EP3597924B1

EP3597924B1 - Impeller

Info

Publication number: EP3597924B1
Application number: EP18768414.7A
Authority: EP
Inventors: Naoki Takeuchi; Shinichiro Horisoko
Original assignee: Mitsuba Corp
Current assignee: Mitsuba Corp
Priority date: 2017-03-13
Filing date: 2018-02-27
Publication date: 2022-06-15
Anticipated expiration: 2038-02-27
Also published as: JP6659911B2; EP3597924A4; JPWO2018168442A1; EP3597924A1; WO2018168442A1

Description

[Technical Field]

The present invention relates to an impeller that is used for a liquid pump.

[Background Art]

A general liquid pump that pumps a liquid by rotating a disc-like 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.
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.
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]

[Patent Literature 1]
Japanese Patent Application, Publication No. H11-50990

[Summary of Invention]

[Technical Problem]

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.
The present invention aims to provide an impeller that can reduce noise while ensuring pump efficiency of a liquid pump.

[Solution to Problem]

There is disclosed an impeller in substantially a disc shape that is used in a liquid pump for pressure-feeding 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 n-th (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 n-th 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 i-th 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, θmax-θmin≤5°, and values from θmin to θmax are set to have equal differences, the sum of pitch angles from the n-th blade groove having the pitch angle θn to the blade groove before a k-th 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 t₁ to an i-th 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.
According to the above-described aspect, in the case where the number of sets having the same values is two or more, when the 1^st integrated pitch angle t₁ to the i-th 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.
According to the above-described 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°.
According to the above-described aspect, θmin is preferably set to 9° or higher and θmax is preferably set to 13° or lower.
The invention as claimed is directed to 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, θmax-θmin≤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 n-th (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 n-th 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 n-th pitch angle is set as a k-th pitch angle among pitch angles having the same value as the n-th pitch angle, and an angle obtained by integrating consecutive pitch angles from the n-th pitch angle to a (k-1)-th pitch angle is set as an integrated pitch angle.
According to the above-described 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.
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.
In addition, for example, θmin is 9° or higher and θmax is 13° or lower

[Advantageous Effects of Invention]

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, θmax-θmin≤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 θmax-θmin≤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.
Furthermore, there are only two or fewer integrated pitch angles having one value among the 1^st integrated pitch angle t₁ to the i-th 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 t₁ to the i-th 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.
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.
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.
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.
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]

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]

An embodiment of the present invention will be described with reference to the accompanying drawings.

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 two-wheeled 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.
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 1 1a 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.
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.
The lower casing 31 has a casing part intake port 31a penetrating the lower casing to take in a liquid fuel from the outside.
The upper casing 32 has a casing part discharge port 32a penetrating the upper casing to discharge a liquid fuel into the housing 15.
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.
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.
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 P₁ to blade P₃₃ that are provided in the circumferential direction, and 33 blade grooves Q₁ to Q₃₃ that are formed in regions sandwiched by the blade P₁ to blade P₃₃.
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 ring-like region on the disc 21 in the circumferential direction, and i grooves Q, each of which is provided between the blades P in the ring-like region on the disc 21.
An arbitrarily selected blade P₁ is assumed to be the 1^st blade P₁, and those arranged clockwise from the first blade are assumed to be the 2^nd blade P₂, the 3^rd blade P₃, and so on. The impeller 20 has the first blade P₁ to the 33^rd blade P₃₃.
The blade groove Q₁ that is formed in the region sandwiched by the 1^st blade P₁ and the 2^nd blade P₂ (intermediate region) is assumed to be the 1^st blade groove Q₁. Likewise, the blade groove Q₂ that is formed in the region sandwiched by the 2^nd blade P₂ and the 3^rd blade P₃ is assumed to be the 2^nd blade groove Q₂. The blade groove Q₃₃ that is formed in the region sandwiched by the 33^rd blade P₃₃ and the 1^st blade P₁ is assumed to be the 33^rd blade groove Q₃₃. The impeller 20 has the 1^st blade groove Q₁ to the 33^rd blade groove Q₃₃.
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.
The angle formed by a line segment L1 connecting the center of the 1^st blade P₁ to a rotation center CL of the impeller 20 and a line segment L2 connecting the center of the 2^nd blade P₂ to the rotation center CL of the impeller 20 is called a pitch angle θ₁ of the 1^st blade groove. Likewise, the angle formed by a line segment L2 connecting the center of the 2^nd blade P₂ to the rotation center CL of the impeller 20 and a line segment L3 connecting the center of the 3^rd blade P₃ to the rotation center CL of the impeller 20 is called a pitch angle θ₂ of the 2^nd blade groove. The angle formed by a line segment L33 connecting the center of the 33^rd blade P₃₃ to the rotation center CL of the impeller 20 and the line segment L1 connecting the center of the 1^st blade P₁ to the rotation center CL of the impeller 20 is called a pitch angle θ₃₃ of the 33^rd blade groove.
That is, the angle formed by each of the line segments L1 to L33 connecting the center of an n-th (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 n-th blade groove. Alternatively, the angle formed by each of the line segments L1 to L33 extending between the center of the n-th (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 n-th pitch angle.
The blade grooves Q₁ to Q₃₀ are continuous from the 1^st blade groove Q₁ and constitute five blade groove groups R₁ to R₆. The three blade grooves Q₃₁ to Q₃₃ constitute a blade groove group R₇.
The 1^st blade groove group R₁ is constituted by the 1^st blade groove Q₁ to the 5^th blade groove Q₅. Likewise, the 2^nd blade groove group R₂ is constituted by the 6^th blade groove Q₆ to the 10^th blade groove Q₁₀.

The blade grooves Q are continuous from the 1^st blade groove Q₁ and constitute m blade groove groups R₁ to R₇, m satisfying m≥5. However, in a case where i/m is not an integer, the blade groove group R₇ that includes the i-th blade groove Q₃₃ is constituted by the remaining number of blade grooves which is less than m. Alternatively, the grooves Q are grouped into multiple groups R₁ to R₇. Each of the groups R₁ to R₇ 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
R₁	θ₁	9	t₁	67	19	t₃₃	R₁	θ₁	9	t₁	65	19	t₃₃
	θ₂	10	t₂	78	20	t₂₅		θ₂	10	t₂	46	20	t₃₀
	θ₃	11	t₃	57	23	t₉		θ₃	11	t₃	67	21	t₂₄
	θ₄	12	t₄	25	23	t₁₅		θ₄	12	t₄	44	21	t₂₅
	θ₅	13	t₅	55	25	t₄		θ₅	13	t₅	55	22	t₁₅
R₂	θ₆	12	t₆	98	30	t₃₁	R₂	θ₆	10	t₆	100	24	t₉
	θ₇	9	t₇	64	32	t₁₈		θ₇	9	t₇	68	30	t₃₁
	θ₈	11	t₈	44	40	t₃₂		θ₈	12	t₈	47	33	t₁₈
	θ₉	10	t₉	23	42	t₂₂		θ₉	11	t₉	24	34	t₂₀
	θ₁₀	13	t₁₀	43	42	t₂₉		θ₁₀	13	t₁₀	45	40	t₃₂
R₃	θ₁₁	10	t₁₁	100	43	t₁₀	R₃	θ₁₁	11	t₁₁	99	43	t₂₇
	θ₁₂	11	t₁₂	45	44	t₈		θ₁₂	12	t₁₂	44	44	t₄
	θ₁₃	9	t₁₃	70	44	t₂₇		θ₁₃	9	t₁₃	67	44	t₁₂
	θ₁₄	13	t₁₄	48	45	t₁₂		θ₁₄	13	t₁₄	45	45	t₁₀
	θ₁₅	12	t₁₅	23	46	t₂₀		θ₁₅	10	t₁₅	22	45	t₁₄
R₄	θ₁₆	11	t₁₆	68	48	t₁₄	R₄	θ₁₆	12	t₁₆	89	46	t₂
	θ₁₇	12	t₁₇	68	52	t₂₄		θ₁₇	10	t₁₇	56	47	t₈
	θ₁₈	13	t₁₈	32	55	t₅		θ₁₈	13	t₁₈	33	54	t₂₈
	θ₁₉	9	t₁₉	65	57	t₃		θ₁₉	9	t₁₉	66	55	t₅
	θ₂₀	10	t₂₀	46	64	t₇		θ₂₀	11	t₂₀	34	56	t₁₇
Rs	θ₂₁	13	t₂₁	75	64	t₂₆	Rs	θ₂₁	13	t₂₁	86	63	t₂₂
	θ₂₂	11	t₂₂	42	65	t₁₉		θ₂₂	10	t₂₂	63	65	t₁
	θ₂₃	12	t₂₃	74	67	t₁		θ₂₃	11	t₂₃	76	66	t₁₉
	θ₂₄	10	t₂₄	52	68	t₁₆		θ₂₄	12	t₂₄	21	67	t₃
	θ₂₅	9	t₂₅	20	68	t₁₇		θ₂₅	9	t₂₅	21	67	t₁₃
R₆	θ₂₆	11	t₂₆	64	70	t₁₃	R₆	θ₂₆	12	t₂₆	115	68	t₇
	θ₂₇	9	t₂₇	44	72	t₃₀		θ₂₇	9	t₂₇	43	76	t₂₃
	θ₂₈	13	t₂₈	107	74	t₂₃		θ₂₈	10	t₂₈	54	86	t₂₁
	θ₂₉	10	t₂₉	42	75	t₂₁		θ₂₉	13	t₂₉	96	89	t₁₆
	θ₃₀	12	t₃₀	72	78	t₂		θ₃₀	11	t₃₀	20	96	t₂₉
R₇	θ₃₁	9	t₃₁	30	98	t₆	R₇	θ₃₁	9	t₃₁	30	99	t₁₁
	θ₃₂	11	t₃₂	40	100	t₁₁		θ₃₂	11	t₃₂	40	100	t₆
	θ₃₃	10	t₃₃	19	107	t₂₈		θ₃₃	10	t₃₃	19	115	t₂₆

Table 1 will also be referred to. First, the pitch angles θ1 to θ5 of Example 1 will be referred to.
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°.
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 R₁. 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.
In addition, among the pitch angles θ1 to θ5 of the blade grooves Q₁ to Q₅ constituting the 1st blade groove group R₁, 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°. θmax-θmin=θ5-θ1=4° is satisfied.
Furthermore, when the pitch angles θ1 to θ5 of the blade grooves Q₁ to Q₅ constituting the 1st blade groove group R₁ 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°.
The above can be summarized as follows. A pitch 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, θmax-θmin≤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.
θ6 to θ33 can be set likewise. In other words, the values of the pitch angles corresponding to each of the groups R₁ to R₇ of the grooves Q are all different from each other. In each of the groups R₁ to R₇, 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, θmax-θmin≦5° is satisfied.
The next blade groove having the same pitch angle (9°) as the 1^st blade groove Q₁ having the pitch angle of 9° in the circumferential direction is the 7^th blade groove Q₇ having θ7. Here, the sum of the pitch angles from the 1^st blade groove Q₁ to the blade groove before the 7^th blade groove Q₇ is called an integrated pitch angle (an integrated angle or a large pitch angle) tn. An integrated pitch angle t₁ is 9°+10°+11°+12°+13°+12°=67°.
An integrated pitch angle tn can be defined as the sum of the pitch angles from an n-th blade groove Q (e.g., the 1^st blade groove Q₁) having the pitch angle θn to the blade groove before the k-th blade groove Q (e.g., the 7^th blade groove Q₇) having the same value for a pitch angle θk as the blade groove Q to the next in the circumferential direction.
In other words, among pitch angles having the same value as an n-th pitch angle, when the next pitch angle to the n-th pitch angle is set as a k-th pitch angle, the angle obtained by integrating consecutive pitch angles from the n-th pitch angle to a (k-1)-th pitch angle is set as an integrated pitch angle.
Note that, with respect to an integrated pitch angle t₂₈, the order of pitch angles returns to θ₁ across the pitch angle θ₃₃ as is ascertained from θ₂₈, θ₂₉...θ₃₃, θ₁, θ₂...and θ₅, and therefore the integrated pitch angle t₂₈ is the sum of the pitch angles before the pitch angle θ₅ having the same value to the next. That is, the integrated pitch angle t₂₈ is 13°+10°+12°+9°+11°+10°+9°+10°+11°+12°=107°. An integrated pitch angle t₃₀ is the sum of θ₃₀ to θ₄, which is 72°. Likewise, the sums are obtained for the integrated pitch angles t₃₁, t₃₂, and t₃₃, across θ₃₃.
The integrated pitch angles tn obtained as described above are arranged in order from lower angles. Then, the 9^th integrated pitch angle t₉ and the 15^th integrated pitch angle t₁₅ have the same value which is 23°. Likewise, the 22^nd integrated pitch angle t₂₂ and the 29^th integrated pitch angle t₂₉ have the same value which is 42°, the 8^th integrated pitch angle t₈ and the 27^th integrated pitch angle t₂₇ have the same value which is 44°, the 7^th integrated pitch angle t₇ and the 26^th integrated pitch angle t₂₆ have the same value which is 64°, and the 16^th integrated pitch angle t₁₆ and the 17^th integrated pitch angle t₁₇ have the same value which is 68°.
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 t₁ to the 33^rd integrated pitch angle t₃₃, 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.
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.
It can be said that, among the 1^st integrated pitch angle t₁ to i-th 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.
In a case where the integrated pitch angles tn are arranged in order from lower angles, there are the 4^th integrated pitch angle t₄ having 25°, the 31^st integrated pitch angle t₃₁ having 30°, the 18^th integrated pitch angle t18 having 32°, and the 32^nd integrated pitch angle t₃₂ having 40° between the set of the 9^th integrated pitch angle t₉ and the 15^th integrated pitch angle t₁₅ having 23° and the set of the 22^nd integrated pitch angle t₂₂ and the 29^th integrated pitch angle t₂₉ having 42°.
Only the 4^th integrated pitch angle t₄ has 25°. The same applies to 30°, 32°, and 40°.
The pitch angles θn are set such that at least one integrated pitch angle (e.g., t₄, t₃₁, t₁₈, or t₃₂) 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.
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.
Example 1 is most preferable since it satisfies all of the first to fourth requirements.

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	θn	○		○	○	tn
R₁	θ₁	9.5	t₁	84.5	20	t₂₉
	θ₂	10.5	t₂	111	20	t₃₀
	θ₃	11.5	t₃	74	24	t₁₁
	θ₄	12.5	t₄	40.5	24	t₁₈
	θ₅	13.5	t₅	86.5	25	t₂₃
R₂	θ₆	14.5	t₆	48	40.5	t4
	θ₇	12.5	t₇	132	47	t₁₅
	θ₈	9.5	t₈	96	48	t₆
	θ₉	11.5	t₉	75	49	t₁₀
	θ₁₀	14.5	t₁₀	49	50	t₁₇
R₃	θ₁₁	10.5	t₁₁	24	59.5	t₁₂
	θ₁₂	13.5	t₁₂	59.5	62.5	t₂₁
	θ₁₃	10.5	t₁₃	134	64	t₂₇
	θ₁₄	14.5	t₁₄	109	64	t₂₈
	θ₁₅	11.5	t₁₅	47	72	t₂₄
R₄	θ₁₆	9.5	t₁₆	73	73	t₁₆
	θ₁₇	13.5	t₁₇	50	74	t₃
	θ₁₈	12.5	t₁₈	24	75	t₉
	θ₁₉	11.5	t₁₉	100	84.5	t₁
	θ₂₀	12.5	t₂₀	100	86.5	t₅
R₅	θ₂₁	13.5	t₂₁	62.5	86.5	t₂₂
	θ₂₂	9.5	t₂₂	86.5	96	t₈
	θ₂₃	14.5	t₂₃	25	100	t₁₉
	θ₂₄	10.5	t₂₄	72	100	t₂₀
	θ₂₅	14.5	t₂₅	130	102	t₂₆
R₆	θ₂₆	13.5	t₂₆	102	109	t₁₄
	θ₂₇	11.5	t₂₇	64	111	t₂
	θ₂₈	12.5	t₂₈	64	130	t₂₅
	θ₂₉	9.5	t ₂₉	20	132	t₇
	θ₃₀	10.5	t ₃₀	20	134	t₁₃

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 θ₁ to θ₃₀. The integrated pitch angles tn are t₁ to t₃₀.
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.
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.
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.
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 (R₁), θmax-θmin≤5° (θ5-θ1=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 (R₁), noise can be suppressed. Meanwhile, under the conditions of θmax-θmin≤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 (R₁ to R₇), 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.
Furthermore, among the 1^st integrated pitch angle t₁ to the i-th integrated pitch angle t_i (the 33^rd integrated pitch angle t₃₃), there are only two or fewer integrated pitch angles having one value (e.g., 23°) (the 9^th integrated pitch angle t₉ and the 15^th integrated pitch angle t₁₅). 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 t₁ to the i-th integrated pitch angle t_i (the 33^rd integrated pitch angle t₃₃), 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.
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.
Furthermore, with respect to the integrated pitch angles tn, at least one integrated pitch angle not having the same value (t₄ having 25°, t₃₁ having 30°, t₁₈ having 32°, and t₃₂ having 40°) is included between the set having the same value (t₉ and t₁₅ having 23°) and the set having the same value (t₂₂and t₂₉ having 42°). If the value of the set having the same value (t₉ and t₁₅ having 23°) is approximate to the value of the set having the same value (t₂₂and t₂₉ having 42°), there are many integrated pitch angles having approximate values. By inserting the integrated pitch angles not having the same value (t₄ having 25°, t₃₁ having 30°, t₁₈ having 32°, and t₃₂ having 40°), the values of the sets having the same value are separated, and thus noise can be further reduced.
Furthermore, the difference in angle between the set having the same value (t₉ and t₁₅ having 23°) and the set having the same value (t₂₂and t₂₉ 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.
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.
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 two-wheeled vehicle.
Any embodiments that exhibit the above-described actions and effects can also be considered by the skilled person in the art.

[Industrial Applicability]

It is preferable for an impeller according to an aspect of the present invention to be mounted in a fuel pump.

[Reference Signs List]

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

Claims

An impeller (20) for a liquid pump (10) comprising:
a disc (21);

i blades (P) disposed on the disc (21) in a circumferential direction; and

i grooves (Q) provided on the disc (21), each of which is sandwiched between the blades (P),

characterized in that

an angle formed by a line segment (L1) connecting the center of an n-th blade (P) to the center of the disc (21) and a line segment (L2) connecting the center of an (n+1)-th blade (P), which is however the 1st blade when n=i, to the center of the disc (21) is set as an n-th pitch angle θn of an n-th blade groove (Q), wherein n is an integer from 1 to i;

the next pitch angle to the n-th pitch angle is set as a k-th pitch angle among pitch angles having the same value as the n-th pitch angle, and

an angle obtained by integrating consecutive pitch angles from the n-th pitch angle to a (k-1)-th pitch angle is set as an integrated pitch angle;

and in that the following requirements are satisfied:
i) the grooves (Q) are divided into a plurality of groups, each of the groups is constituted by m grooves (Q) arranged in series, with m≥5, however, in a case where i/m is not an integer, one group is constituted by the remaining number of grooves (Q), namely 1, 2, 3 or 4 grooves (Q);

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, the minimum value of the pitch angles is set as θmin and the maximum value is set as θmax, and θmax-θmin≤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.
The impeller (20) according to claim 1, 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.
The impeller (20) according to claim 1 or claim 2, 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.
The impeller (20) according to any one of claims 1 to 3, wherein θmin is 9° or higher and θmax is 13° or lower.