DE69213780T2 - Motorcycle with exhaust device - Google Patents

Description

The present invention relates to a motorcycle with an engine, in particular a multi-cylinder engine, with an exhaust arrangement and an exhaust pipe arrangement, comprising a plurality of front exhaust pipes extending from the engine to an exhaust chamber, and a rear exhaust pipe extending from the exhaust chamber to discharge exhaust gas therefrom, and with an oxygen sensor for detecting the oxygen content of the exhaust gas, wherein the oxygen sensor extends upwards from the exhaust chamber.

There is a known exhaust system for a motorcycle having a structure in which a common large exhaust chamber is connected to a plurality of exhaust pipes extending from an engine. In a currently used exhaust system for a motorcycle, an oxygen sensor is provided which detects the combustion state of an engine (see, for example, Japanese Published Unexamined Patent Application No. Sho-58-152115).

The oxygen sensor detects the concentration of oxygen in an exhaust gas in the exhaust pipe. According to the detection signal from the sensor, the period of time for which the fuel injection system is kept in an open position is determined, i.e., the amount of fuel to be injected is determined in order to bring the air-fuel ratio (A/F) as close as possible to a theoretical value.

In the above-described structure, the oxygen sensor is mounted on the exhaust pipe below the engine. This places the point at which the oxygen concentration of an exhaust gas is determined as close to the engine as possible, thus To improve the accuracy of the amount of fuel to be injected.

If the oxygen sensor is installed on an outer surface of the exhaust pipe below the engine as described above, the oxygen sensor is close to the road surface on which the motorcycle is running. As a result, water or mud splashed from the wheels during riding easily hits the sensor. Therefore, there is a risk of the oxygen sensor being damaged.

In some cases, the oxygen sensor is mounted on a top surface of an exhaust pipe below the engine. As a result, in the exhaust system of the above-described motorcycle equipped with an oxygen sensor, the oxygen sensor is damaged by flying stones and rainwater ingress, etc. Furthermore, depending on the position where the oxygen sensor is mounted, the oxygen sensor may come into contact with the ground when the vehicle is tilted, and the tilt angle may be restricted.

JP-A-59099021 shows an oxygen sensor mounted on an exhaust chamber at an upper portion thereof. However, this known exhaust arrangement is not satisfactory in terms of cleaning the exhaust gas.

Accordingly, an object of the present invention was to provide a motorcycle with an improved exhaust arrangement including an improved oxygen sensor arrangement which enables the oxygen concentration of the exhaust gas to be detected with greater accuracy.

According to the present invention, this object is achieved in that a catalyst is arranged in the exhaust chamber and the oxygen sensor is arranged upstream of the catalyst and downstream of the opening ends of the front exhaust pipes which extend into the exhaust chamber. Accordingly, the oxygen concentration close to the engine is detected and, in addition, differences in the exhaust gas concentration of different exhaust pipes are compensated.

According to a preferred embodiment of the present invention, the oxygen sensor is arranged on an upper portion of the exhaust gas chamber, i.e. on an upper housing of the chamber, which is made of sheet metal.

According to further preferred embodiments of the present invention, the oxygen sensor is mounted in a recessed area of the upper housing of the exhaust chamber and inclined upwards.

According to a further preferred embodiment, a front exhaust pipe is detachably connected to the exhaust chamber, while the other front exhaust pipes of a multi-cylinder internal combustion engine are integrally formed with the exhaust chamber, which in turn is suspended and attached to the lower floor portion of the internal combustion engine.

According to a further preferred embodiment, there is a sensor protection shield arrangement, which is preferably formed by a cover extending downwards from the base frame and shielding the oxygen sensor from the side and from below, while according to a further modification, there is a front plate arrangement with a first protection plate protruding from the exhaust chamber and with a second protection plate protruding from the frame body or forming part of the cover, so that a labyrinth arrangement is created with the first protection plate, by which the oxygen sensor is protected. Further preferred embodiments of the present invention are set out in the other subclaims.

In the following, the present invention is described in more detail using several embodiments thereof in conjunction with the accompanying drawings, in which:

Fig. 1 is a motorcycle embodying a first embodiment of the exhaust arrangement according to the present invention,

Fig. 2 is a sectional front view of the exhaust structure, in particular an oxygen sensor protection arrangement,

Fig. 3 is a partial plan view of Fig. 2,

Fig. 4 is a section along the line 3-3 in Fig. 3,

Fig. 5 is a view corresponding to Fig. 3 showing another embodiment of the oxygen sensor protection assembly of the present invention,

Fig. 6 is a view corresponding to Fig. 2 for the other embodiment of the exhaust arrangement, in particular the oxygen sensor protection assembly, as shown in Fig. 5, and

Fig. 7 is a view corresponding to Fig. 4 for the analogous embodiment of the present invention as shown in Figs. 5 and 6.

In the figures, 1 indicates a motorcycle carrying an engine according to the present embodiment. The motorcycle 1 has a frame body consisting of a pair of left and right main frames 3 which have an inverted U-shape when viewed from the side and which are connected by a cross pipe, a head bracket 5 being attached to a cross pipe, a head bracket 5 being attached to an upper surface of an upper portion of each main frame 3, a lamp stay 6 is provided on forwardly extended portions of the head frames 5 and supports a front lamp 14, a seat rail 7 is provided on an upper rear end of each main frame 3, and a seat stay 8, through which the seat rail 7 is connected to a rear arm bracket 3c, is provided in a rear portion of the main frame 3.

The main frame 3 has a front portion provided with a front bracket 3a on which a front arm 12 is vertically pivotally supported. The front arm 12 is H-shaped as viewed in the plane and has rear end portions pivotally supported by the front bracket 3a and front end portions on which a front wheel bracket 10 is pivotally supported by a ball joint (not shown). A front wheel 11 is supported in the lower end of the fork 10. A lower portion of the front wheel bracket 10 and an upper end of the front bracket 3a are connected to each other by a front shock absorber 13. The front wheel fork 10 is supported by the head pipe 4 so as to be steerable to the left and right via a steering shaft 9. The shaft 9 consists of an upper tube 9a supported by the head pipe 4 and a lower tube 9b retractably received in the upper tube 9a and fixedly attached to an upper portion of the front fork 10, and is oriented so as to be disposed increasingly rearward, i.e., in a rearwardly inclined state, as the height of its position increases.

The rear swing arm 3c vertically pivotably supports a rear swing arm 15. The rear swing arm 15 has a rear end which rotatably supports a rear wheel 16. A front portion of the rear swing arm 15 is connected to a lower end of the rear swing arm support 3c via a link mechanism 17. The link mechanism 17 is connected to a shock absorber support through a rear shock absorber 18. (cushion bracket) 3d of the rear swing arm support 3c.

An engine unit 19 is suspended in the main frame 3. In a front upper portion of the engine unit 19, an air cleaner 20 and a glove box 21 are provided in this order from the bottom. In the rear upper portion of the engine unit 19, a fuel tank 22 is mounted, behind which a seat 23 is provided. The glove box 21, the fuel tank 22, etc. are surrounded by a tank cover 22a, which is provided with a lid 22b at a position adjacent to the glove box 21. Another lid 21a is provided in the lower part of the glove box 21.

At the rear of the steering shaft 9, there is provided a radiator 24, which is aligned along the steering shaft 9, i.e., in a rearwardly inclined state when viewed from the side. The radiator 24 has a rearwardly projecting curved member 24a, to the right end of which an inlet water tank 24b is attached and to the left end of which an outlet water tank 24c is attached. A pair of left and right air blowers 63 are arranged at the rear of the radiator 24 and are aligned outwardly and toward the left and right lower edge sides.

The engine unit 19 in the present embodiment is a water-cooled four-stroke parallel four-cylinder engine, which consists of a cylinder body 26, a cylinder head 27 and a head cover 28, which are arranged one above the other in a front upper portion of the crankcase 25. An intake manifold 29 is connected to a rear wall of the cylinder head 27. A throttle body 30 is attached to an upstream end of the intake manifold 29 so as to be arranged vertically as a whole. The air cleaner 20 is connected to the throttle body 30. 44a designates an air intake pipe, and 31 designates a fuel injection valve.

The cylinder head 27 has a front wall to which four exhaust pipes 46a-46d of the exhaust device 45 are attached. Each of the exhaust pipes 46a-46d extends from a front portion of the crankcase 25 to a lower portion thereof and is connected to a common exhaust chamber 47 arranged below the crankcase 25. The exhaust chamber 47 is divided into two and consists of an upper and a lower housing 47a and 47b which are connected to each other. The upper housing 47a has a rear end portion in which an exhaust pipe 47e is integrally formed. At the front end of the exhaust chamber, rear ends of the three exhaust pipes 46b-46d except for the exhaust pipe 46a at the left end are welded. The exhaust pipe 46a at the left end is inserted into a joint 47c welded to the front end and is fixed thereto by means of a fastening band 48 wound around it and secured with a fastening bolt 48a. This enables the exhaust pipe 46a at the left end to be detached so that the exhaust device 45 can be easily attached to the engine. That is, the front swing arm 12 of the motorcycle of the present invention has an H-shape and the width a of the exhaust pipes 46a-46d is larger than the inner width b of the front swing arm 12. Therefore, the front swing arm interferes with the exhaust pipes so that the assembling operation is difficult to perform. On the other hand, when the exhaust pipe 46a at the left end is detached, the width of the exhaust pipes is smaller than the inner width mentioned above so that the assembling operation is easy to perform.

The exhaust gas arrangement, and in particular the oxygen sensor arrangement, is explained and presented in more detail below.

The curved ends of the front exhaust pipes 46a to 46d are connected to the exhaust chamber 47, as shown in the figures, to which the rear pipe 47f is attached. The rear pipe 47f extends rearward, and its rear end is connected to a muffler (not shown). The exhaust chamber 47 extends rearward under an oil pan 61 which forms a bottom of the engine 19. The exhaust chamber 47 is formed by press molding and consists of an upper inverted bowl-shaped plate 62 and a lower bowl-shaped plate 64 which face each other in the shape of waffles filled with bean paste and are connected to each other with the connecting portion being welded to form the upper and lower casings 47a, 47b. The exhaust chamber 47 includes a pair of front and rear partition plates 65 which are welded to the central portions of the inner surface of the exhaust chamber at the upper and lower portions thereof, being located one behind the other in the traveling direction of the motorcycle 1. The partition plates 65 divide the exhaust chamber 47 into a front and a rear chamber 67, 68, the front chamber 67 being connected to the front exhaust pipes 46a to 46d, while the rear chamber is connected to the rear exhaust pipe 47f.

There is a cylindrical body 69 which extends through the partition plates 67, 68 and is welded thereto. The catalyst 52 is fixed in the cylindrical body 69. A sealing material 66 is arranged between the inside of the cylindrical body 69 and the outside surface of the catalyst 52.

The flow of exhaust gas 70 from the engine 90 passes sequentially through the front exhaust pipes 46a to 46d, the front chamber 67, catalyst 52 and the rear chamber 68 of the exhaust chamber 47, and the rear exhaust pipe 47f and is discharged rearwardly from the motorcycle body. In this case, the catalyst 52 serves to purify the exhaust gas 70 flowing through it.

An eye 49a is welded to the front right section of the exhaust chamber 47 and passed through the wall thereof

The oxygen sensor 49 is detachably secured to the boss 49a with screws on the outside of the exhaust chamber 47. The oxygen sensor 49 is covered from above by a side portion of the oil pan 62 and has a detection portion 49b that is adjacent to the front chamber 67.

The oxygen sensor 52 detects the oxygen concentration in the exhaust gas 70 and the exhaust chamber 474. The detection signal determines the opening time of the fuel injection valve (not shown here) of the engine 19, i.e., the amount of fuel to be injected.

In the present embodiment, the oxygen sensor 49 is preferably located as far upstream as possible in the flow of the exhaust gas 70 and as close as possible to the engine 19. One could think of mounting the oxygen sensor on one of the front exhaust pipes 46a to 46d. However, since the oxygen concentrations in the front exhaust pipes 47a to 47d are different, it is more sensible to mount the oxygen sensor 49 in the exhaust chamber 47, in which the oxygen concentration of the front exhaust pipes 47a to 47d is equalized.

A temperature sensor that detects the temperature of the exhaust gas 70 is a thermocouple, indicated by reference numeral 72. The exhaust gas temperature sensor 72 is detachably attached to a rear portion of the exhaust chamber 47 and has a sensing portion 72a adjacent to the rear chamber 68. The sensing portion 72a is arranged downstream and near the catalyst 52 to detect the temperature of the exhaust gas 70 and thus indirectly determine the temperature of the catalyst 52. Footrests are indicated by reference numeral 73.

There is, as shown in Fig. 2, a pair of covers 60 which cover the frame body 3, the engine 19, the exhaust device 45 and the oxygen sensor 49 of left and right. Each of the covers 60 is supported by the frame body 3 and forms a part of the body 3. The right cover 60 has a lower portion that covers the bottom of the oxygen cylinder 49, thus serving as a protective member for the oxygen sensor 49.

In the illustrated case, the oxygen sensor 49 is arranged in a narrow space defined by the oil pan 61 and the cover 60 and is attached to the exhaust chamber 47 with the detection portion 52a lowered forward. Furthermore, the longitudinal direction of the oxygen sensor 49 is aligned on the inside of the cover 60 corresponding to the oxygen sensor 49. With this structure, the lower edge of the oxygen sensor 49 is aligned obliquely upward, so that the oxygen sensor 49 can be easily wired.

Since the oxygen sensor 49 must be arranged in the narrow space between the oil pan 61 and the cover 60 as described above, the boss 52a to which the oxygen sensor 49 is fastened with bolts is provided at the portion where the upper plate 62 and the lower plate 64 are connected to each other, spanning both plates 62, 64.

A first protection plate 74 made by press molding is provided on the right side of the outer surface of the exhaust chamber 74 near the front portion of the oxygen sensor 49. The first protection plate 74 covers a front side of the oxygen sensor 49. Accordingly, the first protection plate 74 serves as a protection member for the oxygen sensor 49. The first protection plate 74 has a lower portion welded over the upper and lower plates 62, 64 so that the strength of the connection between the upper and lower plates 62, 64 (upper case 47a, lower case 47b) is improved.

A second protection plate 75 is integrally formed on an inner surface of the casing 60 and protrudes into a space between the oxygen sensor 49 and the first protection plate 74. The second protection plate 75 covers a front side of the oxygen sensor 49 and thus serves as a protection member for the oxygen sensor 49. The passage leading to the oxygen sensor 49 from a portion in front thereof has a shape of a labyrinth formed by the first and second protection plates 74, 75.

With the above-described structure, since the oxygen sensor 49 is mounted on an outer surface of the exhaust chamber 47, the oxygen sensor 49 is located near the road surface when the motorcycle is running, so that water and the like splash thereon and adhere to the oxygen sensor 49 when the motorcycle is running. However, in the above-described embodiment, the oil pan 61 covers the upper surface of the oxygen sensor 49, the lower portion of the cover 60 covers the lower surface of the oxygen sensor 49, and the first and second protection plates 74, 75 cover the front surface thereof, so that the above-mentioned impact by these parts is surely prevented and damage to the oxygen sensor 49 can be avoided.

Furthermore, since the cover 60 has a high strength and the second protection plate 75 is attached to the cover 60 with a high strength, the attachment of the protection plates 62, 64 becomes a sufficient strength, by which the above-mentioned impact of water, stones or the like is further securely prevented.

In addition, since the passage between the first and second protection plates 62, 64 has a labyrinth shape, the above-mentioned impact is further securely prevented.

Fig. 5 to 7 show a further embodiment in which the second protective plate 75 is attached to the frame body 3, which has high strength Otherwise, the structure and function are the same as in the above-described embodiments shown in Figs. 2 to 4, and therefore the common parts are assigned the same reference numerals in the drawings and for the description, reference is made to the above explanation.

Therefore, since the oxygen sensor is arranged at an upper portion of the exhaust chamber, the lower portion of the exhaust chamber serves as a protector for the oxygen sensor and can prevent damage to the oxygen sensor by flying stones, intrusion of rainwater, etc. Furthermore, according to a further development of the sensor protection arrangement, there is provided a protection member covering the bottom and front of the oxygen sensor, i.e., the protection member comprising lower parts of the cover and/or a side plate arrangement, which further protects the oxygen sensor.

Claims (13)

1. Motorcycle with an engine (19), in particular multi-cylinder engine, with an exhaust arrangement and an exhaust pipe arrangement, containing a plurality of front exhaust pipes (46a, 46d) which extend from the engine (19) to an exhaust chamber (47) and a rear exhaust pipe which extends from the exhaust chamber (47) to discharge exhaust gas therefrom, and with an oxygen sensor (49) for detecting the oxygen content of the exhaust gas, the oxygen sensor (49) extending upwards from the exhaust chamber (47), characterized in that a catalyst (52) is arranged in the exhaust chamber (47) and the oxygen sensor (49) is arranged upstream of the catalyst (52) and downstream of the opening ends of the front exhaust pipes (46a, 46d) which open into the exhaust chamber (47). 2. Motorcycle according to claim 1, characterized in that the oxygen sensor (49) is arranged at an upper portion of the exhaust chamber (47). 3. Motorcycle according to claim 1 and 2, characterized in that the exhaust chamber (47) is composed of an upper and a lower housing (47a, 47b) made of sheet metal, and that the oxygen sensor (49) is connected to the upper housing (47a) of the exhaust chamber (47). 4. Motorcycle according to claim 3, characterized in that the oxygen sensor (49) is arranged on an upper front portion of the upper housing (47a) of the exhaust chamber (47) and is oriented obliquely upwards. 5. Motorcycle with a four-cylinder engine with four front exhaust pipes (46a to 46d) connecting to the exhaust chamber (47) according to at least one of the preceding claims 1 to 4, characterized in that a laterally arranged front exhaust pipe (46a) is detachably connected to the exhaust chamber (47), while the other front exhaust pipes (46b to 46d) are formed integrally with the exhaust chamber (47) which is suspended and attached to the lower floor portion of the engine (19). 6. Motorcycle according to at least one of claims 1 to 5, characterized in that the oxygen sensor (49) is arranged laterally offset relative to the catalyst (52). 7. Motorcycle according to at least one of the preceding claims 1 to 6, characterized in that the oxygen sensor (49) is arranged on a recessed area of the upper housing (47a) of the exhaust chamber (47). 8. Motorcycle according to at least one of the preceding claims 1 to 7, characterized in that a sensor protection arrangement is provided for shielding the oxygen sensor (49). 9. Motorcycle according to at least one of the preceding claims 1 to 8, characterized in that the sensor protection arrangement comprises a cover which extends downwards from the floor frame and shields the oxygen sensor (49) from the side and from below and/or a front plate arrangement which shields the oxygen sensor from the front. 10. Motorcycle according to claim 8, characterized in that the front plate assembly comprises a first protective plate (74) which projects from the exhaust chamber (47) and integrally connects the upper and lower housings (47a, 47d) thereof. 11. Motorcycle according to claim 9 or 10, characterized in that the protective plate arrangement comprises a second protective plate (75) which projects from the frame body (3) and projects integrally from the fairing (60) and forms a labyrinth arrangement with the first protective plate (74). 12. Motorcycle according to at least one of the preceding claims 3 to 11, characterized in that the exhaust chamber (47) has a section which is substantially V-shaped in cross section and is arranged closely adjacent to an oil pan (61) which is arranged above the exhaust chamber, wherein the oil pan (61) has a bottom contour which is adapted to the upper side of the exhaust chamber (47), while the oxygen sensor (49) protrudes substantially laterally inclined upwards from a connecting region between the upper and lower housings (47a, 47b) of the exhaust chamber (47). 13. Motorcycle according to at least one of the preceding claims 1 to 11, characterized in that an upper side of the oxygen sensor (49) is protected by an oil pan (61) of the engine (19).