US20140334941A1

US20140334941A1 - Pump apparatus

Info

Publication number: US20140334941A1
Application number: US14/184,344
Authority: US
Inventors: Yasuki Wada; Takayuki Tsujimoto
Original assignee: MATSUSAKA ENGINEERING Co Ltd
Current assignee: MATSUSAKA ENGINEERING Co Ltd
Priority date: 2013-05-11
Filing date: 2014-02-19
Publication date: 2014-11-13
Also published as: JP2014218988A; JP5491657B1; AU2014202092A1

Abstract

Provided is a pump apparatus capable of improving the performance in a wide operation range from an operation area with a low pressure and a high flow rate to an operation area with a high pressure and a low flow rate while suppressing a rated output of a motor used to drive a pump. A rotation speed of a motor 20 is controlled so that the rotation speed of the motor decreases with an increase in the load of the motor 20 driving a pump unit 10, the rotation speed thereof increases with a decrease in the load thereof, and the load does not exceed a predetermined upper limit. For this reason, it is possible to improve the performance in a wide operation range from an operation area with a low pressure and a high flow rate to an operation area with a high pressure and a low flow rate compared to a method of the related art of uniformly keeping a rotation speed of a motor.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a pump apparatus that includes a driving motor, and particularly, to a pump apparatus that improves the performance in an operation area with a high ejection pressure and a low flow rate.
2. Description of the Related Art
In general, a vortex centrifugal pump has a small load (power necessary for driving a rotation shaft) in an operation area with a high pressure and a small water quantity (in a case where a distance to a drainage place or a pump head is long or a discharge port is narrowed), but has a large load in an operation area with a low pressure and a large water quantity (see JP 2000-227084 A).

SUMMARY OF THE INVENTION

A motor that is used to drive a pump needs to be selected in consideration of the maximum power necessary for the operation. In a case of a vortex centrifugal pump, the pump has the above-described characteristics, and hence a motor is selected in consideration of a maximum load in a condition with a low pressure and a high flow rate. However, even when a large-power motor is selected in consideration of the condition with a low pressure and a high flow rate, the power is excessively large in a condition with a high pressure and a low flow rate. That is, although the large-power motor is selected, the power does not contribute to the improvement in the performance of the pump in an operation area with a high pressure and a low flow rate. For this reason, it is useless to prepare the large-power motor for that case.
The present invention is made in view of such circumstances, and an object thereof is to provide a pump apparatus capable of improving the performance in a wide operation range from an operation area with a low pressure and a high flow rate to an operation area with a high pressure and a low flow rate while suppressing a rated output of a motor used to drive a pump.
According to the present invention, since the rotation speed is controlled so that the rotation speed decreases with an increase in the load, the rotation speed increases with a decrease in the load, and the load does not exceed a predetermined upper limit, it is possible to improve the performance in a wide operation range from an operation area with a low pressure and a high flow rate to an operation area with a high pressure and a low flow rate while suppressing a rated output of a motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of an appearance of a pump apparatus according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating the internal configuration of a pump unit of the pump apparatus illustrated in FIG. 1;

FIG. 3 is a diagram illustrating an example of a control system of the pump apparatus according to the embodiment of the present invention;

FIG. 4 is a graph illustrating a relation between a throttle opening degree and a rotation speed;

FIG. 5 is a flowchart illustrating a rotation speed control operation from a pump start-up timing to a pump stop timing;

FIG. 6 is a flowchart illustrating an operation involving with the control of a target rotation speed;

FIG. 7 is a diagram illustrating an example in which the target rotation speed is controlled so as to approach a relation between a predetermined load and a rotation speed;

FIG. 8 is a flowchart illustrating an operation in a case where a load exceeds an upper-limit value;

FIG. 9 is a flowchart illustrating an operation in a case where a load is smaller than an upper-limit value and a target rotation speed is slower than the minimum rotation speed of FIG. 4;

FIG. 10 is a graph illustrating a relation between an ejection amount Q and a pump head H and a relation between an ejection amount Q and a throttle opening degree S; and

FIG. 11 is a flowchart illustrating a rotation speed control operation of a pump apparatus according to the other embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a diagram illustrating an example of an appearance of a pump apparatus according to an embodiment of the present invention. The pump apparatus illustrated in FIG. 1 includes a pump unit 10 and a motor 20. The pump unit 10 and the motor 20 are fixed to a frame 5.
The motor 20 illustrated in FIG. 1 is an engine as an internal-combustion engine. In order to obtain a target rotation speed, the motor (engine) 20 includes a unit (electronic governor or the like) that controls an opening degree (throttle opening degree) of a throttle valve disposed in a suction path.
The pump unit 10 illustrated in FIG. 1 is a vortex centrifugal pump. FIG. 2 illustrates an example of the internal configuration of the pump unit 10. The pump unit 10 includes an impeller 14 that is coupled to a rotation shaft 21 of the motor 20 and a volute casing 13 that accommodates the impeller 14. When the impeller 14 rotates, water (fluid) of a suction port 11 is carried to an ejection port 12 through the volute casing 13.
The pump unit 10 is, for example, a self-priming pump, and may start a pumping operation even in a state where air is accumulated in a suction-side pipe in a manner such that the pump unit is started up while priming water is present therein. A water charging lid 15 is used to charge priming water into the pump unit 10 at the start-up timing.
FIG. 3 is a diagram illustrating a configuration example of a control system of the pump apparatus according to the embodiment of the present invention.
In the example of FIG. 3, the pump apparatus includes a rotation speed detection unit 30 that detects the rotation speed of the motor 20, a load detection unit 40 that detects the load (the power necessary for driving the rotation shaft 21) of the motor 20, and a controller 50.
For example, the rotation speed detection unit 30 converts a variation in magnetic flux of a magnet rotating along with a gear inside the motor 20 into a pulse signal by a hall sensor and detects the rotation speed based on the frequency of the pulse signal.
The load detection unit 40 is, for example, a sensor that detects the opening degree (throttle opening degree) of the throttle valve disposed in the suction path of the motor 20 as the signal involving with the load of the motor 20. This sensor includes, for example, a potentiometer.
The controller 50 is a unit that controls the operation of the motor 20 and includes, for example, a micro computer. The controller 50 performs a control so that an appropriate rotation speed is obtained in response to the load state by driving an actuator for controlling a choke valve or a throttle valve of the motor 20 in response to the signal of the rotation speed detection unit 30 or the load detection unit 40.
The controller 50 includes a rotation speed controller 51 and a target rotation speed controller 52 as the functional components involving with the control of the rotation speed.
The rotation speed controller 51 controls the rotation speed of the motor 20 so that the rotation speed detected by the rotation speed detection unit 30 approaches a target rotation speed Rt.
The target rotation speed controller 52 controls the target rotation speed Rt in response to the load detection value (throttle opening degree S) of the load detection unit 40 so that a relation between the load and the rotation speed of the motor 20 approaches a predetermined relation (FIG. 4).
FIG. 4 is a graph illustrating a relation between a throttle opening degree S and a rotation speed Ra. The rotation speed Ra of FIG. 4 indicates the rotation speed of the motor 20 that is determined for the throttle opening degree S detected by the load detection unit 40. In the example of FIG. 4, the rotation speed Ra is determined so that the rotation speed decreases substantially in proportional to the throttle opening degree S. The throttle opening degree S includes, for example, a numerical range from “0” to “95”, where “0” indicates a state where the throttle valve is fully closed and “95” indicates a state where the throttle valve is fully opened.
The target rotation speed controller 52 may calculate the value of the rotation speed Ra corresponding to the throttle opening degree S based on, for example, a predetermined calculation formula or may read out the value from a data table representing in which the relation between the throttle opening degree S and the rotation speed Ra and stored in a storage unit.
The target rotation speed controller 52 controls the target rotation speed Rt so as to approach the relation between the throttle opening degree S and the rotation speed Ra illustrated in FIG. 4. That is, the target rotation speed controller 52 controls the target rotation speed Rt so that the rotation speed becomes slow when the load of the motor 20 increases and the rotation speed becomes fast when the load thereof decreases. Further, the target rotation speed controller 52 controls the target rotation speed Rt so that the load of the motor 20 does not exceed a predetermined upper-limit value (throttle opening degree S=80).
Further, in a case where a signal is input to the controller 50 from a switch (not illustrated) that instructs the start-up of the pump unit 10, the target rotation speed controller 52 sets the target rotation speed Rt (for example, 4000 rpm) for the self-priming operation, which is faster than the maximum rotation speed (3800 rpm) in the relation between the throttle opening degree S and the rotation speed Ra illustrated in FIG. 4, to the rotation speed controller 51 (the self-priming operation mode).
After the fast target rotation speed Rt for the self-priming operation is set to the rotation speed controller 51, the target rotation speed controller 52 compares the throttle opening degree S detected by the load detection unit 40 with a predetermined lower-limit value. When the throttle opening degree S exceeds the lower-limit value, the target rotation speed controller 52 switches the current mode from the self-priming operation mode of setting the fast target rotation speed Rt for the self-priming operation to the operation mode (the normal operation mode) of controlling the target rotation speed Rt so as to approach the relation between the throttle opening degree S and the rotation speed Ra illustrated in FIG. 4.
Here, in a case where the throttle opening degree S is smaller than the predetermined lower-limit value even when a predetermined time elapses after the target rotation speed Rt for the self-priming operation is set to the rotation speed controller 51, the target rotation speed controller 52 stops the rotation of the motor 20. Accordingly, it is possible to prevent the excessive load of the motor 20 and the pump unit 10 due to the fast rotation speed even when the self-priming operation mode is continued for a long period of time.
When the self-priming operation mode is switched to the normal operation mode, the target rotation speed controller 52 obtains a predetermined rotation speed Ra corresponding to the throttle opening degree S detected by the load detection unit 40 in the relation between the throttle opening degree S and the rotation speed Ra illustrated in FIG. 4, and calculates a difference DR between the rotation speed Ra and the target rotation speed Rt set to the rotation speed controller 51. The target rotation speed controller 52 compares the difference DR with a predetermined threshold value and sets a new target rotation speed Rt, which is close to the rotation speed Ra compared to the currently set target rotation speed Rt, to the rotation speed controller 51 when the difference DR exceeds the threshold value (the target rotation speed Rt is away from the rotation speed Ra). That is, the target rotation speed controller 52 sets the new target rotation speed Rt, which is included in the range from the rotation speed Ra to the current target rotation speed Rt and in which the difference between the rotation speed Ra and the new target rotation speed Rt is smaller than the current target rotation speed Rt, to the rotation speed controller 51. For example, the target rotation speed controller 52 sets a middle rotation speed in the range from the rotation speed Ra to the current target rotation speed Rt as the new target rotation speed Rt to the rotation speed controller 51 (FIG. 7).
In a case where the throttle opening degree S of the load detection unit 40 exceeds an upper-limit value (80) in the normal operation mode, the target rotation speed controller 52 decreases the target rotation speed Rt until the throttle opening degree S of the load detection unit 40 becomes smaller than the upper-limit value (80). For example, the target rotation speed controller 52 repeats a process, which decreases the target rotation speed Rt by a predetermined variation amount in response to the comparison result between the throttle opening degree S and the upper-limit value (80), until the throttle opening degree S becomes smaller than the upper-limit value (80). For example, a decrease in the target rotation speed Rt may be performed by subtracting a predetermined speed from the original speed or decreasing the entire speed by a predetermined ratio.
Next, the rotation speed control operation of the pump apparatus with the above-described configuration will be described with reference to a flowchart.
FIG. 5 is a flowchart illustrating the rotation speed control operation from the pump start-up timing to the pump stop timing.
When a signal is input to the controller 50 from a switch (not illustrated) that instructs the start-up of the pump unit 10 (ST105), the target rotation speed controller 52 sets the fast target rotation speed Rt for the self-priming operation to the rotation speed controller 51 (ST125). Accordingly, the pump apparatus starts the operation at the fast rotation speed for the self-priming operation (the self-priming operation mode).
On the other hand, the target rotation speed controller 52 switches the current routine to step ST140 below in a case other than the start-up of the pump (for example, a case of the restart operation or the like).
When the rotation speed of the motor 20 reaches the target rotation speed Rt for the self-priming operation by the control of the rotation speed controller 51, the target rotation speed controller 52 obtains the throttle opening degree S from the load detection unit 40 (ST130), and compares the throttle opening degree S with a predetermined lower-limit value (ST135). Since the load of the motor 20 is noticeably low during the self-priming operation, the throttle opening degree S becomes smaller than the lower-limit value.
In a case where the throttle opening degree S is smaller than the lower-limit value (the self-priming operation is continued), the target rotation speed controller 52 determines whether the time elapsing after the timing of setting the target rotation speed Rt for the self-priming operation to the rotation speed controller 51 reaches a predetermined time (ST180). In a case where the elapse time (the time of the self-priming operation mode) is shorter than the predetermined time, the target rotation speed controller 52 returns the current routine to step ST130 so as to repeat the determination on whether the throttle opening degree S exceeds the lower-limit value. In a case where the elapse time reaches the predetermined time, the target rotation speed controller 52 switches the current routine to step ST155 so as to stop the rotation of the motor 20. Accordingly, it is possible to prevent the excessive load of the motor 20 and the pump unit 10 when the fast rotation speed is continued for a long period of time in the self-priming operation mode.
When the throttle opening degree S becomes larger than the predetermined lower-limit value (the self-priming operation ends and the water pumping-up operation starts), the target rotation speed controller 52 switches the current mode to the normal operation mode. The target rotation speed controller 52 sets the target rotation speed Rt to a predetermined initial value (for example, 3600 rpm) (ST140), and starts to control the target rotation speed in response to the throttle opening degree S of the load detection unit 40 (ST145). When a signal is input to the controller 50 from a switch (not illustrated) that instructs the stop of the pump in the normal operation mode (ST150), the target rotation speed controller 52 stops the rotation of the motor 20.
FIG. 6 is a flowchart specifically illustrating the process in step ST145 of FIG. 5, and illustrates the operation involving with the control of the target rotation speed Rt in the normal operation mode.
The target rotation speed controller 52 obtains the throttle opening degree S from the load detection unit 40 (ST205), and determines whether the throttle opening degree S is larger than the upper-limit value (80) (ST210). In a case where the throttle opening degree S is larger than the upper-limit value (80), the target rotation speed controller 52 switches the current routine to step ST305 (FIG. 8) below. Further, the target rotation speed controller 52 determines whether the target rotation speed Rt currently set to the rotation speed controller 51 is slower than the minimum rotation speed (3600 rpm) in the graph illustrated in FIG. 4, and switches the current routine to step ST405 (FIG. 9) below in a case where the current target rotation speed Rt is slower than the minimum rotation speed.
In a case where the throttle opening degree S is smaller than the upper-limit value (80) and the target rotation speed Rt is faster than the minimum rotation speed (3600 rpm) in the graph illustrated in FIG. 4, the target rotation speed controller 52 obtains the predetermined rotation speed Ra (FIG. 4) corresponding to the throttle opening degree S obtained in step ST205 (ST220), and calculates the difference DR between the target rotation speed Rt and the rotation speed Ra (ST225). Then, in a case where the difference DR is larger than the threshold value, the target rotation speed controller 52 sets a middle value between the target rotation speed Rt and the rotation speed Ra as a new target rotation speed Rt to the rotation speed controller 51 (ST235). In a case where the difference DR is smaller than the threshold value, the target rotation speed controller 52 keeps the currently set target rotation speed Rt.
FIG. 7 is a diagram illustrating an example of controlling the target rotation speed Rt so as to approach the relation between the load (throttle opening degree S) and the rotation speed illustrated in the graph of FIG. 4. The graph illustrated in FIG. 7 illustrates a part of the graph illustrated in FIG. 4. The points “P1” to “P3” of FIG. 7 illustrate the operation points of the motor 20 expressed by the throttle opening degree S and the target rotation speed Rt.
A rotation speed Ra1 that is set to correspond to a throttle opening degree S1 of the operation point P1 is faster than a target rotation speed Rt1 of the operation point P1, and the difference DR thereof is larger than the threshold value. For this reason, a middle value Rt2 between the rotation speed Ra1 and the target rotation speed Rt1 is set as a new target rotation speed (ST235).
Since the new target rotation speed Rt2 is faster than the original target rotation speed Rt1, the load of the motor 20 increases. For this reason, when the target rotation speed is changed from “Rt1” to “Rt2”, the throttle opening degree becomes “S2” larger than “S1”. That is, the new operation point P2 (S2, Rt2) moves in the right and up direction of the original operation point P1 (S1, Rt1). As illustrated in FIG. 7, the operation point P2 approaches the line of the graph representing the relation between the load (throttle opening degree S) and the rotation speed compared to the original operation point P1.
In the example of FIG. 7, the operation point moves from “P2” to “P3” by the further control of the target rotation speed Rt. As described above, the target rotation speed Rt3 of the operation point P3 is obtained as a middle value between the target rotation speed Rt2 and the rotation speed Rat corresponding to the throttle opening degree S2 of the operation point P2. The operation point P3 further approaches the line of the graph compared to the operation point P2.
In this way, the rotation speed of the motor 20 is controlled so that the rotation speed approaches the relation between the load and the rotation speed illustrated in the graph of FIG. 4 until the difference DR becomes smaller than a predetermined threshold value by the repeated processes of step ST205 to step ST235.
FIG. 8 is a flowchart illustrating an operation when the load (throttle opening degree S) detected by the load detection unit 40 exceeds the upper-limit value (80).
In step ST210 (FIG. 6), when it is determined that the throttle opening degree S is larger than the upper-limit value (80), the target rotation speed controller 52 determines whether the target rotation speed Rt set to the rotation speed controller 51 is faster than 3600 rpm (the minimum rotation speed in the graph illustrated in FIG. 4) (ST305). In a case where the target rotation speed Rt is slower than 3600 rpm, the target rotation speed controller 52 sets a new target rotation speed Rt, which is obtained by decreasing the target rotation speed Rt by a predetermined variation amount, to the rotation speed controller 51 (ST325).
On the other hand, in a case where the target rotation speed Rt is faster than 3600 rpm, the target rotation speed controller 52 sets the target rotation speed Rt to 3600 rpm (ST310). When the rotation speed of the motor 20 reaches 3600 rpm, the target rotation speed controller 52 obtains the throttle opening degree S of the load detection unit 40 again (ST315), and compares the throttle opening degree S with the upper-limit value (80) (ST320). In a case where the throttle opening degree S exceeds the upper-limit value (80) even when the rotation speed is set to 3600 rpm, the target rotation speed controller 52 sets a new target rotation speed Rt, which is obtained by decreasing the target rotation speed Rt by a predetermined variation amount, to the rotation speed controller 51 (ST325).
The target rotation speed Rt of the motor 20 decreases until the throttle opening degree S becomes smaller than the upper-limit value (80) by the repeated processes of step ST305 to step ST325 described above.
Furthermore, in the process illustrated in the flowchart of FIG. 8, the target rotation speed Rt immediately decreases to the minimum rotation speed (3600 rpm) in a case where the load (throttle opening degree S) exceeds the upper-limit value (80) at the rotation speed faster than the minimum rotation speed (3600 rpm) in the graph illustrated in FIG. 4. Accordingly, it is possible to shorten the time in which an excessive load is applied to the motor 20.
FIG. 9 is a flowchart illustrating an operation in a case where the load (throttle opening degree S) detected by the load detection unit 40 is smaller than the upper-limit value (80) and the target rotation speed Rt is slower than the minimum rotation speed (3600 rpm) of FIG. 4.
In this case, the target rotation speed controller 52 calculates the difference DS between the upper-limit value (80) and the throttle opening degree S detected by the load detection unit 40 (ST405), and determines whether the difference DS is larger than a predetermined threshold value (ST410). In a case where the difference DS is larger than the predetermined threshold value, the target rotation speed controller 52 sets a new target rotation speed Rt, which is obtained by increasing the target rotation speed Rt by a predetermined variation amount, to the rotation speed controller 51 (ST415). For example, an increase in the target rotation speed Rt may be performed by adding a predetermined speed to the original speed or increasing the entire speed by a predetermined ratio.
The target rotation speed Rt of the motor 20 increases until the difference DS between the throttle opening degree S and the upper-limit value (80) becomes smaller than a predetermined threshold value by the repeated processes of step ST405 to step ST415 described above.
FIG. 10 is a graph illustrating an example of the performance of the pump apparatus. The curves CV1 and CV2 represent a relation between an ejection amount Q and a pump head H, and the curve CV3 represents a relation between the ejection amount Q and the throttle opening degree S.
The curve CV1 indicated by the dotted line represents the characteristics in a case where the rotation speed of the motor is kept at a rated speed (3600 rpm), and the curve CV2 indicated by the solid line represents the characteristics in a case where it is controlled such that the relation between the load (throttle opening degree S) and the target rotation speed Rt approaches the relation illustrated in FIG. 4.
As understood from the comparison between the curves CV1 and CV2, the pump head H increases at the same ejection amount Q by the control of the target rotation speed Rt. Further, the load (throttle opening degree S) is limited so that the load does not exceed the upper-limit value (80) in an operation area in which the ejection amount Q is larger than 300 [liter/min].
As described above, according to the pump apparatus of the embodiment, the rotation speed of the motor 20 is controlled so that the rotation speed of the motor 20 decreases with an increase in the load of the motor 20 driving the pump unit 10, the rotation speed thereof increases with a decrease in the load thereof, and the load does not exceed a predetermined upper limit. For this reason, it is possible to improve the performance in a wide operation range from an operation area with a low pressure and a high flow rate to an operation area with a high pressure and a low flow rate compared to the method of the related art uniformly keeping the rotation speed of the motor as indicated by the graph of FIG. 10.
Further, according to the pump apparatus of the embodiment, since the rotation speed of the motor 20 in the self-priming operation mode during the start-up of the pump is set to be faster than the rotation speed of the motor 20 in the normal operation mode, it is possible to shorten the time until the practical pumping operation starts. Further, since the current mode is automatically switched to the normal operation mode when it is determined that the self-priming operation ends by the determination on whether the self-priming operation ends based on the load of the motor 20 (the throttle opening degree S), the pumping operation may be immediately started. Moreover, since the rotation of the motor 20 is stopped when the self-priming operation mode is continued for a predetermined time, it is possible to effectively prevent the excessive load of the motor 20 and the pump unit 10 from being continued for a long period of time due to the fast rotation speed for the self-priming operation.
Furthermore, the present invention is not limited to the above-described embodiment, and includes various modified examples.
FIG. 11 is a flowchart illustrating a rotation speed control operation in a pump apparatus according to the other embodiment of the present invention.
The flowchart illustrated in FIG. 11 is a flowchart in which step ST110 to step ST120 are additionally provided between step ST105 and step ST125 in the flowchart illustrated in FIG. 5.
In this case, the target rotation speed controller 52 sets a rotation speed (for example, 3600 rpm), which is slower than the fast rotation speed (for example, 4000 rpm) for the self-priming operation, as the initial target rotation speed Rt to the rotation speed controller 51 before setting the target rotation speed Rt to the fast rotation speed (for example, 4000 rpm) for the self-priming operation by receiving the input of the pump start-up signal (ST110). Then, the target rotation speed controller 52 obtains the throttle opening degree S of the load detection unit 40 at the initial rotation speed (ST115), and determines whether the throttle opening degree S is smaller than a predetermined lower-limit value (ST120). In a case where the throttle opening degree S is smaller than the lower-limit value, the target rotation speed controller 52 sets the target rotation speed Rt to the fast rotation speed for the self-priming operation (ST125).
In this way, according to the process of the flowchart of FIG. 11, since the rotation speed is changed to the fast rotation speed after the self-priming operation is confirmed at the comparatively slow rotation speed, the excessive load of the motor 20 and the pump unit 10 may be effectively prevented.
In the above-described embodiment, in a case where the difference DR between the target rotation speed Rt and the rotation speed Ra (FIG. 4) corresponding to the load detection value is larger than a predetermined threshold value in the normal operation mode in which the load detection value (throttle opening degree) is smaller than the upper-limit value (80), the middle rotation speed between the rotation speed Ra and the target rotation speed Rt is set to a new target rotation speed Rt (ST235, FIG. 6), but the present invention is not limited thereto. That is, the new target rotation speed Rt may be a rotation speed which is included in the range from the rotation speed Ra corresponding to the load detection value to the original target rotation speed Rt and in which the difference DR between the target rotation speed and the rotation speed Ra is smaller than that of the original target rotation speed Rt. For this reason, the new target rotation speed Rt is not limited to the middle value between the rotation speed Ra and the target rotation speed Rt as described above.
In the above-described embodiment, a case has been exemplified in which the pump unit 10 is the centrifugal pump, but the present invention is not limited thereto. Specifically, various pumps may be used as the pump unit of the present invention other than the centrifugal pump.
In the above-described embodiment, a case has been exemplified in which the motor 20 is the engine (reciprocating engine), but the present invention is not limited thereto. Specifically, various internal-combustion engines may be used as the motor of the present invention. For example, an electric motor may be used as the power source other than the internal-combustion engine.

Claims

What is claimed is:

1. A pump apparatus comprising:

a pump;

a motor that drives the pump;

a rotation speed detector that detects a rotation speed of the motor;

a rotation speed controller that controls the rotation speed of the motor so that the rotation speed detected by the rotation speed detector approaches a target rotation speed;

a load detector that detects a load of the motor; and

a target rotation speed regulator that regulates the target rotation speed in response to the load detection value of the load detector so as to approach a predetermined relation between the load and the rotation speed, the predetermined relation being set so that the rotation speed decreases in accordance with an increase in the load, the rotation speed increases in accordance with a decrease in the load, and an upper-limit value of the load is set,

wherein in a case where the target rotation speed regulator regulates the target rotation speed in response to the load detection value, the target rotation speed regulator calculates a difference between the target rotation speed set to the rotation speed controller and a predetermined rotation speed corresponding to the load detection value in the predetermined relation, and sets a new target rotation speed, which is included in the range from the predetermined rotation speed to the currently set target rotation speed and in which a difference between the new target rotation speed and the predetermined rotation speed is smaller than the calculated difference, to the rotation speed controller when the calculated difference exceeds a predetermined threshold value.

2. The pump apparatus according to claim 1,

wherein the target rotation speed regulator sets a middle rotation speed in the range from the predetermined rotation speed to the currently set target rotation speed as the new target rotation speed to the rotation speed controller.

3. A pump apparatus comprising:

a pump;

a motor that drives the pump;

a rotation speed detector that detects a rotation speed of the motor;

a load detector that detects a load of the motor; and

wherein the target rotation speed regulator sets a minimum rotation speed defined in the predetermined relation as the target rotation speed to the rotation speed controller when the load detection value exceeds the upper-limit value and the target rotation speed currently set to the rotation speed controller is faster than the minimum rotation speed, and decreases the target rotation speed by a predetermined variation amount until the load detection value becomes smaller than the upper-limit value when the load detection value exceeds the upper-limit value even after the setting.

4. A pump apparatus comprising:

a pump;

a motor that drives the pump;

a rotation speed detector that detects a rotation speed of the motor;

a load detector that detects a load of the motor; and

wherein in a case where the target rotation speed regulator regulates the target rotation speed in response to the load detection value, the target rotation speed regulator increases the target rotation speed until a difference between the load detection value and the upper-limit value becomes smaller than a predetermined threshold value when the target rotation speed currently set to the rotation speed controller is slower than the minimum rotation speed defined in the predetermined relation, the load detection value is smaller than the upper-limit value, and the difference between the load detection value and the upper-limit value exceeds the threshold value.

5. The pump apparatus according to claim 1,

wherein the pump is a self-priming pump, and

wherein the target rotation speed regulator sets a target rotation speed for a self-priming operation faster than a maximum rotation speed defined in the predetermined relation to the rotation speed controller when receiving a signal for instructing the start-up of the pump.

6. The pump apparatus according to claim 5,

wherein the target rotation speed regulator compares the load detection value with a predetermined lower-limit value after setting the target rotation speed for the self-priming operation to the rotation speed controller, and regulates the target rotation speed in response to the load detection value when the load detection value exceeds the lower-limit value.

7. The pump apparatus according to claim 6,

wherein the target rotation speed regulator stops the rotation of the motor when the load detection value is smaller than the lower-limit value for a predetermined time after the target rotation speed for the self-priming operation is set to the rotation speed controller.

8. The pump apparatus according to claim 6,

wherein the target rotation speed regulator sets an initial target rotation speed slower than the target rotation speed for the self-priming operation to the rotation speed controller when receiving a signal for instructing the start-up of the pump, compares the load detection value with the lower-limit value after the setting, and sets the target rotation speed for the self-priming operation to the rotation speed controller when the load detection value is smaller than the lower-limit value.

9. A pump apparatus comprising:

a pump;

a motor that drives the pump;

a rotation speed detector that detects a rotation speed of the motor;

a load detector that detects a load of the motor; and

a target rotation speed regulator that regulates the target rotation speed in response to the load detection value of the load detector so as to approach a predetermined relation between the load and the rotation speed, the predetermined relation being set so that the rotation speed decreases in accordance with an increase in the load, the rotation speed increases in accordance with a decrease in the load, and an upper-limit value of the load is set.