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 saddle-ride-type vehicle. The engine includes a cylinder (42) and a cylinder head (43) overlapped on a crankcase (41), an exhaust pipe (70) extending through a side of the cylinder from the cylinder head, an exhaust gas sensor (86) attached to the exhaust pipe on the side of the cylinder, and a radiator (51) located in front of the cylinder head. The exhaust gas sensor is covered by the radiator from the front side.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] Known engines for saddle-ride type vehicles have an exhaust pipe that passes along the side of the cylinder (see, for example, Patent Document 1). In the engine described in Patent Document 1, a cylinder is mounted on a crankcase, and a cylinder head is mounted 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 upward and extends to the cylinder, passing along the side of the cylinder to the rear of the vehicle. Having the exhaust pipe pass along the side of the cylinder ensures the minimum ground clearance of the saddle-ride type vehicle. [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 depending on the location of the exhaust gas sensor, the exhaust gas sensor may be exposed to the outside, increasing the risk of damage.

[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 mounted on a saddle-type vehicle, and comprises a cylinder and cylinder head stacked on top of a crankcase, an exhaust pipe extending from the cylinder head through the side of the cylinder, an exhaust gas sensor attached to the exhaust pipe on the side of the cylinder, and a radiator positioned in front of the cylinder head, and the above-mentioned problem is solved by the exhaust gas sensor being covered from the front by the radiator. Effect of the Invention

[0007] According to the engine of one aspect of the present invention, the exhaust gas sensor is attached to the exhaust pipe on the side of the cylinder, which makes it easier to ensure the minimum ground clearance of the saddle-type vehicle. Also, even if the exhaust gas sensor is attached to the exhaust pipe, the exhaust gas sensor is covered from the front by the radiator, so that the exhaust gas sensor is protected by the radiator and the risk of damage can be reduced. [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 front view of the periphery of a second oxygen sensor of the present embodiment. [Figure 6] FIG. 4 is a right side view of the periphery of the second oxygen sensor of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An engine according to one aspect of the present invention is mounted on a saddle-type vehicle, with a cylinder and a cylinder head stacked on top of a crankcase. An exhaust pipe extends from the cylinder head through the side of the cylinder, and an exhaust gas sensor is attached to the exhaust pipe on the side of the cylinder. A radiator is positioned in front of the cylinder head, and the exhaust gas sensor is covered by the radiator from the front. By attaching the exhaust gas sensor to the exhaust pipe on the side of the cylinder, it becomes easier to ensure the minimum ground clearance of the saddle-type vehicle. Furthermore, even if the exhaust gas sensor is attached to the exhaust pipe, the exhaust gas sensor is covered by the radiator from the front, so that the exhaust gas sensor is protected by the radiator and the risk of damage can be reduced. 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 particular, in the saddle-type vehicle 1 of this embodiment, in order to ensure minimum ground clearance, the exhaust pipe 70 on the downstream side of the primary catalyst case 74 passes through the side of the cylinder 42 and extends rearward. Because the exhaust pipe 70 is exposed at the side of the cylinder 42, providing an oxygen sensor in this location increases the risk of damage. Therefore, in this embodiment, the risk of damage is reduced by covering the oxygen sensor using peripheral parts such as a radiator and by adjusting the mounting direction of the oxygen sensor.

[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 (lower 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 (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 expansion pipe 72, and a first oxygen 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 also 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 (accommodating section) 74 and the reduced diameter pipe (reduced diameter section) 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 accommodated 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 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 (exhaust gas 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, the cylinder head 43, the inlet hose 62, and the 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 second oxygen sensor will be described in detail with reference to Figures 5 and 6. Figure 5 is a front view of the second oxygen sensor and its periphery in this embodiment. Figure 6 is a right side view of the second oxygen sensor and its periphery in this embodiment. In Figure 5, the right radiator is indicated by a two-dot chain line.

[0031] As shown in Fig. 5, the right radiator 51 and the left radiator 55 are attached to the down frame 14 via the radiator mount 24. The exhaust pipe 70 passes below the right radiator 51, and a second oxygen sensor 86 is attached to the exhaust pipe 70 (reduced diameter pipe 75) on the side of the cylinder 42. The second oxygen sensor 86 is covered from the front by the right radiator 51. More specifically, the base end side of the second oxygen sensor 86 is covered from the front by the right inlet tank 52 of the right radiator 51. The second oxygen sensor 86 does not obstruct the exhaust air of the right radiator 51, and the second oxygen sensor 86 is protected by the highly rigid tank.

[0032] The base end of the second oxygen sensor 86 faces inward in the vehicle width direction, and the second oxygen sensor 86 overlaps the cylinder head 43 in a front view. The second oxygen sensor 86 is located inside the exhaust pipe 70, thereby reducing the risk of damage to the second oxygen sensor 86. In particular, the second oxygen sensor 86 is less likely to hit the ground when the vehicle rolls over. Even if the second oxygen sensor 86 is installed in a relatively high position, the second oxygen sensor 86 is hidden by the exhaust pipe 70 and is less noticeable. The primary catalyst 81 (see FIG. 6) is located below the right radiator 51, and the second oxygen sensor 86 is located behind the right radiator 51, thereby bringing the right radiator 51, the primary catalyst 81, and the second oxygen sensor 86 close to each other, resulting in a compact vehicle.

[0033] 6, the right radiator 51 is provided in front of the cylinder head 43, and the second oxygen sensor 86 is located between the cylinder head 43 and the right radiator 51 (right inlet tank 52) in a side view. By positioning the second oxygen sensor 86 in the empty space between the cylinder head 43 and the right radiator 51, an appropriate gap is provided between the second oxygen sensor 86 and surrounding components. As described above, the base end of the second oxygen sensor 86 is directed toward the inside in the vehicle width direction, and the second oxygen sensor 86 fits into the gap between the cylinder head 43 and the right radiator 51, so that exposure of the second oxygen sensor 86 is suppressed and the risk of damage is reduced.

[0034] An inlet hose 62 extends from the right inlet tank 52, and the second oxygen sensor 86 is covered from above by the inlet hose 62. The second oxygen sensor 86 is protected by the inlet hose 62, reducing the risk of damage. In this manner, the second oxygen sensor 86 is covered from the front by the right inlet tank 52, covered from the rear by the cylinder head 43, covered from the right side by the reduced diameter pipe 75, and covered from above by the inlet hose 62. This prevents the second oxygen sensor 86 from being exposed, and the second oxygen sensor 86 is protected from flying objects such as flying stones by the surrounding components.

[0035] In side view, the reduced diameter pipe 75 is divided into upper and lower parts by extending the extension line L of the lower edge of the downstream pipe 76 forward. The second oxygen sensor 86 is attached to the upper area of ​​the reduced diameter pipe 75, and the second oxygen sensor 86 is not attached to the lower area of ​​the reduced diameter pipe 75. In the upper area of ​​the reduced diameter pipe 75, the diameter of the reduced diameter pipe 75 is narrowed, thereby increasing the flow velocity of the exhaust gas, improving the exchange performance of the exhaust gas, and reducing the bias of the exhaust gas flow. For this reason, the detection end of the second oxygen sensor 86 is positioned in the upper area of ​​the reduced diameter pipe 75, improving the detection accuracy.

[0036] As described above, according to the engine 40 of this embodiment, the second oxygen sensor 86 is attached to the exhaust pipe 70 on the side of the cylinder 42, which makes it easier to ensure the minimum ground clearance of the saddle riding type vehicle 1. Furthermore, even if the second oxygen sensor 86 is attached to the exhaust pipe 70, the right radiator 51 covers the second oxygen sensor 86 from the front, so that the second oxygen sensor 86 is protected by the right radiator 51 and the risk of damage can be reduced.

[0037] 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.

[0038] 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.

[0039] In this embodiment, the second oxygen sensor as the exhaust gas sensor is attached to the reduced diameter pipe, but the exhaust gas sensor may be attached to the exhaust pipe on the side of the cylinder. For example, the exhaust gas sensor may be attached to the downstream pipe.

[0040] 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.

[0041] 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.

[0042] Further, in this embodiment, the engine is provided with a right radiator and a left radiator as radiators, but the engine may be provided with a single radiator.

[0043] Moreover, the exhaust pipe in this embodiment may be a single pipe or a double pipe.

[0044] 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.

[0045] As described above, the first aspect is an engine (40) mounted on a saddle-type vehicle (1), and includes a cylinder (42) and a cylinder head (43) stacked on top of a crankcase (41), an exhaust pipe (70) extending from the cylinder head through the side of the cylinder, an exhaust gas sensor (second oxygen sensor 86) attached to the exhaust pipe on the side of the cylinder, and a radiator (right radiator 51) positioned in front of the cylinder head, and the exhaust gas sensor is covered from the front by the radiator. According to this configuration, the exhaust gas sensor is attached to the exhaust pipe on the side of the cylinder, which makes it easier to ensure the minimum ground clearance of the saddle-type vehicle. Also, even if the exhaust gas sensor is attached to the exhaust pipe, the exhaust gas sensor is covered from the front by the radiator, so that the exhaust gas sensor is protected by the radiator and the risk of damage can be reduced.

[0046] In the second embodiment, the radiator in the first embodiment has a radiator core (right radiator core 53) that dissipates heat of the coolant into the air, and tanks (right inlet tank 52, right outlet tank 54) on both the upper and lower sides of the radiator core, and the exhaust gas sensor is covered from the front by the lower tank. With this configuration, the exhaust gas sensor does not obstruct the exhaust air of the radiator, and the exhaust gas sensor can be protected by the rigid lower tank.

[0047] In the third aspect, in the first and second aspects, the exhaust gas sensor is located between the cylinder head and the radiator in a side view. With this configuration, the exhaust gas sensor is located in the empty space between the radiator and the cylinder head, so that an appropriate gap can be provided between the exhaust gas sensor and surrounding components. In addition, the exhaust gas sensor fits into the gap, so that the exposure of the exhaust gas sensor is suppressed, and the risk of damage can be reduced.

[0048] In a fourth aspect, in any one of the first to third aspects, the base end of the exhaust gas sensor is directed toward the inside in the vehicle width direction, and the exhaust gas sensor overlaps the cylinder head in a front view. With this configuration, the exhaust gas sensor is located inside the exhaust pipe, thereby reducing the risk of damage to the exhaust gas sensor. In particular, the exhaust gas sensor is less likely to collide with the ground when the vehicle rolls over. Even if the exhaust gas sensor is installed at a relatively high position, it is hidden by the exhaust pipe and is less noticeable.

[0049] In a fifth aspect, in any one of the first to fourth aspects, the exhaust pipe has an accommodation section (primary catalyst case 74) that accommodates the catalyst below the radiator, and a reduced diameter section (reduced diameter pipe 75) that reduces in diameter from the accommodation section downstream, the reduced diameter section is curved, and the exhaust gas sensor is attached downstream of the reduced diameter section. With this configuration, since the exhaust gas sensor is located downstream of the reduced diameter pipe, even if the reduced diameter pipe is curved, the exhaust gas is not likely to hit the detection end of the exhaust gas sensor, and detection accuracy is not impaired. By installing the catalyst below the radiator, the radiator, catalyst, and exhaust gas sensor are close to each other, and the saddle-type vehicle is formed compactly.

[0050] In the sixth embodiment, a cooling water hose (inlet hose 62) extends from the lower tank in the second embodiment, and the exhaust gas sensor is covered from above by the hose. With this configuration, the exhaust gas sensor is covered from above by the hose, so that the exhaust gas sensor is protected by the hose and the risk of damage can be reduced.

[0051] In the seventh aspect, in the second aspect, the radiator has a shroud (66) that covers the back surface of the radiator core, and the lead wire (second lead wire 87) extending from the base end of the exhaust gas sensor is held by the shroud. With this configuration, even if the exhaust gas sensor is installed to the side of the cylinder, the lead wire is held by the shroud, so that swinging of the lead wire can be suppressed.

[0052] 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.

[0053] 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]

[0054] 1: Saddle-type vehicle 40: Engine 41: Crankcase 42: Cylinder 43: Cylinder head 51: Right radiator (radiator) 52: Right inlet tank (lower tank) 53: Right radiator core (radiator core) 62: Inlet hose (hose) 66: Shroud 70: Exhaust pipe 74: Primary catalyst case (housing section) 75: Reducing diameter pipe (expanding part) 81: Primary catalyst (catalyst) 82: Secondary catalyst 86: Second oxygen sensor (exhaust gas sensor) 87: Second lead (lead)

Claims

1. An engine mounted on a saddle-type vehicle, A cylinder and a cylinder head are stacked on top of the crankcase; an exhaust pipe extending from the cylinder head through a side of the cylinder; an exhaust gas sensor attached to the exhaust pipe on a side of the cylinder; a radiator positioned in front of the cylinder head, An engine characterized in that the exhaust gas sensor is covered from the front by the radiator.

2. The radiator includes a radiator core that radiates heat of the coolant into the air, and tanks on both upper and lower sides of the radiator core.

2. An engine according to claim 1, wherein the exhaust gas sensor is covered from the front by a lower tank.

3. 3. The engine according to claim 1, wherein the exhaust gas sensor is located between the cylinder head and the radiator in a side view.

4. A base end of the exhaust gas sensor is directed toward an inner side in a vehicle width direction, 3. The engine according to claim 1, wherein the exhaust gas sensor overlaps with the cylinder head in a front view.

5. the exhaust pipe has an accommodation portion that accommodates a catalyst below the radiator, and a reduced diameter portion that reduces in diameter downstream from the accommodation portion, 3. The engine according to claim 1, wherein the reduced diameter portion is curved, and the exhaust gas sensor is attached downstream of the reduced diameter portion.

6. 3. The engine according to claim 2, wherein a cooling water hose extends from the lower tank, and the exhaust gas sensor is covered from above by the hose.

7. The radiator has a shroud that covers a back surface of the radiator core, 3. The engine according to claim 2, wherein a lead wire extending from a base end of said exhaust gas sensor is held in said shroud.

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