Split operation type multi-cylinder internal combustion engine

An internal combustion engine having a plurality of cylinders which is divided into a first cylinder group and a second cylinder group. The engine comprises first and second air control means for controlling an amount of intake air fed into the first and second cylinder groups, respectively, and first and second fuel supply means for supplying the first and second cylinder groups with fuel. The second air control means allows inflow of air into the second cylinder group when the level of the load of the engine is lower than a predetermined level. The second fuel supply means supplies an amount of fuel in accordance with the amount of intake air passing through a second intake passage of the second cylinder group when the level of the load of the engine is higher than the predetermined level, and stops the fuel supplying operation when the level of the load of the engine is lower than the predetermined level. The engine further comprises an actuating means for increasing an amount of intake air passing through the first air control means in accordance with an increase in the level of the load of the engine, and for increasing an amount of intake air passing through the second air control means in accordance with an increase in the level of the load of the engine when the level of the load of the engine exceeds the predetermined level. The increasing speed of the amount of intake air passing through the second air control means is controlled higher than the increasing speed of the amount of intake air passing through the first air control means.

DESCRIPTION OF THE INVENTION 
The present invention relates to a split operation type multi-cylinder 
internal combustion engine having a number of cylinders divided into a 
plurality of groups, in which the respective cylinder groups are 
separately controlled according to the level of a load of the engine. 
In multi-cylinder internal combustion engines used as engines for 
automobiles, control of the amount of air introduced into all of the 
cylinders is collectively performed by a single throttle valve disposed in 
an intake passage of the engine. In some cases, a plurality of throttle 
valves is used for respective cylinders or respective groups of cylinders. 
However, in this case, these throttle valves are connected so that the 
opening degree thereof is always the same for all of the throttle valves. 
Therefore, in an internal combustion engine equipped with such throttle 
valves, the amount of intake air sucked into each of the cylinders, 
namely, the level of the load of each cylinder is the same. 
Generally, an autombile engine is kept in the ordinary operating condition 
during a substantial part of the driving period. The level of a load of 
the engine required during this ordinary operating condition is much lower 
than the maximum load level. Therefore, in an engine of this type, the 
value corresponding to the opening degree of the throttle valve is usually 
kept relatively small. 
During the light load condition where the opening degree of the throttle 
valve is small and the amount of air introduced into the engine is small, 
since a great loss of work (pumping loss) is caused at the time of the 
intake stroke, the specific fuel consumption is increased. On the other 
hand, this specific fuel consumption is gradually reduced as the load of 
the engine is increased, in other words, as the opening degree of the 
throttle valve is increased. For the above-mentioned reason, conventional 
automobile engines cannot prevent the increase of the specific fuel 
consumption. 
In order to eliminate the above-mentioned problem, various proposals have 
been made on the split operation type engine in which only some cylinders 
are actuated under a light load. 
An object of the present invention is to further improve the internal 
combustion engines of the split operation type internal combustion engine 
having a simple structure in which the pumping loss can be further reduced 
and, hence, the specific fuel consumption can be remarkably decreased. 
According to the present invention, there is provided an internal 
combustion engine having a plurality of cylinders which are divided into a 
first cylinder group and a second cylinder group, the first cylinder group 
having a first intake passage, the second cylinder group having a second 
intake passage. The engine comprises: a first air control means arranged 
in the first intake passage for controlling an amount of intake air fed 
into the first cylinder group; a first fuel supply means for supplying the 
first cylinder group with an amount of fuel in accordance with the amount 
of intake air passing through the first intake passage; a second air 
control means for controlling an amount of intake air fed into the second 
cylinder group, the second air control means allowing an inflow of air 
into the second cylinder group when the level of a load of the engine is 
lower than a predetermined level; a second fuel supply means for supplying 
the second cylinder group with an amount of fuel in accordance with the 
amount of intake air passing through the second intake passage, the 
above-mentioned fuel supplying operation being carried out when the level 
of the load of the engine is higher than the predetermined level, the 
second fuel supply means stopping the above-mentioned fuel supplying 
operation into the second cylinder group when the level of the load of the 
engine is lower than the predetermined level; and, an actuating means for 
increasing an amount of intake air passing through the first air control 
means in accordance with an increase in the level of the load of the 
engine, and for increasing an amount of intake air passing through the 
second air control means in accordance with an increase in the level of 
the load of the engine when the level of the load of the engine exceeds 
the predetermined level, the increasing speed of the amount of intake air 
passing through the second air control means being controlled higher than 
the increasing speed of the amount of intake air passing through the first 
air control means. 
The above-mentioned and other related objects and features of the present 
invention will be apparent from the following description of the present 
invention with reference to the accompanying drawings, as well as from the 
appended claims.

DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 shows a schematic view of an embodiment of an internal combustion 
engine according to the present invention. Referring to FIG. 1, reference 
numerals 1a, 1b, 1c, 1d, 1e, 1f each represents a cylinder, 3a, 3b, 3c, 
3d, 3e, 3f intake ports of cylinders 1a, 1b, 1c, 1d, 1e, 1f, respectively, 
and 2a, 2b, 2c, 2d, 2e, 2f fuel injection valves mounted on intake ports 
3a, 3b, 3c, 3d,3e, 3f, respectively. The cylinders 1a, 1b, 1c constitute a 
first cylinder group, and the cylinders 1d, 1e, 1f constitute a second 
cylinder group. The first and second cylinder groups are provided with 
first and second intake passages 16a and 16b having surge tanks 4a and 4b, 
throttle valves 5a and 5b, and air flow meters 7 a and 7b arranged in the 
intake passages 16a and 16b upstream of the throttle valves 5a and 5b, 
respectively. A common air cleaner is provided for the intake passages 16a 
and 16b. Electrical computers 8a and 8b are provided for the first and 
second cylinder groups, respectively. Electronic fuel injection control 
device comprising, as the main members, the computers 8a and 8b, the air 
flow meters 7a and 7b, and the fuel injection valves 2a through 2f are 
well known in the art of the present invention. In this embodiment, such 
electronic fuel injection control device is employed for each of the first 
and second cylinder groups. A fuel such as gasoline is fed under pressure 
to the fuel injection valves 2a through 2f from a fuel supply device (not 
shown). Fuel injection valves 2a through 2f are opened only when signals 
are applied from the computers 8a and 8b. In this case, the computers 8a 
and 8b calculate the amount of fuel to be injected into the respective 
cylinder groups in accordance with the level of air flow signals fed from 
the respective air flow meters 7a and 7b, which level corresponds to the 
amount of air sucked into the engine. Then, the computers 8a and 8b supply 
the fuel injection valves 2a through 2f with driving signals having 
durations corresponding to the calculated amount of fuel to be injected 
into the engine, via lines 31a and 31b, respectively. 
A throttle position switch 6 for detecting that the opening degree of the 
throttle valve 5a arranged in the intake passage 16a exceeds a 
predetermined value is connected to the throttle valve 5a. A relay switch 
30 is inserted into the line 31b which electrically connects the air flow 
meter 7b with the computer 8b. When the level of the output signal fed 
from the throttle position switch 6 is low, namely, when the opening 
degree of the throttle valve 5a is below the predetermined value, the 
relay switch 30 opens; thereby no signal is applied to the computer 8b 
from the air flow meter 7b. 
The throttle valves 5a and 5b are co-operatively connected to each other, 
and they are arranged so that their rotational speeds are different from 
each other. FIG. 2 illustrates one embodiment of this throttle valve 
actuating mechanism. In FIG. 2, pulleys 11 and 12 are coaxially fixed to 
the throttle valve 5a in the first intake passage 16a (shown in FIG. 1), 
and these pulleys 11 and 12 are rotated with the throttle valve 5a when an 
accelerator wire 15 connected to an accelerator pedal (not shown) is 
pulled in a direction of arrow A. A pulley 13 is coaxially fixed to the 
throttle valve 5b in the second intake passage 16b (shown in FIG. 1). This 
pulley 13 is engaged with the pulley 12 through a wire 14. The ratio of 
the radius of the pulley 12 to the radius of the pulley 13 is adjusted to 
2:1. A return spring (not shown) and a stopper (not shown) are mounted on 
each of the throttle valves 5a and 5b so that when an extent of the 
depression of the accelerator pedal is zero, the throttle valve 5a is in 
the fully closed state, namely, at the idling position, and the throttle 
valve 5b is in the fully opened state. As the extent of the depression of 
the accelerator pedal is increased, in other words, as the level of a load 
of the engine is increased, the throttle valve 5b is gradually turned in a 
closing direction while the throttle valve 5a is gradually turned in an 
opening direction. When the depression of the accelerator pedal is about 
1/2 of the maximum depression extent, the throttle valve 5b is in the 
fully closed state; when the depression is further increased, both the 
throttle valves 5a and 5b are gradually opened; and when the depression of 
the accelerator pedal reaches maximum, both the throttle valves 5a and 5b 
are fully opened. This relation of the extent of depression of the 
accelerator pedal (the load of the engine) to the opening degree of the 
throttle valves 5a and 5b is illustrated in FIG. 3, in which the abscissa 
indicates the engine load, the ordinate indicates the degree of opening in 
the throttle valve, the solid line B shows the characteristic of the 
throttle valve 5a and the broken line C shows the characteristic of the 
throttle valve 5b. 
FIG. 4 is a schematic view illustrating the structure of the throttle 
position switch 6 in the above-mentioned embodiment of FIG. 1. Referring 
to FIG. 4, reference numeral 23 designates a cam coaxially fixed to the 
throttle valve 5a, 24, 25 contacts, and 26 an insulator inserted between 
the contacts 24 and 25. When the throttle valve 5a is turned in a 
direction of arrow D, the contact 25 is pushed up by the cam 23 and the 
contact 24 falls in contact with the contact 25 to attain a conducting 
state. Accordingly, a voltage from a battery 27 is applied to the relay 
switch 30 (shown in FIG. 1) via a line 28. By appropriately selecting the 
shape of the cam 23 and the attachment angle of the cam 23 to the throttle 
valve 5a, the conducting state between the contacts 24 and 25 can be 
attained between an optional range of the opening degree of the throttle 
valve 5a. In the present embodiment, the shape of the cam 23 and the 
attachment angle of the cam 23 to the throttle valve 5a are arranged so 
that the conducting state is kept within the range from the point where 
the throttle valve 5a is half-opened to the point where the throttle valve 
5a is fully opened. 
The operation of the apparatus of the embodiment shown in FIG. 1 will now 
be described. When no depression of the accelerator pedal is effected, the 
throttle valve 5a in the first intake passage 16a is fully closed and 
stays at the idling position, as pointed out hereinbefore. In this case, a 
fuel for the idling operation is fed to the cylinders of the first group 
in a quantity corresponding to the signal from the air flow meter 7a, but 
since the output signal fed from the throttle position switch 6 is low and 
the signal from the air flow meter 7b is thus cut off by the relay switch 
30, the fuel is not fed to the cylinders of the second group. As the 
extent of depression of the accelerator pedal is increased, in other 
words, the level of a load of the engine is increased, the amount of 
intake air passing through the intake passage 16a is increased, and 
thereby the level of the output signal voltage of the air flow meter 7a is 
elevated according to the degree of opening in the throttle valve 5a. As a 
result, fuel is fed to the cylinders of the first group in a quantity 
corresponding to the level of the signal voltage fed from the air flow 
meter 7a. In the second cylinder group, the throttle valve 5b is gradually 
closed, and since the throttle position switch 6 is still in the 
non-conducting state, fuel is not fed to the cylinders. 
When the extent of the depression of the accelerator pedal is increased to 
about 1/2 of the maximum depression extent, the level of the output signal 
of the throttle position switch 6 changed to a high level so as to 
initiate feeding of the fuel to the cylinders of the second group. At this 
point when the extent of the depression of the accelerator pedal is about 
1/2 of the maximum depression extent, the throttle valve 5b is fully 
closed. When the extent of the depression of the accelerator pedal is 
further increased, the opening degree is increased in each of the throttle 
valves 5a and 5b in the first and second intake passages 16a and 16b, and 
the fuel is fed to the cylinder groups in quantities corresponding to the 
amount of intake air passing through the intake passages 16a and 16b, 
respectively. 
FIG. 5 is a schematic view illustrating the structure of another embodiment 
of the present invention. In this embodiment, the present invention is 
employed in a carburetor type internal combustion engine having six 
cylinders. In FIG. 5, reference numerals 1a, 1b, 1c, 1d, 1e, 1f represent 
the same cylinders as those in FIG. 1. The cylinders 1a, 1b, 1c constitute 
a first cylinder group and the cylinders 1d, 1e, 1f constitute a second 
cylinder group. Reference numerals 51a and 51b represent intake manifolds, 
54a and 54b first and second intake passages, and 52a and 52b throttle 
valves arranged in the intake passages 54a and 54b, respectively. 
Reference numeral 53 represents a bypass passage for communicating the 
atmosphere with the second intake passage 54b at a position downstream of 
the throttle valve 52b, and 52c an air control valve arranged in the 
bypass passage 53 so as to adjust the amount of intake air passing through 
the bypass passage 53. This air control valve 52c is opened or closed by 
the operation of a diaphragm type actuator 55. More specifically, this 
actuator 55 is arranged so that when the sucking force applied to a 
diaphragm 55c caused by the vacuum pressure in a vacuum chamber 55a is 
greater than the pressing force applied to the diaphragm 55c by a spring 
55b, the air control valve 52c is fully opened and when the sucking force 
of the above-mentioned vacuum pressure is smaller than the pressing force 
of the spring 55b, the air control valve 52c is fully closed. The vacuum 
chamber 55a of the actuator 55 can be communicated with the intake 
manifold 51a of the first intake passage 54a via a vacuum pressure conduit 
59 and further with the atmosphere through a conduit 60. A three-port type 
electromagnetic valve 56 is disposed in the midway of the vacuum pressure 
conduit 59 by connecting the two ports thereof with the conduit 59, and 
the remaining port of the electromagnetic valve 56 is opened to the 
atmosphere via the conduit 60. A battery 58 and an engine temperature 
sensor 57 are connected in series to an exciting coil 56a of the 
electromagnetic valve 56. When the engine is warmed and the temperature of 
the engine is sufficiently high, this engine temperature sensor 57 is 
closed so as to energize the electromagnetic valve 56, and the vacuum 
chamber 55a of the actuator 55 is communicated with the intake manifold 
51a of the first intake passage 54a. On the other hand, when the 
temperature of the engine is low, the engine temperature sensor 57 is 
opened, and the vacuum chamber 55a is opened to the atmosphere via the 
conduit 60. 
FIG. 6 is a side view illustrating a mechanism for co-operatively actuating 
the throttle valves 52a and 52b. Referring to FIG. 6, a pulley 61 is 
rotated by the accelerator wire 15 connected to the accelerator pedal. An 
intermediate gear 62 is connected coaxially and rotatably with the pulley 
61. An arcuate slit 63 is formed on the side face of the gear 62 along the 
circumferential direction, and a projecting pin 64 fixed to the side 
portion of the pulley 61 is slidably fitted in this slit 63. Reference 
numeral 66 represents another intermediate gear. A slit 67 extending in 
the radial direction of the gear 66 is formed on the side face of the gear 
66. A projecting pin 65 fixed to the side portion of the pulley 61 is 
slidably fitted in this slit 67. The intermediate gear 66 is engaged with 
a gear 68 fixed coaxially to the throttle valve 52a in the first intake 
passage 54a. The intermediate gear 62 is engaged with a gear 69 fixed 
coaxially to the throttle valve 52b in the second intake passage 54b. A 
return spring (not shown) and a stopper (not shown) are mounted on each of 
the throttle valves 52a and 52b. 
When no depression of the accelerator pedal is effected, the throttle valve 
52a is substantially fully closed, and the slit 65 is located horizontally 
in FIG. 6, and furthermore, the pin 64 is located on the right end of the 
arcuate slit 63 in FIG. 6. Accordingly, also the throttle valve 52b is 
substantially fully closed. As the extent of the depression of the 
accelerator pedal is increased, the throttle valve 52a is abruptly opened 
at first and the rotational speed is gradually lowered. The rotational 
speed of the throttle valve 52a in this initial stage can optionally be 
controlled by adjusting the distance between the centers of the pulley 61 
and gear 66, and also adjusting the position of the pin 65. When the 
extent of the depression of the accelerator pedal exceeds a predetermined 
level, the pin 64 reaches to the left end of the arcuate slit 63, and the 
gear 62 is allowed to rotate together with the pulley 61. Accordingly, the 
throttle valve 52b which was kept fully closed during the first half of 
the rotation of the pulley 61 begins to open in direct proportion to the 
extent of the depression of the accelerator pedal. When the extent of the 
depression of the accelerator pedal reaches maximum, both the throttle 
valves 52a and 52b are fully opened. Incidentally, the rotation angle of 
the gear 66 is considerably smaller than 90.degree., but if the radius 
ratio of the gear 66 to the gear 68 is appropriately set, a sufficient 
degree of opening can be provided for the throttle valve 52a. 
FIG. 7 is a graph illustrating the above-mentioned characteristics of the 
opening degrees of the throttle valves 52a and 52b. In FIG. 7, the 
abscissa indicates the engine load, the ordinate indicates the degree of 
opening in the throttle valve, the solid line E shows the characteristic 
of the throttle valve 52a, and the broken line F shows the characteristic 
of the throttle valve 52b. 
The operation of the latter embodiment will now be described. When no 
depression of the accelerator pedal is effected, the throttle valve 52a is 
substantially fully closed, namely stays at the idling position, as 
pointed out hereinbefore, and a fuel for idling operation is fed to the 
cylinders of the first group as in conventional carburetor engines. Also, 
the throttle valve 52b for the cylinders of the second group is 
substantially fully closed. However, since the level of the vacuum 
pressure in the intake manifold 51a in the first intake passage 54a is 
high, the air control valve 52c is fully opened. In this case, since air 
is not allowed to flow through a carburetor 50 which is arranged in the 
second intake passage 54b upstream of the throttle valve 52b, fuel is not 
fed to the cylinders of the second group. In other words, in the cylinders 
of the second group, the air intake passage is fully opened but the fuel 
is not fed. As the extent of the depression of the accelerator pedal is 
increased, in the initial state, the throttle valve 52a is abruptly opened 
so as to increase the load of the cylinders of the first group; but in the 
cylinders of the second group, the throttle valve 52b is still 
substantially fully closed and air control valve 52c is fully opened. When 
the extent of the depression of the accelerator pedal is further increased 
so as to considerably increase the opening degree of the throttle valve 
52a, the level of the vacuum pressure in the intake manifold 51a of the 
first intake passage 54a becomes closer to the atmospheric pressure level 
beyond the predetermined value, for example, -150 mHg. As a result, the 
air control valve 52c of the bypass passage 53 fully closes, and thereby 
air begins to flow from a slight clearance of the throttle valve 52b. 
Then, the carburetor 50 in the second intake passage 54b initiates feeding 
of fuel. Accordingly, the cylinders of the second group will start the 
firing operation. 
When the extent of the depression of the accelerator pedal is further 
increased, the throttle valve 52b is accordingly opened and the air 
control valve 52c is kept fully closed. Therefore, the cylinders of the 
second group are also operated in accordance with the amount of intake 
air. 
The foregoing operation is conducted when the engine is sufficiently warmed 
and the engine temperature sensor 57 is closed. As the start of the 
engine, since the temperature of the engine, for example, the temperature 
of the cooling water, is low, the engine temperature sensor 57 is opened 
as pointed out hereinbefore, and the atmospheric pressure is applied to 
the vacuum chamber 55a of the actuator 55 by the action of the 
electromagnetic valve 56. Accordingly, the air control valve 52c is always 
kept fully closed. Therefore, the fuel is also fed to the cylinders of the 
second group through the carburetor 50 from the beginning, and hence, the 
operation stability of the engine in the cold state is improved. When the 
temperature of the engine is elevated beyond a predetermined level, the 
engine temperature sensor 57 is closed and the above-mentioned normal 
operation is conducted. 
In the embodiment having the structure shown in FIG. 5, although only the 
cylinders of the first group are operated while the extent of the 
depression of the accelerator pedal (namely, the level of the engine load) 
is small, but in this case, since the opening degree of the throttle valve 
52a is abruptly increased in the initial stage, the operation 
characteristic of the engine can be remarkably improved. 
In the embodiment shown in FIG. 5, carburetors are employed. However, in an 
engine having the bypass intake air passage, an air flow meter, a computer 
and fuel injection valves are appropriately employed instead of the 
carburetor. Namely, the fuel injection type engine can also be adopted in 
the embodiment shown in FIG. 5. 
In each of the foregoing embodiments, six cylinders are divided into two 
groups. As will be apparent to those skilled in the art, the present 
invention can similarly be applied to embodiments in which a number of 
cylinders are divided into three or more groups. In these embodiments, 
from the viewpoint of preventing engine vibrations, from occurring, it is 
preferred that the cylinders of the respective groups be alternately 
ignited. In the case of V type engine, or flat and opposed type engine, 
from the viewpoint of facility in designing, it is preferred that all 
cylinders be divided into groups of each rows. 
As will readily be understood from the foregoing illustration, in the 
internal combustion engine according to the present invention, when the 
required load of the engine is small, only some of the cylinders are 
ignited and operated and the amount of intake air is increased for the 
remaining de-energized cylinders by keeping the throttle valve or the air 
control valve fully open. Accordingly, the load on the energized cylinders 
is increased but the pumping loss in the de-energized cylinders is 
reduced. Therefore, in the present invention, the specific fuel 
consumption can be maintained at a level much lower than in conventional 
engines where a uniform load is imposed on all of the cylinders. 
Furthermore, when the required load is large, since all the cylinders are 
operated, the maximum power of the engine can be readily obtained. 
Moreover, in the present invention, these excellent effects can be 
attained by using a very simple structure. 
As many widely different embodiments of the present invention may be 
constructed without departing from the spirit and scope of the present 
invention, it should be understood that the present invention is not 
limited to the specific embodiments described in this specification, 
except as defined in the appended claims.