CA2065831C

CA2065831C - Slant plate type compressor with variable displacement mechanism and method of controlling the capacity thereof

Info

Publication number: CA2065831C
Application number: CA002065831A
Authority: CA
Inventors: Kiyoshi Terauchi
Original assignee: Sanden Corp
Current assignee: Sanden Corp
Priority date: 1991-04-10
Filing date: 1992-04-10
Publication date: 1997-12-09
Anticipated expiration: 2012-04-10
Also published as: EP0508823B1; JPH04311685A; DE69205480D1; AU1477792A; CN1029023C; EP0508823A1; KR920020078A; DE69205480T2; CA2065831A1; CN1067096A; KR100216388B1; AU650960B2

Abstract

In a slant plate type compressor with a variable displacement mechanism, the stroke of the piston changes in response to the change of the slant angle. The relative distance of the piston from the valve plate when in top dead center position varies within a certain range in response to the change of the stroke of the piston.
A detecting device disposes adjacent the cylinder detects the top dead center position of the piston in the compression space. The piston's stroke length is related to the detected top dead center position, and once the piston's stroke length is known, this information can be used to determine whether capacity control is required.

Description

SLANT PLATE TYPE COMPRESSOR WITH
VARIABLE DISPLACEMEN~ MECHANISM AND
METHOD OF CO~OLLING THE CAPACITY THEREOF
TECHNICAL FIELD
The present invention relates to a co~ ssor with a variable ~ pl~ement mech~n;~.." and more particularly, to a slant plate type colllpl~ i,Sol with a variable displnnemPnt Inech~ni~n~ in which the ol~elatillg capacity of the colllpl~sor isdelellllined by sensing the top dead center position of the piston.
BACKGROUND OF THE INV~iN IION
A conventional slant plate type cc,lllpressor with a variable displacement mecl~ni~m as used in an automotive air conditioning system controls the di.~rl~cement of the colllp~ssor in response to changes the air conditioning load.
The ~ p~ mPnt of the colll~ of at a given opeldLing capacity is related to the angle of the wobble plate or stroke length of the pistons. Thus, if the wobble plate angle is known, it can be colllpalt;d to pledt;~e....;n~d ideal wobble plate angles and adjusted acco~ ly by selectively opening and closing control valves between the operating chambers in the Colll~l~ ssor. Ullrollullalely, prior art mP~h~ni~m~ for d~Pt~Pctin~ colll~ssor disp1~nenlPnt tend to be costly due to their complex construction, so, unless a particular application dictates the eYr~Pn(1iture, such mecl-~n;~ are generally not employed.
For eA~ le, a conventional device for dt;l~;l;ue the displacement of a colllpl~ssor is disclosed in U.S. Patent 4,737,079 to Kur~,~a..a et al. The '079~lr~ling device inelu~les a non-contact type position sensor molmtP,d on the outer p~,;ph~.,.l surface of the colll~ ,sor housing for sensing a detPcted object reciprocating on the outer l)eliph~al surface of the wobble plate. The sensor is an elecl~...~gnPtic indu~;lion type sensor mounted on the outer peliphc~al surface of the housing which genelales a signal pulse each time the detected object passes thereby. This signal pulse is indicative of rut~lional speed of the COIll~ltiSSOl'S
drive shaft and angular orientation of the wobble plate.
The rotational speed of the '079 drive shaft is c~lcul~~Ad by coullling the number of signal pulses gPne.,.led by the sensor within a p~ in~d period of time. The angular orientation of the wobble plate, on the other hand, is c~lcnl~ted by taking a ratio of the time that the detectecl object is on one side of the sensor to the time that the detected object is on the other side of the sensor. Once this ratio and the col~onding wobble plate angle is obtained ~ ;rlul.l, the control unit has stored therein prede~....;llP~l ideal wobble plate angularity tables which dt;lel..line whether capacity control, e.g., opening the co...---~ ;cqtion path between the crank chqmber and the suction chamber, is in order.
As seen above, the angle of the wobble plate is cq1rulqtp~d indirectly in the '079 col-lplcssor~ In other words, the ratio of the time the detected object is on one side of the sensor to the time that the detected object is on the opposite side of the sensor eventually in~ S the slant angle of the woWle plate, which in turnin~ e5 the current o~latiollal capacity of the colllplt;ssol. From this capacitydt;l~,.lllh~àtion, the control unit calculates whether the opelaling capacity of the colllp~ssor should be altered, i.e., sending signals to open the control valves.Therefore, the '079 colll~ sor control unit digitally converts time values during which the wobble plate remains on respective sides of the sensor to arrive at the final d~ n of the wobble plate angle. These cqlrnlqtions are an indirect in~lir~tion of the wobble plate angle and the con~ ol's opelaling capacity. Moreover, the eluiylll~ l nr~ei,--.y for such cq.1rul-qtions tends to incl~dse the cost of the colll~ ,ssor. Con~ .e~nly, the applications in which the '079 wobble plate angle c-q1ru1 ~inn circuit is employed might be limited.
SUMMARY OF THE INVENIION
It is an object of the preferred embo-l;..~r~ to provide a slant plate type colllyl~ sor with a variable displ~cemrnt .~erl~n~ l which includes a device fordirectly drl~;l;..~ the operational disp~eemP,nt of the colllyl~;ssor.
It is another object of the pl~;r~,l~d embo~ to provide a slant plate type colll~l~,ssor with a variable ~ p~ empnt ...~h~ ... which inrlucl~Ps an ul~ y~nsive and simple capacity del~l;ng device.
A slant plate type colllpl~ssor with a variable displ~ç...~1 mPrhqnicm accol~ling to the preferred embodiments colnl)lises a collly~ssor housing enclosing a crank chamber, a suction rhqmber, and a .lisch~e chqmber. The housing also inrhldes a cylinder block with a plurality of ~;ylindel~ formed therein. A piston is slidably fitted with each of the ~;ylindel~ and reciprocates between a bottom dead center position and a top dead center position. A drive mech~n;~, which is coupled to the pistons, r~i~cales the pistons within the cylinders. The drive mel~.hqni.~m incl~ s a drive shaft rotatably ~ polled in the housing~ Coupling means drivingly couples the pistons with the drive shaft and converts rotary motion of the drive shaft into reciprocating motion of the pistons. The coul)lh~g meansin~ s a slant plate having a surface disposed at a slant angle relative to a plane perpen(lir -1qr to the drive shaft. The slant angle h~;lt;ascs or dec;leascs in ;~ponse to changes in pl~,s~ ; in the crank chamber, which in turn alters the stroke of the pistom Con.~eq~-~.ntly, the capacity of the coll.pressor changes~
The co~ .sol's capacity is dc;lt;llllined by sensing, with an analog sensor, the top dead center position of the pistom For e,~alllple, when ~elaling under maximum capacity, i~e~, large slant angle, the top dead center position of the piston is relatively close to the valve plate~ Conversely, when ope~ g under ...;.~;....~.. capacity, i.e., small slant angle, the top dead center position of the piston is relatively farther from the valve plate than when o~eld~ g under l,.~xi.. ~.. capacity. A sensor is disposed a~ljarent the cylinder for detecting the top dead center position of the piston in the co.l.~ ,ssion space. The sensed top dead center position indicates the capacity under which the co.--l,~ssor is l;ullcll~ly u~lalillg. In other words, when the top dead center position ch~nges~ so does the capacity of the cûll.~ ssor. Upon obt~ining the top dead center position, the p1~cem~nt of the co--.~ssor can be easily dele~ ~l, and the ~ ~e",~ ~1 ulrollll~tioll can be utilized for controlling or Illoniloling the air condiliol~ing system.
Further objects, features and other aspects of the illie~t;on will be understood from the following ~l~sc.;l~l;ol- of the pl~,fe~l~d elllb~)h~e-~t~i while l~;r~ ing to the ~tt~~h~l dlawillgs.
BRIEF D~SCRIPIION OF TH~ DR~WINGS
FIG. 1 is â cross-sectinnq1 view of a slant plate type colll~ssor with a variable di~pl~~ement mf-b7~i~m according to a first pleft;~ d embodirnent in which the inclined angle of the slant plate is at a mq~cimllm FIG. 2 is a cross-sectional view of a slant plate type colnpf~i~or with a variable rli~pk~re~cnt mechanism accGl-lh~g to the first ~I~;rel~d embodiment ;nwhich the inclined angle of the slant plate is at a ...ini...~....~
FIG~ 3 is a partial cross-section~l view of a slant plate type cc,~ ressor with a variable displ~ çmP.nt mech~ni.~m in acco~lce with a second ~l~re~ d embodiment.
FIG. 4 is a partial cross-sectional view of a slant plate type co.-lplt;ssor with a variable dis~l~ce~ mechanis.ll in acconlance with a third ~ rell~d embodiment.
FIG. S ;s a graph of the relationship between the piston's stroke and the top dead center position of the piston.
DETAILED DESCRIPTION OF l~lE PREFERRED EMBODIMENTS
Referring to FIG. 1, wobble plate type colllpl~s~r 1 in-~.hlchP.s ~ront end plate 2, cylinder casing 3, valve plate 4, and cylinder head 5. Front end plate 2 is f~ed on one end of cylinder casing 3 by unshow~ll secu~ing bolts. Axial hole 21, which is formed through the center of front end plate 2, receives drive shaft 7. Radial bearing 8 is dis~os~ in axial hole 21 to rotatably support drive shaft7. Cylinder casing 3 surrounds cylinder block 31 and crank chamber 32.
Cylinder block 31 has a plura1ity of e~luian~,.llarly spaced cylinders 33 formedtherein.
Cam rotor 10 is f~ed on drive shaft 7 by pin 103. Thrust needle bearing 11 is disposed between the inner surface of front end plate 2 and the ~ ?~ent axial end surface of cam rotor 10. Arm portion 101 of cam rotor 10 extends in the direction of cylinder block 31. Hole 102 is formed on arm portion 101.
Cylin-lri~1 member 12, having flange portion 121 ~Al~nding ll.~ l., is disposed around drive shaft 7 and is rotatably ~po~tecl on drive shffl 7 through spherical element 13 slidably fitted on drive shaffl 7. Second arm portion 122 is formed on the outer surface of flange portion 121 of ~;y1i~ 1 member 12 and faces arm portion 101 of cam rotor 10. Elongated hole 123, formed in ann portion 122, is aligned with hole 102. Pin 14 is inserted through hole 102, and is slidably movable within elongated hole 123.
Ring-shaped wobble plate 15 is mounted on the outer surface of cylin~

member 12 through radial needle bearing 16. Thrust needle bearing 17 is disposedin a gap between fl~u~ge portion 121 and wobble plate 15. The inner end of driveshaft 7 is rotatably supported through radial bearing 18 in the central bore of ~;ylinde~ block 31. Sliding shaft 151 is ~ hed on the outerpelilJhelal portion of wobble plate 15 and projects toward the bottom surface of cylinder casing 3. Theend of sliding shaft 151 is slidably disposed in groove 321 to prevent the rotation of wobble plate 15. One end of piston rod 19 is connected to wobbIe plate 15, while the other end thereof is com~ ed to piston 20 which is slidably disposed in cylinder 33.
A suction port (not shown) and discha~ port 42 are formed in valve plate 4. An unshu~n suction reed valve and an ull~howll discharge reed valve are dis~osed on opposite sides of valve plate 4. Gaskets are provided on opposing sides of valve plate 4 to seal the respective mating surfaces between valve plate 4 and cylinde~ head S and valve plate 4 and cylinder casing 3. PaTtition wall 51 extends axially from the inner surface of c;ylil~d~ head S and divides the interior of cylindc~r head S into suction çh~ her 52 and discha~, çh~...l)er 53. Suction chamber 52 is col-nP";Ied to the external fluid circuit through fluid inlet port 60 formed in cylinder head 5. Dischalg~ chamber 53 is com~led to the external fluid circuit through fluid outlet port 61 formed in ~;yli~lder head 5.
Cylin-lril~1 bore 62, which is formed in ~;ylinder block 31, has bellows 63 di~osed therein. On one side, bore 62 co.. ~ with suction chomber 52 through aperlure 64 formed through valve plate 4, while on the other side, bore 62 co.~ -ir~tes with crank 1 ~ ~her 32 through pasjdge~.ay 65 formed through cylinder block 31. Aperture 64 is normally closed by needle element 631 di~sed on one end of bellows 63. The cG..,...~iC~ion between crank ch~ 32 and suction challl~r 52 is controlled by the movement of bellows 63.
In operation, l~lalional motion applied to drive shaft 7 is l~,.n.c...illed to cam rotor 10. The rotational motion of cam rotor 10 is then converted to nuldtional motion of wobble plate 15. Sliding shaft 151, coml~led to wobble plate 15 and disposed in groove 321, pl~ t~ wobble plate 15 from rotating. The ~---~;o~
motion of wobble plate 15 is converted to the reciprocating motion of pistons 20 in cylhldel~ 33~ Acco~Lngly, ~ ;g~,lation fluid is sucked through inlet port 60 to suction chamber 52 and flows into cylh~der 33 through the unshown suction port~ Next, ref.;gel.llion fluid is col-lp~ssed in cylinder 33 and is lischa~ed into discharge cha-l~r 53 through dischal~c port 42~ The COIll~ ,SSed refrigeration fluid then flows into the external fluid circuit through outlet port 61~
P~v~ ily position sensor 70 is a non-contact type position dt;l~ device and has a capacity for clele~;l;,-g the piston's top dead center in the range of about 1 mm~ P~uAinlily position sensor 70 is disposed on the cylinder side of valve plate 4 to face the top surface of piston 20. Distance QX between the inner surface ofvalve plate 4 and the top surface of piston 20 is 0.3 mm when the inclined angleof flange portion 121 is at a ..~ ;.n----. as shown in FIG. 1, and distance ~x is 1.3 mm when the inclined angle of flange portion 121 is at a ...;.-i...~.... as shown in FIG. 2. Therefore, p~Aul~ily position sensor 70 is chosen to sense a top dead center position ranging from 0.3-1.3 mm, and outputs an analog signal COll~ ~on.ling to the sensed top dead center position.
With lcr~lcnce to FIG. 3, there is shown a partial cross-sectional view of a co---plc~i,sor in ac~rdance with a second pl~rel.~d embodiment~ Detected object 80 is, for example, a pf.lllla~ t magnet disposed on the top end surface of piston 20~ Hall gen~lalor 81 is disposed on the cylinder side of valve plate 4 to face ~1et~cted object 80. Hall gçn~r~tor 81 generates an output signal col-e~onding to distance QX between itself and detect~cl object 80~ Mstance ~x is proportional to the capacity at which the colllpl-,~sor is ~iull~i~ltly o~ldt.ng. Accoldingly, the CO~ ss~.r's capacity is easily oblah~ed once the top dead center position of thepiston is detected With r~re,~llce to ~IG. 4, there is shown a partial cross-sectionsl v;ew of a coll.~ssol in accol~ lce with a third pl~relled embo lim~nt Detected object 90 is, for ~Aa---~le, a pe. ..-~n~ magnet di~,osed on the side surface of piston 20.
Hall ge.-~ lator 91 is disposed on the piston side of ~;ylinder casing 3, and gen~ t~ s a signal co ~~onding to distance ~x between itself and detected object 90. Whilethe ~~f~,nce point from which Hall gel-f~ or 91 senses the top dead center position has been ~n~ilched with respect to that shown in FIG. 3, the same concept for ~ielect;ng the top dead center position as that employed in the second embodiment applies. That is, Hall gen~ld~or 91 senses a distance ~x between itself and a det~P-cted object ~;ciy~c~ling on piston 20.
Once the top dead center position is detectP~cl, the capacity of the co.l.~lessor is directly oblained. For example, as shown in FIG. 5, the f~ ~e...ç-~ of the conlyl~;,sol (piston stroke) is directly related to the top dead center distance ~x, i.e., for each distance ~x, there is a col~spo~ g displ~c~mPnt (piston stroke) at which the col-lylessor operates. This rel&tionsh;y holds true for the entire range of oyel~ting c~p~ities~ Thus, the stroke length of the piston is det~l...ined by reading from a graph such as that shown in Figure S
which coll~lates stroke length to the top dead center position. Acco,dingly, theoperational capacity of the coll.ylcssor can be directly dclcllllin~d from the top dead center position of the piston as it reciprocates between its ltisye;~ e .. and ~ xi...---.. ~x range of 0.3 - 1.3 mm.
The invention has been described in detail with respect to the preferred embo-1imP.nt~. These eml~1inl ~ however, are merely for example only, and this invention is not i.~çn~P~d to be restlictçd thereto. It will be easily undel~lood by those skilled in the art that variations and mo~lific~tions can be easily made within the scope of the yl~fellcd embo~limPntc, as defined by the appended claims.

Claims

1. A slant plate type compressor with a variable displacement mechanism comprising:
a compressor housing enclosing a crank chamber, a suction chamber, and a discharge chamber, said compressor housing including a cylinder block therein;
a plurality of cylinders formed in said cylinder block, said plurality of cylinders defining a compression space therein;
a piston slidably fitted within each of said cylinders, each of said pistons having a stroke length reciprocating between a top dead center position and a bottom dead center position;
a drive mechanism coupled to said pistons to reciprocate said pistons within said cylinders, said drive mechanism including a drive shaft rotatably supported in said housing, and coupling means for drivingly coupling said pistons with said drive shaft and for converting rotary motion of said drive shaft into reciprocating motion of said pistons, said coupling means including a slant plate having a surface disposed at a slant angle relative to a plane perpendicular to said drive shaft, said slant angle changing in response to a change in pressure in said crank chamber, the stroke length of said piston and the top dead center position thereof changing within a certain range in response to the change of said slant angle;
a communication path linking said crank chamber with said suction chamber;
control valve means for varying the capacity of said compressor by controlling the opening and closing of said communication path; and sensor means, disposed adjacent said cylinder, for sensing the top dead center position of said piston in said compression space, said sensor means being disposed on a valve plate which is adjacent to said cylinder.

2. The compressor as recited in Claim 1 further comprising a detected object disposed on a top surface of at least one of said pistons to oppose said sensor means.

3. The compressor as recited in Claim 2 wherein said detected object comprises apermanent magnet.

4. The compressor as recited in Claim 1 wherein said sensor means is a Hall generator.

5. A method of monitoring the capacity of a slant plate type compressor with a variable displacement mechanism, said compressor comprising a compressor housing in which a crank chamber, a suction chamber, a discharge chamber, and a cylinder block are disposed, a plurality of cylinders formed in said cylinder block, a piston slidably fitted within each of said cylinders and having a stroke length reciprocating between a top dead center position and a bottom dead center position, a drive mechanism coupled to said pistons to reciprocate said pistons within said cylinders, said drive mechanism including a drive shaft rotatably supported in said housing, and coupling means for drivingly coupling said pistons with said drive shaft and for converting rotary motion of said drive shaft into reciprocating motion of said pistons, said coupling means including a slant plate having a surface disposed at a slant angle relative to a plane perpendicular to said drive shaft, said slant angle changing in response to a change in pressure in said crank chamber, the stroke length of said pistons and the top dead center position thereof changing within a certain range in response to the change of said slant angle, a communication path linking said crank chamber with said suction chamber, said method comprising the steps of:
sensing the top dead center position of at least one of said pistons by sensing the closest distance between a detected object on said one piston and a sensing means fixedly disposed in said cylinder;
determining said stroke length of said piston from said top dead center position by reading said stroke length from a graph that correlates stroke length to top dead center position; and determining the capacity of said compressor from said stroke length of said piston.

6. The method according to Claim 5 wherein said detected object is disposed on a top surface of said one piston and said sensing means is disposed in a valve plate adjacent to said cylinder.

7. The method according to Claim 5 wherein said detected object is disposed on aside circumferential surface of said one piston and said sensing means is disposed along said cylinder adjacent to said side surface of said piston.