CA2974845C - Constant power regulation system for duplex axial plunger pump and applications thereof - Google Patents
Constant power regulation system for duplex axial plunger pump and applications thereof Download PDFInfo
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- CA2974845C CA2974845C CA2974845A CA2974845A CA2974845C CA 2974845 C CA2974845 C CA 2974845C CA 2974845 A CA2974845 A CA 2974845A CA 2974845 A CA2974845 A CA 2974845A CA 2974845 C CA2974845 C CA 2974845C
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/22—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves
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Abstract
A constant power regulation system for a duplex axial plunger pump comprises a main valve body (001), an outer spring regulation screw (703), an inner spring regulation screw (701), an outer spring regulation nut (704), and an inner spring regulation nut (702). The main valve body (001) comprises an outer spring (706), an inner spring (708), a compensation rod (801), a compensation spool (802), and a compensation piston (805). The main valve body further comprises an inner spring converter (707), an outer spring converter (709), and a spring seat (710). The inner spring (708) is located between the inner spring converter (707) and the spring seat (710). The inner spring converter (707) runs through the outer spring (706) and the outer spring converter (709). One end of the outer spring (706) is in contact with the outer spring regulation screw (703), and the other end is in contact with the outer spring converter (709). The outer spring converter (709) is in contact with the inner spring converter (707) in a cooperative manner, and a gap is formed between the inner spring converter (707) and the inner spring regulation screw (701) and between the inner spring converter (707) and the spring seat (710). The inner spring converter and the outer spring converter enable the two springs to show four spring stiffness features in the compression process, and the fitting degree of a feature curve of the four shown comprehensive stiffness coefficients and a theoretical constant power hyperbolic curve is higher in the constant power regulation process. The mechanism can greatly increase the energy utilization rate of the plunger pump when the plunger pump works within the pressure load range of 15 MPa to 25 MPa; the overload state in which the plunger pump and a prime mover work is effectively avoided, thereby prolonging the service life of hardware.
Description
CONSTANT POWER REGULATION SYSTEM FOR DUPLEX AXIAL PLUNGER PUMP
AND APPLICATIONS THEREOF
I. Technical Field The present invention relates to a constant power regulation system for a duplex axial plunger pump and applications thereof, and belongs to the technical field of hydraulic drive components.
II. Background Art As main components of hydraulic power elements, plunger pumps are mainly applied under high-pressure, high-flow-rate and high-power operating conditions.
In hydraulic systems applied for engineering machinery (e.g., hydraulic excavators), in view that the flow rates required by the actuating elements vary a lot in an operating cycle, multiplex pumps are used more and more in order to attain purposes of convenient control, energy saving, fluctuation reduction, and coordinated actions, wherein, duplex axial plunger pumps are the most widely applied ones.
Duplex axial plunger pumps are usually used in combination with prime engines (e.g., diesel engines). Major brands and models of duplex axial plunger pumps available in the market (e.g., K3V series plunger pumps designed and manufactured by Kawasaki Heavy Industries, Ltd.) utilize a constant power regulation system during operation to ensure that the plunger pump can take full advantage of the output power of the prime engine, avoid overload of the prime engine, and attain a purpose of saving energy and improving operating efficiency; the working principle of a constant power regulation system is to collect workload pressure signals, balance the force for preset parallel springs, amplify the output displacement signals, and thereby regulate the = =
output capacity of the plunger pump; the operating cycle consists of three stages, i.e., uncompressed stage, single spring compression stage, and parallel spring compression stage, owing to that the two preset parallel springs are different from each other in free length, and are fitted and mounted at different positions.
Corresponding to the three operating stages, the curve of pressure load vs.
output flow of the plunger pump also consists of three stages, as shown in the Curve (3) in Fig.
1. Suppose the stiffness coefficients of the inner spring and outer spring of the plunger pump are k1 and k2 respectively and the overall stiffness coefficient of the parallel spring set is 1(0 during operation, the segment AB is an uncompressed stage in which both springs are uncompressed (k0=00), the segment BD is a signal spring compression stage (k0=k1) in which only one of the spring is compressed, and the segment DE is a parallel spring compression stage (k0=k1+k2) in which both springs are compressed; the slope of the straight line is directly related with the overall stiffness coefficient kip; the Curve (1) in Fig. 1 is a theoretical constant power hyperbolic curve in the constant power regulation process. The closer the actual regulation curve is to the theoretical constant power hyperbolic curve (1) (i.e., the higher the degree of fitting is), the higher the utilization ratio of the output power of the prime engine by the hydraulic pump is, and the higher the efficiency of the hydraulic pump is.
It is seen from the Curves (1) and (3) in Fig. 1, when the pressure load is within a range of 15-25MPa, the degree of fitting of the constant power characteristic curve to the theoretical curve is not high, and the energy waste is severe; theoretically, as the quantity of the springs is increased, the constant power regulation characteristic curve of the pump has more segments and is closer to the theoretical constant power hyperbolic curve; thus, optimal regulating characteristics can be obtained. However, excessive springs result in increased difficulty of = 2=
design and cost of the variable displacement mechanism, and complex structure will result in reduced system stability, just opposite to what one wishes.
HI. Contents of the Invention To overcome the drawbacks in the prior art, the present invention provides a constant power regulation system for a duplex axial plunger pump, which shows more spring stiffness coefficients without additional springs.
The present invention further provides a regulator that includes the above constant power regulation system for a duplex axial plunger pump.
The present invention further provides a duplex axial plunger pump that includes the above regulator.
The technical scheme of the present invention is as follows:
A constant power regulation system for a duplex axial plunger pump, comprising a main valve body, an outer spring adjusting screw, an inner spring adjusting screw, an outer spring adjusting nut and an inner spring adjusting nut, wherein, the main valve body comprises an outer spring, an inner spring, a compensation rod, a compensation valve spool and a compensation piston; the two ends of the main valve body are provided with a hydraulic side cover and a spring side cover respectively, the outer spring adjusting screw is mounted onto the main valve body via the spring side cover and fixed by the outer spring adjusting nut, the inner spring adjusting screw penetrates through the outer spring adjusting screw and is fixed by the inner spring adjusting nut; wherein, the main valve body further comprises an inner spring converter, an outer spring converter, and a spring seat, the inner spring is disposed between the inner spring converter and the spring seat, the inner spring converter penetrates through the outer spring and the outer spring converter, one end of the outer spring contacts with the outer spring adjusting screw, the other end of the outer spring contacts with the outer spring converter, the outer spring converter is fitted and contacts with the inner spring converter, and clearance is reserved between the inner spring converter and the inner spring adjusting screw/the spring seat.
Preferably, the inner spring converter is in a shape of a cylinder that has a cavity, the inner spring is arranged in the cavity, and one end of the inner spring adjusting screw penetrates through the inner spring converter and the inner spring.
Preferably, the outer spring converter is a circular ring with a stepped hole, the inner spring converter is arranged with a flange extending outwardly at the edge of one end, and the flange is in the stepped hole when the outer spring converter is fitted and contacts with the inner spring converter. An advantage of the design is that the outer spring converter is fitted with the inner spring converter more closely and the fitting accuracy is higher by virtue of the contact fitting between the flange and the stepped hole.
Preferably, the spring seat is arranged with a conical groove on one side and a boss on the other side, a groove for accommodating the flange is arranged around outer side of the boss, the boss is embedded in the inner spring, and one end of the compensation rod is located in the conical socket.
A regulator, comprising the above-mentioned constant power regulation system, a negative flow feedback regulation system, and a valve-controlled cylinder position servo system, wherein, the negative flow feedback regulation system comprises a negative flow feedback oil cylinder, and the valve-controlled cylinder position servo system comprises a servo valve, a feedback rod, a servo plunger, and a differential cylinder; the compensation rod and the negative flow feedback = 4 =
oil cylinder are connected with the servo valve respectively and configured to control the movement of the valve spool of the servo valve; the servo plunger is arranged in the differential cylinder and connected with the servo valve via the feedback rod, and configured to control the movement of the valve spool of the servo valve via the feedback rod.
A duplex axial plunger pump includes the above-mentioned regulator.
An operating method of a duplex axial plunger pump, comprising the following steps:
When the operating pressure of the plunger pump is increased gradually from zero load and hasn't reached preset operating power of the plunger pump yet, the outlet pressure of the plunger pump increases accordingly and the force suffered by the compensation valve spool increases gradually, but the leftward acting force generated by the compensation valve spool is still lower than the rightward pre-tightening force applied by the inner spring and outer spring; in that state, the compensation rod has no displacement, the servo valve and the servo plunger do not make any movement, and the plunger pump still outputs with maximum pump discharge;
As the operating pressure of the plunger pump is increased further and reaches the preset operating power of the plunger pump, the outlet pressure of the plunger pump increases accordingly, and the force suffered by the compensation valve spool increases gradually; at that point, the leftward acting force generated by the compensation valve spool overcomes the rightward pre-tightening force of the inner spring and outer spring, the compensation rod is displaced leftwards and pushes the inner spring converter to move leftwards accordingly, and drives the servo valve when it moves leftward; under the action of the servo valve, the big cavity end of the servo plunger is open to the high-pressure oil, the servo plunger is displaced rightwards, and thereby the inclination angle of the swash plate of the plunger pump is decreased = 5 =
and the displacement of the plunger pump is decreased;
As the operating pressure of the plunger pump is increased further, the compensation rod moves leftward further, till the inner spring converter comes in contact with the inner spring adjusting screw;
As the operating pressure of the plunger pump is continuously increased, the compensation rod moves leftwards continuously; however, since the inner spring converter has come into contact with the fixed inner spring adjusting screw, only the inner spring is further compressed.
As the operating pressure of the plunger pump is continuously increased, the compensation rod moves leftwards continuously; when the spring seat comes into contact with the outer spring converter, the flange is disengaged from the stepped hole gradually and no longer contacts with the stepped hole, the outer spring converter moves leftwards separately, and the spring seat compresses the inner spring and the outer spring simultaneously;
When the operating pressure of the plunger pump is decreased, the outlet pressure of the plunger pump decreases accordingly, and the regulation process is contrary to the regulation process when the operating pressure of the plunger pump is increased.
The present invention attains the following beneficial effects:
By improving the constant power regulation system in a duplex axial plunger pump, a novel spring assembling mechanism, namely a series-parallel converter (including an inner spring converter and an outer spring converter) is designed at the positions of an inner spring and an outer spring in the present invention, so that the two springs show four types of spring stiffness characteristics in the compression process by virtue of the series-parallel converter, and the degree of fitting of the characteristic curve of the four overall stiffness coefficients to a = 6 .
theoretical constant power hyperbolic curve is higher in the constant power regulation process;
utilizing the mechanism, the energy efficiency of the plunger pump can be greatly improved when the plunger pump works within a pressure load range of 15-25 MPa; the overload state of the plunger pump and a prime engine is effectively avoided, thereby prolonging the service life of hardware.
IV. Description of Drawings Fig. 1 shows a characteristic curve of pressure load vs. output flow;
Fig. 2 shows the working principle of the regulator;
Fig. 3 is a schematic structural diagram of the constant power regulation system;
Fig. 4 is a schematic structural diagram of the compensation rod;
Fig. 5 is a schematic structural diagram of the compensation valve spool;
Fig. 6a is a front view of the spring seat;
Fig. 6b is a right sectional view of the spring seat;
Fig. 7a is a front view of the inner spring converter;
Fig. 7b is a left sectional view of the inner spring converter;
Fig. 8a is a front view of the outer spring converter;
Fig. 8b is a left sectional view of the outer spring converter;
Fig. 9 is a state diagram when the inner spring and the outer spring are compressed in serial connection;
.7.
Fig. 10 is a state diagram when the inner spring is compressed;
Fig. 11 is a state diagram when the compression of the inner spring ends/the compression of the inner spring and the outer spring in parallel connection starts;
Fig. 12 is a state diagram when the compression of the inner spring and the outer spring in parallel connection ends;
Fig. 13 is a functional block diagram of the duplex axial plunger pump in the present invention;
In the figures: 1 - pilot pump; 2 - rear pump; 3 - front pump; 4 - prime engine; 5 - differential cylinder; 6 - negative flow feedback oil cylinder; 7 - spring force compensation mechanism; 8 -hydraulic pressure compensation mechanism; 9 - solenoid proportional pressure reducing valve;
- servo valve; 11 - feedback rod; 12 - servo plunger; 001 - main valve body;
002 - hydraulic side cover; 701 - inner spring adjusting screw; 702 - inner spring adjusting nut; 703 - outer spring adjusting screw; 704 - outer spring adjusting nut; 705 - spring side cover; 706 - outer spring; 707 - inner spring converter; 708 - inner spring; 709 - outer spring converter; 710 - spring seat; 801 - compensation rod; 802 - compensation valve spool; 803 -compensation valve sleeve;
804 - compensation plug; 805 - compensation piston; 8011 - are head; 8012 -annular groove;
8013 - tail base of compensation rod; 8021 - arc head of compensation valve spool; 8022 - acting surface of this pump; 8023 - acting surface of other pump; 8024 - tail base of compensation valve spool; 7101 - boss; 7102 - right contact base for inner spring; 7103 -parallel compressing surface; 7104 - conical socket; 7105 - groove; 7071 - limit end surface; 7072 -assembly hole;
7073 - left contact base for inner spring; 7074 - flange; 7091 - right contact base for outer spring;
7092 - parallel compression surface; 7093 - stepped hole;
= 8 =
V. Embodiments Hereunder the present invention will be further detailed in embodiments with reference to the accompanying drawings, but the present invention is not limited to those embodiments.
Embodiment 1:
This embodiment provides a constant power regulation system for a duplex axial plunger pump.
The constant power regulation system is a constant power regulation system in a regulator on a plunger pump. The structure of the constant power regulation system is shown in Fig. 3. The main valve body 001 mainly includes a spring force compensation mechanism 7 and a hydraulic pressure compensation mechanism 8, wherein, the spring force compensation mechanism 7 mainly comprises an inner spring adjusting screw 701, an inner spring adjusting nut 702, an outer spring adjusting screw 703, an outer spring adjusting nut 704, a spring side cover 705, an outer spring 706, an inner spring converter 707, an inner spring 708, an outer spring converter 709, a spring seat 710, and seal rings, etc. The hydraulic pressure compensation mechanism 8 mainly comprises a compensation rod 801, a compensation valve spool 802, a compensation valve sleeve 803, a compensation plug 804, a compensation piston 805, and seal rings, etc.
The main valve body 001 is provided with the spring side cover 705 and a hydraulic side cover 002 on the two ends thereof, the inner spring 708 is disposed between the inner spring converter 707 and the spring seat 710, the inner spring converter 707 penetrates through the outer spring 706 and the outer spring converter 709, one end of the outer spring 706 contacts with the spring side cover 705, the other end of the outer spring 706 contacts with the outer spring converter 709, the outer spring converter 709 is fitted and contacts with the inner spring converter 707, and clearance is reserved between the inner spring converter 707 and the inner spring adjusting screw = 9 =
701/the spring seat 710.
The outer spring adjusting screw 703 is mounted on the main valve body 001 via the spring side cover 705, and is fixed via a threaded connection with the outer spring adjusting nut 704; the inner spring adjusting screw 701 is in a shape of a stepped shaft and includes a shaft shoulder, one end of the inner spring adjusting screw 701 penetrates through the outer spring adjusting screw 703, the inner spring converter 707, and the inner spring 708, the other end of the inner spring adjusting screw 701 is fixed via a threaded connection with the inner spring adjusting nut 702, clearance is reserved between the shaft shoulder of the inner spring adjusting screw 701 and the inner spring converter 707/the outer spring adjusting screw 703, the pre-tightening forces of the outer spring and the inner spring are adjusted by adjusting the penetration depths of the outer spring screw and the inner spring screw in the main valve body.
Wherein, the inner spring converter is in a shape of a cylinder, which, as shown in Figs. 7a and 7b, includes a cavity and an assembly hole communicating with the cavity, the inner spring is arranged on the left contact base for inner spring 7073 on the left side in the cavity, and one end of the inner spring adjusting screw 701 penetrates through the assembly hole 7072 in the inner spring converter and then is disposed in the inner spring 708.
The outer spring converter 709 is a circular ring with a stepped hole, as shown in Figs. 8a and 8b, a flange 7074 extending outwardly is arranged at the edge of one end of the cylinder, and the flange 7074 is located in the stepped hole 7093 when the outer spring converter 709 is fitted and contacts with the inner spring converter 707. The outer spring converter is fitted with the inner spring converter more closely and the fitting accuracy is higher by virtue of the contact fitting between the flange and the stepped hole.
=
As shown in Figs. 6a and 6b, the spring holder 710 is arranged with a conical groove 7104 on one side and a boss 7101 on the other side, a groove 7105 for accommodating the flange 7074 is arranged around the outer side of the boss 7101, and the boss 7101 is embedded in the inner spring 708. The structure of the compensation rod 801 is shown in Fig. 4. The compensation rod 801 comprises a conical arc head 8011, an annular groove 8012, and a tail base of compensation rod 8013, the conical arc head 8011 at the left end of the compensation rod is fitted in the conical groove 7104, the annular groove 8012 is connected with the valve spool of the servo valve 10 in a valve-controlled cylinder position servo system, the tail base of compensation rod 8013 at the right end is subjected to the acting force of an arc head of compensation valve spool 8021 at the left end of the compensation valve spool 802.
As shown in Figs. 6a and 6b, the spring seat 710 is subjected to the force of two springs at the left end, wherein, the boss 7101 is fitted with an inner circle of the inner spring 708, a right contact base for inner spring 7102 is fitted and contacts with the right end surface of the inner spring to support the inner spring 708, a parallel compressing surface 7103 is fitted and contacts with a parallel compression surface 7092 of the outer spring converter 709, and the conical groove 7104 is fitted and contacts with the conical arc head 8011 of the compensation rod;
The inner spring 708, outer spring 706, inner spring converter 707, and outer spring converter 709 constitute a series-parallel converter. The distance between the limit end surface 7071 of the inner spring converter 707 and the shaft shoulder of the inner spring adjusting screw 701 determines the pressure range in which the inner spring 708 and the outer spring 706 are in a serial operating state, the assembly hole 7072 is fitted with the inner spring adjusting screw 701, the left contact base for inner spring 7073 contacts with the left end surface of the inner spring, and the flange 7074 is fitted and contacts with the stepped hole 7093;
= 11 =
The right contact base for outer spring 7091 of the outer spring converter 709 contacts with the right end surface of the outer spring 706, the parallel compression surface 7092 can be fitted and contact with the parallel compressing surface 7103, and the stepped hole 7093 is fitted with the flange 7074;
The compensation valve spool 802 has a stepped annular structure as shown in Fig. 5, and is disposed in the compensation valve sleeve 803. The arc head of compensation valve spool 8021 at the left end contacts with the tail base of compensation rod 8013, the annular acting surface of this pump 8022 and the annular acting surface of other pump 8023 in the middle are subjected from outlet pressures Pi and P2 of front pump 3 and rear pump 2 of the duplex axial plunger pump respectively, the tail base of compensation valve spool 8024 at the right end is subjected to the acting force of the compensation piston 805, the compensation piston 805 is located in the compensation valve sleeve 803 through the sleeve compensation plug 804, and the compensation valve sleeve 803 is disposed in the main valve body 001, wherein, the left end of the compensation piston 805 communicates with the low-pressure oil in the oil tank, and the hydraulic pressure at the right end comes from the solenoid proportional pressure reducing valve outlet pressure Pf of the solenoid proportional pressure reducing valve 9 on the plunger pump.
On the basis of a conventional constant power regulation system, the constant power regulation system provided in this embodiment is designed with a novel spring assembling mechanism, namely a series-parallel converter (including an inner spring converter and an outer spring converter), so that the two springs show four types of spring stiffness characteristics in the compression process by virtue of the series-parallel converter, and the degree of fitting of the characteristic curve of the four overall stiffness coefficients to a theoretical constant power hyperbolic curve is higher in the constant power regulation process; utilizing the mechanism, the =12=
energy efficiency of the plunger pump can be greatly improved when the plunger pump works within a pressure load range of 15-25 MPa; the overload state of the plunger pump and a prime engine is effectively avoided, thereby prolonging the service life of hardware.
Embodiment 2:
This embodiment provides a regulator used on a duplex axial plunger pump. The regulator comprises the constant power regulation system for a duplex axial plunger pump described in the embodiment 1 (comprising a spring force compensation mechanism 7 and a hydraulic pressure compensation mechanism 8), a negative flow feedback regulation system (comprising a negative flow feedback oil cylinder 6), and a set of valve-controlled cylinder position servo system (mainly comprising a differential cylinder 5, a servo valve 10, a feedback rod 11, and a servo plunger 12). The negative flow feedback oil cylinder 6 is connected with the servo valve 10 in the valve-controlled cylinder position servo system to control the movement of the valve spool of the servo valve 10, the constant power regulation system is connected with the servo valve 10 in the valve-controlled cylinder position servo system via the compensation rod 801 of the hydraulic pressure compensation mechanism 8 to control the movement of the valve spool of the servo valve 10 by means of the movement of the compensation rod, the servo plunger 12 is disposed in the differential cylinder 5 and connected with the servo valve 10 via the feedback rod 11 to control the movement of the valve spool of the servo valve 10 via the feedback rod 11;
there is no connection relationship between the constant power regulation system and the negative flow feedback system; in addition, the constant power regulation system and the negative flow feedback system are controlled in an appropriate manner so that only one of them operates.
= 13 =
Embodiment 3:
This embodiment provides a duplex axial plunger pump that has the structure shown in Fig. 2.
The duplex axial plunger pump comprises a pilot pump 1, main pumps (a front pump 3 and a rear pump 2), a solenoid proportional pressure reducing valve 9, and regulators as described in the embodiment 2 mounted on the front pump 3 and rear pump 2 respectively.
In an actual hydraulic power system, the duplex axial plunger pump is usually connected with a prime engine, which, in this embodiment, is a diesel engine. The prime engine 4 drives the two axial plunger pumps (rear pump 2 and front pump 3) connected in series and the pilot pump I
mounted at the tail portion via the input shafts, wherein, the plunger pumps provide high-pressure power oil to operating actuator elements, and the pilot gear pump provides high-pressure oil to a control oil circuit. The front pump 3 and the rear pump
AND APPLICATIONS THEREOF
I. Technical Field The present invention relates to a constant power regulation system for a duplex axial plunger pump and applications thereof, and belongs to the technical field of hydraulic drive components.
II. Background Art As main components of hydraulic power elements, plunger pumps are mainly applied under high-pressure, high-flow-rate and high-power operating conditions.
In hydraulic systems applied for engineering machinery (e.g., hydraulic excavators), in view that the flow rates required by the actuating elements vary a lot in an operating cycle, multiplex pumps are used more and more in order to attain purposes of convenient control, energy saving, fluctuation reduction, and coordinated actions, wherein, duplex axial plunger pumps are the most widely applied ones.
Duplex axial plunger pumps are usually used in combination with prime engines (e.g., diesel engines). Major brands and models of duplex axial plunger pumps available in the market (e.g., K3V series plunger pumps designed and manufactured by Kawasaki Heavy Industries, Ltd.) utilize a constant power regulation system during operation to ensure that the plunger pump can take full advantage of the output power of the prime engine, avoid overload of the prime engine, and attain a purpose of saving energy and improving operating efficiency; the working principle of a constant power regulation system is to collect workload pressure signals, balance the force for preset parallel springs, amplify the output displacement signals, and thereby regulate the = =
output capacity of the plunger pump; the operating cycle consists of three stages, i.e., uncompressed stage, single spring compression stage, and parallel spring compression stage, owing to that the two preset parallel springs are different from each other in free length, and are fitted and mounted at different positions.
Corresponding to the three operating stages, the curve of pressure load vs.
output flow of the plunger pump also consists of three stages, as shown in the Curve (3) in Fig.
1. Suppose the stiffness coefficients of the inner spring and outer spring of the plunger pump are k1 and k2 respectively and the overall stiffness coefficient of the parallel spring set is 1(0 during operation, the segment AB is an uncompressed stage in which both springs are uncompressed (k0=00), the segment BD is a signal spring compression stage (k0=k1) in which only one of the spring is compressed, and the segment DE is a parallel spring compression stage (k0=k1+k2) in which both springs are compressed; the slope of the straight line is directly related with the overall stiffness coefficient kip; the Curve (1) in Fig. 1 is a theoretical constant power hyperbolic curve in the constant power regulation process. The closer the actual regulation curve is to the theoretical constant power hyperbolic curve (1) (i.e., the higher the degree of fitting is), the higher the utilization ratio of the output power of the prime engine by the hydraulic pump is, and the higher the efficiency of the hydraulic pump is.
It is seen from the Curves (1) and (3) in Fig. 1, when the pressure load is within a range of 15-25MPa, the degree of fitting of the constant power characteristic curve to the theoretical curve is not high, and the energy waste is severe; theoretically, as the quantity of the springs is increased, the constant power regulation characteristic curve of the pump has more segments and is closer to the theoretical constant power hyperbolic curve; thus, optimal regulating characteristics can be obtained. However, excessive springs result in increased difficulty of = 2=
design and cost of the variable displacement mechanism, and complex structure will result in reduced system stability, just opposite to what one wishes.
HI. Contents of the Invention To overcome the drawbacks in the prior art, the present invention provides a constant power regulation system for a duplex axial plunger pump, which shows more spring stiffness coefficients without additional springs.
The present invention further provides a regulator that includes the above constant power regulation system for a duplex axial plunger pump.
The present invention further provides a duplex axial plunger pump that includes the above regulator.
The technical scheme of the present invention is as follows:
A constant power regulation system for a duplex axial plunger pump, comprising a main valve body, an outer spring adjusting screw, an inner spring adjusting screw, an outer spring adjusting nut and an inner spring adjusting nut, wherein, the main valve body comprises an outer spring, an inner spring, a compensation rod, a compensation valve spool and a compensation piston; the two ends of the main valve body are provided with a hydraulic side cover and a spring side cover respectively, the outer spring adjusting screw is mounted onto the main valve body via the spring side cover and fixed by the outer spring adjusting nut, the inner spring adjusting screw penetrates through the outer spring adjusting screw and is fixed by the inner spring adjusting nut; wherein, the main valve body further comprises an inner spring converter, an outer spring converter, and a spring seat, the inner spring is disposed between the inner spring converter and the spring seat, the inner spring converter penetrates through the outer spring and the outer spring converter, one end of the outer spring contacts with the outer spring adjusting screw, the other end of the outer spring contacts with the outer spring converter, the outer spring converter is fitted and contacts with the inner spring converter, and clearance is reserved between the inner spring converter and the inner spring adjusting screw/the spring seat.
Preferably, the inner spring converter is in a shape of a cylinder that has a cavity, the inner spring is arranged in the cavity, and one end of the inner spring adjusting screw penetrates through the inner spring converter and the inner spring.
Preferably, the outer spring converter is a circular ring with a stepped hole, the inner spring converter is arranged with a flange extending outwardly at the edge of one end, and the flange is in the stepped hole when the outer spring converter is fitted and contacts with the inner spring converter. An advantage of the design is that the outer spring converter is fitted with the inner spring converter more closely and the fitting accuracy is higher by virtue of the contact fitting between the flange and the stepped hole.
Preferably, the spring seat is arranged with a conical groove on one side and a boss on the other side, a groove for accommodating the flange is arranged around outer side of the boss, the boss is embedded in the inner spring, and one end of the compensation rod is located in the conical socket.
A regulator, comprising the above-mentioned constant power regulation system, a negative flow feedback regulation system, and a valve-controlled cylinder position servo system, wherein, the negative flow feedback regulation system comprises a negative flow feedback oil cylinder, and the valve-controlled cylinder position servo system comprises a servo valve, a feedback rod, a servo plunger, and a differential cylinder; the compensation rod and the negative flow feedback = 4 =
oil cylinder are connected with the servo valve respectively and configured to control the movement of the valve spool of the servo valve; the servo plunger is arranged in the differential cylinder and connected with the servo valve via the feedback rod, and configured to control the movement of the valve spool of the servo valve via the feedback rod.
A duplex axial plunger pump includes the above-mentioned regulator.
An operating method of a duplex axial plunger pump, comprising the following steps:
When the operating pressure of the plunger pump is increased gradually from zero load and hasn't reached preset operating power of the plunger pump yet, the outlet pressure of the plunger pump increases accordingly and the force suffered by the compensation valve spool increases gradually, but the leftward acting force generated by the compensation valve spool is still lower than the rightward pre-tightening force applied by the inner spring and outer spring; in that state, the compensation rod has no displacement, the servo valve and the servo plunger do not make any movement, and the plunger pump still outputs with maximum pump discharge;
As the operating pressure of the plunger pump is increased further and reaches the preset operating power of the plunger pump, the outlet pressure of the plunger pump increases accordingly, and the force suffered by the compensation valve spool increases gradually; at that point, the leftward acting force generated by the compensation valve spool overcomes the rightward pre-tightening force of the inner spring and outer spring, the compensation rod is displaced leftwards and pushes the inner spring converter to move leftwards accordingly, and drives the servo valve when it moves leftward; under the action of the servo valve, the big cavity end of the servo plunger is open to the high-pressure oil, the servo plunger is displaced rightwards, and thereby the inclination angle of the swash plate of the plunger pump is decreased = 5 =
and the displacement of the plunger pump is decreased;
As the operating pressure of the plunger pump is increased further, the compensation rod moves leftward further, till the inner spring converter comes in contact with the inner spring adjusting screw;
As the operating pressure of the plunger pump is continuously increased, the compensation rod moves leftwards continuously; however, since the inner spring converter has come into contact with the fixed inner spring adjusting screw, only the inner spring is further compressed.
As the operating pressure of the plunger pump is continuously increased, the compensation rod moves leftwards continuously; when the spring seat comes into contact with the outer spring converter, the flange is disengaged from the stepped hole gradually and no longer contacts with the stepped hole, the outer spring converter moves leftwards separately, and the spring seat compresses the inner spring and the outer spring simultaneously;
When the operating pressure of the plunger pump is decreased, the outlet pressure of the plunger pump decreases accordingly, and the regulation process is contrary to the regulation process when the operating pressure of the plunger pump is increased.
The present invention attains the following beneficial effects:
By improving the constant power regulation system in a duplex axial plunger pump, a novel spring assembling mechanism, namely a series-parallel converter (including an inner spring converter and an outer spring converter) is designed at the positions of an inner spring and an outer spring in the present invention, so that the two springs show four types of spring stiffness characteristics in the compression process by virtue of the series-parallel converter, and the degree of fitting of the characteristic curve of the four overall stiffness coefficients to a = 6 .
theoretical constant power hyperbolic curve is higher in the constant power regulation process;
utilizing the mechanism, the energy efficiency of the plunger pump can be greatly improved when the plunger pump works within a pressure load range of 15-25 MPa; the overload state of the plunger pump and a prime engine is effectively avoided, thereby prolonging the service life of hardware.
IV. Description of Drawings Fig. 1 shows a characteristic curve of pressure load vs. output flow;
Fig. 2 shows the working principle of the regulator;
Fig. 3 is a schematic structural diagram of the constant power regulation system;
Fig. 4 is a schematic structural diagram of the compensation rod;
Fig. 5 is a schematic structural diagram of the compensation valve spool;
Fig. 6a is a front view of the spring seat;
Fig. 6b is a right sectional view of the spring seat;
Fig. 7a is a front view of the inner spring converter;
Fig. 7b is a left sectional view of the inner spring converter;
Fig. 8a is a front view of the outer spring converter;
Fig. 8b is a left sectional view of the outer spring converter;
Fig. 9 is a state diagram when the inner spring and the outer spring are compressed in serial connection;
.7.
Fig. 10 is a state diagram when the inner spring is compressed;
Fig. 11 is a state diagram when the compression of the inner spring ends/the compression of the inner spring and the outer spring in parallel connection starts;
Fig. 12 is a state diagram when the compression of the inner spring and the outer spring in parallel connection ends;
Fig. 13 is a functional block diagram of the duplex axial plunger pump in the present invention;
In the figures: 1 - pilot pump; 2 - rear pump; 3 - front pump; 4 - prime engine; 5 - differential cylinder; 6 - negative flow feedback oil cylinder; 7 - spring force compensation mechanism; 8 -hydraulic pressure compensation mechanism; 9 - solenoid proportional pressure reducing valve;
- servo valve; 11 - feedback rod; 12 - servo plunger; 001 - main valve body;
002 - hydraulic side cover; 701 - inner spring adjusting screw; 702 - inner spring adjusting nut; 703 - outer spring adjusting screw; 704 - outer spring adjusting nut; 705 - spring side cover; 706 - outer spring; 707 - inner spring converter; 708 - inner spring; 709 - outer spring converter; 710 - spring seat; 801 - compensation rod; 802 - compensation valve spool; 803 -compensation valve sleeve;
804 - compensation plug; 805 - compensation piston; 8011 - are head; 8012 -annular groove;
8013 - tail base of compensation rod; 8021 - arc head of compensation valve spool; 8022 - acting surface of this pump; 8023 - acting surface of other pump; 8024 - tail base of compensation valve spool; 7101 - boss; 7102 - right contact base for inner spring; 7103 -parallel compressing surface; 7104 - conical socket; 7105 - groove; 7071 - limit end surface; 7072 -assembly hole;
7073 - left contact base for inner spring; 7074 - flange; 7091 - right contact base for outer spring;
7092 - parallel compression surface; 7093 - stepped hole;
= 8 =
V. Embodiments Hereunder the present invention will be further detailed in embodiments with reference to the accompanying drawings, but the present invention is not limited to those embodiments.
Embodiment 1:
This embodiment provides a constant power regulation system for a duplex axial plunger pump.
The constant power regulation system is a constant power regulation system in a regulator on a plunger pump. The structure of the constant power regulation system is shown in Fig. 3. The main valve body 001 mainly includes a spring force compensation mechanism 7 and a hydraulic pressure compensation mechanism 8, wherein, the spring force compensation mechanism 7 mainly comprises an inner spring adjusting screw 701, an inner spring adjusting nut 702, an outer spring adjusting screw 703, an outer spring adjusting nut 704, a spring side cover 705, an outer spring 706, an inner spring converter 707, an inner spring 708, an outer spring converter 709, a spring seat 710, and seal rings, etc. The hydraulic pressure compensation mechanism 8 mainly comprises a compensation rod 801, a compensation valve spool 802, a compensation valve sleeve 803, a compensation plug 804, a compensation piston 805, and seal rings, etc.
The main valve body 001 is provided with the spring side cover 705 and a hydraulic side cover 002 on the two ends thereof, the inner spring 708 is disposed between the inner spring converter 707 and the spring seat 710, the inner spring converter 707 penetrates through the outer spring 706 and the outer spring converter 709, one end of the outer spring 706 contacts with the spring side cover 705, the other end of the outer spring 706 contacts with the outer spring converter 709, the outer spring converter 709 is fitted and contacts with the inner spring converter 707, and clearance is reserved between the inner spring converter 707 and the inner spring adjusting screw = 9 =
701/the spring seat 710.
The outer spring adjusting screw 703 is mounted on the main valve body 001 via the spring side cover 705, and is fixed via a threaded connection with the outer spring adjusting nut 704; the inner spring adjusting screw 701 is in a shape of a stepped shaft and includes a shaft shoulder, one end of the inner spring adjusting screw 701 penetrates through the outer spring adjusting screw 703, the inner spring converter 707, and the inner spring 708, the other end of the inner spring adjusting screw 701 is fixed via a threaded connection with the inner spring adjusting nut 702, clearance is reserved between the shaft shoulder of the inner spring adjusting screw 701 and the inner spring converter 707/the outer spring adjusting screw 703, the pre-tightening forces of the outer spring and the inner spring are adjusted by adjusting the penetration depths of the outer spring screw and the inner spring screw in the main valve body.
Wherein, the inner spring converter is in a shape of a cylinder, which, as shown in Figs. 7a and 7b, includes a cavity and an assembly hole communicating with the cavity, the inner spring is arranged on the left contact base for inner spring 7073 on the left side in the cavity, and one end of the inner spring adjusting screw 701 penetrates through the assembly hole 7072 in the inner spring converter and then is disposed in the inner spring 708.
The outer spring converter 709 is a circular ring with a stepped hole, as shown in Figs. 8a and 8b, a flange 7074 extending outwardly is arranged at the edge of one end of the cylinder, and the flange 7074 is located in the stepped hole 7093 when the outer spring converter 709 is fitted and contacts with the inner spring converter 707. The outer spring converter is fitted with the inner spring converter more closely and the fitting accuracy is higher by virtue of the contact fitting between the flange and the stepped hole.
=
As shown in Figs. 6a and 6b, the spring holder 710 is arranged with a conical groove 7104 on one side and a boss 7101 on the other side, a groove 7105 for accommodating the flange 7074 is arranged around the outer side of the boss 7101, and the boss 7101 is embedded in the inner spring 708. The structure of the compensation rod 801 is shown in Fig. 4. The compensation rod 801 comprises a conical arc head 8011, an annular groove 8012, and a tail base of compensation rod 8013, the conical arc head 8011 at the left end of the compensation rod is fitted in the conical groove 7104, the annular groove 8012 is connected with the valve spool of the servo valve 10 in a valve-controlled cylinder position servo system, the tail base of compensation rod 8013 at the right end is subjected to the acting force of an arc head of compensation valve spool 8021 at the left end of the compensation valve spool 802.
As shown in Figs. 6a and 6b, the spring seat 710 is subjected to the force of two springs at the left end, wherein, the boss 7101 is fitted with an inner circle of the inner spring 708, a right contact base for inner spring 7102 is fitted and contacts with the right end surface of the inner spring to support the inner spring 708, a parallel compressing surface 7103 is fitted and contacts with a parallel compression surface 7092 of the outer spring converter 709, and the conical groove 7104 is fitted and contacts with the conical arc head 8011 of the compensation rod;
The inner spring 708, outer spring 706, inner spring converter 707, and outer spring converter 709 constitute a series-parallel converter. The distance between the limit end surface 7071 of the inner spring converter 707 and the shaft shoulder of the inner spring adjusting screw 701 determines the pressure range in which the inner spring 708 and the outer spring 706 are in a serial operating state, the assembly hole 7072 is fitted with the inner spring adjusting screw 701, the left contact base for inner spring 7073 contacts with the left end surface of the inner spring, and the flange 7074 is fitted and contacts with the stepped hole 7093;
= 11 =
The right contact base for outer spring 7091 of the outer spring converter 709 contacts with the right end surface of the outer spring 706, the parallel compression surface 7092 can be fitted and contact with the parallel compressing surface 7103, and the stepped hole 7093 is fitted with the flange 7074;
The compensation valve spool 802 has a stepped annular structure as shown in Fig. 5, and is disposed in the compensation valve sleeve 803. The arc head of compensation valve spool 8021 at the left end contacts with the tail base of compensation rod 8013, the annular acting surface of this pump 8022 and the annular acting surface of other pump 8023 in the middle are subjected from outlet pressures Pi and P2 of front pump 3 and rear pump 2 of the duplex axial plunger pump respectively, the tail base of compensation valve spool 8024 at the right end is subjected to the acting force of the compensation piston 805, the compensation piston 805 is located in the compensation valve sleeve 803 through the sleeve compensation plug 804, and the compensation valve sleeve 803 is disposed in the main valve body 001, wherein, the left end of the compensation piston 805 communicates with the low-pressure oil in the oil tank, and the hydraulic pressure at the right end comes from the solenoid proportional pressure reducing valve outlet pressure Pf of the solenoid proportional pressure reducing valve 9 on the plunger pump.
On the basis of a conventional constant power regulation system, the constant power regulation system provided in this embodiment is designed with a novel spring assembling mechanism, namely a series-parallel converter (including an inner spring converter and an outer spring converter), so that the two springs show four types of spring stiffness characteristics in the compression process by virtue of the series-parallel converter, and the degree of fitting of the characteristic curve of the four overall stiffness coefficients to a theoretical constant power hyperbolic curve is higher in the constant power regulation process; utilizing the mechanism, the =12=
energy efficiency of the plunger pump can be greatly improved when the plunger pump works within a pressure load range of 15-25 MPa; the overload state of the plunger pump and a prime engine is effectively avoided, thereby prolonging the service life of hardware.
Embodiment 2:
This embodiment provides a regulator used on a duplex axial plunger pump. The regulator comprises the constant power regulation system for a duplex axial plunger pump described in the embodiment 1 (comprising a spring force compensation mechanism 7 and a hydraulic pressure compensation mechanism 8), a negative flow feedback regulation system (comprising a negative flow feedback oil cylinder 6), and a set of valve-controlled cylinder position servo system (mainly comprising a differential cylinder 5, a servo valve 10, a feedback rod 11, and a servo plunger 12). The negative flow feedback oil cylinder 6 is connected with the servo valve 10 in the valve-controlled cylinder position servo system to control the movement of the valve spool of the servo valve 10, the constant power regulation system is connected with the servo valve 10 in the valve-controlled cylinder position servo system via the compensation rod 801 of the hydraulic pressure compensation mechanism 8 to control the movement of the valve spool of the servo valve 10 by means of the movement of the compensation rod, the servo plunger 12 is disposed in the differential cylinder 5 and connected with the servo valve 10 via the feedback rod 11 to control the movement of the valve spool of the servo valve 10 via the feedback rod 11;
there is no connection relationship between the constant power regulation system and the negative flow feedback system; in addition, the constant power regulation system and the negative flow feedback system are controlled in an appropriate manner so that only one of them operates.
= 13 =
Embodiment 3:
This embodiment provides a duplex axial plunger pump that has the structure shown in Fig. 2.
The duplex axial plunger pump comprises a pilot pump 1, main pumps (a front pump 3 and a rear pump 2), a solenoid proportional pressure reducing valve 9, and regulators as described in the embodiment 2 mounted on the front pump 3 and rear pump 2 respectively.
In an actual hydraulic power system, the duplex axial plunger pump is usually connected with a prime engine, which, in this embodiment, is a diesel engine. The prime engine 4 drives the two axial plunger pumps (rear pump 2 and front pump 3) connected in series and the pilot pump I
mounted at the tail portion via the input shafts, wherein, the plunger pumps provide high-pressure power oil to operating actuator elements, and the pilot gear pump provides high-pressure oil to a control oil circuit. The front pump 3 and the rear pump
2 are equipped with a regulator 1 and a regulator 2 as described in the embodiment 2 respectively.
The solenoid proportional pressure reducing valve 9 provides different solenoid proportional pressure reducing valve outlet pressure Pf that varies with the input current i, so that the operating power Wc of the plunger pump can be set. To prolong the service life of the prime engine, the operating power Wc of the plunger pump should be lower than the rated power Wm of the prime engine in principle.
In actual engineering applications, when the workload pressure of the plunger pump is low and the actual output power Wo of the hydraulic pump has not reached the preset operating power Wc, the plunger pump outputs with maximum pump discharge, to meet the requirement for "light-load high-speed operation". As the load pressure is increased and the actual output power Wo of the hydraulic pump reaches the preset operating power Wc, the plunger pump regulator = 14 =
will decrease the output flow of the plunger pump through the action of the constant power regulation system if the load pressure is increased continuously, and thereby avoids overload of the prime engine 4 and realizes a self-protecting operating mode of "heavy-load low-speed operation".
The constant power regulation system utilizes the load pressures P1 and P2 of the front pump 3 and rear pump 2 as control signals to regulate the output discharges of the plunger pumps. Such a control approach is referred to as a cross power control strategy, and has an advantage of maintaining constant total output power of the entire hydraulic pump and enabling one of the pumps to utilize the remaining power automatically when the required power of the other pump is decreased, so as to take full advantage of the power of the prime engine 4.
The purpose of constant power control is to ensure that a good matching relationship is established between the operating power of the plunger pumps and the output power of the prime engine 4 when the plunger pumps are in working process by regulating the discharges of the plunger pumps to take full advantage of the power source, while ensuring that the output power of the prime engine 4 does not exceed the rated power and prolonging the service life of the electromechanical and hydraulic systems.
Embodiment 4:
An operating method of the duplex axial plunger pump as described in the embodiment 3, comprising the following steps:
a) When the operating pressure of the plunger pump is increased gradually from zero load and has not reached the preset operating power Wc of the plunger pump yet, the outlet pressures Pi and P2 of the front pump 3 and rear pump 2 increase accordingly and the force suffered by - 15=
the acting surface of this pump 8022 and acting surface of other pump 8023 of the compensation valve spool increases gradually, but the leftward acting force generated by the compensation valve spool 802 is still lower than the rightward pre-tightening force applied by the inner spring 708 and outer spring 706; thus, the compensation rod 801 has no displacement, the servo valve 10 and servo plunger 12 do not make any movement, and the plunger pump still outputs with maximum pump discharge. The constant power regulation characteristic curve corresponds to the segment AB of the Curve (2) in Fig. 1.
b) As the operating pressure of the plunger pump is increased continuously and reaches the preset operating power Wc of the plunger pump, the outlet pressures P1 and P2 of the front pump 3 and rear pump 2 increase accordingly, and the force suffered by the acting surface of this pump 8022 and acting surface of other pump 8023 increase gradually; at that point, the leftward acting force generated by the compensation valve spool 802 overcomes the rightward pre-tightening force of the inner spring 708 and outer spring 706, the compensation rod 801 moves leftwards by a displacement xR, the valve-controlled cylinder position servo system makes the big cavity end of the servo plunger 12 open to the high-pressure oil via the servo valve 10, the servo plunger 12 moves rightwards by a displacement Li = XR (ji is an amplification coefficient of displacement, which depends on the internal lever mechanism, and is constant for a specific model of plunger pump), and thereby the inclination angle of the swash plate of the plunger pump is decreased and the displacement V of the plunger pump is decreased. The constant power regulation characteristic curve corresponds to the segment BC
of the Curve (2) in Fig. 1.
In that operating state, the right end of the inner spring 708 and the right contact base for inner spring 7102 have interaction force therebetween, the left end of the inner spring 708 and the = 16 =
left contact base for inner spring 7073 have interaction force therebetween, the flange 7074 and the stepped hole 7093 have interaction force therebetween, the right contact base for outer spring 7091 and the right end of the outer spring 706 have interaction force therebetween, the left end of the outer spring 706 and the outer spring adjusting screw 703 have interaction force therebetween, and in this state, the two springs are moved and compressed simultaneously, and the two springs are connected in serials. At that point, the series-parallel converter is in an operating state that the inner spring 708 and the outer spring 706 are connected in series, and shows an overall stiffness coefficient ko equal to (k1 is the stiffness coefficient of the inner spring, and k2 is the stiffness coefficient of the outer spring).
When the compensation rod 801 moves leftwards, the inner spring 706 and outer spring 708 are compressed, and the inner spring converter 707 and outer spring converter 709 also move leftwards.
c) As the operating pressure of the plunger pump is increased continuously, the compensation rod 801 moves leftwards continuously, till the inner spring converter 707 comes into contact with the inner spring adjusting screw 701 and the serial connection operating state ends; at that point, the constant power regulation characteristic curve corresponds to the point C of the Curve (2) in Fig. 1.
d) As the operating pressure of the plunger pump is increased continuously, the compensation rod 801 moves leftwards continuously; since the inner spring converter 707 contacts with the inner spring adjusting screw 701, the outer spring 706 stops compressing, only the inner spring 708 is compressed continuously; at that point, the series-parallel converter is in an operating state that only one spring is compressed, and shows an overall stiffness coefficient = 17 =
1(0 equal to 1(1. The constant power regulation characteristic curve corresponds to the segment CD of the Curve (2) in Fig. 1.
e) As the operating pressure of the plunger pump is increased continuously, the compensation rod 801 moves leftwards continuously; when the parallel compressing surface 7103 comes into contact with the parallel compression surface 7092, the flange 7074 is disengaged from the stepped hole 7093 and does not contact with the stepped hole 7093 anymore, the outer spring converter 709 also moves leftwards, the spring seat 710 compresses the inner spring 708 and outer spring 706 simultaneously, and the series-parallel converter is in an operating state that the inner spring 708 and outer spring 706 are connected in parallel. The constant power regulation characteristic curve corresponds to the segment DE of the Curve (2) in Fig.
1.
f) If the operating pressure of the plunger pump is decreased, the outlet pressures Pi and P2 of the front pump 3 and rear pump 2 will decrease accordingly; in that case, the regulating principle is similar, but the regulating process is contrary to the regulating process in the case that the operating pressure of the plunger pump is increased.
The outer spring 706 is fitted with the outer spring adjusting screw 703, and the pre-tightening force of the series-parallel converter can be changed by turning the outer spring adjusting nut 704; the inner spring converter 707 is fitted with the inner spring adjusting screw 701, and the spacing between the inner spring adjusting screw 701 and the inner spring converter 707 can be changed by turning the inner spring adjusting nut 702, and thereby the load pressure range of the series-parallel converter in the serial operation state can be adjusted; the structural dimension design of the spring seat 710 determines the distance between the outer spring converter 709 and the spring seat 710 (i.e., the spacing between the parallel compressing surface 7103 and the = 18 =
parallel compression surface 7092), which is one of important dimensions that determine the pressure range of the series-parallel converter in a parallel operating state.
A mathematic model of the duplex axial plunger pump can be established, and a functional block diagram of the constant power regulation mechanism can be plotted according to the working principle of the variable displacement mechanism, as shown in Fig. 13.
Wherein, (I) output characteristic of the solenoid proportional pressure reducing valve 9:
-K
Pf - outlet pressure of solenoid proportional pressure reducing valve 9;
KB - input current-output pressure gain factor of solenoid proportional pressure reducing valve; the value may be deemed as a fixed value once the hardware model of the solenoid proportional pressure reducing valve 9 is determined;
i - input current of solenoid proportional pressure reducing valve 9;
(II) force equation of the constant power regulation system:
k. k.
PfAi + PA1 + P,A, = kexR+
k2 + k r Af area of the compensation piston 805 where the outlet pressure Pf of the solenoid proportional pressure reducing valve is applied;
A1 - area of the compensation valve spool 802 where the load pressure P1 of the front pump
The solenoid proportional pressure reducing valve 9 provides different solenoid proportional pressure reducing valve outlet pressure Pf that varies with the input current i, so that the operating power Wc of the plunger pump can be set. To prolong the service life of the prime engine, the operating power Wc of the plunger pump should be lower than the rated power Wm of the prime engine in principle.
In actual engineering applications, when the workload pressure of the plunger pump is low and the actual output power Wo of the hydraulic pump has not reached the preset operating power Wc, the plunger pump outputs with maximum pump discharge, to meet the requirement for "light-load high-speed operation". As the load pressure is increased and the actual output power Wo of the hydraulic pump reaches the preset operating power Wc, the plunger pump regulator = 14 =
will decrease the output flow of the plunger pump through the action of the constant power regulation system if the load pressure is increased continuously, and thereby avoids overload of the prime engine 4 and realizes a self-protecting operating mode of "heavy-load low-speed operation".
The constant power regulation system utilizes the load pressures P1 and P2 of the front pump 3 and rear pump 2 as control signals to regulate the output discharges of the plunger pumps. Such a control approach is referred to as a cross power control strategy, and has an advantage of maintaining constant total output power of the entire hydraulic pump and enabling one of the pumps to utilize the remaining power automatically when the required power of the other pump is decreased, so as to take full advantage of the power of the prime engine 4.
The purpose of constant power control is to ensure that a good matching relationship is established between the operating power of the plunger pumps and the output power of the prime engine 4 when the plunger pumps are in working process by regulating the discharges of the plunger pumps to take full advantage of the power source, while ensuring that the output power of the prime engine 4 does not exceed the rated power and prolonging the service life of the electromechanical and hydraulic systems.
Embodiment 4:
An operating method of the duplex axial plunger pump as described in the embodiment 3, comprising the following steps:
a) When the operating pressure of the plunger pump is increased gradually from zero load and has not reached the preset operating power Wc of the plunger pump yet, the outlet pressures Pi and P2 of the front pump 3 and rear pump 2 increase accordingly and the force suffered by - 15=
the acting surface of this pump 8022 and acting surface of other pump 8023 of the compensation valve spool increases gradually, but the leftward acting force generated by the compensation valve spool 802 is still lower than the rightward pre-tightening force applied by the inner spring 708 and outer spring 706; thus, the compensation rod 801 has no displacement, the servo valve 10 and servo plunger 12 do not make any movement, and the plunger pump still outputs with maximum pump discharge. The constant power regulation characteristic curve corresponds to the segment AB of the Curve (2) in Fig. 1.
b) As the operating pressure of the plunger pump is increased continuously and reaches the preset operating power Wc of the plunger pump, the outlet pressures P1 and P2 of the front pump 3 and rear pump 2 increase accordingly, and the force suffered by the acting surface of this pump 8022 and acting surface of other pump 8023 increase gradually; at that point, the leftward acting force generated by the compensation valve spool 802 overcomes the rightward pre-tightening force of the inner spring 708 and outer spring 706, the compensation rod 801 moves leftwards by a displacement xR, the valve-controlled cylinder position servo system makes the big cavity end of the servo plunger 12 open to the high-pressure oil via the servo valve 10, the servo plunger 12 moves rightwards by a displacement Li = XR (ji is an amplification coefficient of displacement, which depends on the internal lever mechanism, and is constant for a specific model of plunger pump), and thereby the inclination angle of the swash plate of the plunger pump is decreased and the displacement V of the plunger pump is decreased. The constant power regulation characteristic curve corresponds to the segment BC
of the Curve (2) in Fig. 1.
In that operating state, the right end of the inner spring 708 and the right contact base for inner spring 7102 have interaction force therebetween, the left end of the inner spring 708 and the = 16 =
left contact base for inner spring 7073 have interaction force therebetween, the flange 7074 and the stepped hole 7093 have interaction force therebetween, the right contact base for outer spring 7091 and the right end of the outer spring 706 have interaction force therebetween, the left end of the outer spring 706 and the outer spring adjusting screw 703 have interaction force therebetween, and in this state, the two springs are moved and compressed simultaneously, and the two springs are connected in serials. At that point, the series-parallel converter is in an operating state that the inner spring 708 and the outer spring 706 are connected in series, and shows an overall stiffness coefficient ko equal to (k1 is the stiffness coefficient of the inner spring, and k2 is the stiffness coefficient of the outer spring).
When the compensation rod 801 moves leftwards, the inner spring 706 and outer spring 708 are compressed, and the inner spring converter 707 and outer spring converter 709 also move leftwards.
c) As the operating pressure of the plunger pump is increased continuously, the compensation rod 801 moves leftwards continuously, till the inner spring converter 707 comes into contact with the inner spring adjusting screw 701 and the serial connection operating state ends; at that point, the constant power regulation characteristic curve corresponds to the point C of the Curve (2) in Fig. 1.
d) As the operating pressure of the plunger pump is increased continuously, the compensation rod 801 moves leftwards continuously; since the inner spring converter 707 contacts with the inner spring adjusting screw 701, the outer spring 706 stops compressing, only the inner spring 708 is compressed continuously; at that point, the series-parallel converter is in an operating state that only one spring is compressed, and shows an overall stiffness coefficient = 17 =
1(0 equal to 1(1. The constant power regulation characteristic curve corresponds to the segment CD of the Curve (2) in Fig. 1.
e) As the operating pressure of the plunger pump is increased continuously, the compensation rod 801 moves leftwards continuously; when the parallel compressing surface 7103 comes into contact with the parallel compression surface 7092, the flange 7074 is disengaged from the stepped hole 7093 and does not contact with the stepped hole 7093 anymore, the outer spring converter 709 also moves leftwards, the spring seat 710 compresses the inner spring 708 and outer spring 706 simultaneously, and the series-parallel converter is in an operating state that the inner spring 708 and outer spring 706 are connected in parallel. The constant power regulation characteristic curve corresponds to the segment DE of the Curve (2) in Fig.
1.
f) If the operating pressure of the plunger pump is decreased, the outlet pressures Pi and P2 of the front pump 3 and rear pump 2 will decrease accordingly; in that case, the regulating principle is similar, but the regulating process is contrary to the regulating process in the case that the operating pressure of the plunger pump is increased.
The outer spring 706 is fitted with the outer spring adjusting screw 703, and the pre-tightening force of the series-parallel converter can be changed by turning the outer spring adjusting nut 704; the inner spring converter 707 is fitted with the inner spring adjusting screw 701, and the spacing between the inner spring adjusting screw 701 and the inner spring converter 707 can be changed by turning the inner spring adjusting nut 702, and thereby the load pressure range of the series-parallel converter in the serial operation state can be adjusted; the structural dimension design of the spring seat 710 determines the distance between the outer spring converter 709 and the spring seat 710 (i.e., the spacing between the parallel compressing surface 7103 and the = 18 =
parallel compression surface 7092), which is one of important dimensions that determine the pressure range of the series-parallel converter in a parallel operating state.
A mathematic model of the duplex axial plunger pump can be established, and a functional block diagram of the constant power regulation mechanism can be plotted according to the working principle of the variable displacement mechanism, as shown in Fig. 13.
Wherein, (I) output characteristic of the solenoid proportional pressure reducing valve 9:
-K
Pf - outlet pressure of solenoid proportional pressure reducing valve 9;
KB - input current-output pressure gain factor of solenoid proportional pressure reducing valve; the value may be deemed as a fixed value once the hardware model of the solenoid proportional pressure reducing valve 9 is determined;
i - input current of solenoid proportional pressure reducing valve 9;
(II) force equation of the constant power regulation system:
k. k.
PfAi + PA1 + P,A, = kexR+
k2 + k r Af area of the compensation piston 805 where the outlet pressure Pf of the solenoid proportional pressure reducing valve is applied;
A1 - area of the compensation valve spool 802 where the load pressure P1 of the front pump
3 is applied;
= 19 =
A2 - area of the compensation valve spool 802 where the load pressure P2 of the rear pump 2 is applied;
Ko - overall stiffness coefficient of the series-parallel converter;
XR- leftward displacement of the compensation rod 801;
k1 - stiffness coefficient of inner spring 708;
k2 - stiffness coefficient of outer spring 706;
xp - spring pre-tension length in the series-parallel converter;
(III) displacement transfer relationship in the valve-controlled cylinder position servo system:
xx max ¨ tilcR
xsi, - displacement of servo plunger 12;
xõ,õ, - maximum displacement of servo plunger 12, when xsF=xmax, the displacement of the plunger pump is maximum; the specific value is determined by the structural dimensions of the plunger pump and is fixed;
1.t - displacement amplification coefficient of the position servo system, determined by the internal lever mechanism, and is fixed for a specific model of plunger pump;
(IV) flow output formula of the duplex plunger pump:
Q=2 TinsitsF
Q - total output flow of the front pump 3 and rear pump 2 in the duplex plunger pump;
= 20 =
KJ' - displacement gradient coefficient of the plunger pump; the specific value is determined by the structural dimensions of the plunger pump and is fixed;
n - rotation speed of the input shaft of the plunger pump;
The following formula can be obtained from the above relational expressions:
KBrelf + P1A + P2 A: ¨ x kõ -P
Q=2-Kf1r(xõ.., ) ko Suppose the load pressures Pi and P2 on the front pump 3 and rear pump 2 are equal to each other, i.e., PI=P2=P0, the value n is fixed when the input current i of the solenoid proportional pressure reducing valve 9 is fixed and the prime engine 4 drives the plunger pump at a fixed rotation speed, and the relationship between the total output flow Q of the plunger pump and the load pressure Po is as follows:
2.1(ri-4(A, +A) k, P K 3i.A
k ____________________________ Po + IK/1141 + 4300 o ko It is seen from the above formula: in the characteristic curve of pressure load Po vs. output flow Q of the plunger pump, the slope of the line is a negative reciprocal of the overall stiffness coefficient.
Analyzed according to the four operating states of the series-parallel mechanism, the overall stiffness coefficient Ko of the springs is as follows:
= ,1 =
co kik 2 k k, + k2, o =
2 k2 In a constant power regulation system for a duplex axial plunger pump that has series-parallel spring converters, the constant power regulation characteristic curve comprises four straight lines.
Through accurate calculation and selection, the start acting positions and slopes of the four lines can be controlled, and the curve is smoother than an existing constant power regulation curve formed by three straight lines and is closer to the theoretical constant power hyperbolic curve (see the Curves (2) and (1) in Fig. 1); thus, the degree of fitting of the constant power regulation curve to the theoretical constant power hyperbolic curve is greatly improved, so that the power matching between the plunger pump and the prime engine is more reasonable, and the power can be taken full advantage of = 22 =
= 19 =
A2 - area of the compensation valve spool 802 where the load pressure P2 of the rear pump 2 is applied;
Ko - overall stiffness coefficient of the series-parallel converter;
XR- leftward displacement of the compensation rod 801;
k1 - stiffness coefficient of inner spring 708;
k2 - stiffness coefficient of outer spring 706;
xp - spring pre-tension length in the series-parallel converter;
(III) displacement transfer relationship in the valve-controlled cylinder position servo system:
xx max ¨ tilcR
xsi, - displacement of servo plunger 12;
xõ,õ, - maximum displacement of servo plunger 12, when xsF=xmax, the displacement of the plunger pump is maximum; the specific value is determined by the structural dimensions of the plunger pump and is fixed;
1.t - displacement amplification coefficient of the position servo system, determined by the internal lever mechanism, and is fixed for a specific model of plunger pump;
(IV) flow output formula of the duplex plunger pump:
Q=2 TinsitsF
Q - total output flow of the front pump 3 and rear pump 2 in the duplex plunger pump;
= 20 =
KJ' - displacement gradient coefficient of the plunger pump; the specific value is determined by the structural dimensions of the plunger pump and is fixed;
n - rotation speed of the input shaft of the plunger pump;
The following formula can be obtained from the above relational expressions:
KBrelf + P1A + P2 A: ¨ x kõ -P
Q=2-Kf1r(xõ.., ) ko Suppose the load pressures Pi and P2 on the front pump 3 and rear pump 2 are equal to each other, i.e., PI=P2=P0, the value n is fixed when the input current i of the solenoid proportional pressure reducing valve 9 is fixed and the prime engine 4 drives the plunger pump at a fixed rotation speed, and the relationship between the total output flow Q of the plunger pump and the load pressure Po is as follows:
2.1(ri-4(A, +A) k, P K 3i.A
k ____________________________ Po + IK/1141 + 4300 o ko It is seen from the above formula: in the characteristic curve of pressure load Po vs. output flow Q of the plunger pump, the slope of the line is a negative reciprocal of the overall stiffness coefficient.
Analyzed according to the four operating states of the series-parallel mechanism, the overall stiffness coefficient Ko of the springs is as follows:
= ,1 =
co kik 2 k k, + k2, o =
2 k2 In a constant power regulation system for a duplex axial plunger pump that has series-parallel spring converters, the constant power regulation characteristic curve comprises four straight lines.
Through accurate calculation and selection, the start acting positions and slopes of the four lines can be controlled, and the curve is smoother than an existing constant power regulation curve formed by three straight lines and is closer to the theoretical constant power hyperbolic curve (see the Curves (2) and (1) in Fig. 1); thus, the degree of fitting of the constant power regulation curve to the theoretical constant power hyperbolic curve is greatly improved, so that the power matching between the plunger pump and the prime engine is more reasonable, and the power can be taken full advantage of = 22 =
Claims (7)
1. A constant power regulation system for a duplex axial plunger pump comprising a valve body; an outer spring adjusting screw on the valve body; an inner spring adjusting screw, an outer spring adjusting nut and an inner spring adjusting nut, wherein the valve body contains an outer spring, an inner spring, a compensation rod, a compensation valve spool and a compensation piston; an hydraulic side cover on one end of the valve body; a spring side cover on a second end of the valve body, the outer spring adjusting screw being held on the valve body by the spring side cover and fixed in position by the outer spring adjusting nut, the inner spring adjusting screw extending through the outer spring adjusting screw and being fixed in position by the inner spring adjusting nut;
an inner spring converter in the valve body; an outer spring converter in the valve body; a spring seat in the valve body, the inner spring being located between the inner spring converter and the spring seat, the inner spring converter extending through the outer spring and the outer spring converter, one end of the outer spring contacting the outer spring adjusting screw, a second end of the outer spring contacting the outer spring converter, the outer spring converter contacting the inner spring converter, and wherein there is clearance between the inner spring converter and the inner spring adjusting screw and the spring seat.
an inner spring converter in the valve body; an outer spring converter in the valve body; a spring seat in the valve body, the inner spring being located between the inner spring converter and the spring seat, the inner spring converter extending through the outer spring and the outer spring converter, one end of the outer spring contacting the outer spring adjusting screw, a second end of the outer spring contacting the outer spring converter, the outer spring converter contacting the inner spring converter, and wherein there is clearance between the inner spring converter and the inner spring adjusting screw and the spring seat.
2. The constant power regulation system of claim 1, wherein the inner spring converter is cylindrical and includes a cavity containing the inner spring, one end of the inner spring adjusting screw extending through one end of the inner spring converter into the inner spring.
3. The constant power regulation system of claim 2, wherein the outer spring converter is a ring with a stepped hole, and the inner spring converter includes a flange extending outwardly at one end into the stepped hole when the outer spring converter contacts the inner spring converter.
4. The constant power regulation system of claim 3, including a conical groove in one side of the spring seat containing one end of the compensation rod, a boss on a second side extending into the inner spring, and a groove in the second side extending around an outer side of the boss for accommodating the flange on the inner spring converter.
5. A regulator comprising the constant power regulation system according to any one of claims 1 to 4, a negative flow feedback regulation system including a negative flow feedback oil cylinder, and a valve controlled cylinder position servo system including a servo valve, a feedback rod, a servo plunger and a differential cylinder; the compensation rod and the negative flow feedback oil cylinder being connected to the servo valve and adapted to control movement of the valve spool of the servo valve; and the servo plunger being located in the differential cylinder and connected to the servo valve via the feedback rod, and adapted to control the movement of the valve spool of the servo valve via the feedback rod.
6. A duplex axial plunger pump including the regulator according to claim 5.
7. A method of operating the duplex axial plunger pump of claim 6 comprising the steps of:
when the operating pressure of the plunger pump is increased gradually from zero load and is still below a preset operating power of the plunger pump, the outlet pressure of the plunger pump increases accordingly and the force acting on the compensation valve spool increases gradually, but the force generated by the compensation valve spool is still lower than the pre-tightening force applied by the inner spring and the outer spring; in that state, the compensation rod has no displacement, the servo valve and the servo plunger are not stationery, and the plunger pump still outputs maximum pump discharge;
as the operating pressure of the plunger pump is increased continuously and reaches a preset operating power, the outlet pressure of the plunger pump increases accordingly, and the force ac ting on the compensation spool increases gradually; the force generated by the compensation valve spool overcomes the pre-tightening force of the inner spring and outer spring, the compensation rod is displaced towards the inner and outer springs, pushing the inner spring converter towards the inner and outer springs, and driving the servo valve as it moves toward the springs; under the action of the servo valve, a big cavity end of the servo plunger is open to the high-pressure oil, the servo plunger is moved away from the servo valve, thereby the inclination angle of the swash plate of the plunger pump is decreased and the displacement of the plunger pump is decreased;
as the operating pressure of the plunger pump is increased continuously, the compensation rod moves continuously towards the servo valve until the inner spring converter comes in contact with the inner spring adjusting screw;
as the operating pressure of the plunger pump continuously increases, the compensation rod moves continuously towards the outer and inner springs; when the spring seat contacts the outer spring converter, the flange is gradually disengaged from the stepped hole, the outer spring converter moves separately towards the outer and inner springs, and the spring seat compresses the inner spring and the outer spring simultaneously; and when the operating pressure of the plunger pump decreases, the outlet pressure of the plunger pump decreases accordingly, and the regulation process is opposite to the regulation process when the operating pressure of the plunger pump is increased.
when the operating pressure of the plunger pump is increased gradually from zero load and is still below a preset operating power of the plunger pump, the outlet pressure of the plunger pump increases accordingly and the force acting on the compensation valve spool increases gradually, but the force generated by the compensation valve spool is still lower than the pre-tightening force applied by the inner spring and the outer spring; in that state, the compensation rod has no displacement, the servo valve and the servo plunger are not stationery, and the plunger pump still outputs maximum pump discharge;
as the operating pressure of the plunger pump is increased continuously and reaches a preset operating power, the outlet pressure of the plunger pump increases accordingly, and the force ac ting on the compensation spool increases gradually; the force generated by the compensation valve spool overcomes the pre-tightening force of the inner spring and outer spring, the compensation rod is displaced towards the inner and outer springs, pushing the inner spring converter towards the inner and outer springs, and driving the servo valve as it moves toward the springs; under the action of the servo valve, a big cavity end of the servo plunger is open to the high-pressure oil, the servo plunger is moved away from the servo valve, thereby the inclination angle of the swash plate of the plunger pump is decreased and the displacement of the plunger pump is decreased;
as the operating pressure of the plunger pump is increased continuously, the compensation rod moves continuously towards the servo valve until the inner spring converter comes in contact with the inner spring adjusting screw;
as the operating pressure of the plunger pump continuously increases, the compensation rod moves continuously towards the outer and inner springs; when the spring seat contacts the outer spring converter, the flange is gradually disengaged from the stepped hole, the outer spring converter moves separately towards the outer and inner springs, and the spring seat compresses the inner spring and the outer spring simultaneously; and when the operating pressure of the plunger pump decreases, the outlet pressure of the plunger pump decreases accordingly, and the regulation process is opposite to the regulation process when the operating pressure of the plunger pump is increased.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510689791.8 | 2015-10-21 | ||
| CN201510689791.8A CN105179221B (en) | 2015-10-21 | 2015-10-21 | Constant power adjusting system for duplex axial plunger pump and application of constant power adjusting system |
| PCT/CN2016/084716 WO2017067177A1 (en) | 2015-10-21 | 2016-06-03 | Constant power regulation system for duplex axial plunger pump and applications thereof |
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| CA2974845A1 CA2974845A1 (en) | 2017-04-27 |
| CA2974845C true CA2974845C (en) | 2019-02-12 |
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| CN (1) | CN105179221B (en) |
| AU (1) | AU2016343379B2 (en) |
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| CN105179221B (en) * | 2015-10-21 | 2017-01-11 | 山东科技大学 | Constant power adjusting system for duplex axial plunger pump and application of constant power adjusting system |
| CN105649964A (en) * | 2015-12-28 | 2016-06-08 | 山东科技大学 | Constant-power adjusting system for spiral serial-parallel convertible duplex axial plunger pump |
| CN106194439A (en) * | 2016-08-31 | 2016-12-07 | 南京威孚金宁有限公司 | A kind of VE type dispensing pump and speed regulator thereof and a kind of VE type dispensing pump dual spring negative correction mechanism |
| CN106351995B (en) * | 2016-11-16 | 2018-07-24 | 西安航空动力控制科技有限公司 | A kind of hyperbolic change spring rate mechanism |
| CN109967330B (en) * | 2018-12-27 | 2023-11-28 | 无锡市宇超电子有限公司 | Ultrasonic transduction device |
| CN110219789B (en) * | 2019-05-28 | 2023-06-20 | 龙工（上海）精工液压有限公司 | Hydraulic pump power shear mechanism |
| CN114135458A (en) * | 2021-11-30 | 2022-03-04 | 力源液压（苏州）有限公司 | Constant power control structure of plunger pump |
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| SU1483092A1 (en) * | 1987-02-04 | 1989-05-30 | Одесское производственное объединение по производству гидрооборудования и гидроавтоматики для строительных и дорожных машин | Power controller for multiflow pump |
| JPH0874743A (en) * | 1994-09-05 | 1996-03-19 | Nippon Sharyo Seizo Kaisha Ltd | Control circuit for variable displacement pump |
| JPH11218102A (en) * | 1997-11-11 | 1999-08-10 | Komatsu Ltd | Pressurized oil supply device |
| US6109030A (en) * | 1998-02-13 | 2000-08-29 | Sauer Inc. | Apparatus and method for ganging multiple open circuit pumps |
| CN2720158Y (en) * | 2004-08-11 | 2005-08-24 | 徐绳武 | Constant power and constant pressure variable pump |
| CN101922445B (en) * | 2010-07-29 | 2013-08-21 | 杭州力龙液压有限公司 | Constant power control valve |
| CN102410166B (en) * | 2011-10-13 | 2014-10-15 | 杭州力龙液压有限公司 | Variable-displacement pump control device, constant-power variable-displacement pump and engineering machine |
| CN203867846U (en) * | 2014-01-02 | 2014-10-08 | 江苏恒立液压有限公司 | Hydraulic plunger pump power control device |
| CN105179221B (en) * | 2015-10-21 | 2017-01-11 | 山东科技大学 | Constant power adjusting system for duplex axial plunger pump and application of constant power adjusting system |
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| AU2016343379B2 (en) | 2018-12-20 |
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| WO2017067177A1 (en) | 2017-04-27 |
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