Device for controlling number of operating cylinders of an internal combustion engine

A device for controlling a partial number of engine cylinders employs a geneva movement, intake-air-cutoff valves, an exhaust-gas-cutoff valve and a DC motor. The geneva movement divides the driving force of the DC motor into two: a force intermittently driving the intake-air-cutoff valves and a force driving the exhaust-gas-cutoff valve, so that the exhaust-gas-cutoff valve cannot open until the intake-air-cutoff valve has closed when the engine operation is changed over to a partial-cylinder-operation mode, and the intake-air-cutoff valve cannot open until the exhaust-gas-cutoff valve has closed when the engine operation is changed over to the full-cylinder-operation mode. As a result, time required for changeover of the engine operation between the full-cylinder operation and the partial-cylinder operation is minnimized and additional driving unit is omitted.

CROSS REFERENCE TO RELATED APPLICATION 
The present application is based on and claims priority from Japanese 
Patent Application No. Hei 6-128925 filed on Jun. 10, 1994, the contents 
of which are incorporated herein by reference. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a device for controlling number of 
operating cylinders of an internal combustion engine for a vehicle. 
2. Description of the Related Art 
There has been proposed a device which controls the number of operating 
cylinders of an internal combustion engine (hereinafter referred to as an 
engine) in response to the engine operating condition in order to reduce 
the fuel consumption of the vehicle engine. 
For example, Japanese Patent Apllication Laid-open No. Sho 61-118581 
discoloses a device which is equipped with a slider and a pin. The pin 
engages with or disengages from the slider in a lifter bodies of intake 
and exhaust valves. When an engine cylinder is put into operation, the pin 
is driven by an oil pressureunit to engage with the slider by an oil 
pressure to operate the intake and the exhaust valves. On the other hand 
when the pin is disengaged from the slider, the valves are put out of 
However, if the above structure is installed in an engine, it is necessary 
to change the engine structure from the ordinary engine structure to a 
considerable extent. Especially, the engine having multiple intake and 
exhaust valves for each cylinder requires a substantial alteration. 
In addition, when valves of a controlled cylinder stop its operation while 
other cylinders of the engine are running, the lubricating oil of the 
suspended cylinder is sucked out since the pressure in the controlled or 
suspended cylinder becomes negative, thereby causing insufficient 
lubrication of the cylinder. 
In order to provide the above function without considerable change of the 
driving mechanism, there has been proposed another control device which 
utilizes exhaust gas to control operation of the cylinders. 
Such device is disclosed in Japanese Utility Model Application Laid-open 
No. 60-52360. The device is equipped with an intake-air-cutoff valve which 
is driven by a motor to open or close the air-intake passage, an 
exhaust-gas-intake passage which returns the exhaust gas from the 
exhaust-side of the suspended cylinder to a downstream portion of the 
intake-air-cutoff valve and an exhaust-gas-cutoff valve which is driven by 
a driving unit to open or close the exhaust-gas-intake passage. A driving 
unit is provided in addition to a motor for driving the intake-air-cutoff 
valve. When the intake-air-cutoff valve opens and the exhaust-gas-cutoff 
valve closes, all cylinders of the engine operate. On the other hand, when 
the intake-air-cutoff valve closes and the exhaust-gas-cutoff valve opens, 
a set number of cylinders are suspended and the exhaust gases (or air) 
return through the exhaust-gas-intake passage to the suspended cylinders. 
Although the exhaust gas (or air) circulating type device described above 
does not require a considerable change from the ordinary engine structure, 
it requires two driving units and additional cost for providing the units. 
In addition, the intake-air-cutoff valve must be closed before the 
exhaust-gas-cutoff valve is opened since the pressure in the controlled or 
suspended cylinder becomes negative, in order to have the exhaust gas 
circulation in the suspended cylinder, while the exhaust-gas-cutoff valve 
must be closed before the intake-air cutoff valve is opened in order to 
restore the suspended cylinder to operation. Thus, an electronic valve 
control unit is necessary to control the sequence of the above mentioned 
valve operation, and, therefore, sensors for sensing the opening or 
closing of the valves are also necessary. 
In other words, an engine can only change over from the full-cylinder 
operation to the partial-cylinder operation after the intake-air-cutoff 
valve has been closed by the motor and subsequently the exhaust-gas-cutoff 
valve is opened by a different driving unit after the intake-air-cutoff is 
detected by the sensor, and the engine can only return to the 
full-cylinder operation after the exhaust-gas-cutoff valve has been closed 
by the different driving unit and the intake-air cutoff valve is 
subsequently opened by the motor after the exhaust-gas-cutoff state is 
detected by the sensor. 
Since it takes relatively long time for the cutoff valves and the driving 
units to operate after receiving control signals from the sensor, a 
comparatively long time period is necessary to change over the engine 
operation between the full-cylinder-engine operation and the 
partial-cylinder-engine operation. 
As a result, torque shocks, slow response or stagnation of the engine 
operation may be caused when the changeover of the engine operation 
between the full-cylinder operation and the partial cylinder operation is 
initiated. 
SUMMARY OF THE INVENTION 
The present invention is made in view of the foregoing problems, and has a 
primary object of providing an improved device for controlling number of 
operating cylinders of an engine having a simple and low cost structure. 
Another object of the present invention is to provide a highly responsive 
device for controlling number of operating cylinders of an engine which 
includes intake-air-cutoff valves, an exhaust-gas-cutoff valve, a geneva 
movement and a single driving unit for driving the valves, so that time 
required for the engine-operation-changeover between the full-cylinder 
operation and the partial-cylinder operation is significantly reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Preferred embodiments according to the present invention will now be 
described with reference to the appended drawings. 
A first embodiment of the present invention is described with reference to 
FIG. 1 through FIG. 8. 
An engine 1 has three full-time operating cylinders 2a, 2b and 2c disposed 
at the left side thereof and cylinders 3a, 3b and 3c disposed at the right 
side which are suspended when the engine operates under a partial load 
condition. Each cylinder has an air-intake valve 1a driven by a cam (not 
shown) and an exhaust valve 1b driven by another cam (not shown) and is 
supplied with fuel in a well-known manner. 
A plurality of air-intake pipes 4a, 4b, 4c, 4d, 4e and 4f (which form a 
air-intake passage of the engine 1) are disposed at one side of the engine 
1 and connect each of the cylinders (2a through 3f) to an air-intake 
manifold 5. Air or air-fuel mixture is introduced to the cylinders through 
a throttle valve 6 disposed at an upstream portion of the air-intake 
manifold 5. Exhaust manifolds 7a and 7b are disposed at the other side of 
the engine 1 and connect the left side cylinders 2a, 2b and 2c and the 
right side cylinders 3a, 3b and 3c to an exhaust pipe 9. The exhaust pipe 
9 is equipped with a catalytic converter 8 to purify the exhaust gases 
discharged from the cylinders. Each of the air-intake pipes 4d, 4e and 4f 
connects each of the right side cylinders 3a, 3b and 3c with the air 
intake manifold 5 and is equipped with each of intake-air-cutoff valves 
10a, 10b and 10c, which compose the main part of a device `A` for 
controlling number of operating cylinders (hereinafter referred to as the 
cylinder control device). Structure of the intake-air-cutoff valves 10a, 
10b and 10c is illustrated in FIGS. 3 through 6. 
In FIG. 3, the cylinder control device `A` has an air passage block in 
which a straight cylindrical space 11 is formed to intersect the 
air-intake pipes 4d, 4e and 4f and accommodate the intake-air-cutoff 
valves 10a, 10b and 10c and covers 12 disposed at the both ends thereof. 
Cylindrical bushings 15 are inserted into the space 11 so that each meets 
each of the air-intake pipes 4d, 4e and 4f. Each of the bushings 15 has a 
pair of through holes 19 open to both sides of each of the air-intake 
pipes 4d, 4e and 4f as shown in FIGS. 4 and 5. 
Valve bodies 16 are rotatably inserted into each of the cylindrical 
bushings 15. Each of the valve bodies 16 has a pair of disk-plates 18 
which slide on the inner surface of corresponding one of the bushings 15 
and a valve member 17 which connects the pair of the disk plates 18. The 
valves 10a, 10b and 10c open when the valve members 17 are placed in 
parallel with the axes of the air-intake pipes 4d, 4e and 4f (FIG. 4), and 
close when the valve members 17 are placed perpendicular to these axes 
(FIG. 5) so that the intake air flowing trough the intake pipes 4d, 4e and 
4f may be introduced and cut off. 
The valve bodies 16 are interlinked one another. Each of the disk plates 18 
has a shaft 22 which extends from the center of the outer surface. 
cylindrical spacers 23 are disposed between the valves 16 so as to fill up 
the cylindrical space 11. Joints 24 are disposed inside the spacer 23 and 
connect the shafts 22 which extend from the disk plates 18 located at the 
opposite sides. Pairs of bearings 25 are secured to the both ends of the 
spacers 23 to rotatably carry the shafts 22, so that all the valve members 
17 rotate together. 
The leftmost and the right-most shafts 22 which are the end portions of the 
intake-air-cutoff-valve-train are rotatably supported by bearings 25a 
which is disposed on the covers 12 respectively. 
The rightmost one of the shafts 22 (which is disposed outside the 
air-intake pipes) has a portion extending outside from the cover 12, and 
carries a gear 26. 
A connecting pipe 27 (FIG. 1) is disposed at a downstream portion of the 
intake-air cutoff valves 10a, 10b and 10c (engine side) in parallel with 
the intake-air-cutoff-valve train. The connecting pipe 27 connects each of 
the intake-air pipes 4d, 4e and 4f as shown in FIGS. 1 through 6. 
The connecting pipe 27 has an exhaust gas inlet 28 formed on its wall as 
shown in FIG. 4 and connects through the exhaust gas inlet 28 and an 
exhaust-gas-cutoff valve 29 to an exhaust gas circulating pipe 30 which 
branches off the exhaust manifold 7b (see FIG. 1). The exhaust gases 
discharged into the exhaust manifold 7b (from the cylinders 3a, 3b and 3c) 
are introduced to the air-intake pipes 4d, 4e and 4f through the 
circulating pipe 30, the exhaust-gas-cutoff valve 29 and the connecting 
pipe 27, which compose an exhaust-gas-intake passage 31. 
Structure of the exhaust-gas-cutoff valve 29 is described next with 
reference to FIGS. 3 through 6. 
A block member 32 is disposed under the air-intake pipes 4d, 4e and 4f, and 
a cylindrical space 33 is formed in parallel with the cylindrical space 11 
to accommodate the exhaust-gas-cutoff valve 29. A cylindrical bushing 34 
which is inserted into the space 33 has a pair of elliptic through-holes 
35a and 35b (FIG. 4 and FIG. 5) in the upper wall portion thereof and a 
wall portion perpendicular to the upper wall portion. The upper through 
hole 35a connects to the exhaust-gas inlet 28 through a passage 36 formed 
in the block member 32 and the other through hole 35b connects with the 
exhaust manifold 7b through a passage 37 formed in the block member 32 and 
the exhaust-gas circulating pipe 30. 
A generally cylindrical valve member 38 is slidably inserted into the 
bushing 34. The valve member 38 has round portions at both ends thereof, 
and a flat-bottomed rectangular groove 39 at the central portion thereof. 
A shaft 40 extends from the center of the opposite ends of the valve 
member 38 and is rotatably carried by a pair of bearings 41 which are 
secured to the block member 32 in such a manner as the intake-air-cutoff 
valves 10a, 10b and 10c are secured. 
The valve member 38 closes the through holes 35a and 35b when the valve 
member 38 rotates and the cylindrical surface (except for the groove 39) 
meets the holes 35a and 35b and opens them when the valve member 38 
rotates and the groove 39 meets the holes 35a and 35b. That is, the valve 
member 38 opens or closes the through holes 35a and 35b at a set interval 
when it rotates. Accordingly, the exhaust-gas-cutoff valve 29 opens or 
closes at the set interval. 
The left end of the shaft 40 of the exhaust-gas-cutoff valve 29 
(illustrated in FIG. 3 and in FIG. 6) connects with a rotary encoder 42 
(sensor) which detects the position of the valve member 38. 
The right end (opposite end) of the shaft 40 connects with a motor 44 such 
as a DC motor (valve driving unit) and the intake-air-cutoff valves 10a, 
10b and 10c through a geneva movement 43. The geneva movement 43 is 
disposed in a space 45 formed in the block member 32 as shown in FIG. 3. 
The geneva movement 43 has a driving shaft 46 which is disposed coaxially 
with the shaft 40 of the valve member 38 and is rotatably supported by a 
wall of the space 45, a driven shaft 47 which is disposed rotatably in the 
same space 45 in parallel with the driving shaft 46 and a pair of bearings 
48 which support both ends of the driving shaft 46 (FIG. 3). 
An end of the driving shaft 46 on the side of the exhaust-gas cutoff valve 
29 is connected with the shaft 40 of the valve member 38 by a joint 49. 
There are a driving wheel 50 and a gear 51 of the geneva movement 43 
carried on the driving shaft 46. 
As shown in FIG. 8, the driving wheel 50 of the geneva movement 43 is 
composed of a semicircular constrained cam 52 which has a flat portion and 
a crank member 54 which extends radially beyond the flat portion of the 
cam 52. The crank member 54 has a roller 55 disposed rotatably at the open 
end thereof in parallel with the cam 52. 
The gear 51 engages a pinion gear 56 which is secured to the output shaft 
of the motor 44 (FIG. 6). In other words, the driving wheel 50 of the 
geneva movement 43 and the valve member 38 of the exhaust-gas-cutoff valve 
29 are driven by the DC motor 44 via the driving shaft 46. 
The driven shaft 47 carries a driven cam 57 thereon on the side of the 
exhaust-gas-cutoff valve 29 to engage the constrained cam 52 of the 
driving wheel 50 as shown in FIG. 6. 
The semicircular driven cam 57 has a radial groove 58 and arc-shaped cam 
surfaces 59 formed on the both sides of the groove 58. 
The radial groove 58 is formed so that it may readily engage with and 
disengage from the roller 55. The cam surfaces 59 are formed to engage 
with the periphery of the constrained cam 52. The above mechanism of 
engagement of the roller 55 with the groove 58, and the constrained cam 52 
with the cam surfaces 59 as illustrated in FIG. 8 converts the rotation of 
the driving wheel into intermittent motion. 
The outside end (right side end in FIG. 3) of the driven shaft 47 extends 
from a wall of the space 45 and carries a gear 60 in engagement with the 
gear 26, so that the intermittent motion of the driven shaft 47 is 
transmitted to the valve members 16 of the intake-air-cutoff valves 10a, 
10b and 10c via the gear 60. 
As shown in FIG. 7, the operation timing (intermittent motion) of the 
geneva movement 43 is set as follows: 
the full-cylinder-operation mode (the intake-air-cutoff valve opens and the 
exhaust-gas-cutoff valve closes) is carried when the rotation angle of the 
driving shaft 46 becomes 0, 
the intake-air-cutoff valves 10a, 10b and 10c close as the rotation angle 
increases from 0.degree. to 90.degree., and 
only the exhaust-gas-cutoff valve 29 opens (the position of the 
intake-air-cutoff valves is unchanged) after the rotation angle exceeds 
90.degree. and increases up to 180.degree.. 
The operation timing of the geneva movement 43 is explained more concretely 
hereafter with reference to FIG. 8. 
When the driving shaft 46 rotates from angle 0.degree. to 90.degree., the 
geneva movement gradually closes the intake-air-valves 10a, 10b and 10c 
and maintains the exhaust-gas-cutoff valve 29 in the full-close state 
(synchronous operation). Thereafter (from angle 90.degree. to 
180.degree.), the roller 55 disengages from the groove 58 so that the 
intake-air-cutoff valve 10a, 10b and 10c maintain their full-close state 
and only the exhaust-gas-cutoff valve 29 opens the passage 37 right after 
the intake-air-cutoff valves 10a, 10b and 10c have fully closed. 
That is, when the full-cylinder-operation mode is changed over to the 
partial-cylinder-operation mode, the air-intake-pipes 4d, 4e and 4f are 
first closed before the exhaust-gas circulating pipe 30 is opened. 
Of course, the exhaust-gas-circulating pipe is first closed before the 
air-intake pipes 4d, 4e and 4f are opened when the partial-cylinder 
operation is changed over to the full-cylinder operation. 
A numeral 61 in FIG. 6 indicates a controller (such as a unit including a 
microcomputer). The controller is connected to the rotary encoder 42 and 
the DC motor 44. 
When a partial-mode-changeover signal which indicate the changeover from 
the full-cylinder-operation mode to the partial-cylinder-operation mode 
(under a partial-load engine condition) is received, the controller 61 
controls the DC motor 44 to rotate the driving shaft 46 from the angle 
0.degree. position (for the full-cylinder operation) to the angle 
180.degree. position (partial-cylinder operation). On the other hand, when 
the controller 61 receives a full-mode-changeover signal (full-load engine 
condition), it controls the DC motor 44 to rotate the driving shaft 46 
from the angle 180.degree. position to the angle 0.degree. position. 
Next, the operation of the cylinder control device `A` is explained. 
When a six-cylinder engine operates under the full-cylinder operation mode, 
the intake-air-cutoff valves 10a, 10b and 10c are fully opened and the 
exhaust-gas-cutoff valve 29 is fully closed as in FIG. 8 (0.degree.). 
In other words, the suspended cylinders 3a, 3b and 3c are connected with 
the air-intake manifold 5 and disconnected from the exhaust-gas-intake 
passage 31. Thus, all the cylinders 2a, 2b, 2c, 3a, 3b and 3c introduce 
the air from the air-intake manifold 5 therein to burn fuel and discharge 
exhaust gases during the engine combustion cycle, thereby generating a 
vehicle driving power. The exhaust gases produced by the cylinders 2a 
through 3c are discharged through the exhaust manifold 7a and 7b, the 
catalytic converter 8 and the exhaust pipe 9 to the atmosphere. Since the 
passage 31 is closed by the exhaust-gas-cutoff valve during this operation 
mode, the exhaust gases do not get into the air-intake pipes 4d, 4e and 
4f. 
When the car is driven at a light load or with a small opening angle of the 
throttle valve, the controller 61 receives a partial-mode-changeover 
signal. The controller 61 controls the DC motor 44 to rotate, for example, 
clockwise. Then, the driving torque is transmitted through the driving 
wheel 50 of the geneva movement 43, the driven cam 57, the driven shaft 47 
and the gears 60 and 26 to all the intake-air-cutoff valves 10a, 10b and 
10c to close as shown in FIG. 8. The driving torque of the DC motor 44 is 
also transmitted through the driving shaft 46 and shaft 40 to the 
exhaust-gas-cutoff valve 29 to open. 
The operation of the geneva movement 43 is further explained with reference 
to FIG. 8 next. 
When the rotation angle of the driving shaft 46 is 0.degree., only the 
periphery of the disk-shaped constrained cam 52 (of driving wheel 50) 
engages the arc-shaped cam surface 59 of the driven shaft 57 to regulate 
the motion of the driven cam 57, thereby maintaining the full-open 
position of the intake-air-cutoff valves 10a, 10b and 10c. 
The driving shaft 46 is driven by the DC motor 44 to rotate from this angle 
0.degree. position according to the mode changeover control. The 
constrained cam 52 and the driven cam 57 are held in engagement with the 
roller 55 sliding within the groove 58 until the driving shaft 46 rotates 
to angle 90.degree.. In other words, the constrained cam 52 and the driven 
cam 57 rotate as a unit until the driving shaft 46 rotates to the angle 
90.degree.. The intake-air-cutoff valves 10a, 10b and 10c changes 
gradually from the full-open state to the full-close state as the rotation 
angle increases. The exhaust-gas-cutoff valve 29 maintains its close state 
until the driving shaft rotates right after 90.degree. because of the 
specific valve structure. 
When the rotation angle becomes 90.degree., the roller 55 comes to the open 
end of the groove 58 again and leaves it, and consequently the torque 
transmission to the driven cam 57 is interrupted. Then, the arc-shaped cam 
surface of the driven cam 57 slide on the periphery of the constrained cam 
52 so that it is held at the same position as the angle 90.degree. until 
up to the angle 180.degree.. Thus, the intake-air-cutoff valve 10a, 10b 
and 10c keep closing the air-intake pipes 4d, 4e and 4f. That is, the 
intake-air-cutoff valves 10a, 10b and 10c maintain the close state after 
the angle 90.degree.. 
On the other hand, the driving shaft 46 is driven further by the DC motor 
44 to rotate the valve member 38 of the exhaust-gas-cutoff valve 29 from 
the rotation angle 90.degree. up to the angle 180.degree. so that the 
valve member 38 gradually connects the passages 36 and 37 as shown in FIG. 
8. 
When the driving shaft 46 has rotated to the angle 180.degree., the rotary 
encoder 42 detects the position of the driving shaft 46 and sends a signal 
to the controller 61, which deenergizes the DC motor to hold the 
exhaust-gas-cutoff valve in the full-open state. 
Consequently, the circulating passage which includes the cylinders 3a, 3b 
and 3c, the exhaust manifold 7b, the exhaust gas circulating pipe 30, the 
exhaust-gas-cutoff valve 29, the connecting pipe 27 and the air-intake 
pipes 4d, 4e and 4f is formed as shown in FIGS. 2 and 5. 
As a result, fresh air is cut off and exhaust gases discharged from the 
cylinders 3a, 3b and 3c into the common exhaust manifold 7b are sucked by 
the same cylinders through the exhaust-gas circulating pipe 30, the 
connecting pipe 27 and the air-intake pipes 4d, 4e and 4f, and only the 
cylinders 2a, 2b and 2c operate. 
Since the exhaust gases circulate in the cylinders 3a, 3b, and 3c, pumping 
power loss of the suspended cylinders 3a, 3b and 3c as well as the 
operating cylinders 2a, 2b and 2c (due to reduction in vacuum pressure in 
the intake manifold 5) is small, and significant improvement of the fuel 
consumption is attained. 
When the engine load increases from a light load, to a medium or full load, 
a return-mode signal is sent to the controller 61 and the partial-cylinder 
operation is changed over to the full-cylinder operation as follows. 
The controller 61 drives the DC motor to rotate in the opposite direction, 
thereby returning the driving shaft 46 to the rotation angle 0.degree. 
from the rotation angle 180.degree.. Consequently, the geneva movement 43 
returns toward the angle 0.degree. position tracing the same operations 
shown in FIG. 8, however, in the opposite direction. Thus, the 
exhaust-gas-cutoff valve 29 changes over to the close position from the 
open position as the rotation angle changes from 180.degree. to 90.degree. 
and the intake-air-cutoff valve 10a, 10b and 10c change over to the full 
open position from the full close position as the rotation angle changes 
from 90.degree. to 0.degree.. 
Thus, the suspended cylinders 3a, 3b and 3c return to operation, resulting 
in the full-cylinder engine operation. 
In summary, when the full-cylinder engine operation is changed over to the 
partial-cylinder operation, the exhaust-gas-cutoff valve 29 connects the 
exhaust gas circulating pipe 30 and the connecting pipes 27 right after 
the intake-air-cutoff valve 10a, 10b and 10c have closed the air-intake 
pipes 4d, 4e and 4f, while when the partial engine operation is changed 
over to the full-cylinder engine operation, the intake-air-cutoff valves 
10a, 10b and 10c open the air-intake pipes 4d, 4e and 4f right after the 
exhaust gas-cutoff valve 29 has cut off the connection between the exhaust 
gas circulating pipe 30 and the connecting pipe 27. 
It is noted that the set timing of the geneva movement 43 prevents exhaust 
gases from entering the air-intake passage during the changeover of the 
operation mode, engine troubles caused by exhaust gases are eliminated. 
The set timing is also changeable and may be synchronized with the 
operation timing of the intake valve or the exhaust valve. 
It is noted that no time is necessary for the geneva movement to change 
over the engine operation mode, while an electronic control device needs 
time to process signals before the changeover of the engine operation 
mode. 
Since the driving force of the single DC motor 44 is divided to drive the 
intake-air-cutoff valves and the exhaust-gas-cutoff valve 29, only the 
starting time period of the DC motor 44 is necessary (the motor starting 
time is the main factor of the response time of the device). 
As a result, a highly responsive cylinder control device which is simple, 
inexpensive and free from torque-shocks or stagnation of engine operation 
is provided. 
FIG. 9 shows a second embodiment of the present invention. In the second 
embodiment, an intermittent gear mechanism 70 is employed in place of the 
geneva movement 43 of the first embodiment. The intermittent gear 
mechanism is composed of a driving gear 71 instead of the driving wheel of 
the first embodiment and driven gear 72 instead of the driven cam of the 
first embodiment. 
The driving gear 71 has a few teeth 73 on a portion of about a quarter of 
the periphery thereof and a circular portion 74 (pitch circle). The driven 
gear 72 has arc-shaped cam surfaces 75 formed on four peripheral portions 
coaxially with its shaft 47 at an equal interval (90.degree.) and teeth 76 
formed between the cam surfaces. The teeth 73 of the driving gear 71 and 
the teeth 76 of the driven gear 72 are put in engagement so that driven 
gear rotates the driven shaft 47 in the same manner as in the first 
embodiment, and the outer periphery of the driving gear 71 is put in 
slidable abutment with the arc-shaped cam surface 75 so that the driven 
gear is held at rest as in the first embodiment. 
When the driving gear 71 rotates between the rotation angle 0.degree. to 
the rotation angle 180.degree., the intake-air-cutoff valves and the 
exhaust-gas-cutoff valve operate in the same manner as those of the first 
embodiment. 
The driving gear 71 can be arranged to rotate to 360.degree. in a manner 
obvious to persons skilled in this field instead of the reciprocating 
between 0.degree. to 180.degree. as in the previous embodiments. 
A third embodiment is described next with reference to FIG. 10. 
A geneva movement 83 of this embodiment has a driving wheel 80 and a couple 
of driven cams 81 and 82. The driving wheel 80 has the same structure as 
the driving wheel 50 of the first embodiment, and the driven cams 81 and 
82 are also the same as the driven cam 57 of the first embodiment in 
structure. 
A driving shaft (not shown) connecting the exhaust-gas-cutoff valve 29 and 
the DC motor 44 is divided into two: a valve-side shaft which connects 
with the exhaust-gas-cutoff valve and a motor-side shaft. The motor-side 
shaft is disposed horizontally in parallel with a driven shaft and 
disposed vertically in parallel with the valve-side shaft. The driving 
wheel 80 is carried on the motor-side shaft and the driven cam 81 is 
carried on the driven shaft which connects with the intake-air-cutoff 
valves as described in the first embodiment. The other driven cam 82 is 
carried on the valve-side shaft. The driving wheel 80 rotates from angle 
0.degree. to angle 180.degree.. As the driving wheel 80 rotates from 
0.degree. to 90.degree., the roller 55 (the same as the first embodiment) 
engages with the groove 58 of the driven cam 81 so that the 
intake-air-cutoff valves 10a, 10b and 10c operate from the full-open state 
to the full-close state. As the driving wheel 80 further rotates from the 
angle 90.degree. to the angle 180.degree., the roller 55 engages the 
groove 58 of the other driven cam 82 so that a plate valve member 84 and a 
valve body 85 (shown in FIG. 10) of the exhaust-gas-cutoff valve 29 
operates from the full-close state to the full-open state. 
When the engine operation is changed over from the full-cylinder-operation 
mode to the partial-cylinder-operation mode, the exhaust-gas-cutoff valve 
29 is not opened until the intake-air-cutoff valve has been closed, and 
when the engine is changed over from the partial-cylinder operation to the 
full-cylinder operation, the air-intake-cut off valves 10a, 10b and 10c 
are not opened until the exhaust-gas-cutoff valve has been closed, as in 
the first embodiment. 
Other mechanisms instead of the above described geneva movement may be 
utilized to intermittently control the intake-air-cutoff valves and the 
exhaust-gas-cutoff valve as in the first embodiment. 
Although the embodiments of the present invention are described with a 
six-cylinder engine, the invention is also applicable to engines having 
different number of cylinders of other type (diesel engine, rotary engine 
or else). 
In the foregoing discussion of the present invention, the invention has 
been described with reference to specific embodiments thereof. It will, 
however, be evident that various modifications and changes may be made to 
the specific embodiments of the present invention without departing from 
the broader spirit and scope of the invention as set forth in the appended 
claims. Accordingly, the description of the present invention in this 
document is to be regarded in an illustrative, rather than a restrictive, 
sense.