[Technical Field]
[0001] The present invention relates to an impeller that is used for a liquid pump.
[Background Art]
[0003] A general liquid pump that pumps a liquid by rotating a disclike impeller using
a motor is known. As a conventional technology with regard to an impeller used in
such a liquid pump, there is the technology disclosed in Patent Literature 1.
[0004] An impeller such as that disclosed in Patent Literature 1 has a plurality of blades
provided in a circumferential direction and blade grooves formed in regions sandwiched
between the blades. In a case where the angle formed by a line segment connecting
the center of an arbitrary blade to the rotation center of the impeller and a line
segment connecting the center of a blade adjacent to the arbitrary blade to the rotation
center of the impeller is set to a pitch angle of the blades, the blades are disposed
to have pitch angles of different values. In addition, the blade grooves are disposed
at different pitch angles.
[0005] By irregularly disposing the blade grooves at different pitch angles around the entire
circumference of the impeller, the peak of sound pressure resulting from rotation
of the impeller can be reduced. As a result, noise made by the liquid pump can be
reduced.
[Citation List]
[Patent Literature]
[0006] [Patent Literature 1]
Japanese Patent Application, Publication No.
H1150990
[Summary of Invention]
[Technical Problem]
[0007] It can be seen from Patent Literature 1 that it is better to give all of the blade
grooves different pitch angles in order to reduce noise. Meanwhile, it is also known
that pump efficiency of a liquid pump is the highest when the blade grooves are arranged
at equal pitches.
[0008] The present invention aims to provide an impeller that can reduce noise while ensuring
pump efficiency of a liquid pump.
[Solution to Problem]
[0009] According to an aspect of the present invention, there is provided an impeller in
substantially a disc shape that is used in a liquid pump for pressurefeeding a liquid
by being rotated by a drive source including i blades provided in a circumferential
direction and i blade grooves formed in regions sandwiched by the blades, in which
an angle formed by a line segment connecting the center of an nth (n is an integer
from 1 to i) blade to a rotation center of the impeller and a line segment connecting
the center of an (n+1)th blade (however, the 1
^{st} blade when n=i) to the rotation center of the impeller is set as a pitch angle θn
of an nth blade groove, the blade grooves are continuous from the 1
^{st} blade groove and constitute each of m blade groove groups, m satisfying m≥5, (however,
in a case where i/m is not an integer, a blade groove group including the ith blade
groove is constituted by the remaining number of blade grooves which is less than
m), the pitch angle θn is set to a value different from the pitch angles of the other
blade grooves constituting the one blade groove group, in a case where a lowest pitch
angle in the one blade groove group is set as θmin and a highest pitch angle is set
as θmax, θmaxθmin≤5°, and values from θmin to θmax are set to have equal differences,
the sum of pitch angles from the nth blade groove having the pitch angle θn to the
blade groove before a kth blade groove having a pitch angle θk which is the same
value to the next in the circumferential direction is set as an integrated pitch angle
tn, and among a 1
^{st} integrated pitch angle t
_{1} to an ith integrated pitch angle t
_{i}, the number of integrated pitch angles having one value is two or less, and the number
of sets having the same value does not exceed i×0.18.
[0010] According to the abovedescribed aspect, in the case where the number of sets having
the same values is two or more, when the 1
^{st} integrated pitch angle t
_{1} to the ith integrated pitch angle t
_{i} are arranged in order from the lower angles, at least one integrated pitch angle
not having the same value is preferably set between the sets having the same values.
[0011] According to the abovedescribed aspect, in the case where the number of sets having
the same values is two or more, the difference in angle between the sets having the
same values is preferably greater than 1°.
[0012] According to the abovedescribed aspect, θmin is preferably set to 9° or higher and
θmax is preferably set to 13° or lower.
[0013] According to another aspect of the present invention, an impeller for a liquid pump
includes a disc; i blades disposed on the disc in a circumferential direction; and
i grooves provided on the disc, each of which is sandwiched between the blades, in
which the following requirements are satisfied: (i) the grooves are divided into a
plurality of groups, each of the groups is constituted by m (m≥5) grooves arranged
in series (however, in a case where i/m is not an integer, one group is constituted
by the remaining number (1, 2, 3, or 4) of grooves; (ii) in each group, the values
of pitch angles are different; (iii) in each group, the series of the values of pitch
angles arranged in ascending order have the relationship of equal differences; (iv)
in each group, θmaxθmin≤5°; (v) an integrated pitch angle has a single value that
is different from those of the other integrated pitch angles or a value common for
a pair of two integrated pitch angles is different from those of the other integrated
pitch angles; and (vi) the number of pairs of integrated pitch angles having common
values does not exceed i×0.18, however, the angle formed by a line segment extending
between the center of an nth (n is an integer from 1 to i) blade and the center of
the disc and a line segment extending between the center of an (n+1)th blade (however,
the center of the 1st blade when n=i) and the center of the disc is set as an nth
pitch angle, the minimum value of the pitch angles is set as θmin and the maximum
value is set as θmax for each group, the next pitch angle to the nth pitch angle
is set as a kth pitch angle among pitch angles having the same value as the nth
pitch angle, and an angle obtained by integrating consecutive pitch angles from the
nth pitch angle to a (k1)th pitch angle is set as an integrated pitch angle.
[0014] According to the abovedescribed aspect, in the series of all integrated pitch angles
in ascending order, at least one integrated pitch angle having a single value may
be placed between a first pair of integrated pitch angles having a common value and
a second pair of integrated pitch angles having another common value.
[0015] For example, the difference in values between the first pair of integrated pitch
angles having the common value and the second pair of integrated pitch angles having
the other common value is greater than 1.
[0016] In addition, for example, θmin is 9° or higher and θmax is 13° or lower
[Advantageous Effects of Invention]
[0017] According to an aspect of the present invention, a pitch angle θn is set such that
all conditions that each pitch angle has a value different from the pitch angles of
the other blade grooves constituting one blade groove group, θmaxθmin≤5°, and all
values from θmin to θmax have equal differences are satisfied. By having a value different
from the pitch angles of the other blade grooves constituting the blade groove group,
noise can be suppressed. Meanwhile, under the conditions of θmaxθmin≤5° and the equal
differences between the values from θmin to θmax, the magnitude of irregularity in
pitch angles comes into a certain range, and pump efficiency is also ensured. The
blade grooves are divided into a plurality of groups, and thus pitch angles at which
noise can be reduced while pump efficiency of the liquid pump is ensured with respect
to each of the groups can be set.
[0018] Furthermore, there are only two or fewer integrated pitch angles having one value
among the 1
^{st} integrated pitch angle t
_{1} to the ith integrated pitch angle t
_{i}. Disposition of blade grooves having the same pitch angle at uniform intervals can
cause noise. By diminishing the part that causes noise, noise can be further reduced.
In addition, the number of sets having the same value does not exceed i×0.18 among
the 1
^{st} integrated pitch angle t
_{1} to the ith integrated pitch angle t
_{i}. It was found that, in the case where the number of sets does not exceed i×0.18,
particularly excellent noise reduction was exhibited. If there are a large number
of sets having the same value even though there are two or fewer integrated pitch
angles having one value, it is difficult to reduce noise. This means that by setting
the number of sets having the same value to i×0.18 or smaller, noise can be further
reduced.
[0019] According to the aspect of the present invention, the blade grooves having the same
pitch angle are prevented from being disposed at uniform intervals, focusing on the
integrated pitch angles. Thus, with respect to each of the blade groove groups and
the entire impeller, noise can be reduced while pump efficiency of the liquid pump
is ensured.
[0020] Furthermore, with respect to the integrated pitch angles tn, at least one integrated
pitch angle not having the same value is included between the sets having the same
values. If the value of the set having the same value is approximate to the value
of the set having the same value, there are many integrated pitch angles having approximate
values. By inserting the integrated pitch angles not having the same value, the values
of the sets having the same value are separated, and thus noise can be further reduced.
[0021] The difference in angle between the sets having the same values is greater than 1°.
If the values of the sets having the same values are approximate to each other, there
are many integrated pitch angles having approximate values. By setting the difference
in angle between the sets having the same values to be greater than 1°, the values
of the sets having the same values can be separated, and thus noise can be further
reduced.
[0022] θmin is 9° or higher and θmax is 13° or lower. It was found that that, by setting
the pitch angles of the blade grooves to come within the range, pump efficiency of
the liquid pump can be particularly ensured.
[Brief Description of Drawings]
[0023]
Fig. 1 is a cross sectional view of a fuel pump in which an impeller according to
an embodiment of the present invention is mounted.
Fig. 2 is a plan view of the impeller illustrated in Fig. 1.
[Description of Embodiments]
[0024] An embodiment of the present invention will be described with reference to the accompanying
drawings.
<Embodiment>
[0025] Fig. 1 will be referred to. An impeller 20 according to present invention is mounted
in, for example, a fuel pump 10 that is provided in a twowheeled vehicle. The fuel
pump 10 is used to pump a liquid fuel filled in a fuel tank and supply it to an engine.
The fuel pump 10 can also be called a liquid pump for pumping a liquid.
[0026] The fuel pump 10 has a motor (a drive source 11) that is driven by power from an
external power supply, the impeller 20 that is fixed to a motor shaft 11a of the motor
11, and a pump casing 30 that surrounds the impeller 20 as main constituent elements.
The motor 11, the impeller 20, and the pump casing 30 are housed in a housing 15.
The upper part of the housing 15 is covered by a lid member 16.
[0027] The pump casing 30 is constituted by a lower casing 31 that is disposed below the
impeller 20 and an upper casing 32 that covers the sides and upper part of the impeller
20 superimposed on the lower casing 31.
[0028] The lower casing 31 has a casing part intake port 31a penetrating the lower casing
to take in a liquid fuel from the outside.
[0029] The upper casing 32 has a casing part discharge port 32a penetrating the upper casing
to discharge a liquid fuel into the housing 15.
[0030] The lid member 16 has a lid part discharge port 16a penetrating the lid member to
discharge a liquid fuel to the outside. The lid part discharge port 16a includes a
check valve 17 with which the lid part discharge port 16a can be opened and closed.
[0031] When the motor 11 operates, the impeller 20 rotates together with the motor shaft
11a. Thereby, a liquid fuel is sucked up. The sucked liquid fuel is guided from the
casing part intake port 31a into the pump casing 30 and then discharged from the casing
part discharge port 32a into the housing 15. The liquid fuel that has passed through
the pump casing 30 causes the lid part discharge port 16a to be in an open state,
resisting an urging force of the check valve 17. The liquid fuel discharged from the
lid part discharge port 16a to the outside of the housing 15 is transported to the
engine. Details of the impeller 20 will be described using the next diagram.
[0032] Fig. 2 will be referred to. The impeller 20 has substantially a disc shape as an
example. The impeller 20 has a disc (base or body) 21, 33 blades from a blade P
_{1} to blade P
_{33} that are provided in the circumferential direction, and 33 blade grooves Q
_{1} to Q
_{33} that are formed in regions sandwiched by the blade P
_{1} to blade P
_{33}.
[0033] The impeller 20 can have i blades P that are provided in the circumferential direction
and i blade grooves Q that are formed in regions sandwiched by these blades P. Alternatively,
the impeller 20 has the disc 21, i blades P that are disposed in a ringlike region
on the disc 21 in the circumferential direction, and i grooves Q, each of which is
provided between the blades P in the ringlike region on the disc 21.
[0034] An arbitrarily selected blade P
_{1} is assumed to be the 1
^{st} blade P
_{1}, and those arranged clockwise from the first blade are assumed to be the 2
^{nd} blade P
_{2}, the 3
^{rd} blade P
_{3}, and so on. The impeller 20 has the first blade P
_{1} to the 33
^{rd} blade P
_{33}.
[0035] The blade groove Q
_{1} that is formed in the region sandwiched by the 1
^{st} blade P
_{1} and the 2
^{nd} blade P
_{2} (intermediate region) is assumed to be the 1
^{st} blade groove Q
_{1}. Likewise, the blade groove Q
_{2} that is formed in the region sandwiched by the 2
^{nd} blade P
_{2} and the 3
^{rd} blade P
_{3} is assumed to be the 2
^{nd} blade groove Q
_{2}. The blade groove Q
_{33} that is formed in the region sandwiched by the 33
^{rd} blade P
_{33} and the 1
^{st} blade P
_{1} is assumed to be the 33
^{rd} blade groove Q
_{33}. The impeller 20 has the 1
^{st} blade groove Q
_{1} to the 33
^{rd} blade groove Q
_{33}.
[0036] Note that the number of blades P and blade grooves Q is not limited to 33. In another
example, the impeller 20 can have a number of blades and blade grooves other than
33.
[0037] The angle formed by a line segment L1 connecting the center of the 1
^{st} blade P
_{1} to a rotation center CL of the impeller 20 and a line segment L2 connecting the center
of the 2
^{nd} blade P
_{2} to the rotation center CL of the impeller 20 is called a pitch angle θ
_{1} of the 1
^{st} blade groove. Likewise, the angle formed by a line segment L2 connecting the center
of the 2
^{nd} blade P
_{2} to the rotation center CL of the impeller 20 and a line segment L3 connecting the
center of the 3
^{rd} blade P
_{3} to the rotation center CL of the impeller 20 is called a pitch angle θ
_{2} of the 2
^{nd} blade groove. The angle formed by a line segment L33 connecting the center of the
33
^{rd} blade P
_{33} to the rotation center CL of the impeller 20 and the line segment L1 connecting the
center of the 1
^{st} blade P
_{1} to the rotation center CL of the impeller 20 is called a pitch angle θ
_{33} of the 33
^{rd} blade groove.
[0038] That is, the angle formed by each of the line segments L1 to L33 connecting the center
of an nth (n is an integer from 1 to i) blade P to the rotation center CL of the
impeller 20 and each of the line segments L2 to L33 and to L1 connecting the center
of an (n+1)th blade P (however, the 1
^{st} blade when n=i) to the rotation center CL of the impeller 20 can be assumed to be
a pitch angle θn of an nth blade groove. Alternatively, the angle formed by each
of the line segments L1 to L33 extending between the center of the nth (n is an integer
from 1 to i) blade P and the center of the disc 21 and each of the line segments L2
to L33 and to L1 extending from the center of the (n+1)th blade (however, the center
of the 1
^{st} blade P1 when n=i) and the center of the disc 21 can be assumed to be an nth pitch
angle.
[0039] The blade grooves Q
_{1} to Q
_{30} are continuous from the 1
^{st} blade groove Q
_{1} and constitute five blade groove groups R
_{1} to R
_{6}. The three blade grooves Q
_{31} to Q
_{33} constitute a blade groove group R
_{7}.
[0040] The 1
^{st} blade groove group R
_{1} is constituted by the 1
^{st} blade groove Q
_{1} to the 5
^{th} blade groove Q
_{5}. Likewise, the 2
^{nd} blade groove group R
_{2} is constituted by the 6
^{th} blade groove Q
_{6} to the 10
^{th} blade groove Q
_{10}.
[0041] The blade grooves Q are continuous from the 1
^{st} blade groove Q
_{1} and constitute m blade groove groups R
_{1} to R
_{7}, m satisfying m≥5. However, in a case where i/m is not an integer, the blade groove
group R
_{7} that includes the ith blade groove Q
_{33} is constituted by the remaining number of blade grooves which is less than m. Alternatively,
the grooves Q are grouped into multiple groups R
_{1} to R
_{7}. Each of the groups R
_{1} to R
_{7} is constituted by m (m≥5) grooves arranged in series. However, in the case where
i/m is not an integer, one group is constituted by the remaining number of grooves
(1, 2, 3, or 4).
[Table 1]
Example 1 
Example 2 
Blade groove groups 
Pitch angles 
Large pitch angles 
Large pitch angles arranged from lower angles 
Blade groove groups 
Pitch angles 
Large pitch angles 
Large pitch angles arranged from lower angles 
R_{n} 
θ_{n} 
° 
t_{n} 
° 
° 
t_{n} 
R_{n} 
θ_{n} 
° 
t_{n} 
° 
° 
t_{n} 
R_{1} 
θ_{1} 
9 
t_{1} 
67 
19 
t_{33} 
R_{1} 
θ_{1} 
9 
t_{1} 
65 
19 
t_{33} 
θ_{2} 
10 
t_{2} 
78 
20 
t_{25} 
θ_{2} 
10 
t_{2} 
46 
20 
t_{30} 
θ_{3} 
11 
t_{3} 
57 
23 
t_{9} 
θ_{3} 
11 
t_{3} 
67 
21 
t_{24} 
θ_{4} 
12 
t_{4} 
25 
23 
t_{15} 
θ_{4} 
12 
t_{4} 
44 
21 
t_{25} 
θ_{5} 
13 
t_{5} 
55 
25 
t_{4} 
θ_{5} 
13 
t_{5} 
55 
22 
t_{15} 
R_{2} 
θ_{6} 
12 
t_{6} 
98 
30 
t_{31} 
R_{2} 
θ_{6} 
10 
t_{6} 
100 
24 
t_{9} 
θ_{7} 
9 
t_{7} 
64 
32 
t_{18} 
θ_{7} 
9 
t_{7} 
68 
30 
t_{31} 
θ_{8} 
11 
t_{8} 
44 
40 
t_{32} 
θ_{8} 
12 
t_{8} 
47 
33 
t_{18} 
θ_{9} 
10 
t_{9} 
23 
42 
t_{22} 
θ_{9} 
11 
t_{9} 
24 
34 
t_{20} 
θ_{10} 
13 
t_{10} 
43 
42 
t_{29} 
θ_{10} 
13 
t_{10} 
45 
40 
t_{32} 
R_{3} 
θ_{11} 
10 
t_{11} 
100 
43 
t_{10} 
R_{3} 
θ_{11} 
11 
t_{11} 
99 
43 
t_{27} 
θ_{12} 
11 
t_{12} 
45 
44 
t_{8} 
θ_{12} 
12 
t_{12} 
44 
44 
t_{4} 
θ_{13} 
9 
t_{13} 
70 
44 
t_{27} 
θ_{13} 
9 
t_{13} 
67 
44 
t_{12} 
θ_{14} 
13 
t_{14} 
48 
45 
t_{12} 
θ_{14} 
13 
t_{14} 
45 
45 
t_{10} 
θ_{15} 
12 
t_{15} 
23 
46 
t_{20} 
θ_{15} 
10 
t_{15} 
22 
45 
t_{14} 
R_{4} 
θ_{16} 
11 
t_{16} 
68 
48 
t_{14} 
R_{4} 
θ_{16} 
12 
t_{16} 
89 
46 
t_{2} 
θ_{17} 
12 
t_{17} 
68 
52 
t_{24} 
θ_{17} 
10 
t_{17} 
56 
47 
t_{8} 
θ_{18} 
13 
t_{18} 
32 
55 
t_{5} 
θ_{18} 
13 
t_{18} 
33 
54 
t_{28} 
θ_{19} 
9 
t_{19} 
65 
57 
t_{3} 
θ_{19} 
9 
t_{19} 
66 
55 
t_{5} 
θ_{20} 
10 
t_{20} 
46 
64 
t_{7} 
θ_{20} 
11 
t_{20} 
34 
56 
t_{17} 
R_{5} 
θ_{21} 
13 
t_{21} 
75 
64 
t_{26} 
R_{5} 
θ_{21} 
13 
t_{21} 
86 
63 
t_{22} 
θ_{22} 
11 
t_{22} 
42 
65 
t_{19} 
θ_{22} 
10 
t_{22} 
63 
65 
t_{1} 
θ_{23} 
12 
t_{23} 
74 
67 
t_{1} 
θ_{23} 
11 
t_{23} 
76 
66 
t_{19} 
θ_{24} 
10 
t_{24} 
52 
68 
t_{16} 
θ_{24} 
12 
t_{24} 
21 
67 
t_{3} 
θ_{25} 
9 
t_{25} 
20 
68 
t_{17} 
θ_{25} 
9 
t_{25} 
21 
67 
t_{13} 
R_{6} 
θ_{26} 
11 
t_{26} 
64 
70 
t_{13} 
R_{6} 
θ_{26} 
12 
t_{26} 
115 
68 
t_{7} 
θ_{27} 
9 
t_{27} 
44 
72 
t_{30} 
θ_{27} 
9 
t_{27} 
43 
76 
t_{23} 
θ_{28} 
13 
t_{28} 
107 
74 
t_{23} 
θ_{28} 
10 
t_{28} 
54 
86 
t_{21} 
θ_{29} 
10 
t_{29} 
42 
75 
t_{21} 
θ_{29} 
13 
t_{29} 
96 
89 
t_{16} 
θ_{30} 
12 
t_{30} 
72 
78 
t_{2} 
θ_{30} 
11 
t_{30} 
20 
96 
t_{29} 
R_{7} 
θ_{31} 
9 
t_{31} 
30 
98 
t_{6} 
R_{7} 
θ_{31} 
9 
t_{31} 
30 
99 
t_{11} 
θ_{32} 
11 
t_{32} 
40 
100 
t_{11} 
θ_{32} 
11 
t_{32} 
40 
100 
t_{6} 
θ_{33} 
10 
t_{33} 
19 
107 
t_{28} 
θ_{33} 
10 
t_{33} 
19 
115 
t_{26} 
[0042] Table 1 will also be referred to. First, the pitch angles θ1 to θ5 of Example 1 will
be referred to.
[0043] The 1
^{st} pitch angle θ1 is 9°, the 2
^{nd} pitch angle θ2 is 10°, the 3
^{rd} pitch angle θ3 is 11°, the 4
^{th} pitch angle θ4 is 12°, and the 5
^{th} pitch angle θ5 is 13°.
[0044] The 1st pitch angle θ1 is 9°, which is a different value from those of the pitch
angles θ2 to θ5 of the other blade grooves constituting the 1
^{st} blade groove group R
_{1}. Likewise, the 2
^{nd} pitch angle θ2 to the 5
^{th} pitch angle θ5 also have different values from those of the pitch angles of the other
blade grooves.
[0045] In addition, among the pitch angles θ1 to θ5 of the blade grooves Q
_{1} to Q
_{5} constituting the 1st blade groove group R
_{1}, the lowest pitch angle θmin is the 1
^{st} pitch angle θ1, which is 9°. The highest pitch angle θmax is the 5
^{th} pitch angle θ5, which is 13°. θmaxθmin=θ5θ1=4° is satisfied.
[0046] Furthermore, when the pitch angles θ1 to θ5 of the blade grooves Q
_{1} to Q
_{5} constituting the 1st blade groove group R
_{1} are arranged in ascending order from θmin to θmax, they are 9°, 10°, 11°, 12°, and
13°. The angles are arranged to have equal differences of 1°.
[0047] The above can be summarized as follows. Apitch angle θn (e.g., θ1) is set to have
a different value from the pitch angles (e.g., θ2 to θ5) of the other blade grooves
constituting one blade groove group R. With respect to the values of pitch angles
θn, in a case where the lowest pitch angle for one of the blade groove groups R is
set as θmin and the highest pitch angle is set as θmax, θmaxθmin≤5° is satisfied.
With respect to the values of pitch angles θn, in a case where the pitch angles of
the blade grooves Q constituting one blade groove group R are arranged in ascending
order, values from θmin to θmax are set to have equal differences.
[0048] θ6 to θ33 can be set likewise. In other words, the values of the pitch angles corresponding
to each of the groups R
_{1} to R
_{7} of the grooves Q are all different from each other. In each of the groups R
_{1} to R
_{7}, the series of the values of the pitch angles arranged in ascending order have the
relationship of equal differences. In addition, when the minimum value of the pitch
angles is set as θmin and the maximum value thereof is set as θmax for each group,
θmaxθmin≦5° is satisfied.
[0049] The next blade groove having the same pitch angle (9°) as the 1
^{st} blade groove Q
_{1} having the pitch angle of 9° in the circumferential direction is the 7
^{th} blade groove Q
_{7} having θ7. Here, the sum of the pitch angles from the 1
^{st} blade groove Q
_{1} to the blade groove before the 7
^{th} blade groove Q
_{7} is called an integrated pitch angle (an integrated angle or a large pitch angle)
tn. An integrated pitch angle t
_{1} is 9°+10°+11°+12°+13°+12°=67°.
[0050] An integrated pitch angle tn can be defined as the sum of the pitch angles from an
nth blade groove Q (e.g., the 1
^{st} blade groove Q
_{1}) having the pitch angle θn to the blade groove before the kth blade groove Q (e.g.,
the 7
^{th} blade groove Q
_{7}) having the same value for a pitch angle θk as the blade groove Q to the next in
the circumferential direction.
[0051] In other words, among pitch angles having the same value as an nth pitch angle,
when the next pitch angle to the nth pitch angle is set as a kth pitch angle, the
angle obtained by integrating consecutive pitch angles from the nth pitch angle to
a (k1)th pitch angle is set as an integrated pitch angle.
[0052] Note that, with respect to an integrated pitch angle t
_{28}, the order of pitch angles returns to θ
_{1} across the pitch angle θ
_{33} as is ascertained from θ
_{28}, θ
_{29}...θ
_{33}, θ
_{1}, θ
_{2}...and θ
_{5}, and therefore the integrated pitch angle t
_{28} is the sum of the pitch angles before the pitch angle θ
_{5} having the same value to the next. That is, the integrated pitch angle t
_{28} is 13°+10°+12°+9°+11°+10°+9°+10°+11°+12°=107°. An integrated pitch angle t
_{30} is the sum of θ
_{30} to θ
_{4}, which is 72°. Likewise, the sums are obtained for the integrated pitch angles t
_{31}, t
_{32}, and t
_{33}, across θ
_{33}.
[0053] The integrated pitch angles tn obtained as described above are arranged in order
from lower angles. Then, the 9
^{th} integrated pitch angle t
_{9} and the 15
^{th} integrated pitch angle t
_{15} have the same value which is 23°. Likewise, the 22
^{nd} integrated pitch angle t
_{22} and the 29
^{th} integrated pitch angle t
_{29} have the same value which is 42°, the 8
^{th} integrated pitch angle t
_{8} and the 27
^{th} integrated pitch angle t
_{27} have the same value which is 44°, the 7
^{th} integrated pitch angle t
_{7} and the 26
^{th} integrated pitch angle t
_{26} have the same value which is 64°, and the 16
^{th} integrated pitch angle t
_{16} and the 17
^{th} integrated pitch angle t
_{17} have the same value which is 68°.
[0054] Here, the pitch angles θn of the blade grooves Q are set such that three or more
integrated pitch angles does not have the same value. That is, it can be said that,
among the 1
^{st} integrated pitch angle t
_{1} to the 33
^{rd} integrated pitch angle t
_{33}, the number of integrated pitch angles tn having one value is two or smaller. This
will be called a first requirement. In other words, according to the first requirement,
an integrated pitch angle has a single value that is different from those of the other
integrated pitch angles or a value common for a pair of two integrated pitch angles
is different from those of the other integrated pitch angles.
[0055] There are five sets of integrated pitch angles tn having the same values, which are
23°, 42°, 44°, 64°, and 68°. It accounts for about 15.2% (=(5/33)×100) of the 33 blades
P.
[0056] It can be said that, among the 1
^{st} integrated pitch angle t
_{1} to ith integrated pitch angle t
_{i}, there are two or smaller number of integrated pitch angles having one value and
the number of sets of integrated pitch angles having the same values does not exceed
i×0.18. This is called a second requirement. In other words, according to the second
requirement, the number of pairs of integrated pitch angles having the common values
does not exceed i×0.18.
[0057] In a case where the integrated pitch angles tn are arranged in order from lower angles,
there are the 4
^{th} integrated pitch angle t
_{4} having 25°, the 31
^{st} integrated pitch angle t
_{31} having 30°, the 18
^{th} integrated pitch angle t18 having 32°, and the 32
^{nd} integrated pitch angle t
_{32} having 40° between the set of the 9
^{th} integrated pitch angle t
_{9} and the 15
^{th} integrated pitch angle t
_{15} having 23° and the set of the 22
^{nd} integrated pitch angle t
_{22} and the 29
^{th} integrated pitch angle t
_{29} having 42°.
[0058] Only the 4
^{th} integrated pitch angle t
_{4} has 25°. The same applies to 30°, 32°, and 40°.
[0059] The pitch angles θn are set such that at least one integrated pitch angle (e.g.,
t
_{4}, t
_{31}, t
_{18}, or t
_{32}) not having the same value is included between a set of integrated pitch angles having
the same value (e.g., the set having 23°) and a set having the same value (e.g., the
set having 42°). This is called a third requirement. In other words, according to
the third requirement, in the series of all integrated pitch angles in ascending order,
at least one integrated pitch angle having a single value is included between a first
pair of integrated pitch angles having a common value and a second pair of integrated
pitch angles having another common value.
[0060] In addition, it can also be said as follows. The difference in angles between the
set of integrated pitch angles having the same values (e.g., the set having 23°) and
the set having the same values (e.g., the set having 42°) is greater than 1°. This
is called a fourth requirement. In other words, according to the fourth requirement,
the difference in values between the first pair of integrated pitch angles having
the common value and the second pair of integrated pitch angles having the other common
value is greater than 1.
[0061] Example 1 is most preferable since it satisfies all of the first to fourth requirements.
[0062] Example 2 satisfies the first and second requirements. Meanwhile, integrated pitch
angles having the same value are not included between the set of 44° and the set of
45° having the same values. Thus, the third requirement is not satisfied. Furthermore,
the difference in angles between the set of 44° and the set of 45° having the same
values is 1°, which does not satisfy the fourth requirement.
[Table 2]
Example 3 
Blade groove groups 
Pitch angles 
Large pitch angles 
Large pitch angles arranged from lower angles 
R_{n} 
θ_{n} 
° 

° 
° 
t_{n} 
R_{1} 
θ_{1} 
9.5 
t_{1} 
84.5 
20 
t_{29} 
θ_{2} 
10.5 
t_{2} 
111 
20 
t_{30} 
θ_{3} 
11.5 
t_{3} 
74 
24 
t_{11} 
θ_{4} 
12.5 
t_{4} 
40.5 
24 
t_{18} 
θ_{5} 
13.5 
t_{5} 
86.5 
25 
t_{23} 
R_{2} 
θ_{6} 
14.5 
t_{6} 
48 
40.5 
t_{4} 
θ_{7} 
12.5 
t_{7} 
132 
47 
t_{15} 
θ_{8} 
9.5 
t_{8} 
96 
48 
t_{6} 
θ_{9} 
11.5 
t_{9} 
75 
49 
t_{10} 
θ_{10} 
14.5 
t_{10} 
49 
50 
t_{17} 
R_{3} 
θ_{11} 
10.5 
t_{11} 
24 
59.5 
t_{12} 
θ_{12} 
13.5 
t_{12} 
59.5 
62.5 
t_{21} 
θ_{13} 
10.5 
t_{13} 
134 
64 
t_{27} 
θ_{14} 
14.5 
t_{14} 
109 
64 
t_{28} 
θ_{15} 
11.5 
t_{15} 
47 
72 
t_{24} 
R_{4} 
θ_{16} 
9.5 
t_{16} 
73 
73 
t_{16} 
θ_{17} 
13.5 
t_{17} 
50 
74 
t_{3} 
θ_{18} 
12.5 
t_{18} 
24 
75 
t_{9} 
θ_{19} 
11.5 
t_{19} 
100 
84.5 
t_{1} 
θ_{20} 
12.5 
t_{20} 
100 
86.5 
t_{5} 
R_{5} 
θ_{21} 
13.5 
t_{21} 
62.5 
86.5 
t_{22} 
θ_{22} 
9.5 
t_{22} 
86.5 
96 
t_{8} 
θ_{23} 
14.5 
t_{23} 
25 
100 
t_{19} 
θ_{24} 
10.5 
t_{24} 
72 
100 
t_{20} 
θ_{25} 
14.5 
t_{25} 
130 
102 
t_{26} 
R_{6} 
θ_{26} 
13.5 
t_{26} 
102 
109 
t_{14} 
θ_{27} 
11.5 
t_{27} 
64 
111 
t_{2} 
θ_{28} 
12.5 
t_{28} 
64 
130 
t_{25} 
θ_{29} 
9.5 
t_{29} 
20 
132 
t_{7} 
θ_{30} 
10.5 
t_{30} 
20 
134 
t_{13} 
[0063] Table 2 will be referred to. An impeller according to Example 3 is constituted by
30 blades. Thus, the number of the blade grooves is 30, and the pitch angles θn of
the blade grooves are θ
_{1} to θ
_{30}. The integrated pitch angles tn are t
_{1} to t
_{30}.
[0064] Each blade groove group Rn is constituted by six blade grooves. Pitch angles for
one blade groove group Rn are set to 9.5°, 10.5°, 11.5°, 12.5°, 13.5°, and 14.5° from
a small pitch angle θmin to θmax.
[0065] Example 3 satisfies the first requirement, the second requirement, and the fourth
requirement. Meanwhile, integrated pitch angles not having the same value are not
included between the set of 20° and the set of 24° having the same values. Thus, the
third requirement is not satisfied.
[0066] In an aspect of the present invention, it is important to satisfy the first requirement
and the second requirement. Such an aspect of the present invention exhibits the following
effects. They will be described with reference to Example 1 of Table 1.
[0067] The pitch angles θn (e.g., θ1 to θ5) are set such that all conditions that each pitch
angle has a value (9°, 10°, 11°, 12°, or 13°) different from the pitch angles of the
other blade grooves constituting one blade groove group (R
_{1}), θmaxθmin≤5° (θ5θ1=4°), and all values from θmin to θmax (9°, 10°, 11°, 12°, and
13°) have equal differences are satisfied. By having a value different from the pitch
angles of the other blade grooves constituting the blade groove group (R
_{1}), noise can be suppressed. Meanwhile, under the conditions of θmaxθmin≤5° and the
equal differences between the values from θmin to θmax, the magnitude of irregularity
in pitch angles comes into a certain range, and pump efficiency is also ensured. The
blade grooves Q are divided into the plurality of groups (R
_{1} to R
_{7}), and thus pitch angles at which noise can be reduced while pump efficiency of the
liquid pump is ensured with respect to each of the groups can be set.
[0068] Furthermore, among the 1
^{st} integrated pitch angle t
_{1} to the ith integrated pitch angle t
_{i} (the 33
^{rd} integrated pitch angle t
_{33}), there are only two or fewer integrated pitch angles having one value (e.g., 23°)
(the 9
^{th} integrated pitch angle t
_{9} and the 15
^{th} integrated pitch angle t
_{15}). Disposition of blade grooves having the same pitch angle at uniform intervals can
cause noise. By diminishing the part that causes noise, noise can be further reduced.
In addition, among the 1
^{st} integrated pitch angle t
_{1} to the ith integrated pitch angle t
_{1} (the 33
^{rd} integrated pitch angle t
_{33}), the number of sets (5) having the same value is i×0.18 or less (33××0.18=5.94 or
less). It is ascertained that, in the case where the number of sets does not exceed
i×0.18, particularly excellent noise reduction was exhibited. If there are a large
number of sets having the same value even though there are two or fewer integrated
pitch angles having one value, it is difficult to reduce noise. Based on this point,
by setting the number of sets having the same value to i×0.18 or smaller, noise can
be further reduced.
[0069] According to an aspect of the present invention, it is prevented to dispose the blade
grooves Q having the same pitch angle at uniform intervals, focusing on the integrated
pitch angles tn. Thus, with respect to each of the blade groove groups R and the entire
impeller 20, noise can be reduced while pump efficiency of the liquid pump is ensured.
[0070] Furthermore, with respect to the integrated pitch angles tn, at least one integrated
pitch angle not having the same value (t
_{4} having 25°, t
_{31} having 30°, t
_{18} having 32°, and t
_{32} having 40°) is included between the set having the same value (t
_{9} and t
_{15} having 23°) and the set having the same value (t
_{22} and t
_{29} having 42°). If the value of the set having the same value (t
_{9} and t
_{15} having 23°) is approximate to the value of the set having the same value (t
_{22} and t
_{29} having 42°), there are many integrated pitch angles having approximate values. By
inserting the integrated pitch angles not having the same value (t
_{4} having 25°, t
_{31} having 30°, t
_{18} having 32°, and t
_{32} having 40°), the values of the sets having the same value are separated, and thus
noise can be further reduced.
[0071] Furthermore, the difference in angle between the set having the same value (t
_{9} and 115 having 23°) and the set having the same value (t
_{22} and t
_{29} having 42°) is greater than 1°. If the values of the sets having the same values
are approximate to each other, there are many integrated pitch angles having approximate
values. By setting the difference in angle between the sets having the same values
to be greater than 1°, the values of the sets having the same values can be separated,
and thus noise can be further reduced.
[0072] Furthermore, θmin is 9° or higher, and θmax is 13° or lower. It is ascertained that,
by setting the pitch angles of the blade grooves to come within the range, pump efficiency
of the liquid pump can be particularly ensured.
[0073] Note that a liquid pump in which an impeller according to an aspect of the present
invention is mounted is not limited to a fuel pump. An impeller according to an aspect
of the present invention can also be mounted in other types of liquid pump. Further,
a liquid pump can also be provided in an automobile or a vehicle other than a twowheeled
vehicle.
[0074] The present invention is not limited to the embodiment as long as an embodiment can
exhibit the actions and effects of the aspect of the present invention.
[Industrial Applicability]
[0075] It is preferable for an impeller according to an aspect of the present invention
to be mounted in a fuel pump.
[Reference Signs List]
[0076]
 10
 Fuel pump (liquid pump)
 11
 Motor (drive source)
 20
 Impeller
 21
 Disc (base, body)
 P
 Blade
 Q
 Blade groove
 R
 Blade groove group
 CL
 Rotation center
 L1, L2
 Line segment
1. An impeller in substantially a disc shape that is used in a liquid pump for pressurefeeding
a liquid by being rotated by a drive source, the impeller comprising:
i blades provided in a circumferential direction and i blade grooves formed in regions
sandwiched by the blades,
wherein an angle formed by a line segment connecting the center of an nth (n is an
integer from 1 to i) blade to a rotation center of the impeller and a line segment
connecting the center of an (n+1)th blade (however, the 1^{st} blade when n=i) to the rotation center of the impeller is set as a pitch angle θn
of an nth blade groove,
wherein the blade grooves are continuous from the 1^{st} blade groove and constitute each of m blade groove groups, m satisfying m≥5, (however,
in a case where i/m is not an integer, a blade groove group including the ith blade
groove is constituted by the remaining number of blade grooves which is less than
m),
wherein the pitch angle θn is set to a value different from the pitch angles of the
other blade grooves constituting the one blade groove group,
wherein, in a case where a lowest pitch angle in the one blade groove group is set
as θmin and a highest pitch angle is set as θmax, θmaxθmin≤5°, and values from θmin
to θmax are set to have equal differences,
wherein the sum of pitch angles from the nth blade groove having the pitch angle
θn to the blade groove before a kth blade groove having a pitch angle θk which is
the same value to the next in the circumferential direction is set as an integrated
pitch angle tn, and
wherein, among a 1^{st} integrated pitch angle t_{1} to an ith integrated pitch angle t_{i}, the number of integrated pitch angles having one value is two or less, and the number
of sets having the same value does not exceed i×0.18.
2. The impeller according to claim 1, wherein, in a case where the number of sets having
the same value is two or more, when the 1^{st} integrated pitch angle t_{1} to the ith integrated pitch angle t_{i} are arranged in order from lower angles, at least one integrated pitch angle not
having the same value is included between a set having the same value and a set having
the same value.
3. The impeller according to claim 1, wherein, in a case where the number of sets having
the same value is two or more, the difference in angle between the sets having the
same values is greater than 1°.
4. The impeller according to any one of claims 1 to 3, wherein θmin is 9° or higher and
θmax is 13° or lower.
5. An impeller for a liquid pump comprising:
a disc;
i blades disposed on the disc in a circumferential direction; and
i grooves provided on the disc, each of which is sandwiched between the blades,
wherein the following requirements are satisfied:
(i) the grooves are divided into a plurality of groups, each of the groups is constituted
by m (m≥5) grooves arranged in series (however, in a case where i/m is not an integer,
one group is constituted by the remaining number (1, 2, 3, or 4) of grooves;
(ii) in each group, the values of pitch angles are different;
(iii) in each group, the series of the values of pitch angles arranged in ascending
order have the relationship of equal differences;
(iv) in each group, θmaxθmin≤5°;
(v) an integrated pitch angle has a single value that is different from those of the
other integrated pitch angles or a value common for a pair of two integrated pitch
angles is different from those of the other integrated pitch angles; and
(vi) the number of pairs of integrated pitch angles having common values does not
exceed i×0.18,
however,
the angle formed by a line segment extending between the center of an nth (n is an
integer from 1 to i) blade and the center of the disc and a line segment extending
between the center of an (n+1)th blade (however, the center of the 1st blade when
n=i) and the center of the disc is set as an nth pitch angle,
the minimum value of the pitch angles is set as θmin and the maximum value is set
as θmax for each group,
the next pitch angle to the nth pitch angle is set as a kth pitch angle among pitch
angles having the same value as the nth pitch angle, and
an angle obtained by integrating consecutive pitch angles from the nth pitch angle
to a (k1)th pitch angle is set as an integrated pitch angle.
6. The impeller according to claim 5, wherein, in the series of all integrated pitch
angles in ascending order, at least one integrated pitch angle having a single value
is placed between a first pair of integrated pitch angles having a common value and
a second pair of integrated pitch angles having another common value.
7. The impeller according to claim 5 or claim 6, wherein the difference in values between
the first pair of integrated pitch angles having the common value and the second pair
of integrated pitch angles having the other common value is greater than 1.
8. The impeller according to any one of claims 5 to 7, wherein θmin is 9° or higher and
θmax is 13° or lower.