Scroll-type fluid machinery

Abstract: A scroll-type fluid machine comprises an orbiting scroll (1) with an axially projecting involute wrap (15), a stationary scroll (2) with an involute wrap (10) mating with the wrap (15) of the orbiting scroll (1) and a main shaft (5) inserted in a central axis hole of the stationary scroll (2) for driving the orbiting scroll (1) in an orbital movement. The wrap (10) of one scroll (2) is longer by a half turn than the wrap (15) of the other scroll (1) extending inwardly and/or outwardly in the form of spiral involute, and both wraps (10, 15) are in nearly end-to-end contact at a desired phase place during the orbiting movement. Improved compression efficiency is thus achieved with an overall inexpensive design and the possibility of effective sealing.

Description: BACKGROUND OF THE INVENTION [Field of the Invention] This invention relates to a scroll-type fluid machinery functioning compressors, expanders or vacuum pumps, and more particularly to a twin unit scroll-type fluid machinery having stationary scrolls axially disposed on both surfaces of an orbiting scroll. [Description of the Prior Art] Scroll-type compressors are known in the art which comprise: a stationary scroll having a first wrap formed in an involute spiral located within a casing which encloses all members thereof with a peripheral wall provided with a suction port and an exhaust port respectively at a peripheral region and a central region thereof, an orbiting scroll having a second wrap formed also in the involute spiral mating with the first wrap at least in a pair of line contacts forming a pocket between the line contacts of the first and second wraps, wherein, during the orbiting scroll is driven with an orbital movement rather than a rotational movement, air is taken through the suction port into the pocket the volume of which is reduced as it moves along the scroll surfaces to the central region, the compressed air is discharged through the exhaust port. There is disclosed in U.S. Pat. No. 4,129,405 a kind of devices referred as a single unit scroll-type machinery for expanding, compressing or displacing fluid with a stationary scroll and an orbiting scroll interfitting each other, and is disclosed in U.S. Pat. No. 4,192,152, and Japanese Patent Publication 63-42081 another kind of devices referred to as a twin unit scroll-type machinery for expanding, compressing or displacing fluid with a pair of stationary scrolls having respectively a wrap inside and with an orbiting scroll having each wrap on both surfaces which are interfitted respectively with the stationary scrolls mating with the wraps. Either of the scroll-type machineries above, however, creates issues at each region of suction port and exhaust port, because each of the warps of the stationary scroll and the orbiting scroll is formed in the same turns engaged with a 180 degree phase difference. That is, in the region of suction port, there has to be provided another suction port at a 180 degree apart from the first suction port, where each beginning end of the wraps contacts respectively with other wrap side walls forming one of the utmost contact lines of the pockets, or has to provide a half-way detour passage circumferentially around the peripheral of the wraps connecting the suction port with other side of contact line 180 degrees apart therefrom, resulting in the machinery being large in size and sophisticated in machining and assembling processes. The two suction ports, further, means two pockets at a 180 degree apart which is hard to be simultaneously compressed requiring a double power, and reduces an intake efficiency because the fluid volume of the fluid sucked in the pockets is limited by the port area and the detour passage. The issue in the region of the exhaust port, on the other hand, resides in the volume of the pockets at the central portion where an eccentric shaft has to be provided axially parallel with a drive shaft to drive the orbiting scroll together with a bearing thereof, where the exhaust port and a terminal wrap end have to be provided at the peripheral circumference of the bearing, wherein the involute spiral terminates before reaching the center thereof without shortening its length for more smaller pocket volume because there has to be disposed a pair of terminal wrap ends 180 degrees apart. Thus, the conventional machineries result in the pocket volume to be released at the exhaust port remaining as large as not to attain a maximum compression ratio. What is worse, the greater volume of the pocket at the last stage makes the sealing line longer, and makes the leakage easier resulting in that a higher compression efficiency is not attainable. To solve the failures, in a single unit scroll-type machinery, a constitution may be provided wherein a main shaft to drive an orbiting scroll is disposed at the back surface thereof, and an exhaust port is provided at the center of a stationary scroll. Whereas, in the twin unit scroll-type machinery as shown later in the embodiment of the present invention, the main shaft to drive the orbiting scroll has to be disposed through the stationary scrolls at the center thereof, because the orbiting scroll has to be oppositely interfitted with the stationary scrolls so as to arrange a pair of stationary scrolls at both sides of the orbiting scroll, wherein the failures are inherent urging the constitution that the exhaust port and the terminal wrap ends have to be disposed at the peripheral circumference of the bearing where the involute spiral terminates before reaching close to the center thereof. In either scroll-type machineries, because the wrap end slides on the mirror surface opposing substantially in a surface contact with a grease lubricated to compress the fluid, the scrolls have to be aligned opposing each other parallelly and axially within a strict limitation. A plurality of thrust adjusting means is provided to solve the issue in either scroll-type machineries at the peripheral wall of the stationary scroll opposing the orbiting scroll, the wall of which is located outside the wrap space where the compression is effected, three set in a 120 degree distribution for example, whereby the parallel alignment of the scrolls and the thrust adjustment is subjected. Because the twin unit scroll-type machinery above, however, is formed in a constitution that the orbiting scroll is interfitted with a pair of stationary scrolls at both sides, the thrust adjusting means are provided at each of stationary scrolls to adjust the thrust through the orbiting scroll commonly held at both sides thereof. Thus, if the thrust of one side of the stationary scroll is adjusted, then the thrust already adjusted on the other side of the stationary scroll becomes deviated to make the matter difficult. Therefore, as in a prior art in Japanese Patent Publication 63-42081, utilizing a main shaft which is driven in orbital movement and disposed coaxially with a pair of stationary scrolls, and a plurality of eccentric axes to restrict a rotational movement, the scrolls are intended to be precisely assembled in a unit with bearings, a casing and so forth, to avoid the deviations of the scrolls from being parallel to each other, and the misalignment of the thrust. The constitution of the three scrolls with the main shaft and the eccentric axes assembled in one unit with a plurality of parallel axes does not allow the orbiting scroll to have the slightest axial deviation. Even if the deviation may be allowed within some extent, it brings another failure that the tolerance may require further an extra axis power. Though the twin unit scroll-type fluid machinery has been believed to have such a great advantage as to form it small in size allowing the compression procedure at both sides of the orbiting scroll, and a two stage compressor with a higher compression ratio, hence, with a better power efficiency, the twin unit machinery has not been realized successfully because of the troublesome issues said above. Scroll-type fluid machines having two scrolls with respective wraps being engaged with a 180° phase difference are also disclosed in DE-A-2 160 582 and EP-A-0 298 315. For all these machines, one wrap is longer than the other wrap by at least half a turn extending inwardly. SUMMARY OF THE INVENTION It is an object of the present invention to provide a scroll-type fluid machine with a higher suction efficiency. This object is solved by the machine set forth in claim 1. A preferred embodiment of the present invention provides a scroll-type fluid machinery with an advanced sealing means and an advanced compression efficiency or expansion efficiency. Another embodiment of the present invention provides a scroll-type fluid machinery, particularly in a twin unit machinery with a reasonable tolerance in an assembly alignment and a machining deviation range not so strict as it used to be, wherein the tolerance is absorbed to maintain the tangential sealing between the wraps, and the radial sealing between the scroll ends and the mirror wall surfaces opposing thereto so as to attain the compression efficiency or the expansion efficiency desired. Yet another embodiment of the present invention provides a scroll-type machinery, capable of precise self-alignment in parallel, capable of self-adjustment of the distance between the scrolls, during the orbit movement thereof. Still another embodiment of the present invention provides a scroll-type fluid machinery, absorbing precisely an axial misalignment of the orbiting scroll, capable of compression or expanding as desired without increasing the axis power unnecessarily. In a twin unit scroll-type fluid machinery having a main shaft for driving an orbiting scroll, which main shaft is disposed through a plurality of bearings into a pair of stationary scrolls, a stationary scroll wrap extends approximately another half turn relative to a wrap of the orbiting scroll toward the peripheral region, instead as in the conventional one, so that wraps with the same turns are engaged 180 degrees apart, wherein each of the wraps of the stationary scroll and the orbiting scroll is able to contact nearly end to end during the orbit movement of the orbiting scroll. The present invention is applicable not only to the twin unit as above, but also to a single unit scroll-type fluid machinery having a stationary scroll which is disposed with a main shaft at the center thereof. A constitution reverse to the above may also be possible, that is, to form the wrap of the orbiting scroll longer more than a half turn than that of the wrap of the stationary scroll. Referring to FIGS. 1 and 2, the function of the present invention will be described separately on the suction portion of the compressor hereinafter. The suction portion at the peripheral region, firstly, because an external wrap end(10b) of stationary scroll(2) is extended a half turn over that of the orbiting scroll, the wrap ends(10b, 15b) come in contact with each other whereat a suction port(8) is provided. The single port(8), instead of providing two suction ports located 180° apart, or instead of providing a detour passage between contacting lines 180 degrees apart as in the conventional one, allows the machinery to be small in size and to save the machining steps. The first pocket(30B) between the first and the next contact lines becomes greater than the conventional one, because the external wrap end(10b) of the stationary scroll(2) is extended by 180 degrees, which increases the intake efficiency as well. Further to say referring to FIG. 2(a), the single pocket(30B) for the initial intake through the single suction port(8) with a greater volume than the divided volume into two pockets as in the conventional one, is continuously compressed reducing the volume from the suction portion to the exhaust portion, whereby it makes the machinery possible to increase the compression ratio and the exhaust pressure, too. At the exhaust portion of the machine shown in the Figures, an internal wrap end (10a) of stationary scroll(2) is extended half a turn relative to an internal wrap end(15a) of the orbiting scroll (1) in an involute spiral toward the peripheral of the bearing to form in a constitution in which the internal wrap ends(10a, 15a) come to contact with nearly end to end alignment during the orbit movement of the orbiting scroll (1), whereby the final stage of the pocket(30A) becomes the smallest volume, and hence, the advanced exhaust efficiency and the higher compression ratio can be achieved (FIGS. 1 and 2(a)). It is preferable, as shown in FIG. 1, to dispose the wrap end(10a) of the stationary scroll(2) at a peripheral circumference wall(4a) forming a bank(4) for a central axis hole(2a). The internal wrap end(15a) of the orbiting scroll(1), as shown in FIG.1, is disposed at the dead end(21a) of the scroll groove(21) of the stationary scroll between the peripheral circumference wall(4a) of the bank(4) forming the central axis hole(2a) and a wrap (10c) next to the wrap(10a) thereof, the dead end wall(21a) of the scroll groove (21) being formed in an arc of a half circle with which the internal wrap end (15a) of the orbiting scroll (1) is slidably in contact, whereby the sealing between the internal wrap end(15a) and the dead end wall(21a) of the wrap groove(12) is secured. It is preferable to form the dead end wall(21a) of the scroll groove(21) in the arc of a half circle with a radius (X) almost the same as to the distance of the eccentricity - a distance between the center(la) of axis hole for the orbiting scroll(1) and the center(2a) of axis hole for the stationary scroll(2), or in other words, an orbiting radius(x). In order to apply the present invention to compressors, an exhaust port(7) is provided at the dead end wall(21a) of the scroll groove to discharge the fluid, wherein the final stage of the pocket is in the smallest volume to secure the compression efficiency. It is further recommendable, as in FIG. 2, to provide the exhaust port(7) with some distance on the bank(4) for the axis hole(1a) away from the dead end wall(21a) of the scroll groove(21), instead of next thereto, and connected through a passage (31), to obtain a further improved compression efficiency. As described in the earlier statement, the pocket at the final stage in a smaller volume provides a shorter sealing line which assures a better sealing effect, and prevents a returning flow of the fluid, resulting in further improving the compression efficiency. Thus, the constitution above provides the improved intake/exhaust efficiency at either sides of suction port(8) and exhaust port and a better sealing performance. In the twin unit, however, the feature does not realize, if the scrolls are not disposed in parallel if the distances between them are not kept precisely, and if those alignments are not adjustable easily. Therefore as shown in FIG. 4, a twin unit scroll-type fluid machinery is provided which comprises: an orbiting scroll (1) disposed with a main shaft(5) axially movable relative to stationary scrolls(2A, 2B) within a short distance, a sealing member(9) disposed at least in a groove at the wrap ends (101, 151) of the orbiting scroll(1) resiliently enforced evenly against mirror surfaces(11a, 21a) of the stationary scrolls(2A, 2B), wherein the interfaces between the mirror surfaces and the wrap ends(101, 151) are formed capable to be sealed with the sealing member(9). It is not restrictively intended to seal the interface with the sealing member(9) alone, but an oil lubricant may be expected as a sealant cooperatively. The means for resiliently enforcing evenly the sealing member(9) may be realized with either sealing member(9) made of a resilient material as in an enlarged drawing FIG. 3(a), or with a sealing member(9) with a resilient member (91) disposed in a seal groove (90) of the wrap end as in FIG. 3(b). The invention above, because the orbiting scroll(1) is axially movable within the desired distance, and because the sealing members(9) are inserted in the groove at the wrap ends(101, 151) of the orbiting scroll(1) uniformly urged to the oppose mirror surfaces(lla, 21a), provides a feature that a thrust force on the interface due to the machining deviation and misalignment in the assembly process are compensated with the resilient force of the member, and thus, the self-alignment can be achieved. In other words, even if the machinery involve the machining deviation and the misalignment, the adjustment for the center of orbiting scroll(1) is self-devotedly accomplished without any manual axial adjustment or realignment. Further to the above, as the sealing member(9) is elastic or is variable in length, the sealing member(9) easily absorbs the axial deviation of the orbiting scroll (1). Still adding to the above, as the orbiting scroll(1) is resiliently interfitted through the sealing member(9) between the stationary scrolls(2A, 2B), instead of being fixedly disposed, the axial power does not uselessly increase. The simple constitution above, therefore, according to the present invention, because it gives the high compression efficiency and the advanced sealing performance around the wrap ends of the suction portion and interfaces with other scrolls anywhere between thereof, provide primarily the twin unit scroll-type compressors useful in the market. The description above is associated with the constitution and function of compressors, but it is obviously understandable that the present invention is easily applicable to fluid positive displacement pumps and expanders. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are top plan sectional views of one set of wraps showing their schematic forms and constitutions constructed in accordance with the present invention. FIG. 3 is a longitudinal sectional view of a twin unit scroll-type fluid machinery in which FIGS. 3(a) and 3(b) are longitudinal cross sectional detailed views of a portion of sealing members. FIG. 4 is a partial longitudinal section view showing a portion of center axis. FIG. 5 is a partial longitudinal section view showing a portion of orbiting shaft. DETAILED DESCRIPTION OF THE DRAWINGS Certain aspects of the present invention will be illustratively described in detail with reference to the following drawings. FIGS. 1 and 2 are views showing wraps of a scroll-type compressor. Referring FIG. 1, reference numeral (10) indicates a wrap formed inside a stationary scroll(2A or 2B), formed as a spiral involute of 3-3/4 turns started from a peripheral wall(4a) of a bank(4) for a central hole for a stationary axis(2a) of a main axis(6) provided at the central portion, having a dead end wall(21a) of a scroll groove(21) formed as an arc wall of a half circle started from a wrap start end(10a) at the bank wall(4a) to a wrap (10c) next to the wrap start end (10a), which dead end wall(21a) has an exhaust port(7), or a passage connected to outside members. The dead end wall(21a) was formed with a radius almost the same as an eccentricity distance(x) between centers of an orbiting scroll axis(la) and the stationary scroll axis(2a). A wrap(15) for an orbiting scroll(1), on the other hand, was formed as spiral involute of 2-3/4 turns, a 180 degree turn shorter than the stationary scroll wrap(10) at each end of start and terminal respectively, which wrap start end(15a), having a section rounded circular end, was slidably in contact with the circular surface of the dead end wall(21a) of the scroll groove (21) during the orbital movement of the orbiting scroll (1). As the orbiting scroll(1) rotated around the stationary scroll center(1a), the wrap start end(15a) of the orbiting scroll slidably moved along the dead end wall(21a), whereby a pocket(30A) was kept compressing until the wrap start end (15a) reached the inlet edge of the exhaust port(7), with a final volume of 24% and a sealing line of 33% less than that of a conventional pocket which had been released at 180 degrees behind the exhaust port(7), thus achieving a higher compression efficiency. Because the exhaust port(7) was provided at the dead end wall(21a) in the above embodiment, the final pocket(30A) was released as soon as the wrap end(15a) reached the inlet edge of the exhaust port(7), or it came to contact with the next wrap(10c). To solve the failure above, the exhaust port(7) was provided, as in FIG. 2, at the bank(4) ahead of the dead end wall(21a) with a passage(31) connected the dead end wall(21a) and the port(7). In this constitution, the final pocket(30A) was held until the wrap end(15a) nearly reached the wrap start end(10a) or the bank wall(4a), with a final volume of 11% and a sealing line of 24% less than that of the above embodiment, whereby a further advanced compression ratio was recognized. A wrap terminal end(10b) of the stationary scroll, in the embodiment, was also extended another 180 degree turn, and was in contact with the wrap terminal end(15b) of the orbiting scroll where it formed one of contact lines of the pocket(30B), where a suction port(8) on the stationary scroll (2) is formed, wherein the great volume of the pocket(30B) and one intake port of the suction port(8) led to accomplish the intended features. As in FIGS. 3 through 5, an oilless scroll-type compressor was provided which comprised: an orbiting scroll(1) provided with a pair of orbiting wraps(15A, 15B) at both surfaces axially parallel to a main shaft(5) having a crank portion(5a) supporting the orbiting scroll(1), a pair of stationary scroll(2A, 2B) formed with a stationary wrap(10) inside thereof mated with the orbiting wraps(15A, 15B) respectively, and three sets of slave crank shaft(6) for restriction of rotational movement were disposed in a 120 degree apart at outer walls(14, 24) to enclose an outer scroll room, wherein the slave crank shaft(6) connected the orbiting scroll(1) and one stationary scroll(2A) among the scrolls(2A, 2B). The stationary scrolls(2A, 2B) formed in a circular cap having outer walls(24, 24) disposed oppositely interfitted with a sealing member(29) to form a casing for sealed space therein, and a center axis hole with a main shaft(5) supported rotatably through bearings(25, 66) Stationary wraps(10, 10) formed in spiral involute were symmetrically disposed oppositely around the bearings(25, 66). The stationary scroll(2A) among the scrolls was provided with a suction port(8) at the peripheral wall(24) and a exhaust port(7A) at the central portion. On the other hand as mentioned in the earlier statement, the orbiting scroll(1) was axially parallelly provided with orbiting wraps(15A, 15B) on either surface thereof, wherein the orbiting wraps(15A, 15B) mated with the stationary wraps (10, 10). The orbiting scroll (1) was also axially supported with three axes(61), each one on a side shaft of a slave crank shaft (6). The slave crank axes(6, 6, 6), as known in the prior art, were axially disposed in a 120 degree distribution for arranging three of them at a circumferential distance from the center axis of the main shaft (5), one side axis (61, 61, 61) being axially disposed at the orbiting scroll(1), and other side axes(60, 60, 60) being axially disposed at the stationary scroll(2A) through bearings (63, 64). As the main shaft(5) was rotationally driven, the slave crank axes(6, 6, 6) rotated following the rotation of the main shaft(5) with an orbital radius(x) corresponding an eccentricity distance(x) of the main shaft(5). Thus, the slave orbiting axes(6, 6, 6) enabled the orbiting scroll(1) not to rotate on the stationary scroll axis(2a), but to orbit with the radius(x) around the axis(2a). The constitution of the slave orbiting axes is known in the art further description of which will be discontinued. The feature of the example resided in the constitution, as in FIG. 3, to axially dispose the only one side of the axes(6, 6, 6) at the one(2A) of the stationary scrolls(2), whereby a slight axial misalignment of the orbiting scroll (1) was absorbed to prevent the axial power from a useless increase. When the slave orbiting axis(6) was axially supported at both extensions with the stationary scrolls(2A, 2B) interfitting the orbiting scroll(1) therebetween, there arose an unfavorable problem to increase the axial power to drive due to the axial misalignment of the orbiting scroll(1), which would not be absorbed, to result finally in a solid construction. Referring the FIGS. 4 and 5, the constitution of the bearing portion for the axis(5) and axis(6) will be described hereinafter. A bearing(65) holding a central eccentric shaft(5a) of the main shaft(5), comprised a conventional needle bearing(65a) consisted of a number of needle bearings(65al) enclosed within a casing(65a2), and a pair of oilseals(65b) arranged at either ends thereof, wherein the space between the oilseals(65b, 65b) was filled with grease. Other side of bearing(66), as in FIG. 3, holding the main shaft(5) at the stationary scroll(2A), comprised an angular bearing(66b), a needle bearing(66a) enclosed in a casing, and an oilseal(66c) as in FIG. 4, wherein the sealed space was filled with grease. As in FIG. 5, a bearing(64) holding other side of the slave orbiting axis(60) comprised a pair of sealing angular bearings(64a, 64b), wherein the sealed space between thereof was filled with grease as well. In the constitution above, because the needle bearings(63a) for the slave orbiting axes(61) of the one side of the axes(6), and the needle bearings(65a, 66a) for the eccentric shaft(5a) and the main shaft(5) were formed having a slight axial play within the casings(65a2, ...) thereof, the play allowed the orbiting scroll(1) to move axially. A square groove(90) along the spiral involute, as in FIG. 3, was provide in the middle of every end surface (101, 151) which opposed the mirror surfaces(11a, 21a) of opposed scroll grooves(11, 21), wherein each one of strings of plastic seal member(9) made of a self-lubricant plastic material was disposed in every square groove (90) to be resiliently in contact with the mirror surfaces(11a) on both side of the orbiting scroll (1) and the mirror surfaces(21a) inside of the stationary scrolls(2A, 2B). As shown in FIG. 5, the projection length(H) of the wraps was formed slightly shorter than the distance(L) between the mirror surfaces(11a, 21a) of the scrolls(1, 2A, 2B), and the wall thickness(R1) of the orbiting scroll and the width(R2 as in FIG. 4) of the eccentric shaft(5a) were also formed slightly shorter than the distance(M) between the wrap ends(101) of the stationary scroll(2A, 2B). In other words, apertures assured the axial slide movement of the orbiting scroll, and also enabled the resilient interfitting, that is, the apertures between the scroll grooves(11a) of the orbiting scroll(1) and the scroll ends(101) of the stationary scrolls(2A, 2B), and the apertures between the scroll ends(151) and the scroll grooves(21a, 22a) of the stationary scrolls(2A, 2B). In such constitution of the example above, the resilient thrust forces of the sealing members(9) effected the self-alignment even if the orbiting scroll(1) had or caused to be in misalignment in the manner tilted or shifted with respect to other members. In a constitution of an example wherein three sets of slave orbiting axes(6) were rotatably disposed with stationary scrolls (2A, 2B) interfitted with an orbiting scroll therebetween, in which the both ends of the slave orbiting axes(6) were supported therewith, the axis power increased due to the tilting and shifting of the orbiting scroll (1), which misalignment was not tolerable, and made it rigid joining. The failure urged to the constitution as shown in FIG. 5, wherein the slave orbiting axes(6) were rotatably disposed on only one side of the scrolls, i.e. on the stationary scroll(2A), which led to absorb the tilting and shifting misalignment, to save the useless increase of the axis power. Further to the constitution of the sealing members(9) made of a resilient plastic material, another constitution as shown in FIG. 3(b) has also confirmed to show the same performance, a resilient thrust force having been enforced with a resilient member(91) disposed in the seal groove(90) together with a seal member(9).

Claims: A scroll-type fluid machine comprising: a stationary scroll (2) with an involute wrap (10) defining a scroll groove (21) with an inner dead end formed by a dead end wall (21a), and an orbiting scroll (1) with an axially projecting involute wrap (15), wherein the wrap (15) of the orbiting scroll engages the wrap (10) of the stationary scroll with corresponding turns engaged with a 180° phase difference, wherein one of the wraps (10, 15) is longer by half a turn outwardly than the other wrap so that the outer ends of the wraps are nearly in contact at a phase during the orbital movement of the orbiting scroll, and wherein the stationary scroll (2) comprises a bank (4) having a central axis hole for receiving a main shaft (5) driving the orbiting scroll, and having an exhaust port (7) at the rear side of the dead end wall (21a) which exhaust port is connected with the scroll groove by a passage (31) through the dead end wall. The machine of claim 1, wherein the orbiting scroll (1) has axially projecting wraps (15A, 15B) on opposite sides thereof and is disposed between a pair of stationary scrolls (2A, 2B) with inwardly extending wraps (10).

Inventors: HAGA SHUJI, TANUMA MASATOMO, HAGA, SHUJI, TANUMA, MASATOMO
Applicants: ANEST IWATA CORP, ANEST IWATA CORPORATION
Application year: 1991
Main classification: F04C18
IPC codes: F01C1, F01C19