JP2696047B2 - Centrifugal pump with controlled discharge characteristics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump casing having an impeller having one open side in the axial direction, and adjusting a gap between an open side edge of the impeller and a wall surface facing the impeller. The present invention relates to a discharge characteristic control type centrifugal pump in which discharge characteristics are controlled so that a discharge pressure set initially is maintained even when a flow rate changes from a maximum to a minimum.

[0002]

2. Description of the Related Art A centrifugal pump employing a control system of this kind is disclosed in Japanese Patent Publication No. 1-125959 or Japanese Patent Publication No.
No. 12960. FIG. 3 shows the former structure in a simplified manner. A main shaft 102 to which an open impeller 101 is fixed is slidably supported in a pump casing in the axial direction.
02 is connected to a piston 105 of a servo cylinder 104, and the piston 105 partitions the inside of the cylinder 104 into two chambers, a variable pressure chamber 107 and a constant pressure chamber. The inlet of the variable pressure chamber 107 is connected to a pump discharge port 111 via an electromagnetic valve 110 to introduce a discharge pressure into the variable pressure chamber 107, and the inlet of the constant pressure chamber 108 on the opposite side is depressurized. It is connected to the discharge port 111 via a valve 112 so that a constant pressure is introduced into the constant pressure chamber 108. The outlet of the variable pressure chamber 107 is connected to a low pressure pump suction port via an electromagnetic valve 113, and the outlet of the constant pressure chamber 108 is also connected to the suction port. Each of the solenoid valves 110 and 113 detects a difference between a desired discharge pressure and a discharge pressure at each discharge amount during operation, and operates a pressure switch 1 for operating the solenoid valves 110 and 113.
17 are connected.

[0003] The difference between the desired discharge pressure and the discharge pressure at each discharge amount during operation is detected, and a hydraulic balance promoting mechanism comprising solenoid valves 110, 113 and the like operated by a pressure switch 117 is connected to the variable pressure chamber 107. The pressure balance in the constant pressure chamber 108 is positively disrupted, that is, if the discharge pressure increases, the pressure in the fluctuation chamber 107 increases, and the gap S in front of the blade increases. Conversely, if the discharge pressure drops, the variable pressure chamber 107
, The gap S is reduced. That is, the pressure difference between the two chambers 107 and 108 of the cylinder is used as the main driving force for moving the impeller.

[0004]

The conventional structure as described above has the following problems. (1) Solenoid valves 110 and 113 together with pressure switch 117
And the use of electric control circuits etc., which complicates the structure and increases the manufacturing cost. In addition, the solenoid valve itself has low durability against water, so the maintenance cost is also high. Get on. (2) The solenoid valves 110 and 113 generate large noise when opened and closed,
Soundproofing measures such as a storage case with soundproofing lining are required. (3) Since the pressure control is performed within the upper and lower limits of the pressure switch 117, the control width is large and the control pressure varies widely. (4) The pressure balance between the two chambers in the cylinder, that is, the variable pressure chamber 107 and the constant pressure chamber 108 is broken, and the gap S is controlled by the difference between the pressure difference between these two chambers and the axial thrust of the main shaft 102. However, when the thrust is large in spite of the low discharge pressure as in the example of 50HZ for 60HZ of the multi-stage pump, the pressure in the constant pressure chamber 108 is increased in order to increase the pressure difference between the two chambers to facilitate control. If it is lowered too much, it will exceed the lower limit capacity of the pressure reducing valve 102,
You cannot respond.

It is an object of the present invention to (1) eliminate the electric system such as the solenoid valve, the pressure switch and the electric control circuit associated therewith to simplify the structure, reduce the manufacturing cost, and reduce the maintenance cost. Reduce noise. (2) The constant pressure chamber can be substantially eliminated, thereby simplifying the structure and solving the problem of the pressure reducing valve. (3) By abolishing the pressure switch and using a pressure responsive valve using the discharge water pressure, the control width is narrowed and the control accuracy is improved.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an axially movable impeller having an axially open one side in a pump casing 4, and an open-ended end of the impeller. A space on the back side of the impellers 5 and 6 is provided by an annular portion 26 and divides a space on the back side of the impellers 5 and 6 into a high-pressure space on the radially outward discharge side and a low-pressure space communicating with the radially inward suction port. At the same time, the annular portion 26 is positioned so that an axial thrust is generated in a direction in which the gap is always closed by the rotation of the rotary blades 11 and 12, and an axial force opposing the axial thrust is applied from the outside, In a discharge characteristic control type centrifugal pump for controlling discharge characteristics, a main shaft 1 to which impellers 5 and 6 are fixed is slidably supported in a pump casing 4 in the axial direction, and the main shaft 1 is axially moved together therewith. Piston to be free It was ligated, by fitting the piston 9 axially movably cylinder 8, the cylinder 8
A variable pressure chamber 46 for pressurizing the piston 9 in a direction opposing the thrust of the impellers 5 and 6 is formed therein, and a space opposite to the variable pressure chamber 46 communicates with the low pressure portion of the pump or the atmosphere. And the inlet of the variable pressure chamber 46 is connected to the inlet of the variable pressure chamber 46 via a pressure responsive valve 50 whose opening is adjusted to a large side in accordance with an increase in pump discharge pressure to introduce discharge water into the variable pressure chamber 46. Connected to the pump discharge part, and the outlet of the variable pressure chamber 46 is
By connecting to the pump suction portion via a throttle, the pressure in the variable pressure chamber 46 pressurizes the piston 9 in a direction to open the gap, and when the pump discharge pressure is higher than the set value of the pressure-responsive valve 50, When the pressure in the pressure chamber 46 overcomes the thrust and moves the impellers 5 and 6 to the gap opening side, and when the discharge pressure is lower than the set value, the thrust of the impellers 5 and 6 moves to the gap closing side to reduce the discharge pressure. At the time of the set value, the pressure of the variable pressure chamber and the thrust of the impellers 5 and 6 are balanced, the impellers 5 and 6 do not move, and the discharge pressure is maintained at the set value. It is a characteristic control type centrifugal pump.

[0007]

[Action] When the discharge pressure of the pump becomes smaller than the set value,
The degree of opening of the pressure-responsive valve decreases, the pressure in the variable pressure chamber decreases, and the axial thrust to the gap closing side of the impeller overcomes the pressure in the variable pressure chamber, moving the main shaft and the impeller to the gap closing side. As a result, the discharge pressure of the pump increases. When the discharge pressure of the pump becomes larger than the set value, the opening of the pressure responsive valve increases, and the pressure of the variable pressure chamber increases, so that the pressure of the variable pressure chamber overcomes the axial thrust of the impeller, and The impeller is moved to the gap opening side, whereby the discharge pressure of the pump decreases. In the state where the pump discharge pressure is at the set value, the pressure of the variable pressure chamber and the thrust of the impeller are balanced, the piston does not move, the main shaft and the impeller are maintained at the same axial position, and the gap does not change. , The pump discharge pressure is maintained at or near the set value.

[0008]

FIG. 1 shows a centrifugal pump with controlled discharge characteristics to which the present invention is applied. In FIG. 1, a main shaft 1 has front and rear ends mounted on a pump casing 4 via internal bearings 2 and 3 and the like. The first and second stage impellers 5 and 6 are fixed to a main shaft portion between the bearings 2 and 3. The front end of the main shaft 1 projects forward from the pump casing 4 and is connected to a concentric motor (not shown). The rear end of the main shaft 1 is connected to a piston 9 in a cylinder 8 via a joint 7 capable of transmitting only axial force.
It is connected to. The piston 9 is fitted to the cylinder 8 movably in the axial direction. The cylinder 8 is fixed to the pump casing 4. 13 and 14 are fitting type volute casings, 15 and 16 are suction ports of the impellers 5 and 6, 17 and 18 are walls facing the impellers 5 and 6, and 20 is an intermediate casing constituting the pump casing 4. 21 is a return blade.

That is, the space on the outer side of the annular portion 26 of the impellers 5 and 6 communicates with the pump discharge port to form a high-pressure space, and the space on the inner side defines the balancing hole 27. When the diameter of the annular portion 26 is increased, the low-pressure space becomes wider, so that the force in the direction of widening the gap increases, and conversely, the diameter of the annular portion 26 increases. Is smaller, the high-pressure space becomes wider, and the force in the direction of closing the gap increases. In consideration of this, the diameter of the annular portion 26 is determined so that thrust is always applied in the direction to close the gap during rotation.

The impellers 5 and 6, together with the main shaft 1 and the front and rear ball bearings 2 and 3, can slide rearward from the state shown in FIG. It is supported on the pump casing 4 using external bearings 29, 33 and the like. That is, the front ball bearing 2 is fitted into the ball bearing holder 31 and is supported by the external bearing 29 via the sleeve metal 28 so as to be movable in the axial direction.
The locking pin 30 which is fixed to the pump casing 4 and
The locking pin 30 allows the sleeve metal 28
And the ball bearing holder 31 are prevented from rotating. The rear ball bearing 3 is also supported by the external bearing 33 fixed to the pump casing 4 like the front ball bearing 2 via the ball bearing holder 36 and the sleeve metal 32 so as to be movable in the axial direction. 33 is a locking pin 34 for locking the sleeve metal 32 and the ball bearing holder 36.
It has.

As a joint for connecting the rear ball bearing 3 and the shaft portion 45 of the piston 9 so that only the axial force can be transmitted, a cup-shaped ball bearing holder 36 is formed with a lid 43. The ball bearing holder 36 is fitted into the outer ring from behind, and the lid 43 is fixed to the front surface of the ball bearing holder 36, so that the outer ring of the ball bearing 3 is integrally movably held in the axial direction without rotating. In the screw hole at the center of the end face of the ball bearing holder 36, the shaft 45 of the piston 9 is inserted.
By screwing a screw formed at the front end of the
And the ball bearing holder 36 are integrally connected.

The cylinder 8 is divided into a front variable pressure chamber 46 and a rear low pressure chamber 47 by fitting a piston 9 slidably in the axial direction, and an inlet 49 of the variable pressure chamber 46 is provided.
Is connected to the discharge port 19 of the pump via a pressure passage (pipe) 51 having a pressure responsive valve 50, and the pressure of the pump discharge water is reduced and introduced into the variable pressure chamber 46. The outlet 52 of the variable pressure chamber 46 is connected to an outlet passage (pipe) 55 having a throttle 54 through a low-pressure portion of the pump (for example, the suction port 15).
Connected to The low pressure chamber 47 on the rear side is provided with an opening 57 through a pipe 56 as shown by a virtual line.
The opening 57 may be opened under atmospheric pressure.

In FIG. 2 showing the details of the pressure responsive valve 50, a case 60 of the pressure responsive valve 50 includes an upper case portion 6
2 and an assembly of the lower case portion 61, and the outer peripheral edge of the diaphragm 63 is held at a joint between the two case portions 61 and 62. The diaphragm 63 is located substantially perpendicular to the center line 0-0 of the case 60,
The inside of 0 is divided up and down.

The lower case portion 61 has an inlet 65 connected to the upstream portion of the pressure passage 51 and an outlet 66 connected to the downstream portion. The inlet 65 and the outlet 66 are formed inside the lower case portion 61. To the chambers on the inlet and outlet sides of the These two chambers are separated from each other by a partition wall 67 provided inside the lower case portion 61, and communicate with each other only through a valve port 68 formed in the partition wall 67. The valve port 68 is
The valve shaft 7 is provided concentrically with the center line 0-0 of the case 60.
The upper end of 0 is directly connected to a support plate 71 fixed to the center of the lower surface of the diaphragm 63. The lower end of the valve stem 70 is a valve body 72
It is connected to. The valve body 72 is provided concentrically with respect to the valve port 68 and at a position on the inlet 65 side. Around the valve port 68, a valve seat 76 is formed on the upper surface of the partition wall 67, and a spring receiving plate 80 is formed on the upper surface of the central portion of the diaphragm 63.
Has been fixed.

A compression coil spring 81 is provided on the spring receiving plate 80.
Is seated at the lower end. The spring 81 is connected to the case center line 0-
0, and the upper end is seated on the spring receiver 82. The outer periphery of the spring receiver 82 is fitted into a groove provided on the cylindrical inner surface of the upper case portion 62 so as to be non-rotatable and slidable in a direction parallel to the center line 0-0. . A screw hole into which the screw shaft 83 is screwed is formed at the center of the spring receiver 82. The upper end of the screw shaft 83 protrudes upward from the hole of the upper case portion 62, and a handle 85 for rotating operation is attached to the protruding end. A stopper 86 is attached to the screw shaft 83 inside the upper case portion 62 and above the spring receiver 82.

According to the above structure, when the water pressure supplied from the inlet 65 decreases, the diaphragm 63 is pushed downward by the spring 81 and moves downward, and accordingly the valve stem 70 and the valve body 7 are moved.
2 moves downward, and the opening degree of the valve port 68 decreases. That is, the pressure responsive valve 50 is in the closed state or the opening degree reduced state. When the water pressure supplied from the inlet 65 increases, the diaphragm 63 is pushed up against the elastic force of the spring 81 by the supplied water pressure. Thereby, the valve body 72 is pushed up, and the opening degree of the valve port 68 increases. When the supply water pressure from the inlet 65 is a predetermined set value, as is clear from the above description, the valve body 72 opens the valve port 68 with the opening degree reduced, and the pressure-responsive valve 50 It becomes a half-open state.

Of course, by operating the handle 85 to change the compression state of the spring 81, the movement characteristics of the diaphragm 63 with respect to the supply water pressure, that is, the pressure-responsive valve 5
The set value can be adjusted according to various specifications by adjusting the opening / closing characteristics of 0.

The specific specifications of the above components are set so that the components operate as follows in relation to the above operation of the pressure responsive valve 50. When the discharge pressure of the pump decreases to a value smaller than the set value H, for example, in FIG.
When the water amount increases from the water amount Q1 and the operation point A to the water amount Q2, the pump head pressure curve remains the curve of the gap amount 6, so that the pump discharge pressure decreases and the operation point becomes B. In this case, the opening degree of the pressure responsive valve 50 decreases, and the pressure supply to the variable pressure chamber 46 is stopped or almost stopped. In this state,
Since the pressure in the variable pressure chamber 46 decreases, the axial thrust of the impellers 5, 6 overcomes the pressure in the variable pressure chamber 46,
The main shaft 1 and the impellers 5 and 6 are moved forward to narrow the gap S. As a result, the discharge pressure of the pump increases. In FIG. 4, the pump head curve rises to the curve of the gap amount 5, the operating point becomes C, and returns to the set pressure.

When the pump discharge pressure increases to a value larger than the set value, for example, in FIG. 4, when the water amount decreases from the operating point Q3 and the operating point D to Q4, the pump head curve becomes:
Since the curve of the gap amount 2 remains, the discharge pressure increases and the operating point becomes E. In this case, the degree of opening of the pressure responsive valve 50 increases, and the state becomes an open state or a state close thereto, and the discharge pressure or a pressure close to the discharge pressure is supplied to the variable pressure chamber 46. In this state, since the pressure in the variable pressure chamber 46 increases, the pressure in the variable pressure chamber 46 overcomes the axial thrust of the impellers 5, 6 and moves the main shaft 1 and the impellers 5, 6 backward. Then, the gap S is widened. Thereby, the discharge pressure of the pump decreases. Referring to FIG. 4, the pump head curve decreases to the curve of the gap amount 3, the operating point becomes F, and returns to the original set pressure.

When the pump discharge pressure is at the set value, the pressure responsive valve 50 is in a half-open state, and a relatively low pressure is supplied to the variable pressure chamber 46. In this state, the pressure in the variable pressure chamber 46 and the thrust of the impellers 5 and 6 are balanced, and the piston 9 does not move. Therefore, the main shaft 1 and the impellers 5 and 6 are also maintained at the same axial position, the gap S does not change, and the pump discharge pressure is maintained at a set value or a value near the set value. As described above, the pump discharge pressure is always maintained at or near the set value.

[0021]

Another Embodiment In addition to a multistage centrifugal pump as shown in FIG. 1, the present invention can be applied to a single stage centrifugal pump having a single impeller.

[0022]

As described above, according to the present invention, (1) the impeller is balanced by the balance between the axial thrust generated by the rotation of the impeller and the pressure of the variable pressure chamber using the pressure of the pump discharge water. Since the axial position is adjusted, there is no need to provide an expensive electric control device including a pressure switch and a solenoid valve as in the related art, which simplifies the entire structure and reduces the manufacturing cost and the maintenance cost. Can be reduced.

(2) During operation, the axial position of the impeller is determined by the balance between the axial thrust generated by the water pressure difference generated before and after the impeller and the pressure of the variable pressure chamber using the pressure of the pump discharge water. Therefore, as compared with the conventional structure in which the gap is adjusted by the three forces of the pressure difference between the two chambers in the cylinder and the axial thrust of the main shaft, the chamber on the opposite side to the variable pressure chamber is adjusted. The structure can be made extremely simple by opening it under atmospheric pressure or ultimately abolished, further simplifying the structure. More specifically, the space behind the impellers 5, 6 is radially inwardly and outwardly partitioned by the annular portion 26, and by adjusting the diameter of the annular portion 26, the axial thrust generated in the impellers 5, 6 is constantly increased. The low pressure chamber 47 is set to be independent of pressure control by communicating with the atmosphere, for example, so as to oppose the thrust of the impellers 5 and 6 on the premise of such requirements. A so-called one-chamber control system is adopted in which substantially only the pressure of the variable pressure chamber 46 in the cylinder 8 is applied as the axial external force. Therefore, the pressure itself of the variable pressure chamber 46 adjusted by the pressure responsive valve 50 becomes an axial force opposing the axial thrust of the impellers 5 and 6, and pressurizes the two chambers sandwiching the piston together to generate a pressure difference. The pressure supplied to the pressure chamber (variable pressure chamber) is smaller than that of the two-chamber control system in which the piston can be moved in both directions in the axial direction.
The valve gap between the valve body and the valve seat of the pressure responsive valve can be set small. From this, the change amount of the secondary pressure can be greatly increased with respect to the change amount of the primary pressure, and the response of the pressure change of the variable pressure chamber according to the change of the discharge pressure is improved.

(3) The axial position of the impeller is adjusted by maintaining the balance between the axial thrust generated by the rotation of the impeller and the pressure of the variable pressure chamber, and the impeller open end side is adjusted. The gap between the two chambers in the cylinder and the thrust in the axial direction of the main shaft. Is large, the control can be sufficiently performed, and the response range is widened.

(4) Since there is no need for a solenoid valve, noise when opening and closing the solenoid valve is eliminated.

(5) Since the pressure switch is abolished and the pressure responsive valve using the discharge pressure is used, and complete hydraulic self-control is performed, the opening degree is continuously changed, and the pressure of the pump is delicate and fluctuates. It can be controlled to a small width. That is, since the control can be performed instantaneously without accumulating the change amount, the discharge characteristics are significantly improved.

[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 pressure responsive valve of FIG.

FIG. 3 is a simplified vertical sectional view of a conventional example.

FIG. 4 is a graph showing a relationship between a discharge pressure and a water amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main shaft 4 Pump casing 5, 6 Open impeller 7 Joint 8 Cylinder 9 Piston 11, 12 Blade 15, 16 Suction port (suction part) 17 Wall 18 Wall 19 Discharge port (discharge part) 46 Variable pressure chamber 50 Pressure-responsive valve 54 Aperture

Claims (1)

(57) [Claims] An axially movable impeller (5, 6) having one axial side opened in a pump casing (4);
A wall surface facing the open side edge of the impeller (5, 6) is provided, and a space on the back side of the impeller (5, 6) is formed into an annular portion (26).
And a low-pressure space communicating with the suction port on the radially outward side and a shaft in a direction in which the gap is always closed by the rotation of the rotating blades (11, 12). In the discharge characteristic control type centrifugal pump which controls the discharge characteristics by positioning the annular portion (26) so as to generate the directional thrust and applying an axial force against the axial thrust from the outside, the impeller ( A pump casing (4) in which the main shaft (1) to which the (5, 6) is fixed is slidable in the axial direction.
A piston (9) is connected to the main shaft (1) so as to be axially movable therewith, and the piston (9) is fitted to a cylinder (8) so as to be axially movable. Thus, a variable pressure chamber (46) for pressurizing the piston (9) in a direction against the thrust of the impeller (5, 6) is formed in the cylinder (8), and is opposite to the variable pressure chamber (46). The space on the side is a low-pressure part of the pump or a low-pressure chamber (47) which is not pressure-controlled in communication with the atmosphere, and the opening of the variable-pressure chamber (46) is adjusted to a large side in accordance with an increase in the pump discharge pressure. Then, it is connected to a pump discharge part via a pressure responsive valve (50) for introducing discharge water into the variable pressure chamber (46), and is connected to the variable pressure chamber (4).
The outlet of 6) is connected to the pump suction portion via a throttle, so that the pressure in the variable pressure chamber (46) pressurizes the piston (9) in a direction to open the gap, and the pump discharge pressure responds to pressure. When it is higher than the set value of the valve (50), the pressure of the variable pressure chamber (46) overcomes the thrust and the impeller (5, 6)
When the discharge pressure is lower than a set value, the thrust of the impeller (5, 6) moves to the gap closing side, and when the discharge pressure is the set value, the pressure of the variable pressure chamber and the impeller A discharge characteristic control centrifugal pump characterized in that the impeller (5, 6) does not move and the discharge pressure is maintained at a set value because the thrusts of (5, 6) are balanced.