EP1230998B1 - Method of automatically controling electro-hydraulic handtools and assembly therefor - Google Patents

Abstract

The control method uses a microprocessor (15) for controlling a pump motor (12) for a hydraulic pump (5) supplying the drive cylinder of the electro-hydraulic handtool, with detection of the pump motor current and the current drop after opening an over-pressure valve (9) inserted in the hydraulic fluid return flow path. The pump motor current is disconnected after the motor current drops below a stored current value, via a load switch (14). An Independent claim for an automatic control device for an electro-hydraulic handtool is also included.

Description

The invention relates to a method for automatically controlling electro-hydraulic hand tools according to the preamble of patent claim 1 and an arrangement here for according to the preamble of claim 3. Such a method and such an arrangement are known from the DE 195 35 691 C1 ,

In numerous machining operations of workpieces, especially when connecting pipes in the heating and sanitary sector, it is necessary to comply with the most accurate time and force course. On the one hand, the maximum force must be sufficiently high to ensure a safe working result, e.g. To achieve a permanently sealed pipe connection, on the other hand, the maximum force must not exceed the strength of the workpiece or the tool. These demands are difficult to meet together. In addition, the requirements for control options of the work processes and the function of the tools, possibly also in connection with maintenance, inspection and warranty provisions.

By the DE 21 36 782 C2 is a pneumatically or hydraulically powered hand tool with a working piston and a press head for the manufacture of pipe joints known. The working piston is returned to the initial position by a return spring after each pressing process led back. However, the pressure medium generation and control is not part of the hand tool and also not described.

By the US-A-2 254 613 is a hydraulic press with a hand pump, known with a working piston and a press head, in which the working piston is also performed after each pressing operation by its return spring to the starting position. The return movement takes place until the end automatically by a arranged in a bypass and pilot-operated pressure relief valve, which has a conical tip and a downstream larger valve plate, which is effective after opening the apex. This gives the valve a hysteresis behavior, ie, it is kept open even with decreasing pressure by the hydraulic fluid. The hand press also has an EMERGENCY button. An electrical or electronic control of the hydraulic system is neither provided nor possible because of the hand pump.

By the DE 195 35 691 C1 the same applicant is known an electro-hydraulic hand tool, which also has a working piston and is provided for the placement of a press head. In this case, the working piston is also performed after each pressing operation by its return spring to the starting position. The return movement takes place until. End automatically through a valve system arranged in a bypass. An electrical or electronic control of the hydraulic system is not provided. Rather, there is a hydraulic-mechanical locking of the operating switch until the end of the pressing process. A press head for this is in the DE 44 46 504 C1 described.

By the alien EP 0 445 084 A2 it is in an electric, non-hydraulic screwdriver for expandable hollow dowels known to initiate the shutdown of the motor when reaching the maximum power consumption and automatically reverse the direction of rotation. This is the case when the current consumption exceeds a preset preset value. By a delay circuit is ensures that the final state of the clamping or spreading is actually achieved.

By the DE 295 02 032.6 U1 it is known in an electro-hydraulically driven pressing tool to turn off the electric motor upon reaching a predetermined pressing pressure, which is determined indirectly by measuring the power consumption. This should allow the user to visually determine whether the press jaws of the press tool are really closed and the complete compression of a pipe joint is achieved. However, visual control is only possible when the user leaves the ergonomic position of the machine operator. Thereafter, the user must manually switch the direction of rotation of the motor to remove the tool from the pipe joint can. A pressure limitation by a hydraulic pressure relief valve and an automatic tracking of the motor current taking into account predetermined current values are not provided. Due to the lack of a pressure relief valve, the current drop after the response of such a valve can not be detected and evaluated for control purposes.

By the EP 0 824 979 A1 It is known to provide an electromagnetic encoder in the form of a distance sensor between the cheek plates of a press head, which automatically reduces the engine power when approaching the cheek plates to reduce the kinetic energy of the drive system after covering the Leerhubs and before reaching the end position of the cheek plates and thereby This is to avoid overloading of the cheek plates and premature wear of bearing points in the press head and its drive system despite complete compression of the pipe connection Current values are not provided Although a pressure relief valve is disclosed, but only for the purpose of Endkraftbegrenzung, but not to control and control the Motorabsc attitude.

Through the abstract of JP 11198058 A it is known in a purely electrically driven tool for producing beads to monitor the course of the motor current through a current sensor. When exceeding a predetermined value for the motor current, a microcomputer is started with a timer. When exceeding two seconds and a smaller increase in the motor current, a light emitting diode lights up to indicate to the operator that the pressing is completed. Neither the monitoring of the response of a (not disclosed) pressure relief valve by current measurement is disclosed nor the automatic engine shutdown after falling below a stored lower current value.

The invention is based on the object to provide a hand tool of the type described above, in which the pump motor is controlled at least substantially by the pressure curve in the hydraulic system.

The solution of the object is achieved in the method according to the preamble of claim 1 by the features in the characterizing part of patent claim 1 and in the arrangement according to the preamble of claim 3 by the features in the characterizing part of claim 3.

By these solutions, the object is achieved to the full extent, in particular a hand tool of the type described above is given, in which the pump motor is controlled at least substantially by the pressure curve in the hydraulic system. The invention is based on the consideration that the motor current of the pump motor is a sufficiently accurate or proportional image of the pressure curve in the hydraulic system and thus the flow of forces during operation, and that this property after conversion of the motor current into electrical or electronic signals to control and control the operation by a microprocessor with data storage and memory locations can be used for predefinable and possibly variable setpoints and operating parameters. The signal evaluation can be further developed in connection with stored time-dependent signals and process parameters. Further advantages are given in the detailed description.

• * das Einleiten des Arbeitsvorganges durch eine gespeicherte Sperrzeit verzögert wird und wenn die gesamte Einschaltdauer des Motorstromes durch einen gespeicherten Maximalzeitwert begrenzt wird.

It is in the course of a further embodiment of the method particularly advantageous if - either individually or in combination -:

• * The initiation of the operation is delayed by a stored lock time and when the total duty cycle of the motor current is limited by a stored maximum time value.

• * zwischen einer Stromquelle für den Motorstrom ein Spannungssensor für die Messung der Spannung der Stromquelle angeordnet ist und wenn der Spannungssensor dem Mikroprozessor aufgeschaltet ist,
• * zwischen dem Spannungssensor und dem Mikroprozessor ein Spannungsregler für die Betriebsspannung des Mikroprozessors angeordnet ist,
• * dem Mikroprozessor ein Analog-Digital-Wandler zugeordnet ist, dem die Ausgänge des Stromsensors und des Spannungssensors aufgeschaltet sind,
• * dem Mikroprozessor in Parallelschaltung mindestens zwei Schalter für die lageunabhängige Bedienung des Handwerkzeugs aufgeschaltet sind,
• * die Schalter nach Ablauf der Sperrzeit blockierbar sind,
• * dem Mikroprozessor eine Signaleinrichtung für die Anzeige des Betriebszustandes des Handwerkzeugs zugeordnet ist,
• * die Signaleinrichtung als blinkende Mehrfach-Farbanzeige ausgebildet ist,
• * dem Mikroprozessor mindestens ein Datenspeicher für die Betriebshistorie des Handwerkzeugs zugeordnet ist,
• * dem Mikroprozessor eine Schnittstelle für die Abfrage der Betriebshistorie zugeordnet ist,
• * dem Mikroprozessor mindestens ein Wartungszähler für die Speicherung und Anzeige von Wartungsintervallen und Inspektionsfälligkeiten des Handwerkzeugs zugeordnet ist,
• * der Schnittstelle ein Infrarot-Übertrager zugeordnet ist, und/oder, wenn
• * im Datenspeicher eine maximale Leerlaufzeit für den Pumpenmotor und ein Minimalwert für den Motorstrom abgelegt sind, und wenn die Anordnung so getroffen ist, daß der Pumpenmotor wieder ausgeschaltet wird, wenn der Minimalwert für den Motorstrom nicht innerhalb der Leerlaufzeit überschritten wird.

It is in the course of further embodiments of the arrangement particularly advantageous if - either individually or in combination -:

• * between a current source for the motor current, a voltage sensor for measuring the voltage of the power source is arranged and when the voltage sensor is switched to the microprocessor,
• * a voltage regulator for the operating voltage of the microprocessor is arranged between the voltage sensor and the microprocessor,
• * the microprocessor is associated with an analog-to-digital converter to which the outputs of the current sensor and the voltage sensor are connected,
• the microprocessor is connected in parallel with at least two switches for the position-independent operation of the hand tool,
• * the switches are blockable after expiry of the blocking period,
• * the microprocessor has a signaling device for the display of the Operating state of the hand tool is assigned,
• * the signaling device is designed as a flashing multi-color display,
• * the microprocessor is assigned at least one data memory for the operating history of the hand tool,
• * the microprocessor is assigned an interface for querying the operating history,
• * the microprocessor is assigned at least one maintenance counter for the storage and display of maintenance intervals and inspection delays of the hand tool,
• * the interface is assigned an infrared transmitter, and / or, if
• * a maximum idle time for the pump motor and a minimum value for the motor current are stored in the data memory, and if the arrangement is such that the pump motor is switched off again, if the minimum value for the motor current is not exceeded within the idle time.

An embodiment of the invention and its operation will be described below with reference to FIGS. 1 and 2 explained in more detail.

Figur 1

ein Schaltbild einer Anordnung zum Steuern von elektro-hydraulischen Handwerkzeugen zum Herstellen von Rohrverbindungen durch plastische Verformung von Rohrwerkstoffen,

Figur 2

Kurvendarstellungen der Stromverläufe bei verschiedenen Betriebszuständen über der Zeit.

Show it:

FIG. 1

a circuit diagram of an arrangement for controlling electro-hydraulic hand tools for producing pipe joints by plastic deformation of pipe materials,

FIG. 2

Curves of the current curves at different operating states over time.

In FIG. 1 a drive cylinder 1 is shown with a one-sided working piston 2, which is acted upon by a return spring 3 and has a piston rod 4. This piston rod can for example be provided with spreading rollers for a replaceable press head, not shown here, as it is used for the radial compression of pipe couplings. Such a press pot in the DE 44 46 504 C1 disclosed.

The hand tool has a pump 5, which is arranged in a delivery line 6 between a tank 7 and the drive cylinder 1, and provided as a bypass return line 8, which connects the drive cylinder 1 to the tank 7 and arranged in a pilot-operated pressure relief valve 9 with hysteresis is. The design and adjustment of the pressure relief valve 9 (spring / valve surface) must be in any case so that the valve does not open before reaching the predetermined maximum pressing force (safety of the press connection). The dependencies are u.a. the following: 1. The deformation resistance (inter alia, depending on pipe material, pipe pairing and pipe diameter) and 2. the hydraulic fluid in connection with flow cross-sections, viscosity and temperature.

The design of the pressure relief valve 9 is in the direction that with the hand tool, e.g. By exchanging the press head, it is possible to produce pipe connections of different diameters (for example, from 16 to 54 mm in diameter), the design additionally corresponding to a safety margin for the largest possible diameter of the pipe connection. In all cases, the pressure rises steeply at the end of a pressing process in that the press jaws of the press head meet. This is also the case with tube head press heads at the lower end of the above range. The pressure relief valve 9 is still associated with an emergency release lever, not shown here, with which the valve can be opened at any time by hand.

On both sides of the pump 5 check valves 10 and 11 are provided. The hydraulic part of the arrangement is eg in the US-A-2 254 613 described, however in connection with a hand pump.

In the present case, the pump 5 is driven by an electric pump motor 12, in the supply line 13 as a semiconductor switch (e.g., MOS) formed circuit breaker 14 is arranged, through which the pump motor 12 is driven current and time-dependent by a microprocessor 15. In the supply line 13 of the pump motor 12, a current sensor 16 is arranged, the output of the microprocessor 15 is connected via a line 17 for the purpose of comparison with at least one stored setpoint for the motor current. The associated output of the microprocessor 15 is connected to the power switch 14 via a line 18.

The electronic control is based on two principles, namely a) current-dependent and b) time-dependent. The current sensor 16 detects the current consumption "i" of the motor and thereby the pressing force "K". The pressing force is approximately proportional to the current consumption. The current consumption is also approximately proportional to the hydraulic pressure "P" (see also FIG. 2 ).

For this purpose, the microprocessor is assigned a data memory 19 designed as an EEPROM with at least one memory location for a setpoint value for the motor current and with at least two further memory locations for a minimum and a maximum switch-on duration of the pump motor 12. The operating programs and setpoints for pressures and time values are also stored in this data memory FIG. 2 will be explained in more detail.

The arrangement also has a power source 20, which is designed as a power supply, network connection, but preferably as an accumulator. Between this current source 20 for the motor current and the microprocessor 15, a voltage sensor 21 for measuring the voltage of the current source 20 is arranged, and the voltage sensor 21 is connected to the microprocessor 15 via a line 22 for control purposes. The control is used, inter alia, the state of charge of the accumulator or the Mains voltage to prevent malfunctions. If, for example, a reference value stored in the data memory 19 for the voltage is undershot, then the pump motor is immediately switched off again, since the capacity is no longer sufficient for a proper pressing operation.

Furthermore, a voltage regulator 23 for the operating voltage of the microprocessor 15 is arranged between the voltage sensor 21 and the microprocessor 15. The microprocessor 15 is associated with an analog-to-digital converter 24, to which the outputs of the current sensor 16 and the voltage sensor 21 are connected.

Further, the microprocessor 15 in parallel four switches 25 are switched for the position-independent operation of the hand tool, e.g. for operation with the right or left hand and / or for operating the device in different spatial positions, which may be due to limited space when working.

To the microprocessor 15, a signal device 26 is connected for the respective operating state of the hand tool, which is preferably designed as a multi-color display, for example as a two-color LED with the primary colors red and yellow, which lead to an orange signal when mixed, which is even closer below is explained.

The microprocessor 15 also has internal data memories for the operating history of the hand tool and an interface 27 for retrieving the stored history of operation via an infrared transmitter 28. The data memories formed as counters are incremented during each operation. A total counter counts all operations since the device was manufactured. A maintenance counter serves to maintain the necessary maintenance cycles. For example, if this counter registers 10,000 operations, the signaling device 26 flashes "yellow" five times after each operation to indicate to the operator that an inspection is due. This state is maintained until the maintenance counter through a handheld terminal via the interface 27 back to zero is set.

Via the infrared transmitter 28 all values stored in the data memories can also be read out and edited by means of the handheld terminal. This affects not only the counter readings, but also the stored parameters, which allow an adaptation of the entire device mechanics, including the motor and the current memory to the electronics. After loading the device, it works fully automatically.

The FIG. 2 now shows graphs of the current waveforms "i" different operating states over the time "t". By pressing one of the switches 25, the pump motor is turned on via the power switch 14 at time t1. Here, provides an immediately a corresponding starting current i _anl, of up to an idling current i falls rapidly _empty, which is represented by the curve portion K1. The period of time Δt between t1 and t2 is stored as a blocking time and is for example 400 ms. If the switch is operated shorter than .DELTA.t, the engine is immediately switched off again to prevent random operations initiate a work process.

Furthermore, it is possible by a short-term pressure on one of the switches 25 to initiate the infrared query without having to perform a work operation. Beyond t2, the switches 25 are blocked; they can be let go. By storing a further blocking period of a similar duration, it is possible to prevent the electronics from detecting and storing the starting current peak.

Subsequently, the voltage of the accumulator (as current source 20) is measured. A five flashes of red signaling device 26 is an indication that the battery is discharged. Also, the engine idling current i _empty is measured and stored once. This value is for detecting the operation of the EMERGENCY trip lever (not shown).

Then again the measurement of the motor current is continued.

If, during an idle time stored in the data memory 19, the motor current does not rise by a likewise stored difference, the motor is switched off again and the signal device 26 shows a faulty operation by five orange flashing, for example a machine defect or no working device, e.g. a press head was inserted, or that the emergency release lever was actuated immediately after the start.

If the motor current continues to rise, the operation is continued, that is, during a pressing operation, the cheek plates close as the motor current increases. After the cheek plates abut the workpiece, a metal pipe or a pipe coupling, the actual pressing begins, the current strength increases significantly. This will be in FIG. 2 represented by the curve section K2. The current consumption i _max at time t4 is predetermined by the already described force-dependent opening of the pressure relief valve 9.

From a stored in the data memory 19 limiting current strength occurring at time t4 response of the pressure relief valve 9 and thus the decrease in the current in the curve section K3 is no longer interpreted as actuation of the emergency release, but as proper opening of the valve after successfully completed operation, for example, at 12 to 18 A motor current is completed.

If the motor current at time t5 falls below a limiting current intensity i _stop likewise stored in the data memory 19, the pump motor 12 is switched off by the electronics and thus the power consumption is reduced to a quiescent current consumption of a few microamps, at which no work process is triggered.

If the EMERGENCY triggering is initiated by manually opening the overpressure valve 9 during a work process at the time t3 below the above limiting current, the current decreases in accordance with the curve section K6, and the pump motor 12 falls below the stored no-load current plus a safety margin off. Also in this case, the signaling device 26 blinks "orange" five times to display this process.

FIG. 2 shows the following: If the pump motor continue to run after opening the pressure relief valve 9 beyond t5, then the motor current drops correspondingly to the dashed curve section K4, but only relatively slowly, which depends on the delivery rate of the pump 5 and the flow resistance. By switching off the engine at time t5, however, the motor current corresponding to the curve section K5 drops steeply, and the working piston 2 is now pushed back much faster under the action of the return spring 3 to its original position, the displaced amount of oil in the tank 7 back is promoted and the valve then closes again.

However, in order not to allow the pump motor to continue to run endlessly in the event of malfunctions, a time t _{max is} stored in the data memory 19 at which the device switches off completely, for example after 10 to 15 seconds.

To be stored in memory locations are mainly the time points or time intervals Δt (limited by t1 and t2) and t _max . The times t3, t4 and t5 result from the course of the pressure curve in FIG. 2 and this curve may be longer or shorter in the direction of the abscissa, depending on the deformation characteristics of the workpiece, eg a pipe joint, the flow resistances in the hydraulic system due to the viscosity of the hydraulic fluid, which in turn depends on the temperature, etc. The timing t3 is preferable only because it is the timing of an emergency trip. The time t4 arises from the response of the (adjustable) pressure relief valve 9 at the maximum pressure, represented by the upper limit current value i _max , and the time t5 arises when falling below a predetermined, stored limit current value i _stop , which is necessarily smaller than the upper limit current value i _max at Response of the valve.

List of reference numbers:

1

drive cylinder

2

working piston

3

Return spring

4

piston rod

5

pump

6

delivery line

7

tank

8th

backflow

9

pressure relief valve

10

check valve

11

check valve

12

pump motor

13

supply line

14

breakers

15

microprocessor

16

current sensor

17

management

18

management

19

data storage

20

power source

21

voltage sensor

22

management

23

voltage regulators

24

Analog to digital converter

25

switch

26

signaling device

27

interface

28

Infrared transmitter

i

current consumption

i _max , i _stop

Limiting current values

i _anl

starting current

i _empty

No-load current

t1, t2, t3, t4, t5, t _max

timings

.delta.t

Duration, blocking time

K

pressing force

K1, K2, K3, K4, K5, K6

curve sections

P

hydraulic pressure

Claims (15)

1. A method of automatically controlling electrohydraulic hand tools, in particular when producing pipe connections through plastic deformation of pipe materials, wherein the hand tool has a drive cylinder (1) with a unilaterally-acting working piston (2) which is pushed back into its initial position by a return spring (3) in the event of pressure relief, as well as a pump (5), supplied from a tank (7), to drive the drive cylinder (1) and a return line (8) for the return flow of the hydraulic fluid to the tank (7), a pilot-operated pressure relief valve (9) with hysteresis effect being arranged in the return line (8), wherein the pump (5) is driven by an electric pump motor (12) in whose supply line (13) there is arranged a power switch (14), characterised in that the pump motor (12) is controlled in a current-dependent manner by a microprocessor (15) such that the currency consumption of the pump motor (12) and the currency drop after opening of the pressure relief valve (9) are determined by the microprocessor (15) and that the motor current is interrupted by the power switch (14) after there has been a fall below a stored current value (i_stop).
2. A method according to claim 1, characterised in that initiation of the operation is delayed by a stored blocked time (At), and in that the entire on-time of the motor current is limited by a stored maximum time value (t_max).
3. An arrangement for automatically controlling electrohydraulic hand tools, in particular for producing pipe connections through plastic deformation of pipe materials, having a drive cylinder (1) with a unilaterally-acting working piston (2) which is acted upon by a return spring (3) and has a piston rod (4), having a pump (5) arranged in a conveying line (6) between a tank (7) and the drive cylinder (1), having a return line (8) which connects the drive cylinder (1) to the tank (7) and in which a pilot-operated pressure relief valve (9) with hysteresis effect is arranged, and having an electric pump motor (12) in whose supply line (13) there is arranged a power switch (14), characterised in that the pump motor (5) is operated in a current-dependent manner by a microprocessor (15) associated with which there is at least one manually operable switch (25),

   a) a current sensor (16), whose output is connected to the microprocessor (15) for comparison with at least one stored desired value for the motor current, being arranged in the electrical supply line (13) of the pump motor (12),

   b) the output of the microprocessor (15) being connected to the power switch (14) in the supply line (13), and

   c) at least one data store (19) being associated with the microprocessor (15), in which data store (19) there are arranged storage locations, namely:

   c1) for a time duration Δt as a blocked time for a possible operating error,

   c2) for a maximum time duration t_max for shut-off in the event of faulty operation of the apparatus after actuation of the at least one switch (25) and

   c3) for at least one limit-current value (i_stop) for cutting off the motor current, which limit-current value (i_stop) is lower than a limit-current value (i_max) upon opening of the pressure relief valve.
4. An arrangement according to claim 3, characterised in that a voltage sensor (21) to measure the voltage of the current source (20) is arranged between a current source (20) for the motor current, and in that the voltage sensor (21) is connected to the microprocessor (15).
5. An arrangement according to claim 4, characterised in that a voltage regulator (23) for the operating voltage of the microprocessor (15) is arranged between the voltage sensor (21) and the microprocessor (15).
6. An arrangement according to claims 3 and 4, characterised in that an analogue-to-digital converter (24) is associated with the microprocessor (15) and the outputs of the current sensor (16) and the voltage sensor (21) are connected thereto.
7. An arrangement according to claim 3, characterised in that at least two switches (25) for position-independent operation of the hand tool are connected to the microprocessor (15) in a parallel connection.
8. An arrangement according to claim 7, characterised in that the switches (25) can be locked after the blocked time (Δt) has expired.
9. An arrangement according to at least one of claims 3 to 8, characterised in that a signal device (26) to indicate the operational state of the hand tool is associated with the microprocessor (15).
10. An arrangement according to claim 9, characterised in that the signal device (26) is in the form of a blinking multiple-colour indicator.
11. An arrangement according to claim 3, characterised in that at least one data store for the operating history of the hand tool is associated with the microprocessor (15).
12. An arrangement according to claim 3, characterised in that at least one maintenance counter for the storage and display of maintenance intervals and inspection due dates of the hand tool is associated with the microprocessor (15).
13. An arrangement according to claim 11, characterised in that an interface (27) for retrieval of the operating history is associated with the microprocessor (15).
14. An arrangement according to claim 13, characterised in that an infrared transducer (28) is associated with the interface (27).
15. An arrangement according to claim 3, characterised in that a maximum idle time for the pump motor (12) and a minimum value for the motor current are stored in the data store (15), and in that the arrangement is such that the pump motor (12) is switched off again when the minimum value for the motor current is not exceeded within the idle time.

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