EP2610049B1 - Method for controlling a hydraulic press - Google Patents

Description

The invention relates to a method for controlling a hydraulic press having at least one main pump which is drivable by means of a main electric motor and by means of a hydraulic fluid is conveyed to an adjustable press part, wherein the main electric motor during an idling phase of the hydraulic press switched off and switched on again at the end of the idling phase and is raised to a predetermined speed.

A hydraulic press is used, for example, for forming metal blanks and has at least one press part, for example a plunger, which can be moved by applying pressurized hydraulic fluid between different positions. When the plunger is in its rest position and is to be moved from this to a forming position, at least one main electric motor is activated, ie supplied with electrical energy and raised to a predetermined speed. The main electric motor drives a main pump, which delivers the hydraulic fluid under pressure to the plunger.

If the ram has reached its final position after forming, or if the press is in another idle or idling phase, no further hydraulic fluid needs to be pumped for a short time. In order to reduce the consumption of electrical energy of the press, it has been attempted to switch off the main electric motor during the idling phase. If the main electric motor is then switched on again at the end of the idle phase, however, a significantly higher electrical load of the main electric motor occurs than in the switched-on state under load changes. At relatively short idling phases and, associated with a high turn-off and turn-on frequency of the main electric motor, the wear of the switching devices is relatively high and their life correspondingly short.

In order to increase the life of the switching devices of the main electric motor, it is known to run this constantly and to change the amount of hydraulic fluid delivered not by the speed of the main electric motor, but by means of a variable in the flow pump, which also Zero can be made so that a promotion of the hydraulic fluid is omitted. Disadvantage of this procedure, however, is that the constantly running main electric motor consumes relatively much electrical energy.

In the WO 2012/055579 A9 a hydraulic press is shown in which the hydraulic fluid displaced during lowering of the piston is conveyed through a first pump into a storage tank and additionally through a second pump into another cylinder chamber. In this way, by means of the servomotors in the usual way electrical Energy to be recovered, which is stored. For this purpose, the electric motors associated with the pumps are operated as generators. However, a corresponding energy recovery is not the subject of the present invention, but this relates to an engine-start-up concept to avoid excessive switching movements of the electric motor, as shown above.

The invention has for its object to provide a method for controlling a hydraulic press of the type mentioned, in which on the one hand the stresses of the main electric motor and the switching devices are avoided at startup and on the other hand, the consumption of electrical energy less than a constantly running main -Electric motor is.

This object is achieved by a method according to one of the independent claims 1 to 4.

In the embodiments according to claims 1 or 2 it is provided that the main pump for starting the main electric motor is switched to a drive mode in which it is driven by the hydraulic fluid flowing through it and drives the main electric motor, and that the hydraulic fluid is conveyed by the main pump by means of an auxiliary drive, so that the main pump drives the main electric motor, wherein the main electric motor is supplied with electrical energy upon reaching a predetermined speed and the main pump is switched to a pump mode in which it promotes the hydraulic fluid in the usual way.

The auxiliary drive is in one embodiment of the invention to an auxiliary electric motor which drives an auxiliary pump, by means of which the hydraulic fluid is conveyed through the main pump. The auxiliary electric motor can be in constant operation with relatively low power, which consumes only low electrical energy.

Large hydraulic presses are equipped with several main pumps, each with a main electric motor. The main pumps can deliver the hydraulic fluid to different adjustable press parts. In such an embodiment of the invention, one of the main electric motors together with the main pump associated with it forms the auxiliary drive and promotes the hydraulic fluid through the at least one other main pump, whereby it is driven and in turn the associated further main electric motor on the desired speed brings or keeps on this.

The basic idea of this embodiment of the invention is not to drive up the main electric motor from standstill or a greatly reduced speed by means of electrical energy, but first to accelerate the main electric motor by means of the associated main pump until a predetermined speed, For example, the idle speed of the main electric motor is reached, and only then to connect the main electric motor to the mains, ie to apply electrical energy.

The main pump is switchable between a normal operating mode, ie the pump mode, in which it is common Way that promotes hydraulic fluid, and a drive mode in which it is driven by the hydraulic fluid flowing through them and thereby drives the main electric motor connected to it and brings to the desired speed.

It only makes sense to turn off the main electric motor and let it leak or even come to a halt when the idle or idle phase of the hydraulic press is relatively long. Since this is not the case in many cases, the above object is achieved in this case according to the invention by a method according to claims 3 or 4. In this case, it is provided that the main pump is switched to a drive mode in which it is driven by the hydraulic fluid flowing through it and drives the main electric motor, so that it is maintained at a predetermined speed that the hydraulic fluid by means of an auxiliary drive through the Main pump is pumped so that the main pump drives the main electric motor, and that the main electric motor then supplied with electrical energy and the main pump is switched to a pump mode.

The auxiliary drive is in one embodiment of the invention to an auxiliary electric motor which drives an auxiliary pump, by means of which the hydraulic fluid is conveyed through the main pump. The auxiliary electric motor can be in constant operation with relatively low power, which consumes only low electrical energy.

Large hydraulic presses are equipped with several main pumps, each assigned a main electric motor is. The main pumps can deliver the hydraulic fluid to different adjustable press parts. In such an embodiment of the invention, one of the main electric motors together with the main pump associated with it forms the auxiliary drive and promotes the hydraulic fluid through the at least one other main pump, whereby it is driven and in turn the associated further main electric motor on the desired speed brings or keeps on this.

When the idle phase of the hydraulic press is relatively short, the main electric motor is maintained at a speed close to its idle speed. However, this is not achieved by electrical energy according to the invention, but the main electric motor is kept at the predetermined speed by means of the associated main pump. Only at the end of the resting or idle phase of the hydraulic press, i. when again a promotion of hydraulic fluid is necessary, the main electric motor is reconnected to the mains and supplied with electrical energy and the main pump is switched to the pump mode in which it conveys the hydraulic fluid in a conventional manner.

The hydraulic fluid can be conveyed by the auxiliary pump through the main pump and thereby drive them.

When the main electric motor is driven by the main pump and brought to or maintained at the desired rotational speed, the rotational speed of the main electric motor is preferably monitored by means of a tachogenerator. Alternatively, it is possible to detect the actual rotational speed of the main electric motor by means of a frequency measurement at the motor terminals of the motor separated from the three-phase network. In this embodiment, a tachogenerator can be omitted.

A speed signal corresponding to the actual speed of the main engine is fed to a controller in which it is checked whether the main electric motor is running at a desired speed or has already reached it. When this is the case at the time of starting the main electric motor, the main electric motor is switched to be supplied with and driven by electric power. At the same time, the main pump is switched to the pump mode where it is driven by the main electric motor and pumps the hydraulic fluid.

Fig. 1

ein Schaltschema einer ersten Ausführungsform der Erfindung,

Fig. 2

ein Schaltschema einer zweiten Ausführungsform der Erfindung und

Fig. 3

ein Schaltschema einer dritten Ausführungsform der Erfindung.

Further details and features will become apparent from the following description of exemplary embodiments with reference to the drawing. Show it:

Fig. 1

a circuit diagram of a first embodiment of the invention,

Fig. 2

a circuit diagram of a second embodiment of the invention and

Fig. 3

a circuit diagram of a third embodiment of the invention.

The FIG. 1 shows a section of the hydraulic circuit arrangement of a hydraulic press. A main pump P ₁ is connected via a line L ₁ with a supply V of hydraulic fluid in connection and can suck them from the supply V and to lead in a line L ₂ a consumer, not shown.

In line L ₂ , a check valve RS is arranged, which is unlocked via a switching valve YRS.

Downstream of the check valve RS branches from the line L _{2 from} a line L ₃ , in which an auxiliary pump P _{H is} arranged, which is connected via a line L ₄ with a supply V 'of hydraulic fluid in communication. The auxiliary pump P _H is driven by means of an auxiliary electric motor M _H. Further, in the line L _3, a release valve Y is arranged.

The main pump P ₁ is connected to a main electric motor M ₁ , which is supplied with electrical energy, which can be switched on and off by means of a switch K in the form of a power contactor. The speed of the main electric motor M ₁ is detected by means of a tachogenerator T, which supplies a corresponding speed signal to a controller for evaluation.

The main pump P ₁ can be switched between a normal pump mode and a drive mode.

If the consumer, not shown, must be supplied with hydraulic fluid, the main electric motor M ₁ supplied with electrical energy and rotated, causing the located in pump mode main pump P _{1 is} driven and thereby sucks hydraulic fluid from the supply V via the line L ₁ and fed through the check valve RS in the line L _{2 to} the consumer ,

In a relatively long idling phase of the hydraulic press, ie when no hydraulic fluid has to be conveyed to the consumer, the main electric motor M _{1 is turned off} by means of the switch K, whereby the main pump P ₁ comes to a standstill or in speed at least strong is lowered.

In order to start up the main electric motor M ₁ again, first the check valve RS is unlocked via the switching valve YRS and the release valve Y is opened. The main pump P ₁ is switched to its drive mode. The hydraulic fluid is then sucked from the auxiliary pump P _H , which is driven by the auxiliary electric motor M _H , from the supply V 'and fed via the line L ₃ and the line L ₂ through the main pump P _{1 to} the supply V. In this case, the hydraulic fluid flows through the main pump P ₁ , which is in its drive mode, that is, it is driven by the hydraulic fluid flowing through it, thus driving the main electric motor M ₁ , whereby this is powered up.

The rotational speed of the main electric motor M ₁ is detected by means of the tachogenerator T. When the controller determines that the rotational speed of the main electric motor M _{1 has reached} a desired rotational speed, the switch K is activated, whereby the main electric motor M ₁ with electrical energy supplied and driven. At the same time, the associated main pump P _{1 is} again switched to the pump mode in which it is driven by the main electric motor M ₁ . The check valve RS is again locked and the release valve Y closed again, so that the hydraulic fluid can be supplied in the manner mentioned from the supply V to the consumer.

In a relatively short idle phase of the hydraulic press, the main electric motor M _{1 is maintained} at a predetermined speed. For this purpose, the hydraulic fluid from the auxiliary pump P _H from the supply V 'through the main pump P ₁ supplied to the supply V in the aforementioned manner. The main pump P ₁ in its drive mode is driven by the hydraulic fluid flowing through it, thereby driving the main electric motor M ₁ . As soon as the controller recognizes that the main pump P ₁ is in its drive mode and is driven by the hydraulic fluid, the supply of electrical energy to the main electric motor M _{1 is} switched off by means of the switch K. The main electric motor M ₁ is then maintained by the main pump P ₁ at a desired speed, in particular close to the idling speed, which is monitored by the tachogenerator T and controlled by the controller. At the end of the idling phase of the hydraulic press, the main electric motor M _{1 is} reconnected to the electric power supply via the switch K, and the main pump P ₁ is returned to the pump mode in which it is driven by the main electric motor M ₁ , The valves are switched so that the hydraulic fluid can be supplied in the manner mentioned from the supply V to the consumer.

Also FIG. 2 showed a section of the hydraulic circuit of a hydraulic press. Here is a first main pump P ₁ via a line L ₁ with a supply V ₁ of hydraulic fluid in connection and can suck them from the supply V ₁ and perform in a line L ₂ a consumer, not shown. In line L ₂ , a check valve RS is arranged, which is unlocked via a switching valve YRS.

The first main pump P ₁ is connected to a first main electric motor M ₁ , which is supplied with electrical energy, which can be switched on and off by means of a switch K in the form of a power contactor. The speed of the first main electric motor M ₁ is detected by means of a tachogenerator T, which supplies a corresponding speed signal to a controller for evaluation. The first main pump P ₁ can be switched between a normal pump mode and a drive mode.

Parallel to the first main pump P ₁ , a second main pump P _{2 is} arranged, which is connected via a line L ₅ with a supply V ₂ of hydraulic fluid in connection and suck them from the supply V ₂ and in a line L ₆ the can supply consumers not shown. In the line L ₆ , a further check valve RS2 is arranged and downstream of the check valve RS2, the lines L ₂ and L _{6 are} merged.

The second main pump P ₂ is connected to a second main electric motor M ₂ , which is supplied with electrical energy by means of a switch K in the form of a Power contactor can be switched on and off.

To supply the consumer, not shown, with hydraulic fluid, the two main electric motors M ₁ and M _{2 are} each supplied with electrical energy and rotated, whereby the main pumps P ₁ and P _{2 are} driven and each hydraulic fluid from the respective supply V ₁ or V ₂ via the lines L ₁ and L ₅ suck and supply via the lines L ₂ and L _{6 to} the consumer.

In a relatively long idling phase of the press, ie when no hydraulic fluid has to be conveyed to the consumer, the first main electric motor M _{1 is turned off} by means of the switch K, whereby the first main pump P ₁ comes to a standstill or at least in speed is lowered greatly. The second main electric motor M ₂ continues to run, wherein the second main pump P ₂ , which is adjustable in the delivery quantity, is switched to zero, that is, it does not deliver any hydraulic fluid.

In order to start up the first main electric motor M ₁ again when needed, the check valve RS is initially unlocked via the switching valve YRS. The hydraulic fluid is then drawn from the second main pump P ₂ , which is driven by the second main electric motor M ₂ , from the supply V ₂ via the lines L ₆ and L ₂ through the first main pump P ₁ through the supply V ₁ supplied. In this case, the hydraulic fluid flows through the first main pump P ₁ , which is in its drive mode, that is, it is driven by the hydraulic fluid flowing through it, thus driving the first main electric motor M ₁ , whereby this is started up. The rotational speed of the first main electric motor M ₁ is detected by means of the tachogenerator. When the controller determines that the rotational speed of the first main electric motor M _{1 has reached} a desired rotational speed, the switch K is activated, whereby the first main electric motor M ₁ is supplied with electric power and driven. At the same time, the associated first main pump P _{1 is} again switched to the pump mode in which it is driven by the first main electric motor M ₁ . The check valve RS is locked again, so that the hydraulic fluid can be supplied in the manner mentioned by means of the two main pumps P ₁ and P ₂ from the respective supply V ₁ and V _{2 to} the consumer.

When the idling phase of the hydraulic press is relatively short, the first main electric motor M _{1 is} disconnected from the electric power supply by means of the switch K, but kept at a predetermined speed by the first main pump P ₁ , with the first main pump P _{1 is} in its drive mode and is driven by the pumped by the second main pump P ₂ hydraulic fluid. Details are described in connection with Figure 1, but now the auxiliary drive is formed by the second main pump P ₂ .

FIG. 3 shows a further alternative hydraulic circuit arrangement of a press according to the invention. Here, too, is a main pump P ₁ via a line L ₁ with a supply V of hydraulic fluid in connection and can suck them from the supply V and supply in a line L ₂ a consumer who in the illustrated embodiment of a hydraulically adjustable plunger S. educated is, which is adjustably received and guided in a cylinder Z. In the line L ₂ , a check valve RS, which is unlocked via a switching valve YRS, and a release valve Y are arranged.

The main pump P ₁ is connected to a main electric motor M ₁ , which is supplied with electrical energy, which can be switched on and off by means of a switch K in the form of a power contactor. The speed of the main electric motor M ₁ is detected by means of a tachogenerator T, which supplies a corresponding speed signal to a controller for evaluation. The main pump P ₁ can be switched between a normal pump mode and a drive mode.

When hydraulic fluid in the cylinder Z for adjusting the plunger S must be promoted, the main electric motor M ₁ is supplied with electrical energy and rotated, whereby the main pump P _{1 is} driven, thereby hydraulic fluid from the supply V on the Line L ₁ sucks and feeds through the check valve RS and the release valve Y to the cylinder Z.

In an idle phase, ie when no hydraulic fluid to the consumer must be promoted, the main electric motor M _{1 is turned off} by means of the switch K, whereby the main pump P ₁ comes to a standstill. In order to start up the main electric motor M ₁ again, the check valve RS is unlocked via the switching valve YRS and the release valve Y is opened. The main pump P ₁ is switched to the drive mode. The displacement of the plunger S in the cylinder Z displaces the hydraulic fluid from the cylinder Z and promotes this through the line L ₂ and the line L ₁ in the supply V, wherein the main pump P ₁ flows through and is driven thereby. In this way, the main pump P ₁ drives the main electric motor M ₁ , causing it to start up. The rotational speed of the main electric motor M ₁ is detected by means of the tachogenerator T. Once the desired speed of the electric motor M _{1 is} reached, the switch K is activated, whereby the main electric motor M ₁ is supplied with electrical energy and driven. The main pump P ₁ remains in its drive mode until a predetermined position of the plunger is reached. Subsequently, the main pump P _{1 is switched} to the pump mode, so that the hydraulic fluid can be sucked in the aforementioned manner by means of the main pump P ₁ from the supply V and the cylinder Z can be supplied.

Claims (6)

1. Method for controlling a hydraulic press which has at least one main pump (P₁) which can be driven by means of a main electric motor (M₁) and by means of which a hydraulic fluid can be conveyed to an adjustable press part (S), the main electric motor (M₁) being switched off during an idling phase of the hydraulic press and being switched on again at the end of the idling phase and being run up to a predefined rotational speed, the main pump (P₁) being switched into a drive mode in order to run up the main electric motor (M₁), in which drive mode said main pump (P₁) is driven by the hydraulic fluid, which flows through it, and drives the main electric motor (M₁), and the hydraulic fluid being conveyed through the main pump (P₁) by means of an auxiliary drive (M_H, P_H), with the result that the main pump (P₁) drives the main electric motor (M₁), the auxiliary drive being an auxiliary electric motor (M_H) which drives an auxiliary pump (P_H), by means of which the hydraulic liquid is conveyed through the main pump (P₁), and the main electric motor (M₁) being supplied with electric energy when a predefined rotational speed is reached, and the main pump (P₁) being switched into a pump mode.
2. Method for controlling a hydraulic press which has at least one main pump (P₁) which can be driven by means of a main electric motor (M₁) and by means of which a hydraulic fluid can be conveyed to an adjustable press part (S), the main electric motor (M₁) being switched off during an idling phase of the hydraulic press and being switched on again at the end of the idling phase and being run up to a predefined rotational speed, the main pump (P₁) being switched into a drive mode in order to run up the main electric motor (M₁), in which drive mode the said main pump (P₁) is driven by the hydraulic fluid, which flows through it, and drives the main electric motor (M₁), and the hydraulic fluid being conveyed through the main pump (P₁) by means of an auxiliary drive (M₂, P₂), with the result that the main pump (P₁) drives the main electric motor (M₁), the hydraulic press having at least two main pumps (P₁, P₂) which are assigned in each case one main electric motor (M₁, M₂) and by way of which the hydraulic fluid can be conveyed to the adjustable press part, one of the main electric motors (M₂) forming the auxiliary drive together with the main pump (P₂) which is assigned to it, and conveying the hydraulic fluid through the at least one further main pump (P₁) and driving the latter, and the main electric motor (M₁) being supplied with electric energy when a predefined rotational speed is reached, and the main pump (P₁) being switched into a pump mode.
3. Method for controlling a hydraulic press which has at least one main pump (P₁) which can be driven by means of a main electric motor (M₁) and by means of which a hydraulic fluid can be conveyed to an adjustable press part (S), the main electric motor (M₁) being switched off during an idling phase of the hydraulic press and being switched on again at the end of the idling phase, the main pump (P₁) being switched into a drive mode, in which it is driven by the hydraulic fluid, which flows through it, and drives the main electric motor (M₁), with the result that the latter is held at a predefined rotational speed, and the hydraulic fluid being conveyed through the main pump (P₁) by means of an auxiliary drive (M_H, P_H), with the result that the main pump (P₁) drives the main electric motor (M₁), the auxiliary drive being an auxiliary electric motor (M_H) which drives an auxiliary pump (P_H), by means of which the hydraulic fluid is conveyed through the main pump (P₁), and the main electric motor (M₁) subsequently being supplied with electric energy again, and the main pump (P₁) being switched into a pump mode.
4. Method for controlling a hydraulic press which has at least one main pump (P₁) which can be driven by means of a main electric motor (M₁) and by means of which a hydraulic fluid can be conveyed to an adjustable press part (S), the main electric motor (M₁) being switched off during an idling phase of the hydraulic press and being switched on again at the end of the idling phase, the main pump (P₁) being switched into a drive mode, in which it is driven by the hydraulic fluid, which flows through it, and drives the main electric motor (M₁), with the result that the latter is held at a predefined rotational speed, and the hydraulic fluid being conveyed through the main pump (P₁) by means of an auxiliary drive (M₂, P₂), with the result that the main pump (P₁) drives the main electric motor (M₁), the hydraulic press having at least two main pumps (P₁, P₂) which are assigned in each case one main electric motor (M₁, M₂) and by way of which the hydraulic fluid can be conveyed to the adjustable press part, one of the main electric motors (M₂) forming the auxiliary drive together with the main pump (P₂) which is assigned to it, and conveying the hydraulic fluid through the at least one further main pump (P₁) and driving the latter, and the main electric motor (M₁) being supplied with electric energy when a predefined rotational speed is reached, and the main pump (P₁) being switched into a pump mode.
5. Method according to one of Claims 1 to 4, characterized in that the rotational speed of the main electric motor (M₁) is monitored and a corresponding rotational speed signal is fed to a controller.
6. Method according to Claim 5, characterized in that the rotational speed of the main electric motor (M₁) is detected by way of frequency measurement at the motor terminals of the motor which is disconnected from the three-phase supply.

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