JPH06101687A - Discharge characteristic controlling type centrifugal pump - Google Patents

Abstract

PURPOSE:To simplify the construction of a controller, reduce cost and improve accuracy in control in a discharge characteristic controlling type centrifugal pump. CONSTITUTION:A main shaft 1 having impellers 5, 6 fixed thereto is shaft- supported axially slidably on a pump casing 4, and a piston 9 connected to the main shaft 1 is fitted axially movably in a cylinder 8 so that a variable pressure chamber 46 for pressing the piston 9 against the thrust of the impellers 5, 6 is formed. An inlet 49 of a variable pressure chamber 46 is connected to a pump discharge section through a pressure responsive valve 50 adjusting the opening in response to the increase of pump discharge pressure to the larger side to introduce discharge water into the variable pressure chamber 46. An outlet 52 of the variable pressure chamber 46 is connected to the pump suction section through a throttle 54. When the discharge pressure is higher than a set value of the pressure responsive valve 50, the pressure in the variable pressure chamber 46 overcomes the thrust to shift the impellers 5, 6 to the clearance opening side constitutively.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Centrifugal pumps employing this type of control system are disclosed in Japanese Examined Patent Publication No. 1-12959 or Japanese Examined Publication 1-
There is 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 axially slidably supported by a pump casing.
02 is connected to a piston 105 of a servo cylinder 104, and the piston 105 divides the inside of the cylinder 104 into two chambers, a variable pressure chamber 107 and a constant pressure chamber 108. The inlet of the fluctuating pressure chamber 107 is connected to the pump discharge port 111 via the solenoid valve 110 to introduce the discharge pressure into the fluctuating pressure chamber 107, and the inlet of the constant pressure chamber 108 on the opposite side is decompressed. A constant pressure is introduced into the constant pressure chamber 108 by connecting to the discharge port 111 via a valve 112. The outlet of the fluctuating pressure chamber 107 is connected to the low pressure pump suction port through the solenoid valve 113, and the constant pressure chamber 108 is also connected to the suction port. Each of the solenoid valves 110 and 113 has a pressure switch 1 for operating the solenoid valves 110 and 113 by detecting a difference between a desired discharge pressure and a discharge pressure at each discharge amount during operation.
17 is connected.

By detecting the difference between the desired discharge pressure and the discharge pressure at each discharge amount during operation, a hydraulic balance promoting mechanism composed of electromagnetic valves 110, 113 and the like operated by a pressure switch 117, and the variable pressure chamber 107. The pressure balance of the constant pressure chamber 108 is positively broken, that is, when the discharge pressure rises, the pressure in the fluctuation chamber 107 is increased, and the gap S in front of the blade is increased. On the contrary, if the discharge pressure decreases, the variable pressure chamber 107
The pressure of is reduced to reduce the gap S. That is, the pressure difference between the two chambers 107 and 108 of the cylinder is 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 the pressure switch 117
, The electric control circuit etc. associated therewith are complicated, the structure is complicated and the manufacturing cost is high, and the solenoid valve itself has low durability against water, so the maintenance cost is also high. Tsuku. (2) The solenoid valves 110 and 113 generate a lot of noise when opening and closing,
Soundproof measures such as a storage case lined with soundproof material are required. (3) Since the pressure control is performed within the upper and lower limits of the pressure switch 117, the control range 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 disrupted, 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, like the example of 50HZ to 60HZ of the multi-stage pump, when the thrust is large despite the low discharge pressure, the pressure in the constant pressure chamber 108 is set to be large because the pressure difference between the two chambers is made easy to control. Although it is lowered, if it is lowered too much, the lower limit capacity of the pressure reducing valve 102 is pushed out,
I can't respond.

The object of the present invention is (1) to abolish the electric system such as the solenoid valve, the pressure switch and the electric control circuit associated therewith, thereby simplifying the structure, reducing the manufacturing cost and the maintenance cost, and Aim to reduce noise. (2) Since the constant pressure chamber can be substantially abolished, the structure is simplified and the problem of the pressure reducing valve is solved. (3) By eliminating the pressure switch and using a pressure responsive valve that utilizes discharge water pressure, the control range is narrowed and control accuracy is improved.

[0006]

In order to solve the above-mentioned problems, the present invention provides a pump casing with an impeller whose one side in the axial direction is open, and a direction in which the gap on the open side is closed by rotation of the impeller. A centrifugal pump in which axial thrust is generated, and in the discharge characteristic control type centrifugal pump in which the discharge characteristics are controlled by adjusting the above-mentioned clearance, the main shaft with the impeller fixed is slidable in the axial direction. A direction that resists the thrust of the impeller by supporting the pump casing, connecting a piston to the main shaft so as to be movable in the axial direction together with the main shaft, and fitting the piston in the cylinder so as to be movable in the axial direction. A variable pressure chamber that pressurizes the piston is formed in
The inlet of the fluctuating pressure chamber is connected to the pump discharge part via a pressure response valve that adjusts the opening to a large side according to the increase of the pump discharge pressure and introduces discharge water into the fluctuating pressure chamber. Exit
When the discharge pressure is higher than the set value of the pressure-responsive valve, the pressure in the fluctuating pressure chamber overcomes the thrust to move the impeller to the gap opening side, and the discharge pressure is higher than the set value. When the pressure is low, the thrust is used to move to the gap closing side, and the discharge pressure is maintained at the set value.

[0007]

[Operation] When the discharge pressure of the pump becomes smaller than the set value,
The opening of the pressure responsive valve decreases, the pressure in the fluctuating pressure chamber decreases, and the axial thrust of the impeller against the gap closing side overcomes the pressure in the fluctuating pressure chamber to move the spindle and impeller to the gap closing side. However, this causes the discharge pressure of the pump to rise. 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 fluctuating pressure chamber increases, so the pressure of the fluctuating pressure chamber overcomes the axial thrust of the impeller, The impeller is moved to the gap opening side, which reduces the discharge pressure of the pump. When the pump discharge pressure is at the set value, the pressure of the fluctuating pressure chamber and the thrust of the impeller are in equilibrium, the piston does not move, the main shaft and 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]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a discharge characteristic control type centrifugal pump to which the present invention is applied. In FIG. 1, a main shaft 1 has front and rear end portions connected to a pump casing 4 through internal bearings 2 and 3. It is supported, and the first and second stage impellers 5 and 6 are fixed to the 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), and the rear end of the main shaft 1 has a piston 9 in a cylinder 8 via a joint 7 capable of transmitting only axial force.
Connected to. The piston 9 is fitted in the cylinder 8 so as to be movable in the axial direction. The cylinder 8 is fixed to the pump casing 4. Numerals 13 and 14 are fit-in 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. Reference numeral 21 is a return blade.

The front and rear impellers 5 and 6 are fixed to the centrifugal blades 11 and 12, respectively, and open toward the front, and face the front walls 17 and 18 with a gap S therebetween. There is. In the case of such open type impellers 5 and 6,
During operation, the thrust force in the axial direction is generated due to the pressure difference of the water pressure generated before and after each of the impellers 5 and 6. Specifically,
When the water pressure behind the impellers 5 and 6 is 1.0 during operation,
The front side (open side) having the blades 11 and 12 has a diameter (D1 + D2) / 2 of about 0.5 due to the opening of the edge, which is as small as 0.5.
A large axial thrust is generated at 6 in the forward direction. In response to such thrust, the respective impellers 5 and 6 are formed on their rear surfaces with an annular portion 26 and a balancing hole 27 that fit into the internal annular protrusions of the volute casings 13 and 14. The large thrust (thrust force) is reduced, and the excessive axial load on the bearing 3 is reduced. The diameter of the annular portion 26 is set to the blades 11, 12
By setting the diameter D1 to be larger than the diameter D1 of the inner edge of the rear end, the area of the rear annular space on the outer side of the annular portion 26 is reduced, and the forward thrust is reduced to an appropriate value. can do. The balancing hole 27 is for balancing the pressure in the front and rear space portions on the inner side of the annular portion 26.

The impellers 5 and 6 together with the main shaft 1 and the front and rear ball bearings 2 and 3 are slidable rearward from the state shown in FIG. It is supported on the pump casing 4 by utilizing external bearings 29, 33 and the like. That is, the front ball bearing 2 is fitted into the ball bearing holder 31 and supported by the outer bearing 29 via the sleeve metal 28 so as to be movable in the axial direction.
Fixed to pump casing 4 and locking pin 30
And the detent pin 30 allows the sleeve metal 28
The ball bearing holder 31 is prevented from rotating. Similarly to the front ball bearing 2, the rear ball bearing 3 is also supported by an outer bearing 33 fixed to the pump casing 4 so as to be axially movable via a ball bearing holder 36 and a sleeve metal 32. 33 is a rotation stopper pin 34 for stopping the rotation of the sleeve metal 32 and the ball bearing holder 36.
Is equipped with.

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, the cup-shaped ball bearing holder 36 is constructed with a lid 43. By fitting the ball bearing holder 36 into the outer ring of the ball bearing from the rear and fixing the lid 43 to the front surface of the ball bearing holder 36, the outer ring of the ball bearing 3 is held so as to be movable integrally in the axial direction without rotating. The ball bearing holder 36 has a screw hole at the center of the end face thereof, and the shaft portion 45 of the piston 9 is
By screwing the screw formed at the front end of the shaft 45
And the ball bearing holder 36 are integrally connected.

The cylinder 8 is divided into a front pressure fluctuation 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 pressure fluctuation chamber 46.
Is connected to the discharge port 19 of the pump through a pressure passage (pipe) 51 having a pressure responsive valve 50 to reduce the pressure of the pump discharge water and introduce it into the variable pressure chamber 46. The outlet 52 of the fluctuating pressure chamber 46 passes through an outlet passage (pipe) 55 having a throttle 54, and a low pressure part of the pump (for example, the suction port 15).
Connected to. The low-pressure chamber 47 on the rear side has an opening 57 through a pipe 56, as shown by an imaginary line.
The opening 57 may be opened under atmospheric pressure.

In FIG. 2 showing the details of the pressure-responsive valve 50, the case 60 of the pressure-responsive valve 50 is an upper case portion 6
2 and the lower case portion 61, and the outer peripheral edge portion of the diaphragm 63 is held at the joint portion between the two case portions 61 and 62. The diaphragm 63 is positioned substantially at right angles to the center line 0-0 of the case 60, and
The inside of 0 is divided into upper and lower parts.

The lower case portion 61 is formed with an inlet 65 connected to the upstream side portion of the pressure passage 51 and an outlet 66 connected to the downstream side portion. The inlet 65 and the outlet 66 are inside the lower case portion 61. Communicates with the chamber on the inlet side and the chamber on the outlet side. These chambers are separated 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
It is provided coaxially with the center line 0-0 of the case 60, and the valve rod 7
The upper end of 0 is directly connected to the support plate 71 fixed to the center of the lower surface of the diaphragm 63. The lower end of the valve rod 70 has a valve body 72.
Connected to. The valve body 72 is provided concentric with the valve port 68 and at a position on the inlet 65 side. A valve seat 76 is formed on the upper surface of the partition wall 67 around the valve opening 68, and a spring bearing plate 80 is formed on the upper surface of the central portion of the diaphragm 63.
Is fixed.

The spring receiving plate 80 has a compression coil spring 81.
The bottom edge of is seated. The spring 81 has a case center line 0-
It extends concentrically with 0, and the upper end is seated on the spring receiver 82. The spring receiver 82 has a projection on the outer periphery thereof fitted in a groove provided on the cylindrical inner surface of the upper case portion 62 in a non-rotatable manner 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 in the center of the spring receiver 82. The upper end of the screw shaft 83 projects upward from the hole of the upper case portion 62, and a handle 85 for rotating operation is attached to the projecting end. A stopper 86 is attached to the screw shaft 83 inside the upper case portion 62 and above the spring bearing 82.

According to the above structure, when the water pressure supplied from the inlet 65 decreases, the diaphragm 63 is pushed by the spring 81 and moves downward, and accordingly, the valve rod 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 water pressure supplied. As a result, the valve body 72 is pushed up and the opening degree of the valve opening 68 is increased. When the water pressure supplied from the inlet 65 is a predetermined set value, as is apparent from the above description, the valve body 72 opens the valve opening 68 in a state where the opening degree is reduced, and the pressure responsive valve 50 is Half open.

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

The specific specifications of the above-mentioned respective parts are set so that the respective parts operate as follows in relation to the above-mentioned operation of the pressure responsive valve 50. When the discharge pressure of the pump drops to a value smaller than the set value H, for example, in FIG.
When the water amount Q1 increases from the operating point a to the water amount Q2, the pump head curve remains the curve of the gap amount 6, so the pump discharge pressure decreases and the operating point becomes b. In this case, the opening degree of the pressure responsive valve 50 is reduced, and the pressure supply to the fluctuating pressure chamber 46 is stopped or almost stopped. In this state,
Since the pressure in the fluctuating pressure chamber 46 becomes low, the thrust in the axial forward direction of the impellers 5, 6 overcomes the pressure in the fluctuating 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 rises. In FIG. 4, the pump head curve rises to the curve of the gap amount 5, the operating point becomes c, and the set pressure is restored.

When the pump discharge pressure increases to a value higher than the set value, for example, when the water amount Q3 in FIG. 4 and the water amount decreases from the operating point D to Q4, the pump head curve is
Since the curve of the gap amount 2 remains as it is, the discharge pressure increases and the operating point becomes E. In this case, the opening degree of the pressure responsive valve 50 is increased to be in the 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, the pressure in the fluctuating pressure chamber 46 increases, so that the pressure in the fluctuating pressure chamber 46 overcomes the axial forward thrust of the impellers 5, 6 and moves the main shaft 1 and the impellers 5, 6 rearward. Then, the gap S is widened. This reduces the discharge pressure of the pump. Referring to FIG. 4, the pump head curve decreases to the curve of the gap amount 3, the operating point becomes high, and the pump returns to the original set pressure.

When the pump discharge pressure is at the set value, the pressure responsive valve 50 is in the half-opened state, and a relatively low pressure is supplied to the fluctuating pressure chamber 46. In this state, the pressure of the fluctuating 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 positions, the gap S does not change, and the pump discharge pressure is maintained at a set value or a value in the vicinity thereof. As described above, the pump discharge pressure is always maintained at or near the set value.

[0021]

[Other Embodiments] In addition to the multi-stage centrifugal pump 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 fluctuating pressure chamber that utilizes the pressure of the pump discharge water. Since the axial position of the is adjusted, it is not necessary to provide an expensive electric control device including a pressure switch and a solenoid valve as in the conventional case, the entire structure is simplified, and the manufacturing cost and maintenance cost are reduced. It can be reduced.

(2) The axial position of the impeller is adjusted by the equilibrium between the axial thrust generated by the rotation of the impeller and the pressure of the fluctuating pressure chamber to adjust the clearance on the open end side of the impeller. As compared with the conventional structure in which the gap is adjusted by the pressure difference between the two chambers in the cylinder and the three forces of the axial thrust of the main shaft, the structure of the chamber on the opposite side of the fluctuating pressure chamber is The structure can be made simpler by opening it under atmospheric pressure to make it a very simple structure or, ultimately, abolishing it.

(3) The axial position of the impeller is adjusted by maintaining the equilibrium between the thrust in the axial direction generated by the rotation of the impeller and the pressure in the fluctuating pressure chamber, and the impeller open end side is adjusted. Since the gap is adjusted, compared to the conventional structure in which the gap is adjusted by the pressure difference between the two chambers in the cylinder and the thrust in the axial direction of the main shaft, the thrust force is lower even though the discharge water pressure is low. Even if is large, it can be controlled sufficiently and the response range becomes wide.

(4) Since the solenoid valve is not needed, noise when the solenoid valve is opened and closed is eliminated.

(5) Since the pressure switch is abolished and a pressure responsive valve that uses the discharge pressure is used for complete hydraulic power control, the opening is continuously changed and the pump pressure is subtly and fluctuated. It can be controlled to a narrow width. That is, since the control can be performed instantaneously without accumulating the amount of change, the ejection characteristics are significantly improved.

[Brief description of drawings]

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

FIG. 2 is an enlarged vertical cross-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 the relationship between discharge pressure and water amount.

[Explanation of symbols]

 1 Spindle 4 Pump Casing 5,6 Open Type Impeller 7 Joint 8 Cylinder 9 Piston 11,12 Blades 15,16 Suction Port (Suction Portion) 17 Wall 18 Wall 19 Discharge Port (Discharge Port) 46 Variable Pressure Chamber 50 Pressure Response Valve 54 Aperture

Claims (1)

[Claims] 1. A centrifugal pump, comprising: an impeller whose one axial side is opened in a pump casing, wherein an axial thrust is generated in a direction of closing a clearance on the open side by rotation of the impeller. In a discharge characteristic control type centrifugal pump that controls the discharge characteristic by adjusting the clearance, a main shaft with an impeller fixed is supported by a pump casing so as to be slidable in the axial direction. By connecting the piston so as to be movable, and by fitting the piston in the cylinder so as to be movable in the axial direction, a fluctuating pressure chamber for pressurizing the piston in a direction against the thrust of the impeller is formed,
The inlet of the fluctuating pressure chamber is connected to the pump discharge part via a pressure response valve that adjusts the opening to a large side according to the increase of the pump discharge pressure and introduces discharge water into the fluctuating pressure chamber. Exit
When the discharge pressure is higher than the set value of the pressure-responsive valve by connecting it to the pump suction section via a throttle, the pressure in the fluctuating pressure chamber overcomes the thrust to move the impeller to the gap opening side, and the discharge pressure is set to the set value. A discharge characteristic control type centrifugal pump, characterized in that when it is lower, it is configured to move to the gap closing side by thrust so as to maintain the discharge pressure at a set value.