Suction and discharge valve mechanism for fluid displacement apparatus

A piston-type fluid displacement apparatus includes a housing enclosing a crank chamber, a suction chamber, and a discharge chamber. Discharge conduits are formed at a top dead center position of the piston. A control device includes valve members having suction apertures and discharge apertures for opening and closing the suction conduits and the discharge conduits. The control device further includes a driving mechanism joined to the valve members for driving the valve members to gradually open each of the suction conduits during the suction stage of the piston and to gradually close each of the discharge conduits during the discharge stage of the piston. Thus, the piston-type fluid displacement apparatus may prevent the valve assembly from stopping or sticking at the sliding contact surfaces of the suction and discharge holes to allow the pistons to reciprocate smoothly within each cylinder without reducing the compression efficiency. Further, the piston-type fluid displacement apparatus also improves the sealing performance between the valve assembly and the sliding contact surfaces of the suction and discharge holes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a suction and discharge valve mechanism 
for a fluid displacement apparatus. More particularly, it relates to a 
configuration of a suction and discharge valve mechanism for a 
reciprocating piston-type refrigerant compressor used in an automotive air 
conditioning system. 
2. Description of the Related Art 
Piston-type compressors, such as swash plate-type compressors and 
wobble-type compressors, are known in the art. For example, U.S. Pat. No. 
4,776,259 to Takai describes an air conditioning device used for a vehicle 
employing a multi-cylinder, piston-type compressor with reciprocating 
pistons and a suction and discharge valve mechanism. 
In the following description, the right side of each figure is referred to 
as a rear or rearward end, and the left side of each figure is referred to 
as a front or forward end. With reference to FIGS. 1 and 2, a wobble 
plate-type compressor is shown comprising a compressor housing 11 having a 
cylinder block 11b fixed at a rear end of compressor housing 11, and a 
front end plate 10 disposed on a front end opening of compressor housing 
11. A cylinder head 18, defining a discharge chamber 20 and a suction 
chamber 19, is mounted on the rear end opening of compressor housing 11 
behind a valve plate 18a. 
A discharge valve assembly is mounted on a rear end surface of valve plate 
18a. Valve plate 1 8a has a discharge hole 20a extending therethrough to 
allow communication between the compression chamber and discharge chamber 
20. The discharge valve assembly comprises a discharge valve 22 and a 
valve retainer 21, which is secured to a rear end surface of valve plate 
18a by bolt 23. 
Referring to FIG. 2, valve retainer 21 limits the bending movement of 
discharge reed valve 22 in the direction in which the refrigerant gas 
exits a cylindrical bore 17 and enters discharge chamber 20 through 
discharge hole 20a. Discharge reed valve 22 has a modulus of elasticity 
which keeps discharge hole 20a closed until the pressure in cylindrical 
bore 17 reaches a predetermined value. 
Compressor housing 11 defines a crank chamber 13 that is adjacent to 
cylinder block 11b. Cylinder block 11b is provided with a plurality of 
equi-angularly spaced cylindrical bores 17. A drive shaft 12 is rotatably 
supported at its rear end by cylinder block 11b through a bearing 12b, and 
at its front end by a front end plate 10 through a bearing 12a. A cam 
rotor 14 is fixedly mounted on drive shaft 12 by a pin (not shown) and 
rotatably supported relative to a rear end surface of front end plate 10 
through a thrust bearing 12c. A wobble plate 15 is disposed on a reduced 
diameter portion 15b of cam rotor 14 that extends axially outward from the 
inclined cam surface of cam rotor 14. A thrust bearing 14a is interposed 
between wobble plate 15 and the inclined cam surface of cam rotor 14. 
Wobble plate 15 is prevented from axial movement on reduced diameter 
portion 15b by restraining ring 15c. A reciprocating piston 16 is received 
in each of cylindrical bores 17. Each piston 16 is connected to wobble 
plate 15 through a piston rod 16a. A restraining means 15a comprises a 
slot formed in the peripheral surface of wobble plate 15 and slide plate 
11 a mounted in the bottom portion of crank chamber 13 and extending 
axially thereof. 
Discharge reed valve 22 strikes a rear end surface of valve plate 18a when 
it closes. This striking generates vibration and noise during the 
operation of the compressor. Vibration, caused by discharge reed valve 22 
striking a rear end surface of valve plate 18a, is readily transmitted to 
compressor housing 11. 
One proposed solution to overcome the above-mentioned disadvantages is 
described in Japanese Unexamined Utility Model Publication No. H4-119,370. 
That application describes a compressor wherein a valve mechanism includes 
circular plate members connected to the drive shaft. The rotation of the 
drive shaft and the circular plate members opens and closes the suction 
conduits and the discharge conduits. 
Another proposed solution to overcome the above-mentioned disadvantages is 
described in Japanese Unexamined Patent Publication No. H5-126,040. The 
application discloses a compressor wherein a valve mechanism comprises a 
rotary valve or a piston, or a rod, in lieu of circular plate members. The 
valve mechanism opens and closes the suction conduit and the discharge 
conduit, respectively. 
However, in the configuration of the valve mechanism comprising circular 
plate members and a rotary valve, the sliding contact surfaces do not move 
smoothly with respect to each other, and the sealing performance between 
the sliding contact surfaces is decreased. As a result, an manufacturer is 
required to carefully control the clearance of the sliding contact 
surfaces in assembling the compressor. Thus, this configuration is 
difficult to manufacture and expensive to assemble. 
Further, in the configuration of the compressor comprising a piston or a 
rod, the valve mechanism acts to either fully open or fully close a 
suction conduit and a discharge conduit during a suction stage or a 
discharge stage of the compressor. The valve mechanism does not permit 
opening a fraction of an area of the suction conduit and the discharge 
conduit, i.e., a suction conduit is fully opened and a discharge conduits 
is fully closed when the compressor moves from the suction stage to the 
discharge stage. Thus, the suction conduit and discharge conduit are 
opened fully and closed fully without considering the reciprocating speed 
of the piston. 
Generally, a piston within a cylinder reciprocates with speed reaching zero 
at the bottom dead center and top dead center positions, and with maximum 
speed at a position halfway between bottom dead center and top dead 
center. Thus, it is difficult for a piston to reciprocate smoothly within 
a cylinder because the replacement fluid sucked into and discharged from 
the cylinder has an inertia force. This results in a decrease in the 
compression efficiency. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a piston-type fluid 
displacement apparatus which prevents the valve assembly from sticking or 
stopping at the sliding contact surfaces of the suction and discharge 
holes. 
It is another object of the present invention to provide a piston-type 
fluid displacement apparatus which increases or improves, or both, the 
sealing performance between the valve assembly and the sliding contact 
surfaces of the suction and discharge holes. 
It is a further object of the present invention to provide a piston-type 
fluid displacement apparatus wherein a piston reciprocates smoothly within 
a cylinder. 
According to the present invention, a piston-type fluid displacement 
apparatus comprises a housing enclosing a crank chamber, a suction 
chamber, and a discharge chamber. A plurality of cylinders are formed in 
the housing. A plurality of pistons, each of which is slidably disposed 
within one of the cylinders, reciprocate within the cylinders. A plurality 
of suction conduits are formed at the top dead center positions of the 
pistons. A plurality of discharge conduits also are formed at the top dead 
center positions of the pistons. A driving device is coupled to the 
pistons for driving the pistons, such that the rotary motion of the 
driving device is converted into a reciprocating motion of the pistons 
within the cylinders. A control device comprises a plurality of valve 
members having suction apertures and discharge apertures for opening and 
closing the suction conduits and the discharge conduits. The control 
device further comprises a driving mechanism joined to the valve members 
for driving each valve member to gradually open its respective suction 
conduit during the suction stage of its respective piston, and to 
gradually close its respective discharge conduit during the discharge 
stage of its respective piston.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The embodiments of the present invention are illustrated in FIGS. 3-8. In 
FIGS. 3-8, the same reference numerals are used to denote elements which 
correspond to elements depicted in FIGS. 1 and 2. A detailed explanation 
of these similar elements and their characteristics is provided above and, 
therefore, is here omitted. 
Referring to FIG. 3, a suction chamber 119 and a discharge chamber 120, 
defined by a cylinder head 118, are formed radially around drive shaft 12. 
A cylinder block 11 is provided with a cam chamber 30 at its center. Drive 
shaft 12 extends through a radial bearing 12b to cam chamber 30. A cam 
mechanism 32 is secured by a bolt 38 to a rear end of drive shaft 12 
within cam chamber 30. Thus, cam mechanism 32 rotates with drive shaft 12 
about a longitudinal axis of drive shaft 12. Cam mechanism 32 comprises a 
circular plate having a radial cam groove 32a. Cam groove 32a lies in a 
zigzag line axially, i.e., a part of cam groove 32a is axially offset at 
an interval angle of 180 degrees. 
The compressor comprises a plurality of cylindrical bores 17 and a 
plurality of pistons 16, which are positioned around the axis of drive 
shaft 12 at 90 degree angular intervals. A plate member 34 is disposed 
between cam chamber 30 and suction chamber 119 in order to separate cam 
chamber 30 from suction chamber 119. Plate member 34 comprises a plurality 
of suction holes 34a corresponding to suction conduits 119a, a cylindrical 
recessed portion 34b formed at the center of plate member 34, and a 
plurality of cylindrical apertures 34c extending radially from cylindrical 
recessed portion 34b and each corresponding to a cylindrical bore 17. Each 
cylindrical aperture 34c is formed to be perpendicular to its 
corresponding suction hole 34a. A plurality of fluid valve members 36 are 
disposed in a plurality of cylindrical apertures 34c to cover a plurality 
of suction holes 34a. Fluid valve members 36 are in contact with the 
radial outer circumference of plate member 34. Each fluid valve member 36 
has a cylindrical shape and comprises an opening 36a for placing suction 
conduit 119a and suction hole 34a in communication. Each of fluid valve 
members 36 also has a center axis perpendicular to the longitudinal axis 
of drive shaft 12 and is rotatably disposed in its respective cylindrical 
aperture 34c. Further, each of fluid valve members 36 comprises a drive 
pin member 36b, which is positioned to be eccentric with respect to the 
center axis of the fluid valve member 36. Thus, cam mechanism 32 causes 
fluid valve member 36 to counter-rotate around its axis. 
In operation, drive shaft 12 of the above-mentioned compressor is driven by 
any suitable driving source, such as an automobile engine. Cam rotor 14 
rotates together with drive shaft 12, such that wobble plate 15 is held 
against rotation with cam rotor 14 by a rotation restraining means (not 
shown). Nutation of wobble plate 15 causes the reciprocating action of 
each respective piston 16. Therefore, the evacuation and compression of a 
refrigerant gas is repeatedly performed in each cylinder 17. 
FIG. 4 depicts a schematic view of one full cycle, wherein cam mechanism 32 
and fluid valve member 36 operate from a suction stage to a discharge 
stage of piston 16. The top dead center and bottom dead center positions 
of piston 16 correspond to 0 degrees (360 degrees) and 180 degrees, 
respectively. The position of cam groove 32a of cam mechanism 32 also is 
depicted from the suction stage to the discharge stage. 
During the suction stage (0 degrees-180 degrees), cam mechanism 32 causes 
fluid valve member 36 to counter-rotate, such that fluid valve member 36 
begins to open suction conduit 119a at the top dead center position. 
Suction conduit 119a is opened fully at a piston position halfway between 
top dead center and bottom dead center. Suction conduit 119a again is 
closed at the bottom dead center position. Thus, cam mechanism 32 causes 
fluid valve member 36 to open gradually during the suction stage. 
In contrast, during the discharge stage (180 degrees-360 degrees), cam 
mechanism 32 causes fluid valve member 36 to close suction conduit 119a 
throughout. Consequently, cam mechanism 32 substantially regulates how 
much of an area of suction conduit 119a is opened relative to the position 
of piston 16. 
In this arrangement, fluid valve member 36 may move slidably on suction 
conduit 119a with a lower slide speed or shorter slide distance in 
comparison with the known art, because cam mechanism 32 permits fluid 
valve member 36 to rotate itself Therefore, cam mechanism 32 prevents the 
valve mechanism from stopping or sticking on sliding contact surfaces, 
while simultaneously improving sealing performance between the sliding 
contact surfaces. 
Thus, piston 16 can reciprocate smoothly within cylindrical bore 17 because 
cam mechanism 32 causes fluid valve member 36 to open gradually during the 
suction stage, allowing fluid to be drawn smoothly into and discharged 
from the cylinder with little or no inertia force itself As a result, this 
arrangement increases or improves, or both, the compression efficiency in 
comparison with the known art. 
A discharge valve member may be provided in lieu of fluid valve member 36, 
and a suction valve may be provided in lieu of discharge valve 122. In 
this arrangement, cam mechanism 32 causes the suction valve member to 
close the suction conduit throughout the suction stage. Cam mechanism 32 
also causes the discharge valve member to open gradually the discharge 
conduit during the discharge stage to permit fluid valve member 36 to 
rotate. Alternatively, the compressor may be provided with not only fluid 
valve member 36, but also with a discharge valve member, in lieu of 
discharge valve 122 and retainer 121. Cam mechanism 32 may cause both the 
discharge valve member and the suction valve mechanism to rotate. 
A second embodiment of the present invention, applicable to a compressor 
having an arrangement different from the compressor of the first 
embodiment, is described in conjunction with FIGS. 5 and 6. 
Referring to FIGS. 5 and 6, the compressor of the second embodiment 
comprises a plurality of fluid valve members 136 which are circular-shaped 
plates and are disposed between valve plate 118a and a plate member 134. 
Plate member 134 is disposed between cam chamber 30 and suction chamber 
119 in order to separate cam chamber 30 from suction chamber 119. Plate 
member 134 comprises a plurality of suction holes 134a corresponding to a 
number of suction conduit 119a, a cylindrical recessed portion 134b formed 
at the center of plate member 134, and a plurality of rectangular grooves 
134c radially extending from cylindrical recessed portion 134b and each 
corresponding to a cylindrical bore 17. 
Each rectangular groove 134c is perpendicular to its corresponding suction 
hole 134a. A plurality of fluid valve members 136 are disposed slidably in 
a plurality of rectangular grooves 134c in order to cover a plurality of 
suction holes 134a. Fluid valve members 136 comprise an openings 136a for 
placing suction conduit 119a and suction hole 134a of plate member 134, in 
communication. Each fluid valve member 136 has a longitudinal axis 
perpendicular to the axis of drive shaft 12. Further, each of fluid valve 
members 136 includes a drive pin portion 136b extending perpendicularly 
from an end of the rear surface of the valve members. Cam mechanism 132 is 
secured to the rear axial end of drive shaft 12 by bolt 38 within cam 
chamber 30. Cam mechanism 132 comprises a substantially circular plate 
having a cam groove 132a formed thereon. am groove 132a may be an 
egg-shape groove. Each drive pin portion 136b of each fluid valve member 
136 is disposed in cam groove 132a of cam mechanism 132, and slides in 
rectangular grooves 134c of plate member 134 relative its position in cam 
groove 132a. Thus, cam mechanism 132 causes suction valve member 136 to 
undergo reciprocating action in rectangular grooves 134c of plate member 
134. 
Referring to FIG. 6, a line which crosses the center of drive shaft 12 
horizontally is defined as border line. The lower side and the upper side 
of the line represent a suction stage and a discharge stage, respectively. 
When drive shaft 12 and cam mechanism 132 rotate in a counterclockwise 
direction, as shown by arrow A, the cylinder which is positioned at 3 
o'clock corresponds to a top dead center position of a piston. The 
cylinder positioned at 9 o'clock corresponds to a bottom dead center 
position of a piston. 
During the suction stage of piston 16 (0 degrees-180 degrees), cam 
mechanism 132 causes fluid valve member 136 to move radially outward, in 
the direction shown by arrow B, such that fluid valve member 136 begins to 
open suction conduit 119a at the top dead center position. Suction conduit 
119a is opened fully at a position halfway between top dead center and 
bottom dead center. Thereafter, cam mechanism 132 causes fluid valve 
member 136 to move radially inward, in the direction shown by arrow B, 
such that the suction conduit is closed at the bottom dead center position 
of piston 16. Thus, cam mechanism 132 causes fluid valve member 136 to 
open gradually during the suction stage of piston 16. 
In contrast, cam mechanism 132 causes fluid valve member 136 to close 
suction conduit 119a throughout the discharge stage of piston 16 (180 
degrees-360 degrees). Consequently, cam mechanism 132 substantially 
regulates how much of the area of suction conduit 119a is opened relative 
to the position of piston 16. 
A discharge valve member may be provided in lieu of fluid valve member 136, 
and a suction valve may be provided in lieu of discharge valve 121a. In 
this arrangement, cam mechanism 132 causes the suction valve member to 
close the suction conduit throughout the suction stage of piston 16. Cam 
mechanism 132 also causes the discharge valve member gradually to open a 
discharge conduit in the discharge stage of piston 16 in order to permit 
fluid valve member 136 to slide within rectangular groove 134c of plate 
member 134. 
The advantages obtained by the first preferred embodiment are also 
substantially realized by the second preferred embodiment. 
A third embodiment of the present invention applicable to a compressor 
having an arrangement different from the compressor of the first 
embodiment is described in conjunction with FIGS. 7 and 8. 
Referring to FIG. 7, the compressor of the third preferred embodiment 
includes a plurality of fluid valve members 236. Fluid valve members 236 
are elliptically-shaped plates and are disposed between valve plate 118a 
and a plate member 234. Plate member 234 is disposed between cam chamber 
30 and suction chamber 119 in order to separate cam chamber 30 from 
suction chamber 119. Plate member 234 includes a plurality of suction 
holes 234a therein corresponding to suction conduits 119a, a cylindrical 
recessed portion 234b formed at the center of plate member 234, and a 
plurality of discharge holes 234c formed radially outside of suction holes 
234a. Discharge holes 234c correspond to a plurality of discharge conduits 
120a. A plurality of rectangular grooves 234d are formed on an axial end 
of plate member 234 and are perpendicular to suction holes 234a and 
discharge holes 234c. 
Fluid valve members 236 are slidably disposed in rectangular grooves 234d 
in order to cover suction holes 234a and discharge holes 234c. Each fluid 
valve member 236 includes an opening 236a formed therein for placing 
suction conduits 119a and suction holes 234a in communication. Discharge 
openings 236a also place discharge conduits 120a and discharge holes 234c 
in communication. 
Further, each fluid valve member 236 includes a drive pin portion 236b 
extending axially from an edge of the rear surface. Cam mechanism 232 is 
secured by bolt 38 to a rear axial end of drive shaft 12 within cam 
chamber 30. Cam mechanism 232 comprises a substantially circular plate 
having a cam groove 232a. Cam groove 232a may be an egg-shape groove 
formed on a axial front end surface of cam mechanism 232. Each drive pin 
portion 236b of each fluid valve member 236 is disposed in cam groove 232a 
of cam mechanism 232 in order to slide in rectangular grooves 234d of 
plate member 234 relative to the rotation of cam groove 232a. 
Thus, cam mechanism 232 causes fluid valve member 236 to undergo 
reciprocating action in rectangular grooves 234d of plate member 234. 
Referring to FIG. 8, a line which crosses the center of drive shaft 12 
horizontally defines a border line. The lower side and the upper side of 
the line represent a suction stage and a discharge stage of piston 16, 
respectively. When drive shaft 12 and cam mechanism 232 rotate in a 
counterclockwise direction, as shown by arrow A, the cylinder positioned 
at 3 o'clock corresponds to the top dead center position of a piston. The 
cylinder positioned at 9 o'clock corresponds to the bottom dead center 
position of a piston. 
During the suction stage of piston 16 (0 degrees-180 degrees), cam 
mechanism 232 causes fluid valve member 236 to move radially outward, in 
the direction shown by arrow B, such that fluid valve member 236 begins to 
open suction conduit 119a at the top dead center position of piston 16. 
Suction conduit 119a is opened fully at a position halfway between top 
dead center and bottom dead center. Thereafter, cam mechanism 232 causes 
fluid valve member 236 to move radially inward, in the direction shown by 
arrow B, in order to fully close suction conduit 119a at the bottom dead 
center position of piston 16. Thus, cam mechanism 232 causes fluid valve 
member 236 to close discharge conduit 120a throughout the suction stage. 
On the other hand, during the discharge stage of piston 16 (180 degrees-360 
degrees), cam mechanism 232 causes fluid valve member 236 to move 
gradually inward, in the direction shown by arrow B, such that fluid valve 
member 236 begins to open discharge conduit 119a at the bottom dead center 
position of piston 16. Discharge conduit 119a is fully opened at a 
position halfway between top dead center and bottom dead center of piston 
16. Thereafter, cam mechanism 232 causes fluid valve member 236 to move 
radially outward, in the direction shown by arrow B, in order to close 
fully at the top dead center position of piston 16. Thus, cam mechanism 
232 causes fluid valve member 236 to close suction conduit 119a throughout 
the discharge stage. 
Consequently, cam mechanism 232 allows fluid valve member 236 to under 
reciprocating action, such that fluid valve member 236 opens suction 
conduit 119a gradually in the suction stage of piston 16 and closes 
discharge conduit 120a gradually in the discharge stage of piston 16. 
Substantially the same advantages as those in the first and second 
preferred embodiments are also realized by the third preferred embodiment. 
Moreover, in the third preferred embodiment, cam mechanism 232 causes fluid 
valve member 236 to gradually open suction conduit 119a during the suction 
stage of piston 16, in addition to closing discharge conduit 120a 
throughout during the discharge stage of piston 16. Thus, a fluid can be 
smoothly suctioned from suction chamber 119 and discharged to discharge 
chamber 120 without having inertia force. Therefore, cam mechanism 132 
suitably regulates the open area of suction conduit 119a relative to the 
position of piston 16, and piston 16 can reciprocate smoothly within 
cylindrical bore 17. As a result, this arrangement may increase or 
improve, or both, the compression efficiency. 
Although the present invention has been described in connection with 
preferred embodiments, the invention is not limited thereto. Specifically, 
this invention may employ a link mechanism as a control device for the 
fluid valve member. Further, this invention may be realized by combining 
an inspection device within the driving device, to inspect the position of 
the piston in the suction stage and the discharge stage and regulate the 
opening area of the suction valve and the discharge valve. 
In addition, while the preferred embodiments illustrate the invention in a 
swash plate-type compressor, this invention is not restricted to swash or 
wobble plate-type refrigerant compressors, but may be employed in other 
piston-type compressors or piston-type fluid displacement apparatus. 
Accordingly, the embodiments and features disclosed herein are provided by 
way of example only. It will be understood by those of ordinary skill in 
the art that variations and modifications may be made within the scope of 
this invention as defined by the following claims.