DE10106360C1 - Automatic control method for electro-hydraulic handtool has microprocessor controlling pump motor via hydraulic system pressure - 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 the automatic control of electro-hydraulic hand tools according to the generic term of Claim 1 and an arrangement here for according to the preamble of Claim 3.

For numerous machining operations on workpieces, in particular when connecting pipes in the heating and sanitary area, it is necessary to adhere to a time and force curve that is as precise as possible. On the one hand, the maximum force must be sufficiently high to ensure a safe Work result, e.g. B. to achieve a permanently tight pipe connection, on the other hand, the maximum force must not be the strength of the workpiece still exceed that of the tool. These demands are common sam difficult to fulfill. Control requirements are also increasing Possibilities of the work processes and the function of the tools if necessary also in connection with maintenance, inspection and guarantee regulations regulations.

DE 21 36 782 C2 drives a pneumatically or hydraulically ben hand tool with a working piston and a press head known for making pipe connections. The working piston will  after each pressing process by a return spring in the starting position led back. However, the generation and control of pressure medium is not Part of the hand tool and also not described.

US 2 254 613 is a hydraulic press with one hand pump, known with a working piston and a press head, at the the piston also after each pressing process by its back spring is returned to the starting position. The reset move until the end is done automatically in a bypass arranged and pilot operated pressure relief valve that has a cone tip and has a downstream larger valve plate, which after the opening the cone tip takes effect. This will get the valve on Hysteresis behavior, d. that is, even with decreasing pressure, the Hydraulic fluid kept open. The hand press also has one Emergency release button. An electrical or electronic control of the Hydraulic system is neither intended nor because of the hand pump possible.

DE 195 35 691 C1 from the same applicant is an electro known hydraulic hand tool, which is also a working piston owns and is intended for attaching a press head. there the working piston is also replaced after each pressing process Return spring returned to the starting position. The reset move until the end is automatically indicated in a bypass ordered valve system. An electrical or electronic control of the Hydraulic system is not provided. Rather, there is a hydrau Mechanical-mechanical locking of the operating switch until termination of the pressing process. A press head for this is in DE 44 46 504 C1 described.

Due to the non-generic EP 0 445 084 A2, an electrical, non-hydraulic screwdriver known for expandable hollow dowels, the shutdown of the motor when the maximum current is reached initiate and reverse the direction of rotation automatically. This is then the case when the current consumption is a predetermined, preset  Value exceeds. Through a delay circuit ensures that the final state of bracketing or spreading is actually achieved.

DE 295 02 032 U1 makes it electrohydraulic driven press tool known to reach the electric motor switch off a predetermined pressing pressure, which indirectly by measuring solution of the current consumption is determined. This is intended to help the user be enabled to visually determine whether the press jaws of the Press tool are really closed and the full Compression of a pipe connection is reached. There is a visual check but only possible if the user is in the ergonomic position Machine operation leaves. Then the user has to change the direction of rotation switch the motor manually to remove the tool from the pipe ver to lose bond. A pressure limitation through a hydraulic pressure relief valve and automatic tracking of the Motor current taking into account given current values are not intended. The lack of a pressure relief valve also means that the current drop after the response of such a valve and evaluate for control purposes.

From EP 0 824 979 A1 it is known to insert a An electromagnetic displacement sensor in the form of a press head Provide distance sensor that the engine power when approaching the Press jaws automatically reduced to the kinetic energy of the Drive system after completing the empty stroke and before reaching it to reduce the end position of the press jaws and thereby the under different deformation forces of different pipe connections (Flow behavior of the material, wall thickness and diameter) into account. In this way, despite complete compression of the Pipe connection an overload of the press jaws and premature Wear of bearings in the press head and its drive system be prevented. Automatic tracking of the motor current under Taking current values into account is not provided. Though a pressure relief valve is disclosed, but only for the purpose of limiting the final force,  but not for checking and controlling the engine shutdown tung.

The abstract of JP 11198058 A makes it purely electrical powered tool for making beads known the course monitor the motor current by a current sensor. At the exceeding a specified value for the motor current is a Microcomputer started with a timer. When exceeding two seconds and a smaller increase in the motor current lights up an LED to indicate to the operator that the pressing process is finished. Neither is monitoring the response of one (not ) pressure relief valve by current measurement still discloses the automatic engine shutdown after falling below a saved lower current value.

The invention is based on the object, a craft to indicate the genus described above, in which the Pump motor at least essentially due to the pressure curve in the Hydraulic system is controlled.

The task is solved in the process according to Preamble of claim 1 by the features in the license plate of claim 1 and in the arrangement according to the preamble of Claim 3 by the features in the characterizing part of the patent claim 3.

With these solutions, the task at hand is fully met solved, in particular a hand tool of the type described Specified genus in which the pump motor at least essentially is controlled by the pressure curve in the hydraulic system. The Invention is based on the consideration that the motor current of the pumps motors a sufficiently accurate or proportional representation of the pressure course in the hydraulic system and thus the development of forces during work operation and that this property after implementation of the motor current in electrical or electronic signals for control and monitoring  the work process by a microprocessor with data storage and storage locations for predeterminable and possibly changeable setpoints and Operating parameters can be used. The signal evaluation can be done in Connection with stored time-dependent signals and process parameters meters further. Further advantages are in the details description given.

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

• - the initiation of the work process by a stored blocking time is delayed and if the entire duty cycle of the motor current mes is limited by a stored maximum time value.

In the course of further refinements of the arrangement, it is particularly advantageous if - either individually or in combination -:

• - A voltage sensor between a current source for the motor current is arranged for measuring the voltage of the power source and when the voltage sensor is connected to the microprocessor,
• - A span between the voltage sensor and the microprocessor voltage regulator for the operating voltage of the microprocessor is not
• - The microprocessor is assigned an analog-digital converter, the the outputs of the current sensor and the voltage sensor open are switched
• - The microprocessor in parallel connection at least two switches for the position-independent operation of the hand tool are,
• - the switches can be blocked after the blocking time has expired,  
• - The microprocessor a signal device for displaying the Operating status of the hand tool is assigned,
• - The signal device is designed as a flashing multi-color display is
• - The microprocessor at least one data memory for the operation history of the hand tool is assigned,
• - The microprocessor has an interface for querying the operation history is associated,
• - The microprocessor at least one maintenance counter for the spoke Maintenance intervals and inspection due dates assigned to the hand tool,
• An infrared transmitter is assigned to the interface, and / or, if  
• - A maximum idle time for the pump motor in the data memory and a minimum value for the motor current are stored, and if the Arrangement is made so that the pump motor out again is switched if the minimum value for the motor current is not internal half of the idle time is exceeded.

An embodiment of the subject of the invention and its function, are explained below with reference to FIGS. 1 and 2.

Show it:

Fig. 1 is a diagram of an arrangement for controlling electrohydraulic hand tools metallic for producing pipe connections through plastic deformation of pipe materials,

Fig. 2 graphs of the current profiles in 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 e.g. B. roll with spread for an interchangeable press head, not shown here, as used for the radial pressing of pipe couplings. Such a press head is disclosed in DE 44 46 504 C1.

The hand tool has a pump 5 which is arranged in a delivery line 6 between a tank 7 and the power cylinder 1, and an opening provided as a bypass return line 8 that connects the actuator cylinder 1 to the tank 7 and in a pilot-operated pressure relief valve 9 Hysteresis effect is arranged. The design and setting of the pressure relief valve 9 (spring / valve surface) must in any case be such that the valve does not open before the specified maximum pressing force is reached (safety of the press connection). The dependencies include the following: 1. The deformation resistance (depending on the pipe material, pipe pair 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 takes place in the direction that with the hand tool z. B. by exchanging the press head Rohrver connections with different diameters (z. B. from 16 to 54 mm in diameter) can be made, the design of the largest possible diameter of the pipe connection also corresponds to a safety margin. 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 press heads for tube diameters at the lower end of the above range. The pressure relief valve 9 is also assigned an emergency release lever, not shown here, with which the valve can be opened by hand at any time.

Check valves 10 and 11 are provided on both sides of the pump 5 . The hydraulic part of the arrangement is e.g. B. described in US-A-2 254 613, but 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 of which a circuit breaker 14 designed as a semiconductor switch (for example MOS) is arranged, through which the pump motor 12 is driven by a microprocessor 15 as a function of current and time becomes. In the supply line 13 of the pump motor 12 , a current sensor 16 is arranged, the output of which is connected to the microprocessor 15 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 the power switch 14 connected via a line 18 .

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 roughly 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 duty cycle of the pump motor 12 . The operating programs and setpoints for pressures and time values are also stored in this data memory, which is explained in more detail below with reference to FIG. 2.

The arrangement also has a current source 20 which is designed as a power supply unit, mains connection, but preferably as an accumulator. Between this current source 20 for the motor current and the micro processor 15 , a voltage sensor 21 for measuring the voltage of the current source 20 is arranged, and the voltage sensor 21 is switched on for control purposes the microprocessor 15 via a line 22 . The check serves, among other things, to determine the state of charge of the accumulator or the mains voltage so that malfunctions can be eliminated. If, for example, a comparison value for the voltage stored in the data memory 19 is undershot, the pump motor is immediately switched off again, since the capacity is no longer sufficient for a proper pressing process.

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

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

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

The microprocessor 15 also has internal data memories for the operating history of the hand tool and an interface 27 for querying the stored operating history via an infrared transmitter 28 . The data stores designed as counters are incremented with each work process. A total counter counts all operations since the device was manufactured. A maintenance counter is used to maintain the necessary maintenance cycles. Has this counter z. B. 10,000 operations registered, after each operation the signaling device 26 flashes five times "yellow" to indicate to the operator that an inspection is due. This state remains until the maintenance counter is reset to zero by a hand terminal via interface 27 .

All values stored in the data memories can also be read out and edited by means of the handheld terminal via the infrared transmitter 28 . This affects not only the meter readings, but also the saved parameters, which enable the entire device mechanics, including the motor and the power storage, to be adapted to the electronics. After charging the device, it works fully automatically.

Fig. 2 now shows graphs of the current profiles "i" various operating conditions over time "t". By pressing one of the switches 25 , the pump motor is switched on via the power switch 14 at time t1. In this case, a corresponding starting _current i _anl immediately _arises , which drops rapidly to an idling _current i _empty , which is represented by the curve section K1. The time period Δt between t1 and t2 is stored as a blocking time and is, for example, 400 ms. If the switch is pressed for less than Δt, the motor is switched off again immediately to prevent accidental operations from initiating a work process.

Furthermore, by briefly pressing one of the switches 25, it is possible to initiate the infrared query without having to carry out an operation. Beyond t2, switches 25 are blocked; so they can be released. By storing a further blocking time of a similar duration, the electronics can be prevented from detecting and storing the starting current peak.

Then the voltage of the accumulator (as current source 20 ) is measured. A five red flashing of the signaling device 26 is a sign that the accumulator is discharged. The engine idling current i _empty is measured once and stored. This value is used to detect the actuation of the (not shown) emergency release lever.

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 increase by a likewise stored difference, the motor is switched off again, and the signal device 26 shows a faulty operation by five orange flashes, for example that a machine defect is present or no implement, e.g. a press head, or that the emergency release lever was actuated immediately after starting.

If the motor current continues to rise, the work process is continued, that is to say in the case of a pressing process the press jaws close as the motor current increases further. After the press jaws rest on the workpiece, a metal pipe or a pipe coupling, the actual pressing process begins, whereby the current strength increases significantly. This is shown in Fig. 2 by the curve section K2. The current consumption i _max at time t4 is predetermined by the previously described force-dependent opening of the pressure relief valve 9 .

From a limit current stored in the data memory 19 , the response of the pressure relief valve 9 occurring at the time t4 and thus the decrease in the current in the curve section K3 is no longer interpreted as actuation of the EMERGENCY triggering, but rather as a proper opening of the valve after a successfully completed work process, for example at 12 to 18 A motor current has ended.

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

If the EMERGENCY triggering is initiated by manually opening the pressure relief valve 9 during a working process at time t3 below the above limit current, the current drops in accordance with the curve section K6, and the pump motor 12 is switched off when the stored idle current plus a safety margin is undershot. In this case too, the signal device 26 flashes five times "orange" to indicate this process.

Fig. 2 is still the following: if the pump motor after opening of the relief valve 9 beyond continue from t5, so although the motor current corresponding to the dotted curve section decreases K4 further, but only relatively slowly, by the efficiency of the pump 5 and the flow resistances depending is. By switching off the motor at time t5, however, the motor current drops steeply in accordance with curve section K5, and working piston 2 is now automatically pushed back much faster into its starting position under the action of return spring 3 , the displaced oil quantity being returned to tank 7 is promoted and then the valve closes again.

However, in order not to keep the pump motor running 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.

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

; Times
Δt time period, blocking time
K pressing force
K1, K2, K3, K4, K5, K6 curve sections
P hydraulic pressure

Claims (15)

1.A method for the automatic control of electro-hydraulic hand tools, in particular when producing pipe connections by plastic deformation of pipe materials, the hand tool having a drive cylinder ( 1 ) with a one-sided working piston ( 2 ), which is relieved of pressure by a return spring ( 3 ) is pushed back into its initial position, and for the drive of the drive cylinder ( 1 ) a pump ( 5 ) fed from a tank ( 7 ) and for the backflow of the hydraulic fluid speed to the tank ( 7 ) has a return flow line ( 8 ) in a pilot-operated pressure relief valve ( 9 ) with a hysteresis effect is arranged, the pump ( 5 ) being driven by an electric pump motor ( 12 ), in the supply line ( 13 ) of which a power switch ( 14 ) is arranged, characterized in that the pump motor ( 12 ) is controlled in a current-dependent manner by a microprocessor ( 15 ) that the Stro Recording of the pump motor ( 12 ) and the current drop after opening the pressure relief valve ( 9 ) are detected by the microprocessor ( 15 ) and that the motor current is interrupted by the circuit breaker ( 14 ) after falling below a stored current value (i _stop ). 2. The method according to claim 1, characterized in that the initiation of the operation is delayed by a stored blocking time (Δt) and that the entire duty cycle of the motor current is limited by a stored maximum time value (t _max ). 3. Arrangement for the automatic control of electro-hydraulic hand tools, in particular for the production of Rohrverbindun conditions by plastic deformation of pipe materials, with a drive cylinder ( 1 ) with a one-sided working piston ( 2 ), which is acted upon by a return spring ( 3 ) and one Piston rod ( 4 ), with a pump ( 5 ), which is arranged in a delivery line ( 6 ) between a tank ( 7 ) and the drive cylinder ( 1 ), with a return flow line ( 8 ) which drives the drive cylinder ( 1 ) connects to the tank ( 7 ) and in which a pilot-operated pressure relief valve ( 9 ) with hysteresis effect is arranged, and with an electric pump motor ( 12 ), in whose supply line ( 13 ) a circuit breaker ( 14 ) is arranged, characterized in that the pump motor ( 5 ) can be controlled in a current-dependent manner by a microprocessor ( 15 ) to which at least one manually operable switch ( 25 ) is assigned, wherein

• a) a current sensor ( 16 ) is arranged in the electrical supply line ( 13 ) of the pump motor ( 12 ), the output of which is connected to the microprocessor ( 15 ) for comparison with at least one stored setpoint for the motor current,
• b) the output of the microprocessor ( 15 ) is connected to the circuit breaker ( 14 ) in the supply line ( 13 ), and wherein
• c) the microprocessor ( 15 ) is assigned at least one data memory ( 19 ) in which memory locations are arranged, namely:
  • 1. for a period of time Δt as a blocking time for a possible incorrect operation,
  • 2. for a maximum period of time t _max for switching off in the event of a malfunction of the device after actuation of at least one switch ( 25 ) and
  • 3. for at least one limit current value (i _stop ) for switching off the motor current, which limit current value (i _stop ) is lower than a limit current value (i _max ) when the pressure relief valve is opened.

4. Arrangement according to claim 3, characterized in that between a current source ( 20 ) for the motor current, a voltage sensor ( 21 ) for measuring the voltage of the current source ( 20 ) is arranged and that the voltage sensor ( 21 ) is connected to the microprocessor ( 15 ) is. 5. Arrangement according to claim 4, characterized in that between the voltage sensor ( 21 ) and the microprocessor ( 15 ), a voltage regulator ( 23 ) for the operating voltage of the microprocessor ( 15 ) is arranged. 6. Arrangement according to one of claims 3 or 4, characterized in that the microprocessor ( 15 ) is assigned an analog-digital converter ( 24 ) to which the outputs of the current sensor ( 16 ) and the voltage sensor ( 21 ) are connected. 7. Arrangement according to claim 3, characterized in that the microprocessor ( 15 ) are connected in parallel to at least two switches ( 25 ) for the position-independent operation of the hand tool. 8. Arrangement according to claim 7, characterized in that the switches ( 25 ) can be blocked after the blocking time (Δt). 9. Arrangement according to at least one of claims 3 to 8, characterized in that the microprocessor ( 15 ) is assigned a signal device ( 26 ) for displaying the operating state of the hand tool. 10. The arrangement according to claim 9, characterized in that the signal device ( 26 ) is formed as a flashing multi-color display. 11. The arrangement according to claim 3, characterized in that the microprocessor ( 15 ) is assigned at least one data memory for the operating history of the hand tool. 12. The arrangement according to claim 3, characterized in that the microprocessor ( 15 ) is assigned at least one maintenance counter for the storage and display of maintenance intervals and inspection due dates of the hand tool. 13. The arrangement according to claim 11, characterized in that the microprocessor ( 15 ) is assigned an interface ( 27 ) for querying the operating history. 14. Arrangement according to claim 13, characterized in that the interface ( 27 ) is associated with an infrared transmitter ( 28 ). 15. The arrangement according to claim 3, characterized in that a maximum idle time for the pump motor ( 12 ) and a minimum value for the motor current are stored in the data memory ( 19 ), and that the arrangement is such that the pump motor ( 12 ) again is switched off if the minimum value for the motor current is not exceeded within the idle time.