Hydraulic drive for a drilling device and method for operating a hydraulic drive

Abstract

Hydraulic drive for a drilling device, in particular a horizontal drilling machine, wherein a hydraulic motor (30) is provided, by means of which a drill (31) can be driven, wherein the hydraulic motor (30) is connected via a first and a second working line (21;22) is connected in a closed hydraulic circuit (20) to a main pump (40), wherein the main pump (40) has a continuously adjustable displacement volume which can be adjusted by means of an actuating cylinder (42), wherein the actuating cylinder (42) is connected to a control valve (50), wherein the control valve (50) has a first inlet connection (51) and a first return connection (52), characterized in that the first inlet connection (51) of the control valve (50) is connected to an outlet connection (61) of a pressure reducing valve (60), so that the pressure at the inlet connection (51) can be adjusted to a predetermined target pressure (62) by means of the pressure reducing valve (60), wherein an electronic control device (13) of the hydraulic drive is configured to set the said target pressure (62) as a function of a desired high pressure in the closed circuit (20);

Description

[0001] The invention relates to a hydraulic drive according to the preamble of claim 1 and a method for its operation.

[0002] The hydraulic drive is primarily intended for use with a horizontal drilling machine.

[0003] Furthermore, the data sheet "Axial Piston Variable Displacement Pump A4VG Series 40" RD92004 dated March 30, 2020, describes an axial piston pump in swash plate design with a continuously adjustable displacement. This pump is intended for use in a closed hydraulic circuit. Fig. The control valve shown in Figure 1 of this application is discussed in the aforementioned data sheet in the chapter "EP - Electric Proportional Control." It enables the speed of the hydraulic motor connected to the pump in a closed hydraulic circuit to be controlled proportionally to a control signal. The corresponding torque, however, cannot be influenced.

[0004] An advantage of the present invention is that the torque of the hydraulic motor can be specifically adjusted depending on the operating state of the hydraulic drive. In the case of a horizontal drilling machine, this particularly applies to the operating states of advancing the drill bit and changing the drill bit or a single part of the drill rod.

[0005] According to claim 1, it is proposed that the first inlet connection of the control valve is connected to an outlet connection of a pressure reducing valve, so that by means of the pressure reducing valve the pressure at the inlet connection can be regulated to a predetermined target pressure, wherein the said target pressure can be adjusted depending on a desired high pressure in the closed circuit.

[0006] The control valve preferably has a first and a second working port, each of which is connected to one of two opposing actuating chambers of the actuating cylinder. The hydraulic motor preferably has a constant displacement volume, so that the torque depends essentially solely on the aforementioned high pressure. The hydraulic drive is preferably operated with a pressurized fluid in the form of a liquid, most preferably hydraulic oil. The high pressure is understood to be the higher of the two pressures in the first and second working lines.

[0007] Advantageous further developments and improvements of the invention are specified in the dependent claims.

[0008] The pressure reducing valve can be mounted directly onto the control valve. This eliminates the need for pipes or hoses between the control valve and the pressure reducing valve.

[0009] The control valve can be configured such that the displacement volume of the main pump is regulated substantially proportionally to an associated control signal. The control signal can be an electrical or hydraulic signal. It is understood that this control is only fully effective if a sufficiently high pressure is provided at the first inlet connection by the pressure reducing valve according to the invention.

[0010] It may be provided that the pressure reducing valve is supplied with pressurized fluid from a separate auxiliary pump. The auxiliary pump is, for example, an external gear pump. The auxiliary pump is preferably operated in an open hydraulic circuit, drawing the pressurized fluid from a tank. It is conceivable to use the high pressure of the closed hydraulic circuit of the main pump to supply the pressure relief valve.

[0011] It can be provided that the first return connection of the control valve and / or a second return connection of the pressure reducing valve are connected to a tank.

[0012] It can be provided that the high pressure is determined by means of a shuttle valve, which is connected on the inlet side to the first and second working lines of the closed hydraulic circuit. During the advance of the drill bit and during the release of the drill bit or the individual parts of the drill rod, the high pressure is applied to a different working line because the direction of rotation of the hydraulic motor is opposite in these operating states. The high pressure is applied on the outlet side to the shuttle valve, regardless of the operating state of the hydraulic drive. The high pressure is preferably measured using a pressure sensor.

[0013] The displacement volume of the main pump can be adjusted in such a way that the pumping direction of the main pump can be reversed simply by adjusting the displacement volume while maintaining the same drive rotation direction. This allows an internal combustion engine, particularly a diesel engine, whose rotation direction cannot be easily reversed to serve as the drive motor.

[0014] It may be provided that the target pressure of the pressure reducing valve is electrically adjustable. The target pressure is preferably set by means of an electromagnet, which most preferably adjusts the preload of a spring that acts on a control spool of the pressure reducing valve.

[0015] A control loop can be provided whose actual variable is the measured high pressure, and whose manipulated variable is the setpoint pressure of the pressure reducing valve, and whose setpoint variable is the desired high pressure. Said actual variable is preferably measured with a pressure sensor. Said control loop preferably comprises a continuous, linear controller, which is most preferably implemented in a time-discrete manner.

[0016] The controller is, for example, a P or PI controller. It is most preferably implemented by a control device comprising a digital computer.

[0017] Protection is also claimed for a method for operating a hydraulic drive according to the invention, wherein when changing the drill bit and when advancing the drill bit, different high pressures are set by adjusting the target pressure of the pressure reducing valve. In a horizontal device, a drill rod is typically used which is composed of several individual parts that are screwed together. The screw connection is designed such that it is tightened during advancement. When changing an individual part of the drill rod, the drill bit is driven in the opposite direction of rotation to that of advancement, wherein a higher torque is typically required to loosen said screw connection than during advancement. Accordingly, a higher high pressure is preferably set when changing the drill bit than when advancing the drill bit.

[0018] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0019] The invention is explained in more detail below with reference to the accompanying drawing. It shows: Fig. 1 a circuit diagram of a hydraulic drive according to the invention.

[0020] Fig. Figure 1 shows a circuit diagram of a hydraulic drive according to the invention. The hydraulic drive serves to drive a drill 31, which is used, for example, in a horizontal drilling machine. The drill 31 is designed, for example, as a drill rod composed of several individual parts that are screwed together. As the drill 31 advances, it is gradually supplemented with such individual parts to extend the bore.

[0021] The borehole is used, for example, to route electrical cables under an existing road.

[0022] The hydraulic drive comprises a main pump 40 and a hydraulic motor 30, which are connected via a first and a second working line 21; 22 in a closed hydraulic circuit 20. The closed hydraulic circuit 20 is in Fig. 1 is greatly simplified, with details not necessary for understanding the invention being omitted. These details include, for example, the protection against overpressure and the flushing to prevent overheating of the pressurized fluid. The hydraulic drive is operated with a pressurized fluid, which is preferably a liquid and most preferably hydraulic oil.

[0023] The main pump 40 has a continuously adjustable displacement volume. It is preferably designed as an axial piston pump with a swashplate design. The pivot angle of the corresponding swashplate is adjusted by means of an actuating cylinder 42 to adjust the displacement volume. The main pump 40 is adjustable beyond zero displacement, so that the delivery direction can be reversed simply by adjusting the displacement volume or the swashplate, without reversing the direction of rotation of the drive motor 41. In a horizontal drilling machine, the drive motor 41 is usually designed as an internal combustion engine, particularly a diesel engine.

[0024] The hydraulic motor 30 preferably has a constant displacement volume, so that its torque depends essentially solely on the high pressure 23 of the closed hydraulic circuit 20. The hydraulic motor 30 is designed, for example, as an axial piston motor with a bent-axis design.

[0025] The actuating cylinder 42 is designed as a double-acting cylinder with two actuating chambers 45 that adjust the displacement volume in opposite directions. The two actuating chambers 45 are each connected to a first and a second actuating connection 53; 54 of the control valve 50. The control valve 50 is designed as a continuously adjustable 4 / 3-way valve. The middle switching position symbolizes a positive zero overlap, in which the first inlet connection 51 and the first return connection 52 are each connected to the first and second actuating connections 53; 54 via a very small opening cross-section. This results in favorable control behavior of the control valve 50.

[0026] The control valve 50 implements a control system in which the displacement volume of the main pump 40 is adjusted essentially proportionally to a control signal 44. In this case, the control signal 44 is specified by two electromagnets that act in opposite directions on the control spool of the control valve 50. The position of the actuating cylinder 42 is fed back to the control spool via a (symbolically represented) position feedback 46 via springs 47. The position of the actuating cylinder 42 is proportional to the force exerted by the springs 47 on the control spool. When the control spool is in force equilibrium, the displacement volume is adjusted to the value specified by the control signal 44.

[0027] Typically, the first inlet connection 51 of such a control valve 50 is connected to a defined high pressure. According to the invention, the first inlet connection 51 is connected to a pressure reducing valve 60, in particular to its outlet connection 61. The higher of the two pressures at the first or second control connection 53; 54 cannot rise above the pressure at the first inlet connection 51. At the same time, a control pressure is required to adjust the displacement volume, which depends on the high pressure 23 in the first or second working line 21; 22. If this required control pressure is not present at the first inlet connection 51, the displacement volume of the main pump 40 decreases, causing the high pressure 23 to drop. The high pressure 23 is understood to mean the higher of the two pressures in the first or second working line 21; 22. The high pressure 23 is determined in this case using a shuttle valve 24.

[0028] According to the above explanations, the high pressure 23 can therefore be influenced by the pressure reducing valve 60. It is understood that the control function of the control valve 50 is thereby disrupted, whereby the displacement volume of the main pump 40 is no longer necessarily proportional to the control signal 44. This is only the case if the pressure reducing valve 60 provides a sufficiently high pressure at the first inlet connection 51.

[0029] Since the relationship between the pressure at the first inlet connection 51 and the high pressure 23 is subject to a variety of influences, the high pressure 23 is measured using the pressure sensor 25. An electronic control device 13 then adjusts the target pressure 62 of the pressure reducing valve 60 such that the measured high pressure 23 equals a desired high pressure. The desired high pressure is selected depending on the operating state of the drilling device. During advancement of the drill bit, the desired high pressure is typically somewhat lower than when replacing an individual part of the drill rod. This takes into account the fact that the screw connections of the drill rod are tightened during advancement, so that an increased torque is required to loosen the screw connection.

[0030] The pressure reducing valve 60 is supplied with pressurized fluid by an auxiliary pump 12. The auxiliary pump 12 draws pressurized fluid from a tank 11 and delivers it to a second inlet connection of the pressure reducing valve 60. A second return connection of the pressure reducing valve 60 is connected to the tank 11. All tank symbols in Fig. 1 denote the same tank 11. The first return port 52 of the control valve 50 is also connected to the tank 11.

[0031] The control device 13 preferably comprises a programmable digital computer. Reference symbol 11 Tank 12 Auxiliary pump 13 Control device 20 closed circuit 21 first work line 22 second working line 23 High pressure 24 shuttle valve 25 Pressure sensor 30 hydraulic motor 31 drills 40 Main pump 41 Drive motor 42 actuating cylinders 44 Control signal 45 Control chamber 46 Path feedback 47 spring 50 control valve 51 first inlet connection 52 first return connection 53 first control connection 54 second control connection 60 pressure reducing valve 61 Output connector 62 Target pressure 63 second inlet connection 64 second return connection

Claims

[1] Hydraulic drive for a drilling device, in particular a horizontal drilling machine, wherein a hydraulic motor (30) is provided, by means of which a drill (31) can be driven, wherein the hydraulic motor (30) is connected to a main pump (40) via a first and a second working line (21; 22) in a closed hydraulic circuit (20), wherein the main pump (40) has a continuously adjustable displacement volume which is adjustable by means of an actuating cylinder (42), wherein the actuating cylinder (42) is connected to a control valve (50), wherein the control valve (50) has a first inlet connection (51) and a first return connection (52), characterized bythat the first inlet connection (51) of the control valve (50) is connected to an outlet connection (61) of a pressure reducing valve (60), so that by means of the pressure reducing valve (60) the pressure at the inlet connection (51) can be regulated to a predetermined target pressure (62), wherein an electronic control device (13) of the hydraulic drive is configured to set the said target pressure (62) depending on a desired high pressure in the closed circuit (20). [2] Hydraulic drive according to claim 1, wherein the pressure reducing valve (60) is mounted directly on the control valve (50). [3] Hydraulic drive according to one of the preceding claims, wherein the control valve (50) is designed such that the displacement volume of the main pump (40) is regulated substantially proportionally to an associated control signal (44). [4] Hydraulic drive according to one of the preceding claims, wherein the pressure reducing valve (60) is supplied with pressurized fluid by a separate auxiliary pump (12). [5] Hydraulic drive according to one of the preceding claims, wherein the first return connection (52) of the control valve (50) and / or a second return connection (64) of the pressure reducing valve (60) are connected to a tank (11). [6] Hydraulic drive according to one of the preceding claims, wherein the high pressure (23) is determined by means of a shuttle valve (24) which is connected on the input side to the first and second working lines (21; 22) of the closed hydraulic circuit (20). [7] Hydraulic drive according to one of the preceding claims, wherein the displacement volume of the main pump (40) is adjustable such that the delivery direction of the main pump (40) can be reversed with the drive rotation direction remaining the same solely by adjusting the displacement volume. [8] Hydraulic drive according to one of the preceding claims, wherein the target pressure (62) of the pressure reducing valve (60) is electrically adjustable. [9] Hydraulic drive according to one of the preceding claims, wherein a control circuit is provided, the actual value of which is the measured high pressure (23), the control value of which is the setpoint pressure (62) of the pressure reducing valve (60), the setpoint value of which is the desired high pressure. [10] Method for operating a hydraulic drive according to one of the preceding claims, wherein when changing the drill (31) and when advancing the drill (31), different high pressures (23) are set by adjusting the target pressure (62) of the pressure reducing valve (60).

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