JP2554088B2 - Frame support structure for motorcycle engine unit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a structure for supporting a motorcycle engine unit with a frame, and in particular, for crankshaft replacement in a short time, such as an engine unit in a racing vehicle. The present invention relates to a frame support structure suitable when it is necessary to perform maintenance work such as.

[Conventional technology]

In the motorcycle engine unit, a crankcase and a transmission case are integrally formed, and the integrated case is used to insert the crankshaft and the transmission.
There is a so-called upper and lower split type in which a plane including an output shaft and the like is divided into an upper case and a lower case. When this split vertical engine unit is mounted on a vehicle body frame, it is common to fasten each of the upper case and the lower case to the vehicle body frame with bolts (see, for example, Japanese Utility Model Laid-Open No. 54-146553).

In such an engine unit, when performing large maintenance such as crankshaft replacement, lower the entire engine unit from the body frame, remove the cylinder body, etc., and then divide the crankcase into an upper case and a lower case. , The crankshaft will have to be replaced. As described above, the crankshaft replacement work is premised on the attachment / detachment of the engine unit. Therefore, some conventional body frames are configured so that the down tube can be removed to facilitate the attachment / detachment of the engine unit. is there.

[Problems to be solved by the invention]

By the way, in the case of an ordinary motorcycle for driving on public roads, the above-mentioned maintenance method rarely causes a problem because the frequency of large maintenance as described above is low and there is a time margin. However, for example, when it is necessary to repeat running and maintenance until just before the start of a race, such as a racing vehicle, the above-mentioned large maintenance will be performed frequently in a short time. I can't answer.

In view of the above situation, an object of the present invention is to provide a frame support structure for an engine unit for a motorcycle, which allows large maintenance such as the crankshaft replacement while the engine unit is mounted on a vehicle body frame.

[Means for solving problems]

The present invention provides a motorcycle engine unit in which a crankcase is divided into a first case and a second case in a plane including a crankshaft, and a mission case is integrally formed in the second case, and has left and right down tubes. In the support structure mounted on the vehicle body frame, the dividing surfaces of the first and second cases are made to face the front of the vehicle, and the width of the first case to which the cylinder body is connected is substantially larger than the distance between the left and right down tubes. It is characterized by being narrowed to.

Here, in the present invention, the point that the split surface of the crankcase faces the front of the vehicle and the point that the width of the first case is substantially narrower than the distance between the down tubes are that the second case and the mission case integrated with the second case are the frames. This is because the cylinder head, the cylinder body, and the first case can be removed with the device still mounted. Therefore, it is sufficient that the split surface faces forward so that the cylinder head, the first case, and the like do not interfere with the lower surface of the main frame or the like when they are removed, and the width of the first case is the front. Even if it overlaps with the down tube as viewed from the above, it does not have to interfere with the down tube at the time of removal, and the physical size does not necessarily have to be smaller than the down tube interval.

Further, the pair of left and right down tubes of the present invention includes one having a main frame connecting portion and being separated into two at the engine unit portion.

[Action]

According to the frame support structure of the engine unit according to the present invention, for example, when exchanging the crankshaft, the cylinder head and the cylinder body are first removed with the engine unit mounted on the vehicle body frame, and then the first case and the first case. If the connecting bolt with the two cases is removed, the split surfaces of both cases face the front of the vehicle and the width of the first case is substantially narrower than the distance between the down tubes. Therefore, the first case can be removed as it is. . As a result, the crankshaft is exposed to the outside, so that the crankshaft can be replaced with the second case and the mission case mounted on the frame.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 are views for explaining an engine unit support structure according to an embodiment of the present invention. In the figure, reference numeral 1 is a motorcycle adopting the structure of the present embodiment, and a body frame 2 thereof is of a so-called double cradle type, and is provided at the rear ends of a pair of left and right main frames 2a extending obliquely downward and rearward of the vehicle. , A pair of left and right rear arm brackets 2c connected by the upper and lower cross members 2b are fixed, the bracket 2c and the lower front surface of the rear part of the main frame 2a are connected by a pair of left and right down tubes 2d, and further the main frame 2a The seat rail 2e is disposed on the upper surface of the.

A steering fork barrel 2f fixed to the front end of the main frame 2a has a front fork 4 pivotally supporting the front wheel 3 at its lower end, and the rear arm bracket 2c has a rear end. At the front end of a rear arm 6 which pivotally supports the rear wheel 5, is pivotally supported so as to be vertically swingable. A link 6b of the rear wheel suspension device is provided between the reinforcing member 6a on the lower surface of the rear arm 6 and the lower block member 2b, and a shock absorber 6c is provided between the link 6b and the upper cross member 2b. ing. In addition, 7
Is a fuel tank, 8 is a seat, and 9 is a cowling.

A two-cycle water-cooled two-cylinder engine unit 10 is mounted in the substantial center of the body frame 2. The crankcase 11 of the engine unit 10 is divided into an upper case (first case) 11a located on the front side of the vehicle and a lower case (second case) 11b located on the rear side. The split surface 11c is vertical when viewed from the side surface, extends in the vehicle width direction including the axis of the crankshaft 18, and faces the front of the vehicle. The cases 11a and 11b are connected by a connecting bolt 22a arranged inside the lower case 11b and a connecting bolt 22b arranged outside.

The mission case 1 is on the rear side of the lower case 11b.
7 are integrally formed. The mission case 17 is for accommodating the speed change gear device, and the main shaft is located at the substantially center.
18a, a drive shaft 18b at the rear part thereof, and a change drum 23a further below are arranged in the mission case 17 by a so-called cassette mission system. In addition, 23b is a change shaft, 23c is the shaft 23b and the change drum 2
An arm connecting with 3a and 18c is a counter shaft for transmitting the rotation of the crankshaft 18 to the main shaft 18a. A drive chain 20 is wound between the drive sprocket 19a fixed to the protruding end of the drive shaft 18b and the driven sprocket 19b fixed to the rear wheel shaft.

The support portions 11e formed on the left and right outer portions of the lower surface of the front end portion of the lower case 11b are fixed and supported by bolting to the support brackets 21a fixed to the down tube 2d, and the rear end portion of the mission case 17 is also provided. The support portions 17a on the left and right outer portions of the upper surface are attached to the support bracket 21b fixed to the rear arm bracket 2c, and the support portions 17b on the left and right outer portions of the lower surface of the rear end portion are attached to the support bracket 21c fixed to the lower cross member 2b. It is fixed and supported by bolting. The upper and lower support parts 17a and 17b of the mission case 17 are located above and below the drive shaft 18b.

An intake port 11d communicating with the crank chamber is formed on the front lower surface of the upper case 11a, and a carburetor 12 is connected to the intake port 11d.
Is arranged. Exhaust port 13a of this cylinder body 13
A muffler 14 is connected to the muffler 14, and this muffler 14 is an exhaust port.
It extends obliquely upward and rearward of the vehicle so as to form a straight line with the discharge direction of 13a. A cylinder head 15 is arranged on the upper surface of the cylinder body 13 and is fixed together with the cylinder body 13 by stud bolts 21c planted in the upper case 11a. The width of each of the upper case 11a, the cylinder body 13, and the cylinder head 14 is narrower than the distance between the left and right down tubes 2d when viewed from the front of the vehicle. Reference numeral 16 is a radiator, which is connected to the cylinder head 15 by a circulation hose 16a.

 Next, the function and effect of this embodiment will be described.

When replacing the crankshaft, conventionally, it was necessary to lower the entire engine unit from the body frame, and it was difficult to perform such work in a short time. On the other hand, when replacing the crankshaft 18 in this embodiment, first, the cylinder head 15 and the cylinder body 13 are removed while the engine unit 10 is still mounted on the vehicle body frame 2. Then, as shown in FIG. 1, the upper case 11a
Faces the front from between the left and right down tubes 2d, and then the upper case 11a is coupled to the lower case 11b and the coupling bolts 22a and 22b are removed. Then the upper case 11a
From the point that the dividing surface 11c faces the front of the vehicle and the width of the upper case 11a is narrower than the distance between the down tubes 2d, it can be removed as it is. When the upper case 11a is removed, the crankshaft 18 is exposed to the outside while remaining on the lower case 11b side. Therefore, the crankshaft 18 is replaced with the lower case 11b and the mission case 17 mounted on the vehicle body frame 2. it can.

As described above, in this embodiment, not only the cylinder head 15 and the cylinder body 13 but also the upper case 11a can be immediately removed when the engine unit 10 is mounted on the vehicle. Therefore, the crankshaft can be removed without lowering the entire engine unit 10 from the frame 2. 18 can be exchanged, and the exchange work can be performed treasuredly in a short time.

In the above embodiment, the split surface 11c of the crankcase 11 is
Although it is a vertical surface, this dividing surface does not necessarily have to be vertical, and may be inclined so as not to interfere with the main frame 2a or the like when the upper case 11a is removed forward.

Further, in the above-described embodiment, the width dimension of the upper case 11a is smaller than the distance between the left and right down tubes 2d, but the upper case 11a is passed diagonally between the down tubes 2d. It suffices if they can be attached to and detached from the front, and the two may overlap slightly when viewed from the front.

〔The invention's effect〕

As described above, according to the frame support structure for an engine unit for a motorcycle of the present invention, the split surface of the crankcase is made to face the front of the vehicle, and the width of the first case is made substantially narrower than the distance between the down tubes. Therefore, the crankshaft can be replaced without removing the entire engine unit, and the working time can be significantly shortened.

[Brief description of drawings]

1 to 4 are views for explaining a frame support structure of an engine unit according to an embodiment of the present invention. FIG. 1 is a front view, FIG. 2 is a right side view, and FIG. 3 is a left side. FIG. 4 is a left side view of the motorcycle to which the embodiment is applied. In the figure, 1 is a motorcycle, 2 is a body frame, 2d is a down tube, 10 is an engine unit, 11 is a crankcase, 11a is an upper case (first case), 11b is a lower case (second case), and 11c is a division. A surface, 13 is a cylinder body, 17 is a mission case, and 18 is a crankshaft.

Claims (1)

(57) [Claims] 1. A mission in which a crankcase is divided into a first case and a second case at a division surface including a crankshaft, a cylinder body is connected to the first case, and a transmission gear device is accommodated in the second case. In a support structure for mounting a motorcycle engine unit having a case integrally formed on a vehicle body frame having a pair of left and right down tubes, the first case side portion is mounted on the left side of the engine unit. , The front side of the vehicle is divided in such a manner that the front side can be attached and detached between the right and left down tubes, and the width of the first case is substantially narrower than the distance between the left and right down tubes. Frame support structure for motorcycle engine units.