Pneumatically operated device with valve and switch mechanisms

A pneumatically operated device responsive to a signal pressure applied thereto from a source of negative pressure for controlling the atmospheric air applied to a control device and for controlling an electric signal applied to an electric control circuit. The pneumatically operated device includes a diaphragm assembly assembled within a housing to subdivide the interior of the housing into first and second chambers respectively in open communication with the negative pressure source and the atmospheric air, and valve and switch mechanisms arranged within the housing to be operated in response to movement of the diaphragm assembly caused by the pressure difference between the first and second chambers.

BACKGROUND OF THE INVENTION 
The present invention relates to a pneumatically operated device, and more 
particularly to a pneumatically operated device in which valve and switch 
mechanisms are arranged to be operated in response to a pneumatic pressure 
applied thereto. 
In a conventional exhaust gas recirculation system for automotive vehicles, 
various pneumatically operated valve and switch mechanisms have been 
proposed heretofore. For example, such a pneumatically operated valve 
mechanism has been adapted to control exhaust gas recirculation in 
accordance with operating condition of a vehicle engine so as to effect 
reduction of the nitrogen oxide content NO.sub.x of exhaust emission, 
while such a pneumatically operated switch mechanism has been adapted to 
energize a solenoid valve in response to an input signal from an O.sub.2 
sensor in the exhaust system for controlling the ratio of air-fuel 
mixture. However, the above valve and switch mechanisms have been 
independently constructed and arranged in each control system. This 
results in high production cost of the respective mechanisms and 
complicated arrangement of them in a limited space. 
SUMMARY OF THE INVENTION 
It is, therefore, a primary object of the present invention to provide a 
pneumatically operated device in which valve and switch mechanisms are 
assembled in a simple and light weight construction to eliminate the 
disadvantages described above. 
Another object of the present invention is to provide a pneumatically 
operated device, having the above-mentioned characteristics, capable of 
adjusting the operation timing of the valve and switch mechanisms in a 
simple manner. 
According to the present invention briefly summarized, the above objects 
are accomplished by provision of a pneumatically operated device 
responsive to a signal pressure applied thereto from a source of pneumatic 
pressure for controlling the atmospheric air applied to a control device 
and for controlling an electric signal applied to an electric control 
circuit, which device comprises a housing provided with a first inlet port 
for connection to the pneumatic pressure source, a second inlet port in 
open communication with the atmospheric air, and an outlet port for 
connection to said control device; a diaphragm assembly assembled within 
the housing in a fluid tight manner to subdivide the interior of the 
housing into first and second chambers respectively in open communication 
with the first and second inlet ports, the diaphragm assembly being 
integrally provided with a movable member which is moved by the pressure 
difference between the first and second chambers; valve means including a 
valve seat arranged within the second chamber to permit the flow of 
atmospheric air from the second inlet port to the outlet port, and a valve 
member cooperating with the movable member to open and close the valve 
seat in response to the movement of the diaphragm assembly; and switch 
means arranged within the housing to be connected to the electric control 
circuit and including a pair of contacts one of which is arranged to be 
operated in response to the movement of the diaphragm assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to FIG. 1 of the drawings, a pneumatically operated device 
10 according to the present invention includes first and second housing 
sections 11 and 12 of synthetic resin which are secured to each other in a 
fluid tight manner. Between the housing sections 11 and 12 a diaphragm 
member 15 is interposed and clamped at its outer periphery to subdivide 
the interior of the housing assembly into an atmospheric chamber 16 and a 
negative pressure chamber 17. The diaphragm member 15 has a pair of 
movable members 13 and 14 of synthetic resin which are integrally secured 
to the central portion of diaphragm member 15. The first housing section 
11 is formed in its end wall 18 with an air passage 19 and provided in its 
recessed portions with a pair of annular air filters 20, 21 which are held 
in position by means of a cap member 22 of synthetic resin. The cap member 
22 is fixedly coupled over the opening end of housing section 11 and forms 
an air passage 23 which acts as an inlet port. With this arrangement, the 
atmospheric chamber 16 is in open communication with the atmospheric air 
through the air passage 19, filters 20, 21 and air passage 23. 
The end wall of housing section 11 is formed at its central portion with a 
stepped axial bore 24 in which a valve seat member 26 of synthetic resin 
is assembled via an O-ring seal member 25. The valve seat member 26 has a 
screw portion 27 which is adjustably threaded into the stepped portion of 
axial bore 24. The position of valve seat member 26 can be adjusted to a 
desired position by a tool which is engaged with radial recesses 28 formed 
on the outer end of valve seat member 26. A retainer plug 29 is fixedly 
engaged within the opening end of axial bore 24, and a compression coil 
spring 30 is interposed between the plug 29 and the valve seat member 26 
to eliminate an intervening space at the threaded portion 27 of valve seat 
member 26. The inner end of valve seat member 26 is formed as a valve seat 
34 and extends into a recessed portion 31 of second movable member 14 
through first movable member 13. 
The first movable member 13 is formed with an air passage 32 and slidably 
receives the inner end of valve seat member 26. The recessed portion 31 of 
second movable member 14 communicates with the atmospheric chamber 16 
through the air passage 32 of first movable member 13 and contains therein 
an elastic valve member 35 which is biased by a weak coil spring 33 to 
normally engage the valve seat 34 of member 26. Thus, the interior of 
recessed portion 31 of second movable member 14 is normally isolated from 
an axial air passage 36 in valve seat member 26, while the interior 37 of 
axial bore 24 is in open communication with the axial air passage 36 and 
an outlet port 38 radially formed in the end wall 18 of housing section 
11. Within the atmospheric chamber 16 a coil spring 41 is interposed 
between the first movable member and an annular retainer 40 to bias the 
diaphragm assembly rightwards. The retainer 40 is received by a screw 39 
which is adjustably threaded into the end wall 18 of housing section 11 to 
adjust the biasing force of spring 41. Within the negative pressure 
chamber 17 a coil spring 42 is interposed between the second movable 
member 14 and the inner wall of housing section 12 to bias the diaphragm 
assembly leftwards. The biasing force of coil spring 42 is determined in a 
value larger than that of coil spring 41 such that the initial position of 
the diaphragm assembly is balanced as shown in the figure. 
The housing section 12 is formed with an inlet port 43 which is arranged to 
connect an intake manifold of a vehicle engine. The negative pressure 
chamber 17 is supplied with a negative pressure through inlet port 43 in 
accordance with operating condition of the engine. When the negative 
pressure chamber 17 is supplied with a predetermined negative pressure, 
the diaphragm assembly moves rightwards against the biasing force of 
spring 42 and, in turn, the valve member 35 is separated from the valve 
seat 34 by engagement with an inner shoulder 44 of first movable member 13 
to communicate the atmospheric chamber 16 with the outlet port 38 through 
air passage 36. In such a manner as described above, the valve member 35 
cooperates with the valve seat 34 to provide a valve mechanism. 
In the valve mechanism, when the biasing force of coil spring 41 is 
adjusted by screw 39, the biasing force of coil spring 42 is adjusted in 
relation to the adjusted biasing force of coil spring 41. This serves to 
adjust the negative pressure value in chamber 17 necessary for conducting 
rightward movement of the diaphragm assembly. When the position of valve 
seat member 26 is adjusted to a desired position, as previously described, 
the distance between the inner shoulder 44 of first movable member 13 and 
the valve member 35 is appropriately adjusted. This serves to adjust the 
negative pressure value in chamber 17 necessary for opening the valve 
mechanism. In addition, the adjustment of the negative pressure value 
serves to adjust the operating pressure of a switch mechanism described 
hereinafter. The outlet port 38 is arranged to connect a negative pressure 
circuit of a control valve for controlling exhaust gas recirculation from 
the engine. 
The switch mechanism includes a reed switch 47 which is assembled within a 
tubular extension 46 integral with the end wall 45 of second housing 
section 12. The reed switch 47 comprises a pair of reed contacts 49 and 
50, the former being supported by an inner end of a conductor 48, and the 
latter being fixed to an insulation plate 52. The insulation plate 52 is 
secured to a projection 51 extending outwardly from the end wall 45 of 
housing section 12, and the conductor 48 is fixed at its outer end to the 
insulation plate 52. The reed contact 50 and conductor 48 are connected to 
a source of electricity by means of lead wires. In the figure, one of the 
lead wires is illustrated by the reference numeral 53. The lead wires are 
preferably attached at 55 to a cover member 54 fixed to the outer end of 
housing section 12, and the insulation plate 52 is fixed in place through 
a seal member 56 of silicone rubber. 
The second movable member 14 is integrally formed with a tubular extension 
57 which surrounds the tubular extension 46 of housing section 12. An 
annular permanent magnet 58 is fixed to the tubular extension 57 in such a 
manner that the reed contacts 49 and 50 are separated from each other due 
to the magnetic flux of magnet 58. When the magnet 58 is displaced in a 
predetermined distance due to rightward movement of the diaphragm 
assembly, the reed contacts 49 and 50 are engaged to each other to close 
the switch mechanism 47. In the actual use of the device 10, the switch 
mechanism is adapted to operate a solenoid valve for controlling the ratio 
of air-fuel mixture supplied into the engine. 
From the above description, it will be understood that adjustment of the 
biasing force of spring 42 is caused by adjustment of the biasing force of 
spring 41 and results in adjustment of the negative pressure value 
necessary for conducting the rightward movement of the diaphragm assembly. 
This means that the adjustment of the biasing force of spring 42 results 
in adjustment of the operation timing of reed switch 47. 
Hereinafter, the operation of the pneumatically operated device 10 will be 
described. When the negative pressure in chamber 17 applied from the 
intake manifold is below a predetermined value, the first movable member 
13 is engaged at its left end with an inner shoulder of valve seat member 
26 due to the biasing force of spring 42 to normally close the valve 
mechanism and to normally open the switch mechanism, as shown in the 
figure. Under the inoperative condition, the valve member 35 abuts against 
the valve seat 34 by the resilient force of spring 33 to interrupt the 
communication between the atmospheric chamber 16 and the outlet port 38. 
As a result, a negative pressure is applied to the above-mentioned control 
valve to conduct the exhaust gas recirculation, while the solenoid valve 
is maintained inoperative to prevent decrease of the air-fuel mixture 
ratio. 
When the negative pressure in chamber 17 exceeds the biasing force of 
spring 42, the diaphragm assembly displaces rightwards, and then the inner 
shoulder 44 of first movable member 13 abuts against the valve member 35 
to separate from the valve seat 34 against the weak biasing force of 
spring 33 so as to connect the atmospheric chamber 16 to the outlet port 
38. As a result, the control valve is deactivated in response to the 
atmospheric air applied from the outlet port 38 to disconnect the exhaust 
gas recirculation. Simultaneously, the reed contacts 49 and 50 are engaged 
to each other in response to the rightward movement of magnet 58 to close 
the reed switch 47 so as to decrease the air-fuel mixture ratio in a 
conventional manner. 
In FIG. 2, there is illustrated a modified pneumatically operated device 60 
in which the same or similar component parts and portions as those in the 
above embodiment are indicated by the same or similar reference numerals 
as those in FIG. 1. In the pneumatically operated device 60, the coil 
spring 41 of FIG. 1 is eliminated, and the coil spring 42 of FIG. 1 is 
supported by a stationary plate 61 fixed to the inner wall of a modified 
housing section 12a. A tubular rod 63 is fixed at its left end to a 
modified movable member 14a, which corresponds with the movable member 14 
of FIG. 1, and has an axial air passage 62 which communicates into a 
recessed portion 31a of the movable member 14a through a filter element 66 
and an orifice plate 67. The filter element 66 is provided to prevent the 
entrance of moisture into the tubular rod 63. A second diaphragm member 64 
is interposed and clamped at its outer periphery between the stationary 
plate 61 and the inner wall of housing section 12a, which diaphragm member 
64 is fixed at its inner periphery to an intermediate portion of tubular 
rod 63 to form an atmospheric chamber 65 isolated from the negative 
pressure chamber 17. 
The right end of tubular rod 63 opposes to a movable piston 68 which is 
slidably disposed within a stepped bore of housing section 12a. The piston 
68 is received at its right end by a spring loaded retainer 69 and is 
engaged at its left end with an inner shoulder of the bore. Thus, the 
right end of tubular rod 63 is normally separated from the piston 68 to 
communicate the atmospheric chamber 65 with the recessed portion 31 of the 
movable member 14a. A fixed contact 71 is secured at 72 to the housing 
section 12a, and a movable contact 73 is also secured at 74 to the housing 
section 12a. Both the contacts 71 and 73 are connected to a source of 
electricity by way of lead wires. In the figure, one of the lead wires is 
indicated by the reference numeral 75. The lead wire 75 extends outwardly 
through a seal member 81 and is preferably attached at 55 to the bottom of 
housing section 12a. The movable contact 73 normally engages the fixed 
contact 71 by its self-reliency to provide a normally closed switch 
mechanism, which movable contact 73 is also engaged at 76 with the movable 
piston 68. 
When the diaphragm assembly including members 13a and 14a is displaced 
rightwards, as previously described, the tubular rod 63 abuts against the 
piston 68 to move it rightwards, and then the movable contact 73 is 
separated from the fixed contact 71 in response to the rightward movement 
of piston 68 to open the switch mechanism. A compression coil spring 70 is 
engaged at its one end with the retainer 69 and at its other end with a 
retainer 77 which is received by a screw 80. The screw 80 is adjustably 
threaded into a cap member 78 of synthetic resin which is fixed to the 
outer end of housing section 12a, and a seal member 79 of silicone rubber 
closes the screw 80 at its adjusted position. 
Having now fully set forth both structure and operation of preferred 
embodiments of the concept underlying the present invention, various other 
embodiments as well as certain variations and modifications of the 
embodiments herein shown and described will obviously occur to those 
skilled in the art upon becoming familiar with said underlying concept. It 
is to be understood, therefore, that within the scope of the appended 
claims, the invention may be practiced otherwise than as specifically set 
forth herein.