GB2173261A

GB2173261A - Swash plate compressor

Info

Publication number: GB2173261A
Application number: GB08602483A
Authority: GB
Inventors: Masakatsu Sakaki; Tamotsu Daikohara
Original assignee: Sanden Corp
Current assignee: Sanden Corp
Priority date: 1985-02-25
Filing date: 1986-01-31
Publication date: 1986-10-08
Also published as: MX160536A; GB8602483D0; KR860006635A; CN86101181A; AU5278686A; GB2173261B; AU584665B2

Abstract

A rotational speed detecting device for a swash plate type compressor comprises a magnetic substance (30) disposed on the outer surface of the swash plate (14) and movable therewith. An electromagnetic sensor (31) is mounted on the casing (1) of the compressor and is positioned thereon opposite the centre of the locus of the motion of magnetic substance (30). Electromagnetic sensor (31) detects the magnetic flux density in magnetic substance (30) each time it passes opposite electromagnetic sensor (31) and generates a voltage pulse. The period and amplitude of the voltage pulses generated by electromagnetic sensor (31) are proportional to the rotational speed of the compressor. In the preferred embodiment, a lubricating oil port (33) is located in casing (1) at the center of the locus of motion of magnetic substance (30). A plug (32) is provided to overlay port (33) and is formed to receive electromagnetic sensor (31). <IMAGE>

Description

SPECIFICATION Swash plate compressor This invention is related to swash plate type compressors generally and more specifically to a rotational speed detecting device for a swash plate type compressor.

In automobiles equipped with air conditioning equipment, an air conditioning compressor is typically mounted in the engine compartment and is coupled to the engine output through transmission belts and an electromagnetic clutch. In such systems, it is desirable to interrupt the driving force to the compressor in some circumstances, e.g., in the event of malfunction of the compressor, to prevent destructive damage to, or breakage of the component parts of, the compressor and also to prevent serious damage to the engine.

Such interruption is particularly desirable where the compressor and other auxilliary equipment, e.g., an alternator, are coupled to the engine output through a single power transmission belt to ensure that operation of the other equipment remains unaffected by the compressor malfunction.

Various prior art devices are known for detecting compressor malfunction by detecting changes in the rotational speed of the compressor and interrupting the driving force to the compressor when the rotational rate falls below a reference rate. One techinque for detecting rotational speed in those prior art devices has involved use of a magnetic substance coupled to the compressor drive shaft and rotatable therewith. A magnetic detector is disposed on the compressor housing opposite the locus of rotation of the magnetic substance which detects the magnetic flux density of the magnetic substance at successive passes and generates voltage pulses having a period and amplitude proportional to the rotational rate of the compressor. Those prior art devices have not, however, been entirely satisfactory and have, in fact, been totally ineffective in detecting certain compressor malfunctions.For example, if the connecting rod extending between the swash plate and reciprocating piston were destroyed in a compressor equipped with one of the prior art devices, that fact would not be detected as such a malfunction would not affect the continued rotation of the drive shaft and magnetic substance coupled thereto or the operation of the detector to detect the magnetic flux density of the magnetic substance and to generate voltage pulses responsive thereto. Thus compressor operation would not be interrupted through the essential compressor functions, i.e., suction compressor and discharge of refrigerant, were no longer being performed.

According to the invention, a swash plate compressor has a rotary driving shaft; a housing rotatably supporting the rotary shaft; a wedge shaped rotor coupled to the rotary shaft and rotatable therewith; a swash plate disposed adjacent to an inclined surface of the rotor and carrying out a swash motion in response to rotation of the rotor; and a speed detecting device comprising a magnetic substance disposed at the outer circumference of the swash plate and an electromagnetic sensor disposed on the housing opposite a locus of motion of the magnetic substance, the sensor being arranged to generate pulse signals in response to variations in the magnetic flux density which take place each time the magnetic substance passes the electromagnetic sensor during the swash motion of the swash plate.

With this construction, the speed detecting device is effective to detect the occurrence of compressor malfunction by sensing changes in the rotational speed of the compressor.

The rotational speed detecting device comprises a magnetic substance, such as an iron core or permanent magnet, disposed on the outer surface of the swash plate and an electromagnetic sensor mounted on the compressor casing opposite the locus of motion of the magnetic substance. In operation, movement of the swash plate results in corresponding reciprocation of the magnetic substance so that the magnetic substance periodically comes to a position opposite the electromagnetic sensor. The electromagnetic sensor detects the magnetic flux density in the magnetic substance at each passing and generates a voltage pulse. The period and amplitude of the voltage pulses are proportional to the rotational speed of the compressor.Thus, when the rotational speed falls below a predetermined reference rate, that indicates that a compressor malfunction has occurred and appropriate action can then be taken to interrupt the driving force to the compressor by disengaging the electromagnetic clutch.

A more complete understanding of the invention can be had by reference to the following detailed description taken in conjunction with the accompanying drawing, in which: Figure 1 is a sectional view of a swash plate type compressor incorporating a rotational speed detecting device, and in accordance with the present invention.

Fig. 1 shows a swash plate type compressor for a vehicle air condition system and including a cylindrical casing 1 having a front housing 10 and a cylinder head 6 coupled to the front and rear ends thereof, respectively.

A cylinder block 2 is also provided and includes a plurality of cylinder bores 2a disposed at regular angle intervals around the axial center line of casing 1. A valve plate 3 is disposed adjacent the surfaces of cylinder head 6 and cylinder block 2 and is sandwiched therebetween. Valve plate 3 is coupled to cylinder head 6 through a gasket 4 and is also coupled to cylinder block 2 through gasket 4 and a suction valve 5.

Cylinder head 6 includes a suction chamber 7 and a discharge chamber 8 formed on the interior side thereof which communicate with cylinder bore 2a through a suction port (not shown) and a discharge port (not shown) formed in valve plate 3.

Suction valve 5 and a discharge valve (not shown) are disposed proximate the suction port and discharge port formed in valve plate 3 and are operative to open and close in response to pressure differentials between cylinder bore 2a and suction chamber 7 and cylinder bore 2a and discharge chamber 8 respectively. Valve plate 3, gasket 4, suction valve 5 and cylinder head 6 are all coupled to casing 1 through bolts 9.

A drive shaft 12 extends through the axial core of casing 1 so as to penetrate an opening in front housing 10 and is rotatably supported with front housing 10 through a radial bearing 11 positioned therein. The end portion of drive shaft 12 projecting outside of casing 1 is coupled to the vehicle engine (not shown) through an electromagnetic clutch (not shown).

A wedge shaped rotor 13 is coupled to drive shaft 12 and rotates therewith. A swash plate 14 is mounted to drive shaft 12 adjacent the incline surface of rotor 13 and includes a bevel gear 15 positioned at the center thereof. A corresponding bevel gear 17 having an identical number of gear teeth is fixedly mounted on cylinder block 2 and cooperates with gear 15 through a steel ball 16 to facilitate swashing movement of swash plate 14 toward and away from front housing 10, without rotation, as drive shaft 12 and rotor 13 are driven.

A connecting rod 21 is coupled to one end of swash plate 14 and extends therefrom and is coupled at its opposite end to a piston 22 fitted within cylinder bore 2a.

A magnetic substance 30 is disposed on the outer surface of swash plate 14 and is movable therewith. An electromagnetic sensor 31 is mounted on casing 1 and is positioned thereon opposite the center of the locus of motion of magnetic substance 30.

In operation, when drive shaft 12 is driven, swash plate 14 drives piston 22 to reciprocate within cylinder bore 2a. Movement of swash plate 14 also results in reciprocation of magnetic substance 30 so that it periodically, i.e., two times per rotation of drive shaft 12, comes to a position opposite electromagnetic sensor 31. Electromagnetic sensor 31 detects the magnetic flux density in magnetic substance 30 at each passing and generates a voltage pulse. The period and amplitude of the voltage pulses are proportional to the rotational speed of the compressor. Thus, when the speed falls below a predetermined reference rate, that indicates that a compressor malfunction has occurred and appropriate action can then be taken to disengage the electromagnetic clutch and thus interrupt the driving force to the compressor.This may occur, for example, if gears 15 and 17 are damaged so that they are no longer effective to prevent rotational movement of swash plate 14. In that event, swash plate 14 is allowed to rotate with drive shaft 12 resulting in breakage of connecting rod 22. This malfunction is detected by the detecting device which senses the change in the period and amplitude of the voltage pulses. Because swash plate 14 is allowed to rotate, electromagnetic sensor 31 will detect magnetic substance 30 only once per rotation of drive shaft 12 as compared to two times in normal operation, which indicates a compressor malfunction has occurred.

Referring again to the figure, one technique for attaching electromagnetic sensor 31 onto casing 1 is illustrated. As shown in the figure, front housing 10 cooperates with cylinder block 2 to form a crank chamber 1a in the interior of casing 1 between the inner wall surfaces of front housing 10 and cylinder block 2. A port 33 for permitting lubricating oil to enter and exit crank chamber 1 a is provided and is located on casing 1 so as to correspond to the center of the motional locus of magnetic substance 30. A plug 32 is provided to cover port 33 and is designed to receive electromagnetic sensor 31. Plug 32 is formed to match the external shape of the body of the electromagnetic sensor and is comprised of non-magnetic substance so as not to affect the operation of electromagnetic sensor 31 to detect magnetic substance 30.

Claims

1. A swash plate compressor having a rotary driving shaft; a housing rotatably supporting the rotary shaft; a wedge shaped rotor coupled to the rotary shaft and rotatable therewith; a swash plate disposed adjacent to an inclined surface of the rotor and carrying out a swash motion in response to rotation of the rotor; and a speed detecting device comprising a magnetic substance disposed at the outer circumference of the swash plate and an electromagnetic sensor disposed on the housing opposite a locus of motion of the magnetic substance, the sensor being arranged to generate pulse signals in response to variations in the magnetic flux density which take place each time the magnetic substance passes the electromagnetic sensor during the swash motion of the swash plate.

2. A compressor according to claim 1, wherein the magnetic substance is an iron core.

3. A compressor according to claim 1, wherein the magnetic substance is a permanent magnet.

4. A compressor according to any one of the preceding claims, wherein the housing has a hole formed therein for allowing fluid to en ter and exit the housing and a plug for closing the hole and accommodating the electromagnetic sensor.

5. A swash plate compressor, substantially as described with reference to the accom panying drawing.