Variable capacity compressor

A compressor includes a plurality of pistons, a shaft and a wobble plate rotatably and swingably connected with said shaft so that the pistons are reciprocated in accordance with the wobbling movement of the wobble plate. The capacity of the compressor is varied in accordance with the inclining angle of the wobble plate. The actual capacity of the compressor is detected by the magnetic sensor. The compressor has a through member at the lower most portion of the pressure chamber provided in the housing and the slider is slidably connected with the through member. The slider also rotatably connected with the wobble plate so that the wobbling movement of the wobble plate makes the slider reciprocate along with the through member. Such movement of the slider is detected by the magnetic sensor.

The present invention relates to a variable volume compressor which is used 
as a compressor for compressing coolant for an automotive cooler, for 
example. 
BACKGROUND OF THE INVENTION 
A wobble type compressor having a wobble plate and a plurality of pistons 
slidably provided within cylinders and functionally connected to the 
wobble plate is used as the compressor for automotive air conditioners. It 
has been known for the wobble type compressor that the inclining angle of 
the wobble plate is varied in order to change the reciprocating stroke of 
the piston (U.S. Pat. No. 3,861,829). 
Though such a type of variable volume wobble compressor can vary the volume 
in accordance with the inclining angle of the wobble plate, the inclining 
angle of the wobble plate is hard to controll. Since the inclining angle 
of the wobble plate is controlled in accordance with the pressure within a 
housing, and since it is difficult to change the pressure within the 
housing, conventional type of the variable volume wobble type compressor 
is difficult to control accurately. Namely, there must exist some time lag 
between the timing when the control pressure is introduced into the 
housing and the timing when the wobble plate inclines the desired 
inclining angle, and such a time lag cannot be estimated accurately. 
Therefore, a positioning sensor which can sense the position of the wobble 
plate is desired. 
Since the conventional type of positioning sensor using a magnet can sense 
only a small distance (3 mm for example), the conventional type sensor 
cannot be used for sensing the position of the wobble plate. Another type 
of positioning sensor using a photosensor is also hard to use with the 
compressor, because the photosensor must be provided within the housing 
and because the operation of the photosensor is hindered by the lubricant 
oil or any other foreign object within the housing. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a variable volume 
compressor having a positioning sensor which detects the position of an 
wobble plate. 
In order to attain the above object, the present invention employs a 
through member within a cover housing, a wobble plate and an inclining 
plate are provided within the cover housing. A slider is connected with 
the through member in such a manner that the slider can slide along with 
the through member, the slider is rotatably connected with the wobble 
plate. Since the wobble plate is wobbled within the cover housing in 
accordance with the rotation of the inclining plate, the slider can 
reciprocate along with the through member in accordance with the movement 
of the wobble plate. A magnet is connected with the slider in such a 
manner that the direction of the flux of the magnet is identical with the 
longitudinal axis of the through member. A plurality of magnetic sensors 
are provided in such a manner that each of the magnetic sensors faces the 
slider when the slider moves along with the through member. 
So that the movement of the magnet can be sensed by the magnetic sensor. 
Since a plurality of magnetic sensors are arranged in a line, the 
reciprocating stroke of the slider can be calculated by distinguishing the 
magnetic sensor which senses the magnet. Since the compressor of the 
present invention is sensed the position of the wobble plate by magnetic 
sensor, the reciprocating stroke of the wobble plate can be sensed even 
though the wobble plate is located within the lubricant oil.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENT 
The first embodiment of the present invention is described hereinafer. The 
numeral 111 in FIG. 1 shows a cylinder housing made of aluminum alloy and, 
a plurality of cylinders 106 are formed within the cylinder housing 111. A 
piston is slidably provided within each of cylinders 106. A rear housing 
123 is fixed to the first end portion of the cylinder housing 111 via a 
valve plate 114. A suction chamber 107 and a discharge chamber 111 are 
formed within the rear housing. A suction valve is provided on the valve 
plate 114 so that the coolant within the suction chamber 107 can be sucked 
toward the cylinder 106 through the suction valve. A discharge valve 109 
is also provided on the valve plate 114, and the discharge valve 109 and a 
valve cover 110 are fixed on the valve plate 114 by a bolt 140. Since the 
discharge valve 109 can open and close a discharge port formed in the 
valve plate 104, the coolant compressed within the housing 106 is 
discharged toward the discharge chamber 108 through the discharge port. 
A cover housing 125 is fixed to another end portion of the cylinder housing 
via an 0-ring 141. Rotating mechanisms such as a rotating plate 101 and a 
wobble plate 103 are provided within the cover housing. A shaft 115 is 
rotatably supported in the cover housing 125 by journals 116 and 117. A 
rotating member 118 is fixed to the shaft 115 so that the rotating member 
118 and the shaft 115 rotate in synchranism. The thrust force added to the 
rotating member 118 is supported by a thrust bearing 119. The rotating 
plate 101 is connected to the rotating member 118 via a pin 1011. 
Since the rotating plate 101 is inclined, the rotating plate 101 wobbles 
when the rotation of the shaft 115 is transmitted thereto. The wobble 
plate 103 is connected on the rotating plate 101 via a bearing 143 so that 
the wobble plate 103 cannot rotate even when the rotating plate 101 
rotates. Thereby the wobble plate 103 wobbles within a pressure chamber 
213 without any rotation when the rotation of the shaft 115, and is 
transmitted; and the to the wobble plate 111 via the rotating plate 101. 
The wobble movement is transmitted to the piston 105 via a rod 104. Since 
the rod 104 is rotatably connected with the wobble plate 103 via a ball 
shaped portion formed at one end of the rod 104, and since the rod 104 is 
also rotatably connected with the piston 105 via a ball shaped portion 
formed at another end of the rod 104, the wobble movement of the wobble 
plate 103 makes the piston 105 reciprocate. 
Since the rotating plate 101 is connected to the rotating member 118 via 
the pin 111, angle of inclination of the rotating plate 101 can be varied. 
The reciprocating stroke of the piston 105 is varied in accordance with 
the inclining angle of the rotating plate. Namely, the reciprocating 
movement becomes larger when the inclining angle of the wobble plate is 
large. The reciprocating movement of the piston, on the other hand, 
becomes small when the inclining angle of the rotating plate 101 becomes 
small. Accordingly the reciprocating stroke can be controlled in 
accordance with the angle of inclination of the rotating plate. 
A shaft seal 145 which prevents the leakage of the coolant within the 
pressure chamber 213 along with the shaft 115 is provided within the cover 
housing 125. A cylindrical hub portion 147 on which an electromagnetic 
clutch (not shown) is mounted is formed at the center portion of the cover 
housing 125. The rotating movement of the automotive engine is transmitted 
toward the shaft 115 via the electro magnetic clutch. 
The inclining angle of the wobble plate 103 is varied in accordance with 
the pressure within the pressure chamber 213. The high pressure is added 
toward the back portion of the piston 105 when the pressure within the 
pressure chamber 213 becomes high so that such high pressure makes the 
reciprocating stroke of the piston 105 short. The pressure added on the 
back side of the piston 105 becomes small when the pressure within the 
pressure chamber 213 reduces so that such small pressure causes the 
reciprocating stroke of the piston 105 to become large. Accordingly, the 
reciprocating movement of the piston 105 and the inclining angle of the 
wobble plate 103 can be controlled when the pressure within the pressure 
chamber 213 is controlled. 
The pressure within the pressure chamber 213 is controlled via a control 
valve 301. The control valve 301 is provided in the rear housing 113, and 
the control valve 301 receives discharge pressure within the discharge 
chamber 108 and the suction pressure within the suction chamber. The 
control valve 301 modulates the output pressure which is introduced into 
the pressure chamber 213. An electra magnetic valve 303 provided within 
the control valve 301 is controlled to set the proportion of the timing 
during which the electro magnetic valve 303 opens a high pressure path 304 
which is connected to the discharge chamber 108 and the timing when the 
electro magnetic 303 closes the high pressure chamber 304 so that the 
output pressure which is introduced into the pressure chamber 213 via a 
output path is modulated (as shown in FIG. 9). The output path 305 is 
formed within the rear housing 113 and the cylinder housing 111. 
The cover housing 125, the cylinder housing 111 and the rear housing 113 
are connected each other via a plurality of through bolts 202. A slider 
203 is slidably connected on the through bolt 202 which locates lower most 
portion of the housing. The slider 203 is also rotatably connected with 
the wobble plate 103 as shown in FIGS. 2, 3 and 10. 
FIG. 10 shows a through hole 2030 through which the through bolt 202 is 
inserted is formed at the central portion of the slider 203. A connecting 
pin 2031 which is inserted into a connecting hole 2033 formed in a shoe 
2032 is formed at a side portion of the slider 203 so that the slider 203 
is rotatably connected with the shoe 2032. The shoe 2032 is slidably held 
within a sliding groove 2034 formed in the lower most portion of the 
wobble plate 103. The relative movement between the wobble plate 103 and 
the through bolt 202 can be compensated by the reciprocating movement of 
the shoe 2032 and the rotation of the slider 203. Since the slider 203 
locates the lower most portion of the pressure chamber 213, the lubricant 
oil filled in the pressure chamber 213 lubricates the gap between the 
slider 203 and the through bolt 202, the gap between the slider 203 and 
the shoe 2032 and the gap between the shoe 2032 and the sliding groove 
2034. A magnet 204 is fixed on the lower most surface of the slider 203. 
The direction of the flux between N pole to S pole is identical with the 
longitudinal axis of the through bolt 202; and thereby the direction of 
the flux 2041 of the magnet 204 is identical with the moving direction of 
the slider 203. 
A magnetic sensor has a base plate 236 fixed on a sensing housing 207 and a 
plurality of hole IC 246 provided on the base plate 236. The sensor 
housing 207 is fixed to the cover housing 125 via a packing 208 and a 
washer by a bolt 214. A slight gap g is formed between the hole IC 246 and 
the top end of the magnet 204. The gap g is controlled to be between a 
predetermined width of 0.5 mm-1.5 mm with the gap of 0.8 mm being 
preferred. A magnetic housing 250 is fixed to the slider 203 by a mataric 
adhesive, and the magnet 204 is fixed to the magnet housing 250 by 
caulking. 
As shown in FIG. 4, the hole IC 206 is rectangular, and the width of the 
hole IC is about 4-4.5 mm and the thickness thereof is about 2 mm. The 
hole IC 246 is so provided that a detecting surface 2461 thereof is 
perpendicular with the flux 2041. Thereby, a plurality of hole ICS 246 
make a line in such a manner that the detecting surface 2461 of an one 
hole IC faces to the detecting surface 2461 of adjacent hole IC 246. 
The hole IC 246 of the magnetic sensor 206 is explained hereinafter. As 
shown in FIG. 4, hole IC 246 has three terminals 1, 2 and 3, the first 
terminal 1 is connected to the automotive battery via a converter so that 
a voltage (5 Vt) is supplied thereto, the third terminal 3 is grounded to 
the automotive body, and output voltage (5 Vt) is output to the second 
terminal 2 when a predetermined amount of flux 2041 is passed through the 
hole IC 246. 
The structure of the hole IC 246 is described in FIG. 5. Hole IC element 
301 which outputs the output voltage is provided within the hole IC 246. 
The output voltage is supplied to a trigger 304 after the output voltage 
is amplified by an amplifier 303. The output voltage is transferred to 0 
or 1 by the trigger 304. Namely, the trigger 304 generates a "1" pulse 
when the amount of flux is less than the predetermined value (500 Gauss) 
and the trigger 304 generates a pulse when the amount of the flux becomes 
higher than the predetermined value. The output signal generated by the 
trigger 304 is transferred to the second terminal 2 via an output stage 
305. A voltage regulator 306 is connected between the trigger 304 and the 
output, stage 505. 
FIG. 6 shows a characteristic curve of the hole IC. The output voltage 
becomes 0 when the density of the flux becomes higher than the 
predetermined value 500 (Gauss). Pulse signals generated from the hole IC 
246 is maintained a predetermined time by a one shot IC. The predetermined 
time is calculated using the rotating speed of the compressor as a 
parameter. When the compressor rotates 720 RPM, which is the idling 
condition of the automotive engine, the predetermined time is calculated 
as being 90 mSec by the following equation: 720/60 rpm the second=12 Hz 
720/60 rpm/Sec=12H.sub.z. Since the slider 203 reciprocates within the 
pressure chamber 213, the output voltage should be maintained while the 
period after the slider passed through the hole IC and before the slider 
returns to the hole IC 246. 
The output signal is supplied to an encoder 403 so that the signals from 
the one shot IC 400 is exchanged to a 0 or 1 signal. The changed signal is 
then supplied to an adder 404 in order to add the signal from one encoder 
to the signal from another encoder 403. Numeral 405 shows a digital to 
analog converter and numeral 406 shows an amplifier. The signal from the 
amplifier 406 has the characteristic shown in FIG. 8. Namely the circuit 
400 generates the signal in accordance with the signal from the hole IC. 
Since the signal from the hole IC 246 designates the reciprocating stroke 
of the slider 203, and since the reciprocating length of the slider 
designates the inclining angle of the wobble plate 103, the output signal 
from the circuit 400 designates the capacity of the compressor. 
An output signal from the circuit 400 is introduced into the electric 
control unit 211. The signal from air conditioning electric control unit 
210 is also introduced into the electric control unit 211 so that the 
preferred volume of the compressor is calculated within the electric 
control unit 211. When the signal from air conditioning circuit 210 
indicates a shortage of the cooling capability, the signal is supplied to 
the control valve 301 in order to maximize the volume of the compressor. 
The difference between the preferred volume of the compressor calculated 
by the electric control unit and the actual volume of the compressor 
detected by the circuit 400 is fed back to the electric control unit in 
order to modulate the capacity of the compressor. 
As shown in FIG. 9, not only the positioning sensor, but also the other 
sensors sensing the condition of the air conditioner such as pressure 
sensor 601 which detects the discharge pressure form the compressor, a 
temperature sensor which detects the temperature of the atmosphere within 
the passenger's compartment and an accelerating sensor 603 which detects 
the accelerating operation of the automotive engine are provided, and the 
electric signal from these sensors are supplied to the air conditioning 
electric control unit 210. The air conditioning electric control unit 210 
controls the duty ratio in cooperation with the electric signals. Since 
the actual compressor capacity is detected by the pressure sensor 206 and 
such signal is fed back to the electric control unit 210, the electric 
control unit 210 can control the capacity of the compressor accurately and 
quickly. 
As described above, since the compressor of the present invention employs 
the through member within the pressure chamber, and since the slider is 
slidably connected with the through member, the slider and the through 
member can be lubricated by the lubricant oil within the pressure chamber 
so that the slider can slide smoothly. Since the magnet is provided at the 
end portion of the slider in such a manner that the direction of the flux 
is identical with the direction of the reciprocating movement of the 
slider, and since the flux is perpendicular to the sensing surface of the 
magnetic sensors, a plurality of magnetic sensor can be provided along 
with the direction of the reciprocating movement of the slider so that the 
position of the slider can be detected by the magnetic sensor.