Water pump for cleaning machine and cleaning machine

Abstract

The utility model relates to a water pump for a cleaning machine and the cleaning machine, the water pump comprises a pump shell and an impeller rotatably arranged in the pump shell, the side portion of the pump shell is provided with a water outlet flow channel spirally extending in the circumferential direction, and a partition tongue is formed at the throat position where the water outlet flow channel is connected with the pump shell. A high-pressure area used for pressurizing water flow is formed by the impeller and the inner side of the partition tongue, and back blades capable of being matched with the partition tongue to balance axial force and / or radial force of the impeller are arranged on the upper surface of the impeller. The high-pressure area can pressurize outlet water so as to improve the water pressure and lift, and the water pumping efficiency is improved on the basis of meeting the water drawing flow; the back blades are arranged on the back face of the impeller to balance the axial force of the impeller, meanwhile, the distance between the impeller and the partition tongue is restrained within a specific range, and the radial balance force on the impeller is strengthened through control over the local flow speed in the range and cooperation of the back blades, so that the impeller rotates stably, noise is lowered, and meanwhile the service life of the impeller is prolonged. And the water pumping efficiency is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of dishwashers, and in particular to a water pump for a washing machine and a washing machine. Background Art

[0002] Dishwashers have been widely used in home kitchens. Dishwashers are generally provided with a spray arm for spraying water, a concave water return area is provided at the bottom of the cabinet, the top of the water return area is covered with a filter plate, and a water pump is used to pump water from the water return area to the spray arm above the filter plate to realize the circulation spraying of washing water.

[0003] Using an open water pump to draw water for the spray arm can greatly shorten the return water path, improve the return water efficiency, and facilitate the maintenance of the water pump. "An open water pump and cleaning machine" (application number: CN202211216848.9) with publication number CN115573915A discloses a structure in which a concave return water area is provided at the bottom of the box body, and the top of the return water area is covered with a filter plate. The open water pump is arranged in the return water area, and there is a water suction gap between the water suction port at the bottom of the pump housing and the bottom of the return water area. The first water outlet at the top of the pump housing is located above the filter plate and is connected to the water inlet of the first spray arm. The second spray arm is arranged in the upper middle part of the box body and is connected to the second water outlet of the pump housing through a water supply pipe.

[0004] The above-mentioned water pump is an open centrifugal pump structure. Since the water pump is directly placed in the return water area to draw water, the return water path is very short. After the water flows into the pump casing, it is quickly distributed through the flow channel and then output. When a larger water flow rate is met, the impeller and the pump casing are easily matched to produce snail noise due to excessive local flow velocity. At the same time, due to the different pressure differences above and below the impeller, the impeller may move up and down, which will also generate noise, which not only affects the efficiency and life of the water pump, but also seriously affects the user experience. Summary of the invention

[0005] The first technical problem to be solved by the present invention is to provide a water pump for a cleaning machine that can reduce noise, improve water pump efficiency and life while meeting the water pumping flow rate in view of the current status of the prior art.

[0006] The second technical problem to be solved by the present invention is to provide a cleaning machine using the above-mentioned water pump in view of the current status of the prior art.

[0007] The technical solution adopted by the present invention to solve the above technical problems is:

[0008] A water pump for a cleaning machine comprises a pump casing and an impeller rotatably arranged in the pump casing, a side portion of the pump casing is provided with a water outlet channel extending in a circumferential spiral, a baffle is formed at a throat where the water outlet channel is connected to the pump casing, the impeller and the inner side of the baffle form a high-pressure area for pressurizing the water flow, and the upper surface of the impeller is provided with a back blade that can cooperate with the baffle to balance the axial force and / or radial force of the impeller.

[0009] Preferably, the distance between the outer edge of the impeller and the tongue is 5 to 7.5 mm, more preferably 6.5 to 7.5 mm. By constraining this distance, the worm noise can be effectively reduced on the basis of meeting the water flow of the water pump, thereby improving the efficiency and life of the water pump and greatly improving the user experience.

[0010] Preferably, the impeller is a disc-shaped centrifugal impeller, comprising an upper cover plate and a lower cover plate spaced apart from each other, and water-drawing blades located between the upper cover plate and the lower cover plate, and the back blades and the water-drawing blades are staggered in the vertical direction.

[0011] Preferably, the height of the water-drawing blade in the vertical direction is 6 to 8 mm. The height of the back blade in the vertical direction is 0.8 to 3 mm, and more preferably 0.8 to 1.5 mm.

[0012] Preferably, the water-drawing blade and / or back blade comprises a first part extending from the central part of the impeller to the edge and a second part inclined along the circumference of the impeller from the outer end of the first part. This structure is conducive to improving the water-drawing effect.

[0013] Preferably, the first portion and the second portion are both straight line segments, and the acute angle a formed by the bending of the second portion relative to the first portion is 20 to 40 degrees, more preferably 25 to 35 degrees.

[0014] Preferably, the ratio of the length L2 of the second part to the length L1 of the first part is 0.2-0.6. The acute angle a formed by the bending of the second part relative to the first part is 30 degrees, and the ratio of the length L2 of the second part to the length L1 of the first part is 1:3 or 1:4. When a is 30 degrees and L2 / L1=1:3, the water pumping efficiency can be significantly improved; when a is 30 degrees and L2 / L1=1:4, the noise can be significantly reduced and the effect of the axial force can be reduced.

[0015] Preferably, a water inlet for the first part of the water-drawing blade is opened in the central portion of the lower cover plate, and the second part of the water-drawing blade extends obliquely in the direction of the water flow relative to the first part. Preferably, the first part of the water-drawing blade extends obliquely from the inner end to the outer end against the direction of the water flow, so that the junction between the first part and the second part of the water-drawing blade forms a water scooping structure. Preferably, the first part of the water-drawing blade is inclined at an angle of 25 to 35 degrees against the direction of rotation of the impeller. The above structures are all conducive to improving the water-drawing effect of the blades and improving the efficiency of the water pump.

[0016] Preferably, the water-drawing blades are an even number and are evenly distributed along the circumference of the centrifugal impeller. The even number of water-drawing blades can cooperate with the inner wall of the pump casing in the pump casing to balance the water-drawing force in the circumferential direction, thereby improving the running stability of the water pump.

[0017] A cleaning machine comprises a box body, a concave water return area is arranged at the bottom of the box body, and also comprises the above-mentioned water pump, which is arranged in the water return area.

[0018] Preferably, a slag collecting basket and a heating element are also provided in the return water area. From a top view, the water pump, slag collecting basket and heating element are arranged in a herringbone structure, and the side walls of the return water area are enclosed in the periphery of the herringbone structure, wherein the water pump is provided with a water outlet offset relative to the center of the pump casing and the water outlet extends to the central part of the herringbone structure. The return water area is a triangular structure with a smooth corner transition, including a first straight edge, a second straight edge and a third straight edge connected end to end, and each straight edge is smoothly connected at the intersection by an arc segment. The return water area is arranged in the center of the bottom of the box body, and the water pump is offset relative to the center of the bottom wall of the box body, and the water outlet of the water pump is arranged corresponding to the central part of the bottom of the box body. The return water area of ​​the existing washing machine is semicircular in shape as a whole. Considering that the spray arm needs to be arranged in the center relative to the box body in order to better cover the tableware cleaning range, the return water area needs to be offset on the bottom wall of the box body, and the debris collecting basket located next to the spray arm is also offset on the bottom wall of the box body. During the return water process, the ideal effect is that the return water enters the return water area after filtering the residue through the debris collecting basket, and then is further drawn into the spray arm through the water suction port of the open water pump in the return water area. However, since the debris collecting basket is offset too far from the bottom wall of the box body, the return water enters the return water area before flowing to the debris collecting basket, resulting in poor debris collection effect and residue retention problems on the filter plate. At the same time, the structure of the return water area of ​​the existing cleaning machine determines that the heating element located beside the water pump is also offset on the bottom wall of the box. In order to improve the heating efficiency, it is necessary to make the heating element have a corresponding return water area. This requires the return water area to have a volume that meets the installation requirements of the heating element and the slag collection basket, which makes it difficult to reduce the total volume of the return water chamber, resulting in a certain amount of water waste, affecting the water efficiency of the cleaning machine. The present invention sets the return water area as a triangular structure, and uses each corner area of ​​the triangular structure to install the water pump, the slag collection basket, and the heating element, and then guides the outlet water to the remaining space in the central part of the triangular structure through the offset outlet of the water pump, so as to maximize the use of the space of the return water area, which not only greatly reduces the volume of the return water area, which is beneficial to saving the amount of washing water each time, but also helps to improve the return water speed and water efficiency; because the water pump no longer occupies the central part of the bottom of the cleaning machine, the slag collection basket can be closer to the central part of the bottom of the cleaning machine, which is beneficial to improve the slag collection effect.

[0019] Compared with the prior art, the advantages of the present invention are: a baffle is formed at the throat where the water outlet channel extending along the circumferential spiral is connected to the pump casing, and the impeller and the inner side of the baffle form a high-pressure area for pressurizing the water flow. This structure can pressurize the outlet water to increase the water pressure and head, thereby improving the water pumping efficiency on the basis of satisfying the water intake flow rate; since the local flow velocity in the high-pressure area is too high, snail noise is easily generated, and the pressure difference between the upper and lower parts of the impeller is large, the impeller is prone to axial and radial shaking under a large pressure difference, resulting in a lot of noise and affecting the efficiency. The present invention provides a back blade on the back of the impeller to balance the axial force of the impeller. At the same time, the distance between the impeller and the baffle is constrained within a specific range. The control of the local flow velocity within this range is combined with the back blade to strengthen the radial balancing force of the impeller, thereby making the impeller rotate stably, while reducing noise, further improving the water pumping efficiency, avoiding the interference of the impeller shaking with the pump casing, and improving the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a diagram showing the matching of the impeller and the pump casing in an embodiment of the present invention (the upper half of the casing is hidden);

[0021] Figure 2 It is a schematic diagram of the structure of a water pump in an embodiment of the present invention;

[0022] Figure 3 for Figure 2 Schematic diagram of the bottom structure;

[0023] Figure 4 Schematic diagram of the structure of the impeller in the embodiment of the present invention;

[0024] Figure 5 for Figure 4 Schematic diagram of the bottom structure;

[0025] Figure 6 for Figure 4 A cross-sectional view of

[0026] Figure 7 Schematic diagram of the structure of a cleaning machine in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings.

[0028] The water pump used for the cleaning machine in this embodiment is an open water pump, that is, the water pump is installed in the return water area of ​​the cleaning machine, and no external pipeline is required to guide water. The water in the return water area directly flows back through the water pump and the spray arm.

[0029] like Figures 1 to 7As shown, the water pump 3 of this embodiment includes a pump housing 31 and an impeller 4 rotatably arranged in the pump housing 31. The side of the pump housing 31 is provided with a water outlet channel 32 extending in a circumferential spiral. The throat where the water outlet channel 32 is connected to the pump housing 31 forms a tongue 30. The distance d between the outer edge of the impeller 4 and the tongue 30 is 5 to 7.5 mm, preferably 6.5 to 7.5 mm. If the matching clearance between the outer edge of the impeller 4 and the tongue 30 is too large, it will cause a small water flow rate and a low head; if the matching clearance between the outer edge of the impeller 4 and the tongue 30 is too small, it will not only reduce the efficiency of the pump, but also cause cavitation in the small gap due to the high water pressure in the pump housing 31, resulting in a large local flow velocity and noise. In this embodiment, the distance between the outer edge of the impeller 4 and the tongue 30 is preferably 6.5 to 7.5 mm, which can not only meet the requirements of a water pump flow rate of 40 L / min and a head of 2 meters, but also effectively reduce the worm noise and improve the user experience.

[0030] The pump housing 31 of this embodiment includes a disc-shaped body, with a water inlet 311 at the bottom of the pump housing 31 and a water outlet 312 at the top. The water inlet 311 is opened in the central part of the bottom wall of the body. The end of the water outlet channel 32 is connected to a water guide pipe 33 extending upward, and the upper end of the water guide pipe 33 forms a water outlet 312 offset relative to the center of the pump housing 31. The water outlet 312 can be connected to a spray arm to spray from bottom to top at the bottom of the washing chamber. The spirally extended water outlet channel 32 offsets the water outlet 312 relative to the center of the water pump 3, so as to facilitate the central arrangement of the water outlet and the spray arm connected to the water outlet when the water pump 3 is not centered relative to the washing chamber.

[0031] The impeller 4 of this embodiment is a disc-shaped centrifugal impeller, which is arranged concentrically with the water inlet 311 .

[0032] In this embodiment, the impeller 4 and the inner side of the baffle 30 form a high-pressure area 300 for pressurizing the water flow, and the upper surface of the impeller 4 is provided with a back blade 44 for balancing the axial and radial forces of the impeller 4. The impeller 4 includes an upper cover plate 41 and a lower cover plate 42 arranged at intervals from top to bottom, and a water-drawing blade 43 located between the upper cover plate 41 and the lower cover plate 42. The back blade 44 and the water-drawing blade 43 are staggered in the upper and lower directions. The back blade 44 is arranged in the area corresponding to the two adjacent water-drawing blades 43. With such a structure, the axial force of the impeller can be balanced to the maximum extent without greatly affecting the efficiency of the pump. After the axial force is balanced, the wear on the pump casing 31 can be reduced, so that the lower string of blades will not be worn to the lower pump casing in a long-term use environment.

[0033] The height h1 of the water-drawing blade 43 in the vertical direction is 6 to 8 mm. The height h2 of the back blade 44 in the vertical direction is 0.8 to 3 mm, and more preferably 0.8 to 1.5 mm. Such parameter design is adopted to balance the impeller axial force to the maximum extent within a more preferred and reasonable range, while ensuring that the pump has a high water-drawing efficiency.

[0034] The water-drawing blade 43 and the back blade 44 include a first portion 401 extending from the central part of the impeller to the edge and a second portion 402 inclined along the circumference of the impeller from the outer end of the first portion 401. This structure is conducive to improving the water-drawing effect.

[0035] The first portion 401 and the second portion 402 are both straight segments, and the acute angle a formed by the second portion 402 bending relative to the first portion 401 is 20 to 40 degrees, and more preferably 25 to 35 degrees.

[0036] The ratio of the length L2 of the second part 402 to the length L1 of the first part 401 is 0.2 to 0.6. The acute angle a formed by the second part 402 relative to the first part 401 is 30 degrees, and the ratio of the length L2 of the second part 402 to the length L1 of the first part 401 is 1:3 or 1:4. When a is selected to be 30 degrees and L2 / L1=1:3, the water pumping efficiency can be significantly improved; when a is selected to be 30 degrees and L2 / L1=1:4, the noise can be significantly reduced and the effect of the axial force can be reduced.

[0037] The central part of the lower cover plate 42 is provided with a water inlet 45 arranged for the first part 401 of the water-drawing blade 43, and the water inlet 45 is arranged corresponding to the water inlet 311. The second part 402 of the water-drawing blade 43 extends obliquely in the direction of the water flow relative to the first part 401. The first part 401 of the water-drawing blade 43 extends obliquely from the inner end to the outer end against the direction of the water flow, so that the connection between the first part 401 and the second part 402 of the water-drawing blade 43 forms a scooping structure 403. The angle b of the first part 401 of the water-drawing blade 43 inclining against the direction of rotation of the impeller is 25 to 35 degrees. The above structures are all conducive to improving the water-drawing effect of the blades and improving the efficiency of the water pump.

[0038] The water-drawing blades 43 are an even number and are evenly distributed along the circumference of the centrifugal impeller. The even number of water-drawing blades 43 can cooperate with the inner wall of the pump housing 31 in the pump housing 31 to balance the water-drawing force in the circumferential direction, thereby improving the running stability of the water pump.

[0039] The cleaning machine of this embodiment comprises a housing 1 , a concave water return area 11 is arranged at the bottom of the housing 1 , and the water pump 3 is arranged in the water return area 11 .

[0040] The return water area 11 is also provided with a slag collection basket 411 and a heating element 5. From a top view, the water pump 3, the slag collection basket 411 and the heating element 5 are arranged in a herringbone structure. The side walls of the return water area 11 are enclosed in the periphery of the herringbone structure, wherein the water outlet 312 of the water pump is an offset water outlet 312 and extends to the central part of the herringbone structure. The return water area 11 is a triangular structure with a smooth corner transition, including a first straight edge, a second straight edge and a third straight edge connected end to end, and each straight edge is smoothly connected at the intersection by an arc segment. The return water area 11 is arranged in the center of the bottom of the box body 1, and the water pump is offset relative to the center of the bottom wall of the box body 1. The water outlet 312 of the water pump is arranged corresponding to the central part of the bottom of the box body 1. The return water area of ​​the existing washing machine is semicircular in shape as a whole. Considering that the spray arm needs to be arranged in the center relative to the box body in order to better cover the tableware cleaning range, the return water area needs to be offset on the bottom wall of the box body, and the debris collecting basket located next to the spray arm is also offset on the bottom wall of the box body. During the return water process, the ideal effect is that the return water enters the return water area after filtering the residue through the debris collecting basket, and then is further drawn into the spray arm through the water suction port of the open water pump in the return water area. However, since the debris collecting basket is offset too far from the bottom wall of the box body, the return water enters the return water area before flowing to the debris collecting basket, resulting in poor debris collection effect and residue retention problems on the filter plate. At the same time, the structure of the return water area of ​​the existing cleaning machine determines that the heating element located next to the water pump is also offset on the bottom wall of the box. In order to improve the heating efficiency, it is necessary to have a corresponding return water area above the heating element. This requires the return water area to have a volume that meets the installation requirements of the heating element and the slag collection basket, which makes it difficult to reduce the total volume of the return water chamber, resulting in a certain amount of water waste, affecting the water efficiency of the cleaning machine. The "central arrangement" and "offset" mentioned in the present invention refer to the horizontal position relationship of each component from a top-down perspective, and do not involve the vertical height. The present invention sets the return water area 11 as a triangular structure, and uses each corner area of ​​the triangular structure to install a water pump, a slag collecting basket 411, and a heating element 5, and then guides the outlet water to the remaining space in the central part of the triangular structure through the offset water outlet 312 of the water pump, thereby making maximum use of the space of the return water area 11, which not only greatly reduces the volume of the return water area 11, which is beneficial to saving the amount of washing water each time, but also helps to improve the return water speed and water efficiency; because the water pump no longer occupies the central part of the bottom of the cleaning machine, the slag collecting basket 411 can be closer to the central part of the bottom of the cleaning machine, which is beneficial to improving the slag collecting effect.

[0041] In this embodiment, a water outlet channel 32 extending along the circumferential spiral is connected to the throat of the pump casing 31 to form a baffle 30. The impeller 4 and the inner side of the baffle 30 form a high-pressure area 300 for pressurizing the water flow. This structure can pressurize the outlet water to increase the water pressure and head, thereby improving the water pumping efficiency on the basis of satisfying the water intake flow rate. Since the local flow velocity in the high-pressure area 300 is too high, snail noise is easily generated, and the pressure difference between the upper and lower parts of the impeller 4 is large, the impeller 4 is prone to axial and radial shaking under the large pressure difference, resulting in a lot of noise and affecting the efficiency. In this embodiment, a back blade 44 is provided on the back of the impeller 4 to balance the axial force of the impeller 4. At the same time, the distance between the impeller 4 and the baffle 30 is constrained within a specific range. The control of the local flow velocity within this range is combined with the back blade 44 to strengthen the radial balancing force on the impeller 4, thereby making the impeller 4 rotate stably. While reducing noise, the water pumping efficiency is further improved, and the interference between the impeller shaking and the pump casing is avoided, thereby increasing the service life.

[0042] In the specification and claims of the present invention, terms indicating directions, such as "front", "rear", "up", "down", "left", "right", "side", "top", "bottom", etc., are used to describe various exemplary structural parts and elements of the present invention, but these terms are used here only for the purpose of convenience of description and are determined based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in the present invention can be arranged in different directions, these terms indicating directions are only used as explanations and should not be regarded as limitations. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

Claims

1. A water pump for a cleaning machine, comprising a pump housing (31) and an impeller (4) rotatably arranged in the pump housing (31), characterized in that: The pump housing (31) is provided with a water outlet channel (32) extending in a circumferential spiral on the side thereof, and a baffle (30) is formed at the throat where the water outlet channel (32) is connected to the pump housing (31). The impeller (4) and the inner side of the baffle (30) form a high-pressure area (300) for pressurizing the water flow, and the upper surface of the impeller (4) is provided with a back blade (44) that can cooperate with the baffle (30) to balance the axial force and / or radial force of the impeller (4).

2. The water pump for a cleaning machine according to claim 1, characterized in that: The distance (d) between the outer edge of the impeller (4) and the partition tongue (30) is 5 to 7.5 mm.

3. The water pump for a cleaning machine according to claim 2, characterized in that: The distance (d) between the outer edge of the impeller (4) and the partition tongue (30) is 6.5 to 7.5 mm.

4. The water pump for a cleaning machine according to claim 1, 2 or 3, characterized in that: The impeller (4) is a disc-shaped centrifugal impeller, comprising an upper cover plate (41), a lower cover plate (42) arranged at intervals from top to bottom, and a water-drawing blade (43) located between the upper cover plate (41) and the lower cover plate (42), wherein the back blade (44) and the water-drawing blade (43) are arranged staggered in the upper and lower directions.

5. The water pump for a cleaning machine according to claim 4, characterized in that: The height of the water-drawing blade (43) in the vertical direction is 6 to 8 mm, and the height of the back blade (44) in the vertical direction is 0.8 to 3 mm.

6. The water pump for a cleaning machine according to claim 4, characterized in that: The water-drawing blade (43) and / or the back blade (44) comprises a first part (401) extending from the central part to the edge of the impeller and a second part (402) inclined along the circumference of the impeller from the outer end of the first part (401).

7. The water pump for a cleaning machine according to claim 6, characterized in that: The first part (401) and the second part (402) are both straight line segments, and the acute angle formed by the bending of the second part (402) relative to the first part (401) is 20 to 40 degrees.

8. The water pump for a cleaning machine according to claim 7, characterized in that: The ratio of the length L2 of the second portion (402) to the length L1 of the first portion (401) is 0.2 to 0.

6.

9. The water pump for a cleaning machine according to claim 8, characterized in that: The acute angle formed by the bending of the second part (402) relative to the first part (401) is 30 degrees, and the ratio of the length L2 of the second part (402) to the length L1 of the first part (401) is 1:3 or 1:

4.

10. The water pump for a cleaning machine according to claim 6, characterized in that: The lower cover plate (42) has a water inlet (45) at the central portion thereof arranged corresponding to the first portion (401) of the water-drawing blade (43), and the second portion (402) of the water-drawing blade (43) extends obliquely toward the direction of water flow relative to the first portion (401).

11. The water pump for a cleaning machine according to claim 6, characterized in that: The first part (401) of the water-drawing blade (43) extends obliquely from the inner end to the outer end in the opposite direction of the water flow, so that the connection between the first part (401) and the second part (402) of the water-drawing blade (43) forms a water scooping structure (403).

12. The water pump for a cleaning machine according to claim 6, characterized in that: The first part (401) of the water-drawing blade (43) is inclined at an angle of 25 to 35 degrees in the direction opposite to the rotation direction of the impeller.

13. A cleaning machine, comprising a housing (1), wherein a concave water return area (11) is provided at the bottom of the housing (1), characterized in that: It also comprises the water pump according to any one of claims 1 to 12, wherein the water pump is arranged in the water return area (11).

14. The cleaning machine according to claim 13, characterized in that: The return water area (11) is also provided with a slag collecting basket (411) and a heating element (5). When viewed from a top view, the water pump, the slag collecting basket (411) and the heating element (5) are arranged in a herringbone structure, and the side wall of the return water area (11) is surrounded by the periphery of the herringbone structure. The water pump is provided with a water outlet (312) offset relative to the center of the pump housing, and the offset water outlet (312) extends to the central part of the herringbone structure.

15. The cleaning machine according to claim 14, characterized in that: The water return area (11) is a triangular structure with a smooth transition at the corner, comprising a first straight side, a second straight side, and a third straight side connected end to end, and each straight side is smoothly connected through an arc segment at the intersection.

16. The cleaning machine according to claim 15, characterized in that: The water return area (11) is arranged in the center of the bottom of the box body (1), the water pump is offset relative to the center of the bottom wall of the box body (1), and the water outlet (312) of the water pump is arranged corresponding to the central part of the bottom of the box body (1).

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