JPS622152B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a reciprocating pump with variable pressure and capacity, in which the drive shaft and plunger are formed by a hydraulic piston-cylinder configured to be able to adjust the buffering force and absorb the plunger stroke. The present invention relates to a control circuit for a reciprocating pump connected via a buffer mechanism.

BACKGROUND ART Conventionally, in so-called plunger pumps, when adjusting a set pressure, fluid in excess of the set pressure is often relieved from a pressure regulating valve provided in a fluid discharge circuit and discharged to the outside. On the other hand, the capacity is adjusted by changing the amount of eccentricity of the crankshaft, by adjusting the rotational speed of the pump, or by changing the diameter of the plunger. However, the conventional method described above has disadvantages such as being mechanically complex, requiring complicated operations, wasting unnecessary power, and making it difficult to obtain a stable discharge amount. .

In order to eliminate these conventional drawbacks, the present applicant has already applied for a reciprocating pump that has a simple structure and is equipped with a pressure/capacity adjustment mechanism that allows the pressure/capacity to be easily changed. That is, a fluid pressure cushion cylinder capable of absorbing the stroke of the plunger is provided between the drive shaft and the plunger,
We have proposed a system in which the pump discharge pressure and discharge amount can be adjusted simultaneously by adjusting the fluid pressure supplied to the cushion cylinder.

Fig. 1 is a diagram showing the basic principle of such a reciprocating pump, in which 1 is a pump device, 2 is a crankshaft, 3 is a connecting rod whose one end is rotatably supported by the crankshaft 2, and the other end is a crosshead. 4 is rotatably supported. The crosshead 4 is housed and supported so as to be able to slide in the axial direction on a support member 6 fixed on a base 5, and is reciprocated by the crankshaft 2 and connecting rod 3, and has a piston rod 7 at its front end. A low-pressure piston 8 having a predetermined pressurizing cross-sectional area is fixed to the end thereof.

Reference numeral 9 denotes a buffer mechanism, which includes a cylinder/piston device 12 consisting of a low-pressure piston 8 and a cushion cylinder 11, and a hydraulic pressure generating device connected to a cylinder chamber 16 formed in the cushion cylinder 11 by an oil feed pipe 13. 14 and a pressure accumulator 15.

A plunger 10 is fixed to the front end surface of the cushion cylinder 11 and slidably inserted into a discharge head 20 fixed to the base 5.

21 is a gasket, and 22 is a discharge circuit.

In such a configuration, a prime mover (not shown)
By rotating the crankshaft 2, the low pressure piston 8 reciprocates via the connecting rod 3, crosshead 4, and piston rod 7. The reciprocation of the low-pressure piston 8 causes the cushion cylinder 11 to reciprocate through the oil in the cylinder chamber 16, and the plunger 10 also reciprocates accordingly, discharging fluid from the discharge circuit 22. At this time, the maximum pressure discharged from the discharge circuit 22 is the product of the pressure in the cylinder chamber 16 and the pressurized cross-sectional area of the low-pressure piston 8, and the product of the pressure in the discharge circuit 22 and the pressurized cross-sectional area of the plunger 10. The pressure in the discharge circuit 22 is determined to be equal, and at discharge pressures lower than that, the rear end surface 17 of the low-pressure piston 8 and the rear end surface 18 of the cylinder chamber 16 operate with the rear end surface 17 always in contact with each other. That is, the low-pressure piston 8, the cushion cylinder 11, and the plunger 10 reciprocate as one, and the plunger 10 operates at its maximum stroke, which also maximizes the discharge amount. However, when the discharge pressure is about to exceed the maximum discharge pressure, the low-pressure piston 8 slides forward in the cushion cylinder 11 and sends the oil in the cylinder chamber 16 to the pressure accumulator 15, thereby reducing the stroke of the plunger 10. It acts to prevent the pressure inside the discharge circuit 22 from increasing any further. When retracting, the low-pressure piston 8 is pushed back by the hydraulic pressure of the pressure accumulator 15 to the extent that it slides forward in the cushion cylinder 11 during the forward movement, and the rear end surface 17 of the low-pressure piston 8 and the cylinder chamber 1
After the rear end surfaces 18 of the plungers 6 and 6 come into contact with each other, they move back together, causing the plunger 10 to move back.

However, when using such a pump device, it is common to communicate or disconnect between the discharge circuit 22 and the connected nozzle or other load; Since the prime mover (not shown) is still rotating even when the discharge of the gas stops, the gasket 21 continues to be subjected to repeated alternating loads.

Therefore, in the present invention, when the discharge circuit 22 is cut off, the pressure oil in the cylinder chamber 16 of the cushion cylinder 11 is released to lower the pressure in the cylinder chamber 16 and reduce the load on the packing 21. , extension of seal life and plunger 10,
Some attempts are made to reduce fatigue in areas such as the discharge head 20 that are subject to high pressure.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 2, 30 is a nozzle, and the fluid passage 4
1 is connected to a stop valve 31 which is a pilot type two-position two-way valve, and the stop valve 31 is connected to the discharge circuit 22.
It is connected to the. Reference numeral 32 designates a pilot switching valve using an electromagnetic two-position four-way valve, two sides of which are connected to the pilot ports of the stop valve 31 through pilot passages 42 and 43, respectively, and the other two sides connected to the hydraulic pump 37 of the hydraulic pressure generator 14, respectively. Discharge oil path 44
and is connected to the drain oil passage 48. 33 is a main switching valve that is an electromagnetic type two-position three-way valve, two sides of which are connected to an oil feed path 45 and a drain oil path 49 connected to the discharge oil path 44 of the hydraulic pump 37, and one side connected to the oil feed path 46. Oil feed line 13,1 through
3'. Reference numeral 34 denotes a relief type pressure control valve, which is connected to oil feed passages 45 and 46 via check valves 35 and 36, respectively. A and B
are pump devices installed in parallel so that they operate out of phase with each other.

The functions and effects of such a configuration are as follows.

FIG. 2 shows a case where the pilot switching valve 32 and the main switching valve 33 are energized at the same time and the stop valve 31 is in an open state. Hydraulic pressure generator 1
The oil discharged from 4 is sent to the cylinder chambers 16, 16' through the main switching valve 33, and the oil is sent to each cylinder chamber 16, 16'.
6 and 16' to a predetermined pressure. At the same time, the pilot passage 43 passes through the pilot switching valve 32.
The fluid is then sent to the pilot port of the stop valve 31 to maintain the stop valve 31 in an open state and inject the fluid from the nozzle 30 via the discharge circuit 22 and the fluid passage 41. At this time, pump devices A and B are configured to operate with different phases from each other so that when one is in the discharge stroke, the other is in the suction stroke, and pump device B is in the discharge stroke. If so,
The piston 8' moves forward together with the piston rod 7',
The plunger 10', that is, the cushion cylinder 11' moves forward by an amount corresponding to the amount of fluid discharged from the nozzle 30, and the difference in movement between the piston 8' and the cushion cylinder 11' is such that the piston 8' is moved forward by the amount corresponding to the amount of fluid discharged from the nozzle 30. It can be absorbed by sliding forward inside. At this time, the excess oil due to the volume reduction of the cylinder chamber 16' is removed from the cylinder chamber 1 of the pump device A which is in the suction process.
6, and excess oil is sent to oil pipe 1.
3', oil supply passages 46 and 47, and the reverse valve 36 before being released from the pressure regulating valve 34. On the contrary, cylinder chamber 1
If the amount of oil sent from 6' is less than the amount of oil required for the cylinder chamber 16, the insufficient amount will be taken from the hydraulic pump 37 via the discharge oil path 44, or the amount stored in the pressure accumulator 15 will be taken to the oil supply path. 45, the main switching valve 33, the oil feed path 46, and the oil feed pipe 13 to be supplied to the cylinder chamber 16. Pump devices A and B operate to the end of each stroke, and then the discharge and suction strokes are switched and operated. In this way, a plurality of pump devices can alternately perform discharge strokes and continuously inject fluid from the nozzle 30.

Next, when it is desired to stop the injection of fluid from the nozzle 30, the power to the pilot switching valve 32 is cut off, the pilot direction is switched, the pilot passage 43 is opened to the drain oil passage 48, and the pilot passage 42 is switched to hydraulic pressure. By opening the discharge oil passage 44 of the pump 37, the stop valve 31 is switched to shut off the discharge circuit 22 and the fluid passage 41;
The ejection of fluid from the nozzle 30 is stopped. The configuration is such that when the power supply to the pilot switching valve 32 is cut off, the power supply to the main switching valve 33 is also cut off, so that the pilot switching valve 32 and the main switching valve 33 are operated at the same time. As a result, the oil flowing from the hydraulic pump 37 through the discharge oil passage 44 and the oil supply pipe 45 is blocked by the main switching valve 33, and the oil in the cylinder chambers 16 and 16' is discharged through the oil supply passages 13 and 13' and the oil supply pipe 45. 46, the oil is discharged into the atmosphere from the drain oil passage 49 via the main switching valve 33, and the pressure in the cylinder chambers 16 and 16' is reduced to approximately atmospheric pressure. Here, the discharge circuit 2 is cut off by the stop valve 31.
2 is normally maintained in a high pressure state.
For this reason, even after the stop valve 31 is activated and the injection of fluid from the nozzle 30 is stopped, the pump devices A and B are still in operation, but the pressure in the cylinder chambers 16 and 16' is reduced. Also, since the discharge circuit 22 is maintained at high pressure, the plungers 10 and 1 during the discharge stroke
There is no before or after 0'; on the contrary, during the suction stroke, the pistons 8 and 8' force the cushion cylinders 11 and 11' to retreat, so the plungers 10 and 10' stop at the retreat end position. The pistons 8 and 8' slide back and forth within the cushion cylinders 11 and 11'. The oil in the cylinder chambers 16 and 16' only reciprocates between the cylinder chambers 16 and 16' because the pistons 8 and 8' operate so that when the volume of one decreases, the volume of the other increases. There is no leakage to the outside. For this reason, the oil in the buffer circuit including the cylinder chambers 16 and 16' that is drained by the main switching valve 33 is only for the initial pressure drop, and is not drained during the subsequent no-load operation of the pump. It is. By lowering the pressure in the cylinder chambers 16 and 16' to approximately atmospheric pressure, the force with which the pistons 8 and 8' press against the plungers 10 and 10' becomes smaller, and therefore the pressure in the variable pressure chambers 23 and 23' is not increased. Since the pressure is low, the force acting on the gaskets 21 and 21' is extremely small compared to when the pressure is increased, and it can be said that it has no effect. Of course, the same applies not only to the gaskets 21 and 21' but also to the plungers 10 and 10' and the discharge heads 20 and 20'.

Then, in order to inject fluid from the nozzle 30 again, the pilot switching valve 32 is energized to switch the pilot direction, and the stop valve 3
1 to open the discharge circuit 22 and fluid passage 41. At the same time, the main switching valve 33 is also energized to increase the pressure in the cylinder chambers 16 and 16', causing fluid to be injected from the nozzle 30.

As described in detail above, even if the fluid supply to a load such as a nozzle is stopped, the pump device usually remains in operation, and in this case, the suction and discharge of the gasket and other parts where high pressure is applied Since the process is subjected to repeated alternating loads of high pressure and low pressure, there were problems such as shortened life.However, with the structure of the present invention, operation without load is possible, and the life due to fatigue can be reduced. This greatly improved the decline in

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a reciprocating pump according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 11...Cushion cylinder, 14...Hydraulic pressure generator, 16...Cylinder chamber, 22...Discharge circuit, 30...Nozzle, 31...Stop valve, 32...
Pilot switching valve, 35...Check valve, 36...
...Check valve, 42...Pilot passage, 43...Pilot passage, 33...Main switching valve, 34...
Pressure control valve.

Claims (1)

[Claims] 1 A pump that causes a plunger to reciprocate using a drive shaft, in which the drive shaft and the plunger are connected via a buffer mechanism composed of a fluid pressure cylinder that can adjust the buffer force and absorb the plunger stroke. In variable capacity reciprocating pumps,
A stop valve that is operated by a fluid pressure pilot and opens and closes the flow path between the discharge port and the load, an electromagnetic pilot switching valve that controls the stop valve, and a stop valve that is operated by a fluid pressure pilot to control the flow path. A variable pressure/capacity reciprocating pump comprising a main electromagnetic switching valve that supplies fluid from a fluid pressure generating device to the cylinder chamber of the cylinder and communicates the cylinder chamber with the tank when the stop valve closes the flow path. control circuit.