Two speed mechanical supercharger

A mechanical supercharger includes a housing, first, second and third shafts rotatably supported on the housing, respectively, a first timing gear disposed on the first shaft, a second timing gear disposed on the second shaft and engaged with the first shaft timing gear, a first rotor disposed on the first shaft, a second rotor disposed on the second shaft and engaged with the first rotor, a first pulley disposed on one end of the first shaft, an electromagnetic clutch interposed between the first shaft and the first pulley and being selectively intermittent a transmission of driving force between the first shaft and the first pulley, a reduction gear disposed on one end of the third shaft through an one-way clutch and engaged with the second timing gear, a second pulley disposed on the other end of the third shaft and a driving force transmission means for transmitting driving force of engine to the first and second pulleies so that the first and second pulleies are simultaneously rotated in the same direction. Thereby, it is possible to reduce the number of the additional parts for changing the supercharging quantity in response to the condition of the engine and it is possible to prevent the unnecessary increasing of the rotating mass of the rotation groups which are rotated for supercharging.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a mechanical supercharger, and more 
particularly to a mechanical supercharger for supercharging an engine for 
automobiles and so on. 
2. Description of the Prior Art 
A conventional mechanical supercharger is disclosed, for example, in 
Japanese utility model application laid-open publication No. 
2(1990)-34728. As shown in FIG. 8, this conventional mechanical 
supercharger 80 includes four shafts 82, 83, 89, 90 rotatably supported on 
a housing 81, rotors 84, 85 disposed on the about center portion of the 
shafts 82, 83, respectively and timing gears 86, 87 disposed on one end of 
the shafts 82, 83 respectively so that both shafts 82, 83 are 
synchronously rotated. In this mechanical supercharger 80, a variable 
speed mechanism 88 is disposed between the shafts 89, 83. Thereby, the 
rotation of the shaft 89 is increased and is transmitted to the shaft 83. 
Similarly, a variable speed mechanism 91 is disposed between the shafts 
90, 83. Thereby, the rotation of the shaft 90 is increased and is 
transmitted to the shaft 83. Now, the variable ratio of the variable speed 
mechanism 88 differs from the variable speed ratio of the variable speed 
mechanism 91. Furthermore, in this mechanical supercharger 80, pulleys 94, 
95 are installed on end portions of the shafts 89, 90 through 
electromagnetic clutches 92, 93, respectively. These pulleys 94, 95 are 
driven by a driving source such as an engine (not shown) and so on through 
a belt (not shown) and the operational condition of the electromagnetic 
clutches 92, 93 are controlled by a control device 96. 
In this conventional mechanical supercharger 80, either of the 
electromagnetic clutches 92, 93 is selectively connected by the control 
device 96 and the rotors 84, 85 are driven in accordance with the variable 
speed ratio of either of the variable speed mechanisms 88, 91. Thereby, 
the supercharging pressure of the mechanical supercharger 80 is changed. 
In the above conventional mechanical supercharger 80, however, since two 
expensive electromagnetic clutches are employed and furthermore two 
variable speed mechanisms are employed, the cost and the weight of the 
mechanical supercharger increase remarkably. 
Furthermore, when either of the electromagnetic clutches 92, 93 is 
connected, the shafts 82, 83, 89, 90 and all of rotational members (each 
gear and so on) which are disposed on the shafts 82, 83, 89, 90 are 
driven. When the electromagnetic clutch 92 is connected, for example, it 
is not necessary to rotate a rotation group of the shaft 90. Nevertheless, 
the rotation group of the shaft 90 is rotated. Accordingly, the rotating 
mass of the rotation groups which are rotated for supercharging increases 
and therefore the response of the mechanical supercharger deteriorates. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide an improved 
mechanical supercharger which overcomes the above drawbacks. 
It is another object of the present invention to provide an improved 
mechanical supercharger which includes a simple variable speed mechanism 
and which can decrease the rotating mass of the rotation groups which are 
rotated for supercharging. 
In order to achieve these objects, there is provided a mechanical 
supercharger which includes a housing, first, second and third shafts 
rotatably supported on the housing, respectively, a first timing gear 
disposed on the first shaft, a second timing gear disposed on the second 
shaft and engaged with the first timing gear, a first rotor disposed on 
the first shaft, a second rotor disposed on the second shaft and engaged 
with the first rotor, a first pulley disposed on one end of the first 
shaft, an electromagnetic clutch interposed between the first shaft and 
the first pulley and selectively transmitting driving force between the 
first shaft and the first pulley, a reduction gear disposed on one end of 
the third shaft through an one-way clutch and engaged with the second 
timing gear, a second pulley disposed on the other end of the third shaft 
and a driving force transmission means for transmitting driving force of 
the engine to the first and second pulleys so that the first and second 
pulleys are simultaneously rotated in the same direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A mechanical supercharger constituted in accordance with embodiments of the 
present invention will be described with reference to the attached 
drawings. 
FIG. 1 to FIG. 3 show a first embodiment of the present invention. 
Referring to FIG. 1, a crankpulley 12 of engine 11 is connected with a 
first pulley 14 and a second pulley 15 of a mechanical supercharger 10 
through a belt 13 so that the mechanical supercharger 10 is driven by the 
crankpulley 12 of the engine 11 through the belt 13. Thereby, the first 
and second pulleies 14, 15 are simultaneously rotated by the engine 11 
through the belt 13 in the same direction and therefore the belt 13 
corresponds to a driving force transmission means of the present 
invention. 
Referring to FIG. 2 and FIG. 3, first, second and third shafts 22, 23, 24 
are rotatably supported on a housing 21 of the mechanical supercharger 10 
though bearings. A first timing gear 25 and a first rotor 27 are fixed on 
the first shaft 22. On the other hand, a second timing gear 26 and a 
second rotor 28 which are engaged with the first timing gear 25 and the 
first rotor 27 respectively are fixed on the second shaft 23. In the 
housing 21, a volume chamber 29 which is communicated with an inlet port 
and an outlet port (not shown) is formed therein and the first rotor 27 
and the second rotor 28 are rotated in the volume chamber 29. 
The first pulley 14 is diposed on one end of the first shaft 22 through a 
electromagnetic clutch 30. The electromagnetic clutch 30 is interposed 
between the first shaft 22 and the first pulley 14 and is controlled by a 
control device (not shown) so as to intermittently transmit driving force 
between the first shaft 22 and the first pulley 14 selectively. A 
reduction gear 31 which is engaged with the second timing gear 26 is 
disposed on one end of the third shaft 24 through an one-way clutch 32. 
The second pulley 15 is fixed on the other end of the third shaft 24. The 
one-way clutch 32 is interposed between the third shaft 24 and the second 
pulley 15 and functions so as not to transmit the rotation of the 
reduction gear 31 to the third shaft 24 when the reduction gear 31 is 
driven by the second timing gear 26. Now, the rotation of the third shaft 
24 is transmitted to the reduction gear 31 when the reduction gear 31 is 
not driven by the second timing gear 26. 
The above-described first embodiment of the mechanical supercharger 
operates as follows. When the engine 11 is started, the first pulley 14 
and the second pulley 15 are simultaneously driven by the crankpulley 12 
through the belt 13 in the same direction. In case of large required 
supercharging quantity of the engine 11, the electromagnetic clutch 30 is 
connected (ON-condition) by the control device (not shown). In this case, 
the driving force of the belt 13 which is connected with the first pulley 
14 is transmitted to the first shaft 22 through the electromagnetic clutch 
30 and then is transmitted to the second shaft 23 through the first timing 
gear 25 and the second timing gear 26. Accordingly, the first rotor 27 and 
the second rotor 28 are synchronously rotated in the volume chamber 29. 
Thereby, air is discharged from the inlet port (not shown) to the outlet 
port through the volume chamber 29 and the engine 11 is supercharged. In 
this situation, the rotation of the first pulley 14 is transmitted to the 
first rotor 27 and the second rotor 28 without increasing or decreasing 
the rotational speed of the first pulley 14 and the ratio between the 
rotational speeds of the first pulley 14 and the rotors 27, 28 is 1:1. 
Similarly, the reduction gear 31 is rotated by the second timing gear 26 
and the rotational speed of the reduction gear 31 is increased in 
accordance with the reduction ratio between the reduction gear 31 and the 
second timing gear 26. On the other hand, the second pulley 15 and the 
third shaft 24 are driven by the belt 13. The rotational speed of the 
third shaft 24 is as same as the first pulley 14 and is lower than that of 
the reduction gear 31. In this situation, since the rotation of the 
reduction gear 31 is not transmitted to the third shaft 24 by the function 
of the one-way clutch 32 and therefore the third shaft 24 synchronized 
with regard to the reduction gear 31, however, there is no problem in the 
operation of the mechanical supercharger 10. 
On the other hand, in case of small required supercharging quantity of the 
engine 11, the electromagnetic clutch 30 is disconnected (OFF-condition) 
by the control device (not shown). Therefore, the driving force of the 
belt 13 which is connected with the first pulley 14 is not transmitted to 
the first shaft 22. In this case, the driving force of the belt 13 which 
is connected with the second pulley 15 is transmitted to the second timing 
gear 26 through the third shaft 24, one-way clutch 32 and the reduction 
gear 31. In this situation, the rotational speed of the second timing gear 
26 is reduced in accordance with the reduction ratio between the reduction 
gear 31 and the second timing gear 26 and the reduced rotation of the 
second timing gear 26 is transmitted to the second shaft 23. Then, the 
driving force of the belt 13 is transmitted to the first shaft 22 through 
the first timing gear 25 and the second timing gear 26. Accordingly, the 
first rotor 27 and the second rotor 28 are synchronously rotated in the 
volume chamber 29. Thereby, air is discharged from the inlet port (not 
shown) to the outlet port through the volume chamber 29 and the engine 11 
is supercharged. In this situation, the supercharging quantity is smaller 
than that in the situation which the electromagnetic clutch 30 is 
connected (ON-condition) and each of the supercharging characteristics in 
the situations which the electromagnetic clutch 30 is connected 
(ON-condition) and is disconnected (OFF-condition) is shown in FIG. 7. 
Now, the condition of the electromagnetic clutch 30 is controlled by the 
control device (not shown) in response to the condition of the engine 11 
such as the load of the engine 11 and so on. 
FIG. 4 to FIG. 6 show a second embodiment of the present invention. In the 
FIG. 4 to FIG. 6, the same parts as compared with FIG. 1 to FIG. 3 use the 
same numeral utilized the FIG. 1 to FIG. 3. Referring to FIG. 4 and FIG. 
5, the first pulley 14 is connected with the second pulley 15 though a 
connecting member 41 such as a belt, a chain and so on so that the first 
and second pulleies 14, 15 are simultaneously rotated in the same 
direction. At the second pulley 15, a third pulley 40 is fixed thereto so 
as to be rotated with the second pulley 15 in one body. The third pulley 
40 is connected with the crankpulley 12 of the engine 11 through the belt 
13 so that the mechanical supercharger 50 is driven by the crankpulley 12 
of the engine 11 through the belt 13. Thereby, the first and second 
pulleies 14, 15 are simultaneously rotated by the engine 11 through belt 
13, the third pulley 40 and the connecting member 41 in the same direction 
and therefore the belt 13, the third pulley 40 and the connecting member 
41 correspond to a driving force transmission means of the present 
invention. Now, since the other structures are as same as the first 
embodiment shown by FIG. 1 to FIG. 3, further description is omitted. 
According to this embodiment, when the engine 11 is started, the third 
pulley 40 is driven by the crankpulley 12 through the belt 13. Then, the 
driving force of the belt 13 which is transmitted to the third pulley 40 
is transmitted to the first pulley 14 through the second pulley 15 and the 
connecting member 41. In case of large required supercharging quantity of 
the engine 11, the electromagnetic clutch 30 is connected (ON-condition) 
by the control device (not shown). In this case, the above described 
driving force of the belt 13 which is connected with the first pulley 14 
is transmitted to the first shaft 22 through the electromagnetic clutch 30 
and then is transmitted to the second shaft 23 through the first timing 
gear 25 and the second timing gear 26. Accordingly, the first rotor 27 and 
the second rotor 28 are synchronously rotated in the volume chamber 29. 
Thereby, air is discharged from the inlet port (not shown) to the outlet 
port through the volume chamber 29 and the engine 11 is supercharged. In 
this situation, the rotation of the third pulley 40 as an inlet pulley is 
transmitted to the first rotor 27 and the second rotor 28 without 
increasing or decreasing the rotational speed of the third pulley 40 and 
the ratio between the rotational speeds of the third pulley 40 and the 
rotors 27, 28 is 1:1. 
Similarly, the reduction gear 31 is rotated by the second timing gear 26 
and the rotational speed of the reduction gear 31 is increased in 
accordance with the reduction ratio between the reduction gear 31 and the 
second timing gear 26. On the other hand, the third pulley 40, the second 
pulley 15 and the third shaft 24 are driven by the belt 13. The rotational 
speed of the third shaft 24 is as same as the first pulley 14 and is lower 
than that of the reduction gear 31. In this situation, since the rotation 
of the reduction gear 31 is not transmitted to the third shaft 24 by the 
function of the one-way clutch 32 and therefore the third shaft 24 is not 
synchronized with regard to the reduction gear 31, however, there is no 
problem in the operation of the mechanical supercharger 50. 
On the other hand, in case of small required supercharging quantity of the 
engine 11, the electromagnetic clutch 30 is disconnected (OFF-condition) 
by the control device (not shown). Therefore, the driving force of the 
belt 13 which is connected with the first pulley 14 is not transmitted to 
the first shaft 22. In this case, the driving force of the belt 13 which 
is connected with the third pulley 40 and the second pulley 15 is 
transmitted to the second timing gear 26 through the third shaft 24, 
one-way clutch 32 and the reduction gear 31. In this situation, the 
rotational speed of the second timing gear 26 is reduced in accordance 
with the reduction ratio between the reduction gear 31 and the second 
timing gear 26 and the reduced rotation of the second timing gear 26 is 
transmitted to the second shaft 23. Then, the driving force of the belt 13 
is transmitted to the first shaft 22 through the first timing gear 25 and 
the second timing gear 26. Accordingly, the first rotor 27 and the second 
rotor 28 are synchronously rotated in the volume chamber 29. Thereby, air 
is discharged from the inlet port (not shown) to the outlet port through 
the volume chamber 29 and the engine 11 is supercharged. Accordingly, the 
supercharging quantity is changed in response to the condition of the 
electromagnetic clutch 30 and each of the supercharging characteristics in 
the situations in which the electromagnetic clutch 30 is connected 
(ON-condition) and is disconnected (OFF-condition) is shown in FIG. 7. 
Now, the condition of the electromagnetic clutch 30 is controlled by the 
control device (not shown) in response to the condition of the engine 11 
such as the load of the engine 11 and so on. 
According to the present invention, as mentioned above, it is possible to 
reduce the number of the additional parts (the elctromagnetic clutch, the 
reduction gear and so on) for changing the supercharging quantity in 
response to the condition of the engine such as the load of the engine and 
so on and therefore the structure of the mechanical supercharger is 
simplified. Thereby, it is possible to reduce the cost of the mechanical 
supercharger. Furthermore, it is possible to improve the reliability of 
the mechanical supercharger. 
Furthermore, since it is possible to separate the third shaft from the 
first and second shafts by the function of the one-way clutch selectively, 
it is possible to prevent the unnecessary increasing of the rotating mass 
of the rotation groups which are rotated for supercharging and therefore 
it is possible to improve the response of the mechanical supercharger. 
The principles, preferred embodiments, and modes of operation of the 
present invention have been described in the foregoing description. The 
invention which is intended to be protected herein should not, however, be 
construed as limited to the particular forms disclosed, as these are to be 
regarded as illustrative rather than restrictive. Variations and changes 
may be made by those skilled in the art without departing from the spirit 
of the present invention. Accordingly, the foregoing detailed description 
should be considered exemplary in nature and not limited to the scope and 
spirit of the invention as set forth in the appended claims.