JPH0335514B2 - - 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, and
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, which can cause problems in practical use. 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 overloading and the oil pressure from rising excessively, and allows 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 electrode plates 5 and 6 are formed on both the left and right sides. It is. Therefore, the internal electrode plates 3 are electrically connected to the external electrode plates 5 and 6 every other layer. This piezoelectric effect ceramic 1 differs from conventional piezoelectric effect ceramics in that it generates more than a certain amount of strain even when the applied voltage is low (for example, 100 V), and does not deteriorate at all even when the voltage is repeated (according to experiments, No deterioration was observed even after voltage pulses were continuously applied over 500 million times. On the other hand, in the present piezoelectric effect ceramic 1, as with conventional piezoelectric effect 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 piezoelectric effect ceramic 1 is a binary solid solution ceramic of magnesium/lead niobate and lead titanate (1-X).
Among Pb(Mg _1/3 Nb _2/3 )O ₃ −PbTiO ₃ , for example,
A value 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 lower casing 8 and a lower lid body 21 to both upper and lower sides of a short cylindrical body 20 with screws 22. Reference numeral 23 designates a drive shaft as a drive unit, which has a disk portion 23a at its upper end and a male threaded portion 23b at its lower end.
is located in the pump chamber 10, penetrating the center of the diaphragm 9 vertically. A plurality of plastic receiving plates 2 are mounted on the drive shaft 23.
4 and washer 25 and lower end male thread part 2.
Screw the rod 26 onto 3b, and then attach the diaphragm 9.
The drive shaft 23 is connected to the diaphragm 9 by being sandwiched between the disc portion 23a and the receiving plate 24. The drive shaft 23 is supported in a bearing hole 27 formed in the lower casing 8 forming a part of the base body 19 via a receiving plate 24 so as to be able to reciprocate up and down. 28
and 29 are first and second driving bodies for reciprocating the drive shaft 23, and the drive shaft 28,
In FIGS. 4 and 5 showing the specific structure of 29, 30 is a metal cylinder, and a connector 31 that also serves as a plug is screwed into a female thread 30a formed at one end of this cylinder 30. It is fixed with a lock nut 32. Reference numeral 33 denotes an insulating tube made of, for example, polyacetal resin, which has a small coefficient of friction and is fitted into the hollow interior of the cylinder 30. Inside this, a large number of the piezoelectric effect ceramics 1 described above each having a circular or oval shape are stacked. These piezoelectric effect ceramics 1 are bonded to each other with an adhesive so that they can slide freely relative to the insulating cylinder 33. Reference numeral 34 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 34 is brazed to the piezoelectric effect ceramic 1 with a slack left between them. Further, the electric wire 34 is wired using a space S created when the piezoelectric effect ceramic 1 is inserted into the insulating tube 33. Both external electrode plates 5 and 6 of one piezoelectric effect ceramic 1 located on the connector 31 side
Lead wires 35 and 36 connected to the cylindrical body 30 are led out to the outside and connected to a power source, so that each piezoelectric effect ceramic 1 is connected in parallel to the power source. Note that 37 is a ceramic insulating plate provided between the piezoelectric effect ceramic 1 and the connector 31. Reference numeral 38 denotes a plunger as an actuating part, and this plunger 38 is slidably inserted inside the other end of the cylindrical body 30, and its insertion end is brought into contact with the piezoelectric effect ceramic 1 via an insulating plate 39 made of ceramic. ing.

Thus, the first and second driving bodies 28 and 2
Six connectors 9 are arranged radially in a vertical positional relationship in the base body 19, and the spherical tips of the connectors 31 on the outside in the radial direction are formed on both the upper and lower sides of the annular convex portion 20a on the inner periphery of the body 20. It is rotatably fitted into and connected to the spherical recesses 40 and 41 formed by the spherical recesses 40 and 41 . The first driving body 28 on the upper side is tilted so that the center side faces diagonally upward, and the spherical tip of the plunger 38 on the center side is rotatably fitted into the spherical recess 42 formed in the upper part of the rod 26. The second drive body 29 on the lower side is inclined in the opposite direction to the inclination of the first drive body 28, that is, the central axis is directed diagonally downward, and the connector 31 on the center side is connected. The spherical tip of the rod 26 is rotatably fitted into a spherical recess 43 formed in the lower portion of the rod 26. Reference numeral 44 denotes a cap fitted in the lower part of the bearing hole 27, in which a vent hole 45 is formed, and a valve plate on the upper surface side that functions as a check valve for opening and closing the vent hole 45. 46 are provided. The valve plate 46 is made of a thin sheet of plastic, and one end thereof is fixed to the cap 44. 47 is the bearing hole 2 in the lower casing 8
A ventilation path 48 to 50 is formed to connect the upper part of 7 to the atmosphere, and 48 to 50 are annular protrusions 27a and washer 25 formed on the inner circumference of bearing hole 27, and support plate 2.
4 are vent holes formed respectively.

Next, the operation of the above structure will be described. In this embodiment, the first and second driving bodies 28 and 29 are basically energized alternately. First, when the first driving body 28 is energized, a predetermined voltage is applied to each piezoelectric ceramic 1, and each piezoelectric ceramic 1 is distorted so as to extend in the stacking direction. This distortion is minute in each piezoelectric ceramic 1, but since a large number of piezoelectric ceramics 1 are stacked, the plunger 38
The sum of the strains of a large number of piezoelectric ceramics 1 acts on the plunger 38, so that the plunger 38 is strongly pressed against the piezoelectric ceramic 1 and is linearly displaced in the direction of arrow A. Then, the first driving body 28
Since the plunger 38 is tilted upward, displacement of the plunger 38 in the direction of the arrow A generates a component force that tries to push up the output shaft 23, and as a result, the first driving body 28 moves into the recessed part of the body 20. Arrow B centered on 40
The drive shaft 23 is linearly displaced in the direction of arrow C while being rotated in the direction of arrow C. By this displacement of the drive shaft 23 in the direction of arrow C, the second drive body 29 is rotated in the direction of arrow D about the recess 41 of the body 20 while pushing the plunger 38 into the cylinder 30 . The state of the drive shaft 23 after the advance is described in the second
Indicated by the two-dot chain line in the figure. Next, when the first driving body 28 is turned off and the second driving body 29 is energized, the piezoelectric effect ceramic 1 of the first driving body 28 returns to its original state as if contracting, and the second driving body A predetermined voltage is applied to the piezoelectric effect ceramic 1 of 29 and the piezoelectric effect ceramic 1 is distorted, and the plunger 38 is strongly pressed against the piezoelectric effect ceramic 1 and is linearly displaced in the direction of arrow E in the same way as described above. Then, since the second drive body 29 is disposed tilted downward, the displacement of the plunger 38 in the direction of the arrow E causes the drive shaft 2
A force trying to push down 3 is generated, and as a result,
The second driving body 29 rotates in the direction opposite to the arrow D around the recess 41 of the body 20 and rotates the drive shaft 23 in the direction opposite to the arrow C.
The displacement of the drive shaft 23 in the direction opposite to the arrow C causes the first driving body 28 to rotate in the direction opposite to the arrow B while pushing the plunger 38 into the cylinder 30. , everything returns to its original state as shown by the solid line in FIG. Thus the first and second
By alternately energizing the drive bodies 28 and 29, the drive shaft 23 reciprocates in the direction of arrow C and the direction opposite to arrow C.

By the way, the first and second driving bodies 28 and 29
The amount of displacement of the plunger 38 is relatively small, and it is actually difficult to directly drive the diaphragm 9 by the plunger 38. However, according to the present invention, the displacement of the plunger 38 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 the amount of advancement displacement of the plunger at that time is △x,
If the amount of displacement of the drive shaft is y, then SINθ≒△x/
y Therefore, y≒△x/SINθ. However, since θ is relatively small and SINθ≪1, the amount of displacement of the plunger 38 can be amplified and taken out as a large reciprocating displacement of the drive shaft 23, 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 23, but 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 then lowered, the volume of the pump chamber 10 increases and the pressure of the paint inside becomes negative, so the foot valve 12 is moved by the compression coil spring 15. The pump moves downward against the pressure and separates from the valve seat 14, and the paint is sucked into the pump chamber 10 from the suction pipe 11. and,
By repeatedly moving the diaphragm 9 up and down in this manner, paint is sucked through the suction pipe 11, is forced to be fed 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 first Then, the power to the second driving bodies 28 and 29 is cut off. Then, when the spraying of paint from the spray gun is resumed, the pressure inside the pump chamber 10 drops, so this is detected by the pressure switch and the energization to the first and second driving bodies 28 and 29 is resumed. let In this way, even if the first and second driving bodies 28 and 29 are cut off every time the spraying of paint from the spray gun is interrupted, the electrostrictive effect of the piezoelectric ceramic 1 is used to move the diaphragm 9 back and forth. Since the diaphragm 9 is reenergized, it has good responsiveness when the power is reenergized, and the diaphragm 9 reciprocates at the same speed as in normal operating conditions at the same time as the power is reenergized.Therefore, there is almost no fluctuation in the pumping pressure, making it practical for practical use. No problems will 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. In addition, when the pressure feeding is interrupted, the diaphragm 9 will not be displaced if the current is continued, so the drive shafts 28, 29
cannot output work externally. Therefore, the internal piezoelectric ceramic 1 itself generates heat. However, piezoelectric ceramic itself has excellent heat resistance, so even if the environmental temperature exceeds 100°C, 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, for short-term suspension of pumping, such as temporary suspension of spraying operation, the drive shafts 28 and 29 are
It is also possible to operate without interrupting energization.

Incidentally, since not only the diaphragm 9 but also the receiving plate 24 are vertically displaced due to the vertical movement of the drive shaft 23, the diaphragm 9 and the receiving plate 24 generate heat due to friction or the like. However, according to this embodiment, when the receiving plate 24 moves upward due to the upward movement of the drive shaft 23, the internal volume of the bearing hole 27 increases and the pressure becomes negative.
is pushed open as shown by the two-dot chain line in FIG.
When the receiving plate 24 moves downward due to the downward movement of the bearing plate 3, the internal volume of the bearing hole 27 decreases, and the air therein is discharged outward from the ventilation path 47.
Therefore, during operation, an air flow as shown by arrow F in FIG. 2 is generated, and this air flow cools the diaphragm 9 and the receiving plate 24, so there is no risk of overheating.

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 26, 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, the present invention extracts the distortion of the piezoelectric effect ceramic as a relatively large displacement using the driving body, and further amplifies the displacement to directly drive the diaphragm. Therefore, the rotation of the electric motor is controlled by the diaphragm. Unlike those that convert into reciprocating displacement, the structure is simple, lightweight, and enables low-noise operation. Moreover, since it utilizes the electrostrictive effect of piezoelectric effect 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 effect ceramic, 9 is a diaphragm, 10 is a pump chamber, 19 is a base, 23 is a drive shaft (drive part), 28 and 29 are first and second drive bodies,
38 is a plunger (actuating part).

Claims (1)

[Claims] 1. A pump chamber that has a diaphragm on one side and sucks and discharges 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 large number of pump chambers stacked in a cylinder. first and second actuating parts for displacing the driving part in one direction and the other direction; 2 driving bodies, the first and second driving bodies are arranged so as to be tilted in opposite directions with respect to the reciprocating direction of the driving part, so that the first and second driving bodies A diaphragm pump characterized in that both ends of the diaphragm pump are connected to a base body and a drive unit, respectively, so that the piezoelectric effect ceramic of the first drive body and the piezoelectric effect ceramic of the second drive body are alternately energized.