JPH055418A - Four cycle, multiple cylinder engine - Google Patents

Abstract

PURPOSE:To increase the engine output for the entire range of an engine speed by connecting together exhaust pipes of respective cylinders by means of connecting pipes, arranging exhaust system control valves which are opened when the engine speed is low so that the exhaust pipes are connected together, providing a rocker arm for a low speed and one for an intermediate/high speed in a valve system device and by switching the rocker arms in response to the engine speed. CONSTITUTION:Exhaust pipes 17, which are introduced out of respecliro cylinders of a four-cycle, multiple cylinder engine, are connected together by means of a connecting pipe 52, which is provided with an exhaust system control valve 57. This exhaust system control valve 57 is controlled so as to be opened or closed in response to the engine speed. In other words, the valve 57 is opened when the engine speed is low, so that both exhaust-and filling-efficiency is enhanced, owing to mutual interference of exhaust pressure pulsating waves. Meanwhile, a valve system device 20 is constituted of a low speed rocker arm 32 which is inserted into a rocker shaft 31 and driven by a low speed cam 27, and intermediate/high speed, rocker arms 33, 34 which are driven by intermediate/high speed cams 28, 29 inserted into an eccentric, large diameter part of a rocker shaft 31. Both rocker arms 32 and 33 (34) are switched in response to the engine speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 4-cycle multi-cylinder engine, and more particularly to a 4-cycle multi-cylinder engine in which an exhaust system control device is installed in an exhaust pipe led from each cylinder.

[0002]

2. Description of the Related Art A conventional 4-cycle multi-cylinder engine is
There is a system in which an exhaust system control device is installed in an exhaust pipe led out from each cylinder. In this exhaust system control device, a plurality of exhaust pipes are connected by a connecting pipe, and an exhaust system control valve is installed in the connecting pipe. In this exhaust system control device, the exhaust system control valve is opened / closed in accordance with the engine speed, and when the valve is opened, the output characteristics of the engine are improved by mutual interference of the exhaust pressure pulsating waves.

[0003]

However, in a four-cycle multi-cylinder engine equipped with the exhaust system control device as described above, the engine output can be improved. Therefore, the engine output cannot be significantly improved.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a four-cycle multi-cylinder engine capable of significantly improving the engine output over the entire engine speed range. To do.

[0005]

According to the present invention, a plurality of exhaust pipes derived from respective cylinders of a four-cycle multi-cylinder engine are connected by a connecting pipe, and the connecting pipe is opened / closed in accordance with the engine speed. An exhaust system control device is configured by installing a controlled exhaust system control valve, and a valve operating device for driving the intake / exhaust valve of the 4-cycle multi-cylinder engine is directly inserted into a rocker shaft for low speed operation. A low speed rocker arm driven by a cam, and a medium and high speed rocker arm which is fitted into an eccentric large diameter portion of the rocker shaft and driven by a medium and high speed cam. The operation of the rocker arm and the operation of the medium-high speed rocker arm by the medium-high speed cam cause the rotation of the rocker shaft according to the engine speed. Ri is configured selectively to switched as,
It is characterized in that opening / closing of the exhaust system control valve and switching of the cam of the valve operating device are controlled in association with each other.

[0006]

Therefore, according to the four-cycle multi-cylinder engine according to the present invention, the exhaust system control valve is opened at the time of low engine speed to make a plurality of exhaust pipes communicate with each other, and the mutual interference of the exhaust pressure pulsating waves is utilized. Exhaust efficiency and charging efficiency to improve engine output. In addition, the valve operating device changes the type of cam according to the engine speed, realizes the valve timing and valve lift amount of the intake and exhaust valves suitable for all engine speeds, and improves the engine output. .. By controlling the opening / closing of the exhaust system control valve and the switching of the cam of the valve operating system in association with each other, the engine output can be significantly improved as compared with the case where these are used alone.

[0007]

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

FIG. 2 is a side view showing an embodiment of a 4-cycle multi-cylinder engine according to the present invention.

The engine unit 1 includes a crankcase 2
And a cylinder 3 that stands upright on the crankcase 2 and extends in the vehicle width direction. The cylinder 3 is configured by sequentially combining a cylinder block 4, a cylinder head 5, and a head cover 6 from below, and one or more cylinders (not shown) are formed in the cylinder block 4. In this embodiment, four upright cylinders are formed in the cylinder block 4.

A combustion chamber 7 (FIGS. 3 and 4) is formed in each cylinder of the cylinder head 5, and two intake ports 8 and two exhaust ports 9 are opened in each combustion chamber 7. Further, in the cylinder head 5, an intake passage 10 and an exhaust passage 11 which are respectively connected to the intake port 8 and the exhaust port 9 are formed for each combustion chamber 7. In the intake passage 10 and the exhaust passage 11, the intake port 8,
Partition walls 12 and 13 are formed in the vicinity of the exhaust port 9, and the partition walls 12 and 13 serve as branch passages.

At the upstream ends of the four intake passages 10 formed in the cylinder head 5, the intake pipe 14 shown in FIG.
The carburetor 15 and the air cleaner 16 are sequentially connected, and these 15 and 16 introduce the air-fuel mixture into the combustion chamber 7 through the intake passage 10.

The exhaust pipes 17 shown in FIG. 2 are connected to the downstream ends of the four exhaust passages formed in the cylinder head 5. Each exhaust pipe 17 is connected to the engine unit 1
Of the engine unit 1
After being connected to the collecting pipe 18 under the
Divide into and open to the rear.

By the way, as shown in FIGS. 3 and 4,
The intake boat 8 and the exhaust port 9 are opened and closed by an intake valve 21 and an exhaust valve 22, respectively. The intake valve 21 and the exhaust valve 22 are slidably inserted into a valve guide 23 provided on the cylinder head 5, and are constantly urged upward by a valve spring 24. The valve characteristic variable valve operating device 20 shown in FIG. 5 controls opening / closing of the intake valve 21 and the exhaust valve 22.

The variable valve characteristic valve operating device 20 is rotatably supported between a cam shaft journal portion 25 of a cylinder head 5 and a cam shaft journal housing (not shown), and is used for a low speed cam 27 and a medium and high speed. A camshaft 30 provided with cams 28 and 29, a rocker shaft 31 rotatably fitted in the lower part of the camshaft journal portion 25 of the cylinder head 5 to form an eccentric large diameter portion, and the rocker shaft 31 directly The low-speed rocker arm 32 inserted, the low-speed rocker arm 32 on both sides of the low-speed rocker arm 32 in the rocker shaft 31, and the medium-high speed rocker arms 33 and 34 inserted in the eccentric large-diameter portion, and the rocker for rotating the rocker shaft 31. Hydraulic cylinder 3 as shaft rotation drive source
5 and.

Two camshafts 30 are arranged, one in front of the cylinder head 5 and one in front of the vehicle, extending in the vehicle width direction. The front camshaft 30 drives the exhaust valve 22, and the rear camshaft 30. Is for driving the intake valve 21. Each cam shaft 30 is formed with one set of cam units in which medium speed cams 28 and 29 are arranged on both sides of the low speed cam 27 by the number of cylinders (that is, the number of combustion chambers 7). In this embodiment, four sets are formed. Each camshaft 30 is rotated by a crankshaft (not shown) housed in the crankcase 2 of the engine unit 1 via a cam chain (not shown).

The medium and high speed cams 28 and 29 have the same cam profile. The low speed cam 27 has a cam profile different from the cam profiles of the middle and high speed cams 28 and 29. In other words, the cam profile for the low speed cam 27 is formed so that a suitable valve lift amount and valve lift timing can be obtained when the engine is operating in the low speed range.
The middle and high speed cams 28 and 29 are
The cam profile is formed so that an appropriate valve lift amount and valve lift timing can be obtained when operating in a high speed range.

A total of four rocker shafts 31 are arranged on the front and rear of the cylinder head 5 on the left and right sides of the vehicle in the vehicle width direction. It is provided in place. Two sets of low speed rocker arms 32 and medium and high speed rocker arms 33 and 34 are installed on one rocker shaft 31. The positions of the low speed rocker arm 32 and the medium and high speed rocker arms 33 and 34 of each set are regulated together with the rocker shaft 31 by a positioning spring (not shown) interposed in the rocker shaft 31.

As shown in FIGS. 5 and 6, the tip end of the low speed rocker arm 32 is branched into two, and both branch tip ends 32b are brought into contact with the intake valve 21 or the exhaust valve 22 through a shim 37. It Further, the support portion 32a of the low speed rocker arm 32 is directly fitted into the rocker shaft 31, and the low speed rocker arm 32 has a cam floor surface 32c formed between the branch tip portion 32b and the support portion 32a.

Supporting portion 33a of the rocker arm 33 for medium and high speeds
Is an eccentric bush 38 having a diameter larger than that of the rocker shaft 31.
It is rotatably fitted in the rocker shaft 31 via. As shown in FIGS. 3 and 4, the eccentric bush 38 has an axis of the outer peripheral surface eccentric from the center of the rocker shaft 31, and is detachably fixed to the rocker shaft 31 by a positioning fixing pin 40. Therefore, the eccentric bush 38 functions as an eccentric large-diameter portion of the rocker shaft 31.

As shown in FIG. 6, the support portion 34a of the rocker arm 34 for medium and high speed also has the same shape as the eccentric bush 38 and is eccentric in the same direction.
It is rotatably fitted in the rocker shaft 31 via. The eccentric bush 39 also has a positioning fixing pin 40.
(Figs. 3 and 4), it is detachably fixed to the rocker shaft 31 and functions as an eccentric large-diameter portion.

The lower surfaces of the tip portions 33b and 34b of the medium- and high-speed rocker arms 33 and 34 are provided on one side or the other side of the branch tip portion 32b of the low-speed rocker arm 32, respectively.
The shims 41 are brought into contact with each other. Medium and high speed cam 3
The cam floor surfaces 33c and 34c are provided between the tip portions 33b and 34b and the support portions 33a and 34a, respectively.
Is formed. The contact point between the branch tip portion 32b of the low speed rocker arm 32 and the tip portions 33b and 34b of the medium and high speed rocker arms 33 and 34 is the intake valve 21.
Alternatively, it is set substantially on the axis of the exhaust valve 22.

Therefore, as shown in FIG. 3, the low speed cam 27 is provided on the cam floor surface 32c of the low speed rocker arm 32.
When the low speed cam 27 is operated by pushing down and lowering each branch tip 32b thereof, the rocker arms 33 and 3
The tip portions 33b and 34b of No. 4 follow the branch tip portion 32b by gravity and descend. On the other hand, as shown in FIG. 4, the middle and high speed cams 28 and 29 are connected to the cam floor surfaces 33c and 34 of the middle and high speed rocker arms 33 and 34, respectively.
When the middle and high speed cams 28 and 29, which are respectively depressed by c, are actuated, the tip portions 33b and 34b of the middle and high speed rocker arms 33 and 34 push down the respective branch tip portions 32b of the low speed rocker arm 32. The part 32b is forcibly lowered.

The hydraulic cylinder 35 shown in FIG. 5 is installed in a cam chain chamber (not shown) in the cylinder head 5. The same number of pistons (not shown) as the rocker shaft 31 are housed in the hydraulic cylinder 35, and the rack 43 is connected to each piston. These racks 43
Is engaged with a pinion 44 formed at one end of the rocker shaft 31. Further, the hydraulic cylinder 35 is provided with a low-speed hydraulic port 45 and a medium-high speed hydraulic port 46, respectively, and the hydraulic pressure from the engine is selectively guided to the respective ports 45, 46, so that each piston, that is, the rack 43. Reciprocates.

When the engine speed is in the low speed range, hydraulic pressure is supplied to the low speed hydraulic port 45, and the rack 4 is rotated.
3 is pulled back, the pinion 44 is rotated in the direction of arrow O (FIG. 5), and the eccentric bushes 38 and 39 have their thickened top portions 38a and 39a positioned at the center of the front-rear direction of the engine, as shown in FIG. To rotate. As a result, the cam floor surface 33 of the rocker arms 33 and 34 for medium and high speed
c and 34c move downward relative to the cam floor surface 33c of the low speed rocker arm 33, and the middle and high speed cam 2
Gaps are formed between the peripheral surfaces of 8 and 29 and the cam floor surfaces 33c and 34c of the rocker arms 33 and 34 for medium and high speeds. As a result, the middle and high speed cams 4 and 5 idle, and only the low speed cam 27 abuts on the cam floor surface 32c of the low speed rocker arm 32 and rotates. Therefore, the intake valve 21 and the exhaust valve 22 are operated by the low speed cam 27 and the low speed rocker arm 32 so that the intake port 8 and the exhaust port 9 have the valve lift timing and the valve lift amount suitable for the low engine speed range. Open and close each.

When the engine speed is in the medium-high speed range, hydraulic pressure is supplied to the medium-high speed hydraulic port 46 (FIG. 5), the rack 43 is pushed out, and the pinion 44 is in the direction of arrow P (FIG. 5). The eccentric bushes 38 and 39 are rotated so that their thick top portions 38a and 39a are positioned outward in the front-rear direction of the engine, as shown in FIG. As a result, the medium- and high-speed rocker arms 33 and 3
The cam floor surfaces 33c and 34c of No. 4 move relatively substantially upward or to the same position with respect to the cam floor surface 32c of the low speed rocker arm 32. Contact. Here, since the cam lift amounts of the middle and high speed cams 28 and 29 are formed to be larger than that of the low speed cam 27, the low speed cam 27 idles in the above state, while
Medium and high speed cams 28 and 29 are medium and high speed rocker arm 3
The cam floor surfaces 33c and 34c of 3 and 34 are brought into contact with each other and rotate. As a result, the intake valve 21 and the exhaust valve 22 are actuated at the valve lift timing and the valve lift amount suitable for the middle-high speed range of the engine by the operation of the middle-high speed cams 28, 29 and the middle-high speed rocker arms 33, 34. The port 8 and the exhaust port 9 are opened and closed respectively.

Now, as shown in FIG. 7, the exhaust pipe 17 is arranged in parallel with the cylinders in the cylinder 3 so that # 1, # 2 and # 1 are arranged from one side.
# 3 and # 4. The exhaust pipes 17 of # 2 and # 3 are connected by a connecting pipe 51, the exhaust pipes of # 1 and # 4 are connected by a connecting pipe 52, and the exhaust system control valve mechanism 52A (FIG. 1) is connected to the connecting pipe 52. It is installed. The exhaust system control device 50 is configured to include the connecting pipe 51, the connecting pipe 52, and the exhaust system control valve mechanism 52A.

As shown in FIG. 8, the connecting pipe 51 is fixed to the opposing side surfaces of # 2 and # 3 of the exhaust pipe 17, and openings 53 are formed on both side surfaces of these. Exhaust pipe 17 # 2
And # 3 are communicated with each other by the opening 53 and the connecting pipe 51.

The connecting pipe 52 is, as shown in FIG.
The exhaust pipe 17 is fixed to the facing side surfaces of # 1 and # 4, and openings 54 are formed on both side surfaces of these. Exhaust pipe 17
# 1 and # 4 of these openings 54 and the connecting pipe 5
It is communicated by two.

The exhaust system control valve mechanism 52A comprises a servo motor 55 and an exhaust system control valve 57 fixed to a rotary shaft 56 of the servo motor 55. The servomotor 55 has a mounting seat 58 fixed to the connecting pipe 52.
Further, the exhaust system control valve 57 is opened and closed by being bolted via a heat insulating material 59 and by rotating the rotating shaft 56. The tip of the rotating shaft 56 is supported by the connecting pipe 52.

The rotation control of the servo motor 55 is performed by the servo motor control signal d from the igniter 60 shown in FIG. The igniter 60 is a pickup coil 6
The engine rotation speed signal a from 1 and the carburetor opening signal b from the carburetor sensor 62 are input to output the engine ignition signal e, and the servo motor control signal d and the cam switching signal c are output to the hydraulic cylinder 35. .. The cam switching signal c controls the switching of the hydraulic pressure to the low speed hydraulic port 45 (FIG. 5) or the medium and high speed hydraulic port 46 of the hydraulic cylinder 35, and the operation of the low speed cam 27 or the medium and high speed cams 28 and 29. The operation of switches. Further, the servo motor control signal d controls the forward / reverse rotation of the servo motor 55 and the amount of rotation thereof, and controls the opening / closing of the exhaust system control valve 57 (FIG. 1).

That is, as shown in FIG. 10, the igniter 60 is configured so that the engine speed N increases when the engine speed increases.
At a rpm, the exhaust system control valve 57 is controlled to open and close from the open state to the closed state, and at low engine speed Nb (Nb> Na) rpm, the operation of the low speed cam 27 to the medium to high speed cam. Control the switching of the cam to actuation of 28 and 29. The igniter 60 is
When the engine speed drops, the engine speed Nbrpm
The cams are switched from the operation of the middle and high speed cams 28 and 29 to the operation of the low speed cam 27 at a slightly lower rotational speed, and the exhaust system control valve 57 is opened from the closed state at a rotational speed slightly lower than the engine rotational speed Narpm. Control to valve state,
We are trying to prevent hunting.

In FIG. 10, the broken line 63 is the engine output characteristic when the low speed cam 27 is operating and the exhaust system control valve 57 is open, and the alternate long and short dash line 64 is the exhaust gas when the low speed cam 27 is operating. It is an engine output characteristic when the system control valve 57 is closed. Also, the two-dot chain line 65 is
The solid line 66 indicates the engine output characteristic when the exhaust system control valve 57 is opened when the medium- and high-speed cams 28 and 29 are operating. It is an engine output characteristic at time.

Therefore, the igniter 60 opens and closes the exhaust system control valve 57 and the cams 27, 28, as described above.
When the switching of 29 is controlled, the engine output characteristic is shown by the broken line 63 at the engine speed Narpm or less, the output characteristic shown by the alternate long and short dash line 64 at the engine speed Narpm to Nbrpm, and the solid line 66 at the engine speed Nbrpm or more. It exhibits engine output characteristics. In this way, the igniter 60 controls so as to select the best output characteristic from the low speed region to the high speed region, so that the engine output as a whole can be greatly improved.

The reason why the engine output characteristics are improved by opening / closing the exhaust system control valve 57 will be described below.

Exhaust gas flowing through the exhaust pipe 17 in FIG. 7 has a crankshaft rotation angle of 1 depending on the ignition sequence of the cylinder 3.
It is carried out in the order of # 1 → # 2 → # 4 → # 3 at intervals of 80 °. Therefore, the # 2 and # 3 exhaust pipes 17 that are connected by the connecting pipe 51 are also the # 1 and # 4 exhaust pipes 17 that are connected by the connecting pipe 52 and the exhaust system control valve 57.
In both cases, the exhaust timing is shifted by 360 ° of the crankshaft rotation angle. Therefore, when the engine speed is low (engine speed Narpm or less), the connecting pipe 51 causes # 2.
When the exhaust pipes # 3 and # 3 communicate with each other, the exhaust system control valve 57 is fully opened, and the exhaust pipes # 1 and # 4 communicate with each other through the connecting pipe 52, the exhaust pressure pulsation waves interfere with each other to improve exhaust efficiency and filling. Since the efficiency is increased, the output of the engine is improved. On the other hand, if the exhaust system control valve 57 is fully closed to cut off the communication between the exhaust pipes # 1 and # 4 when the engine is operating at a high speed (engine speed Narpm or more),
Since the # 1 and # 4 exhaust pipes 17 are independent of each other and the exhaust gas flows smoothly, it is possible to cope with an increase in the exhaust gas flow rate and to significantly improve the engine output.

According to the above embodiment, as described above, the cam 2
By switching between 7, 28 and 29 and connecting and disconnecting the connecting pipe 52 by opening and closing the exhaust system control valve 57, the output characteristics of the engine can be greatly improved over the entire rotational speed range.

In the above embodiment, the connecting pipe 52 is # 2.
And because it is in a hidden position in the exhaust pipe of # 3,
There is no problem in design even if the exhaust system control valve mechanism 52A is installed behind the connecting pipe 52.

In the above embodiment, the engine speed Narpm for changing the opening / closing of the exhaust system control valve 57,
Engine speed Nb for switching the cams 27, 28, 29
The case where the speed is different from the rpm is described, but the engine speed Na
The rpm may be eliminated and the switching of the cams 27, 28, 29 and the opening / closing of the exhaust system control valve 57 may be simultaneously performed at the engine speed Nbrpm. In this case, the engine output characteristic is slightly reduced, but since only one signal is output to the hydraulic cylinder 35 and the servo motor 55, the device can be simplified, and the exhaust system control valve mechanism 52A is additionally provided as an option. it can.

In the above embodiment, the exhaust system control valve mechanism 52A is installed only in the connecting pipe 52.
An exhaust system control valve mechanism similar to the exhaust system control valve mechanism 52A may be installed in the connecting pipe 51 to further improve the engine output.

[0040]

As described above, according to the four-cycle multi-cylinder engine according to the present invention, a plurality of exhaust pipes derived from the respective cylinders of the four-cycle multi-cylinder engine are connected by the connecting pipe, An exhaust system control valve, which is controlled to open and close according to the engine speed, is installed in the connecting pipe to configure an exhaust system control device, and a valve operating device for driving the intake / exhaust valve of the four-cycle multi-cylinder engine,
The rocker shaft has a low-speed rocker arm directly inserted into the rocker shaft and driven by a low-speed cam, and a medium-high speed rocker arm inserted into the eccentric large-diameter portion of the rocker shaft and driven by a medium-high speed cam. The operation of the low-speed rocker arm by the low-speed cam and the operation of the medium-high-speed rocker arm by the medium-high speed cam can be selectively switched by the rotation of the rocker shaft according to the engine speed. Since the opening / closing of the exhaust system control valve and the switching of the cam of the valve operating device are controlled in association with each other, the engine output can be greatly improved over the entire engine speed range.

[Brief description of drawings]

FIG. 1 is a cross-sectional view taken along line I-I of FIG.

FIG. 2 is a side view showing an embodiment of a 4-cycle multi-cylinder engine according to the present invention.

FIG. 3 is a cross-sectional view of the cylinder head of FIG. 2, showing an operating state of the valve gear when the engine is running at low speed.

FIG. 4 is a cross-sectional view of the cylinder head of FIG. 2, showing an operating state of the valve gear when the engine is running at a high speed.

5 is a perspective view of the valve gear shown in FIGS. 3 and 4. FIG.

6 is a plan view of the valve gear of FIG.

FIG. 7 is a view on arrow VII of FIG.

8 is a sectional view taken along the line VIII-VIII in FIG.

9 is a block diagram of a control system that controls the exhaust system control valve mechanism of FIG. 1 and the valve operating device of FIG.

10 is a graph showing the engine output shown in FIG. 2 together with the engine speed.

[Explanation of symbols]

 1 engine unit 17 exhaust pipe 20 variable valve characteristic valve operating device 21 intake valve 22 exhaust valve 27 low speed cam 28,29 medium and high speed cam 31 rocker shaft 32 low speed rocker arm 33,34 medium and high speed rocker arm 35 hydraulic cylinder 38,39 Eccentric bush 50 Exhaust system control device 51, 52 Connection pipe 52A Exhaust system control valve mechanism 57 Exhaust system control valve 60 Igniter a Engine speed signal

Claims (1)

Claim: What is claimed is: 1. A plurality of exhaust pipes derived from respective cylinders of a four-cycle multi-cylinder engine are connected by a connecting pipe, and the opening and closing of the connecting pipe is controlled according to the engine speed. The exhaust system control valve is installed to configure the exhaust system control device, and the valve operating device for driving the intake / exhaust valve of the four-cycle multi-cylinder engine is directly inserted into the rocker shaft by the low speed cam. A low-speed rocker arm to be driven, and a medium-high speed rocker arm that is inserted into the eccentric large-diameter portion of the rocker shaft and is driven by a medium-high speed cam. The operation and the operation of the middle-high speed rocker arm by the middle-high speed cam are selected by the rotation of the rocker shaft according to the engine speed. A is configured to switched, 4-cycle multi-cylinder engine and a switching cam of the opening and closing and the valve system of the exhaust system control valve is characterized by being controlled in connection.