JP2818136B2 - Centrifugal pump with controlled discharge characteristics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an impeller having an axially open one side in a pump casing, and adjusting a gap between an open side edge of the impeller and a blade plate facing the same. The present invention relates to a discharge characteristic control type centrifugal pump for controlling discharge characteristics.

[0002]

2. Description of the Related Art A discharge characteristic control type centrifugal pump uses an inverter and a servomotor separately from the above-mentioned gap adjusting type to adjust the number of revolutions of a pump drive motor in accordance with a discharge pressure and a discharge flow rate. There is an inverter system to control.

As an example of the gap adjusting type, the applicant of the present application has developed an inexpensive pump capable of performing constant discharge pressure control using the discharge water and the pressure responsive valve of the pump without using the inverter and the servomotor. It has been developed and has already been filed (Japanese Patent Application No. 4-254525).

[0004]

The former inverter system is very expensive and has a slow response due to the influence of inertia.

In the latter case, the discharge pressure can be kept constant as shown by the characteristic line AE in FIG. 5 without changing the rotation speed of the pump drive motor. However, the control characteristics have to be changed manually, which lacks versatility.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings and reference numerals relating to an embodiment. In FIG. 1, an impeller 5 having an axially open one side is provided in a pump casing 4, Of the blade plates 6 arranged on the open side of the impeller 5, one of the members, for example, the blade plate 6, is axially movable and connected to an actuator 19, and the thrust of the actuator 19 or the thrust of the impeller 5 The discharge pressure is controlled by adjusting the gap d between the open side edge of the impeller 5 and the blade plate 6 by balancing the thrust of the blade plate 6 generated by the rotation.

As a structure for adjusting the gap, in addition to the above structure, when the blade plate is movable in the axial direction, the structure is such that it is performed only by the thrust of the actuator. In the case of being movable, this includes a structure in which the thrust of the actuator or the thrust of the impeller generated by the rotation of the impeller is balanced with the thrust of the actuator.

In the centrifugal pump of the discharge characteristic control type, the actuator slidably fits the piston 9 connected to the blade plate 6 (or the impeller), which is the one moving side member, into the cylinder 8. The balance chamber 1 pressurizes the piston 9 as a fluid chamber, for example.
The balance chamber 16 is provided with an electric pilot valve 21.
Is connected to the pump discharge part via the.

In order to control the electric pilot valve 21,
Control motor 59 interlockingly connected to electric pilot valve 21
And various pressure control characteristics can be set.
4, a preamplifier 64 serving as an arithmetic circuit for receiving a current flow rate signal from the preamplifier 64 and issuing a target pressure change command corresponding to the set pressure control characteristic. An electronic unit 63 is provided as a controller for receiving a signal, detecting a deviation between the target pressure and the current pressure, and rotating the control motor 59 so as to eliminate the deviation.

According to a second aspect of the present invention, there is provided the centrifugal pump according to the first aspect, wherein a plurality of impellers are arranged on the same axis.

[0011]

A desired pressure control characteristic is determined and set among various settable pressure control characteristics stored in the preamplifier 64, and the pump is operated with performance in accordance with the set pressure control characteristic. .

When a flow signal from the flow meter 54 is input to the preamplifier 64, a target pressure in accordance with the set pressure control characteristics is calculated and input to the electronic unit 63.

In the electronic unit 63, the pressure transmitter 6
The current pressure input from 0 is compared with the target pressure, the deviation is detected, and a drive command is transmitted to the control motor 59 via the relay circuit 62.

The control motor 59 drives the electric pilot valve 21 to drive the balance chamber 16 of the actuator 19.
In the structure shown in the drawing, the gap d of the impeller 5 is adjusted by adjusting the pressure of the impeller 5 by the thrust of the actuator 19 or by the balance between the thrust of the actuator 19 and the thrust of the blade plate 6 generated by the rotation of the impeller 5. , The above target pressure.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 shows a single-stage centrifugal pump to which the present invention is applied, in which a main shaft 1 has a pair of front and rear bearings 2.
While being supported by the bearing case 3 through the like, the rear end portion in the axial direction protrudes into the spiral pump casing 4, and an open impeller 5 is integrally fixed to the front end portion. A front end of the main shaft 1 is provided with an electric motor 10 for driving a pump.
It is linked and linked. A suction pipe 14 projecting upward in a curved shape is connected to an axial rear end of the pump casing 4, and a discharge short pipe 13 is connected to a radial end of the spiral chamber 4 a. Is connected to a discharge water supply pipeline 18.

On the open side (rear side) of the impeller 5, the impeller 5
The blade plate 6 is arranged opposite to the opening side edge of the main body 1 with a gap d therebetween. The blade plate 6 is attached to the moving rod 11 arranged on the same axis as the main shaft 1 by the radial connection plate 1.
2 and is movable in the axial direction together with the moving rod 11. The moving rod 11 penetrates through the suction pipe 14, protrudes into the cylinder 8 of the actuator 19, and is connected to the piston 9 fitted to the cylinder 8 so as to be movable in the axial direction.

In this embodiment, during operation, for example, the blade plate 6 and the moving rod 11 are given a thrust forward in the axial direction by a water pressure difference generated before and after the blade plate 6.
That is, a force is generated in a direction to reduce the gap d.

The fluid chamber in the cylinder 8 is divided into a balance chamber 16 on the front side and a pressure chamber 17 on the rear side by the piston 9, and the inlet of the balance chamber 16 is connected to the downstream pressure passage 3.
4. Connected to the discharge pipe 13 via the electric pilot valve 21 and the upstream pressure passage 33, and the outlet of the balance chamber 16 is connected to the suction pipe 14 via the outlet pipe 24 and a throttle (or on-off valve). I have.

The inlet of the pressure chamber 17 is connected to the discharge short pipe 13 via an inlet pipe 28 and the like, and the outlet is connected to the suction pipe 14 via an on-off valve or a throttle and an outlet pipe 29.

FIG. 2 is a schematic vertical sectional view of the electric pilot valve 21. The interior of the valve case 31 is divided into upper and lower chambers by a diaphragm 32, and the lower case portion is balanced through a downstream pressure passage 34. Exit room 3 communicating with room 16
5 and an inlet chamber 36 communicating with the short discharge pipe 13 via the upstream pressure passage 33, and the two chambers 35, 36 communicate only through a valve port 38 provided in a partition 37. doing.

The valve element 41 is directly connected to a support plate 42 fixed at the center of the lower surface of the diaphragm 32 via a connecting rod or the like.

A spring receiving seat 43 is fixed to the upper surface of the central portion of the diaphragm 32, and a coil spring 47 is contracted between the spring receiving seat 43 and the upper spring receiver 45. The outer peripheral projection of the spring receiver 45 is fitted in a groove formed on the inner periphery of the upper case part so as to be non-rotatable and movable in the axial direction, and a screw hole is formed in the center part. Mouth 38
The external thread portion of the pilot shaft 26 on the same axis as the screw thread is screwed.

The pilot shaft 26 is rotatably fitted to and supported by the upper case portion and protrudes upward. A large-diameter rotary operation gear 50 is fixed to the protruding end. A stopper 52 is formed on the pilot shaft 26 to contact the lower surface of the upper case portion.

The electric pilot valve 21 is connected to the pilot shaft 2
When 6 rotates in the reverse rotation direction (counterclockwise), the spring receiver 45 descends, increasing the load on the spring 47 and pushing down the valve body 41 to reduce the pressure in the balance chamber 16. At the same time, the balance of the piston 9 is lost, and the blade plate 6 is moved forward so that the gap d is narrowed, and the discharge pressure of the pump is increased.

On the other hand, when the motor rotates in the normal rotation direction (clockwise), the spring receiver 45 rises to reduce the load of the spring 47, the valve body 41 returns upward, and at the same time, the balance chamber 16
, The piston 9 moves in a direction (rearward) in which the gap becomes larger, and the discharge pressure decreases.

In order to change the pressure set by the spring 47 so as to follow a predetermined pressure control characteristic by changing the current flow rate and the current pressure, an electric pilot valve including an operation part of the electric pilot valve 21 in FIG. Unit 55
, A pressure control circuit device 56, and a flow meter 54.

The electric pilot valve unit 55 has a small control motor 59 having a small-diameter drive gear 58 that meshes with the large-diameter gear 50 of the electric pilot valve 21, and detects a discharge pressure in the short discharge pipe 13 to adjust a pressure control circuit. And a pressure transmitter 60 that transmits the signal to an electronic unit 63 functioning as a meter. The pressure control circuit device 56 includes a constant voltage unit 61, a relay circuit 62, the electronic unit 63, and a preamplifier 64 functioning as an arithmetic circuit.

The constant voltage unit 61 supplies the pressure transmitter 60 with a constant voltage for operating the same. The flow meter 54 is arranged in the middle of the discharge water supply pipeline 18.

In FIG. 3, various pressure control characteristics (gradients) are stored in the preamplifier 64 and can be arbitrarily set. When a load signal (flow signal) of the amount of water used is input from the flow meter 54, A target pressure change command corresponding to the set pressure control characteristic is input to the electronic unit 63.

The electronic unit 63 receives the target pressure change command from the preamplifier 64 and the current pressure signal from the pressure transmitter 60, detects a deviation between the current pressure and the target pressure,
The control pressure of the electric pilot valve 21 is adjusted by rotating the control motor 59 to the target pressure.

FIG. 5 shows examples of various pressure control characteristics which can be set by the preamplifier 64. In FIG. 5, a characteristic line AB having a gradient closest to the pipeline resistance curve R of the apparatus, and a gradient having a gentler gradient than that. Characteristic line AC or straight line A-
D can be freely set to an arbitrary gradient, and the discharge pressure can be set to be constant regardless of the flow rate as shown by the characteristic line AE by not using the flow rate signal.

The curve T1 in FIG. 5 shows the maximum pump performance and changes when the gap is the smallest, and the curve T3 shows the minimum pump performance and changes when the gap is the largest.

The pressure control during operation when the set pressure control characteristic by the preamplifier 64 is selected so as to have the gradient of the characteristic line AB in FIG. 5 will be described with reference to the flowchart in FIG.

In steps S1 and S2, the amount of water Q1,
If there is no change in the flow rate during the operation at the pressure P1, the operation in this state is maintained.

If the amount of water has changed to Q2, in step S3, the amount of water Q
2 is input.

In step S4, the preamplifier 64 determines a target pressure P2 corresponding to the water amount Q2 along the determined set pressure control characteristic line AB (FIG. 5).
A pressure change command is input to the electronic unit 63.

In steps S5 and S6, the electronic unit 63 compares the current pressure input from the pressure transmitter 60 with the target pressure P2, detects the pressure deviation, and relays a pressure correction command according to the deviation. Input to the circuit 62.

In step S7, the control motor 59 is driven via the relay circuit 62 and the electric pilot valve 21 is driven.
Is rotated until the discharge pressure reaches the target pressure, and the gap d of the open impeller 5 is controlled. As a result, the pump performance becomes T2 (FIG. 5), and P2 as in steps S8 and S9.
, The clearance control of the open impeller 5 ends.

Then, in step S10, the water amount Q
2. In the operating state at the pressure P2, a change in the amount of water is detected and controlled as described above.

Therefore, when the pressure control characteristic line AB is set, the pump performance between A and B is steplessly controlled, and the so-called constant estimated end pressure control approximate to the pipeline resistance curve R is performed. I can do it. For a smaller amount of water than point B, the minimum pump performance (fixed pump performance) is T3 (BD).
As a result, what is A-F in the conventional general-purpose pump is A-B-D, and the difference between the two indicated by the hatched portion is the energy saving.

The first embodiment can also be applied to a configuration in which thrust is not generated on the blade plate 6 by rotation of the impeller 5, and in this case, the gap d is reduced only by the piston force of the actuator 19. Adjust.

(Second Embodiment) FIG. 6 shows a modification of the actuator 19 in the blade plate moving system similar to that of FIG. 1, and the inside of the cylinder 8 includes a front balance chamber 16 and a rear low pressure chamber. Room 117, and balance room 1
6 is connected to the outlet (secondary pressure side) of the electric pilot valve 21, and the outlet of the balance chamber 16 is connected to the suction pipe 14 via the throttle 70. The low pressure chamber 117 is connected to the suction pipe 14.

In the discharge characteristic control type centrifugal pump provided with the actuator 19, the balance chamber 16 is provided on the front side of the piston 9 and the low pressure chamber 117 is provided on the rear side, so that the thrust of the piston 9 and the rotational force of the impeller 5 are used. The gap d is adjusted by balancing the thrust of the blade plate 6.

(Third Embodiment) FIG. 7 also shows a modification of the actuator 19, in which the cylinder 8 is
As a result, the rear balance chamber 116 and the front pressure chamber 11
8, the inlet of the balance chamber 116 is connected to the outlet on the secondary pressure side of the electric pilot valve 121, and the pressure chamber 1
The inlet of 18 is connected to the discharge short pipe 13 via a throttle 119, and the outlets of both chambers 116, 118 are respectively connected to the throttle 122,
For example, it is connected to the suction pipe 14 via 123.

The electric pilot valve 121 used in the embodiment of FIG. 7 is the reverse of the operation in the embodiment of FIG.
When the primary pressure rises, the secondary pressure falls, and when the primary pressure falls, the secondary pressure rises.

FIG. 8 shows a specific structure of the motor-operated pilot valve 121 of FIG. 7, in which the valve element 41 is disposed below the valve port 38 as compared with the pilot valve 21 of FIG. When the pressure (primary pressure) in the upstream inlet chamber 36 increases, the valve body 41 rises against the spring 47 and the valve port 38 becomes narrower, so that the pressure in the downstream outlet chamber 35 (secondary pressure) increases. ) Falls.

(Fourth Embodiment) FIG.
5 is a multi-stage pump having a plurality of impellers 5 fixed thereon, wherein the impeller 5 is configured to be movable in the axial direction together with a shaft 125, and the impeller plate 6 has a fixed shape (fixed wall). The moving rod 9 a of the piston 9 of the actuator 19 is connected to the 125 via a bearing joint 126.

The front side of the piston 9 of the cylinder 8 is a balance chamber (variable pressure chamber) 16. The inlet is connected to the secondary pressure outlet of the electric pilot valve 21, and the outlet side communicates with the suction pipe 14.

The rear side of the piston 9 is a low pressure chamber 130,
The outlet side communicates with the suction pipe 14 or the atmosphere.

[0050]

As described above, according to the present invention, (1) the axial position of the impeller is adjusted by adjusting the thrust of the actuator or the axial thrust generated by the rotation of the impeller. Therefore, manufacturing costs and maintenance costs can be reduced as compared with expensive devices using an inverter, a servomotor, or the like.

(2) Since the pressure control characteristic can be set arbitrarily, the characteristic can be set to a characteristic line (gradient) AB similar to the pipeline resistance curve R, for example, as a characteristic line AB in FIG. That is, so-called estimated terminal pressure constant control can be performed, and energy corresponding to the shaded region can be saved as compared with the conventional A-F, and power costs such as power costs can be saved.

(3) By storing various pressure characteristics in the arithmetic circuit (preamplifier 64), an arbitrary discharge pressure control characteristic suitable for various use conditions can be selected. For this purpose, in addition to the configuration relating to pressure detection, it also has a configuration requirement relating to flow detection, receives a current flow signal by an arithmetic circuit, issues a target pressure signal corresponding to the set pressure control characteristic, and uses a controller (electronic unit 63). Then, the control motor is rotated so as to eliminate the deviation between the target pressure and the current pressure by receiving the target pressure change command and the current pressure signal. Incidentally, if the input of the flow rate is not used, the discharge pressure constant control can be performed as shown by AE in FIG.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a discharge characteristic control type centrifugal pump to which the present invention is applied.

FIG. 2 is an enlarged longitudinal sectional view of the electric pilot valve of FIG. 1;

FIG. 3 is a block diagram showing an operation flow of the entire apparatus.

FIG. 4 is a control flow chart showing an example of an operation.

FIG. 5 is a graph showing the relationship between the discharge pressure (head) and the amount of water.

FIG. 6 is a schematic longitudinal sectional view showing a second embodiment of the present invention.

FIG. 7 is a schematic longitudinal sectional view showing a third embodiment of the present invention.

FIG. 8 is an enlarged longitudinal sectional view of the electric pilot valve of FIG. 7;

FIG. 9 is a schematic longitudinal sectional view showing a fourth embodiment of the present invention.

[Description of Signs] 1 Main shaft 4 Pump casing 5 Open impeller 6 Blade plate 8 Cylinder 9 Piston 13 Discharge short pipe (discharge part) 14 Suction pipe 16 Balance chamber (fluid chamber) 21 Electric pilot valve 26 Pilot shaft 54 Flow rate Total 55 Electric pilot valve unit 56 Pressure control circuit device 59 Control motor 60 Pressure transmitter 63 Electronic unit (controller) 64 Preamplifier (arithmetic circuit) 121 Electric pilot valve

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F04D 15/00

Claims (2)

(57) [Claims] 1. An impeller whose one side in the axial direction is open, and a blade plate disposed on an open side of the impeller, connect one member to a piston fitted to a cylinder, together with the piston. Discharge that enables axial movement and adjusts the gap between the open side edge of the impeller and the blade plate by the thrust of the piston or the balance between the thrust and the thrust generated by the rotation of the impeller to control the discharge pressure. In a characteristic control type centrifugal pump, an electric pilot valve that connects a fluid chamber in a cylinder that operates a piston and a pump discharge section, a control motor that rotationally drives the electric pilot valve, and detects a discharge flow rate to generate a current flow signal. A flow meter for transmitting, a pressure transmitter for detecting the discharge pressure and transmitting the current pressure signal, and various pressure control characteristics can be set and receive the current flow signal to set the pressure. An arithmetic circuit that outputs a target pressure signal corresponding to the force control characteristic, and a target pressure change command and a current pressure signal from the arithmetic circuit are received, a deviation between the target pressure and the current pressure is detected, and the deviation is eliminated. And a controller for rotating a control motor. 2. The discharge characteristic control type centrifugal pump according to claim 1, wherein a plurality of impellers are arranged on the same axis.