Work machinery equipped with motor brakes, especially cranes.

Abstract

To provide a work machine, particularly a crane, which comprises a cable winch capable of winding up a cable to lift a load and unwinding the cable to lower the load, a prime mover capable of driving the cable winch, and a controller capable of controlling the prime mover, and in which the prime mover is equipped with a braking device that generates a braking torque that resists an externally generated torque.SOLUTION: According to the present invention, when a load is lowered, a controller controls a braking device and controls a prime mover according to a predetermined target braking torque and a braking torque that can be provided by the prime mover, so that the load is lowered at a predetermined, in particular, a constant speed. The present invention also relates to a method for lowering a load by the working machine according to the present invention and a corresponding computer program product.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] , ,

[0001] The present invention relates to a working machine described in the preamble of claim 1, particularly a crane, a method for lowering a load by the working machine, and a corresponding computer program product.

Background Art

[0002] In many working machines, a driven cable winch (electric cable winch) is used to lift a load. This includes moving heavy machine parts such as a boom or bracing frame by a cable winch of a bracing cable or an adjustment winch (the load of the machine itself), or lifting an object to be moved by a hoist rope winch (external load) with the working machine. The load is generally lowered by rewinding (loosening the winding, paying out) a cable connected to the load via a cable winch. In order to prevent the load from descending in an uncontrollable state due to excessive kinetic energy caused by its own weight, the process of lowering the load or the process of rewinding the corresponding cable needs to be braked under control.

[0003] Braking is usually performed by converting the potential energy of the load into heat during descent. In the prior art, it is known to convert the braking force required to lower the load into heat by a hydraulic device. This can be achieved by selectively activating a hydraulic consumption device (hydraulic utilization device) such as a hydraulic fan drive. A hydraulic brake equipped with one or more brake pumps designed particularly for the braking process is usually used. The brake pump can supply a large amount of hydraulic flow rate at a corresponding pressure stage to generate the required braking force. The braking energy absorbed by the brake pump is converted into heat at that pressure stage, heating the hydraulic oil (working oil). This heat must be released by a hydraulic cooler or a fan. For this purpose, the fan rotates at a high speed, generating a considerable noise level.

[0004] Furthermore, the torque balance between the cable winch or hoist and the brake pump in these solutions is typically designed so that the winch prime mover (winch motor) always supplies effective torque (positive torque). This principle allows for good to very good control quality with less effort, although it requires fuel consumption in the descent mode. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Therefore, the present invention addresses the challenge of overcoming the aforementioned drawbacks in general work machinery, reducing noise pollution and fuel consumption, and enabling controlled braking and lowering of loads. [Means for solving the problem]

[0006] According to the present invention, this objective is achieved by a work machine having the features of claim 1, a method having the features of claim 11, and a computer program product having the features of claim 15. Advantageous embodiments of the present invention are described in the dependent claims and the following description.

[0007] Accordingly, according to one aspect of the present invention, a work machine is proposed comprising a cable winch, a prime mover for driving the cable winch, and a controller for controlling the prime mover. The controller may comprise a plurality of control units or control devices connected to each other in a communicative manner, or it may be a single control unit. The work machine can, in principle, be mobile (e.g., crawler crane, rail crane, mobile crane) or fixed (e.g., tower crane, port crane).

[0008] Cables for lifting and lowering loads are attached to a cable winch so that they can be wound up and unwound. The term "load" should be interpreted broadly here and can refer to an external load attached to a load handling device (e.g., a hoist block), or components of a working machine such as a boom or bracing frame that is mounted to be swivelable. In the former case, the cable winch is specifically a hoist rope winch, and the cable is the hoist rope. In the latter case, the cable winch may be an adjustable winch that can be part of a bracing cable for moving the aforementioned components.

[0009] In particular, the prime mover is an internal combustion engine, such as a diesel engine. In addition to driving the cable winch, the prime mover can also function as a traction drive for moving the work machine. The prime mover is equipped with a braking device that generates braking torque to counteract externally generated torque; this is also called a prime mover brake. In particular, the braking device can be actively operated, for example, by activating a corresponding switch element in the cab of the work machine. The braking device can be operated or controlled by a controller. In this example, the term “control” can mean both open-loop control and closed-loop control (including comparison between target values ​​and actual values).

[0010] Internal combustion engines can also be replaced with electric motors. In this case, the braking system needs to be replaced with an equivalent component. This replacement could be, for example, an electric resistor.

[0011] According to this invention, when a load is lowered or a cable is unwound (unwound) from the winch, the controller controls the prime mover (i.e., by open-loop control and / or closed-loop control) in accordance with a predetermined target braking torque and the braking torque actually obtained by the prime mover, causing the load to lower at a predetermined speed, in particular a variable speed or a constant speed (which corresponds to a predetermined speed, in particular a constant speed, for a cable winch). The controller determines the target braking torque from the available variables. In particular, this is specified for the cable winch or the winch motor driving the cable winch.

[0012] Therefore, the basic idea of ​​the present invention is to decelerate the load using the engine brake of the engine, and for this purpose the engine is controlled to obtain a predetermined descent speed of the load. Most engines installed in conventional work machines are internal combustion engines that already have engine brakes (although these are used as brakes for travel), so there is no need to make time-consuming retrofits (modifications) to existing machines.

[0013] By using a motorized brake to control the deceleration of a cable winch or load, the use of hydraulic brakes can be reduced completely or significantly. This eliminates the need for noisy fans to cool the hydraulic oil, greatly reducing overall noise levels in the system. Furthermore, conventional motorized brakes are true continuous brakes that can be used for very long periods without the reduction in braking force caused by high oil temperatures.

[0014] There are further advantages to using the engine brake to decelerate the load. The heat load in the entire engine chamber is reduced due to the high-temperature exhaust from the fan. In particular, energy is converted into compression work and / or depressurization work and discharged from the engine via the exhaust system instead of a hydraulic cooler. Furthermore, since braking energy is not converted into heat by the hydraulic system, the hydraulic braking force is reduced, thereby reducing the heat load on the hydraulic system. Finally, by using the engine brake in downhill mode, fuel consumption is reduced because the engine can reach the desired speed without or with minimal injection (fuel injection).

[0015] In one embodiment, the prime mover may be an internal combustion engine, such as a spark-ignition engine (gasoline engine), or preferably a diesel engine. The prime mover's braking system may consist of an air vane located in the prime mover's exhaust duct and / or a throttle valve located in the prime mover's intake duct. The corresponding valves are further closed to increase braking torque. Alternatively, or in addition to the above, the prime mover may be equipped with a depressurization brake (also known in English as a "Jacob's brake" or "Jake brake"). In particular, the braking system may be a well-known prime mover brake used in conventional internal combustion engines. Preferably, the prime mover also functions as a drive for the work machine, and the braking system may be used to reduce the travel speed in a known manner, in addition to the function of the present invention of braking the lowering speed of the load.

[0016] In further possible embodiments, the controller may be configured to determine a target braking torque based on at least the detected current load, the current cable payout speed (winding speed), the desired load descent speed, and / or the desired rotational speed, e.g., the desired rotational speed of a cable winch and / or prime mover. The current load may be detected by a sensing device on the work machine and made available to the controller. For this purpose, the sensing device may be equipped with one or more sensors to measure the current load. The larger the detected load, the larger the target braking torque required to achieve a particular descent speed. The current cable payout speed (e.g., hoist cable of a hoist winch or guy cable of a regulating winch) may also be detected by a sensor or manually preset by the operator of the work machine via an input means. The desired descent speed or desired rotational speed may be automatically determined by the controller using other parameters and / or manually preset by the operator of the work machine using an input means (e.g., a master switch).

[0017] Alternatively, or in addition to the above, the controller may be configured to determine the braking torque actually obtained by the prime mover based on at least the detected current speed of the prime mover (i.e., the resulting braking torque may be speed-dependent). The resulting braking torque may depend on the characteristics and configuration of the braking system and / or the prime mover.

[0018] In yet another possible embodiment, it is proposed to configure the controller to control the rotational speed, particularly the speed of the prime mover or the rotational speed of the winch motor driving the cable winch, to a target speed in order to obtain a target braking torque when the load is lowered. Control of the prime mover speed due to externally generated torque may include, in addition to the influence on the braking system (i.e., control by open-loop control and / or closed-loop control), effective control of the prime mover by at least one yet another parameter of the prime mover, such as fuel injection to generate an effective prime mover torque to counteract the braking torque generated by the braking system. This improves the accuracy of the control of the prime mover speed, and consequently the accuracy of the load lowering speed.

[0019] The target speed may refer to the speed of the prime mover. However, the target speed may also refer to the rotational speed of the cable winch (or the winch motor driving the cable winch) (i.e., the winch speed is controlled). This may be the same as or different from the speed of the prime mover (for example, because the cable winch is connected to the prime mover via a gear system and / or hydraulic circuit). It is also conceivable that the relevant control variable in the control circuit is the speed of the prime mover, and the target speed is converted from the desired winch rotational speed to the corresponding prime mover speed. In general, the speed of the winch motor can be converted to the speed of the prime mover, and vice versa, because these are linked through the properties of intervening components such as gear systems. It should be noted at this point that when the terms “prime mover” or “speed of prime mover” are used, it always refers to a prime mover equipped with a braking system.

[0020] In yet another possible embodiment, it is proposed that the prime mover is an internal combustion engine with fuel injection, and the controller is configured to control the brakes in an open-loop and / or closed-loop manner so that the braking torque generated by the brakes is greater than a target braking torque. In other words, the controller specifically requests a braking torque greater than the braking torque required to achieve a specified descent speed. This results in the actual speed of the prime mover falling below the target speed. To compensate for this effect, the controller is configured to activate the fuel injection and control it to equalize the greater braking torque (or reduction in prime mover speed) of the brakes, thereby setting the target torque for the prime mover or the target braking torque for the cable winch. Since the required braking torque is preferably only slightly greater than the requested value, only a small amount of fuel injection is needed for equalization. However, even such a small amount of fuel injection is sufficient to reliably cool the fuel injection nozzles located in the combustion chamber of the internal combustion engine.

[0021] By activating injection, extremely high control accuracy is achieved with respect to the prime mover speed, improving the stability of the entire control loop. This contributes significantly to the overall system stability, especially in the case of long signal transmission cycle times (e.g., requests and feedback via CAN bus). Without injection, the entire system, winch speed, and load may vibrate.

[0022] In yet another possible embodiment, the work machine is equipped with a cable winch or a hydraulic brake for braking a load, which can be operated by a controller as needed, instead of or in parallel with the brake of the prime mover, in order to generate braking torque for lowering the load. The hydraulic brake generates braking torque for the prime mover (i.e., prime mover 16) or cable winch connected to the hydraulic brake by converting energy into heat.

[0023] A hydraulic braking system comprises at least one hydraulic brake equipped with a hydraulic pump (brake pump), and in particular, at least one pressure relief valve that functions as a pressure stage through which hydraulic oil flows and converts the braking energy absorbed by the brake pump into heat. The pressure relief valve can be actively controlled to adjust the braking torque. As a result, the heated hydraulic oil needs to be cooled once it exceeds a certain temperature. For this purpose, the hydraulic braking system preferably comprises at least one hydraulically operated cooling device. This may include a hydraulic pump (additional brake pump) and a hydraulic fan motor, which are also part of the hydraulic braking system as they can also be used to generate the braking torque.

[0024] In yet another possible embodiment, the controller is configured to fully or partially brake the descent of the load via a hydraulic brake in a first braking stage, and in a subsequent second braking stage, to continuously or gradually reduce the braking torque transmitted to the cable winch by the hydraulic brake, while continuously or gradually increasing the braking torque transmitted to the cable winch by the motor brake. Preferably, the controller is configured to maintain a constant descent speed of the load or rotational speed of the motor while the braking torque is transmitted from the hydraulic brake to the motor brake.

[0025] In this modification, braking, i.e., control to the target speed, is initially performed via a hydraulic brake, and especially exclusively (i.e., with the prime mover's brake inactive). Then, preferably as soon as the speed stabilizes, braking torque is continuously transmitted from the hydraulic brake to the prime mover's brake. In the third braking stage, braking torque is preferably provided exclusively by the prime mover's brake, and the hydraulic brake is activated only temporarily if the detected current load exceeds a defined limit (preventing a speed anomaly) or if the prime mover's brake fails. Preferably, the first braking stage is sufficiently short (e.g., less than 20 seconds, preferably less than 10 seconds) so that the hydraulic oil does not heat up to the point where it is necessary to activate the fan. This avoids noise pollution from fan operation.

[0026] In a possible alternative embodiment, the braking device of the prime mover bears the braking torque for braking the lowering of the load right from the start, particularly exclusively (i.e., the hydraulic braking device of the prime mover is non-operational from the start). Also in this variant, the hydraulic braking device can be temporarily switched on when the detected current load becomes a load exceeding a defined limit value, and / or the hydraulic braking device can be switched on as a backup in case of a failure of the prime mover brake.

[0027] In another possible embodiment, the cable winch is connected to the prime mover via a transfer case. The above-mentioned hydraulic braking device can be connected to the transfer case so that one or more brake pumps can be driven by the prime mover. Preferably, all the braking components of the working machine that can be used to brake the lowering speed of the load are coupled or can be coupled to the prime mover via the transfer case.

[0028] Preferably, the closed hydraulic circuit is connected between the transfer case and the cable winch. In particular, the closed hydraulic circuit has a hydraulic pump that can be driven by the prime mover via the transfer case and a hydraulic winch motor.

[0029] In yet another possible embodiment, it is proposed that the working machine has a detection device connected to a controller for detecting the current rotational speed, particularly the current rotational speed of the prime mover and / or the winch motor, and / or for detecting the current load, and / or for detecting the current torque (acting on, for example, the cable winch or the winch motor). The detection device can comprise one or more sensors for detecting the aforementioned variables.

[0030] In yet another possible embodiment, the working machine is configured as a mobile crane comprising a boom (e.g., a lattice boom or telescopic boom) and a hoist rope guided above the boom head. A load-lifting device (e.g., a hoist block) is attached to the hoist rope to which a load to be lifted can be attached. A cable winch braked by a motor brake can be a hoist rope winch that winds up the hoist rope. Alternatively, the crane may be configured to have a boom or bracing frame (e.g., an A-frame or derrick boom) capable of luffing (up and down movement) using an adjustment winch and a corresponding cable, and the cable winch braked by a motor brake is the adjustment winch. The crane may comprise a movable lower carriage and a superstructure with a boom rotatably mounted on the lower carriage structure. The controller may be a crane controller (or one comprising one).

[0031] In other possible embodiments, communication or signal transmission between the controller and the prime mover or brake (and between the controller's control units, if provided) is carried out via a bus, particularly a CAN bus. All relevant control variables and signals are exchanged via this bus.

[0032] According to a second aspect, the present invention relates to a method for lowering a load using a work machine according to the present invention. Here, as has already been described with respect to the work machine according to the present invention, the controller controls the prime mover so that the load descends at a predetermined, particularly constant, speed by controlling the braking device in accordance with a target braking torque and the braking torque actually obtained by the prime mover. This control is preferably performed in relation to the speed of the prime mover or winch motor. This provides the same advantages, characteristics, and modifications as have already been described with respect to the work machine according to the present invention, so a repetition is omitted.

[0033] In one possible embodiment, the prime mover is an internal combustion engine with a fuel injection system, and the controller performs open-loop and / or closed-loop control of the brakes so that the braking torque generated by the brakes is greater than a target braking torque. In this case, the controller controls the speed of the prime mover via fuel injection so that the greater braking torque of the brakes is equalized and the target braking torque is set, particularly in the case of a cable winch.

[0034] In yet another possible embodiment, the work machine is equipped with a hydraulic brake for braking a cable winch, and the controller is configured to brake the descent of the load directly (i.e., without using the hydraulic brake first) via the prime mover's brake, and the hydraulic brake is switched on (activated) only in the case of a specific load or in the event of a failure of the prime mover brake.

[0035] In a possible alternative embodiment, the work machine is equipped with a hydraulic brake for braking a cable winch, and the controller fully or partially brakes the descent of the load via the hydraulic brake in the first braking stage, and in the subsequent second braking stage, the controller continuously or gradually reduces the braking torque transmitted to the cable winch by the hydraulic brake while simultaneously continuously or gradually increasing the braking torque transmitted to the cable winch by the prime mover brake, preferably keeping the load descent speed constant while the braking torque is being transmitted from the hydraulic brake to the prime mover brake. This variation involves a gradual transition of braking torque from the hydraulic brake to the prime mover brake. This transition is performed, for example, as soon as the speed stabilizes when lowering the load, and the controller can calculate the required braking torque from the detected load, payout speed, desired load descent speed and / or desired winch speed for descent.

[0036] The present invention also relates to a computer program product that, when the program is executed, includes instructions, particularly by the controller, to cause the work machine according to the present invention to perform steps of the method according to the present invention. Of course, this relates only to steps that can be performed automatically, particularly by the controller, as described above. Since the same advantages, characteristics, and embodiments are obtained with respect to the work machine according to the present invention as already described, redundant explanations are omitted.

[0037] Further applications of the solutions according to the present invention are conceivable. These include, for example, a boom adjustment winch or a crawler chassis drive system.

[0038] Further features, details, and advantages of the present invention can be understood from exemplary embodiments described below with reference to the figures. [Brief explanation of the drawing]

[0039] [Figure 1] Figure 1 shows a schematic side view of a work machine according to an embodiment of the present invention. [Figure 2] Figure 2 shows a flowchart of an embodiment that is an example of a method according to the present invention for lowering a load. [Modes for carrying out the invention]

[0040] Figure 1 shows a schematic diagram of a preferred exemplary embodiment of the work machine 10 according to the present invention, which is configured as a crawler crane comprising a movable lower carriage and an upper carriage rotatably mounted thereon. However, the following description of the prime mover control applies to all embodiments of the work machine 10 and is not limited to this example.

[0041] This crawler crane 10 is equipped with a boom 11 that is rotatably mounted on the superstructure. The boom can be moved up and down (luffing motion) by the operation of bracing cables (not shown) and an adjustment winch (not shown). A cable winch 12 (hoist rope winch) located on the superstructure is equipped with a cable 14 (hoist rope) that can be wound up and unwound, and supports a load lifting means to which a load 1 is attached. The load 1 can be raised or lowered by winding up and unwinding the hoist rope 14.

[0042] The cable winch 12 is driven through a closed hydraulic circuit 40 connected to a prime mover 16 via a mechanical transfer case 19. The prime mover 16, configured as an internal combustion engine, drives a hydraulic pump 41 in the closed hydraulic circuit 40 via the transfer case 19, and the hydraulic pump 41 drives a hydraulic motor 42 which functions as a winch motor.

[0043] The hydraulic pump 41 and / or hydraulic motor 42 are adjusted as appropriate according to the operator's desired specifications, for example by a master switch, to lower the load, thereby unwinding (feeding out) the hoist cable 14 from the cable winch 12 and lowering the load 1. The pump 41 and / or motor 42 are controlled via a controller 20, which will be described in more detail below.

[0044] As shown in the exemplary embodiment in Figure 1, the work machine 10 includes a hydraulic braking device 30, which is also coupled to the prime mover 16 via a transfer case 19 and can be driven by the prime mover. The hydraulic braking device 30 can consist of a hydraulic brake comprising a hydraulic pump 31 (brake pump) that can be driven by the prime mover 16 and a pressure relief valve 32 as a pressure stage (pressure regulating stage).

[0045] To limit the speed of load 1 as it descends, the hydraulic brake 30 can be activated to generate a braking torque that acts on the winch motor 42 or cable winch 12 to reduce the descent speed. For this purpose, the brake pump 31 is controlled by the control unit 21 to create a flow rate through the pressure relief valve 32, thereby generating braking force. The pressure relief valve 32 can also be controlled by the control unit 21. During prolonged operation of the hydraulic brake, the hydraulic oil (hydraulic fluid) heats up, requiring cooling by a cooling device. In the exemplary embodiment shown in Figure 1, the hydraulic brake 30 further includes a hydraulic motor 33 to which hydraulic oil is supplied via another hydraulic pump 34 for this purpose. The hydraulic oil for the hydraulic brake 30 is drawn from a hydraulic tank 15 (open hydraulic circuit).

[0046] The prime mover 16 is equipped with a braking device 18 (hereinafter also referred to as a prime mover brake) to counteract externally applied torque (for example, torque generated by the descent of load 1 due to gravity and transmitted to the prime mover 16 via the cable winch 12, hydraulic circuit 40, and transfer case 19). As shown in the exemplary embodiment of Figure 1, the prime mover 16 can be configured as a diesel engine equipped with an exhaust duct 17 in which an air vane 18 is positioned as a braking device. Alternatively, or in addition to the above, a throttle valve may be provided in the intake duct of a spark ignition engine, or a compression release brake may be provided.

[0047] In particular, the prime mover 16 also functions as a drive engine for driving the crawler tracks of the crawler crane 10.

[0048] According to the present invention, the hydraulic brake 30 is not used (at least exclusively not used) to brake the load 1 during descent, and instead the motor brake 18 is used. To obtain the required braking torque, the speed of the winch motor 42 is controlled by the controller 20 of the work machine 10. In the illustrated exemplary embodiment, the controller 20 has a first control unit 21 that controls the brake pumps 31, 34 and receives various sensor signals, and a second control unit 22 that controls the motor and brake 18 and is connected to the first control unit 21 (in Figure 1, signals and control connections are shown by dashed lines). The second control unit 22 can also be a motor control unit and part of the motor 16. Instead of the two control units 21, 22, there may be three or more control units, or just a single control unit that also controls the motor 16 and brake 18.

[0049] The controller 20 determines the target braking torque of the cable winch 12 from the detected load, the payout speed of the hoist cable 14 to be considered, and the target speed of the cable winch 12 (or winch motor 42). This ensures that the controlled descent of the load 1 reaches a predetermined speed, particularly a constant speed. Furthermore, the currently available speed-dependent braking torque of the prime mover brake 18 is determined. According to one embodiment, the available braking torque is determined by the second control unit 22 and transmitted to the first control unit 21, and the actual control is performed by the first control unit 21.

[0050] According to the first modification, the braking torque for lowering the load 1 is initially provided by the motor brake 18. The controller 20 establishes a torque balance from the available motor braking torque, which is determined by the current speed of the motor 16, and the target braking torque of the cable winch 12, which is determined by the load 1 being lowered. The braking force is obtained from the current speed of the motor 16 or the lowering speed of the load 1 (cable winch 12).

[0051] According to the second modification, the braking torque for the controlled descent of the load 1 is first supplied via the hydraulic brake 30, during which the fan is kept inactive, and then gradually switched to the motor brake 18 after a short time (e.g., a few seconds). This switch is made after the speed of the winch motor 42 has stabilized.

[0052] Since the hydraulic brake system 30 is not used to brake the load 1 (or is used only after a short adjustment period), noisy cooling of the hydraulic oil is not required. However, the hydraulic brake system 30 can be activated for a short time to prevent changes in speed (sudden changes in conditions) and is used practically only for safety purposes. Furthermore, the hydraulic brake system 30 can function as a safety brake in the event of a failure of the motor brake 18 and / or as an auxiliary brake for braking when the motor brake 18 cannot provide sufficient braking torque.

[0053] According to a preferred embodiment (applicable to both of the above modifications), the prime mover 16 is a fuel-injected internal combustion engine, and the entire system is tuned so that when sufficient braking torque is transmitted to the prime mover brake 18, the controller 20 requests a braking torque from the prime mover brake 18 that is slightly greater than the torque required to reach the target braking torque. The high braking torque request causes the actual speed of the prime mover 16 to fall below the target speed. Subsequently, the injection to the prime mover 16 is activated. This results in a negative speed fluctuation from the target speed in the prime mover 16, averaging (stabilizing) the large braking torque of the prime mover brake 18, and setting the winch motor 42 to the desired braking torque or speed. By activating the injection, much higher control accuracy (stability of the prime mover speed and, consequently, the entire control loop) is achieved. In principle, only a very small amount of injection is required to average out the speed fluctuations. However, this is sufficient to ensure that the fuel injection located in the combustion chamber of the prime mover 16 is cooled.

[0054] The relevant control variables and signals are preferably exchanged between the components subject to open-loop and / or closed-loop control and the controller 20 via a CAN bus (dashed line in Figure 1).

[0055] The use of the motor brake 16 according to the present invention is not only applicable to hoist winches as shown in Figure 1, but is also applicable to other applications involving regenerative action (e.g., adjusting the winch to move the boom).

[0056] Figure 2 shows a flowchart of an exemplary embodiment of the method according to the present invention. In particular, the corresponding steps are performed by the controller 20 (excluding operator input).

[0057] In step S101, the lowering of load 1 is requested, for example, by a corresponding input from the operator using a master switch. A target braking torque for the cable winch 12 is required in order to lower load 1 by braking control.

[0058] In the next step 102, torque balancing is initiated based on the desired target braking torque of the cable winch 12 and the braking torque actually available to the braking device 18 of the prime mover 16.

[0059] In the next step 103, the torque balance is adjusted. For this purpose, the controller 20 determines the braking torque available to the cable winch 12. This braking torque consists of three torques: the braking torque generated by the transfer case 19 (static and independent of rotational speed), the friction torque of the internal combustion engine (static and independent of rotational speed), and the braking torque supplied by the braking device 18 of the prime mover 16 (which can be, for example, a brake flap) (variable as it depends on the prime mover speed).

[0060] In the following step 104, the controller 20 assigns the requested braking torque to the cable winch 12.

[0061] In the following step 105, the cable winch 12 is controlled (by corresponding control of the prime mover 16 that drives the cable winch 12 via the closed hydraulic circuit 40) and the load 1 begins to descend.

[0062] In the next step 106, the controller 20 checks whether the speed of the prime mover 16 exceeds the target speed. If it does not, the system proceeds directly to step S110 (see below). If it does exceed the target speed, the system proceeds to step S107.

[0063] In step S107, the controller 20 requests braking torque from the prime mover 16 or the braking device 18. The braking device 18 is operated to increase the braking torque supplied by the prime mover 16 (in one exemplary embodiment, the brake flap is further closed).

[0064] In the following step 108, the controller 20 checks whether the requested braking torque is less than the maximum available braking torque (which is determined in particular by the speed and characteristics of the braking device 18).

[0065] Otherwise, that is, if the required braking torque is greater than the maximum available braking torque, the braking torque required for braking cannot be obtained by the prime mover 16 (or prime mover brake 18) alone. Therefore, in step S122, the hydraulic brake system 30 is activated to increase the total braking torque supplied to the cable winch 12 and reach the target braking torque.

[0066] If the requested braking torque is less than the maximum available braking torque, step S109 is performed. Here, the controller 20 checks whether supplying the requested braking torque by the prime mover 16 will cause the speed of the prime mover to fall below the target speed. If it does not, the system returns to step S107 (further increasing the requested braking torque). If it does fall below the target speed, the system proceeds to step S110, at which point the braking torque supplied by the prime mover 16 is slightly greater than the braking torque required to reach the target braking torque required for the cable winch 12.

[0067] In step S110, the controller 20 activates the injection of the prime mover 16. This actively increases the speed of the prime mover, slightly reducing the braking torque of the internal combustion engine 16 and supplying the target braking torque to the cable winch 12.

[0068] As shown in the diagram, load 1 descends at a constant speed (or the cable winch 12 rotates at a constant motor speed). [Explanation of Symbols]

[0069] 1 load 10 Working Machines 11 Boom 12 Cable winches 14 Cables 15 Hydraulic Tank 16. Engine 17 Exhaust duct 18. Braking system (motorized brake) 19 Transfer Cases 20 controllers 21. First Control Unit 22 Second Control Unit 30 Hydraulic braking system 31 Brake pump 32 Pressure relief valve 33 Fan motor 34. Hydraulic pump (brake pump) 40 Closed hydraulic circuit 41 Hydraulic pump 42. Hydraulic motor (winch motor)

Claims

1. A work machine (10), particularly a crane, comprising a cable winch (12) capable of winding up a cable (14) to lift a load (1) and unwinding it to lower the load (1), a prime mover (16) capable of driving the cable winch (12), and a controller (20) capable of controlling the prime mover (16), wherein the prime mover (16) is equipped with a braking device (18) that generates a braking torque to resist externally generated torque, A work machine (10) is characterized in that, when the load (1) descends, the controller (20) controls the braking device (18) and the motor (16) in accordance with a predetermined target braking torque and the braking torque obtained by the motor (16), so that the load (1) descends at a predetermined, particularly constant speed.

2. In the working machine (10) described in claim 1, The prime mover (16) is an internal combustion engine, and the braking device (18) of the prime mover (16) preferably comprises an air vane located in the exhaust duct (17) and / or a throttle valve and / or a compression release brake located in the intake duct.

3. In the working machine (10) described in claim 1, The controller (20) is configured to form a target braking torque based on at least the detected current load, the current payout speed of the cable (14), the desired descent speed of the load (1), and / or the desired rotational speed of the work machine (10), and / or to determine the braking torque obtained by the prime mover (16) based on at least the detected current rotational speed of the prime mover (16).

4. In the working machine (10) described in claim 1, The controller (20) is configured to control the rotational speed to a target rotational speed in order to supply a target braking torque to the cable winch (12) when the load (1) is lowered, and the controller (20) is preferably configured to provide open-loop control and / or closed-loop control of the braking device (18) and to control at least one further prime mover parameter, in particular the rotational speed of the prime mover (16) via a fuel injection system of the work machine (10).

5. In the working machine (10) described in claim 1, The prime mover (16) is an internal combustion engine equipped with a fuel injection device, the controller (20) is configured to perform open-loop and / or closed-loop control of the braking device (18) such that the braking torque generated by the braking device (18) is greater than a target braking torque, and the controller (20) is configured to control the rotational speed, particularly the rotational speed of the prime mover (16), via the fuel injection device to equalize the greater braking torque of the braking device (18), preferably setting the target braking torque to the cable winch (12).

6. In the working machine (10) described in claim 1, The work machine (10) further comprises a hydraulic braking device (30) for braking the cable winch (12), which can be operated by the controller (20) as needed, either in place of or in parallel with the braking device (18) of the prime mover that generates braking torque for the cable winch (12), and the hydraulic braking device (30) comprises at least one hydraulic brake having a hydraulic pump (31) and, in particular, a pressure relief valve (32), and preferably at least one hydraulically operated cooling device for cooling the hydraulic oil.

7. In the working machine (10) according to claim 6, The controller (20) is configured to brake the descent of the load (1) via the hydraulic braking device (30) in a first braking stage, and in a subsequent second braking stage, to reduce the braking torque transmitted to the cable winch (12) by the hydraulic braking device (30), while increasing the braking torque transmitted to the cable winch (12) by the braking device (18) of the prime mover (16). The controller (20) is preferably configured to maintain a constant descent speed of the load (1) while the braking torque is transmitted from the hydraulic braking device (30) to the braking device (18) of the prime mover (16).

8. In the working machine (10) according to claim 6, The controller (20) is configured to brake the descent of the load (1) via the braking device (18) of the prime mover (16), and to temporarily activate the hydraulic braking device (30) only when the detected current load exceeds a predetermined limit value.

9. In the working machine (10) described in claim 1, The cable winch (12) is connected to the prime mover (16) via a transfer case (19), and is particularly drivable via a closed hydraulic circuit (40) connected between the transfer case (19) and the cable winch (12), and preferably a hydraulic brake (30) is connected to the transfer case (19) of the work machine (10).

10. In the working machine (10) described in claim 1, Furthermore, the work machine (10) is equipped with a detection device connected to the controller (20) to detect the current rotational speed and / or current load and / or current torque.

11. A method for lowering a load (1) using the work machine (10) described in claim 1, A method of controlling the motor (16) such that the load (1) descends at a predetermined, particularly constant speed, by controlling the braking device (18) based on a desired braking torque and the braking torque that can be supplied by the motor (16), wherein the controller (20) controls the motor (16).

12. In the method according to claim 11, A method in which the prime mover (16) is an internal combustion engine equipped with a fuel injection device, the controller (20) performs open-loop and / or closed-loop control of the braking device (18) such that the braking torque generated by the braking device (18) is greater than the target braking torque, and the controller (20) controls the speed of the prime mover (16) via the fuel injection device such that the greater braking torque of the braking device (18) is averaged out, and in particular the cable winch (12) sets the target braking torque.

13. In the method according to claim 11, A method in which the work machine (10) is equipped with a hydraulic braking device (30) for braking the cable winch (12), the controller (20) brakes the descent of the load (1) by the braking device (18) of the prime mover (16), and temporarily activates the hydraulic braking device (30) only when the detected current load exceeds a predetermined limit value.

14. In the method according to claim 11, The work machine (10) is equipped with a hydraulic braking device (30) for braking the cable winch (12), and the controller (20) brakes the descent of the load (1) in a first braking stage via the hydraulic braking device (30), and in a subsequent second braking stage, the controller (20) reduces the braking torque transmitted to the cable winch (12) by the hydraulic braking device (30) while simultaneously increasing the braking torque transmitted to the cable winch (12) by the braking device (18) of the prime mover (16), and preferably maintains a constant descent speed of the load (1) while the braking torque is being transmitted from the hydraulic braking device (30) to the braking device (18) of the prime mover (16).

15. A computer program product, A computer program, when executed, that causes the work machine (10) according to claim 1 to perform the step of controlling the motor (16) so that the load (1) descends at a predetermined speed by controlling the braking device (18) based on a desired braking torque and the braking torque that can be supplied by the motor (16).

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