JP5445337B2 - Water heater - Google Patents

Description

  The present invention relates to a water heater such as a water heater using gas, oil, or electricity as a heat source, or a heat pump water heater using atmospheric heat and electricity as a heat source.

  Conventionally, the shower device of this type of water heater is an energy-saving usage amount displayed or voiced on the remote controller when the shower flow rate detected when using the shower hot water supply is lower than the target flow rate set in advance. By notifying this, it is possible to notify the shower user whether or not the shower usage is the energy saving usage (see, for example, Patent Document 1).

  FIG. 12 shows how hot water comes out of the shower head 45 when using a conventional shower. The left figure of the same figure is the figure which looked at the shower head 45 from the side which can see a hole. Holes (for example, 45a and 45b) through which hot water is discharged are opened.

  The right figure of the figure shows a part where the hot water from the shower head hits a part of the trajectory until it hits the body. The hot water coming out of the left figure holes 45a and 45b hits the right figure points A and B. Similarly, the hot water discharged from the other area corresponds to the point corresponding to the right figure, and in the case shown in FIG. 12, a large number of points are arranged on two concentric circles as shown in the figure.

JP 2009-24913 A

  However, in the conventional configuration, the target value of the shower hot water supply flow rate should be simply set to a flow rate equal to or lower than the shower flow rate (the user's favorite flow rate) normally used by the shower user. Since it is less than the user's preferred flow rate, the shower user will endure and use it.

  Also, if the shower head is fixed, the position where the hot water from the shower head hits the body is constant, so it becomes a passive stimulus for human touch, and the intensity of the stimulus is felt weak due to adaptation. Come. For this reason, there has been a problem of comfort that the shower feels unsatisfactory.

  Moreover, simply lowering the shower flow rate does not always allow the soap and shampoo after washing the body and hair to be sufficiently rinsed away. Usually, when the shower flow rate is small, the rinsing performance is lowered, and thus the rinsing performance is deteriorated.

  In addition, the amount of time spent rinsing soap and shampoo in the shower becomes longer because the rinsing performance has deteriorated. As a result, the amount used in a single shower does not decrease, and sometimes the amount used increases. There was a problem in energy saving and water saving effect.

  The present invention solves the above-mentioned conventional problems, and reduces water consumption step by step while changing the flow rate so that the water saving flow rate is smaller than the flow rate that is normally used, while maintaining the usability and An object is to provide a water heater that realizes energy saving.

  In order to solve the above-described conventional problems, a water heater according to the present invention includes a hot water supply pipe for supplying hot water to a tapping part, a flow rate adjusting means for adjusting a flow rate provided in the hot water supply pipe, and a control means. The flow rate adjusting means changes the amplitude and period of the flow rate of the hot water flowing through the hot water supply pipe so that the average flow rate of the hot water flowing through the hot water supply pipe decreases stepwise. is there.

  This makes it difficult to feel a change to a water-saving flow rate that is lower than the normal flow rate, and the position where the hot water from the shower head, which is a hot water outlet, hits the body constantly changes. Since it becomes an active stimulus, there is no decrease in the strength of the stimulus due to adaptation, and the area where hot water hits also increases, so it is possible to realize water saving and energy saving while maintaining comfort and rinsing even with water saving flow rate. it can.

  According to the present invention, there is provided a water heater that realizes water saving and energy saving while maintaining usability by reducing the flow rate step by step so that the water saving flow rate is smaller than the normal flow rate. Can be provided.

Configuration diagram of a water heater in Embodiment 1 of the present invention (A) Schematic top view of motor-operated valve in Embodiment 1 of the present invention (b) Side sectional view of the motor-operated valve Characteristic diagram showing the change in average flow rate with respect to the elapsed time of the water heater Explanatory drawing explaining the shower feeling with respect to the amplitude and frequency of the same flow rate change (A) The figure which shows the flow rate change of the period and amplitude of the 1st step with respect to the average flow rate of the water heater in Embodiment 1 of this invention (b) The flow rate change of the cycle and amplitude of the 2nd step with respect to the average flow rate of the water heater (C) The figure which shows the flow rate change of the period and amplitude of a 3rd step with respect to the average flow volume of the water heater Explanatory drawing of the location that hits the body of the hot water when using the water heater shower (A) Characteristic diagram showing change in rotation angle in Embodiment 1 of the present invention (b) Characteristic diagram showing relationship between change in rotation angle and flow rate shown in FIG. 7 (a) (A) Characteristic diagram showing the relationship between elapsed time and rotation angle in Embodiment 1 of the present invention (average flow rate: large, amplitude: small) (b) Characteristic diagram showing the relationship between the elapsed time and rotation angle ( (Average flow rate: medium, amplitude: medium) (c) Characteristic diagram showing the relationship between the elapsed time and the rotation angle (average flow rate: small, amplitude: large) (A) Characteristic diagram showing the relationship between the elapsed time and the flow rate in Embodiment 1 of the present invention (amplitude: small) (b) Characteristic diagram showing the relationship between the elapsed time and the flow rate (amplitude: medium) (c) A characteristic diagram showing the relationship between elapsed time and flow rate (amplitude: large) (A) Other characteristic diagrams showing the relationship between the elapsed time and the rotation angle in Embodiment 1 of the present invention (average flow rate: large, amplitude: small) (b) Other showing the relationship between the elapsed time and the rotation angle (C) Other characteristic diagrams showing the relationship between elapsed time and rotation angle (average flow rate: small, amplitude: large) (A) Other view showing relationship between elapsed time and flow rate in Embodiment 1 of the present invention (amplitude: small) (b) Other view showing relationship between elapsed time and flow rate (amplitude: medium) ( c) Diagram showing the relationship between the elapsed time and the flow rate (amplitude: large) Explanatory drawing of the place where it hits the body of hot water from a conventional shower head

1st invention is provided with the hot water supply pipe line which supplies hot water to a tapping part, the flow volume adjustment means provided in the said hot water supply pipe line, and a control means, The average flow volume of the hot water which flows through the said hot water supply pipe line The hot water heater is characterized in that the flow rate adjusting means changes the amplitude and period of the flow rate of the hot water flowing through the hot water supply pipe so that the flow rate is less than the normally used flow rate. Rinse performance is less likely to notice changes to the water-saving flow rate, and even when the water-saving flow rate is less than the normal flow rate, the location where hot water discharged from the hot water outlet such as a shower changes periodically changes. It has a water-saving effect without reducing the feeling of use, and it is not necessary to boil hot water as much as it saves water, thus reducing energy, so energy can be saved.

  According to a second aspect of the present invention, the hot water supply line is changed by changing the flow rate adjusting means so that the amplitude of the flow rate of the hot water flowing through the hot water supply line is larger than the previous time and the cycle is smaller than the previous time. It is characterized by decreasing the average flow rate of flowing hot water in stages, and even if the average flow rate decreases, the change is difficult to understand, so that the comfort can be improved.

  According to a third aspect of the invention, the flow rate adjusting means is connected to the valve body having a valve hole, the valve body housed in the valve body and having an opening, the drive shaft fixed to the valve body, and the drive shaft It is a motor-operated valve composed of a drive device, and it can easily realize a predetermined flow rate change rate for a predetermined period and amplitude, so that it is reliable to save water and improve comfort. High control is possible.

  The fourth aspect of the invention is characterized in that the rotational speed of the valve body when the amplitude is small is smaller than the rotational speed of the valve body when the amplitude is large, and the flow rate changes according to the period. It is possible to improve the performance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a configuration diagram of a water heater in the present embodiment. In the figure, the hot water supply apparatus of the present embodiment includes a heat source section 29 that heats water sent from a water supply pipe 31, a flow rate controller 22, and a hot water supply pipe 40. The flow rate controller 22 is provided in the hot water supply pipe 40 to determine a flow rate detecting means 43 for detecting the flow rate of hot water, a flow rate adjusting means 44 for adjusting the flow rate of hot water, and a reference flow rate that is an initial flow rate when using a shower. Signals from the reference flow rate setting means 46, the water saving flow rate setting means 47 for setting the water saving flow rate that is the average flow rate of the hot water actually used, the signals from the flow rate detection means 43, the reference flow rate setting means 46, and the water saving flow rate setting means 47. And the control means 23 for controlling the operation of the flow rate adjusting means 44.

  Further, a hot water supply terminal 42 such as a currant, a shower head 45 and the like are connected to the hot water supply pipe line 40 by piping. In the figure, a remote controller 9 is provided in the water heater, and the function of the water-saving flow rate setting means 47 is provided as one of the functions of the remote controller 9 of the water heater. Further, the flow rate adjusting means 44 is formed by an electric valve as shown in FIG. This electric valve can be controlled to a predetermined flow rate by driving the valve element with a motor such as a stepping motor and changing the cross-sectional area of the flow path.

  In the figure, a valve body 108 having an opening 106 is provided inside a valve main body 105 in which a valve seat 104 having a valve hole 103 is formed in the middle of a fluid passage 101 into which a fluid flows. Further, as will be described later, the electric drive device 110 includes a stepping motor and a plurality of gears, and is connected to the valve body 108 by a valve body drive shaft 109. The electric drive device 110 rotates the valve body 108 about the valve body drive shaft 109. The ratio of the penetrating area formed by the opening 106 and the valve hole 103 of the valve body 108 formed at this time is changed, and the flow rate of hot water entering from the fluid passage 101 is controlled and discharged from the fluid passage 102.

  Further, as shown in the figure as an example of the configuration of the electric drive device 110 described above, the rotation of the drive unit 111 such as a stepping motor is decelerated by a gear mechanism, and finally the valve body 108 is moved by the valve body drive shaft 109. It is a structure to rotate. In the figure, a three-stage gear mechanism is shown as an example of the drive mechanism. The first gear 112 is fixed to a drive shaft of a drive unit 111 such as a stepping motor.

  The second and third gears 113 and 114 are fixed coaxially. Similarly, the fourth and fifth gears 115 and 116 are fixed coaxially. The sixth gear 117 is fixed coaxially with the valve body drive shaft 109. Further, the first and second gears 112 and 113 perform the first gear, the third and fourth gears 114 and 115 perform the second gear, and the fifth and sixth gears 116 and 117 perform the third gear. It has become. The valve body is driven by a stepping motor, which is the drive unit 111, and is controlled so as to have a predetermined flow rate by changing the above-described cross-sectional area of the water flow path.

  About the hot water heater comprised as mentioned above, the operation | movement and an effect | action are demonstrated below. In FIG. 1, before the shower user takes a shower, the water-saving flow rate is set by operating the remote controller 9 having the function of the water-saving flow rate setting means 47. As the water-saving flow rate, the flow rate may be set directly, but the rate (water-saving rate) of decreasing with respect to a reference flow rate described later may be set.

  Here, the water saving rate is set. When the user of the shower sets the water saving rate, the control unit 23 moves the valve body of the electric valve that is the flow rate adjusting unit 44 to a predetermined position. As described later, the predetermined position is for providing a rotation allowance necessary to move (rotate) the valve body around the water-saving flow rate. For example, the predetermined position is a flow rate when the valve body of the motor-operated valve is fully opened. On the other hand, it is set at a position that is about 80 to 90%.

  When the shower hot water supply circuit is opened, the control means 23 measures the flow rate at that time using the signal detected by the flow rate detection means 43. Furthermore, the flow rate at the time when a predetermined time ΔT has elapsed since the flow rate detected by the flow rate detection means 43 is stabilized is determined as the reference flow rate that is the initial flow rate. This reference flow rate is the flow rate preferred by the shower user.

  The control means 23 calculates | requires water-saving flow volume from this determined reference | standard flow volume and the water-saving rate set previously. When the water saving rate is Z% and the reference flow rate is Rk, the water saving flow rate Rs is Rs = Rk × (1−Z / 100).

  Further, as will be described below, the control unit 23 controls the flow rate adjusting unit 44 to change the average value of the flow rate stepwise so as to change from the reference flow rate Rk to the water-saving flow rate Rs. FIG. 3 shows changes in the average flow rate of hot water with respect to the elapsed time after the start of shower hot water supply, with the elapsed time on the horizontal axis and the average flow rate of hot water supply on the vertical axis. In the figure, Rk is a reference flow rate, Rs is a water-saving flow rate, and Z is a water-saving rate. Shown that the shower is started at the elapsed time T1, the flow rate is stabilized after T2, and the reference flow rate is determined at the time T3 when a predetermined time ΔT has passed. When the reference flow rate is determined, the control means 23 adjusts the flow rate adjustment means 44 to control the cycle and amplitude of the hot water supply flow rate fluctuation, as shown in the figure, the first stage (elapsed time T3 to T4). ), The second stage (elapsed time T4 to T5), and the third stage (after the elapsed time T5), so that the average value of the hot water supply flow rate is gradually changed from the reference flow rate to the water-saving flow rate.

The relationship between the amplitude and period of fluctuation and the shower feeling when the average flow rate is different are as follows. In FIG. 4, the horizontal axis represents the amplitude of the flow rate change, and the vertical axis represents the frequency of the flow rate change (frequency = 1 / cycle), and represents the shower feeling at that time. For example, if the amplitude is the same and the frequency is increased (the period is decreased), the shower feels strong. Moreover, when the frequency is the same and the amplitude is increased, a change in strength is felt. In particular, how people feel about this change in strength varies widely from person to person. Therefore, if the amplitude is increased too much, the proportion of people who feel uncomfortable increases.

  The amplitude and frequency when the average flow rate is small are determined as follows with reference to the case where the average flow rate indicated by point A is large in FIG. When the flow rate is changed around the average flow rate, the maximum value of the flow rate change is set to be equal to the reference flow rate in order to make the shower feeling equal to the reference flow rate (preferred flow rate). Therefore, when the average flow rate is reduced, the amplitude of the flow rate change is increased. However, simply increasing the amplitude will naturally reduce the shower feeling because the flow rate is smaller than when the average flow rate is large. As shown in the figure, if the frequency is increased (the period is decreased) to the state of point B as much as it feels weak, even if the average flow rate is decreased, a shower feeling similar to that when the average flow rate is large can be obtained. it can.

  FIG. 5 shows the cycle and amplitude of fluctuations in the hot water flow rate at each stage in FIG. In the figure, the average flow rate decreases as the first stage, the second stage, and the third stage, and the period and amplitude of the first stage are Ts1, S1, and the period and amplitude of the second stage are Ts2, S2, and third. Let Ts and S be the period and amplitude of the steps. A dotted line in each stage indicates an average flow rate, and control is performed so that the flow rate varies around this average flow rate.

  As described with reference to FIG. 4, since the maximum value of the flow rate at each stage is the reference flow rate Rk, the amplitude control has a relationship of S1 <S2 <S. Further, increasing the frequency as the average flow rate is reduced has a relationship of Ts1> Ts2> Ts as the cycle control. Then, the control means 23 controls the valve body of the motor-operated valve, which is the flow rate adjusting means 44, to periodically open and close around the position of the average flow rate so that the relationship between the amplitude and the cycle is obtained.

  If the initial flow rate is changed from the reference flow rate to the water-saving flow rate at once, there is a relatively large change, and there may be a slightly uncomfortable feeling as a shower, but the average flow rate is stepped as shown in FIGS. The change is moderated by dropping it, and the period is initially set to be larger and the change is made smaller in steps, making it difficult to feel the change. That is, the comfort is improved as compared with the conventional case of simply reducing the flow rate.

  As one of the functions of the remote controller 9, the function of the water-saving flow rate setting means 47 is provided. Specifically, the water-saving rate input unit (not shown) and the value set in this water-saving rate input unit are set. There is a configuration including a display unit (not shown) for displaying. At this time, the shower user sets the water saving rate by operating the water saving rate input unit (for example, a numeric keypad input or a key that can be increased or decreased) while looking at the numerical value displayed on the display unit. Or you may set a water-saving rate using the dial or slide input part (not shown) with a numerical value (water-saving rate) display in the circumference | surroundings.

  Furthermore, it may be configured to select from two or more preset water saving rates without specifically setting the water saving rate. For example, the remote controller 9 is provided with a switch with a water saving rate of 20% being “large”, a water saving rate of 10% being “medium”, a water saving rate of 5% being “small”, and no water saving being “off”. For this purpose, four switches may be provided, or the setting contents may be changed in order each time the switch is pressed with one switch.

  As described above, the method of selecting the water saving rate from a plurality of preset water saving rates can easily select the desired water saving rate, and thus the convenience is improved. Further, it is possible to further improve convenience by providing a display unit on the remote controller 9 so as to know which of “large”, “medium”, “small”, and “off” is selected and displaying the selected state. In addition, you may display a selection state by the number which lights, such as LED.

  Furthermore, a display unit (not shown) may be provided on the remote controller 9 so that it can be selected on the menu screen. In the above description, the selection is made in four stages of “large”, “medium”, “small”, and “off”, but it may be more or less than this. Further, the two or more preset water saving rates may be fixed values in the water heater, or the shower user may change the water saving rate according to himself / herself by operating the remote controller. . In this way, the shower user's favorite shower feeling can be obtained, and the comfort can be further improved.

  FIG. 6 shows how hot water is discharged from the shower head 45 when the shower flow rate is periodically changed. The left figure of the same figure is the figure which looked at the shower head 45 from the side which can see a hole. Holes (for example, 45a and 45b) through which hot water flows out are opened. The right figure of the figure shows a part where the hot water coming out of the shower head 45 hits a part of the locus until it hits the body or the like. As described above, when the valve body of the motor-operated valve that is the flow rate adjusting means 44 is repeatedly opened and closed around the position of the average flow rate, the pressure of the hot water inside the shower head 45 changes accordingly. That is, when the valve body 108 is moved in the direction in which the flow path area decreases, the pressure inside the shower head 45 decreases.

  Conversely, when the valve body 108 is moved in the direction in which the flow path area increases, the pressure inside the shower head 45 increases. However, there is a time delay between the movement of the valve body 108 and the change in pressure. The trajectory of the hot water coming out of the shower head also changes according to this pressure fluctuation. The dotted line in the figure shows the locus of hot water coming out of the hole 45a of the shower head 45, and changes within the range indicated by the upper and lower dotted lines with the central dotted line as the center.

  And the part which hits a body becomes a substantially rectangle shown by A of the same figure. Similarly, the portion of the hot water coming out of the hole 5b that hits the body is substantially rectangular as indicated by B in FIG. The same applies to the hot water coming out of the other holes, and as a result, the area where hot water coming out of the shower head hits the body increases as compared with the case of the conventional example.

  In this way, when the shower flow rate is changed periodically, the area hitting the body increases, so that the shower feeling is maintained substantially equal to the case of a constant flow shower as in the conventional example of FIG. Furthermore, the performance of rinsing off soap and shampoo is maintained, and water saving effect is obtained. Further, since the amount of hot water to be heated is reduced as the amount of hot water used is reduced, there is also an energy saving effect.

  Note that in FIG. 5, in which the variation period and amplitude change with respect to the average flow rate of hot water supply are described, the maximum value of the change in flow rate and the reference flow rate are substantially equal, but the maximum value of the change in flow rate is the reference flow rate. It may be larger than. In this case, the strength of the shower is felt when it is near the maximum flow rate, and the shower feeling is maintained, so comfort is maintained.

  Next, the changing speed when changing the amplitude and frequency will be described. FIG. 7 shows the change in the flow rate of hot water relative to the rotation angle of the valve element, with the horizontal axis indicating the rotation angle of the valve element 108 having the valve element drive shaft 109 as the rotation axis and the vertical axis indicating the flow rate of hot water. It is. The rotation angle as the origin is a position where the flow rate is maximized at the position of the valve element 108 indicated by A in the figure, and the position where the opening 106 is a contrast to the fluid passage 101. .

Reference numerals 106 and 107 respectively denote an opening and a non-opening provided in the valve body 108. Further, the opening 106 has a first end face 118 and a second end face 119 at different positions in the rotation axis direction. There are two end faces. When the valve body 108 is rotated toward the valve body drive shaft 109 in the same rotational direction (CW) as the clock, the position of the valve body 108 shown in the upper part of the figure changes to A, B, C, D, and E. Return to the original A again. The flow rate change at this time corresponds to points A, B, C, D, and A in the lower diagram.

  As can be seen from the figure, the flow rate through the motor-operated valve is maximum between AB and EA, and minimum (closed) between CD. And in the rotation angle area | region between B-C (area | region 1 of the figure) and DE (area | region 2 of the figure), the flow volume has changed with respect to the rotation angle. That is, when performing flow rate control, the valve element 108 is rotated to either the region 1 or the region 2, and the stepping motor, which is the drive unit 111, is rotated so that a predetermined flow rate can be obtained. Let

  At this time, the rotational speed of the valve body 108 is proportional to the pulse speed input to the stepping motor, and the flow rate change speed is substantially proportional to the rotational speed of the valve body 108. Therefore, the flow rate change speed is proportional to the pulse speed input to the stepping motor. Therefore, the flow rate change speed can be controlled by controlling the pulse speed input to the stepping motor.

  FIG. 8 shows the rotation angle of the valve element 108 with respect to the elapsed time, with the elapsed time on the horizontal axis and the rotation angle of the valve element 108 on the vertical axis. The lower diagram shows a large amplitude (small average flow rate), the middle diagram shows a medium amplitude (average flow rate), and the upper diagram shows a small amplitude (large average flow rate). It is. The rotational speed of the valve body 108 is the same in the three cases.

  When the rotational speed control of the valve body 108 is controlled as shown in FIG. 8, the flow rate changes as shown in FIG. FIG. 9 shows the change in flow rate with respect to elapsed time, with the elapsed time on the horizontal axis and the flow rate on the vertical axis. Since the rotational speed of the valve body 108 is the same in the three cases of the upper, middle, and lower stages, as shown in the figure, the change rate of the flow rate is the same in the three cases.

  That is, the inclination angle θ of the flow rate change shown in FIG. In this case, when the amplitude of the lower stage is large, the flow rate change is a sine wave-like smooth change, but it can be seen that the change becomes a rectangular wave-like change as the amplitude becomes smaller. In the case of such a change rate of the flow rate, when taking a shower, the maximum flow rate and the minimum flow rate are alternately felt, and the change in the flow rate is felt greatly, and some people may feel uncomfortable.

  Therefore, as shown in FIG. 10, the flow rate change rate is changed according to the amplitude. FIG. 10 shows the rotation angle of the valve body 108 with respect to the elapsed time, with the elapsed time on the horizontal axis and the rotation angle of the valve body 108 on the vertical axis. The lower diagram shows a large amplitude (small average flow rate), the middle diagram shows a medium amplitude (average flow rate), and the upper diagram shows a small amplitude (large average flow rate). The rotational speed of the valve body 108 is smaller as the amplitude is smaller.

  When the rotational speed control of the valve body 108 is controlled as shown in FIG. 10, the flow rate changes as shown in FIG. FIG. 11 shows the change in flow rate with respect to elapsed time, with the elapsed time on the horizontal axis and the flow rate on the vertical axis. The smaller the amplitude, the smaller the rotational speed. Therefore, the smaller the amplitude, the smaller the change rate.

  That is, as shown in the figure, if the inclination angles of the flow rate changes corresponding to large, medium, and small amplitudes are θ, α, and β, a relationship of θ> α> β is established. Further, in this case, in the three cases of the lower, middle, and upper stages having different amplitudes, the change in the flow rate is a sinusoidal and smooth change. Thus, the smaller the amplitude is, the smaller the flow rate change rate is, and the more gradually the flow rate changes.

In the case of FIG. 2, since it is a three-stage gear mechanism, the drive unit 1 such as a stepping motor is used.
11 may be rotated in the direction opposite to the necessary rotation direction of the valve body 108. That is, when rotating the valve body in the same rotation direction (CW) as the watch, the rotation direction of the drive unit 111 is set to the opposite direction (CCW) to the rotation of the watch, and the valve body is set to the opposite direction (CCW) to the rotation of the watch. ), The rotation direction of the drive unit 111 is set to the same rotation direction (CW) as that of the watch. Further, in FIG. 3, the reference flow rate, which is the initial flow rate, is lowered from 3 steps to the water-saving flow rate, but the operation and effect are the same regardless of whether it is 2 steps or 4 steps or more.

  As described above, the water heater according to the present invention has a water-saving flow rate that achieves a predetermined water-saving rate with respect to the flow rate that the user wants to use, and the water-saving flow rate is the same as the flow rate that the user wants to use. Therefore, it can be used as a water-saving means as a single shower device or as a water heater incorporating the function of the shower device.

23 Control means 40 Hot water supply pipe 44 Flow rate adjustment means 46 Reference flow rate setting means 47 Water-saving flow rate setting means

Claims (4)

A hot water supply pipe that supplies hot water to the hot water supply section, a flow rate adjusting means that adjusts the flow rate provided in the hot water supply pipe, and a control means are provided, and the average flow rate of hot water flowing through the hot water supply pipe decreases stepwise. As described above, the water heater is characterized in that the flow rate adjusting means changes the amplitude and period of the flow rate of the hot water flowing through the hot water supply pipe. By changing the flow rate adjusting means so that the amplitude of the flow rate of the hot water flowing through the hot water supply pipe is larger than the previous time and the cycle is smaller than the previous time, the average flow rate of the hot water flowing through the hot water supply pipe line is increased. The water heater according to claim 1, wherein the water heater is decreased step by step. The flow rate adjusting means is composed of a valve body having a valve hole, a valve body housed inside the valve body and having an opening, a drive shaft fixed to the valve body, and a drive device connected to the drive shaft. The water heater according to claim 1 or 2, wherein the water heater is an electric valve. The water heater according to claim 2, wherein the rotation speed of the valve body when the amplitude is small is smaller than the rotation speed of the valve body when the amplitude is large.