The invention relates to a spiral compressor, with a spiral element arrangement comprising two spiral elements movable periodically in relation to one another, and with a driving motor which forms a closed unit with the spiral element arrangement.

Such a spiral compressor is known from DE 38 38 382 Al. This compressor is driven by a plurality of expanding and contracting activating means, e.g. by means of piezo-electric motors, which are fed with an AC voltage from a supply circuit. The contact points between the activating means and the rotating spiral element are continously moved by the expansion and contraction movements of the activating means.

DE 41 30 393 Al describes a spiral compressor comprising an arrangement of spiral elements which consists of a first fixed spiral element and a second spiral element movable relative thereto which, in operation, performs an orbiting movement in relation to the first spiral element. The spiral elements are in contact with one another at specific points which shift in the course of the movement and thus enclose gas pockets which in the course of the movement move towards a midpoint of the spiral element arrangement and in so doing decrease in volume. In the region of the midpoint there is a pressure outlet at which gas under pressure is able to escape from the spiral element arrangement.

EP 0 133 891 Al discloses a further spiral compressor comprising two spiral element arrangements. An electric motor is provided between these two spiral element arrangements. This arrangement compensates

for axial forces of the two spiral element arrangements. Spiral compressors of that kind have the drawback, however, that they take up a relatively large space and in relation to their output their weight is high. In standard motors the speed of the compressor, and therefore also its displacement capacity, is limited. The power loss in terms of heat given off by the electric motor can lead to a temperature rise of the medium to be compressed, which in many cases is undesirable.

Furthermore, DE 33 32 292 Al discloses a spiral compressor which is driven by way of a sheave by a V-belt, for example in a motor vehicle. Compressors of that kind require a complicated lead-through bearing of the shaft from the sheave to the movable spiral element, which is difficult to seal. Compressors of that kind are widely used in motor vehicle air-conditioning systems in which the spiral compressor is intended to compress the coolant. Because of the problems associated with sealing, in this case there is generally a loss of coolant, which should be avoided for reasons of pollution control. In addition, replenishment of the coolant generates unacceptable costs.

The invention is based on the problem of providing a compressor which can be manufactured easily and has a large displacement volume combined with a small size and low weight.

In a spiral compressor of the kind mentioned initially, this problem is solved through forming the driving motor as a gear motor which is driven by a pressurized fluid and which comprises a gearwheel arranged eccentrically in an internally toothed annular gear, the gearwheel having fewer teeth than the annular gear, and at least one part of the gear motor being connected to a spiral element and performing an orbiting movement during operation.

This means that the compressor is in itself closed, that is to say, no movable parts have to be lead in from the outside, which would require a complicated seal. An additional thermal load, such as that which would occur, for instance, if an electric motor were present, is considerably reduced. On the contrary, the fluid can still be used to dissipate relatively quickly and without difficulty any heat that has been generated. Only two sets of connections are required, namely, one connection set for the admission and discharge of the drive fluid under pressure and one connection set for the admission and discharge of the gas to be compressed or a fluid to be compressed. A compressor of that kind can be used advantageously for air-conditioning systems in motor vehicles. Many motor vehicles already have a hydraulic or pneumatic system, for example, to reinforce brake force or to assist steering power, so that the fluid under pressure is in most cases already available. Normally, to generate the relative movement, one spiral element is moved while the other remains stationary. This is not the only possibility, however. It is also possible for both elements to move. To simplify the following explanations, the "movable" characteristic of a spiral element therefore refers to a system of coordinates in which the other spiral element is fixed. This coordinate system can, but need not, be fixed in relation to the housing. A motor of that kind can be constructed from relatively few parts. Compared with the output of other motors, for example, electric motors, its size can be kept relatively small and its weight can be kept relatively low. A gear motor of that kind at the same time allows high speeds, as a consequence of which the desired volumetric displacement of the compressor is achieved. During the orbiting movement the two spiral elements are not rotated relative to one another. On the contrary, all

points of the movable spiral element in a coordinate system which is determined by the other spiral element periodically describe a revolution. This revolution is generally circular. This is not, however, a prerequisite for the invention. On the contrary, the paths of movement of the points of the movable spiral element may also deviate from the circular path, and have, for example, an elliptical form or follow a path which is determined by a periodically changing function superimposed on a circular path. The orbiting movement, which in the simplest case is produced by an eccentrically mounted pin, can be converted in a simple manner into the movement which the movable spiral element performs in relation to the stationary spiral element. Consequently, only a single crank connection needs to be present between the motor and the movable spiral element. Mounting of the motor and spiral element arrangement can be unitized. The bearings can readily be adapted and matched to one another.

Advantageously, the fluid motor is a gerotor motor wherein the gearwheel and annular gear are arranged rotatably within a housing with their centers fixed at positions which are offset from each other. The position of the midpoints in the housing does not change. The drive control of the motor can be effected through fixed channels in the housing so that the construction of the motor becomes relatively simple.

It is preferable for the gearwheel to have an eccentrically arranged pin which is in operative connection with the movable spiral element. The eccentric pin generates the orbiting movement. The only measure that now has to be taken is to ensure that this pin is able to rotate in the co-orbiting spiral element and that the spiral element only orbits and does not rotate. A crank can consequently be formed

from just two machine elements, namely, from the gearwheel and the spiral element.

In another preferred embodiment, the annular gear has an eccentrically arranged pin which is in operative connection with the movable spiral element. In that case, the radial forces from the orbiting spiral element, which are transferred by the pin to the annular gear, can be absorbed by the outer bearing of the annular gear. This is the bearing with which the annular gear is rotatably mounted in the housing. This bearing can be of relatively large construction. It its accordingly able to absorb relatively large forces without the service life of the compressor being shortened as a result.

In another especially preferred construction, the fluid motor is in the form of an orbiting motor, in which, in operation, the gearwheel performs an orbiting movement in relation to the annular gear and is in operative connection with the movable spiral element. The orbiting movement of the gearwheel and of the annular gear can then be used directly to generate the orbiting movement of the spiral element. Other parts, such as eccentrically arranged pins, are not, in principle, required. The orbiting movement of such an orbiting motor need not be restricted to a purely circular path. It must merely contain a revolving movement which is matched to the shape of the spiral element.

Pump channels and tank channels are preferably provided alternately in the circumferential direction for control of the motor. Furthermore, slots are provided which have a fluid connection in a region between the gearwheel and the annular gear, the slots coming alternately into fluid connection with the pump and tank channels during the relative movement of gearwheel and annular gear. The pump and tank channels are in this case connected to the pump and

tank connection respectively, so that the pressure pockets formed between the annular gear and the gearwheel which are connected by way of the slots to the pump channels, are supplied with fluid under pressure. These pressure pockets increase their volume. As they do so, pressure pockets on the other side decrease in volume and are able to let away the resulting expressed fluid by way of the tank channels to the tank. A slot control of this kind can be effected relatively easily.

This is particularly easy if the slots are arranged in the base plate of the movable spiral element. The orbiting movement of the movable spiral element enables the individual pressure pockets to be brought at the correct time into connection with the pump channels or with the tank channels.

It is especially preferred for the annular gear to be rotatably mounted in a housing. It is consequently possible to allow the gearwheel to orbit only. The rotational movement is accommodated by the annular gear. Since considerably more space is available for the bearing of the annular gear than for a rotary bearing on a pin between the gearwheel and the spiral element, the bearing can be of relatively large dimensions. It is therefore able to absorb greater forces, which increases the service life of the compressor.

The spiral element may then advantageously be of one-piece construction with the gearwheel. This simplifies the construction of the compressor. Basically, only four parts are required, namely, two spiral elements, of which one contains the gearwheel, an annular gear and the housing.

In this construction, the slot control can be effected in a simple manner in that the slots are arranged in the annular gear in each case between two inwardly projecting teeth. When the annular gear

turns, the corresponding slots come into connection with the pump channels and the tank channels respectively. Since one more slot than pump channels and tank channels is provided, there is automatically the correct distribution of slots over the pump and tank channels.

In a further preferred construction, the fluid motor is arranged between two spiral element arrangements. In this manner axial forces of the two spiral element arrangements can be compensated. The corresponding bearings are thus relieved of pressure. They need essentially to accommodate only radial forces.

Advantageously, the movable spiral elements of both spiral element arrangements are driven by the same machine part of the motor. This embodiment also simplifies the construction of the compressor.

It is especially preferred in this case for the two movable spiral elements to operate in counter-phase to one another. It is possible in this manner to compensate partially for radial forces as well.

Preferably, a means preventing rotation is provided, which prevents the spiral element rotating relative to the fixed spiral element and which is constituted by several pins arranged in respective holes, the holes being large enough for them to allow a movement of the pin corresponding to the movement of the movable spiral element; the pin is arranged on a spiral element or a part fixedly joined thereto and the hole is arranged in the other spiral element or a part fixedly joined thereto. The pins may also orbit in the holes, corresponding to the movement of the movable spiral element. During this movement they lie adjacent to the wall of the hole. Since several hole- and-pin combinations are provided, levers are consequently created, which apply a counter-torque that prevents rotation of the movable spiral element.

Advantageously, at least the movable spiral element rides on the fluid. For that purpose it is sufficient for a thin film of this fluid to be formed between the spiral element and neighbouring parts. The fluid then allows a virtually friction-free movement of the spiral element. The drive output can then be used almost entirely for generating the desired pressure. Moreover, the fluid may also exert a pressure on the spiral element which results in improved sealing of the spiral element arrangement. By means of this pressure, counter-pressures that occur on compression of the gas in the spiral element arrangement, for example in the axial direction, can be compensated.

Advantageously, the fluid has lubricating properties and lubricates the spiral element arrangement. Additional lubricants need not then be introduced. This considerably simplifies keeping the gas to be compressed, for example, a coolant, clean. The compressor can have a long service life.

Advantageously, the fluid motor is in the form of a hydraulic motor. The forces required for the drive of the spiral element arrangement can be applied relatively easily with this form of motor. Hydraulic motors are able to run relatively rapidly and therefore perform correspondingly large numbers of pump or compression cycles per unit of time. This makes it possible to achieve the desired large displacement volumes.

Advantageously, the motor is separated by a flexible wall from the spiral element arrangement. This prevents fluid under pressure, for example, hydraulic fluid, mingling with the fluid to be compressed, for example, a coolant. The flexibility of the wall enables the movable spiral element to move so that despite this seal the function of the spiral compressor is guaranteed.

It is especially preferred in that case for the flexible wall to be of bellows-like construction and to surround the spiral element arrangement in the form of a ring, the base plates of the two spiral elements being joined to one another. By that means, the stresses on the wall which result from the movements of the movable spiral element, are kept relatively small.

When the wall is of sufficiently rigid construction in the circumferential direction, it may even serve to prevent the movable spiral element from unwanted rotation.

The invention is explained hereinafter with reference to preferred embodiments. In the drawings,

Fig. 1 shows a first embodiment of a spiral compressor with a gerotor motor,

Fig. 2 shows a section II-II according to Fig. 1,

Fig. 3 shows a further embodiment of a spiral compressor with a gerotor motor,

Fig. 4 shows a section IV-IV according to Fig. 3,

Fig. 5 shows a spiral compressor with an orbiting motor,

Fig. 6 shows a section VI-VI according to Fig. 5,

Fig. 7 shows a further construction of a spiral compressor with an orbiting motor,

Fig. 8 shows a section VIII-VIII according to Fig. 7, and

Fig. 9 shows a spiral compressor with two spiral element arrangements.

A spiral compressor 1 comprises a spiral element arrangement consisting of a movable spiral element 2 and a spiral element 3 fixed in a housing 16. The spiral element 2 is able to orbit relative to the spiral element 3, that is to say, is able to perform a periodic revolving movement, without, however, rotating relative to the spiral element 3. For that purpose, a

means preventing rotation is provided in the housing 16, comprising three holes 21 in the housing 16 and three pins 22 on the movable spiral element 2. One pin 22 projects into each hole 21. The hole 21 is sufficiently large for the pin 22 to perform in it an orbiting movement corresponding to the movement of the spiral element 2. Since, however, at least two holes 21 are provided, the spiral element 2 is unable to rotate relative to the housing.

The spiral element 2 is driven by a gerotor motor which comprises an annular gear 4 rotatably mounted in the housing 16 by means of a bearing 7 and a gearwheel 5 rotatably mounted on a bearing journal 6 in the housing 16. The annular gear 4 and the gearwheel 5 are arranged eccentrically with respect to one another, that is to say, the axis of rotation 18 of the gearwheel 5, formed by the midpoint of the bearing journal 6, does not coincide with the axis of rotation of the annular gear 4 formed by the midpoint of the bearing 7.

Pressure pockets are created in known manner between the annular gear 4 and the gearwheel 5. Some of the pressure pockets are connected to an input chamber 8, others are connected to an output chamber 9. Fluid under pressure is supplied from a pump connection 10 to the input chamber 8. The output chamber 9 is connected to a tank connection 11 so that fluid which is transported from the input chamber 8 into the pressure pockets and into the output chamber 9 on rotation of the annular gear 4 and the gearwheel 5 is able to flow back to the tank again. The annular gear 4 and the gearwheel 5 rotate jointly, but at different speeds.

An eccentric pin 14 is arranged eccentrically on the gearwheel 5, that is to say, the axis 19 of the eccentric pin describes a circular movement around the axis 18 of the gearwheel 5 on rotation of the gearwheel

5. The eccentric pin 14 is mounted in the spiral element 2 by means of a rotary bearing 15. On rotation of the gearwheel 5, the orbiting movement of the eccentric pin 14 is therefore transferred to the spiral element 2, and the spiral element 2 orbits in the fixed spiral element 3. As this happens, between the movable spiral element 2 and the fixed spiral element 3 gas pockets are created, which become increasingly smaller so that gas drawn in by way of an intake connection 12 can ultimately be discharged at an increased pressure at an outlet connection 13. Between the base plates 23, 24 of the spiral elements 2, 3, of which the base plate 24 of the fixed spiral element 3 is fixedly connected to the housing 16, there is a flexible wall 25 in the form of a bellows. This prevents hydraulic fluid and compressed gas from mixing. Rotation can be prevented by means of the wall, if this is rigid enough in the circumferential direction. At any rate, the wall 25 allows the orbiting movement of the movable spiral element 2.

Figs 3 and 4 show a further construction of a spiral compressor 1' with a gerotor motor. Identical parts have here been provided with the same reference numbers and corresponding parts have been provided with dashed reference numbers. The fluid control for the gerotor motor is not shown for the sake of clarity. It is, however, taken as known. The flexible wall 25 and the means preventing rotation 21, 22 have also been omitted from the following Figures. They may, however, also be used in these constructions.

Whereas in the construction shown in Figs 1 and 2 the annular gear 4 was mounted eccentrically in the housing, while the gearwheel 5 was arranged centrally with respect to the housing on the bearing pin 6, that is to say, centred with respect to the fixed spiral element 3, in the construction shown in Figs 3 and 4 the gearwheel 5' is eccentrically mounted, while the

annular gear 4' is mounted essentially centred in the housing 16', that is to say, its centre line 18' is a predetermined distance from the centre line 20' of the gearwheel which is rotatably mounted on a correspondingly displaced bearing pin 6' .

This time, the annular gear 4' carries an eccentric pin 17 which is in connection by way of a bearing 15' with the movable spiral element 2. If annular gear 4' now rotates under the action of the fluid under pressure, the eccentric pin 17 describes an orbiting movement around the axis 18' of the annular gear 4' , so that the movable spiral element 2 also performs a corresponding revolving movement.

In order to save on a further bearing, according to an embodiment shown in Figs 5 and 6, an orbiting motor is used instead of a gerotor motor. Here, identical parts have been provided with the same reference numbers and corresponding parts have been provided with reference numbers increased by 100.

The annular gear 104 is now stationary, that is to say, it no longer rotates in relation to the fixed spiral element 3. Instead, the gearwheel 105 rotates and orbits in the annular gear 104, as is known from an orbiting motor. For that purpose, the gearwheel 105 is mounted eccentrically in the annular gear 104. The gearwheel 105 has one tooth fewer than the annular gear 104. A drive pin 114 is provided centrally on the gearwheel 105. It is connected by way of a bearing 15 to the movable spiral element 2. The bearing 15 allows a rotation between the drive pin 114 and the movable spiral element 2. If the gearwheel 105 now orbits in the annular gear 104, and consequently in the housing 116, this orbiting movement is transferred to the movable spiral element 2. Rotation of the spiral element 2 is prevented by means preventing rotation (see above) not illustrated.

The annular gear 104 and the gearwheel 105 are matched to one another so that the orbiting movement of the gearwheel 105 exactly corresponds to the desired orbiting movement of the movable spiral element 2.

A pump channel 26 which is connected to the pump connection 110 is provided in the housing 116. A tank channel 27 is also provided, and is connected to the tank connection 111. Slots 28 are provided in the base plate 123 of the movable spiral element 2. These slots, although they do not correspond to the sectional view, are additionally shown in Fig. 6. If the movable spiral element 2 performs an orbiting movement, these slots 28 comes alternately into connection with the pump channels 26 and the tank channels 27. Either hydraulic fluid under pressure enters the pressure pockets which form between the annular gear 104 and the gearwheel 105 and are in the process of increasing in volume on account of the relative movement between the annular gear 104 and the gearwheel 105, or a connection to the tank connection 111 is formed at the pressure pockets that are in the process of decreasing in volume. About half of the slots 28 are connected to the pump channels 26, while the remainder are connected to the tank channels 27. The number of pump channels 26 and of tank channels 27 corresponds to the number of teeth on the gearwheel 105. The number of slots 28 is larger by one. Connection of the individual pressure chambers at the correct time therefore occurs virtually automatically.

Figs 7 and 8 show a further embodiment in which identical parts are provided with the same reference numbers as in Figs 5 and 6 and corresponding parts are provided with correspondingly dashed reference numbers.

In this embodiment the annular gear 104' is mounted rotatably in the housing 116'. Retaining the relative movement between the annular gear 104' and the gearwheel allows the gearwheel 105' only to orbit,

while the rotary portion of the relative movement between the annular gear 104' and the gearwheel 105 is taken over by the annular gear 104', which is able to rotate freely in a bearing 107 in the housing 116'. Since the bearing 107 can be of considerably larger dimensions than the bearing 15, larger forces can also be accommodated, so that the service life of the spiral compressor 101' can be considerably extended.

Since the movement of the gearwheel 105' is not restricted to a purely orbiting movement or a revolving movement, the movable spiral element 2' and the gearwheel 105' can be of one-piece construction. As a result, the construction of the spiral compressor 101' is consequently considerably simplified. The movable spiral element 2' can be formed in an end face of the gearwheel 105'.

To control the movement of the motor 104', 105', pump channels 26' and tank channels 27' are again provided here and are connected to a pump connection 110 and a tank connection 111 respectively. In the annual gear 104' there are formed slots 28' that open between two inwardly projecting teeth 29 of the annular gear 104 into the intermediate space between the annular gear 104' and the gearwheel 105'. By rotating the annular gear 104', these intermediate spaces come alternately into connection with pump channels 26' and tank channels 27', giving a correct control of timing.

Hydraulic motors are advantageously used in all cases. When the hydraulic liquid, as is normally the case, has lubricating properties, it can be used at the same time to lubricate the corresponding bearing points 7 and 15. At the same time, the hydraulic fluid can be used to form a film of fluid between the movable spiral elements 2 and the housing and the gearwheel, so that here too a virtually friction-free movement is achieved. When this film of fluid is kept at a certain pressure, axial forces, which occur during

compression of the gas between the movable and the fixed spiral element 2, 3, can be at least partially compensated. This improves the seal between the movable and the fixed spiral elements 2, 3 and thus the degree of efficiency of the spiral compressor. This seal can furthermore be achieved in that the pressurized fluid is supplied from the side remote from the movable spiral element 2 to the pressure pockets between the annular gear 4 and the gearwheel 5, and the annular gear 4 and the gearwheel 5 are loaded correspondingly from this side with a certain pressure. This pressure can then also be used to compensate for axial forces.

Fig. 9 shows a further construction, in which two movable spiral elements 202, 202' are provided. The associated fixed spiral elements have been omitted for clarity. The construction shown in Fig. 9 corresponds otherwise substantially to Figs 7 and 8 so that reference numbers increased by 100 with respect to the reference numbers in Figs 7 and 8 are used here for corresponding parts. The gearwheel 205' is constructed in one piece with the spiral elements 202, 202'. The gearwheel 205' is mounted eccentrically in the annular gear 204' which in its turn is again rotatably mounted in the housing 216' by way of a bearing 207. The relative movement between the annular gear 204' and the gearwheel 205', which is composed of an orbiting and a rotating movement, can now be resolved into a purely orbiting movement of the gearwheel 205', while the rotating movement is performed exclusively by the annular gear 204'.

Since the axial pressures that occur on compression of gases or other fluids between the spiral elements now act from both sides equally, they cancel each other out. The bearing 207 then needs to be able to absorb only radial forces. If the spiral elements 202, 202' are arranged, for example, so that they

operate in counter-phase, radial forces also can be partially compensated.