BACKGROUND
1. Field
[0001] The present invention relates to a motor pump.
2. Description of the Related Art
[0002] Conventionally, there is a headlamp cleaner having a part moved to be taken in and
out from an opening formed on a vehicle body or on a bumper to thereby clean a front
cover of a vehicle headlamp.
[0003] The headlamp cleaner includes a spray nozzle for ejecting cleaning liquid, and a
cylinder having a supply pipe. Cleaning liquid supplied to the cylinder through the
supply pipe is ejected from the spray nozzle toward the front cover of the vehicle
headlamp to thereby clean the front cover.
[0004] Cleaning liquid is supplied to the cylinder by a motor pump. A drive motor having
a drive shaft is disposed inside the motor pump. A suction pipe as a suction path
for suctioning the cleaning liquid and an ejection pipe as a ejection path for feeding
the suctioned cleaning liquid are provided in the motor pump. The suction pipe is
connected to a tank while the ejection pipe is connected to the supply pipe of the
cylinder by a hose.
[0005] An impeller for performing suction and discharge of cleaning liquid is rotatably
supported inside the motor pump. While cleaning liquid is suctioned from the tank
into the motor pump, the cleaning liquid is fed from the motor pump to the cylinder
in accordance with rotation of the impeller.
[0006] In the motor pump of the type described in the above, the impeller has a bearing
portion connected to the drive shaft of the drive motor, and blade portions protruding
from an outer circumferential surface of the bearing portion. An example of such configuration
is disclosed in
JP-A-2006-299898.
[0007] In the configuration disclosed in
JP-A-2006-299898, each of the blade portions provided in the impeller of the motor pump is shaped
to have a curve which is displaced gradually between a direction of rotation of the
impeller and a direction opposite thereto in a range of from the bearing portion to
a tip of the blade portion.
[0008] In the motor pump disclosed in
JP-A-2006-299898, the pressure of each blade portion for pressing cleaning liquid to the ejection
pipe side may become so low that liquid pressure for feeding the cleaning liquid may
hardly be kept high, since each blade portion of the impeller is shaped to have a
curve which is displaced gradually between a direction of rotation of the impeller
and a direction opposite thereto in a range of from the bearing portion to the tip
as described above.
[0009] US 2005/0191176 A1, considered as the closest prior art, relates to a rotor wherein there are at least
three blades disposed between a front cover plate and a rear cover plate, the arc
of the suction edge of at least one blade in the top view of the inlet side of the
pumping medium following a sinusoidal path with a single turning point.
[0010] DE 92 06 053 U1 relates an impeller for a pump, in particular for use in a dishwasher.
[0011] WO 2004/046558 A1 relates to a centrifugal pump with an impeller which is rotatable in a direction
of rotation in a pump housing.
[0012] Moreover, because the liquid pressure may hardly be kept high, there is also a disadvantage
that the volume per unit time of cleaning liquid fed to the cleaner is small.
SUMMARY
[0013] One of objects of the present invention is to provide a motor lamp for a headlamp
cleaner capable to increase flow rate of cleaning liquid and to improve liquid pressure
for feeding the cleaning liquid.
[0014] According to an aspect of the invention, there is provided a motor pump including:
a case having a cavity having an inner circumferential surface, the cavity being configured
to temporary store liquid being suctioned therein; a suction pipe provided to serve
as a suction path for suctioning the liquid into the cavity, the suction pipe having
one end being provided with an inlet and the other end communicating with the cavity;
an ejection pipe provided to serve as an ejection path for ejecting the liquid from
the cavity, the ejection pipe having one end being provided with an outlet and the
other end communicating with the cavity; a drive motor disposed inside the case, the
drive motor having a drive shaft; and an impeller fixed to the drive shaft to be rotated
inside the cavity and the suction pipe to suction and eject the liquid, wherein the
impeller includes a bearing portion configured to be fixed to the drive shaft and
blade portions protruding in radial direction from the bearing portion, wherein each
of the blade portions includes a base portion formed to continue from the bearing
portion and a tip portion formed to continue from the base portion, wherein the base
portion of each of the blade portions is formed to be convexly curved toward a rotational
direction of the impeller, and wherein the tip portion of each of the blade portions
is formed to be convexly curved toward a backward direction opposite the rotational
direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A general configuration that implements the various feature of the invention will
be described with reference to the drawings. The drawings and the associated descriptions
are provided to illustrate embodiments of the invention and not to limit the scope
of the invention.
Fig. 1 is a perspective view of a motor pump showing an example of a motor pump of
a headlamp cleaner according to the invention.
Fig. 2 is a sectional view of the motor pump.
Fig. 3 is an enlarged sectional view taken along the III-III line shown in Fig. 2.
Fig. 4 is an enlarged perspective view of an impeller.
Fig. 5 is a schematic view showing the shape of each blade portion in the impeller.
DETAILED DESCRIPTION OF THE EMBODIMENT(S)
[0016] An embodiment according to the present invention will be described in detail with
reference to the accompanying drawings. The scope of the claimed invention should
not be limited to the examples illustrated in the drawings and those described below.
[0017] As shown in Figs. 1 and 2, a motor pump 1 has a case 2 and other components disposed
inside the case 2.
[0018] The case 2 is configured by an upper-half case 3 and a lower-half case 4 which are
combined vertically.
[0019] The upper-half case 3 is opened downward and has a cylindrical wall 5 having a cylindrical
shape, and a top wall 6 formed to be continued from an upper edge of the cylindrical
wall 5 so as to cover one end of the cylindrical wall 5.
[0020] The cylindrical wall 5 has a fitting groove 5a and a fitting protrusion 5b which
are formed vertically and continuously so as to be located near a lower end of the
cylindrical wall 5.
[0021] The top wall 6 is integrally provided with a connector portion 7 which protrudes
upward from an upper surface of the top wall 6. A connection terminal 7a is disposed
inside the connector portion 7. A not-shown power connector for supplying electric
power to a drive motor, which will be described later, is connected to the connection
terminal 7a.
[0022] The lower-half case 4 is opened upward and has a cylindrical wall 8 formed to have
a cylindrical shape, and a top wall 9 formed to be continued from a lower end portion
of the cylindrical wall 8 so as to cover the lower end portion of the cylindrical
wall 8.
[0023] The cylindrical wall 8 has a fitting protrusion 8a and a fitting groove 8b which
are formed vertically and continuously so as to be located near an upper end of the
cylindrical wall 8. The cylindrical wall 8 is integrally provided with an ejection
pipe 10 which protrudes laterally from a lower end portion of the cylindrical wall
8. The ejection pipe 10 has one end (tip) at which an outlet 10a is formed, and the
other end which communicates with a cavity (which will be described later) formed
inside the case 2.
[0024] The top wall 9 is integrally provided with a suction pipe 11 which protrudes downward
from a center portion of the top wall 9. The suction pipe 11 has one end (lower end)
at which an inlet 11a is formed, and the other end which communicates with the cavity
formed inside the case 2.
[0025] As shown in Fig. 2, the upper-half case 3 and the lower-half case 4 are combined
with each other to form the case 2 in such a manner that the fitting protrusion 8a
is fitted into the fitting groove 5a while the fitting protrusion 5b is fitted into
the fitting groove 8b.
[0026] A spacer 12 is disposed inside the lower-half case 4 so as to be fitted to the lower-half
case 4. A shaft insertion hole 12a is formed in a center portion of the spacer 12
so as to pierce the spacer 12 vertically. Because the spacer 12 is disposed inside
the lower-half case 4, an upper space 13 and a lower space 14 are formed as upper
and lower parts respectively inside the case 2.
[0027] A drive motor 15 is disposed in the upper space 13. The drive motor 15 is configured
by drive coils and drive magnets. The drive motor 15 has a drive shaft 15a which is
formed in a center portion of the drive motor 15 so as to extend vertically. A part
of the drive shaft 15a protrudes downward.
[0028] A rubber bush 16 is disposed in the lower space 14 so as to be located under the
spacer 12. The rubber bush 16 is fitted inside the lower-half case 4 and has a shaft
support hole 16a which is disposed in a center portion of the rubber bush 16 so as
to pierce the rubber bush 16 vertically. The rubber bush 16 has a function of preventing
cleaning liquid (which will be described later) from leaching out from the lower space
14 into the upper space 13.
[0029] The downward protruding part of the drive shaft 15a of the drive motor 15 is formed
as follows. The drive shaft 15a is inserted into the shaft insertion hole 12a of the
spacer 12 and passes through the shaft support hole 16a of the rubber bush 16 so as
to be supported by the shaft support hole 16a of the rubber bush 16. As a result,
a lower end portion of the drive shaft 15a protrudes downward from the rubber bush
16.
[0030] A portion of the lower case space 14 which is surrounded by an inner circumferential
surface 8c of the cylindrical wall 8, a lower surface of the rubber bush 16 and an
inner surface of the top wall 9 in the lower-half case 4 is formed as a cavity 14a
in which cleaning liquid can be stored temporarily. The other end of the ejection
pipe 10 and the other end of the suction pipe 11 communicate with the cavity 14a.
[0031] An impeller 17 is disposed inside the cavity 14a and the suction pipe 11 so as to
be supported rotatably (see Figs. 2 and 3). As shown in Figs, 2 to 4, the impeller
17 is formed in such a manner that a bearing portion 18 is integrated with blade portions
19, 19 and 19 protruding in radial direction from the bearing portion 18.
[0032] A fixing hole 18a opened upward is formed in the bearing portion 18.
[0033] The blade portions 19, 19 and 19 are provided and positioned at regular intervals
in a circumferential direction around the bearing portion 18. Each of the blade portions
19, 19 and 19 is configured by a suction blade 20 protruding downward from the bearing
portion 18 and a feed blade 21 protruding laterally from the bearing portion 18.
[0034] Each feed blade 21 is configured by a base portion 21a continued to the bearing portion
18 and a tip portion 21b continued to the base portion 21a. The length of each base
portion 21a in a laterally extending direction is set to be larger than that of a
corresponding tip portion 21b.
[0035] As shown in Figs. 3 and 5, each base portion 21a is shaped to have a gentle curve
such as a substantially circular arc which is convexly curved toward a direction of
rotation of the impeller 17 (a direction P1 shown in Figs. 3 to 5). As shown in Figs.
3 and 5, each tip portion 21b is shaped to have a gentle curve such as a substantially
circular arc which is convexly curved toward a direction opposite to the direction
P1 of rotation of the impeller 17.
[0036] In the impeller 17, the base portions 21a, 21a and 21a are shaped like circular arcs
so that three reference lines T, T and T radiating at regular intervals from a center
M of the bearing portion 18 are tangential to extensions Q, Q and Q of the base portions
21a, 21a and 21a at the center M. Accordingly, cleaning liquid can be prevented from
staying stagnantly in the vicinity of bearing portion 18-side end portions of the
base portions 21a, 21a and 21a, so that improvement in fluidity of cleaning liquid
can be improved.
[0037] The impeller 17 is fixed in such a manner that a lower end portion of the drive shaft
15a of the drive motor 15 is inserted into the fixing hole 18a of the bearing portion
18. The bearing portion 18 and the feed blades 21, 21 and 21 are disposed in the cavity
14a while the suction blades 20, 20 and 20 are disposed inside the suction pipe 11.
Accordingly, the impeller 17 is rotated inside the cavity 14a and the suction pipe
11 by driving force of the drive motor 15.
[0038] In a state that the impeller 17 is disposed inside the cavity 14a and the suction
pipe 11, respective tips (outer ends) of the feed blades 21, 21 and 21 are located
near the inner circumferential surface 8c of the lower-half case 4 forming the cavity
14a (see Fig. 3) while respective tips (outer ends) of the suction blades 20, 20 and
20 are located so that a predetermined gap is formed between the tip of each suction
blade 20 and the inner surface of the suction pipe 11.
[0039] As shown in Fig. 3, the ejection pipe 10 is provided so that an axial direction of
the ejection pipe 10 coincides with a direction tangential to the inner circumferential
surface 8c, and that an outermost portion 10b of the inner surface of the ejection
pipe 10 farthest from the center of rotation of the impeller 17 coincides with a line
(S in Fig. 3) tangential to the inner circumferential surface 8c.
[0040] In the motor pump 1 configured as described above, when the drive motor 15 is rotated,
the impeller 17 is rotated by driving force of the drive motor 15. When the impeller
17 is rotated, cleaning liquid is suctioned from a not-shown tank into the cavity
14a through the suction pipe 11 by the suction blades 20, 20 and 20 so that the suctioned
cleaning liquid is fed to a not-shown cylinder of the headlamp cleaner through the
ejection pipe 10 by the feed blades 21, 21 and 21. The cleaning liquid fed to the
cylinder is ejected from a spray nozzle of the headlamp cleaner toward a front cover
of a vehicle headlamp, so that the front cover is cleaned.
[0041] When cleaning liquid is fed from the cavity 14a toward the ejection pipe 10 in accordance
with rotation of the impeller 17, cleaning liquid temporarily stored in the cavity
14a is forced out into the inside of the ejection pipe 10 by the feed blades 21, 21
and 21 rotating in the cavity 14a.
[0042] On this occasion, because the base portion 21a of each feed blade 21 is shaped to
have a gentle curve which is convexly curved toward the direction of rotation of the
impeller 17 as described above, flow resistance is so low that cleaning liquid can
flow easily from the bearing portion 18 side to the tip portion 21b side, and that
the flow rate of cleaning liquid increases as the cleaning liquid moves from the base
portion 21a side to the tip portion 21b side.
[0043] Moreover, because the tip portion 21b of each feed blade 21 is shaped to have a gentle
curve which is convexly curved toward a direction opposite to the direction of rotation
of the impeller 17, the direction of a rotation-direction side surface 21c (see Fig.
3) of each tip portion 21b approaches a tangential line in the direction of rotation
compared with the direction of a rotation-direction side surface of a corresponding
base portion 21a. Accordingly, increase in flow rate of cleaning liquid and improvement
in liquid pressure for feeding the cleaning liquid can be attained.
[0044] Moreover, because the tip portion 21b of each feed blade 21 is shaped to have a gentle
curve which is convexly curved toward a direction opposite to the direction of rotation
of the impeller 17, eddy currents of cleaning liquid which has flown from the base
portion 21a side to the tip portion 21b side are adjusted so that velocity energy
is efficiently converted into pressure energy in the vicinity of the tip portions
21b, 21b and 21b. Accordingly, increase in flow rate of cleaning liquid and improvement
in liquid pressure for feeding the cleaning liquid can be attained.
[0045] Moreover, since the motor pump 1 is formed so that the respective tips of the feed
blades 21, 21 and 21 in the impeller 17 are located near the inner circumferential
surface 8c of the lower-half case 4 forming the cavity 14a, greater increase in flow
rate of cleaning liquid in accordance with improvement in liquid pressure for feeding
the cleaning liquid can be attained.
[0046] In addition, the motor pump 1 is formed so that the axial direction of the ejection
pipe 10 coincides with a direction tangential to the inner circumferential surface
8c and that the portion 10b of the ejection pipe 10 coincides with a line tangential
to the inner circumferential surface 8c. Accordingly, increase in flow rate of cleaning
liquid and improvement in efficiency of liquid feeding operation can be attained.
[0047] The motor pump 1 is formed so that the impeller 17 is configured by three blade portions
19, 19 and 19. Because the number of the blade portions 19 is reduced to three as
described above, resistance of cleaning liquid to the rotating impeller 17 can be
reduced so that the load imposed on the drive motor 15 can be reduced.
[0048] Since the number of the blade portions 19 is reduced to three, the volume of cleaning
liquid in the cavity 14a can be increased.
[0049] However, the number of the blade portions 19 used in the impeller 17 of the motor
pump 1 may not be limited to three. The number of the blade portions 19 may be chosen
in accordance with a desired pump design.
[0050] In the above description, it is assumed that the motor pump 1 is used for a headlamp
cleaner for ejecting the cleaning liquid to the headlamp of a vehicle. However, the
motor pump 1 may be widely used for variety of vehicle lamps including the headlamp
or may be widely used for window washer unit for ejecting the cleaning liquid toward
a windshield of a vehicle.
[0051] Although the embodiment according to the present invention have been described above,
the present invention is not limited to the above-mentioned embodiment but can be
variously modified. Constituent components disclosed in the aforementioned embodiment
may be combined suitably to form various modifications. For example, some of all constituent
components disclosed in the embodiment may be removed or may be appropriately combined.
[0052] Additional advantages and modifications will readily occur to those skilled in the
art. Therefore, the invention in its broader aspects is not limited to the specific
details and representative embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or scope of the general
inventive concept as defined by the appended claims and their equivalents.
1. A motor pump (1) comprising:
a case (2) having a cavity (14a) having an inner circumferential surface (8c), the
cavity (14a) being configured to temporary store liquid being suctioned therein;
a suction pipe (11) provided to serve as a suction path for suctioning the liquid
into the cavity (14a), the suction pipe (11) having one end being provided with an
inlet (11a) and the other end communicating with the cavity (14a);
an ejection pipe (10) provided to serve as an ejection path for ejecting the liquid
from the cavity (14a), the ejection pipe (10) having one end being provided with an
outlet (10a) and the other end communicating with the cavity (14a);
a drive motor (15) disposed inside the case (2), the drive motor (15) having a drive
shaft (15a); and
an impeller (17) fixed to the drive shaft (15a) to be rotated inside the cavity (14a)
and the suction pipe (11) to suction and eject the liquid,
wherein the impeller (17) comprises a bearing portion (18) configured to be fixed
to the drive shaft (15a) and blade portions (19) protruding in radial direction from
the bearing portion (18),
wherein each of the blade portions (19) comprises a base portion (21a) formed to continue
from the bearing portion (18) and a tip portion (21b) formed to continue from the
base portion (21a),
wherein the base portion (21a) of each of the blade portions (19) is formed to be
convexly curved toward a rotational direction of the impeller (17), characterized in that
the tip portion (21b) of each of the blade portions (19)is formed to be convexly curved
toward a backward direction opposite the rotational direction.
2. The motor pump (1) according to Claim 1,
wherein the impeller (17) is formed to have the tip portion (21b) of each of the blade
portions (19) being set to rotate near the inner circumferential surface (8c) of the
cavity (14a).
3. The motor pump (1) according to one of Claims 1 and 2,
wherein an axial direction of the ejection pipe (10) is set to coincide with a tangential
direction of the inner circumferential surface (8c) of the cavity (14a).
4. The motor pump (1) according to one of claims 1 to 3,
wherein the cavity (14a) is formed to be surrounded by a cylindrical wall having the
inner circumferential surface (8c).
5. The motor pump (1) according to one of claims 1 to 4,
wherein the impeller (17) comprises three pieces of the blade portions (19).
1. Motorpumpe (1) mit:
einem Gehäuse (2), das eine Kavität (14a) mit einer inneren Umfangsoberfläche (8c)
aufweist, wobei die Kavität (14a) ausgestaltet ist, zeitweise darin eingesaugte Flüssigkeit
aufzunehmen;
einem Ansaugrohr (11), das vorgesehen ist, um als Ansaugpfad zum Einsaugen der Flüssigkeit
in die Kavität (14a) zu fungieren, wobei das Ansaugrohr (11) ein Ende aufweist, an
dem ein Einlauf (11a) vorgesehen ist, und das andere Ende in Verbindung mit der Kavität
(14a) steht;
einem Ausstoßrohr (10), das vorgesehen ist, um als Ausstoßpfad zum Ausstoßen der Flüssigkeit
aus der Kavität (14a) zu fungieren, wobei das Ausstoßrohr (10) ein Ende aufweist,
an dem ein Auslauf (10a) vorgesehen ist, und das andere Ende in Verbindung mit der
Kavität (14a) steht;
einem Antriebsmotor (15), der innerhalb des Gehäuses (2) angeordnet ist, wobei der
Antriebsmotor (15) eine Antriebswelle (15a) aufweist; und
einem Laufrad (17), das an der Antriebswelle (15a) befestigt ist, um innerhalb der
Kavität (14a) und dem Ansaugrohr (11) zum Ansaugen und Ausstoßen der Flüssigkeit rotiert
zu werden,
wobei das Laufrad (17) einen Lagerbereich (18), der ausgestaltet ist, an der Antriebswelle
(15a) befestigt zu werden, und Schaufelbereiche (19), die in radialer Richtung von
dem Lagerbereich (18) hervorstehen, aufweist,
wobei jeder der Schaufelbereiche (19) einen Basisbereich (21a), der ausgebildet ist,
von dem Lagerbereich (18) zu verlaufen und einen Spitzenbereich (21b), der ausgebildet
ist, von dem Basisbereich (21a) zu verlaufen, aufweist,
wobei der Basisbereich (21a) von jedem der Schaufelbereiche (19) ausgebildet ist,
konvex in eine Drehrichtung des Schaufelrades (17) gekrümmt zu sein,
dadurch gekennzeichnet, dass
der Spitzenbereich (21b) von jedem der Schaufelbereiche (19) ausgebildet ist, konvex
in eine Rückwärtsrichtung entgegengesetzt der Drehrichtung gekrümmt zu sein.
2. Motorpumpe (1) nach Anspruch 1, bei der das Schaufelrad (17) ausgebildet ist, den
Spitzenbereich (21b) von jedem der Schaufelbereiche (19) so angeordnet zu haben, dass
dieser sich in der Nähe der inneren Umfangsoberfläche (8c) der Kavität (14a) dreht.
3. Motorpumpe (1) nach einem der Ansprüche 1 und 2, bei der eine Axialrichtung des Ausstoßrohres
(10) angeordnet ist, sich mit einer Tangentialrichtung der inneren Umfangsoberfläche
(8c) der Kavität (14a) zu decken.
4. Motorpumpe (1) nach einem der Ansprüche 1 bis 3, bei der die Kavität (14a) ausgebildet
ist, von einer Zylinderwand mit der inneren Umfangsoberfläche (8c) umgeben zu sein.
5. Motorpumpe (1) nach einem der Ansprüche 1 bis 4, bei der das Schaufelrad (17) drei
Teile der Schaufelbereiche (19) umfasst.
1. Pompe de moteur (1) comprenant :
un carter (2) comportant une cavité (14a) ayant une surface circonférentielle intérieure
(8c), la cavité (14a) étant configurée pour stocker temporairement un liquide aspiré
dedans ;
un tuyau d'aspiration (11) fourni pour servir de chemin d'aspiration pour aspirer
le liquide dans la cavité (14a), le tuyau d'aspiration (11) ayant une extrémité pourvue
d'un orifice d'entrée (11a) et l'autre extrémité communiquant avec la cavité (14a)
;
un tuyau de refoulement (10) fourni pour servir de chemin de refoulement pour refouler
le liquide de la cavité (14a), le tuyau de refoulement (10) ayant une extrémité pourvue
d'un orifice de sortie (10a) et l'autre extrémité communiquant avec la cavité (14a)
;
un moteur d'entraînement (15) disposé à l'intérieur du carter (2), le moteur d'entraînement
(15) comportant un arbre d'entraînement (15a) ; et
un impulseur (17) fixé sur l'arbre d'entraînement (15a) pour être mis en rotation
à l'intérieur de la cavité (14a) et du tuyau d'aspiration (11) pour aspirer et refouler
le liquide,
dans lequel l'impulseur (17) comprend une partie de moyeu (18) configurée pour être
fixée sur l'arbre d'entraînement (15a) et des parties de pale (19) faisant saillie
dans une direction radiale depuis la partie de moyeu (18),
dans lequel chacune des parties de pale (19) comprend une partie de base (21a) formée
pour continuer depuis la partie de moyeu (18) et une partie d'extrémité (21b) formée
pour continuer depuis la partie de base (21a),
dans lequel la partie de base (21a) de chacune des parties de pale (19) est formée
pour être courbée de manière convexe vers une direction de rotation de l'impulseur
(17),
caractérisé en ce que
la partie d'extrémité (21b) de chacune des parties de pale (19) est formée pour être
courbée de manière convexe vers une direction vers l'arrière opposée à la direction
de rotation.
2. Pompe de moteur (1) selon la revendication 1,
dans laquelle l'impulseur (17) est formé pour avoir la partie d'extrémité (21b) de
chacune des parties de pale (19) réglée pour tourner près de la surface circonférentielle
intérieure (8c) de la cavité (14a).
3. Pompe de moteur (1) selon l'une des revendications 1 et 2,
dans laquelle une direction axiale du tuyau de refoulement (10) est réglée pour coïncider
avec une direction tangentielle de la surface circonférentielle intérieure (8c) de
la cavité (14a).
4. Pompe de moteur (1) selon l'une des revendications 1 à 3,
dans laquelle la cavité (14a) est formée pour être entourée par une paroi cylindrique
comportant la surface circonférentielle intérieure (8c).
5. Pompe de moteur (1) selon l'une des revendications 1 à 4,
dans laquelle l'impulseur (17) comprend trois des parties de pale (19).