EP2022990B1 - Machine tool and supply unit - Google Patents

Description

The invention relates to a machine tool according to the preamble of patent claim 1.

In the hydraulic control system according to US 4,819,430 A are provided in the supply unit a fixed displacement pump and a control pump. The constant pump feeds a secondary circuit, while the control pump is the primary pressure source for a priority circuit with a pressure accumulator. Control pumps are expensive and have a relatively sluggish response.

In a machine tool with electro-hydraulic control device according to EP 1 350 033 A For working cycles of the working hydraulics in the supply unit, a permanently running electric motor drives the first and second constant pumps in the supply unit, the first fixed displacement pump with lower flow feeding a leaking circuit with a pressure accumulator, while the second fixed displacement pump with the higher flow rating only covers this circuit to cover a peak load feeds oil through an oil cooler for the remainder of the time. Since the delivery rates of the two constant-flow pumps are in a ratio of at least 1: 2, the performance characteristics of the pump drive motor are optimized approximately to the total delivery rate. Predominantly, the second constant-displacement pump delivers power only in the oil cooler, so then the optimization of the performance characteristics of the pump drive motor does not fit, the pump drive motor runs with poor efficiency and possibly generates additional heat that must be removed from the oil in the oil cooler. This can cause a relatively large oil cooler. While the second constant-displacement pump leads the oil through the oil cooler, a valve that can be switched by the pressure in the pressure accumulator against spring force directs the flow to the oil cooler.

Out US 4,449,365 A is a hydraulic forklift control system with two own motors having pumps known. In one embodiment, both motors are only switched on when needed by the driver. In another embodiment, the engine of the first pump for priority actuation of a steering during operation of the forklift runs permanently, while the second motor for operating lifting and tilting cylinders is only switched on by the driver when a lifting cylinder is to be controlled in overdrive. A manual multi-way multi-position control valve will for this purpose, the switching position for the lifting cylinder overdrive adjusted and closes the circuit of the second motor.

Out US 4 635 439 A is a forklift control with two own motors having constant displacement pumps known. The speed of the first motor is variable while the speed of the second motor is fixed. The capacity of the first pump is greater than the capacity of the second pump. The control valve for a main consumer has as signal generator a valve lift sensing device with a potentiometer to turn on the second motor depending on the strength of the signal. When the second motor is turned on, the speed of the first motor is correlated with the acceleration of the second motor temporarily reduced. The discharge reduction of the first pump is compensated with the delivery of the second pump, while the rotational speed of the first motor is raised again.

The invention has for its object to provide a machine tool, which makes it possible to use in the electro-hydraulic control device electrical primary energy with good efficiency and to generate little heat on the motor side.

The stated object is achieved with the features of claim 1.

The first pump drive motor runs permanently in working cycles of the machine's working hydraulics and covers the basic hydraulic load via the first constant pump, whereby it is operated with optimum performance characteristics because load changes to the first constant-flow pump have no influence. The second pump drive motor for the second fixed displacement pump is operated with peak load optimized performance. Thus, with both pump drive motors, electric primary energy is optimally utilized, and little additional heat is generated on the motor side due to unfavorable engine efficiencies, so that, if any, a cooling device of only moderate design is needed. The second pump drive motor is turned on in shutdown mode and to cover the peak load. If no peak load is called, then there is the second pump drive motor. If the second pump drive motor is switched on, the full delivery capacity for covering the peak load is immediately available. The system pressure in the work hydraulics is monitored by a pressure switch which can provide a signal to turn on the second pump drive motor operating in shutdown mode as soon as a certain pressure drop occurs. This pressure drop usually sets in when provided for the working hydraulics or another hydraulic consumer Directional valve is switched. Alternatively, the machine tool has a program control in which the work cycles of the work hydraulics are programmed, and thus informed when there is a need for a peak load. The program controller may then turn the second pump drive motor on and off, with either on-demand or eventually even on-demand switching on.

In another alternative embodiment, the output of the second constant-displacement pump is fed to the hydraulic consumers via the load-sensing signal-providing pressure switch and a solenoid operated by either for peak load or to an oil cooler. If neither a peak load to cover nor the temperature of the oil is too high, then is the second pump drive motor, thus saving primary energy.

In one embodiment, in addition, a third constant displacement pump driven by the first pump drive motor is provided, which conveys exclusively into an oil cooler. The third constant-flow pump has a higher flow rate than the first constant-flow pump. In this case, the first pump drive motor is optimized in terms of performance with respect to the substantially constant sum of both flow rates, so that he needs to come with no power fluctuations right to work and with low efficiency.

In another embodiment, the supply unit as an oil reservoir on a finned tube housing, on which, preferably, at least one cooling fan is arranged. Since the drive motors are operated optimized performance and therefore generate relatively little additional heat, the cooling of the finned tube housing can be sufficient even when the first pump drive motor runs in continuous operation. However, if desired, the cooling fan may also be combined with an oil cooler fed by the second or third constant displacement pump. The supply unit contains the first and second pump drive motors in a common oil reservoir and in the form of sub-oil electric motors, which are cooled by the oil in the reservoir, take up little space, and are very reliable.

The delivery rates of the first and second constant-flow pumps or the first and third constant-flow pumps are expediently each in a ratio of less than 1: 2.

A pressure limiting valve, set to a predetermined oil cooler load, between the third constant displacement pump and the oil cooler ensures that the first pump drive motor is hardly exposed to load changes by the third constant pump and can be operated with optimum efficiency.

The two constant pumps are useful gear pumps, but could also be piston pumps or the like.

Fig. 1

ein Blockschaltbild einer Hydrauliksteuerung mit einem Versorgungsaggregat in einer Werkzeugmaschine,

Fig. 2

eine Ausführungsform eines Doppelmotor-Versorgungsaggregats in einem Längsschnitt,

Fig. 3

eine weitere Ausführungsform der Hydrauliksteuerung, und

Fig. 4

eine weitere Ausführungsform der Hydrauliksteuerung.

Embodiments of the subject invention will be explained with reference to the drawings. Show it:

Fig. 1

1 is a block diagram of a hydraulic control with a supply unit in a machine tool;

Fig. 2

an embodiment of a twin-motor supply unit in a longitudinal section,

Fig. 3

another embodiment of the hydraulic control, and

Fig. 4

another embodiment of the hydraulic control.

In the block diagram in Fig. 1 is a hydraulic control S, for example, a machine tool M indicated schematically, in which a working line 27 not shown

Hydro consumers, for example, a working hydraulics or tensioning device connected (eg via directional valves, not shown), and to a working line 28 any other, not shown, hydraulic consumers. The control device S is supplied hydraulically from a supply unit A, for example a supply unit A according to FIG Fig. 2 ,

During operation of the machine tool M, for example, a basic hydraulic load is fed in via the working line 27, which optionally compensates for leakage losses that vary as a function of the temperature. About the working line 28 is also case by case for hydraulic consumers with currently strong consumption a peak hydraulic load fed. The base load is permanently required, while the peak load is needed only for a relatively short time and / or at certain time intervals, e.g. Depending on certain workflows in the machine tool M. It can also be included in the hydraulic working on the working line 27 hydraulic consumers, such as clamping cylinders that need a peak load for a short time.

The machine tool M has, for example, a schematically indicated program control CU, by which the working hydraulics or the hydraulic consumers are controlled. In the supply unit A, a first electric pump drive motor M1 for a first fixed displacement pump P1 having a specific delivery rate Q1 and a second pumping drive motor M2 for a second fixed displacement pump P2 having a second predetermined delivery rate Q2 are arranged in one and the same oil reservoir R. The first constant-displacement pump P1 is used to cover the base load and to at least temporarily maintain the pressure of a pressure accumulator 31. The second constant-displacement pump P2, however, serves to temporarily cover the peak load. (The base load and the peak load are not constant loads but may vary.) An essential feature of the peak load is a transient higher delivery rate than the base load.)

The first constant-displacement pump P1 is connected to the pressure accumulator 31 and the working line 27 via a supply line 29 and a check valve 30 which blocks the reservoir R. At a node 36, a line 32 branches off to the reservoir R, in which a first pressure relief valve 33 is included. Between the check valve 30 and the node 36 branches off from the pressure line 29 from a line 34 to the reservoir R, in which a second pressure relief valve 35 is included. The two pressure limiting valves 33, 35 are set to different response pressures, for example to 100 bar and 140 bar.

The second constant pump P2 is connected via a supply line 38 and a check valve 39 to a node 37 of the supply line 29, and also to an electrical pressure switch 40. The pressure switch 40 is used when a certain pressure drop occurs the second pump drive motor M2 either for a programmed period of time or switch on so long that the peak load covered and / or the target pressure of the pressure accumulator 31 are reached again. If necessary, the pressure switch 40 switches off the second pump drive motor M2 again.

In an alternative, not shown, the function of the pressure switch 40 could also be taken over by the program control CU of the machine tool M, that is to say that the program control CU turns on the second pump drive motor M2 if and as long as a hydraulic peak load is to be covered depending on the program

Since heat is generated in the system and also by the pump drive motors M1, M2, the supply unit A may have a cooling fan 41, which is driven by the permanently running first pump drive motor M1, or (not shown), by its own electric fan drive motor. As long as only the base load is to be covered during operation of the machine tool, this is done via the first constant-displacement pump P1 with the delivery rate Q1. In this case, the pressure accumulator 31 is charged. The second pump drive motor M2 is stationary. The pressure switch 40 and the program control CU provide no turn-on signal for the second pump drive motor. If, for example, the peak load is called up via the working line 27 or, for example, a directional valve for one or more hydraulic consumers connected to the working line 28, at least between the node 37 and the check valve 39, a pressure drop occurs, which the pressure switch 40 issues with a signal for switching on second pump drive motor M2 acknowledged. The second constant displacement pump P2 covers the peak load and also maintains or brings the pressure in the accumulator 31 to the setpoint, for example, determined by the set to the lower response pressure relief valve 35. Once the peak load is no longer needed, generated at a pressure increase, the pressure switch 40, the signal for switching off the second pump drive motor M2, so that then again only the first pump drive motor M1 is operated.

Since the power consumption of the first pump drive motor M1 hardly varies in the base load, the first pump drive motor M1 can be operated with optimized in terms of base load performance. The same applies to the second pump drive motor M2, which is operated only to cover a peak load and then hardly load fluctuations is exposed, so that the second pump drive motor M2 is operated with optimized in terms of peak load performance characteristics. Both pump drive motors M1, M2 and their constant pumps P1, P2 operate with optimal efficiencies. They can be small and inexpensive.

The supply unit A in Fig. 2 has as a common oil reservoir R for the first and second pump drive motors M1, M2 and the first and second fixed displacement pump P1, P2 a finned tube housing G of a finned tube 1 with at least outer fins 2 and end caps 3, 4. As a cooling fan 41, a fan 5 is mounted on the lid 4, which in the embodiment shown in Fig. 2 is not driven by the first pump drive motor M1, but by a separate drive motor 6, for example, to achieve a higher fan speed than the speed of the first pump drive motor M1. In an alternative not shown, however, the first pump drive motor M1 could also drive the fan 5.

On one side of the finned tube 1 feet 7 are provided, which indicate the operating position of the supply unit A (lying).

In correspondingly strong cover 3 flow paths 8 are formed, while the lid 4, for example, a casting in thin-walled training. On the cover 3, a connection surface 10 for control, monitoring, control components 9 of the supply unit A is also provided on the outside. A vent or vent hole 8 for the reservoir R may also be provided, so that the oil in the reservoir R is stored substantially without pressure. The first pump drive motor M1 drives in Fig. 2 Not only the first constant pump P1, but possibly also a third constant pump P3. The constant pumps P1, P3 are connected in series and differ for example in their flow rates (Q1, Q3). Appropriately, it is gear pumps.

The first and second pump drive motors M1, M2 are open sub-oil electric motors which are cooled by the oil in the reservoir R.

The first pump drive motor M1 has a stator part 12 which is pressed into a retaining collar 13 of the cover 4. A rotor shaft 15 of a rotor 14 has bearings 16, 20 in a bearing collar 17 of the cover 4 and in a bearing plate 19 between the stator 12 and the third constant pump P3. The constant-displacement pumps P1, P3 are fastened freely cantilevered on the stator part 12 with fastening devices 18. The axis of the first pump drive motor M1 and the first and third constant pumps P1, P3 in this embodiment is approximately parallel to the axis of the finned tube 1 or even in accordance with the axis of the finned tube 1.

The second pump drive motor M2 has a stator part 21 which is fixed with an end face in an annular recess 23 of the lid 3 by means of a sleeve 22. A bearing collar 24 of the lid 3 supports a bearing 25 a rotor 27 of the second pump drive motor M2. A second rotor shaft bearing 27 'is contained in a bearing plate 26 between the stator 21 and the second constant pump P2. The second constant pump P2 is free auskraund the second constant pump P2 included. The second constant displacement pump P2 is freely cantilevered by means of fasteners 28 arranged on the stator 21. The axis of the second pump drive motor M2 and the second constant pump P2 is also substantially parallel to the axis of the finned tube 1, but is offset from the axis of the first pump drive motor M1. The fan drive motor 6 can either run in continuous operation, or be turned on as needed depending on the temperature.

The hydraulic control device S of the machine tool M in Fig. 3 is different from that of Fig. 1 in that the first pump drive motor M1 permanently additionally drives a third constant-displacement pump P3 with a delivery rate Q3. The third constant pump P3 (see Fig. 2 ) is connected via a supply line 42 to an oil cooler KV. From the supply line 42 branches off a line 43 to the reservoir R, in which a pressure relief valve 44 is included. The pressure relief valve 44 is set, for example, to a radiator pressure of only 15 bar.

The in Fig. 1 indicated cooling fan 41 could also be provided in this embodiment, but may not be necessary because of the oil cooler KV. The oil cooler KV is disposed outside the reservoir R. For example, the ratio between the flow rate Q1 of the first constant displacement pump P1 and the flow rate Q3 of the third constant displacement pump P3 and Q1 and the displacement Q2 of the second constant displacement pump P2 is smaller than 1: 2, respectively Fig. 1 ,

In the embodiment of the control device S in Fig. 4 are included in the supply unit A only the first and second constant pumps P1 and P2, wherein the second pump drive motor P2 is operated either in the shutdown mode or permanently. In the shutdown mode, the turn-on time of the second pump drive motor M2 depends on the respective peak load and the need for cooling the oil, ie, the second pump drive motor M2 can then remain off if neither a peak load is requested nor cooling is required. When continuous operation of the second pump drive motor M2, however, the peak load is covered, if necessary, and otherwise passed the delivery of the second constant pump P2 through the oil cooler KV. In the supply line 38 is in Fig. 4 instead of the check valve 39 of Fig. 3 a solenoid switching valve 45 included (as shown by a spring 46) assumes a passage position to the oil cooler KV, and a branch line 34 'to the supply line 29 shuts off or upon actuation of a solenoid 47, the supply line 38 via the branch line 34' with the supply line 29 downstream the check valve 30 connects, and the connection to the oil cooler KV interrupts. The switching valve 45 is connected to the pressure switch 40 via a signal line 48, for example, so that the pressure switch 40 switches the switching valve 45 accordingly upon occurrence of a peak load request (pressure drop). Alternatively, the in Fig. 4 not shown program control of the machine tool, the control valve 45 program dependent even leading to the pressure drop trigger. In this case, the pressure switch 40 could be omitted.

Because in the Fig. 3 and 4 The first pump drive motor is not subject to significant load fluctuations, it can be operated with optimized performance and favorable efficiency. This also applies to the second pump drive motor M2 in Fig. 3 which is turned on only upon request of a peak load. The second pump drive motor M2 in Fig. 4 can also be operated with optimized performance and efficiency both in shutdown mode and in continuous operation, since the load difference between the peak load and the load of the oil cooler KV is not significant. Suitably, the performance of the second pump drive motor M2 is tuned to the peak load, especially when the second pump drive motor M2 is running in shutdown mode. Alternatively, it is possible to tune the second pump drive motor M2 in its performance characteristics to the needs of the oil cooler KV, since the peak load is obtained comparatively rarely.

Claims (7)

1. Machine tool (M), comprising a working hydraulics the hydroconsumers of which are operated during working cycles permanently with hydraulic basic load and temporarily with hydraulic peak loads, an electrohydraulic control device (S), and a supply unit (A), the supply unit (A) including at least first and second constant discharge pumps (P1, P2) of different discharge quantities (Q1, Q2) within an oil reservoir (R), of which first and second constant discharge pumps (P1, P2) the first one having the lower discharge quantity (Q1) is covering the basic load and the second having the higher discharge quantity (Q2) is covering the peak load, and at least a first pump driving motor (M1) permanently operating during working cycles, characterized in that a second pump driving motor (M2) is provided in the supply unit (A) for the second constant discharge pump (P2), that the second pump driving motor (M2) during working cycles is operable electrically in a switch-off-operation and is switched on only for covering the peak load and is optimized in view to the peak load in its quantity characteristic, and that either in the electrohydraulic control device (S) a pressure switch (40) is associated to the first and second constant discharge pumps (P1, P2) and the hydroconsumers at least for switching on the second pump driving motor (M2) depending from load, or that the machine tool (M) comprises a program control (CU) for switching on and switching off the second pump driving motor (M2) via the program control (CU).
2. Machine tool according to claim 1, characterized in that the discharge quantity of the second constant discharge pump (P2) selectively is supplied to the hydroconsumers for covering the peak load or is supplied to an oil cooler (KV), either via the pressure switch (40) delivering an electric signal depending from load and a solenoid switching valve (45) controlled by the signal or via a solenoid switching valve (45) controlled by the program control (CU) of the machine tool (M).
3. Machine tool according to claim 1, characterized in that in addition a third constant discharge pump (P3) having higher discharge quantity (Q3) compared to the first constant discharge pump (P1) is driven by the first pump driving motor (M1) and is connected exclusively at the discharge side with an oil cooler (KV).
4. Machine tool according to claims 1 to 3, characterized in that the supply unit (A) comprises a ribbed tube housing (G) as the oil reservoir (R) and that, preferably, at least one cooling fan (41) is arranged at the ribbed tube housing (G), the cooling fan (41) being either driven directly and permanently by the first pump driving motor (M1) or having an own driving motor (6).
5. Machine tool according to at least one of the preceding claims, characterized in that the discharge quantities (Q1:Q2; Q1:Q3) of the first and second constant discharge pumps (P1, P2) or optionally of the first and third constant discharge pumps (P1, P3) respectively define a ratio smaller than 1:2.
6. Machine tool according to claim 3, characterized in that the connection between the third constant discharge pump (P3) and the oil cooler (KV) is safeguarded towards the oil reservoir (R) by a pressure limiting value (44) which, preferably, is adjusted only to about 15 bar as oil cooler load.
7. Machine tool according to at least one the preceding claims, characterized in that a pressure accumulator (31) is arranged between the first and second constant discharge pumps (P1, P2) and the hydroconsumers.

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