DE102011015903B4 - Pump arrangement - Google Patents

Abstract

Pump arrangement with several constant pumps (P1, P2, P3) which can be driven jointly by an electric motor (40), the speed of which can be set by a frequency converter via a control circuit (34, 38), each constant pump (P1, P2, P3) having one Working line (2, 4, 6) in each of which a switching valve (10, 12, 14) is arranged, via which a delivery volume flow of the assigned constant pump (P1, P2, P3) can be discharged to a tank (T), the individual working lines (2, 4, 6) open at a common high pressure connection or in a common high pressure line (8), characterized in that the switching valves (10, 12, 14) can be switched depending on a threshold speed of the electric motor (40).

Description

The invention relates to a pump arrangement according to the preamble of claim 1 and a method for its operation.

the EP 2 060 788 A1 discloses an arrangement with a plurality of pumps for providing pressurized kyrogenic liquid, for example in an air liquefaction system.

The pamphlet EP 1 564 414 A1 shows a pump arrangement according to the preamble of claim 1, in which a hydraulic consumer is supplied or driven via two fixed displacement pumps coupled to one another and via a common variable-speed drive. When the load pressure falls below a predetermined value, one of the two pumps is deactivated or switched to ineffective via a switching valve by connecting its high-pressure connection to a tank. The switching valve is switched via a control line in which the load pressure of the hydraulic consumer is applied, so that the switching valve is a pressure switching valve.

The disadvantage of this pump arrangement is that it is provided to supply a consumer with two opposite pressure chambers.

In contrast, the invention is based on the object of creating a pump arrangement which can be used to supply several and different consumers.

This object is achieved by a pump arrangement having the features of patent claim 1 and by a method for its operation according to patent claims 8 and 9, respectively.

The pump arrangement according to the invention has several constant pumps connected in parallel, which are driven jointly by a variable-speed drive. Each fixed displacement pump has an assigned working line, in each of which a switching valve is arranged, via which a delivery volume flow of the assigned fixed displacement pump can be discharged to a tank. The working lines open out at a common high pressure connection or in a common high pressure line of the pump arrangement. According to the invention, the switching valves can be switched or actuated for deactivating or ineffective switching or for activating or switching on the associated constant pump as a function of threshold speeds of the variable-speed drive. This creates a pump arrangement that can be used with increased flexibility to supply several and different consumers.

According to the invention, the variable-speed drive is an electric motor, the speed of the electric motor being adjustable by a frequency converter via the control loop.

A speed sensor connected to the control circuit can be provided on the electric motor in closed-loop operation.

Or, according to a more cost-effective variant, an equivalent circuit diagram or speed model can be created in the frequency converter in open-loop operation (open control loop).

Further advantageous refinements of the invention are described in the dependent claims.

It is particularly preferred if the pump arrangement is a constant pressure system, in the high pressure line of which a constant working pressure can be generated and maintained even at different speeds of the variable speed drive. This is done with the control circuit, which has a pressure sensor, via which a load pressure in the common high-pressure line can be determined. The switching valves connected to it can be switched via the control circuit. Hydraulic consumers can thus be operated via the pump arrangement with constant force or torque and at variable speed.

The fixed displacement pumps can preferably be coupled to one another and / or to the electric motor via shafts with couplings. In this way, individual fixed displacement pumps can also be shut down completely.

If the fixed displacement pumps have different nominal delivery volumes, there are various possible combinations of the fixed displacement pumps, so that the speed range of the electric motor can be further restricted. The fixed displacement pump with the lowest nominal delivery volume can be designed for zero stroke operation of the consumer and / or for pressure holding operation to compensate for leaks in the pump arrangement according to the invention or the consumer it supplies.

If the switching valves are connected to the tank via a common return tank line, a cooler and / or a filter can be arranged in the tank line.

In a preferred development of the pump arrangement according to the invention, a pressure accumulator is connected to the common high-pressure line.

It is particularly preferred if an adjustable one-way flow control valve is arranged between the pressure accumulator and the high pressure line. It can act as an attenuator together with the pressure accumulator.

• - insbesondere stetiges - Erhöhen der Drehzahl des Elektromotors;
• - Aktivieren oder Zuschalten einer der Konstantpumpen über das ihr zugeordnete Schaltventil mittels der - vorzugsweise einstellbaren - Schwelldrehzahl; und
• - insbesondere stetiges - Erhöhen der Drehzahl des Elektromotors.

The method according to the invention for increasing a volume flow in the common high-pressure line of a pump arrangement according to one of the preceding claims has the following steps:

• - in particular steady - increasing the speed of the electric motor;
• - Activation or connection of one of the constant pumps via the switching valve assigned to it by means of the - preferably adjustable - threshold speed; and
• - in particular steady - increasing the speed of the electric motor.

This creates a method for operating a pump arrangement, the electric motor of which can largely be operated in a wide speed range.

• - insbesondere sprunghaftes - Absenken der Drehzahl des Elektromotors erfolgen. Damit kann der theoretisch sprunghaft steigende Volumenstrom in der Hochdruckleitung kompensiert werden.

In the middle step "Activate or connect one of the constant pumps" a

• - in particular abrupt - lowering of the speed of the electric motor take place. In this way, the theoretically sudden increase in volume flow in the high-pressure line can be compensated.

• - insbesondere stetiges - Verringern der Drehzahl des Elektromotors;
• - Deaktivieren oder Wirkungslos-Schalten einer der Konstantpumpen über das ihr zugeordnete Schaltventil mittels der - vorzugsweise einstellbaren - Schwelldrehzahl; und
• - insbesondere stetiges - Verringern der Drehzahl des Elektromotors.

Accordingly, the method according to the invention for reducing a volume flow in the common high-pressure line of a pump arrangement according to one of the preceding claims has the following steps:

• - in particular steady - reducing the speed of the electric motor;
• - Deactivation or ineffective switching of one of the constant pumps via the switching valve assigned to it by means of the - preferably adjustable - threshold speed; and
• - in particular steady - reducing the speed of the electric motor.

This creates a method for operating a pump arrangement, the electric motor of which can largely be operated in a wide speed range.

In the middle step “Deactivating or switching one of the constant pumps to ineffective”, the speed of the electric motor can be increased, especially abruptly. This allows the theoretically sudden drop in volume flow in the high-pressure line to be compensated.

With both methods, it is particularly preferred if the activation or connection of one of the constant pumps at a higher threshold speed (e.g. 1500 1 / min) and the deactivation or ineffective switching of the same constant pump at a lower threshold speed (e.g. 500 1 / min ) respectively. This results in a speed range with a wide hysteresis.

• 1 ein Ausführungsbeispiel einer erfindungsgemäßen Pumpenanordnung bei maximalem Volumenstrombedarf eines Verbrauchers; und
• 2 das Ausführungsbeispiel gemäß 1 im Nullhub- bzw. Druckhaltebetrieb.

An exemplary embodiment of the invention is described in detail below with reference to the figures. Show it:

• 1 an embodiment of a pump arrangement according to the invention with a maximum volume flow requirement of a consumer; and
• 2 the embodiment according to 1 in zero stroke or pressure holding operation.

1 shows an embodiment of a pump arrangement according to the invention, which is designed as a constant pressure system, with a maximum volume flow requirement of a consumer connected to the pump arrangement 1 . The pump arrangement has three constant pumps connected in parallel P1 , P2 , P3 . These are arranged in an open circuit and each have a working line 2 , 4th , 6th . The working lines 2 , 4th , 6th open into a common high-pressure line 8th about which the consumer 1 is supplied with pump pressure.

The three fixed displacement pumps can have different nominal delivery volumes. According to this option, a large fixed displacement pump is used below P3 , a medium fixed displacement pump P2 and a small fixed displacement pump P1 differentiated. The small fixed displacement pump P1 is designed for zero stroke or pressure holding operation.

In the working lines 2 , 4th , 6th is a switching valve each 10 , 12th , 14th arranged. Every switching valve 10 , 12th , 14th is designed as a 3/2-way valve and has two switching positions, with the in 1 The switching positions shown are the respective fixed displacement pumps P1 , P2 , P3 with the high pressure line 8th and thus with the consumer 1 connected is. In a respective second switching position of the switching valves 10 , 12th , 14th becomes the assigned fixed displacement pump P1 , P2 , P3 via a respective discharge line 16 , 18th , 20th to a tank T relieved. To this end, the relief lines flow 16 , 18th , 20th in a common connection line 21 that is in a tank line 22nd flows out. The tank line 22nd connects the consumer 1 with the tank T .

In the connecting line 21 is a spring-loaded check valve 24 arranged, the direction of opening of the relief lines 16 , 18th , 20th to the tank line 22nd and is thus directed towards the tank.

In a section of the tank line 22nd that between the consumer 1 and the confluence of the connecting line 21 is arranged is a spring-loaded check valve 26th provided, the opening direction of the consumer 1 to the tank T is directed.

In a section of the tank line 22nd between the junction of the connecting line 21 and the tank T are arranged are a filter 28 and a cooler 30th arranged. This is not only used by the consumer 1 pressure medium flowing back but also that from the pumps P1 , P2 , P3 via your discharge lines 16 , 18th , 20th to the tank T returning pressure medium filtered and cooled.

To the high pressure line 8th is via a control line 32 a pressure sensor 34 connected via a signal line 36 to a control unit 38 the pump arrangement according to the invention is connected. Every switching valve 10 , 12th , 14th is via an electrical line 54 , 56 , 58 from the control unit 38 actuated or switched. The control unit 38 further regulates the speed of an electric motor via a frequency converter (not shown in detail) 40 that has a drive shaft 42 with the large fixed displacement pump P3 connected is. The big fixed displacement pump P3 is via a connecting shaft 44 to the middle fixed displacement pump P2 coupled while this via a connecting shaft 46 to the small fixed displacement pump P1 is coupled. In the waves 42 , 44 , 46 each is a coupling 48 , 50 , 52 provided over which the machines 40 , P1 , P2 , P3 can be separated or decoupled from each other.

The fixed displacement pumps do not have to be connected via couplings; they can also be connected directly to one another and form a multiple pump.

To the high pressure line 8th is via a one-way flow control valve 60 a pressure accumulator 62 connected. The pressure accumulator 62 can pressurized medium to the high-pressure line via a comparatively large opening cross-section 8th and thus to the consumer 1 release while a filling of the accumulator 62 effective opening cross-section is comparatively small and adjustable.

If from the consumer 1 the switching valves are used 10 , 12th , 14th via the control unit 38 in the in 1 switched positions shown, so that the delivery volume flows of all three constant pumps P1 , P2 , P3 via the common high pressure line 8th to the consumer 1 be promoted.

2 shows the embodiment of the pump arrangement according to the invention according to 1 in zero stroke or pressure holding operation. Here are the two switching valves 12th , 14th the medium and the large fixed displacement pump P2 , P3 via the control unit 38 switched in such a way that their respective delivery volume flow via the respective relief line 18th , 20th and via the connection line 21 to the tank line 22nd and with it to the tank T be discharged.

• - große Konstantpumpe P3 und mittlere Konstantpumpe P2 fördern zum Verbraucher 1;
• - große Konstantpumpe P3 und kleiner Konstantpumpe P1 fördern zum Verbraucher 1;
• - mittlere Konstantpumpe P2 und kleiner Konstantpumpe P1 fördern zum Verbraucher 1;
• - nur große Konstantpumpe P3 fördert zum Verbraucher 1; und
• - nur mittlere Konstantpumpe P2 fördert zum Verbraucher 1.

In a special design of the exemplary embodiment described, the electric motor 40 at the in 1 operating status shown for all fixed displacement pumps P1 , P2 , P3 drive at a speed of 3000 1 / min while the in 2 The operating state shown is at a speed of 200 1 / min. Between the two in the 1 and 2 The following operating states (not shown) are possible:

• - large fixed displacement pump P3 and medium fixed displacement pump P2 promote to the consumer 1 ;
• - large fixed displacement pump P3 and small fixed displacement pump P1 promote to the consumer 1 ;
• - medium fixed displacement pump P2 and small fixed displacement pump P1 promote to the consumer 1 ;
• - only large fixed displacement pump P3 promotes to the consumer 1 ; and
• - only medium fixed displacement pump P2 promotes to the consumer 1 .

This means that there is a comparatively “wide” variation in the common delivery volume flow in the high-pressure line 8th and thus to the consumer 1 possible.

A second exemplary embodiment of the pump arrangement according to the invention is explained below: In the zero stroke, a 10ccm pump is sufficient to compensate for the leakage of the consumer 1 at 2 l / min at a constant pressure of 100 bar. This is the speed of the electric motor 40 at 200 rpm. The electric motor 40 a torque of 15.9 Nm is demanded by the 10ccm pump and the requirement "constant pressure with 100 bar" without taking efficiency into account.

At the maximum volume flow requirement of the consumer 1 from 90 l / min a 20 ccm pump is switched on from a speed of 1500 rpm, for example. This means that at a speed of 1500 rpm, a volume flow of 45 l / min is conveyed. The electric motor 40 accelerates up to 3000 1 / min and thus the required volume flow of 90 l / min is achieved. Up to 1500 rpm is the electric motor 40 a torque of 15.9 Nm is required, which means that it can accelerate very quickly. After switching on the 20 cc pump by switching the switching valve at 1500 1 / min, the electric motor 40 a torque of 47.7 Nm is required. The switching signal is the speed that comes from the frequency converter, which is the current actual speed of the electric motor at all times 40 has. The electric motor 40 may be accelerated further up to 3000 1 / min in the overload range. This overload function is with the electric motor 40 and the frequency converter possible.

During the deceleration process, both constant pumps continue to deliver P1 and P2 active in the system until a threshold speed is reached again. This threshold speed does not have to be the same speed (usually significantly lower, for example 500 1 / min) as in the connection process for the switching valve. As a result, both fixed displacement pumps P1 and P2 are involved in the deceleration process, arises on the electric motor 40 a higher counter-torque and it is thus decelerated faster than if only a fixed displacement pump represents a counter-torque.

Disclosed is a pump arrangement - preferably as a constant pressure system - with a plurality of constant pumps connected in parallel, which are jointly driven by a variable-speed drive. Each fixed displacement pump has an assigned working line, in each of which a switching valve is arranged, via which a delivery volume flow of the assigned fixed displacement pump can be discharged to a tank. The working lines open into a common high-pressure line of the pump arrangement. According to the invention, the switching valves can be switched or actuated for deactivating or switching ineffectively or for activating or switching on the associated constant pump as a function of a respective threshold speed of the variable-speed drive. This is preferably done via a control loop. This creates a pump arrangement whose variable-speed drive can largely be operated in a wide speed range.

List of reference symbols

1

consumer

2, 4, 6

Work management

8th

High pressure line

10, 12, 14

Switching valve

16, 18, 20

Discharge line

21

Connecting line

22nd

Tank line

24, 26

check valve

28

filter

30th

cooler

32

Control line

34

Pressure sensor

36

Signal line

38

Control unit

40

Electric motor

42

drive shaft

44, 46

Connecting shaft

48, 50, 52

coupling

54, 56, 58

electrical line

60

One-way flow control valve

62

Pressure accumulator

P1

small fixed displacement pump

P2

medium fixed displacement pump

P3

large fixed displacement pump

T

tank

Claims (10)

Pump arrangement with several constant pumps (P1, P2, P3) which can be driven jointly by an electric motor (40), the speed of which can be set by a frequency converter via a control circuit (34, 38), each constant pump (P1, P2, P3) having one Working line (2, 4, 6) in each of which a switching valve (10, 12, 14) is arranged, via which a delivery volume flow of the assigned constant pump (P1, P2, P3) can be discharged to a tank (T), the individual working lines (2, 4, 6) open at a common high pressure connection or in a common high pressure line (8), characterized in that the switching valves (10, 12, 14) can be switched as a function of a threshold speed of the electric motor (40). Pump arrangement according to Claim 1 , wherein a constant working pressure can be generated in the high pressure line (8) at different speeds of the electric motor (40), the pump arrangement having the control circuit (34, 38) which has a pressure sensor (34) via which a load pressure in the high pressure line ( 8) can be determined, the switching valves (10, 12, 14) being switchable via the control circuit (34, 38). Pump arrangement according to one of the preceding claims, wherein the constant pumps (P1, P2, P3) can be coupled to one another or to the electric motor (40) via shafts (42, 44, 46) with clutches (48, 50, 52). Pump arrangement according to one of the preceding claims, wherein the constant pumps (P1, P2, P3) have different nominal delivery volumes. Pump arrangement according to one of the preceding claims, wherein the switching valves (10, 12, 14) are connected to the tank (T) via a common tank line (22), and wherein in the tank line (22) a cooler (30) or a filter ( 28) is arranged. Pump arrangement according to one of the preceding claims, wherein a pressure accumulator (62) is connected to the high pressure line (8). Pump arrangement according to Claim 6 , an adjustable one-way flow control valve (60) being arranged between the pressure accumulator (62) and the high-pressure line (8). Method for increasing a volume flow in the high pressure line (8) of a pump arrangement according to one of the preceding claims, comprising the steps: - increasing the speed of the electric motor (40); - Activation or connection of one of the constant pumps (P1, P2, P3) via the switching valve (10, 12, 14) assigned to it by means of the threshold speed; and - Increasing the speed of the electric motor (40). Method for reducing a volume flow in the high pressure line (8) of a pump arrangement according to one of the Claims 1 until 7th with the steps: - reducing the speed of the electric motor (40); - Deactivation or ineffective switching of one of the constant pumps (P1, P2, P3) via the switching valve (10, 12, 14) assigned to it by means of the threshold speed; and - reducing the speed of the electric motor (40). Procedure according to Claim 8 or 9 , whereby one of the constant pumps (P1, P2) is activated or switched on at a first threshold speed and the same constant pump (P1, P2) is deactivated or ineffective at a second threshold speed, the first threshold speed being greater than the second threshold speed.

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