Upper structure of engine

Abstract

To restrain upsizing of a cylinder head cover and install a reed valve in an appropriate place.SOLUTION: Secondary air is supplied to an exhaust port of an engine (20). A cylinder head (23) in which an exhaust cam shaft (56) and an intake cam shaft (57) are installed, a cylinder head cover (24) which is fixed onto the cylinder head by fastening members (69a to 69c), a reed valve which prevents a backward flow of exhaust gas from the exhaust port to an upstream side, and an ignition plug (59) which is positioned between the intake cam shaft and the exhaust cam shaft are provided in an upper structure of the engine. A housing section (74) which houses the reed valve is provided adjacently to the ignition plug in an upper portion of the exhaust cam shaft in the cylinder head cover. A supply passage (64) for introducing secondary air to the exhaust port from the housing section is formed in a side opposite to the ignition plug while sandwiching the exhaust cam shaft in the cylinder head cover.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an engine upper structure. [Background technology]

[0002] In order to reduce air pollutants, engines are equipped with a secondary air supply device that supplies secondary air to the exhaust port to reburn unburned gas in the exhaust gas. The secondary air supply device is provided with an air control device that controls the supply of secondary air from the air cleaner to the exhaust port, as well as a reed valve that prevents exhaust gas from flowing back from the exhaust port to the air cleaner. As an engine equipped with this type of secondary air supply device, a DOHC engine with a reed valve installed on the top surface of the cylinder head cover has been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4284997 Summary of the Invention [Problem to be solved by the invention]

[0004] In a DOHC engine, a spark plug is provided between a pair of camshafts, and the cylinder head cover fastening bolts are arranged around the spark plug. In order to install the reed valve to avoid the spark plug and fastening bolts, the cylinder head cover must be made taller or wider. This makes the engine larger, which affects the layout of the surrounding parts such as the fuel tank. Depending on the location of the reed valve, the supply of secondary air to the exhaust port may be impaired, which may reduce the purification performance of the exhaust gas.

[0005] The present invention has been made in consideration of the above-mentioned points, and has an object to provide an upper structure of an engine that can install a reed valve in an appropriate location while preventing the cylinder head cover from becoming larger. [Means for solving the problem]

[0006] The upper structure of an engine of one embodiment of the present invention is an upper structure of an engine in which secondary air is supplied to an exhaust port of the engine, and comprises a cylinder head on which an exhaust camshaft and an intake camshaft are installed, a cylinder head cover fixed onto the cylinder head with fastening members, a reed valve that prevents backflow of exhaust gas from the exhaust port to the upstream side, and an ignition plug located between the intake camshaft and the exhaust camshaft, wherein a storage portion for accommodating the reed valve is provided in the cylinder head cover above the exhaust camshaft and next to the spark plug, and a supply passage for introducing secondary air from the storage portion to the exhaust port is formed on the opposite side of the spark plug in the cylinder head cover across the exhaust camshaft, thereby solving the above-mentioned problem. Effect of the Invention

[0007] According to the engine upper structure of one aspect of the present invention, the reed valve does not interfere with the ignition plug on the cylinder head cover. Also, in order to ensure the sealing between the cylinder head cover and the cylinder head, the fastening members are usually positioned at multiple locations away from the ignition plug, but by locating the reed valve next to the ignition plug, the reed valve does not interfere with the fastening members. The size of the cylinder head cover is suppressed, and the impact on the layout of the surrounding parts can be suppressed. A reed valve accommodating portion is provided above the exhaust camshaft, and a supply passage is formed on the opposite side of the exhaust camshaft from the ignition plug, so that the supply passage can be shortened without changing the arrangement of the exhaust camshaft and the ignition plug. The pressure loss of the secondary air in the supply passage can be suppressed, and the purification performance of the exhaust gas can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a right side view of the saddle-type vehicle of the present embodiment. [Diagram 2] FIG. 2 is a right side view of the engine and its periphery according to the present embodiment. [Diagram 3] FIG. 2 is a front view of the upper part of the engine according to the embodiment. [Figure 4] FIG. 2 is a top view of the upper part of the engine according to the embodiment. [Diagram 5] FIG. 4 is a cross-sectional view of the upper part of the engine taken along line AA in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In an engine upper structure according to one aspect of the present invention, secondary air is supplied to an exhaust port of the engine. An exhaust camshaft and an intake camshaft are provided in a cylinder head at the top of the engine, and a cylinder head cover is fixed on the cylinder head by fastening members. An ignition plug is provided between the intake camshaft and the exhaust camshaft. A reed valve accommodating portion is provided next to the spark plug above the exhaust camshaft in the cylinder head cover, and the reed valve prevents exhaust gas from flowing back from the exhaust port to the upstream side. By providing the reed valve accommodating portion next to the spark plug, the reed valve does not interfere with the spark plug on the cylinder head cover. In addition, in order to ensure sealing between the cylinder head cover and the cylinder head, fastening members are usually positioned at multiple locations away from the spark plug, but by arranging the reed valve next to the spark plug, the reed valve does not interfere with the fastening members. The size of the cylinder head cover is suppressed, and the impact on the layout of the surrounding parts can be suppressed. By forming a secondary air supply passage on the cylinder head cover on the opposite side of the exhaust camshaft from the spark plug, the supply passage can be shortened without changing the arrangement of the exhaust camshaft and the spark plug. This reduces pressure loss of the secondary air in the supply passage and improves exhaust gas purification performance. EXAMPLES

[0010] The saddle riding vehicle of this embodiment will be described below with reference to the accompanying drawings. Fig. 1 is a right side view of the saddle riding vehicle of this embodiment. In the following drawings, the arrow Fr indicates the front of the vehicle, the arrow Re indicates the rear of the vehicle, the arrow L indicates the left side of the vehicle, and the arrow R indicates the right side of the vehicle.

[0011] As shown in Fig. 1, the saddle-type vehicle 1 is configured by mounting various parts such as an engine 20 and an electrical system on a body frame 10. A pair of main frames 12 extend diagonally downward and rearward from a head pipe (not shown) of the body frame 10, and the rear portions of the pair of main frames 12 are bent downward to form a pair of body frames 13. A down frame 14 extends downward from the head pipe, and a pair of under frames 15 bent rearward are connected to the lower portion of the down frame 14. The rear ends of the pair of under frames 15 are connected to the lower portions of the pair of body frames 13, so that the body frame 10 is formed into a cradle shape.

[0012] A front fork 31 is supported on the head pipe via a steering shaft (not shown) so as to be steerable. A handlebar 32 is provided on the upper part of the front fork 31, and a front wheel 33 is rotatably supported on the lower part of the front fork 31. A fuel tank 34 is placed on the upper part of the pair of main frames 12, and the main frames 12 and the fuel tank 34 are covered from the sides by front side covers 41. A seat 42 is installed behind the fuel tank 34, and a seat frame that supports the seat 42 from below is covered from the sides by rear side covers 43.

[0013] A swing arm 44 is supported by the body frame 13 so as to be able to swing. The swing arm 44 extends rearward from the body frame 13, and a rear wheel 45 is rotatably supported at the rear end of the swing arm 44. The engine 20 is a four-stroke single-cylinder engine, and is suspended inside the body frame 10 via a plurality of suspension brackets. A cylinder assembly, in which a cylinder 22, a cylinder head 23, and a cylinder head cover 24 are layered, is attached to an upper portion of a crankcase 21 of the engine 20. An intake device such as an air cleaner 46 is provided behind the cylinder head 23.

[0014] The saddle riding type vehicle 1 of this embodiment is equipped with a secondary air supply device that promotes the combustion of unburned gas in the exhaust gas. In the secondary air supply device, a passage for secondary air is formed from the air cleaner 46 to the exhaust port 61 (see FIG. 5), and a reed valve 73 (see FIG. 5) that prevents the backflow of exhaust gas from the exhaust port 61 to the air cleaner 46 side is installed in the cylinder head cover 24. In this case, the ignition plug 59 and fastening bolts 69a-69c are provided on the cylinder head cover 24 (see FIG. 4), and it is necessary to secure an installation space for the reed valve 73 so as not to interfere with the ignition plug 59 and the fastening bolts 69a-69c.

[0015] In addition, a flow path for secondary air is formed in the cylinder head cover 24 from the reed valve 73 to the exhaust port 61, but depending on the installation location of the reed valve 73, the flow path may become longer, increasing pressure loss and worsening the supply of secondary air to the exhaust port 61. In order to ensure exhaust gas purification performance, the reed valve 73 must be installed taking into consideration its positional relationship with the exhaust port 61. Therefore, the reed valve 73 is installed in the space above the exhaust camshaft 56 so that the reed valve 73 can be brought close to the exhaust port 61 without interfering with the spark plug 59 or the fastening bolts 69a-69c (see Figure 4).

[0016] The upper structure of the engine will be described with reference to Figures 2 to 4. Figure 2 is a right side view of the engine and its surroundings in this embodiment. Figure 3 is a front view of the upper part of the engine in this embodiment. Figure 4 is a top view of the upper part of the engine in this embodiment.

[0017] As shown in Fig. 2, a pair of main frames 12 and a down frame 14 are connected to the upper part of the body frame 10 via a reinforcing bridge tube 16. Below the bridge tube 16, a cylinder head 23 at the upper part of the engine 20 and a crankcase 21 at the lower part of the engine 20 are suspended from the body frame 10 by suspension brackets 17-19. A cylinder 22 is installed on the crankcase 21, and a cylinder head 23 is installed on the cylinder 22. A cylinder head cover 24 is installed on the cylinder head 23, and a DOHC type valve train is housed inside the cylinder head 23 and the cylinder head cover 24.

[0018] A clutch cover 25 that covers a clutch (not shown) from the side is attached to the right side of the crankcase 21. A water pump 26 that sends cooling water to the engine 20 is attached in front of the clutch cover 25. An air cleaner 46 is installed at the rear of the engine 20. The air cleaner 46 is connected to the rear side (intake side) of the cylinder head 23 via a throttle body 47 and an intake pipe 48. Air is sent from the air cleaner 46 to the throttle body 47, and after the intake amount is adjusted by the throttle body 47, the air is supplied from the throttle body 47 to an intake port 62 (see FIG. 5) of the cylinder head 23 through the intake pipe 48.

[0019] 2 and 3, an electromagnetic air cut valve 71 is installed on the right side of the cylinder head cover 24 as an air control device for secondary air. A storage section 74 for a reed valve 73 is provided on the front side (exhaust side) of the cylinder head cover 24, and the storage section 74 is closed from above by a reed valve cover 75. A first hose 81 extends from the air cleaner 46 to the air cut valve 71, and a second hose 82 extends from the air cut valve 71 to the reed valve cover 75. A secondary air supply passage 64 extends from the inside of the reed valve cover 75 to the exhaust port 61 of the cylinder head 23.

[0020] Secondary air is sent from the air cleaner 46 to the air cut valve 71 through a first hose 81, the timing of the secondary air introduction is controlled by the air cut valve 71, and the secondary air is sent from the air cut valve 71 into the reed valve cover 75 through a second hose 82. Secondary air is supplied from inside the reed valve cover 75 to the exhaust port 61, and unburned gas in the exhaust gas is re-burned to reduce air pollutants. In addition, the reed valve 73 is installed inside the reed valve cover 75, and the reed valve 73 prevents exhaust gas from flowing back from the exhaust port 61 to the air cleaner 46 side.

[0021] The air cut valve 71 is supported in a floating state on the cylinder head cover 24 via a bracket 83. The bracket 83 is formed into an inverted L shape with a vertical plate portion and a horizontal plate portion, and the vertical plate portion of the bracket 83 is fixed to the upper wall 51 of the cam chain chamber of the cylinder head cover 24. An inverted U-shaped linear member 84 with both ends facing downward is provided on the horizontal plate portion of the bracket 83, and the air cut valve 71 is attached to both ends of the linear member 84. Compared to a configuration in which the air cut valve 71 is supported by the body frame 10, the air cut valve 71 can be installed closer to the cylinder head cover 24.

[0022] As shown in Fig. 4, the right side of the top surface of the cylinder head cover 24 bulges out to form an upper wall 51 of the cam chain chamber. The front side of the top surface of the cylinder head cover 24 bulges out to form an upper wall 52 of the exhaust camshaft chamber, and the rear side of the top surface of the cylinder head cover 24 bulges out to form an upper wall 53 of the intake camshaft chamber. The upper wall 51 of the cam chain chamber extends in the front-to-rear direction of the engine, and the upper walls 52, 53 of the exhaust camshaft chamber and the intake camshaft chamber extend in the width direction of the engine. The upper walls 52, 53 of the exhaust camshaft chamber and the intake camshaft chamber are formed one step lower than the upper wall 51 of the cam chain chamber.

[0023] An ignition plug 59 is installed between upper walls 52, 53 of the exhaust camshaft chamber and the intake camshaft chamber, i.e., between the exhaust camshaft 56 and the intake camshaft 57. Three fastening bolts (fastening members) 69a-69c are installed around the spark plug 59, and the cylinder head cover 24 is fixed to the cylinder head 23 by the three fastening bolts 69a-69c. In a top view, the fastening bolts 69a, 69b are located above the exhaust camshaft 56 and the intake camshaft 57 on the right side of the engine (one side in the engine width direction), and the fastening bolt 69c is located to the side of the spark plug 59 on the left side of the engine (the other side in the engine width direction).

[0024] In this case, the fastening bolt 69a is located diagonally forward and to the right of the spark plug 59 on the top wall 52 of the exhaust camshaft chamber, the fastening bolt 69b is located diagonally rear and to the right of the spark plug 59 on the top wall 53 of the intake camshaft chamber, and the fastening bolt 69c is located to the left of the spark plug 59. The three fastening bolts 69a-69c secure the cylinder head cover 24 to the cylinder head 23 in a well-balanced manner to ensure sealing. Usually, four-point fixing is the mainstream method for ensuring sealing of the cylinder head cover 24, but by using three-point fixing, it becomes easier to ensure installation space for a reed valve 73 (see FIG. 5) in front of the spark plug 59.

[0025] An accommodation portion 74 for accommodating a reed valve 73 is provided in the cylinder head cover 24 above the exhaust camshaft 56 and next to the spark plug 59, i.e., directly in front of the spark plug 59 on the upper wall 52 of the exhaust camshaft chamber. The accommodation portion 74 is closed from above by a reed valve cover 75, which is screwed to the accommodation portion 74 by a pair of fastening bolts 69d, 69e. In this way, the reed valve 73 is installed in the empty space of the cylinder head cover 24 so as not to interfere with the spark plug 59 and the fastening bolts 69a-69c, thereby preventing the cylinder head cover 24 from becoming larger.

[0026] On the opposite side of the spark plug 59 across the exhaust camshaft 56 in the cylinder head cover 24, a front wall of the cylinder head cover 24 near the accommodation portion 74 partially protrudes forward. A supply passage 64 that introduces secondary air from the accommodation portion 74 to the exhaust port 61 (see FIG. 3) is formed in the protruding portion 63 of the cylinder head cover 24. Since only the vicinity of the accommodation portion 74 of the cylinder head cover 24 protrudes, the size of the cylinder head cover 24 is kept to a minimum. Since the supply passage 64 extends downward from the accommodation portion 74, the supply passage 64 is shortened while avoiding the exhaust camshaft 56, and pressure loss of the secondary air is suppressed.

[0027] The layout of the reed valve and the supply passage will be described with reference to Figures 3 and 5. Figure 5 is a cross-sectional view of the upper part of the engine taken along line AA in Figure 3. Note that the ignition plug is omitted in Figure 5.

[0028] 3 and 5, an exhaust port 61 is formed at the lower front side of the cylinder head 23, and an intake port 62 is formed at the lower rear side of the cylinder head 23. A cylinder head cover 24 is installed on the cylinder head 23, and an exhaust camshaft chamber is formed at the upper front side of the cylinder head 23, and an intake camshaft chamber is formed at the upper rear side of the cylinder head 23. In the exhaust camshaft chamber, an exhaust camshaft 56 is installed in the cylinder head 23 via an exhaust cam housing 91, and in the intake camshaft chamber, an intake camshaft 57 is installed in the cylinder head 23 via an intake cam housing 92.

[0029] A plug hole 55 for an ignition plug 59 (see FIG. 4) is formed in approximately the center of the cylinder head 23 and the cylinder head cover 24. An exhaust valve 93 is driven by an exhaust camshaft 56 in front of the plug hole 55 to open and close the exhaust port 61, and an intake valve 94 is driven by an intake camshaft 57 in rear of the plug hole 55 to open and close the intake port 62. An accommodation portion 74 for a reed valve 73 is formed on the upper wall 52 of the exhaust camshaft chamber of the cylinder head cover 24. The bottom surface of the accommodation portion 74 becomes deeper from a position directly above the exhaust camshaft 56 toward the front.

[0030] The upper part of the accommodation part 74 is recessed in a stepped shape, and the reed valve 73 is installed in the recess of the accommodation part 74. An opening 77 is formed in a plate-shaped base 76 of the reed valve 73, and the base ends of a reed 78 and a stopper 79 are fixed to the underside of the base 76. The reed 78 is made of a thin metal or resin plate and is formed to be elastically deformable. When the exhaust port 61 is under positive pressure, the opening 77 is closed to prevent the backflow of exhaust gas, and when the exhaust port 61 is under negative pressure, the opening 77 is opened to supply secondary air. The tip of the stopper 79 is spaced downward from the base 76, and the amount by which the reed 78 opens is regulated by the stopper 79.

[0031] The tip of the stopper 79 of the reed valve 73 is located forward of the exhaust camshaft 56 (on the supply passage 64 side). Therefore, the tip of the stopper 79 does not interfere with the upper wall 52 of the camshaft chamber, and the reed valve 73 can be installed at a lower position above the exhaust camshaft 56. A reed valve cover 75 is installed on the accommodation portion 74 of the cylinder head cover 24. In this case, the height H of the mating surface 65 of the accommodation portion 74 and the reed valve cover 75 is lower than the upper surface of the upper wall 51 of the cam chain chamber of the cylinder head cover 24, so the height of the cylinder head cover 24 is kept down.

[0032] The reed valve cover 75 is fixed to the accommodation portion 74 by fastening bolts 69d, 69e in opposing positions sandwiching the exhaust camshaft 56 in a top view. The fastening bolt 69d is positioned between axes C0, C1 that pass through the centers of the spark plug hole 55 and the exhaust camshaft 56 and are parallel to the cylinder axis. The fastening bolt 69e is positioned forward of the axis C1 of the exhaust camshaft 56 and on the protruding portion 63 of the cylinder head cover 24. By positioning the fastening bolts 69d, 69e away from directly above the exhaust camshaft 56, it is possible to secure the screw holes of the fastening bolts 69d, 69e without raising the mating surface 65 of the accommodation portion 74 and the reed valve cover 75.

[0033] The bottom of the accommodation portion 74 becomes deeper toward the front, and a supply passage 64 is formed from the deepest point of the bottom of the accommodation portion 74 toward the exhaust port 61. Inside the protrusion 63 of the cylinder head cover 24, the supply passage 64 passes directly below the fastening bolt 69e, and inside the cylinder head 23, the supply passage 64 extends obliquely to near the outlet of the exhaust port 61. The supply passage 64 extends in the vertical direction, wrapping around the front of the exhaust camshaft 56. Because the reed valve 73 is positioned above the exhaust port 61, the supply passage 64 from the reed valve 73 to the exhaust port 61 is shortened.

[0034] As described above, according to the upper structure of the engine 20 of this embodiment, the reed valve 73 does not interfere with the spark plug 59 and the fastening bolts 69a-69c on the cylinder head cover 24. The size of the cylinder head cover 24 is prevented from increasing, and the effect on the layout of the surrounding parts can be reduced. The accommodation portion 74 for the reed valve 73 is provided above the exhaust camshaft 56, and the supply passage 64 is formed on the opposite side of the exhaust camshaft 56 from the spark plug 59, so that the supply passage 64 can be shortened without changing the positions of the exhaust camshaft 56 and the spark plug 59. The pressure loss of the secondary air in the supply passage 64 can be reduced, and the purification performance of the exhaust gas can be improved.

[0035] In this embodiment, a single cylinder engine is illustrated, but a multi-cylinder engine may be used. In this case, it is preferable that the cylinder head cover is fixed to the cylinder head with three fastening bolts per cylinder.

[0036] Further, in this embodiment, the cylinder head cover is fixed to the cylinder head at three points, but the cylinder head cover may be fixed to the cylinder head at four or more points.

[0037] Further, in this embodiment, the reed valve cover is fixed to the housing portion of the cylinder head cover at two points, but the reed valve cover may be fixed to the housing portion at three or more points.

[0038] The engine upper structure of this embodiment is not limited to the above-mentioned off-road type saddle-ride vehicle, and may be used in other types of saddle-ride vehicles. Note that a saddle-ride vehicle is not limited to all vehicles in which the rider sits astride the seat, but also includes scooter-type vehicles in which the rider does not sit astride the seat.

[0039] As described above, the first embodiment is an upper structure of an engine in which secondary air is supplied to the exhaust port (61) of the engine (20), and includes a cylinder head (23) on which an exhaust camshaft (56) and an intake camshaft (57) are installed, a cylinder head cover (24) fixed on the cylinder head with fastening members (fastening bolts 69a-69c), a reed valve (73) for preventing exhaust gas from flowing back from the exhaust port to the upstream side, and an ignition plug (59) located between the intake camshaft and the exhaust camshaft, a housing portion (74) for housing the reed valve is provided on the cylinder head cover above the exhaust camshaft and next to the ignition plug, and a supply passage (64) for introducing secondary air from the housing portion to the exhaust port is formed on the cylinder head cover on the opposite side of the ignition plug across the exhaust camshaft. With this configuration, the reed valve does not interfere with the ignition plug on the cylinder head cover. Also, in order to ensure the sealing between the cylinder head cover and the cylinder head, fastening members are usually positioned at multiple locations away from the spark plug, but by installing the reed valve next to the spark plug, the reed valve does not interfere with the fastening members. The size of the cylinder head cover is prevented from increasing, and the impact on the layout of surrounding parts is reduced. A reed valve housing is provided above the exhaust camshaft, and a supply passage is formed on the opposite side of the exhaust camshaft from the spark plug, so the supply passage can be shortened without changing the position of the exhaust camshaft and the spark plug. The pressure loss of secondary air in the supply passage can be reduced, improving the purification performance of exhaust gas.

[0040] In the second embodiment, the accommodating portion is closed from above by the reed valve cover (75) in the first embodiment, a cam chain chamber is formed in the cylinder head cover, and the mating surface (65) between the accommodating portion and the reed valve cover is lower than the upper surface of the upper wall (51) of the cam chain chamber of the cylinder head cover. With this configuration, the mating surface between the accommodating portion and the reed valve cover is lowered, making it possible to reduce the height of the cylinder head cover.

[0041] In the third aspect, in the second aspect, the reed valve cover is fixed to the housing at a position opposite to the exhaust camshaft. With this configuration, the reed valve cover is fixed at a position that is not directly above the exhaust camshaft, and the mating surface between the reed valve cover and the housing can be lowered.

[0042] In a fourth aspect, in any one of the first to third aspects, a wall of the cylinder head cover opposite the ignition plug across the exhaust camshaft protrudes, and a supply passage for introducing secondary air from the accommodation portion to the exhaust port is formed inside the protruding portion (63) of the wall. With this configuration, it is possible to form the supply passage at a position that avoids the exhaust camshaft while minimizing the increase in size of the cylinder head cover.

[0043] In a fifth aspect, in any one of the first to fourth aspects, the reed valve has a seat (76) in which an opening (77) is formed, a reed (78) that opens and closes the opening, and a stopper (79) that regulates the amount of opening of the reed, and a base end of the stopper is fixed to the seat so that a tip end of the stopper is spaced downward from the seat, and the tip end of the stopper is located closer to the supply passage than the exhaust camshaft. With this configuration, the reed valve can be installed at a lower position above the exhaust camshaft.

[0044] In a sixth aspect, in any one of the first to fifth aspects, the cylinder head cover is fixed to the cylinder head with three fastening members per cylinder, and in a top view, the three fastening members are located at two locations above the intake camshaft and the exhaust camshaft on one side in the engine width direction, and at one location to the side of the spark plug on the other side in the engine width direction. With this configuration, the cylinder head cover is fixed to the cylinder head with three fastening members per cylinder in a balanced manner, ensuring sealing performance and making it easy to ensure installation space for the reed valve.

[0045] Although the present embodiment has been described, other embodiments may be made by combining the above-described embodiments and modifications in whole or in part.

[0046] In addition, the technology of the present invention is not limited to the above examples, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to the progress of technology or a different technology derived therefrom, the invention may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea. [Explanation of symbols]

[0047] 1: Saddle-type vehicle 20: Engine 23: Cylinder head 24: Cylinder head cover 56: Exhaust camshaft 57: Intake camshaft 59: Spark plug 61: Exhaust port 63: Protrusion 64: Supply route 65:Mating surface 69a-69c: Fastening bolts (fastening members) 73: Reed valve 74: Storage unit 75: Reed valve cover 76: Pedestal 77 :Aperture 78: Lead 79: Stopper

Claims

1. An engine upper structure in which secondary air is supplied to an exhaust port of the engine, comprising: A cylinder head in which an exhaust camshaft and an intake camshaft are installed; a cylinder head cover fixed onto the cylinder head by a fastening member; a reed valve that prevents exhaust gas from flowing backward from the exhaust port to the upstream side; a spark plug located between the intake camshaft and the exhaust camshaft, a housing portion for housing the reed valve is provided in the cylinder head cover above the exhaust camshaft and adjacent to the spark plug; An upper structure of an engine, characterized in that a supply passage for introducing secondary air from the accommodating portion to the exhaust port is formed on the opposite side of the cylinder head cover from the ignition plug across the exhaust camshaft.

2. The housing portion is closed from above by a reed valve cover, and a cam chain chamber is formed in the cylinder head cover, 2. The engine upper structure according to claim 1, wherein a mating surface between the housing portion and the reed valve cover is lower than an upper surface of an upper wall of the cam chain chamber of the cylinder head cover.

3. 3. The engine upper structure according to claim 2, wherein the reed valve covers are fixed to the housing portion at opposing positions across the exhaust camshaft.

4. 3. The upper structure of an engine as described in claim 1 or claim 2, wherein a wall of the cylinder head cover opposite the spark plug across the exhaust camshaft protrudes, and a supply passage is formed inside the protruding portion of the wall for introducing secondary air from the accommodating portion to the exhaust port.

5. The reed valve includes a base having an opening, a reed for opening and closing the opening, and a stopper for regulating an opening amount of the reed, A base end portion of the stopper is fixed to the base so that a tip end portion of the stopper is spaced downward from the base, 3. The upper structure of an engine according to claim 1, wherein a tip end of the stopper is located closer to the supply passage than the exhaust camshaft.

6. The cylinder head cover is fixed to the cylinder head by three fastening members per cylinder, 3. The upper structure of an engine as described in claim 1 or claim 2, characterized in that, when viewed from above, the three fastening members are located at two locations above the intake camshaft and the exhaust camshaft on one side of the engine width direction, and at one location to the side of the ignition plug on the other side of the engine width direction.

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