JPS60237187A - Diaphragm pump - Google Patents

Abstract

PURPOSE:To prevent the temperature rise of an operating oil and eliminate an ill effect due to cavitation by providing an opening/closing valve decreasing the opening in response to the temperature rise of the operating oil on a supplementary passage and changing the negative pressure in a cylinder in response to the temperature of the operating oil. CONSTITUTION:When the temperature of an operating oil is increased to a fixed value or higher, the bimetal 49 of an opening/closing valve 50 provided on a pipe 45 supplementing the deficit of the operating oil in an operating oil chamber 8 from a tank 2 during the decompression stroke of a piston 4 is curved to decrease the opening of the valve 50 as shown by a chain line, thereby the supplementary quantity of the operating oil during the descent stroke of the piston 4 is limited, the negative pressure in a cylinder 3 is remarkably increased, the air solved in the operating oil is separated and the deficit of the operating oil is supplemented, the quantity of the operating oil passing through a relief valve 40 during the ascent stroke of the piston 4 is made exremely little, and the temperature rise of the operating oil is suppressed. In addition, the opening of the opening/closing valve 50 is gradually changed in response to the temperature change of the operating oil, thus an ill effect due to cavitation can be eliminated to the utmost.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION The present invention relates to a diaphragm pump that prevents the temperature of hydraulic fluid from rising when the pumping of liquid is stopped or the amount of pumping is throttled.

A diaphragm pump in which the diaphragm is driven back and forth by alternately increasing and decreasing the pressure of hydraulic oil in a cylinder communicating with one side of a diaphragm by reciprocating motion of a piston with a constant stroke, and pressurizes and pumps liquid on the other side. When the pumping of liquid stops or the pumping amount is throttled, the movement of the diaphragm stops or the momentum decreases, so excess hydraulic fluid in the cylinder is drained during the piston's pressurizing stroke. In addition to returning the hydraulic oil to the tank via the relief valve, it is also necessary to replenish the lack of hydraulic oil into the cylinder via the check valve during the pressure reduction stroke of the piston. If the operation continues for a long time while returning the oil to the tank, the temperature of the hydraulic oil will rise and operation will become impossible.To prevent this situation, increase the capacity of the tank, or Although it is necessary to provide a forced cooling device for the hydraulic oil, this has the disadvantage of increasing the size of the entire device.

For this reason, as described in Japanese Patent Publication No. 51'-15601, the hydraulic oil replenishment passage is blocked during a part of the piston's pressure reduction stroke, and the inside of the cylinder is tilted to negative pressure, causing cavitation. A diaphragm pump has been proposed that prevents the temperature of the hydraulic oil from rising by replenishing the shortage of hydraulic oil by separating the air dissolved in the oil. However, due to the rapid separation of air from the hydraulic oil, The shock may corrode the inner surface of the cylinder, and the piston may require extra power to drive against negative pressure. It is desirable that cavitation does not occur.

The present invention has been completed in view of the above points, and by changing the negative pressure generated in the cylinder according to the temperature of the hydraulic oil, it prevents the temperature of the hydraulic oil from rising and prevents cavitation. It is an object of the present invention to provide a diaphragm pump that eliminates adverse effects as much as possible.

EXAMPLE Hereinafter, an example of a diaphragm pump according to the present invention will be described based on the accompanying drawings.

Tank 2 from the top of the body 1 with the hydraulic oil tank 2
A piston 4 is slidably inserted into a cylinder 3 that is fitted so as to penetrate through the cylinder 3, and is urged downward by the elasticity of a spring 28 installed between the lower end of the piston 4 and a spring receiver 27 screwed onto the cylinder 3. At the same time, an eccentric shaft 6 at the tip of the drive shaft 5 connected to the output shaft of the motor M faces into the tank 2, and a roller fitted to the eccentric shaft 6 serves as a cam 7, and a piston 4 is mounted on the outer periphery of the roller. The lower ends are in contact with each other, and a seat plate 9 having a through hole 10 and an insert 30 having a center hole 31 and a through hole 32 are fitted onto the upper surface of the body 1 in a vertically overlapping manner. The periphery of the diaphragm 11 which is mounted on the seat plate 9 and superimposed on the upper surface of the seat plate 9 is fastened to the body 1 by a cover 12. A hydraulic oil chamber 8 is formed between the upper surface of the cylinder 3 and the hydraulic fluid chamber 8 which communicates with the through hole 10 of the seat plate 9 and the center hole 31 and through hole 32 of the insert 30, and is formed at the center of the upper surface of the liquid chamber 13. A check valve 18 with a valve body 16 pressed against the valve seat 15 by the elasticity of a spring 17 is interposed in the inflow hole 14 , and a discharge hole transparent from the liquid chamber 13 to the side surface of the cover 12 is inserted into the inflow hole 14 . 19
A check valve 23 is interposed in which the valve body 20 is pressed against the valve seat 22 by the elasticity of a spring 21, and the diaphragm 11 is supported by a spring attached to a central rod 24 projecting from the center of its lower surface. It is urged by the elastic force of 25 in the direction of pressing against the upper surface of the seat plate 9.

The above is the same as a conventionally known diaphragm pump, and the piston 4 reciprocates within the cylinder 3 by a partial stroke for each revolution of the drive shaft 5, and during the upward stroke of the piston 4, the operation within the cylinder 3 The oil is pressurized to open the center hole 31 and through hole 32 of the insert 30 and the through hole 10 of the seat plate 9.
The pressure pushes the diaphragm 11 upwards and pressurizes the liquid in the liquid chamber 13, which opens the check valve 23 and pumps the liquid from the discharge hole 19. In the downward stroke of step 4, the hydraulic oil in the hydraulic oil chamber 8 returns to the cylinder 3 and is depressurized, which causes the diaphragm 11 to move downward and depressurize the liquid chamber 13, and the check valve 18 opens to allow inflow. The movement of liquid flowing in from the hole 14 is repeated, but the pumping of liquid from the discharge hole 19 stops.

Or 1. As a countermeasure for the case where the flow rate is restricted, this embodiment has the following structure.

A discharge hole 35 is formed in the body 1 to communicate the hydraulic oil chamber 8 and the tank 2, and a relief valve 40 with a valve body 38 pressed against a valve seat 39 by the elasticity of a spring 37 is inserted into the discharge hole 35. It is set up.

Further, an annular space 42 is formed between the cylinder 3 and the body 1 by cutting the outer peripheral surface of the cylinder 3, and the upper end surface of the piston 4 at the bottom dead center position is formed on the inner peripheral surface of the cylinder 3. A through hole 43 communicating with the cavity 42 is formed at a slightly upper position, and a pipe 4 serving as a replenishment passage for hydraulic oil is provided in the body 1 with one end communicating with the cavity 42.
5 is fixed, and the other end of the pipe 45 hangs down into the tank 2 and is immersed in the hydraulic oil, and the other end of the pipe 45 has a diagonal opening at the lower end, as shown in FIGS. 2 and 3. A rectangular tube 46 having a shape 47 is fixed thereto, and a base end of a bimetal 49 whose distal end curves in a direction that closes the opening 47 due to temperature rise is fixed to the rectangular tube 46. The on-off valve 50 is configured by:
A wire mesh filter 52 is formed so as to cover this on-off valve 50.
is installed.

Next, the operation of this embodiment will be explained. During normal operation, the rotation of the cam 7 causes the screws to tighten! - cylinder 4 is cylinder 3
The piston 4 moves up and down to alternately increase and decrease the pressure of the hydraulic oil in the hydraulic oil chamber 8, but the pressure feeding of the liquid from the discharge hole 19 stops or the flow rate is throttled, causing the piston 4 to rise. When the pressure of the hydraulic oil in the hydraulic oil chamber 8 rises above a certain value during the stroke, the relief valve 40 opens and the hydraulic oil in the hydraulic oil chamber 8 is discharged into the tank 2 through the discharge hole 35. During the subsequent downward stroke of the piston 4, the volumetric expansion inside the cylinder 3 tilts the inside of the hydraulic oil chamber 8 to negative pressure, creating a pressure difference between it and the tank 2, which is maintained at approximately atmospheric pressure, and the temperature of the hydraulic oil increases. When the temperature is low, the bimetal 49 is in a straight position and the on-off valve 50 is open, as shown by the solid line in FIG. The hydraulic oil inside flows from the pipe 45 to the cavity 4.
2. The cylinder 3 is replenished through the through hole 43, and while the temperature of the hydraulic oil is low, the piston 4
When the hydraulic oil in the hydraulic oil chamber 8 is released into the tank 2 during the upward stroke of the piston 4, the hydraulic oil in the tank 2 is replenished into the cylinder 3 during the downward stroke of the piston 4, creating a large negative pressure. is prevented.

When the temperature of the hydraulic oil rises above a certain value by repeating the above-described operation, the bimetal 49 bends and the opening degree of the on-off valve 50 becomes smaller, as shown by the chain line in Fig. 2.3. The amount of replenishment of the hydraulic oil during the downward stroke of the piston 4 is limited, and the negative pressure inside the cylinder 3 becomes extremely high, causing cavitation.1 The air dissolved in the hydraulic oil is separated, and the insufficient amount of hydraulic oil is replenished. During the upward stroke of the piston 4, the amount of hydraulic oil passing through the relief valve 40 becomes extremely small, suppressing a rise in the temperature of the hydraulic oil, and when the temperature of the hydraulic oil decreases, the opening degree of the on-off valve 50 decreases. The size increases again, and as described above, the discharge of excess hydraulic oil to the tank 2 and the replenishment of hydraulic oil into the cylinder 3 are repeated.

Furthermore, in this embodiment, since the opening degree of the on-off valve 50 gradually changes according to changes in the temperature of the hydraulic oil, there is no fear that the scale of cavitation will change suddenly.

In the above embodiment, the on-off valve 50 using the bimetal 49 was used to control the amount of replenishment of the hydraulic oil, but instead of this, a throttle valve connected to a servo motor was connected to the pipe 45 serving as the replenishment passage. The amount of replenishment may be controlled by driving a servo motor using a signal from a temperature detection device for hydraulic oil provided in the tank 2 and changing the opening degree of the throttle valve.

Structure and Effects of the Invention As specifically explained in the above embodiments, the diaphragm pump of the present invention is capable of pumping hydraulic oil in a cylinder that communicates with a hydraulic oil chamber on one side of the diaphragm by reciprocating the piston with a constant stroke. The diaphragm is reciprocated by increasing and decreasing the pressure alternately, and the liquid in the liquid chamber on the other side is pressurized and fed, and the excess hydraulic oil in the hydraulic oil chamber during the pressurization stroke of the piston is transferred to the relief valve. In the diaphragm pump, the hydraulic oil is discharged into a tank through a replenishment passage, and the shortage of hydraulic oil in the hydraulic oil chamber during the decompression stroke of the piston is refilled from the tank through a replenishment passage. The gist of this system is to provide an on-off valve that reduces the degree of opening according to the rise in temperature, and when the pressure of the hydraulic oil in the hydraulic oil chamber rises above a certain value, the relief valve opens. During the pressure reduction process immediately after excess hydraulic oil is released into the tank, when the temperature of the hydraulic oil rises, the opening of the on-off valve installed in the replenishment passage becomes smaller, limiting the amount of replenishment of the hydraulic oil. The negative pressure in the hydraulic oil chamber increases, cavitation occurs, and the air molten in the hydraulic oil separates, replenishing the lack of hydraulic oil and reducing the amount of hydraulic oil discharged from the relief valve to an extremely small amount. , can suppress the temperature rise of hydraulic oil,
When the temperature of the hydraulic oil drops or is still low, the opening degree of the on-off valve is large and the hydraulic oil in the tank is refilled into the hydraulic oil chamber through the replenishment passage, creating a large negative pressure in the hydraulic oil chamber. This has the effect of eliminating the need for corrosion on the inner surface of the cylinder and wasted power associated with negative pressure operation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is an enlarged partially cutaway perspective view showing details of an on-off valve, and FIG. 3 is an enlarged sectional view of the same. 1: Body 2: Tank 3 Niji cylinder 4: Piston 8: Hydraulic oil chamber 11: Diaphragm 13: Liquid chamber 3
5: Discharge hole 40: Relief valve 42: Hole 43: Through hole 45: Pipe 47: Opening 49: Bimetal 50
: Open/close valve 1st W! J 2nd N strategy 3 times

Claims (1)

[Claims] The reciprocating motion of the piston with a constant stroke alternately increases and decreases the pressure of the hydraulic oil in the cylinder communicating with the hydraulic oil chamber on one side of the diaphragm, driving the diaphragm back and forth, and pressurizes the liquid in the liquid chamber on the other side. Along with pressure-feeding,
A surplus of hydraulic oil in the hydraulic oil chamber during the pressurization stroke of the piston is released into a tank via a relief valve, and a shortage of hydraulic oil in the hydraulic oil chamber during the depressurization stroke of the piston is removed from the tank through a replenishment passage. In the diaphragm pump configured to refill through the refill passage,
A diaphragm pump characterized by being equipped with an on-off valve that reduces the degree of opening according to the rise in the temperature of the hydraulic oil.