Saddle Riding Type Vehicle

Abstract

 A saddle riding type vehicle capable of improving detection accuracy by an oxygen sensor while reducing ventilation resistance in an exhaust path is provided. The vehicle includes an engine 34 provided with an exhaust path 68 and an oxygen sensor 72 attached to the engine 34 to detect oxygen included in exhaust gas. The engine 34 has a recess 70 provided at an inner surface of the exhaust path 68 and increasing a path sectional area of the exhaust path 68 and an insertion hole 76 opened at an inner surface of the recess 70. The oxygen sensor 72 is inserted in the insertion hole 76 as at least a part of its tip end is positioned in the recess 70.

Description

BACKGROUND

Technical Field

[0001] The present invention relates to a structure of an engine for a saddle riding type vehicle.

Description of the Background Art

[0002] An example of a saddle riding type vehicle is a motorcycle. In recent years, motorcycles are provided with oxygen sensors. An oxygen sensor is provided in an exhaust path. The oxygen sensor detects oxygen included in exhaust gas.

[0003] For example, JP-A 2004-316430 discloses a motorcycle including an oxygen sensor. The disclosed motorcycle includes a cylinder head. The cylinder head includes an exhaust port. The oxygen sensor is attached to the exhaust port.

SUMMARY

[0004] In order to improve detection accuracy using an oxygen sensor, exhaust gas must easily come into contact with the oxygen sensor. However, if the oxygen sensor has a large projection into the exhaust path, ventilation resistance in the exhaust path increases.

[0005] It is an object of the present invention to provide a saddle riding type vehicle capable of improving detection accuracy by an oxygen sensor while reducing ventilation resistance in an exhaust path.

Means for Solving the Problems and its Effects

[0006] A saddle riding type vehicle according to the present invention includes an engine provided with an exhaust path through which exhaust gas is passed and an oxygen sensor attached to the engine and used to detect oxygen included in exhaust gas, the engine has a recess provided at an inner surface of the exhaust path to increase a path sectional area of the exhaust path and an insertion hole opened at an inner surface of the recess and having the oxygen sensor inserted therein, and the oxygen sensor is inserted in the insertion hole as at least a part of a tip end of the oxygen sensor is positioned in the recess.

[0007] The saddle riding type vehicle according to the invention is capable of improving detection accuracy by the oxygen sensor while reducing ventilation resistance in the exhaust path.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] 

Fig. 1 is a left side view of an overall structure of a motorcycle according to an embodiment of the present invention.

Fig. 2 is a left side view of a power unit included in the motorcycle shown in Fig. 1.

Fig. 3 is a left side view of an engine and an air cleaner.

Fig. 4 is a right side view of the engine and the air cleaner.

Fig. 5 is a front view of the engine.

Fig. 6 is a bottom view of a part of the air cleaner and the engine.

Fig. 7 is an enlarged view of a port included in a head main body.

Fig. 8 is a sectional view taken along line VIII-VIII in Fig. 7.

Fig. 9 is a sectional view taken along line IX-IX in Fig. 7.

Fig. 10 is an enlarged view of a port showing an application example of another attachment position of an oxygen sensor.

Fig. 11 is a sectional view taken along line XI-XI in Fig. 10.

DESCRIPTION OF THE EMBODIMENTS

Embodiments

[0009] Now, a saddle riding type vehicle according to an embodiment of the present invention will be described in conjunction with the accompanying drawings. The embodiment will be described by way of illustrating a scooter type motorcycle as the saddle riding type vehicle. In the following, the same or corresponding portions are designated by the same reference characters and their description will not be repeated.

Overall Structure

[0010] Fig. 1 is a left side view of a motorcycle 10 according to the embodiment of the invention. Note that in the following description, the front, rear, left, and right refer to these directions viewed from a rider seated on the seat 28 of the motorcycle 10. In Fig. 1, the arrow F designates the forward direction of the motorcycle 10 and the arrow U designates the upward direction of the motorcycle 10.

[0011] The motorcycle 10 includes a vehicle body frame 12. A head pipe 14 is provided at a front end of the vehicle body frame 12.

[0012] A steering shaft 16 is inserted in the head pipe 14 in a rotatable manner to the left and right. A handle 18 is attached at an upper end of the steering shaft 16. The steering shaft 16 is rotated by operating the handle 18.

[0013] A bracket 20 is attached at a lower end of the steering shaft 16. Upper end of a front fork 22 is attached to the bracket 20. The front fork 22 supports a front wheel 24 in a rotatable manner.

[0014] The vehicle body frame 12 is covered with a vehicle body cover 26. The vehicle body cover 26 is for example made of synthetic resin.

[0015] The seat 28 is provided above the vehicle body frame 12 on the rear side. There is a storage space under the seat 28. The storage space for example stores a helmet or the like.

[0016] A power unit 30 is provided under the vehicle body frame 12 on the rear side. The vehicle body frame 12 supports the power unit 30 swingably in the vertical direction.

[0017] A rear wheel 32 is attached in a rotatable manner at a rear end of the power unit 30. As the motive power of the power unit 30 is transmitted to the rear wheel 32, the rear wheel 32 rotates.

Power Unit

[0018] Referring to Fig. 2, the power unit 30 will be described. Fig. 2 is a left side view of the power unit 30. In Fig. 2, the arrow F designates the forward direction of the motorcycle 10 and the arrow U designates the upward direction of the motorcycle 10. The power unit 30 includes an engine 34 and a transmission 36.

[0019] The engine 34 is a 4-stroke single cylinder engine. The engine 34 generates the motive power of the motorcycle 10. The engine 34 may be either an air-cooled engine or a water-cooled engine.

[0020] The transmission 36 is a continuously variable transmission. The transmission 36 transmits motive power generated by the engine 34 to the rear wheel 32 (see Fig. 1).

Engine

[0021] Referring to Figs. 3 to 6, the engine 34 will be described. Fig. 3 is a left side view of the engine 34 and an air cleaner 48. Fig. 4 is a right side view of the engine 34 and the air cleaner 48. Fig. 5 is a front view of the engine 34. Fig. 6 is a bottom view of a part of the air cleaner 48 and the engine 34. In Figs. 3 and 4, the air cleaner 48 is positioned in front of the engine 34. Fig. 6 shows a part of the air cleaner 48 positioned in front of the engine 34. In Fig. 5, the air cleaner 48 is not shown. In Figs. 3 and 4, the arrow F designates the forward direction of the motorcycle 10 and the arrow U designates the upward direction of the motorcycle 10. In Fig. 5, the arrow L designates the leftward direction of the motorcycle 10 and the arrow U designates the upward direction of the motorcycle 10. In Fig. 6, the arrow F designates the forward direction of the motorcycle 10 and the arrow L designates the leftward direction of the motorcycle 10.

[0022] The engine 34 has a cylinder 38. The cylinder 38 guides a piston to move linearly in a reciprocating manner. As shown in Figs. 2 and 3, the cylinder 38 has an axial line (cylinder axial line L) slightly inclined with respect to the front-rear direction of the vehicle. The cylinder axial line L extends obliquely upward in the forward direction. A front end of the cylinder 38 is positioned above a rear end of the cylinder 38.

[0023] The cylinder 38 has a cylinder body 40 and a cylinder head 42.

[0024] The cylinder body 40 is attached at a front end of a transmission case 37 that stores the transmission 36. The piston is provided in the cylinder body 40.

[0025] The cylinder head 42 has a head main body 44 and a head cover 46.

[0026] The head main body 44 is attached to a front portion of the cylinder body 40. The head main body 44 forms a combustion chamber together with the piston. The head main body 44 is provided with a cam shaft. The cam shaft drives a valve. The valve carries out air intake/exhaust to/from the combustion chamber.

[0027] The head cover 46 is attached to a front portion of the head main body 44. The head cover 46 covers the camshaft.

[0028] An intake system 47 is provided near the cylinder head 42. The intake system 47 produces air-fuel mixture and supplies the mixture to the combustion chamber. In the example shown in Figs. 3 to 6, the intake system 47 is provided upward from the front of the cylinder head 42.

[0029] As shown in Figs. 3 and 4, the intake system 47 includes an air cleaner 48, an intake pipe 49, a throttle body 50, a manifold 51, an injector 52 and a sensor 53.

[0030] The air cleaner 48 stores air cleaner elements. The air cleaner 48 is provided in front of the cylinder head 42.

[0031] The intake pipe 49 is positioned above the air cleaner 48. The intake pipe 49 has one end connected to the air cleaner 48. The intake pipe 49 has the other end connected to the throttle body 50. The intake pipe 49 guides air passed through the air cleaner elements into the throttle body 50.

[0032] The throttle body 50 is positioned behind the intake pipe 49. The throttle body 50 has one end connected to the intake pipe 49. The throttle body 50 has the other end connected to the manifold 51. The throttle body 50 stores the throttle valve. The throttle valve adjusts the flow rate of the air.

[0033] The manifold 51 is positioned behind the throttle body 50. The manifold 51 has one end connected to the throttle body 50. The manifold 51 has the other end connected to the head main body 44. The manifold 51 guides air having its flow rate adjusted by the throttle valve to the head main body 44.

[0034] The injector 52 is attached to the head main body 44. The injector 52 is for example attached to an intake port provided at the head main body 44. The intake port is connected with the other end of the manifold 51. The injector 52 injects fuel into air passed through the air cleaner elements and having its flow rate adjusted by the throttle valve. In this way, air-fuel mixture is generated. The amount of air-fuel mixture supplied to the combustion chamber changes depending on the opening/closing amount of the throttle valve.

[0035] A sensor 53 (see Fig. 3) is attached to the throttle body 50. The sensor 53 detects a state of the engine 34. The sensor 53 for example outputs a signal used to control the output of the engine 34. The sensor 53 is for example an intake pipe pressure sensor, an intake temperature sensor, and a throttle position sensor. The intake pipe pressure sensor detects intake air pressure. The intake temperature sensor detects intake air temperature. The throttle position sensor detects the opening degree of the throttle valve. According to the embodiment, the sensor 53 is an integrated sensor capable of functioning as an intake pipe pressure sensor, an intake temperature sensor and a throttle position sensor. A fuel injection amount by the injector 52 is determined based on intake air pressure detected by the sensor 53.

[0036] As shown in Fig. 4, an ignition plug 58 is attached at a right side surface of the head main body 44. The ignition plug 58 ignites air-fuel mixture compressed in the combustion chamber. In this way, air-fuel mixture explodes/combusts.

[0037] As shown in Fig. 3, an ignition coil 60 is provided at a left side surface of the head cover 46. The ignition coil 60 generates voltage necessary for the ignition plug 58 to ignite air-fuel mixture.

[0038] As shown in Figs. 5 and 6, the ignition plug 58 and the ignition coil 60 are connected by a plug cord 62. The plug cord 62 passes high voltage current generated by the ignition coil 60 to the ignition plug 58.

[0039] As shown in Figs. 3 to 6, an exhaust port 64 is provided at a lower surface of the head main body 44. The exhaust port 64 is connected with an exhaust pipe 66.

Exhaust Path

[0040] As shown in Figs. 7 to 9, the head main body 44 is provided with an exhaust path 68. Fig. 7 is an enlarged view of the exhaust port 64 of the head main body 44. Fig. 8 is a sectional view taken along line VIII-VIII in Fig. 7. Fig. 9 is a sectional view taken along IX-IX in Fig. 7.

[0041] The exhaust path 68 is connected to the combustion chamber. The exhaust path 68 passes exhaust gas generated in the combustion chamber to the exhaust pipe 66. More specifically, at least a part of the exhaust path 68 is formed at the exhaust port 64.

[0042] Here, the vertical direction in Fig. 7 (the axial direction of the cylinder 38) is a first direction, the path direction of the exhaust path 68 is a second direction, and the left-right direction in Fig. 7 (the left-right direction of the vehicle) is a third direction. The exhaust path 68 is curved in the third direction. More specifically, as shown in Fig. 9, the path is curved to one side (right side) in the vehicle widthwise direction.

Recess

[0043] The exhaust port 64 has a recess 70. The recess 70 is provided at an inner circumferential surface of the exhaust path 68. The exhaust path 68 has its path sectional area increased in a position where the recess 70 is formed.

[0044] The recess 70 is positioned more on one side (right side) in the vehicle widthwise direction than a center C of the exhaust path 68. Here, the center C of the exhaust path 68 is a center of the exhaust path 68 in the first direction and a center of the exhaust path 68 in the third direction. More specifically, the recess 70 is positioned on an inner circumferential side of the exhaust path 68. The width in the exhaust path 68 in the third direction is larger in a position where the recess 70 is formed.

Oxygen Sensor

[0045] The exhaust port 64 is provided with an oxygen sensor 72. The oxygen sensor 72 has a detector 74. The detector 74 is positioned at one end of the oxygen sensor 72 in the axial direction. The detector 74 detects oxygen included in exhaust gas. The oxygen sensor 72 is a heater-less oxygen sensor.

[0046] The oxygen sensor 72 is attached at the exhaust port 64 more on the side of the head cover 46 than the center C of the exhaust path 68.

[0047] More specifically, the exhaust port 64 has an insertion hole 76. The insertion hole 76 is positioned more on the side of the head cover 46 than the center C of the exhaust path 68 and on one side (right side) in the vehicle widthwise direction. The insertion hole 76 extends in the first direction. More specifically, the direction in which the insertion hole 76 extends is the first direction. In other words, the lengthwise direction of the insertion hole 76 is the first direction. A thread groove is provided at an inner circumferential surface of the insertion hole 76.

[0048] The oxygen sensor 72 has an attachment portion 78. The attachment portion 78 extends in an axial direction of the oxygen sensor 72. A screw thread is formed at an outer circumferential surface of the attachment portion 78.

[0049] The oxygen sensor 72 is inserted into the insertion hole 76. As shown in Figs. 7 and 8, the oxygen sensor 72 is inserted into the insertion hole 76 from the outside of the exhaust port 64. More specifically, the oxygen sensor 72 is inserted into the insertion hole 76 from the outside of the exhaust path 68. At the time, the screw thread of the attachment portion 78 engages with the thread groove of the insertion hole 76. As a result, the oxygen sensor 72 is attached to the exhaust port 64. In this state, the axial line of the oxygen sensor 72 extends in the direction (first direction) in which the axial line (cylinder axial line L in Figs. 2 and 3) of the cylinder 38 extends.

[0050] The insertion hole 76 is opened at the inner surface of the recess 70. As the attachment portion 78 is attached to the insertion hole 76, the tip end (detector 74) of the oxygen sensor 72 is positioned in the recess 70. More specifically, the detector 74 is exposed to the space in the recess 70. The entire tip end (detector 74) of the oxygen sensor 72 does not have to be positioned in the recess 70. At least a part of the tip end (detector 74) of the oxygen sensor 72 needs only be in the recess 70.

[0051] As shown in Fig. 9, more on the upstream side of the exhaust path 68 than the tip end of the oxygen sensor 72 in the recess 70, the width of the recess 70 in the third direction gradually increases from the upstream side of the exhaust path 68 to the downstream side. Stated differently, more on the upstream side of the exhaust path 68 than the oxygen sensor 72 in the recess 70, a space having a greater width on the downstream side than on the upstream side of the exhaust path 68 is formed at least for one of the first and third directions.

Advantageous Effects of the Embodiment

[0052] According to the embodiment, the tip end of the oxygen sensor 72 is positioned in the recess 70. The ventilation resistance in the exhaust path 68 is reduced. The tip end (detector 74) of the oxygen sensor 72 comes into contact with exhaust gas more easily. This makes it easier to activate the detector 74. The detection accuracy using the oxygen sensor 72 increases.

[0053] According to the embodiment, more on the upstream side of the exhaust path 68 than the tip end of the oxygen sensor 72 in the recess 70, there is a space having a width gradually increased in the third direction from the upstream to the downstream of the exhaust path 68. This makes it difficult for turbulent flow to form in the recess 71. Exhaust gas is supplied more easily to the tip end of the oxygen sensor 72.

[0054] According to the embodiment, the oxygen sensor 72 is offset in the third direction from the center C of the exhaust path 68. This reduces the projection amount of the oxygen sensor 72 to the side of the head cover 46.

[0055] According to the embodiment, the exhaust path 68 is curved in the third direction. The oxygen sensor 72 is provided on the inner circumferential side of the exhaust path 68. In this way, the oxygen sensor 72 can be closer to the combustion chamber.

[0056] According to the embodiment, the oxygen sensor 72 is a heater-less oxygen sensor. Therefore, the oxygen sensor 72 has a reduced size.

[0057] According to the embodiment, the oxygen sensor 72 is attached to the exhaust port 64. This makes it easier to attach the oxygen sensor 72.

Application Examples of Attachment Position for Oxygen Sensor

[0058] The oxygen sensor 72 does not have to be offset from the center C of the exhaust path 68 in the third direction. For example, as shown in Figs. 10 and 11, the oxygen sensor 72 may be positioned immediately above the center C of the exhaust path 68. Fig. 10 is an enlarged view of a port showing another application example of the attachment position for the oxygen sensor. Fig. 11 is a sectional view taken along XI-XI in Fig. 10. In this example, the recess 70 is positioned immediately above the center C of the exhaust path 68 as shown in Fig. 10. The exhaust path 68 has an expanded width in the first direction at a position where the recess 70 is formed.

[0059] In the above described embodiment, the oxygen sensor 72 is offset to the inner circumferential side from the center C of the exhaust path 68, but it may be offset to the outer circumferential side. More specifically, the oxygen sensor 72 may be offset to the other side (left side) in the vehicle widthwise direction from the center C of the exhaust path 68. In this case, the recess 70 is positioned more on the other side (left side) in the vehicle widthwise direction than the center C of the exhaust path 68. This reduces the projection amount of the exhaust port 64 from the head main body 44 (the total length of the exhaust port 64). The head main body 44 may be compact and lightweight.

[0060] In the above-described embodiment, the lengthwise direction of the insertion hole 76 is orthogonal to the lengthwise direction of the exhaust path 68 but the lengthwise direction of the insertion hole 76 does not have to be orthogonal to the lengthwise direction of the exhaust path 68. For example, an opening formed at an inner surface of the recess 70 in the insertion hole 76 may be shifted in the lengthwise direction of the exhaust path 68 with respect to an opening formed at the surface of the exhaust port 64.

[0061] The above-described embodiment relates to the motorcycle but the invention is not limited to the above and may be applied to three- or four-wheel leaning vehicles.

[0062] Although the embodiment of the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only for carrying out the invention and is not to be taken by way of limitation. Therefore, the above-described embodiment may be subject to variations and modification without departing the scope and spirit of the present invention.

Claims

1. A saddle riding type vehicle, comprising:

an engine provided with an exhaust path through which exhaust gas is passed; and

an oxygen sensor attached to the engine and configured to detect oxygen included in exhaust gas,

the engine having a recess provided at an inner surface of the exhaust path and increasing a path sectional area of the exhaust path and an insertion hole opened at an inner surface of the recess and having the oxygen sensor inserted therein,

the oxygen sensor being inserted in the insertion hole such that at least a part of a tip end of the oxygen sensor is positioned in the recess.

2. The saddle riding type vehicle according to claim 1, wherein when a lengthwise direction of the insertion hole is a first direction, a lengthwise direction of the exhaust path is a second direction, and a direction orthogonal to both the first and second directions is a third direction,
a width of the exhaust path in at least one of the first and third directions in a position where the recess is provided is larger than the width in the direction in a position without the recess.

3. The saddle riding type vehicle according to claim 2, wherein a space is formed more on an upstream side of the exhaust path than the oxygen sensor in the recess.

4. The saddle riding type vehicle according to claim 3, wherein in the space, the recess has a larger width on a downstream side of the exhaust path than on the upstream side for at least one of the first and third directions.

5. The saddle riding type vehicle according to any one of claims 2 to 4, wherein the oxygen sensor is provided in a position offset from a center of the exhaust path in the third direction.

6. The saddle riding type vehicle according to claim 5, wherein the exhaust path is curved in the third direction and the oxygen sensor is provided more on an inner circumferential side than the center of the exhaust path in the third direction.

7. The saddle riding type vehicle according to claim 5, wherein the exhaust path is curved in the third direction, and the oxygen sensor is provided more on an outer circumferential side than the center of the exhaust path in the third direction.

8. The saddle riding type vehicle according to any one of claims 1 to 7, wherein the oxygen sensor is a heater-less oxygen sensor.

9. The saddle riding type vehicle according to any one of claims 1 to 8, wherein the engine comprises a cylinder head having a port connected with an exhaust pipe, and the oxygen sensor is attached to the port.

10. The saddle riding type vehicle according to claim 9, wherein at least part of the recess is formed at the port.

Drawing