (25) disposed in front of the engine main body (24A) Is mounted on a body frame (F) of a motorcycle, and a water outlet (92) for guiding cooling water from the cylinder head (30A) to the radiator (25) side and the exhaust port (65) are provided on the exhaust port. The port (65) is provided on the front side surface of the cylinder head (30A) so as to dispose the water outlet (92) on the opposite side of the cam chain chamber (57). An exhaust control device for a four-cycle engine as described.   A cylinder head (30B) coupled to the cylinder block (29) has a combustion chamber (34) facing the top of a piston (32) slidably fitted in a cylinder bore (28) of the cylinder block (29). ) And the cylinder block (29), the intake valve port (36) and the exhaust valve port (37) provided in the cylinder head (30B) facing the combustion chamber (34) can be opened and closed, respectively. (38) and an exhaust valve (39) are disposed in the cylinder head (30B) so as to be openable and closable, and a valve operating device (44) for opening and closing the intake valve (38) and the exhaust valve (39) is provided. A timing transmission mechanism (53) having an endless cam chain (56) is provided between one end of the camshaft (45) and the crankshaft (26). In an exhaust control device for a four-cycle engine in which a cam chain chamber (57) for running the cam chain (56) is formed in the dublock (29) and the cylinder head (30B), it is connected to the exhaust valve port (37). The rotary valve (71) that can change the opening area of the exhaust port (110) provided in the cylinder head (30B) is defined by the cam chain chamber (57) from the center (CL) of the exhaust port (110). An exhaust control device for a four-cycle engine, wherein the exhaust control device is rotatably arranged on the cylinder head (30B) at a position offset to the opposite side.   An exhaust cam (49) provided on the camshaft (45) disposed above the intake valve (38) is connected via a rocker arm (47) that is oscillated by the exhaust cam (49). The interlocking and coupling with the exhaust valve (39), wherein the rotational axis of the rotary valve (71) is set substantially parallel to the axis of the cylinder bore (28). An exhaust control device for a four-cycle engine according to 1.   The exhaust port (65, 110) has a straight portion (65aa, 110aa) extending in a straight line and is provided in the cylinder head (30A, 30B), and the rotary valve (71) is connected to the straight port. The exhaust control device for a four-cycle engine according to any one of claims 1 to 4, wherein the exhaust control device is disposed in a portion (65aa, 110aa).   A valve housing (74) that accommodates the rotary valve (71) in a pivotable manner allows the rotary valve (71) to be assembled from above and opens upward to be integrated with the cylinder head (30A, 30B). The upper end surface of the valve housing (74) is formed flush with the coupling surface to the head cover (31) of the cylinder head (30A, 30B). An exhaust control device for a four-cycle engine according to claim 1.   The exhaust ports (65, 110) are provided in the cylinder heads (30A, 30B) so as to face the side of a frame member (18) that constitutes a part of the body frame (F) of the motorcycle and extends vertically, and the rotary A valve (71) is rotatably disposed on the cylinder head (30A, 30B) on the opposite side of the frame member (18) with respect to the center (CL) of the exhaust port (65, 110). The exhaust control device for a four-cycle engine according to any one of claims 1 to 6.

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