JPH0335515B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diaphragm pump suitable for, for example, pumping paint in an airless paint sprayer.

For example, during painting work using a paint sprayer, intermittent or interrupted spraying is essential;
Pressure fluctuations during spraying lead to poor atomization and must be avoided. On the other hand, an electric motor is generally used as the drive source for a diaphragm pump used to forcefully pump paint, but if the electric motor is stopped each time the spray is interrupted during painting, it becomes very difficult to open and close the switch. This can lead to early damage to the switch, overheating due to the frequent flow of starting current to the electric pump, and furthermore, fluctuations in pumping pressure due to the slow start-up of rotation, resulting in practical problems. Therefore, it has been conventional practice to continuously operate the electric motor even when spraying is interrupted to eliminate the above problems.
No. 51-15601 (US Pat. No. 3,680,981) is known. In this system, hydraulic oil is interposed between the diaphragm pump and a piston that is reciprocated by an electric motor, and when spraying is interrupted and the displacement of the diaphragm of the diaphragm pump is restricted, excess hydraulic oil is removed from the relief valve. This prevents the motor from being overloaded and the oil pressure from rising excessively, thereby allowing the motor to continue operating even when spraying is interrupted, but this makes the structure extremely complicated.

The present invention was made in view of the above circumstances, and
The purpose is to provide a diaphragm pump that is free from the risk of overheating of the drive source or fluctuation of pumping pressure even if the pump is repeatedly operated and stopped.

The present invention focuses on the fact that laminated piezoelectric ceramics produce distortion when voltage is applied, and the response is very fast.The present invention amplifies the distortion of the piezoelectric ceramic and extracts it as a large displacement to drive a diaphragm. This is how it was done.

An embodiment in which the present invention is applied to a diaphragm pump for an airless paint sprayer will be described below with reference to the drawings.

First, the laminated piezoelectric effect ceramic used in this embodiment will be explained with reference to FIG. This piezoelectric effect ceramic 1 has recently been developed and put into practical use by NEC Corporation, and is made by laminating and sintering an element in which ceramic plates 2 and internal electrode plates 3 are alternately laminated and integrated into a predetermined shape and size. The internal electrode plate 3 exposed on the entire circumferential surface is electrically insulated by insulating material 4 every other layer on both the left and right sides, and external electrodes 5 and 6 are formed on both the left and right sides. be. Therefore, the internal electrode plates 3 are electrically connected to the external electrode plates 5 and 6 every other layer. Unlike conventional piezoelectric ceramics, this piezoelectric ceramic 1 generates a certain amount of strain even when the applied voltage is low (for example, 100 V), and does not deteriorate at all even when voltage is repeatedly applied (experiments have shown that For example, no deterioration was observed even when voltage pulses were continuously applied over 500 million times. On the other hand, this piezoelectric effect ceramic 1
As with conventional piezoelectric ceramics, it is difficult to increase the layer thickness too much, and the limit is about 9 mm. By the way, the ceramic plate 2 of the present piezoelectric effect ceramic 1 is a binary solid solution ceramic of magnesium/lead niobate and lead titanate, (1-
Among X) Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ , for example, one in which X is close to 0.35 is used.

Next, in FIG. 2 showing a diaphragm pump according to the present invention, 7 and 8 are upper and lower casings, and a diaphragm 9 is held between these opposing surfaces. A pump chamber 10 is recessed in the upper casing 7 so as to face the upper surface of the diaphragm 9, and the upper casing 7 is provided with a suction pipe 11 communicating with the pump chamber 4. Reference numeral 12 denotes a foot valve provided within the suction pipe 11, which is supported by a support member 13 fitted within the suction pipe 11 so as to be movable up and down. Reference numeral 14 denotes an annular valve seat fixed to the lower surface of the support member 13. The foot valve 12 is urged upward by the elastic force of the compression coil spring 15 and comes into contact with the valve seat 14, and the foot valve 12 is pushed upwardly by the elastic force of the compression coil spring 15 and comes into contact with the valve seat 14. Suction pipe 1
This prevents backflow to 1. Reference numeral 16 denotes a discharge pipe fitted into the upper casing 7, which communicates with the inside of the pump chamber 10 via a passage 18 having a check valve 17 in the middle. Reference numeral 19 denotes a base body of the drive source, which is constructed by fastening a body 20 in the shape of a short cylinder with a bottom to the lower side of the lower casing 8 with screws 21 . Reference numeral 22 designates a drive shaft as a drive unit, which has a disk portion 22a at its upper end and a male threaded portion 22 at its lower end.
b, and the disk portion 22a is connected to the pump chamber 10.
It vertically penetrates the center of the diaphragm 9 so as to be located inside. Then, a plurality of plastic receiving plates 23 and washers 24 are fitted into the drive shaft 22, and the rod 2 is inserted into the lower end male threaded portion 22b.
5, and then attach the diaphragm 9 to the disc part 22a.
The drive shaft 22 is connected to the diaphragm 9 by being sandwiched between the diaphragm 9 and the receiving plate 23. The drive shaft 22 is supported in a bearing hole 26 formed in the lower casing 8 forming a part of the base body 19 via a receiving plate 23 so as to be able to reciprocate up and down. 27 is a driving body, and in FIGS. 4 and 5 showing the specific structure of this driving body 27, 28 is a metal cylinder;
A connector 29, which also serves as a plug, is screwed into a female thread 28a formed on one end of the connector and fixed with a lock nut 30. Reference numeral 31 denotes an insulating cylinder made of, for example, polyacetal resin, which has a low coefficient of friction and is fitted into the hollow interior of the cylinder 28, and a large number of the piezoelectric effect ceramics 1 described above, which are formed in a circular or oval shape, are stacked inside the cylinder. These piezoelectric effect ceramics 1 are bonded to each other with an adhesive so that they can freely slide on the insulating cylinder 31. 3
Reference numeral 2 denotes an electric wire with low electrical resistance, in which a silver wire is used, and electrodes of the same polarity on the external electrode plates 5 and 6 are electrically connected at each point by brazing or the like. This electric wire 32 is brazed to the piezoelectric effect ceramic 1 with a slack left between them.
In addition, the electric wire 32 is made of piezoelectric ceramic 1 with an insulating tube 3
Wiring is done using the space S that is created when the device is inserted into 1. Then, the lead wires 33 and 34 connected to both external electrode plates 5 and 6 of one piezoelectric effect ceramic 1 located on the connector 29 side are connected to the cylindrical body 2.
8 is led out and connected to a power source, so that each piezoelectric effect ceramic 1 is connected in parallel to the power source. Note that 35 is a ceramic insulating plate provided between the piezoelectric effect ceramic 1 and the connector 29. Reference numeral 36 designates a plunger as an actuating part, and this plunger 36 is slidably inserted into the other end of the cylinder 28, and its insertion end is brought into contact with the piezoelectric ceramic 1 through an insulating plate 37 made of ceramic. ing.

The driving bodies 27 are respectively disposed radially within the base body 19 and connected to connectors 29 on the radial tip side.
The spherical tip portion of the body 20 is rotatably fitted into and connected to a spherical recess 38 formed above the annular convex portion 20a on the inner periphery of the body 20. The drive shaft 27 is tilted so that the center side faces diagonally upward, and the spherical tip of the plunger 36 on the center side is rotatably fitted into and connected to a spherical recess 39 formed in the upper part of the rod 25. . Reference numeral 40 denotes a disc spring as a spring acting body, and the disc springs 40 are inserted in pairs into the upper end of the rod 25 in three stages, upper and lower. The disc spring 40 is located between the annular convex portion 26a on the inner periphery of the bearing hole 26 of the lower casing 8 and the large-diameter portion 25a of the rod 25, and always moves the rod 25 and thus the drive shaft 22 in one direction, that is, in the direction of arrow A. is energized.

Next, the operation of the above configuration will be described. In this embodiment, the drive body 27 is basically energized and de-energized alternately. First, when the drive shaft 27 is energized, a predetermined voltage is applied to each piezoelectric effect ceramic 1, and each piezoelectric effect ceramic 1 is distorted so as to expand in the stacking direction. This strain is minute for each piezoelectric ceramic 1 individually, but since a large number of piezoelectric ceramics 1 are stacked, the sum of the strains of the large number of piezoelectric ceramics 1 acts on the plunger 36. Therefore, the plunger 36 is strongly pressed against the piezoelectric ceramic 1 and is linearly displaced in the direction of arrow B. Then, since the drive shaft 27 is disposed in an upwardly inclined manner, the displacement of the plunger 36 in the direction of the arrow B generates a component force that tries to push up the output shaft 22, and as a result, the drive shaft 27 moves toward the body 20. The drive shaft 2 rotates in the direction of arrow C around the recess 38 of the
2 is linearly displaced in the other direction, the direction of arrow D, against the elastic force of the disc spring 40.
The state after the drive shaft 22 is advanced is shown by the two-dot chain line in FIG. Next, when the drive shaft 27 is cut off, the piezoelectric effect ceramic 1 returns to its original state as if it were contracted.
The disc spring 40 displaces the drive shaft 22 in the direction of the arrow A by its elastic force, and the displacement of the drive shaft 22 in the direction of the arrow A causes the drive shaft 27 to move toward the plunger 3.
6 is pushed into the cylindrical body 28, and rotates in the opposite direction of arrow B, and everything returns to its original state as shown by the solid line in FIG. In this way, by alternately repeating energization and de-energization of the drive shaft 27, the drive shaft 22 reciprocates up and down.

Incidentally, the amount of displacement of the plunger 36 of the drive shaft 27 is relatively small, and it is actually difficult to directly drive the diaphragm 9 by the plunger 36. However, according to the present invention, the displacement of the plunger 36 can be amplified and output. To explain this in principle with reference to Fig. 6, the driving body is located between O-Y ₁ before energization, and when the plunger advances due to energization, it rotates by an angle θ around O and moves between O-Y ₂ . position, and if the amount of forward displacement of the plunger at that time is △x and the amount of displacement of the drive shaft is y, then SINθ≒△x/y Therefore, y≒△x/SINθ
becomes. However, since θ is relatively small and SINθ≪1, the amount of displacement of the plunger 36 can be amplified and taken out as a large reciprocating displacement of the drive shaft 22, and the diaphragm 9 can be directly driven by the drive shaft 23. It is something that can be done.

The diaphragm 9 is vertically displaced by the vertical movement of the drive shaft 22. First, when the diaphragm 9 rises, the volume of the pump chamber 10 decreases and the pressure of the paint inside increases. When the diaphragm 9 is pushed open and the diaphragm 9 is lowered, the volume of the pump chamber 10 increases and the pressure of the paint inside becomes negative, so the foot valve 12 is forced into the compression coil spring 15. The pump moves downward and separates from the valve seat 14, and paint is sucked into the pump chamber 10 from the suction pipe 11. By repeating such vertical movement of the diaphragm 9, the paint is sucked through the suction pipe 11, is forced to be sent toward the discharge pipe 16, and is finally sprayed from the spray gun as a mist of paint.

Now, when the spraying of paint from the spray gun is interrupted, the paint in the pump chamber 10 is no longer discharged from the discharge pipe 16, so the internal pressure of the pump chamber 10 increases, which is detected by the pressure switch and the drive 27 is kept in a power-off state without being energized. When the spray gun resumes spraying the paint, the pressure inside the pump chamber 10 drops, which is detected by the pressure switch and the drive shaft 2
7, the operation of alternating energization and de-energization is resumed. In this way, even if the operation is interrupted every time the spray gun stops spraying paint, the electrostrictive effect of the piezoelectric ceramic 1 is used to move the diaphragm 9 back and forth, so the response when the power is re-energized is The diaphragm 9 reciprocates at the same speed as in the normal operating state at the same time as the power is reenergized, and therefore there is almost no fluctuation in the pumping pressure and no practical problems occur. Moreover, unlike an electric motor, there is no risk of a large starting current flowing even if the power is turned on and off frequently, so there is no risk of overheating or early damage to the switch. Furthermore, if the energization is continued after the pumping is interrupted, the diaphragm 9 will not be displaced, so the drive shaft 27 will not be able to output work to the outside. Therefore, the internal piezoelectric ceramic 1 itself generates heat. However, piezoelectric ceramic itself has excellent heat resistance, and the environmental temperature
Even if the temperature exceeds 100℃, there will be no problem with its performance or durability. Therefore, there is no need to interrupt the energization unless the temperature rises abnormally. Therefore, it is possible to operate the driving body 27 without interrupting energization when the pumping operation is stopped for a short period of time, such as when a spraying operation is temporarily interrupted.

In addition, another pump chamber is provided on the lower side of the base body 19,
If the diaphragm of this pump chamber is also displaced by the rod 25, two types of paint can be pumped at the same time. Moreover, it can be widely applied not only to the pumping of paint but also to the pumping of fluids in general.

As is clear from the above description, in the present invention, the distortion of the piezoelectric ceramic is extracted as a relatively large displacement by the driving body, and the displacement is further amplified to directly drive the diaphragm, so that the rotation of the electric motor is controlled by the diaphragm. Unlike those that convert reciprocating displacement, the structure is simple, lightweight, and enables low-noise operation. Moreover, since it utilizes the electrostrictive effect of piezoelectric ceramic, it has good responsiveness and there is no risk of large starting current flowing, so there is no risk of the fluid pumping pressure fluctuating even if the operation is interrupted frequently. This provides various effects such as preventing early damage to the switch.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a sectional view schematically showing a piezoelectric effect ceramic, Figs. 2 and 3 are longitudinal sectional views and a partial plan view of a diaphragm pump, and Fig. 4 is a driving body. 5 is a longitudinal sectional view taken along the line - in FIG. 4, and FIG. 6 is a diagram showing the principle of displacement amplification. In the figure, 1 is a piezoelectric ceramic, 9 is a diaphragm, 10 is a pump chamber, 19 is a base, 22 is a drive shaft (drive part), 27 is a driver, 36 is a plunger (actuating part), and 40 is a disc spring (spring). (acting body).

Claims (1)

[Claims] 1. A pump chamber having a diaphragm on one side and sucking and discharging fluid to be pressurized according to the displacement of the diaphragm, a base body that reciprocably supports a drive unit connected to the diaphragm, and a base body that supports the drive unit in one direction. It has a spring acting body that biases the body, a laminated piezoelectric effect ceramic stacked in large numbers in a cylinder, and an actuating part that is displaced by the distortion of these piezoelectric effect ceramics caused by the application of voltage. a driving body that displaces the driving part, which is connected to the base body and the driving part and is arranged in an inclined state with respect to the reciprocating direction of the driving part, in the other direction against the elastic force of the spring acting body; A diaphragm pump equipped with: