Engine

Abstract

To reduce a damage risk of an exhaust gas sensor in a model in which an exhaust pipe passes a side of a cylinder.SOLUTION: An engine (40) is mounted on a vehicle frame (10) in which a down frame (14) extends downward from a head pipe (11). The engine includes a cylinder head having an exhaust port (47), an exhaust pipe (70) connected to the exhaust port of the cylinder head, and an exhaust gas sensor (84) attached to the exhaust pipe. The exhaust pipe extends downward through one side of the down frame, crosses the front of the down frame, and then, extends upward through the other side of the down frame. A part of the exhaust pipe crossing the down frame is a straight portion (73). The exhaust gas sensor is attached to the straight portion, and is overlapped with the down frame from the front.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] A known engine for a saddle-type vehicle has an exhaust pipe curved in a U-shape in front of the down tube (see, for example, Patent Document 1). In the engine described in Patent Document 1, a cylinder is installed on a crankcase, and a cylinder head is installed on the cylinder. An exhaust port is formed in the front of the cylinder head, and an exhaust pipe extends downward from the exhaust port toward the crankcase. In front of the crankcase, the exhaust pipe curves in a U-shape so that it faces upward, and extends to the cylinder, passing beside the cylinder and extending to the rear of the vehicle where it is connected to a muffler. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3489242 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, an exhaust gas sensor is attached to the exhaust pipe, but if the exhaust pipe has many bends, the flow of exhaust gas becomes biased, which deteriorates the detection accuracy of the exhaust gas sensor. Depending on the installation location of the exhaust gas sensor, there is a high risk of damage to the exhaust gas sensor or the lead wires.

[0005] The present invention has been made in consideration of the above points, and has an object to provide an engine in which the risk of damage to the exhaust gas sensor can be reduced in a model in which the exhaust pipe passes along the side of the cylinder. [Means for solving the problem]

[0006] An engine of one embodiment of the present invention is an engine for a saddle-type vehicle mounted on a body frame having a down frame extending downward from a head pipe, and comprises a cylinder head having an exhaust port formed therein, an exhaust pipe connected to the exhaust port of the cylinder head, and an exhaust gas sensor attached to the exhaust pipe, wherein the exhaust pipe extends downward through one side of the down frame, crosses the front of the down frame, and then extends upward through the other side of the down frame, a part of the exhaust pipe that crosses the down frame is a straight section, and the exhaust gas sensor is attached to the straight section and overlaps the down frame from the front, thereby solving the above-mentioned problem. Effect of the Invention

[0007] According to an engine of one aspect of the present invention, an exhaust gas sensor is attached to a straight section where the flow of exhaust gas is less biased, and the exhaust gas sensor overlaps the down frame from the front and is approximately perpendicular to the straight section. The detection end of the exhaust gas sensor is oriented approximately perpendicular to the flow of exhaust gas, thereby improving detection accuracy. In addition, the straight section of the exhaust pipe has less swing compared to the bent section, so the exhaust gas sensor is stably supported, and the exhaust gas sensor is located on the inner side in the vehicle width direction, which reduces the risk of damage to the exhaust gas sensor when the vehicle rolls over. In addition, by arranging the lead wires of the exhaust gas sensor along the down frame, swinging of the lead wires is suppressed, thereby reducing the risk of damage to the lead wires. [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 engine and its surroundings according to the present embodiment. [Figure 4] FIG. 2 is a perspective view of the engine periphery of the present embodiment as viewed from the right rear. [Diagram 5] FIG. 4 is a cross-sectional view of the engine of FIG. 3 taken along line AA. [Figure 6] FIG. 4 is a cross-sectional view of the engine of FIG. 3 taken along line BB. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An engine according to an embodiment of the present invention is mounted on a body frame of a saddle-type vehicle. An exhaust port is formed in a cylinder head of the engine, an exhaust pipe is connected to the exhaust port of the cylinder head, and an exhaust gas sensor is attached to the exhaust pipe. A down frame extends downward from a head pipe of the body frame, and the exhaust pipe extends downward through one side of the down frame. After crossing the front of the down frame, the exhaust pipe extends upward through the other side of the down frame. A part of the exhaust pipe crossing the down frame is a straight section, and an exhaust gas sensor is attached to the straight section and overlaps the down frame from the front. The exhaust gas sensor is attached to the straight section where the flow of exhaust gas is less biased, and the exhaust gas sensor overlaps the down frame from the front and is approximately perpendicular to the straight section. The detection end of the exhaust gas sensor is directed approximately perpendicular to the flow of exhaust gas, thereby improving detection accuracy. Furthermore, the straight section of the exhaust pipe has less shaking compared to the bent section, so that the exhaust gas sensor is stably supported, and the exhaust gas sensor is located on the inner side in the vehicle width direction, so that the risk of damage to the exhaust gas sensor when the vehicle rolls over can be reduced. In addition, by routing the lead wires of the exhaust gas sensor along the down frame, it is possible to suppress vibration of the lead wires and reduce the risk of breakage of the lead wires. 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 40 and an electrical system on a body frame 10. A pair of main frames 12 extend diagonally downward and rearward from a head pipe 11 (see Fig. 2) 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 11, and an under-loop 15 bent rearward is connected to a lower portion of the down frame 14. The rear ends of the pair of under-loops 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 25 is supported on the head pipe 11 via a steering shaft (not shown) so as to be steerable. A handlebar 26 is provided on the upper part of the front fork 25, and a front wheel 27 is rotatably supported on the lower part of the front fork 25. A fuel tank 31 is placed on the upper part of the pair of main frames 12, and the main frames 12 and the fuel tank 31 are covered from the sides by front side covers 33. A seat 32 is installed behind the fuel tank 31, and a seat frame 16 (see FIG. 2) that supports the seat 32 from below is covered from the sides by a rear side cover 34.

[0013] A swing arm 35 is supported by the body frame 13 so as to be able to swing. The swing arm 35 extends rearward from the body frame 13, and a rear wheel 36 is rotatably supported at the rear end of the swing arm 35. The engine 40 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 42, a cylinder head 43, and a cylinder head cover 44 are layered, is attached to an upper portion of a crankcase 41 of the engine 40. An air cleaner 48 is provided behind the cylinder head 43.

[0014] Left and right radiators 51, 55 (only the right radiator 51 is shown in FIG. 1) are located in front of the cylinder head 43, and the left and right radiators 51, 55 are attached to the down frame 14. An exhaust pipe 70 extends downward from the left side of the front surface of the cylinder head 43, passes along the right side of the cylinder 42 and is connected to a muffler 79 at the rear of the vehicle. A primary catalyst case 74 is formed in the exhaust pipe 70 in front of the crankcase 41, and a secondary catalyst case 78 is formed in the exhaust pipe 70 behind the air cleaner 48. A primary catalyst 81 is housed in the primary catalyst case 74, and a secondary catalyst 82 is housed in the secondary catalyst case 78.

[0015] If the primary catalyst case 74 is provided in front of the crankcase 41, it is difficult to provide an oxygen sensor upstream or downstream of the primary catalyst case 74. In the saddle-type vehicle 1 of this embodiment, the exhaust pipe 70 has many bends, which causes the flow of exhaust gas in the exhaust pipe 70 to be biased, resulting in poor detection accuracy depending on the location where the oxygen sensor is installed. Also, there is a high risk of damage to the oxygen sensor and lead wires in front of the crankcase 41. Therefore, in this embodiment, the oxygen sensor is installed in a straight portion where there is little bias in the flow of exhaust gas in the exhaust pipe 70, where there is little risk of damage, and at a location where the oxygen sensor overlaps from the front with the down frame, which serves as a route for routing the lead wires.

[0016] The peripheral structure of the engine will be described with reference to Figures 2 to 4. Figure 2 is a right side view of the engine periphery of this embodiment. Figure 3 is a front view of the engine periphery of this embodiment. Figure 4 is a perspective view of the engine periphery of this embodiment as viewed from the right rear.

[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 17. Below the bridge tube 17, an engine 40 is suspended from the body frame 10 by suspension brackets 21-23. A clutch cover 45 is attached to the right side of a crankcase 41 of the engine 40, and a water pump 46 is installed in front of the clutch cover 45. A discharge port of the water pump 46 is connected to a cooling passage in the crankcase 41, and cooling water is sent from the water pump 46 to the inside of the cylinder 42 and the water jacket in the cylinder head 43.

[0018] 2 and 3, a right radiator 51 and a left radiator 55 are installed in front of the cylinder head 43, sandwiching the down frame 14 at the center of the vehicle. The right radiator 51 is formed larger than the left radiator 55. The right radiator 51 has a right inlet tank 52 installed below the right radiator core 53, and a right outlet tank 54 installed above the right radiator core 53. The left radiator 55 has a left inlet tank 56 installed above the left radiator core 57, and a left outlet tank 58 installed below the left radiator core 57.

[0019] A thermostat cover 61 is provided on the front of the engine 40, and a thermostat (not shown) is installed inside the thermostat cover 61. The right inlet tank 52 is connected to the thermostat cover 61 via an inlet hose 62. The right outlet tank 54 and the left inlet tank 56 are connected via a radiator hose 63. The left outlet tank 58 is connected to the water pump 46 via an outlet hose 64. The upper part of the thermostat cover 61 is connected to the right outlet tank 54 via an air bleeding hose 65.

[0020] In the right radiator 51, the coolant flows upward from the right inlet tank 52 to the right outlet tank 54, and the heat of the coolant is dissipated into the air while the coolant passes through the right radiator core 53. The coolant is sent from the right outlet tank 54 to the left inlet tank 56 through the radiator hose 63. In the left radiator 55, the coolant flows downward from the left inlet tank 56 to the left outlet tank 58, and the heat of the coolant is dissipated into the air while the coolant passes through the left radiator core 57. The right radiator 51 and the left radiator 55 dissipate heat in two stages, improving cooling efficiency.

[0021] An intermediate portion of the cylinder head 43 and the outlet hose 64 is connected via a bypass hose (not shown). The bypass hose forms a bypass passage that returns the cooling water from the cylinder head 43 (upstream of the thermostat) to the water pump 46, bypassing the right radiator 51 and the left radiator 55. While the cooling water temperature is below a predetermined temperature, the thermostat closes and the cooling water is returned from the cylinder head 43 through the bypass hose to the water pump 46. When the cooling water temperature reaches or exceeds the predetermined temperature, the thermostat opens and the cooling water also flows through the right radiator 51 and the left radiator 55 to cool the engine 40.

[0022] An exhaust port 47 facing diagonally downward to the left is formed on the front surface of the cylinder head 43, and an exhaust pipe 70 is connected to the exhaust port 47. The exhaust pipe 70 extends downward from the exhaust port 47 through the left side of the down frame 14, crosses the front of the down frame 14, and then extends upward through the right side of the down frame 14. The exhaust pipe 70 is curved into a U-shape using the space in front of the vehicle body, so that the radius of curvature of the curved portion of the exhaust pipe 70 is increased, thereby reducing exhaust resistance. In addition, the exhaust pipe 70 extends rearward through the right side of the cylinder 42, and the rear end of the exhaust pipe 70 is connected to a muffler 79 near the seat 32.

[0023] The exhaust pipe 70 is formed by connecting an upstream pipe 71, an expanded pipe 72, a primary catalyst case 74, a reduced diameter pipe 75, a downstream pipe 76, an expanded pipe 77 (see FIG. 1), and a secondary catalyst case 78 (see FIG. 1). The upstream pipe 71 extends diagonally downward to the left from the exhaust port 47 and then curves to the right. The expanded pipe 72 extends to the right from the downstream end of the upstream pipe 71, crosses the front of the down frame 14, and then curves diagonally upward to the right. The front half of the expanded pipe 72 that crosses the down frame 14 is a straight section 73 that is straight, and the rear half of the expanded pipe 72 curves while expanding in diameter from the straight section 73 toward the downstream.

[0024] A guard member 83 protrudes upward from the straight portion 73 of the expanded pipe 72, and a first oxygen sensor (exhaust gas sensor) 84 is attached to the upper surface of the straight portion 73 behind the guard member 83 in a front view. The first oxygen sensor 84 is located in front of the down frame 14, and is sandwiched from the front and rear by the down frame 14 and the guard member 83. The first oxygen sensor 84 is protected by the guard member 83 and the down frame 14. By attaching the first oxygen sensor 84 to the straight portion 73, bias in the flow of exhaust gas is reduced near the detection end of the first oxygen sensor 84, improving detection accuracy.

[0025] The primary catalyst case 74 and the reduced diameter pipe 75 are formed as a single unit. The primary catalyst case 74 extends diagonally upward to the right from the downstream end of the expanded diameter pipe 72, and the reduced diameter pipe 75 is curved backward from the downstream end of the primary catalyst case 74. The primary catalyst case 74 is formed with a larger pipe diameter than the upstream pipe 71. A primary catalyst 81 is housed inside the primary catalyst case 74, and air pollutants in the exhaust gas are purified by passing through the primary catalyst 81. The reduced diameter pipe 75 is curved while reducing in diameter from the primary catalyst case 74 toward the downstream.

[0026] The downstream side of the reduced diameter pipe 75 is positioned to the side of the cylinder 42, and a second oxygen sensor 86 is attached to the reduced diameter pipe 75 on the side of the cylinder 42. The base end of the second oxygen sensor 86 faces inward in the vehicle width direction and is positioned in a space surrounded by peripheral components such as the right radiator 51, cylinder head 43, inlet hose 62, and reduced diameter pipe 75. The second oxygen sensor 86 is protected by the peripheral components. The second oxygen sensor 86 is positioned on the reduced diameter downstream side of the reduced diameter pipe 75, and even if the reduced diameter pipe 75 is curved, exhaust gas is likely to hit the detection end of the second oxygen sensor 86, and detection accuracy is not impaired.

[0027] The downstream pipe 76 extends rearward from the downstream end of the reduced diameter pipe 75, passing through the right side of the cylinder 42. The expanded diameter pipe 77 expands rearward from the downstream end of the downstream pipe 76. The secondary catalyst case 78 is formed with a diameter larger than the pipe diameter of the downstream pipe 76. A secondary catalyst 82 (see FIG. 1) is housed inside the secondary catalyst case 78, and air pollutants in the exhaust gas are purified as the exhaust gas passes through the secondary catalyst 82. A muffler 79 is connected to the downstream end of the secondary catalyst case 78, and the exhaust gas that has passed through the secondary catalyst 82 is discharged from the muffler 79 to the outside.

[0028] Further, the expanded pipe 72 is formed in a sandwich structure consisting of front and rear pipe halves, and the primary catalyst case 74 and the reduced pipe 75 are also formed in a sandwich structure consisting of left and right pipe halves. This makes it easy to provide mounting bosses for the first and second oxygen sensors 84, 86 on each pipe half. The first oxygen sensor 84 detects the oxygen concentration of the exhaust gas, and the second oxygen sensor 86 detects the oxygen concentration of the exhaust gas that has passed through the primary catalyst 81. The detection result of the first oxygen sensor 84 is used for feedback control of the fuel injection amount, and the detection result of the second oxygen sensor 86 is used for diagnosing catalyst deterioration.

[0029] As shown in Fig. 4, a first lead wire 85 extends upward from a base end of a first oxygen sensor 84 (see Fig. 2), and a second lead wire 87 extends upward from a base end of a second oxygen sensor 86. A shroud 66 that covers a right radiator core 53 is provided in the right radiator 51, and cable holders 67, 68 are provided on the shroud 66. The first lead wire 85 is held by a suspension bracket 23 (see Fig. 3) of the down frame 14, and then extends toward the second oxygen sensor 86 and is held by the cable holders 67, 68 of the shroud 66 together with the first lead wire 85. By suppressing the swinging of the first and second lead wires 85, 87, damage to the first and second lead wires 85, 87 is suppressed.

[0030] The layout of the first oxygen sensor will be described in detail with reference to Figures 3, 5 and 6. Figure 5 is a cross-sectional view of the engine in Figure 3 taken along line AA. Figure 6 is a cross-sectional view of the engine in Figure 3 taken along line BB.

[0031] As shown in Fig. 3, the straight portion 73 of the exhaust pipe 70 extends across the front of the down frame 14 in the vehicle width direction. A guard member 83 protrudes from the upper surface of the straight portion 73, and a first oxygen sensor 84 is attached to the upper surface of the straight portion 73 on the back side of the guard member 83. When going over an obstacle, the straight portion 73 of the exhaust pipe 70 sways less than the bent portion, so the first oxygen sensor 84 is stably supported. The first oxygen sensor 84 overlaps with the down frame 14 from the front, and the first oxygen sensor 84 is approximately perpendicular to the straight portion 73, so detection accuracy is stable.

[0032] In this case, the extension line L1 of the upper edge of the upstream pipe 71 is extended to the right side to divide the expanded pipe 72 into upper and lower parts. A first oxygen sensor 84 is attached to the lower area of ​​the expanded pipe 72, and the first oxygen sensor 84 is not attached to the upper area of ​​the expanded pipe 72. The lower area of ​​the expanded pipe 72 is a straight section 73 where the flow speed of the exhaust gas is high, improving the exchange performance of the exhaust gas and reducing the bias of the exhaust gas flow. In the lower area of ​​the expanded pipe 72, the detection end of the first oxygen sensor 84 is oriented approximately perpendicular to the flow of the exhaust gas, improving the detection accuracy.

[0033] In a front view, the first oxygen sensor 84 extends parallel to the down frame 14, and is located inside both side surfaces of the down frame 14 in the engine width direction. The first lead wire 85 extending from the base end (upper end) of the first oxygen sensor 84 can be easily routed along the down frame 14. The down frame 14 and the guard member 83 face each other in the front-rear direction, and the first oxygen sensor 84 is sandwiched between the down frame 14 and the guard member 83. In front of the engine 40, the first oxygen sensor 84 is protected from the front and rear by the down frame 14 and the guard member 83.

[0034] In a side view, the first oxygen sensor 84 overlaps with the exhaust pipe 70 that passes through both sides of the down frame 14 (see FIG. 2). The upstream pipe 71 is located on the left side of the first oxygen sensor 84, and the primary catalyst case 74 is located on the right side of the first oxygen sensor 84. The first oxygen sensor 84 is protected by the upstream pipe 71 and the primary catalyst case 74, reducing the risk of damage to the first oxygen sensor 84 when the vehicle rolls over. As described above, the primary catalyst 81 is housed inside the primary catalyst case 74, and is positioned so that the primary catalyst 81 overlaps with the first oxygen sensor 84 in a side view (see FIG. 2).

[0035] In this case, the primary catalyst 81 is located above the lower end of the down frame 14 and the underloop 15 and below the exhaust port 47. In front view, the upper end of the primary catalyst 81 is inclined so as to be located further outward in the vehicle width direction than the lower end, and in side view, the lower end of the primary catalyst 81 is inclined so as to be located forward of the upper end (see FIG. 2). In side view, the primary catalyst 81 overlaps the down frame 14, and the lower end of the primary catalyst 81 is located forward of the down frame 14 (see FIG. 2). By bringing the primary catalyst 81 closer to the first oxygen sensor 84, the first oxygen sensor 84 is activated early by utilizing the heat of the primary catalyst 81, improving detection accuracy.

[0036] As shown in FIG. 5, the axis C1 of the first oxygen sensor 84 is inclined so as to approach the axis C2 of the down frame 14 in a side view. The first oxygen sensor 84 is inclined slightly rearward to reduce the risk of damage due to a collision with a flying stone or the like from the front. In addition, the first lead wire 85 (see FIG. 6) can be easily routed along the down frame 14. In a side view, the axis C1 of the first oxygen sensor 84 extends approximately parallel to the axis of the front fork 25 (see FIG. 1), and the first oxygen sensor 84 is located inside the positions P1 and P2 of both ends of the straight portion 73 in the front-rear direction. Since the first oxygen sensor 84 does not protrude from the straight portion 73, a gap is secured between the first oxygen sensor 84 and the down frame 14 or the front wheel 27, and there is no need to extend the wheelbase to install the first oxygen sensor 84.

[0037] In a side view, the guard member 83 protrudes vertically from the straight portion 73, and the upper end of the guard member 83 is located above the base end of the first oxygen sensor 84. The first oxygen sensor 84 is tilted upward so as to move away from the guard member 83. The further the first oxygen sensor 84 moves upward, the farther it is from the guard member 83, so that even if the guard member 83 is hit by a flying stone or the like and deformed, the effect on the first oxygen sensor 84 is suppressed. The gap between the first oxygen sensor 84 and the guard member 83 makes it easier to attach the first oxygen sensor 84 and to route the first lead wire 85.

[0038] The under-loop 15 curves downward and rearward from the down frame 14. When an extension line L2 of the lower edge of the under-loop 15 is extended at the middle position of the curved portion of the under-loop 15, the first oxygen sensor 84 is located above the extension line L2. By positioning the first oxygen sensor 84 above the extension line L2 of the under-loop 15, the exhaust pipe 70 (straight portion 73) is positioned higher. Therefore, when the saddle-type vehicle 1 goes over an obstacle, the first oxygen sensor 84 will not hit the obstacle, and even if the exhaust pipe 70 interferes with the obstacle and is dented, the risk of damage to the first oxygen sensor 84 is reduced.

[0039] 6, the guard member 83 is formed in an arc shape when viewed from above, and the first oxygen sensor 84 is located between the guard member 83 and the down frame 14. The guard member 83 and the down frame 14 are brought close to the first oxygen sensor 84 from the front and rear, and the first oxygen sensor 84 is covered by the down frame 14 from the rear, eliminating the need to form the guard member 83 around the entire periphery. Since the guard member 83 is no longer necessary behind the first oxygen sensor 84, a working space is secured between the down frame 14 and the guard member 83 for attaching the first oxygen sensor 84 with a tool, and deterioration of ease of assembly is suppressed.

[0040] As described above, according to the engine 40 of this embodiment, the first oxygen sensor 84 is attached to the straight portion 73 where the flow of the exhaust gas is less biased, and the first oxygen sensor 84 overlaps the down frame 14 from the front and is approximately perpendicular to the straight portion 73. The detection end of the first oxygen sensor 84 is oriented approximately perpendicular to the flow of the exhaust gas, thereby improving the detection accuracy. In addition, the straight portion 73 of the exhaust pipe 70 has less swing compared to the bent portion, so that the first oxygen sensor 84 is stably supported, and the first oxygen sensor 84 is located on the inner side in the vehicle width direction, so that the risk of damage to the first oxygen sensor 84 when the vehicle rolls over can be reduced. In addition, by arranging the first lead wire 85 along the down frame 14, the swing of the first lead wire 85 can be suppressed, and the risk of damage to the first lead wire 85 can be reduced.

[0041] In this embodiment, the exhaust pipe extends downward from the cylinder head, curves significantly in front of the crankcase, and then extends rearward by passing around the sides of the cylinders, but the exhaust pipe may extend rearward from the cylinder head by passing around the sides of the cylinders. For example, the exhaust pipe may extend laterally from the cylinder head and then extend rearward by passing around the sides of the cylinders.

[0042] In addition, in this embodiment, an oxygen sensor is used as an example of an exhaust gas sensor, but the exhaust gas sensor may be any sensor capable of detecting the average characteristics of the exhaust gas, and may be, for example, an exhaust temperature sensor that detects the exhaust temperature of the exhaust gas.

[0043] In addition, in this embodiment, the first oxygen sensor serving as an exhaust gas sensor is attached to the straight portion of the enlarged pipe, but the exhaust gas sensor may be attached to the straight portion of the exhaust pipe that crosses the down frame.

[0044] Furthermore, in this embodiment, the first and second oxygen sensors serving as exhaust gas sensors are provided in the exhaust pipe, but it is sufficient that at least one exhaust gas sensor is provided in the exhaust pipe.

[0045] Furthermore, in this embodiment, the exhaust pipe is provided with a primary catalyst case and a secondary catalyst case, but it is sufficient that the exhaust system is provided with at least one catalyst case.

[0046] Further, in this embodiment, the body frame is provided with an underloop, but the shape of the body frame is not particularly limited as long as the underframe extends downward from at least the head pipe.

[0047] In addition, in this embodiment, a water-cooled engine is exemplified as the engine, but the engine may be an air-cooled engine or an oil-cooled engine.

[0048] Moreover, the exhaust pipe in this embodiment may be a single pipe or a double pipe.

[0049] The engine of the present embodiment may be used in other types of saddle-ride vehicles, not limited to the off-road type saddle-ride vehicles described above. Note that the saddle-ride vehicle is not limited to vehicles in general in which the rider sits astride the seat, but also includes scooter-type vehicles in which the rider does not sit astride the seat.

[0050] As described above, the first embodiment is an engine (40) for a saddle-type vehicle (1) mounted on a body frame (10) in which a down frame (14) extends downward from a head pipe (11), and includes a cylinder head (43) in which an exhaust port (47) is formed, an exhaust pipe (70) connected to the exhaust port of the cylinder head, and an exhaust gas sensor (first oxygen sensor 84) attached to the exhaust pipe, the exhaust pipe extending downward through one side of the down frame, crossing the front of the down frame, and then extending upward through the other side of the down frame, and a part of the exhaust pipe crossing the down frame is a straight section (73), and the exhaust gas sensor is attached to the straight section and overlaps the down frame from the front. According to this configuration, the exhaust gas sensor is attached to the straight section in which the flow of exhaust gas is less biased, and the exhaust gas sensor overlaps the down frame from the front and is approximately perpendicular to the straight section. The detection end of the exhaust gas sensor is directed approximately perpendicular to the flow of exhaust gas, thereby improving detection accuracy. In addition, the straight section of the exhaust pipe sways less than the bent section, so the exhaust gas sensor is stably supported, and the exhaust gas sensor is positioned on the inside in the vehicle width direction, reducing the risk of damage to the exhaust gas sensor when the vehicle rolls over. Also, by routing the lead wires of the exhaust gas sensor along the down frame, the lead wires can be prevented from swaying, reducing the risk of damage to the lead wires.

[0051] In the second aspect, in the first aspect, the exhaust gas sensor extends vertically so as to be parallel to the down frame in a front view, and is positioned inside both side surfaces of the down frame in the engine width direction. With this configuration, the exhaust gas sensor is attached approximately perpendicular to the straight portion of the exhaust pipe, which can further improve detection accuracy. The lead wires of the exhaust gas sensor can be easily routed along the down frame.

[0052] In the third aspect, in the first and second aspects, the axis of the exhaust gas sensor is tilted upward so as to approach the axis of the down frame in a side view. With this configuration, the risk of damage due to a collision with a flying stone or the like from the front is reduced by tilting the first oxygen sensor rearward. The lead wire of the exhaust gas sensor can be easily aligned along the down frame, and by routing the lead wire along the down frame, swinging of the lead wire can be suppressed.

[0053] In a fourth aspect, in any one of the first to third aspects, the exhaust gas sensor is located inside both ends of the straight section in the front-rear direction in a side view. With this configuration, the exhaust gas sensor does not protrude from the straight section in the front or rear, so a gap is secured between the exhaust gas sensor and the down frame or the front wheel, and there is no need to extend the wheelbase to install the exhaust gas sensor.

[0054] In a fifth aspect, in any one of the first to fourth aspects, the exhaust gas sensor overlaps an exhaust pipe passing through both sides of the down frame in a side view. With this configuration, the exhaust gas sensor is protected from both sides by the exhaust pipe, and the risk of damage to the exhaust gas sensor due to the vehicle tipping over or the like can be reduced.

[0055] In a sixth aspect, in any one of the first to fifth aspects, a catalyst (primary catalyst 81) is accommodated in the exhaust pipe on the other side of the down frame, and the catalyst overlaps the exhaust gas sensor in a side view. With this configuration, the catalyst is brought close to the exhaust gas sensor, and the heat of the catalyst can be used to activate the exhaust gas sensor early, thereby improving detection accuracy.

[0056] A seventh aspect is any one of the first to sixth aspects, in which a guard member (83) protrudes from the straight portion and covers the exhaust gas sensor from the front. With this configuration, the exhaust gas sensor is covered from the front by the guard member, and thus the exhaust gas sensor is protected by the guard member, thereby reducing the risk of damage.

[0057] In the eighth aspect, in the seventh aspect, the guard member protrudes vertically from the straight portion in a side view, and the exhaust gas sensor is tilted upward so as to move away from the guard member. With this configuration, the exhaust gas sensor is farther away from the guard member toward the top, so that even if the guard member is hit by a flying stone or the like and deformed, the effect on the exhaust gas sensor is suppressed. The gap between the exhaust gas sensor and the guard member makes it easier to install the exhaust gas sensor and to route the lead wires.

[0058] 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.

[0059] 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]

[0060] 1: Saddle-type vehicle 10: Body frame 11: Head pipe 14: Down frame 40: Engine 43: Cylinder head 47: Exhaust port 70: Exhaust pipe 72: Expanded pipe 73: Straight section 74: Primary catalyst case 81: Primary catalyst (catalyst) 83: Guard material 84: First oxygen sensor (exhaust gas sensor)

Claims

1. An engine for a saddle-type vehicle mounted on a body frame having a down frame extending downward from a head pipe, A cylinder head having an exhaust port; an exhaust pipe connected to an exhaust port of the cylinder head; an exhaust gas sensor attached to the exhaust pipe; the exhaust pipe extends downward through one side of the down frame, crosses a front of the down frame, and then extends upward through the other side of the down frame, A part of the exhaust pipe that crosses the down frame is a straight section, The engine is characterized in that the exhaust gas sensor is attached to the straight portion and overlaps the down frame from the front.

2. 2. The engine according to claim 1, wherein, in a front view, the exhaust gas sensor extends vertically so as to be parallel to the down frame, and the exhaust gas sensor is located inside both side surfaces of the down frame in the engine width direction.

3. 3. The engine according to claim 1, wherein an axis of the exhaust gas sensor is inclined upwardly so as to approach an axis of the down frame in a side view.

4. 3. The engine according to claim 1, wherein the exhaust gas sensor is located inwardly of both ends of the straight portion in the front-rear direction in a side view.

5. 3. The engine according to claim 1, wherein the exhaust gas sensor overlaps the exhaust pipe passing through both sides of the down frame in a side view.

6. A catalyst is accommodated in the exhaust pipe on the other side of the down frame, 3. The engine according to claim 1, wherein the catalyst overlaps the exhaust gas sensor in a side view.

7. A guard member protrudes from the straight portion, 3. The engine according to claim 1, wherein the exhaust gas sensor is covered from the front by the guard member.

8. 8. The engine according to claim 7, wherein, in a side view, the guard member protrudes vertically from the straight portion, and the exhaust gas sensor is inclined upward and away from the guard member.

Images