engine

Abstract

To improve the assembly ease and protection performance of an exhaust gas sensor in a model in which an exhaust pipe crosses in front of a cylinder. [Solution] An engine (31) for a saddle-ride type vehicle is mounted on a body frame (10) having a down frame (14) extending downward from a head pipe (11). The engine is provided with a cylinder (33) located rearward of the down frame, a cylinder head (34) mounted on the upper surface of the cylinder, an exhaust pipe (61) extending rearward from the cylinder head, and an exhaust gas sensor (71) for detecting predetermined characteristics in the exhaust gas. The exhaust pipe extends downward through one side of the down frame, crosses in front of the down frame, and then extends upward through the other side of the down frame. The exhaust gas sensor is installed on the rear side of the exhaust pipe on one side of the down frame and is located outboard of the cylinder in the vehicle width direction when viewed from the front.

Description

[Technical Field]

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

[0002] A known engine for a saddle-ride vehicle is one in which the exhaust pipe is curved in a U-shape in front of the down frame (see, for example, Patent Document 1). The engine described in Patent Document 1 has a cylinder mounted on a crankcase, and a cylinder head mounted on the cylinder. An exhaust port is formed in the front of the cylinder head, and the exhaust pipe extends downward from the exhaust port toward the crankcase. In front of the crankcase, the exhaust pipe curves upward in a U-shape and extends to the cylinder, then passes beside the cylinder and extends 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] An exhaust gas sensor is attached to the exhaust pipe, but if the exhaust pipe is bent in a U-shape like the one in Patent Document 1, it becomes difficult to assemble the exhaust gas sensor in front of the engine and to route the lead wires of the exhaust gas sensor. Furthermore, if the position of the exhaust gas sensor is determined with ease of assembly in mind, there is a risk that the exhaust gas sensor will be damaged by foreign objects such as flying stones.

[0005] The present invention has been made in consideration of the above points, and aims to provide an engine that can improve the assembly ease and protective performance of an exhaust gas sensor in models in which the exhaust pipe crosses in front of the cylinder. [Means for solving the problem]

[0006] An engine of one aspect of the present invention is an engine for a saddle-ride vehicle mounted on a body frame in which a down frame extends downward from a head pipe, and comprises a cylinder located rearward of the down frame, a cylinder head installed on the upper surface of the cylinder, an exhaust pipe extending rearward from the cylinder head, and an exhaust gas sensor that detects predetermined characteristics in the exhaust gas, wherein the exhaust pipe extends downward through one side of the down frame, crosses in front of the down frame, and then extends upward through the other side of the down frame, and the exhaust gas sensor is installed on the rear side of the exhaust pipe on one side of the down frame and is positioned outward in the vehicle width direction from the cylinder when viewed from the front, thereby solving the above problem. [Effects of the Invention]

[0007] According to an engine of one aspect of the present invention, the exhaust gas sensor is installed in the space to the side of the cylinder, which improves the ease of installation of the exhaust gas sensor and facilitates the routing of the exhaust gas sensor lead wires. Furthermore, the exhaust gas sensor is installed on the rear side of the exhaust pipe, and the exhaust pipe extends from one side to the other of the down frame below the exhaust gas sensor, so that the exhaust gas sensor can be protected from foreign objects such as flying stones by the exhaust pipe. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a left side view of a saddle-ride type vehicle according to an embodiment of the present invention; [Figure 2] FIG. 2 is a left side view of the engine and its surroundings according to the present embodiment. [Figure 3] FIG. 2 is a front view of the engine and its surroundings according to the present embodiment. [Figure 4] FIG. 2 is a front view of the first oxygen sensor and its surroundings according to the present embodiment. [Figure 5] FIG. 2 is a bottom view of the engine and its surroundings according to the present embodiment. [Figure 6] FIG. 2 is a left side view of the first oxygen sensor and its surroundings according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An engine according to one aspect of the present invention is mounted on a body frame of a saddle-ride type vehicle. A down frame extends downward from a head pipe of the body frame, and a cylinder of the engine is positioned rearward of the down frame. A cylinder head is installed on the upper surface of the cylinder, and an exhaust pipe extends from the cylinder head toward the rear of the vehicle. 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. An exhaust gas sensor is installed in the exhaust pipe to detect a predetermined characteristic of the exhaust gas. The exhaust gas sensor is installed on one side of the down frame, behind the exhaust pipe, and is located outward in the vehicle width direction from the cylinder in a front view. Installing the exhaust gas sensor using the space to the side of the cylinder improves the assembly of the exhaust gas sensor and facilitates the routing of the exhaust gas sensor lead wires. Furthermore, because the exhaust gas sensor is installed on the rear side of the exhaust pipe and the exhaust pipe extends from one side of the down frame to the other below the exhaust gas sensor, the exhaust pipe can protect the exhaust gas sensor from foreign objects such as flying stones. [Example]

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

[0011] As shown in Fig. 1, a saddle-type vehicle 1 is configured by mounting various parts such as an engine 31 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 of the body frame 10, and the rear portions of the pair of main frames 12 bend downward to form a pair of body frames 13. In addition, down frames 14 extend downward from the head pipe 11, and under loops 15 bent rearward are connected to the lower portions of the down frames 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 21 is steerably supported on the head pipe 11 via a steering shaft (not shown). Handlebars 22 are provided on the upper part of the front fork 21, and a front wheel 23 is rotatably supported on the lower part of the front fork 21. A fuel tank 24 is placed on the upper part of the pair of main frames 12, and the main frames 12 and fuel tank 24 are covered from the sides by front side covers 25. A seat 26 is installed behind the fuel tank 24, and a seat frame (not shown) that supports the seat 26 from below is covered from the sides by a rear side cover 27.

[0013] A swing arm 28 is swingably supported by the body frame 13. The swing arm 28 extends rearward from the body frame 13, and a rear wheel 29 is rotatably supported at the rear end of the swing arm 28. The engine 31 is a four-stroke single-cylinder engine, and is suspended inside the body frame 10 via multiple suspension brackets 16, 17. A cylinder assembly, which is made up of a stacked cylinder 33, a cylinder head 34, and a cylinder head cover 35, is attached to the upper surface of a crankcase 32 of the engine 31. An air cleaner (not shown) is installed behind the cylinder head 34.

[0014] Left and right radiators 41, 42 (only the right radiator 41 is shown in FIG. 1) are located in front of the cylinder head 34, and the left and right radiators 41, 42 are attached to the down frame 14. An exhaust pipe 61 extends downward from the front left side of the cylinder head 34, passes along the right side of the cylinder 33, and is connected to a muffler 62 at the rear of the vehicle. A primary catalyst case 63 is formed in the exhaust pipe 61 in front of the engine 31, and a secondary catalyst case 64 is formed in the exhaust pipe 61 in the rear of the engine 31. A primary catalyst 65 (see FIG. 3) is housed in the primary catalyst case 63, and a secondary catalyst (not shown) is housed in the secondary catalyst case 64.

[0015] An oxygen sensor needs to be installed in the exhaust pipe 61 upstream of the primary catalyst 65, but the ease of installation and protective performance of the oxygen sensor must be considered. If the oxygen sensor is installed on the rear part of the exhaust pipe 61 in front of the engine 31, the protective performance of the oxygen sensor is ensured, but there is not enough space between the engine 31 and the exhaust pipe 61, making the installation of the oxygen sensor difficult. If the oxygen sensor is installed on the upper side of the exhaust pipe 61 in front of the engine 31, for example, the ease of installation of the oxygen sensor is improved, but a dedicated guard member is required to ensure protective performance. Therefore, in this embodiment, the oxygen sensor is installed on the rear side of the exhaust pipe 61, utilizing the available space on the side of the cylinder 33.

[0016] The peripheral structure of the engine will be described with reference to Figures 2 and 3. Figure 2 is a left side view of the engine and its periphery in this embodiment. Figure 3 is a front view of the engine and its periphery in this embodiment.

[0017] As shown in Figure 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 19. Below the bridge tube 19, an engine 31 is suspended from the body frame 10 by suspension brackets 16 and 17. A magneto cover 36 is installed on the left side of a crankcase 32 of the engine 31, and a sprocket cover 37 is installed behind the magneto cover 36. A clutch cover 38 (see Figure 3) is installed on the right side of the crankcase 32, and a water pump 39 (see Figure 3) is installed in front of the clutch cover 38.

[0018] A cylinder 33 is installed on the upper surface of the crankcase 32, a cylinder head 34 is installed on the upper surface of the cylinder 33, and a cylinder head cover 35 is installed on the upper surface of the cylinder head 34. The crankcase 32, cylinder 33, cylinder head 34, and cylinder head cover 35 are positioned rearward of the down frame 14, and the front of the crankcase 32 is supported by a suspension bracket 16 attached to the down frame 14. First and second engine guards 75, 76 are installed inside and on the left side of the underloop 15 below the engine 31. The first and second engine guards 75, 76 protect the engine 31 from foreign objects such as flying stones.

[0019] 2 and 3, a right radiator 41 and a left radiator 42 are installed in front of the cylinder head 34, on either side of the down frame 14 in the center of the vehicle. The right radiator 41 is formed larger than the left radiator 42. The right radiator 41 has a right inlet tank 44 installed below the right radiator core 43, and a right outlet tank 45 installed above the right radiator core 43. The left radiator 42 has a left inlet tank 47 installed above the left radiator core 46, and a left outlet tank 48 installed below the left radiator core 46.

[0020] A thermostat cover 51 is provided on the front of the engine 31, and a thermostat (not shown) is installed inside the thermostat cover 51. The right inlet tank 44 is connected to the thermostat cover 51 via an inlet hose 52. The right outlet tank 45 and the left inlet tank 47 are connected via a radiator hose 53. The left outlet tank 48 is connected to the water pump 39 via an outlet hose (radiator hose) 55. The top of the thermostat cover 51 is connected to the right outlet tank 45 via an air bleeding hose (not shown).

[0021] In the right radiator 41, the coolant flows upward from the right inlet tank 44 to the right outlet tank 45, and the heat of the coolant is radiated into the air as the coolant passes through the right radiator core 43. The coolant is sent from the right outlet tank 45 to the left inlet tank 47 through the radiator hose 53. In the left radiator 42, the coolant flows downward from the left inlet tank 47 to the left outlet tank 48, and the heat of the coolant is radiated into the air as the coolant passes through the left radiator core 46. The coolant radiates heat in two stages, in the right radiator 41 and the left radiator 42, improving cooling efficiency.

[0022] An intermediate portion of the cylinder head 34 and the outlet hose 55 is connected via a bypass hose (not shown). The bypass hose forms a bypass passage that returns the cooling water from the cylinder head 34 (upstream of the thermostat) to the water pump 39, bypassing the right radiator 41 and the left radiator 42. While the cooling water temperature is below a predetermined temperature, the thermostat closes, and the cooling water is returned from the cylinder head 34 to the water pump 39 through the bypass hose. When the cooling water temperature reaches or exceeds the predetermined temperature, the thermostat opens, and the cooling water also flows through the right radiator 41 and the left radiator 42 to cool the engine 31.

[0023] An exhaust port 67 facing diagonally downward and to the left is formed in the front surface of the cylinder head 34, and an exhaust pipe 61 is connected to the exhaust port 67. The exhaust pipe 61 extends downward from the exhaust port 67, passing along the left side of the down frame 14, crosses the front of the down frame 14, and then extends upward along the right side of the down frame 14. The exhaust pipe 61 is curved in a U-shape using the space in front of the vehicle body, and the radius of curvature of the curved portion of the exhaust pipe 61 is increased, thereby reducing exhaust resistance. The exhaust pipe 61 also extends rearward, passing along the right side of the cylinder 33, and the rear end of the exhaust pipe 61 is connected to a muffler 62 (see FIG. 1) near the seat 26.

[0024] The exhaust pipe 61 in front of the engine 31 is formed in a U-shape by connecting an upstream pipe 68 and a primary catalyst case 63. The upstream pipe 68 extends diagonally downward and left from an exhaust port 67 and then makes a large curve to the right, crossing the front of the down frame 14. The upstream end (lower end) of the primary catalyst case 63 is located forward of the down frame 14, and the primary catalyst case 63 extends diagonally upward and right from the downstream end of the upstream pipe 68. A primary catalyst 65 is housed inside the primary catalyst case 63, and air pollutants in the exhaust gas are purified as the exhaust gas passes through the primary catalyst 65. A downstream pipe 69 (see FIG. 2) extends rearward from the downstream end of the primary catalyst case 63.

[0025] A first oxygen sensor 71 is installed on the rear side of the upstream pipe 68 when viewed from the front, and a second oxygen sensor 77 is installed on the left side of the primary catalyst case 63. The first oxygen sensor 71 detects the oxygen concentration in the exhaust gas before it passes through the primary catalyst 65, and the second oxygen sensor 77 detects the oxygen concentration in the exhaust gas after it has passed through the primary catalyst 65. The detection result of the first oxygen sensor 71 is used for feedback control of the fuel injection amount, and the detection result of the second oxygen sensor 77 is used for diagnosing catalyst deterioration. Lead wires 72 (only one is shown) extend upward from the rear ends of the first oxygen sensor 71 and the second oxygen sensor 77.

[0026] The layout of the first oxygen sensor will be described in detail with reference to Figures 4 to 6. Figure 4 is a front view of the first oxygen sensor and its periphery in this embodiment. Figure 5 is a bottom view of the engine and its periphery in this embodiment. Figure 6 is a left side view of the first oxygen sensor and its periphery in this embodiment. Note that in Figure 4, the upstream pipe is indicated by a dashed line for ease of explanation.

[0027] 4, an upstream pipe 68 extends diagonally downward to the left from an exhaust port 67 of the cylinder head 34, and a first oxygen sensor 71 is installed on the rear side of the upper portion of the upstream pipe 68 on the left side (one side) of the down frame 14. In a front view, the entire first oxygen sensor 71 overlaps the upstream pipe 68, and the first oxygen sensor 71 is covered from the front by the upstream pipe 68, thereby protecting the first oxygen sensor 71 from foreign objects such as flying stones from the front. Because the upstream pipe 68 extends in the vehicle width direction below the first oxygen sensor 71, foreign objects flying from below are less likely to hit the first oxygen sensor 71.

[0028] In a front view, the first oxygen sensor 71 is located outboard (on the left side) of the cylinder 33 in the vehicle width direction, and the first oxygen sensor 71 overlaps the magneto cover 36. There is an empty space to the side of the cylinder 33 and in front of the magneto cover 36, and this empty space is used to install the first oxygen sensor 71. Securing sufficient working space to the side of the engine 31 improves the ease of assembling the first oxygen sensor 71 and also makes it easier to route the lead wire 72 of the first oxygen sensor 71. The lead wire 72 extends upward, passing behind the outlet hose 55 of the left radiator 42.

[0029] A portion of the upstream pipe 68 downstream of the first oxygen sensor 71 extends to the outside in the vehicle width direction beyond the first oxygen sensor 71 on the left side of the down frame 14, and then curves back to the right side of the down frame 14. In addition, the outer surface of the magneto cover 36 is located to the left of the leftmost position (the outermost position on one side) of the upstream pipe 68, and the outer surface of the left radiator 42 is located to the left of the outer surface of the magneto cover 36. In the event of a fall to the left, the left radiator 42, magneto cover 36, and upstream pipe 68 hit the ground before the first oxygen sensor 71, thereby preventing damage to the first oxygen sensor 71.

[0030] A first oxygen sensor 71 is installed in the upstream pipe 68 on the left side of the down frame 14, and a primary catalyst 65 is installed in the primary catalyst case 63 on the right side of the down frame 14. In a left side view, the first oxygen sensor 71 overlaps the down frame 14 (see FIG. 6), and in a right side view, the primary catalyst 65 overlaps the down frame 14. By separating the primary catalyst 65 and the first oxygen sensor 71 by the down frame 14, the hot air flowing from the primary catalyst 65 toward the first oxygen sensor 71 is blocked by the down frame 14. By installing the primary catalyst 65 on the opposite side of the down frame 14 from the first oxygen sensor 71, the degree of freedom in installing the first oxygen sensor 71 is improved.

[0031] 4 and 5, the outlet hose 55 extends rearward from the left radiator 42, and then extends toward the right side of the down frame 14. The first oxygen sensor 71 is located below the outlet hose 55 in a front view, and is covered from above by the outlet hose 55, thereby protecting the first oxygen sensor 71 from foreign matter entering from above. Because the left radiator 42 and the outlet hose 55 are located above the first oxygen sensor 71, the left radiator 42 and the outlet hose 55 do not impair the ease of assembly of the first oxygen sensor 71.

[0032] Furthermore, the first oxygen sensor 71 is installed in a space surrounded by the upstream pipe 68, the outlet hose 55, and the underloop 15 when viewed from below. In this case, when viewed from below, the upstream pipe 68 is located in front of the first oxygen sensor 71, the outlet hose 55 is located to the left and rear of the first oxygen sensor 71, and the underloop 15 is located to the right of the first oxygen sensor 71. Because the outlet hose 55 is located to the left of the first oxygen sensor 71, in the event of a fall to the left, the outlet hose 55 hits the ground before the first oxygen sensor 71, thereby preventing damage to the first oxygen sensor 71.

[0033] As described above, the plate-shaped first engine guard 75 is attached to the inside of the under-loop 15, and the plate-shaped second engine guard 76 is attached to the left side of the under-loop 15. The first engine guard 75 extends in the front-to-rear direction so as to cover the crankcase 32 from below, and the second engine guard 76 extends in the front-to-rear direction so as to cover the magneto cover 36 from below. In a bottom view, the rear end of the first oxygen sensor 71 overlaps the second engine guard 76, and the first oxygen sensor 71 is covered from below by the second engine guard 76, so that the first oxygen sensor 71 is protected from foreign objects from below the engine 31.

[0034] As shown in FIG. 6, a base 73 that bulges rearward is provided on the back side of the upstream pipe 68, and a first oxygen sensor 71 is mounted on a boss 74 provided on this base 73. The bulge of the base 73 increases the cross-sectional area of ​​the upstream pipe 68, minimizing the effect of pressure loss caused by the protruding tip of the first oxygen sensor 71. The detection accuracy of the first oxygen sensor 71 is ensured even if the upstream pipe 68 has many bends. Because the boss 74 is not provided directly on the upstream pipe 68, there is no need to process the boss shape to fit the pipe shape in order to reduce pressure loss. By providing the boss 74 on the base 73, the boss shape can be made simple cylindrical, reducing costs.

[0035] As described above, the down frame 14 is provided with the approximately triangular suspension bracket 16, and the first oxygen sensor 71 overlaps the suspension bracket 16 in a side view. Because space is provided on the side of the suspension bracket 16 in consideration of ease of assembly of the engine 31, the first oxygen sensor 71 can be easily installed relative to the upstream pipe 68 on the left side of the suspension bracket 16. As most of the first oxygen sensor 71 is covered from the right side by the suspension bracket 16, the first oxygen sensor 71 is protected from foreign matter from the right side of the down frame 14, and the suspension bracket 16 blocks hot air heading from the primary catalyst 65 toward the first oxygen sensor 71.

[0036] As described above, according to the engine 31 of this embodiment, the first oxygen sensor 71 is installed using the space to the side of the cylinder 33, which improves the ease of assembly of the first oxygen sensor 71 and facilitates the routing of the lead wires 72 of the first oxygen sensor 71. Furthermore, since the first oxygen sensor 71 is installed on the rear side of the exhaust pipe 61 and the exhaust pipe 61 extends from one side to the other side of the down frame 14 below the first oxygen sensor 71, the exhaust pipe 61 can protect the first oxygen sensor 71 from foreign objects such as flying stones.

[0037] 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 that can detect 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.

[0038] 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.

[0039] Furthermore, 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.

[0040] Furthermore, 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.

[0041] The engine of this embodiment is not limited to the off-road straddle-type vehicle described above, and may be used in other types of straddle-type vehicles. Note that the term "saddle-type vehicle" is not limited to vehicles in general in which the rider sits astride a seat, but also includes scooter-type vehicles in which the rider does not sit astride a seat.

[0042] As described above, the first aspect is an engine (31) for a saddle-ride type vehicle (1) mounted on a body frame (10) having a down frame (14) extending downward from a head pipe (11), the engine (31) including a cylinder (33) located rearward of the down frame, a cylinder head (34) installed on an upper surface of the cylinder, an exhaust pipe (61) extending rearward from the cylinder head, and an exhaust gas sensor (first oxygen sensor 71) for detecting predetermined characteristics in the exhaust gas, the exhaust pipe extending downward through one side of the down frame, crossing in front of the down frame, and then extending upward through the other side of the down frame, the exhaust gas sensor being installed on the rear side of the exhaust pipe on one side of the down frame and being located outward in the vehicle width direction from the cylinder in a front view. With this configuration, the exhaust gas sensor is installed using the space on the side of the cylinder, thereby improving the ease of assembly of the exhaust gas sensor and facilitating the routing of the exhaust gas sensor lead wires. In addition, the exhaust gas sensor is installed on the rear side of the exhaust pipe, and the exhaust pipe extends from one side to the other side of the down frame below the exhaust gas sensor, so the exhaust pipe can protect the exhaust gas sensor from foreign objects such as flying stones.

[0043] In the second aspect, in the first aspect, the portion of the exhaust pipe downstream of the exhaust gas sensor extends on one side of the down frame to the outside in the vehicle width direction of the exhaust gas sensor, and then curves back to the other side of the down frame. With this configuration, in the event of a sideways rollover, the exhaust pipe hits the ground before the exhaust gas sensor, thereby preventing damage to the exhaust gas sensor. In addition, the shape of the exhaust pipe can protect the exhaust gas sensor from foreign objects.

[0044] The third aspect is similar to the first and second aspects, except that it includes a pair of radiators (left radiator 42, right radiator 41) installed on both sides of the down frame, and a radiator hose (outlet hose 55) extending from the radiator (left radiator 42) on one side of the down frame, with the exhaust gas sensor located below the radiator hose in a front view. With this configuration, the radiator and radiator hose do not impair the ease of assembly of the exhaust gas sensor. Furthermore, since the exhaust gas sensor is covered from above by the radiator hose, the exhaust gas sensor can be protected from foreign objects entering from above.

[0045] In a fourth aspect, in the third aspect, the radiator hose extends rearward from the radiator on one side of the down frame and then extends to the other side of the down frame, and the exhaust gas sensor is installed in a space surrounded by the exhaust pipe and the radiator hose in a bottom view. With this configuration, when the vehicle falls to one side, the radiator hose hits the ground before the exhaust gas sensor, thereby preventing damage to the exhaust gas sensor.

[0046] A fifth aspect is any one of the first to fourth aspects, in which a suspension bracket (16) for the engine is attached to the down frame, and the exhaust gas sensor overlaps the suspension bracket in a side view. With this configuration, space is provided on the sides of the suspension bracket to allow for easy installation of the engine, making it easy to install the exhaust gas sensor on one side of the suspension bracket relative to the exhaust pipe. In addition, the exhaust gas sensor is covered from the other side by the suspension bracket, so that the exhaust gas sensor can be protected from foreign objects entering from the other side of the down frame.

[0047] A sixth aspect is any one of the first to fifth aspects, further comprising an engine guard (second engine guard 76) for protecting the engine that is installed below the engine, and the exhaust gas sensor overlaps the engine guard in a bottom view. With this configuration, the exhaust gas sensor is covered from below by the engine guard, thereby protecting the exhaust gas sensor from foreign matter from below the engine.

[0048] A seventh aspect is any one of the first to sixth aspects, in which a rearwardly bulging base (73) is provided on the rear side of the exhaust pipe, and the exhaust gas sensor is mounted on the base. With this configuration, the bulging base increases the cross-sectional area of ​​the exhaust pipe, making it possible to minimize the effect of pressure loss due to the protrusion of the exhaust gas sensor. The detection accuracy of the exhaust gas sensor can be ensured even in an exhaust pipe with many bends.

[0049] The eighth aspect is any one of the first to seventh aspects, and includes a catalyst (primary catalyst 65) installed in the exhaust pipe on the other side of the down frame, with the exhaust gas sensor and catalyst overlapping the down frame in a side view. With this configuration, the down frame can block hot air flowing from the catalyst toward the exhaust gas sensor. By installing the catalyst on the opposite side of the down frame from the exhaust gas sensor, the degree of freedom in installing the exhaust gas sensor can be improved.

[0050] 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.

[0051] Furthermore, the technology of the present invention is not limited to the above-described embodiments, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea. [Explanation of symbols]

[0052] 1: Saddle-type vehicle 10: Body frame 11: Head pipe 14: Down frame 16: Suspension bracket 31: Engine 33: Cylinder 34: Cylinder head 42: Left radiator (radiator) 55: Outlet hose (radiator hose) 61: Exhaust pipe 65: Primary catalyst (catalyst) 71: First oxygen sensor (exhaust gas sensor) 72: Lead wire 73: Pedestal 76: Second engine guard (engine guard)

Claims

1. An engine for a saddle-ride type vehicle mounted on a body frame having a down frame extending downward from a head pipe, a cylinder located behind the down frame; a cylinder head disposed on an upper surface of the cylinder; an exhaust pipe extending from the cylinder head toward the rear of the vehicle; an exhaust gas sensor for detecting a predetermined characteristic in the exhaust gas; 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, The engine is characterized in that the exhaust gas sensor is installed on one side of the down frame, behind the exhaust pipe, and is located outward in the vehicle width direction from the cylinder when viewed from the front.

2. 2. The engine according to claim 1, wherein a portion of the exhaust pipe downstream of the exhaust gas sensor extends on one side of the down frame to a position outside the exhaust gas sensor in the vehicle width direction, and then curves back to the other side of the down frame.

3. a pair of radiators installed on both sides of the down frame; a radiator hose extending from a radiator on one side of the down frame, 3. The engine according to claim 1, wherein the exhaust gas sensor is located below the radiator hose in a front view.

4. the radiator hose extends rearward from the radiator on one side of the down frame and then extends to the other side of the down frame, 4. The engine according to claim 3, wherein the exhaust gas sensor is disposed in a space surrounded by the exhaust pipe and the radiator hose when viewed from below.

5. 3. The engine according to claim 1, wherein a suspension bracket for the engine is attached to the down frame, and the exhaust gas sensor overlaps the suspension bracket in a side view.

6. Equipped with an engine guard installed under the engine to protect the engine, 3. The engine according to claim 1, wherein the exhaust gas sensor overlaps the engine guard when viewed from below.

7. 3. The engine according to claim 1, wherein a rearwardly bulging base is provided on a rear side of the exhaust pipe, and the exhaust gas sensor is mounted on the base.

8. a catalyst installed in the exhaust pipe on the other side of the down frame; 3. The engine according to claim 1, wherein the exhaust gas sensor and the catalyst overlap the down frame in a side view.

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