HYDRAULIC SYSTEM AND WORK EQUIPMENT WITH SUCH A

Description

[0001] The present invention relates to a hydraulic system according to the preamble of claim 1 and to a working device, in particular a hydraulic excavator, with such a hydraulic system.

[0002] In the hydraulic circuits of construction machinery such as hydraulic excavators, a distinction is typically made between the main hydraulics or working hydraulics (main hydraulic circuit or working hydraulic circuit), whose components are responsible for the equipment's functions, and the remaining hydraulics with the auxiliary consumers (auxiliary consumer circuit). The working hydraulics are typically operated by a variable displacement hydraulic pump and include all hydraulic components necessary for performing the work functions, i.e., operating the equipment and attachments. The auxiliary consumer circuit, on the other hand, is usually operated by several differently controlled hydraulic pumps and provides other functions necessary for the operation of the construction machine.

[0003] Given the diverse functions of auxiliary consumers, their control is often implemented differently. A fundamental distinction is made between pressure control and flow control of the connected auxiliary consumers. Due to these different control concepts, the auxiliary consumers are therefore frequently supplied by differently controlled auxiliary consumer pumps.

[0004] In particular, pressure-controlled auxiliary consumers are supplied via pressure-controlled hydraulic pumps and volume-controlled auxiliary consumers via separate volume-controlled auxiliary consumer pumps.

[0005] Many work machines typically require at least four hydraulic auxiliary consumers: hydraulic engine cooling, hydraulic steering, hydraulic brakes, and hydraulic pilot control. According to current technology, the hydraulic steering and hydraulic braking systems are supplied with hydraulic oil by constant-displacement pumps or load-sensing pumps (LS pumps). Fan drives are usually operated with pressure-controlled pumps. Pilot pressure generation for the main hydraulics is also often achieved with constant-displacement pumps. Furthermore, feed pumps are required, for example, for closed hydraulic systems.

[0006] If a pressure-controlled auxiliary consumer temporarily requires no hydraulic energy, the supply pump continues to run, resulting in energy inefficiency, as the pump control system always maintains a constant pressure. Combining pressure-controlled and flow-controlled variable displacement hydraulic pumps into a single hydraulic pump presents a significant challenge due to the different control principles and the resulting high susceptibility to vibration and design complexity.

[0007] Newer systems, such as those disclosed in US 6,314,729 B1 and US 6,848,255 B2, are operated by a variable displacement pump. However, such systems have the disadvantage that the variable displacement control of the various consumers is extremely susceptible to oscillations. To overcome this disadvantage, DE 10 2016 000 186 A1 describes a system with combined variable displacement and pressure control for a common variable displacement pump. However, this control system also has the disadvantage of exhibiting a certain susceptibility to oscillations.

[0008] The present invention is therefore based on the objective of overcoming the disadvantages of the prior art and finding a suitable system that enables a stable joint supply of quantity-controlled and pressure-controlled consumers.

[0009] This problem is solved according to the invention by a hydraulic system having the features of claim 1. Advantageous embodiments of the invention are described in the dependent claims and the following description.

[0010] Accordingly, a hydraulic system is proposed with at least two hydraulic consumers supplied by a single variable displacement hydraulic pump and a control arrangement for regulating the hydraulic pump. Of the at least two consumers, at least one is pressure-controlled and at least one is flow-controlled. The consumers supplied by the common hydraulic pump can be auxiliary consumers of a machine, such as fans, steering, brakes, and / or pilot control. The hydraulic system can be an auxiliary consumer circuit of a machine or a part thereof.

[0011] According to the invention, an electrical control system for the hydraulic pump is provided; that is, the hydraulic pump is electrically controlled by means of the control arrangement. The control arrangement comprises a control unit and sensors connected to the control unit for detecting at least one quantity characterizing the demand of at least one consumer. The demand of the respective consumer preferably relates to a pressure or a delivery volume supplied by the hydraulic pump. A detected quantity can itself represent a demand, for example, a pressure detected by a pressure sensor. Alternatively or additionally, the demand of a consumer can be derived from a detected quantity or determined by the control unit.

[0012] According to the invention, the control unit is configured to determine, using the at least one parameter detected by the sensors, a pressure required by at least one pressure-controlled consumer and a volume flow required by at least one quantity-controlled consumer, and to control the hydraulic pump in such a way that the required pressure and volume flow are provided to the corresponding consumers.

[0013] It can be provided that the required pressure for one or more pressure-controlled consumers is not determined based on sensor signals, but rather stored as a fixed and / or definable value in a memory to which the control unit has access. The required flow rate is preferably derived from the signals of one or more sensors. Of course, it is also conceivable, alternatively or additionally, to determine the required pressure of one or more consumers using pressure sensors.

[0014] The hydraulic system according to the invention makes it possible to supply several differently controlled consumers with one and the same hydraulic pump, without having to resort to a complicated and vibration-prone control arrangement. Furthermore, supplying several consumers together with a single electrically controlled displacement unit results in significant energy savings.

[0015] A further advantage of the electrical control system according to the invention is that the hydraulic pump can be set to completely torque-free during the starting process of a work implement which includes the hydraulic system. This reduces the torque during the starting process of the work implement.

[0016] In one possible embodiment, the hydraulic system includes a second valve unit, which is connected between the hydraulic pump and at least one flow-controlled consumer. The second valve unit can be considered part of the consumer in a broader sense.

[0017] Preferably, the second valve unit is not electrically controlled by the control unit. The second valve unit can be hydraulically controlled.

[0018] In another possible embodiment, the sensor system includes a pressure sensor that detects the pressure in the second valve unit, particularly in a control line of the second valve unit. The measured pressure is provided to the control unit and preferably used by it to determine the required flow rate of the volumetric-controlled consumer supplied via the second valve unit. In addition to the measured pressure value, other parameters detected by additional sensors can be used.

[0019] In another possible embodiment, a first valve unit is provided that hydraulically connects at least two consumers to the hydraulic pump. The first valve unit is preferably not electrically controlled by the control unit. The control of the first valve unit is therefore preferably hydraulic, not electrical.

[0020] The first valve unit can be configured to direct hydraulic oil from the hydraulic pump to the second valve unit in a first switching position, and to block the hydraulic flow to the second valve unit in a second switching position. Alternatively, the first valve unit can be configured to allow hydraulic flow to the second valve unit in every switching position, and to block the hydraulic oil flow at a further outlet in a specific switching position. This is particularly advantageous if the consumer connected to the hydraulic pump via the second valve unit is a steering device or part thereof, since the steering device must always and with priority be supplied with hydraulic oil.

[0021] In another possible embodiment, the second valve unit is connected between the first valve unit and at least one flow-controlled consumer. Preferably, the first valve unit is connected to the second valve unit via a hydraulic control line. In this case, the previously described pressure sensor detects, in particular, the pressure in the control line between the first and second valve units.

[0022] In another possible embodiment, at least one hydraulic steering device or a part thereof (e.g., one or more steering cylinders for deflecting one or more wheels of an implement) is provided as a flow-controlled consumer, which is connected to the first valve unit, in particular via the second valve unit described above. The second valve unit can also be part of the steering device and may represent or comprise a steering valve block.

[0023] Preferably, the sensor system comprises a speed sensor coupled to the steering mechanism, which is used to detect the steering speed. The speed sensor can be mounted on a steering linkage. The measured speed value is provided to the control unit and preferably used by it to determine the required flow rate of the steering mechanism. In addition to the measured speed value, other parameters detected by additional sensors can be used, for example, a pressure value.

[0024] In another possible embodiment, the first valve unit is configured to supply at least one consumer with hydraulic oil in a priority manner over at least one other consumer. Preferably, a flow-controlled consumer is prioritized over a pressure-controlled consumer. The consumer supplied with priority can be a steering device or a part thereof.

[0025] In another possible embodiment, the first valve unit comprises a switchable priority valve which, preferably in a first switching position, supplies exclusively one or more flow-controlled consumers (for example, a steering device) and in a second switching position, supplies at least one flow-controlled consumer and one or more pressure-controlled consumers in parallel. The priority valve can be designed as a continuously switchable directional control valve.

[0026] In another possible embodiment, the control arrangement includes an actuator for adjusting the pressure and / or swivel angle of the hydraulic pump, which is electrically connected to the control unit. Based on the control commands from the control unit, the actuator adjusts the hydraulic pump such that the desired pressure or flow rate is achieved at the respective consumers.

[0027] In another possible embodiment, at least one pressure-controlled consumer is connected to the hydraulic pump, particularly to the first valve unit described above, via a third valve unit. This third valve unit is preferably electrically controllable by the control unit via an electrical control line. The term "controllable" here encompasses control within the framework of a regulation of the third valve unit. The third valve unit can include or be a pressure-reducing valve that reduces the pressure applied to the associated consumer to a defined value if the pressure level at the inlet of the pressure-reducing valve is too high. The threshold value at which the pressure-reducing valve switches is preferably predetermined by the control unit, which can be connected to an electrical control input of the pressure-reducing valve.

[0028] In another possible embodiment, at least one pressure-controlled consumer can be supplied with hydraulic pressure via a hydraulic accumulator, the hydraulic accumulator preferably being chargeable via the hydraulic pump. The hydraulic accumulator can comprise one or more individual accumulators. The hydraulic accumulator can be connected to the associated consumer via a switching valve.

[0029] In another possible embodiment, the sensor system includes a pressure sensor that detects the pressure in the hydraulic accumulator and thereby continuously monitors the accumulator's fill level. The control arrangement is preferably configured to regulate the hydraulic pump based on the pressure sensor signals so that the accumulator is filled, for example, when a certain minimum fill level is undershot. For this purpose, the pressure sensor signals are provided to the control unit.

[0030] In another possible embodiment, a hydraulic brake device is connected to the hydraulic accumulator. The pressure in the brake system can be monitored via the aforementioned pressure sensor.

[0031] In another possible embodiment, a hydraulic motor for a fan unit and / or a hydraulic pilot control is provided as the pressure-controlled consumer. A pressure reducing valve and / or a pressure-reducing valve can be installed upstream of the fan motor or the pilot control.

[0032] It is possible to connect several pressure-controlled consumers in parallel to the first valve unit, particularly in parallel with one or more flow-controlled consumers. Some or all of the pressure-controlled consumers can be connected to the first valve unit via a third valve unit. Alternatively, one or more consumers can be connected directly to the first valve unit.

[0033] In another possible embodiment, apart from the electrically controlled hydraulic pump, no additional pump is required to supply the consumers. This results in a particularly simple and energy-efficient hydraulic system for supplying and controlling the various consumers.

[0034] The present invention further relates to a work machine with a hydraulic system according to the invention. This offers the same advantages and properties as previously described for the hydraulic system according to the invention, therefore a repetitive description is omitted. The work machine can, in particular, be a hydraulic excavator, although the work machine according to the invention is not limited to this. The hydraulic system according to the invention can, for example, be part of a wheel loader, dumper, or telehandler. The hydraulic system according to the invention is preferably part of an auxiliary circuit of the work machine.

[0035] Further features, details and advantages of the invention will become apparent from the exemplary embodiments explained below with reference to the figures. The figures show: Figure 1: a schematic circuit diagram of the hydraulic system according to a first embodiment; Figure 2: a schematic circuit diagram of the hydraulic system according to a second embodiment; Figure 3: a more detailed representation of the hydraulic system according to Figure 2 ; and Figure 4: a schematic circuit diagram of the hydraulic system according to the invention in a third embodiment.

[0036] In the Figure 1Figure 1 shows a first embodiment of the hydraulic system according to the invention as a schematic circuit diagram. The hydraulic system can be part of an auxiliary circuit of a working machine, such as a hydraulic excavator, through which several auxiliary consumers are supplied with hydraulic oil.

[0037] The hydraulic system according to the invention provides several pressure-controlled and flow-controlled hydraulic consumers, which are supplied by a single adjustable hydraulic pump 10. The hydraulic pump 10 can, for example, be an axial piston pump.

[0038] The outlet of hydraulic pump 10 is connected to an inlet of a first valve block 30 (= first valve unit), which primarily supplies a second valve block 120 (= second valve unit) with hydraulic oil. The second valve block 120 is connected via a supply line to a second outlet of the first valve block 30. Furthermore, the two valve blocks 30 and 120 are connected to each other via a hydraulic control line, the pressure of which is detected by a first pressure sensor 80. The control line may be a load cell signaling line.

[0039] In the embodiment shown here, the second valve block 120 is part of a hydraulic steering device, which also includes one or more hydraulic steering cylinders 110. When one of the pressure chambers is pressurized accordingly, the steering cylinder(s) 110 cause the steered wheels of the implement (not shown) to deflect.

[0040] The steering device further comprises a steering wheel 100 with a steering linkage, which is coupled to the second valve block 120 in such a way that a specific deflection of the steering wheel 100 leads to a specific adjustment of the steering cylinder(s) 110 and thus to a specific deflection of the wheels. A speed sensor 90 is connected to the steering linkage and detects an angle and / or an angular velocity and thus the steering speed.

[0041] The steering cylinder(s) 110 constitute the hydraulic consumer in the narrower sense, although for the sake of simplicity, the entire steering system will be referred to as the hydraulic consumer in the following. The steering system is a flow-controlled consumer that requires a specific volume flow from the hydraulic pump 10.

[0042] In addition to the steering device as a flow-controlled consumer, a pressure-controlled consumer 60 is provided, which in this embodiment is a hydraulic fan motor 60 for driving a ventilation system of the working equipment. The fan motor 60 is connected via a pressure reducing valve 50 (= third valve unit) to a first outlet of the first valve block 30.

[0043] The hydraulic pump 10 can be adjusted via an actuator 20 in the form of a pump controller to deliver a specific flow rate and pressure. The actuator 20 can be a pressure regulator and / or a swivel angle controller. The pump controller 20 regulates the hydraulic pump 10 in such a way that the fan motor 60 is simultaneously operated at the required pressure and the steering mechanism is supplied with the required flow rate.

[0044] In contrast to systems known from the prior art, the hydraulic pump 10 is not controlled by a load cell control or a combination of several load cell, pressure, and, if applicable, power controllers, but by an electrical control arrangement. Thus, an electro-hydraulic displacement unit is used to supply all consumers of the hydraulic system.

[0045] The control arrangement comprises an electronic control unit (ECU) 40, which is connected to the various sensors 80 and 90 and receives and processes their signals. From the pressure measured by the first pressure sensor 80 in the control line between the valve blocks 30 and 120 and the signals from the speed sensor 90, the ECU 40 calculates the required flow rate for the steering system and generates a control signal for the pump controller 20, to which the ECU 40 is electrically connected. The ECU 40 thus provides the controller 20 with a corresponding target value, whereupon the controller regulates the hydraulic pump 20 to deliver the requested flow rate.

[0046] The valve block 30 can be configured as a so-called priority valve, which in a first switching position connects the pump output only to the steering device and in a second switching position connects it in parallel to both the steering device and the fan motor 60. The steering device is preferably supplied, as its function is essential for the operation of the implement.

[0047] The fan motor 60 must be operated at a specific pressure (which corresponds to a specific speed requirement for the fan), i.e., it is pressure-controlled. To provide the required pressure, a third valve unit in the form of an electrically controlled pressure reducing valve 50 is connected between the fan motor 60 and the first outlet of the first valve block 30. Its control input is electrically connected to the control unit 40. The control unit 40 monitors the limit pressure of the pressure reducing valve 50, for example, based on a setting for the operation of the ventilation system or a speed requirement. As long as the pressure at the first outlet of the first valve block 30 is greater than the limit pressure of the pressure reducing valve 50 set by the control unit 40, the same pressure is always applied to the fan motor 60. The pressure requirement is then provided to the pump controller 20 as a setpoint by the control unit 40.The hydraulic motor 10 is controlled in such a way that the pressure supplied is greater than or equal to the limit pressure of the pressure reducing valve 50.

[0048] The pressure-controlled consumer can generally be a hydraulic motor (such as the fan motor 60 of the embodiment shown here), a valve block, or any other pressure-controlled consumer. Several pressure-controlled consumers can also be connected in parallel to each other to the first valve block 30. Such an embodiment is shown in Figure 2, where, in addition to the fan motor 60, two further pressure-controlled consumers 140, 170 are provided and connected in parallel to the fan motor 60 to the first outlet of the first valve block 30. Components already included in the Figure 1 The reference numerals shown are identical to the embodiment of the Figure 1 and will not be described again here.

[0049] An additional pressure-controlled consumer is provided in the form of a hydraulic pilot control 140, which is directly connected to the first output of the first valve block 30. A hydraulic pressure reducing valve 130 can be installed upstream of the pilot control 140. The pilot control 140 can include or represent a control oil unit that provides a specific control pressure (e.g., 30 bar) for other components of the hydraulic system (e.g., for a main consumer circuit).

[0050] Furthermore, a hydraulic brake device 170 is provided as an additional pressure-controlled consumer, which is connected directly to the first output of the first valve block 30 in parallel with the other pressure-controlled consumers 60, 140. The brake device 170 can include a brake valve (for example, a dual-circuit brake valve) with a brake pedal.

[0051] The brake system is pressurized via a hydraulic accumulator 150. The pressure in the accumulator 150 is continuously monitored by a second pressure sensor 160, which is electrically connected to the control unit 40, and the signals are provided to the control unit 40. If the pressure in the hydraulic accumulator 150 falls below a defined limit (this limit can be stored in the control unit or in a storage device connected to it), the control unit 40 sends a corresponding signal to the pump controller 20 to activate the hydraulic pump 10 in order to charge the hydraulic accumulator 150. The charging process continues until the hydraulic accumulator 150 is full.

[0052] If the pressure requirement for the hydraulic accumulator 150 is higher than the pressure requirement for the fan motor 60, the pressure is reduced accordingly by the pressure reducing valve 50.

[0053] If there is excessive pressure at the steering device (for example, due to a charging process of the hydraulic accumulator 150 and a corresponding pressure generation by the hydraulic pump 10), the second valve block 120 preferably regulates the excess pressure independently (similar to a pressure balance).

[0054] This makes it possible for a single pump controller 20 and a single hydraulic pump 10 to provide both the required flow rate for the steering device and the required and usually different pressures for hydraulic accumulator 150, pilot control 140, fan motor 60 and steering device.

[0055] Due to the purely electric design of the pump controller 20, the hydraulic pump 10 can be set to completely torque-free during the start-up process. This reduces the torque during the machine start-up, which significantly facilitates the starting process.

[0056] The control system supplies the various auxiliary consumers with the required amount of oil as needed via a single adjustable hydraulic pump.

[0057] The Figure 3 shows the exemplary embodiment of the hydraulic system of the Figure 2 In a more detailed view, the dual-circuit brake valve 170 can be seen, which connects two individual hydraulic accumulators 150 to the hydraulic brakes. A check valve is installed between the brake valve 170 and the hydraulic accumulators 150 on the one hand, and the first valve block 30 on the other, preventing hydraulic backflow from the accumulator 150 to the first valve block 30.

[0058] Furthermore, the priority valve 30 with its two switching positions can be seen (first, in the Figure 3 lower switch position: sole power supply to the steering device; second, in the Figure 3upper switch position: parallel supply to the steering device and the other pressure-controlled consumers).

[0059] The structure of the steering valve and the second valve block 120 is also visible. The priority valve 30 is not controlled via the control unit 40, but hydraulically via the control line connected to the second valve block 120.

[0060] In the Figure 4 A third embodiment of the hydraulic system according to the invention is shown as a schematic circuit diagram. The only difference compared to the embodiment of the Figure 1The difference is that no first valve block 30 (first valve unit) is provided. Instead, the pressure reducing valve 50 and the second valve block 120 (second valve unit) are directly connected to the hydraulic pump 10. The pressure sensor 80 detects the pressure in a hydraulic line of the second valve block 120, which may, for example, be a hydraulic control line of the second valve block 120. In the exemplary embodiment of the Figure 4 Therefore, there is no prioritization of the hydraulic flow to the second valve block 120, whereas the electrical control according to the invention described above continues to be carried out by the control unit 40. Reference symbol list:

[0061] 10 Hydraulic system 20 Actuator (pump regulator) 30 First valve unit 40 Control unit 50 Third valve unit 60 Pressure-controlled consumer (fan motor) 80 Pressure sensor 90 Speed ​​sensor 100 Steering wheel 110 Steering cylinder 120 Second valve unit 130 Pressure reducing valve 140 Pilot control 150 Hydraulic accumulator 160 Pressure sensor 170 Brake device

Claims

1. A hydraulic system comprising at least two hydraulic consumers, of which at least one consumer is pressure-controlled and at least one consumer is quantity-controlled, an adjustable hydraulic pump (10), via which the at least two consumers are supplied jointly, and a control arrangement, characterised in that the hydraulic pump (10) is electrically controlled by means of the control arrangement, wherein the control arrangement comprises a control unit (40) and a sensor system connected to the control unit (40) for detecting at least one variable characterising a requirement of a consumer, wherein the control unit (40) is set up to determine, using the at least one detected variable, a pressure required by a pressure-controlled consumer and a volume flow rate required by a quantity-controlled consumer and to control the hydraulic pump (10) in such a way that the required pressure and the required volume flow rate are provided.

2. The hydraulic system according to claim 1, further comprising a second valve unit (120), which is connected between the hydraulic pump (10) and at least one quantity-controlled consumer and preferably is not electrically controlled by the control unit (40).

3. The hydraulic system according to the preceding claim, wherein the sensor system comprises a pressure sensor (80), which detects a pressure in the second valve unit (120), in particular in a control line of the second valve unit (120).

4. The hydraulic system according to any one of the preceding claims, further comprising a first valve unit (30), which connects the at least two consumers to the hydraulic pump (10) and preferably is not electrically controlled by the control unit (40).

5. The hydraulic system according to claim 4 and any one of claims 2 to 3, wherein the second valve unit (120) is connected between the first valve unit (30) and at least one quantity-controlled consumer, wherein the first valve unit (30) is preferably connected via a hydraulic control line to the second valve unit (120) and the sensor system comprises in particular a pressure sensor (80), which detects a pressure in the control line between first and second valve unit (30, 120).

6. The hydraulic system according to any one of the two preceding claims, wherein the first valve unit (30) is set up to supply at least one, in particular quantity-controlled, consumer (110) with hydraulic oil in a prioritised manner over at least one other, in particular pressure-controlled, consumer (60, 140, 170).

7. The hydraulic system according to the preceding claim, wherein the first valve unit (30) comprises a switchable priority valve, which preferably supplies, in a first switched position, exclusively one or more quantity-controlled consumers (110) and, in a second switched position, in parallel the at least one quantity-controlled consumer (110) and one or more pressure-controlled consumers (60, 140, 170).

8. The hydraulic system according to one of the preceding claims, wherein at least one quantity-controlled consumer (110) is part of a hydraulic steering device (100, 110, 120), wherein the sensor system preferably comprises a speed sensor (90), coupled to the steering device (100, 110, 120), for detecting a steering speed.

9. The hydraulic system according to any one of the preceding claims, wherein the control arrangement comprises an adjustment means (20) for adjusting a pressure and / or a pivot angle of the hydraulic pump (10), which adjustment means is electrically connected to the control unit (40).

10. The hydraulic system according to any one of the preceding claims, wherein at least one pressure-controlled consumer (60) is connected via a third valve unit (50) to the hydraulic pump (10), wherein the third valve unit (50) is preferably electrically controllable by the control unit (40) via an electric control line.

11. The hydraulic system according to any one of the preceding claims, wherein at least one pressure-controlled consumer (170) is suppliable via a hydraulic store (150), wherein the hydraulic store (150) is preferably chargeable via the hydraulic pump (10), wherein a consumer connected to the hydraulic store (150) is, in particular, a hydraulic braking device (170).

12. The hydraulic system according to the preceding claim, wherein the sensor system comprises a pressure sensor (160) which detects a pressure prevailing in the hydraulic store (150), wherein the control arrangement is preferably set up to control the hydraulic pump (10) in dependence on a signal of the pressure sensor (160) in such a way that the hydraulic store (150) is filled.

13. The hydraulic system according to any one of the preceding claims, wherein a hydraulic motor (60) for a fan unit and / or a hydraulic pilot control (140) is provided as pressure-controlled consumer and is preferably disposed downstream of a pressure reducing valve (130) and / or a pressure relief valve (50).

14. The hydraulic system according to any one of the preceding claims, wherein no further pump for supplying the consumer is provided besides the hydraulic pump (10).

15. A working device, in particular hydraulic bagger, comprising a hydraulic system according to any one of the preceding claims, wherein the hydraulic system is preferably part of an auxiliary consumer circuit of the working device.