Work machine with prime mover brake, particularly crane

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]

[0001] The present invention relates to a work machine, in particular a crane, according to the preamble of claim 1, a method for lowering a load by means of said work machine and a corresponding computer program product. [Background technology]

[0002] Many work machines use powered cable winches (electric cable winches) to lift loads. This includes moving heavy machine components such as booms or bracing frames with cable winches, e.g., bracing cables or adjustable winches (the machine's own load), or lifting an object to be moved by the work machine with a hoist rope winch (external load). Loads are typically lowered by unwinding (releasing, paying out) the cable connected to the load via the cable winch. To prevent the load from descending uncontrollably due to excessive kinetic energy caused by its own weight, the process of lowering the load or the corresponding cable unwinding must be braked in a controlled manner.

[0003] Braking is usually achieved by converting the potential energy of the load into heat as it is lowered. In the prior art, it is known to convert the braking force required to lower the load into heat using hydraulic systems. This can be achieved by selectively activating hydraulic consumers, such as hydraulic fan drives. Hydraulic brakes are usually used, with one or more brake pumps specifically designed for the braking process. The brake pumps can be supplied with a large hydraulic flow at the corresponding pressure stage to generate the required braking force. The braking energy absorbed by the brake pumps is converted into heat at that pressure stage, heating the hydraulic oil. This heat must be dissipated by hydraulic coolers or fans. For this purpose, fans rotate at 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 usually designed so that the winch motor always provides a positive torque. This principle allows good to very good control quality with little effort, but requires fuel consumption in the descending mode. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention therefore addresses the problem of being able to brake and lower loads in a controlled manner in a typical work machine, overcoming the above-mentioned drawbacks, reducing noise pollution and reducing fuel consumption. [Means for solving the problem]

[0006] According to the present invention, this object is achieved by a working machine with the features of claim 1, a method with the features of claim 11 and a computer program product with the features of claim 15. Advantageous embodiments of the invention are set out in the dependent claims and the following description.

[0007] Therefore, according to one aspect of the present invention, a work machine is proposed that includes a cable winch, a prime mover that drives the cable winch, and a controller that controls the prime mover. The controller may include multiple control units or control devices that are communicatively connected to each other, or may be a single control unit. In principle, the work machine can be mobile (e.g., a crawler crane, a rail crane, a mobile crane) or fixed (e.g., a tower crane, a harbor crane).

[0008] A cable for lifting and lowering a load is attached to the cable winch so that it can be hoisted 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 to a component of the work machine such as a pivotally mounted boom or bracing frame. In the former case, the cable winch is in particular a hoist rope winch and the cable is a hoist rope. In the latter case, the cable winch may also be an adjusting winch that can be part of a bracing cable for moving said component.

[0009] In particular, the prime mover is an internal combustion engine, for example a diesel engine. In addition to driving the cable winch, the prime mover may also function as a traction drive for propelling the work machine. The prime mover is equipped with a braking device, also called a prime mover brake, which generates a braking torque that opposes an externally generated torque. In particular, the braking device can be actively activated, for example by activating a corresponding switch element in the work machine's cab. The braking device can be activated or controlled by a controller. In this example, the term "control" can mean both open-loop control and closed-loop control (including a comparison of a target value with an actual value).

[0010] The internal combustion engine can also be replaced by an electric motor, in which case the braking device must be replaced by a corresponding one, which can be, for example, an electrical resistor.

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

[0012] The basic idea of the present invention is therefore to slow down the load using the prime mover brake, and for this purpose the prime mover is controlled to achieve a predetermined lowering speed of the load. Most prime movers installed in conventional work machines are configured as internal combustion engines already equipped with a prime mover brake (which is, however, used as a brake for the traveling operation), so that there is no need for a time-consuming retrofit (modification) of existing machines.

[0013] Using prime mover brakes to control the deceleration of a cable winch or load can completely or significantly reduce the use of hydraulic brakes. Noisy fans to cool the hydraulic oil are no longer needed, significantly reducing the overall noise output of the equipment. Furthermore, traditional prime mover brakes are truly continuous brakes that can be used for very long periods of time without loss of braking power due to high oil temperatures.

[0014] Using the prime mover brake to slow the load has additional benefits. The entire prime mover compartment is subjected to reduced heat load from the hot exhaust of the fan. Specifically, energy is converted into compression work and / or decompression work and is expelled from the prime mover through the exhaust system instead of the hydraulic cooler. Furthermore, because 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, using the prime mover brake in descent mode reduces fuel consumption because the prime mover reaches the desired speed with no or minimal fuel injection.

[0015] In one embodiment, the prime mover is an internal combustion engine, for example a spark ignition engine (gasoline engine), or preferably a diesel engine. The brake of the prime mover can consist of an air vane arranged in the exhaust duct of the prime mover and / or a throttle valve arranged in the intake duct of the prime mover. The corresponding valve is further closed to increase the braking torque. Alternatively or additionally, the prime mover may be equipped with a decompression brake (also known in English as a "Jacobs brake" or "Jake brake"). In particular, the brake may be the well-known prime mover brake used in conventional internal combustion engines. Preferably, the prime mover also functions as a drive device for the work machine, and the brake, in addition to its function of braking the load descent speed in the present invention, can also be used to reduce the travel speed in a known manner.

[0016] In a further possible embodiment, the controller can be configured to determine the target braking torque based on at least the detected current load, the current cable payout rate (winding rate), the desired load lowering rate, and / or the desired rotational speed, e.g., the desired rotational speed of the cable winch and / or prime mover. The current load can be detected by a sensing device on the work machine and made available to the controller. To this end, the sensing device can include one or more sensors for measuring the current load. The greater the detected load, the greater the target braking torque required to achieve a particular lowering speed. The current cable (e.g., the hoist cable of a hoist winch or the guy cable of an adjusting winch) payout rate can also be detected by a sensor or manually preset by the work machine operator via input means. The desired lowering rate or desired rotational speed can be automatically determined by the controller using other parameters and / or manually preset by the work machine operator using input means (e.g., a master switch).

[0017] Alternatively, or in addition, the controller may be configured to determine the actual available braking torque at the prime mover based at least on the detected current speed of the prime mover (i.e., the available braking torque may be speed dependent), which may depend on the characteristics and configuration of the braking device and / or the prime mover.

[0018] In yet another possible embodiment, it is proposed to configure the controller to control the rotational speed, in particular 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 an externally generated torque may include, in addition to influencing the braking device (i.e., control by open-loop control and / or closed-loop control), effective control of the prime mover by at least one further parameter of the prime mover, such as, for example, fuel injection in order to generate an effective prime mover torque counteracting the braking torque generated by the braking device. This improves the accuracy of the control of the prime mover speed and thus the accuracy of the load descent speed.

[0019] The target speed may refer to the speed of the prime mover. However, the target speed can 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 the prime mover speed, or it may be different (e.g., because the cable winch is coupled to the prime mover via a gearing and / or hydraulic circuit). It is also conceivable that the relevant control variable of the control circuit is the prime mover speed, and the target speed converts from the desired winch rotational speed to the corresponding prime mover speed. In general, the winch motor speed can be converted to the prime mover speed, and vice versa, since they are linked via the properties of intervening components, such as gearing. It should be noted at this point that when the terms "prime mover" or "prime mover speed" are used, they always refer to the prime mover with its braking device.

[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 braking device in an open-loop and / or closed-loop manner so that the braking torque generated by the braking device is greater than the target braking torque. In other words, the controller specifically requests a braking torque from the prime mover that is greater than the braking torque required to achieve a specified descent speed. This causes the actual speed of the prime mover to fall below the target speed. To correct this effect, the controller is configured to activate the fuel injection and control the braking device to equalize the greater braking torque (or the reduction in prime mover speed) and set the target torque of the prime mover or the target braking torque of the cable winch. Since the required braking torque is preferably only slightly greater than the required value, only a small amount of fuel injection is required for equalization. However, even this small amount of fuel injection is sufficient to reliably cool the fuel injection nozzle located in the combustion chamber of the internal combustion engine.

[0021] By activating the injection, a very high control accuracy is achieved for the prime mover speed and the stability of the entire control loop is improved. This contributes significantly to the stability of the entire system, especially in the case of long signal transmission cycle times (e.g. request, feedback via CAN bus). Without injection, the entire system, winch speed and load may oscillate.

[0022] In yet another possible embodiment, the work machine includes a hydraulic brake for braking the cable winch or load that can be activated by the controller as needed in place of or in parallel with the brake on the prime mover to generate a braking torque for lowering the load. The hydraulic brake converts energy into heat to generate a braking torque for the prime mover (i.e., prime mover 16) or cable winch connected to the hydraulic brake.

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

[0024] In yet another possible embodiment, the controller is configured to fully or partially brake the lowering of the load via the hydraulic brake in a first braking stage, and to continuously or stepwise decrease the braking torque transmitted to the cable winch by the hydraulic brake in a subsequent second braking stage, while continuously or stepwise increasing the braking torque transmitted to the cable winch by the prime mover brake. Preferably, the controller is configured to keep the load lowering speed or the prime mover rotational speed constant during transmission of the braking torque from the hydraulic brake to the prime mover brake.

[0025] In this variant, braking, i.e., control to the target speed, is initially performed exclusively via the hydraulic brake (i.e., the prime mover brake is deactivated). Then, preferably as soon as the speed has stabilized, the braking torque is continuously transmitted from the hydraulic brake to the prime mover brake. In the third braking phase, the braking torque is preferably provided exclusively by the prime mover brake, which is only temporarily activated if the detected current load exceeds a defined limit (speed anomaly prevention) or if the prime mover brake fails. Preferably, the first braking phase is sufficiently short (e.g., less than 20 seconds, preferably less than 10 seconds) so that the hydraulic oil does not heat up so much that it is necessary to activate the fan. This avoids noise pollution due to the operation of the fan.

[0026] In a possible alternative embodiment, the prime mover brake is responsible for the braking torque for braking the load descent from the beginning, particularly exclusively (i.e. the hydraulic brake of the prime mover is deactivated from the beginning). In this variant too, the hydraulic brake can be temporarily switched on if the detected current load exceeds a defined limit value and / or as a backup in case of failure of the prime mover brake.

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

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

[0029] In yet another possible embodiment, it is proposed that the work machine comprises a detection device connected to the controller for detecting the current rotational speed, in particular 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 (e.g. acting on the cable winch or the winch motor). The detection device may comprise one or more sensors for detecting the aforementioned variables.

[0030] In yet another possible embodiment, the work machine is configured as a mobile crane with a boom (e.g., a lattice boom or a telescoping boom) and a hoist rope guided above the boom head. A load slinging device (e.g., a hoist block) is attached to the hoist rope, to which a load to be lifted can be attached. The cable winch that can be braked by the prime mover brake can be a hoist rope winch that reels in the hoist rope. It is also conceivable that the crane has a boom or bracing frame (e.g., an A-frame or derrick boom) that can perform luffing movements using an adjusting winch and a corresponding cable, and the cable winch that can be braked by the prime mover brake is the adjusting winch. The crane can have a movable undercarriage and an upper structure with a boom rotatably attached to the undercarriage structure. The controller can be (or include) a crane controller.

[0031] In another possible embodiment, communication or signal transmission between the controller and the prime mover or brake (and between the control units of the controller, if provided) takes place via a bus, in particular a CAN bus, with all relevant control variables and signals being exchanged via this bus.

[0032] According to a second aspect, the present invention relates to a method for lowering a load by means of a work machine according to the present invention, in which, as already explained in relation to the work machine according to the present invention, the controller controls the prime mover so that the load is lowered at a predetermined, in particular constant, speed by controlling the brake device in accordance with a target braking torque and the braking torque actually obtained by the prime mover. This control is preferably carried out in particular in relation to the speed of the prime mover or winch motor. This provides the same advantages, features and variants as already explained in relation to the work machine according to the present invention, so that a repeated explanation will be omitted.

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

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

[0035] In a possible alternative embodiment, the work machine is equipped with a hydraulic brake for braking the cable winch, and the controller fully or partially brakes the lowering of the load via the hydraulic brake in a first braking phase, and then in a second braking phase, the controller continuously or stepwise reduces the braking torque transmitted to the cable winch by the hydraulic brake and simultaneously continuously or stepwise increases the braking torque transmitted to the cable winch by the prime mover brake, preferably keeping the load lowering speed constant during the transmission of the braking torque from the hydraulic brake to the prime mover brake. This variant involves a gradual transfer of the braking torque from the hydraulic brake to the prime mover brake. This transfer 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, the payout speed, the desired load lowering speed and / or the desired winch speed for the lowering.

[0036] The present invention also relates to a computer program product comprising instructions which, when executed, cause the working machine according to the present invention to carry out the steps of the method according to the present invention, in particular by the controller. Of course, this only relates to steps which can be carried out automatically, in particular by the controller, as described above. This provides the same advantages, properties and embodiments as the working machine according to the present invention, as already described, so that a repetitive description will be omitted.

[0037] Further applications of the solution according to the invention are conceivable, such as for example adjusting winches for booms or travel drives for crawler chassis.

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

[0039] [Figure 1] FIG. 1 shows a schematic side view of a work machine according to an example embodiment of the present invention. [Figure 2] FIG. 2 shows a flow chart of an example embodiment of a method according to the present invention for lowering a load. DETAILED DESCRIPTION OF THE INVENTION

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

[0041] This crawler crane 10 has a boom 11 pivotally mounted on the superstructure. The boom can be raised and lowered (luffing) by operation of a bracing cable (not shown) and an adjustment winch (not shown). A cable 14 (hoist rope) is attached to a cable winch 12 (hoist rope winch) located on the superstructure so that it can be wound up and unwound, and supports a load hoisting 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, which drives a hydraulic motor 42 that functions as a winch motor.

[0043] The hydraulic pump 41 and / or hydraulic motor 42 are adjusted as desired by the operator to lower the load, for example by a master switch, thereby unwinding (paying 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] 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 be configured as a hydraulic pump 31 (brake pump) that can be driven by the prime mover 16, and a hydraulic brake that includes a pressure relief valve 32 as a pressure stage (pressure regulating stage).

[0045] To limit the speed of the load 1 as it descends, the hydraulic brake device 30 can be activated to generate a braking torque acting on the winch motor 42 or the cable winch 12 to slow down the descent speed. For this purpose, the control unit 21 controls the brake pump 31 to generate a flow through the pressure relief valve 32, thereby generating a braking force. The pressure relief valve 32 can also be controlled by the control unit 21. During prolonged operation of the hydraulic brakes, the hydraulic oil heats up and therefore needs to be cooled by a cooling device. In the exemplary embodiment shown in FIG. 1, the hydraulic brake device 30 comprises 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 device 30 is taken from the hydraulic tank 15 (open hydraulic circuit).

[0046] The prime mover 16 is provided with a braking device 18 (hereinafter also referred to as prime mover brake) for counteracting an externally applied torque (e.g., a torque generated by the lowering of the load 1 due to gravity and transmitted to the prime mover 16 via the cable winch 12, the hydraulic circuit 40, and the transfer case 19). As in the exemplary embodiment of FIG. 1, the prime mover 16 may be configured as a diesel engine with an exhaust duct 17 in which air vanes 18 are arranged as a braking device. Alternatively or additionally, a throttle valve may be provided in the intake duct of the spark-ignition engine, or a compression release brake may be provided.

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

[0048] In accordance with the present invention, the hydraulic brake 30 is not used (at least not exclusively) to brake the load 1 during lowering; instead, the prime mover brake 18 is used. The speed of the winch motor 42 is controlled by the controller 20 of the work machine 10 to obtain the required braking torque. In the exemplary embodiment shown, 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 prime mover and brake 18 and is connected to the first control unit 21 (signal and control connections are shown in dashed lines in FIG. 1 ). The second control unit 22 could also be a prime mover control unit and part of the prime mover 16. Instead of two control units 21, 22, three or more control units, or even just a single control unit that also controls the prime mover 16 and brake 18, could be provided.

[0049] The controller 20 determines a target braking torque for the cable winch 12 from the detected load, the payout speed of the hoist cable 14 taken into account, and the target speed of the cable winch 12 (or winch motor 42), which results in a predetermined, in particular constant, speed of the load 1 during controlled descent. Furthermore, a currently available speed-dependent braking torque for 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, which then performs the actual control.

[0050] According to a first variant, the braking torque for lowering the load 1 is provided from the start by the prime mover brake 18. The controller 20 establishes a torque balance between the available prime mover braking torque, which depends on the current speed of the prime mover 16, and the target braking torque of the cable winch 12, which depends on the lowering load 1. The braking force is derived from the current speed of the prime mover 16 or the lowering speed of the load 1 (cable winch 12).

[0051] According to a second variant, the braking torque for the controlled lowering of the load 1 is first supplied via the hydraulic brake 30, the fan being kept inactive during this initial braking phase, and then, after a short period (for example a few seconds), gradually switches over to the prime mover brake 18. This switchover takes place after the speed of the winch motor 42 has stabilized.

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

[0053] According to a preferred embodiment (applicable to both of the above-mentioned variants), the prime mover 16 is a fuel-injected internal combustion engine, and the entire system is adjusted 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. The injection to the prime mover 16 is then activated. This causes negative speed fluctuations from the target speed in the prime mover 16, averaging (leveling) the large braking torque of the prime mover brake 18 and setting the desired braking torque or speed for the winch motor 42. By activating the injection, much higher control accuracy (prime mover speed and thus stability of the entire control loop) is achieved. In principle, only small injection volumes are required to average out the speed fluctuations. However, these are sufficient to ensure cooling of the fuel injections located in the combustion chamber of the prime mover 16.

[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 FIG. 1).

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

[0056] 2 shows a flow chart of an exemplary embodiment of the method according to the invention, in particular the corresponding steps being executed by the controller 20 (excluding operator input).

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

[0058] In the next step 102 , torque balancing is initiated between the desired target braking torque of the cable winch 12 and the braking torque actually available by 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 is made up 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 provided 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 a following step 104 , the controller 20 allocates 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 which drives the cable winch 12 via the closed hydraulic circuit 40) so that the load 1 starts to lower.

[0062] In the next step S106, controller 20 checks whether the speed of prime mover 16 exceeds the target speed. If not, it proceeds directly to step S110 (see below). If yes, the system proceeds to step S107.

[0063] In step S107, controller 20 requests braking torque from prime mover 16 or brake 18. Brake 18 operates to increase the braking torque provided by prime mover 16 (in one exemplary embodiment, further closing the brake flaps).

[0064] In a following step 108, the controller 20 checks whether the requested braking torque is less than the maximum braking torque available (which depends, among other things, on the speed and characteristics of the braking device 18).

[0065] If this is not the case, i.e., if the requested braking torque is greater than the maximum available braking torque, the braking torque required for braking cannot be provided by the prime mover 16 (or prime mover brake 18) alone, and therefore, in step S122, the hydraulic braking device 30 is activated to increase the total braking torque supplied to the cable winch 12 until the target braking torque is reached.

[0066] If the requested braking torque is less than the maximum available braking torque, step S109 is executed. Here, controller 20 checks whether the supply of the requested braking torque by prime mover 16 will cause the prime mover speed to fall below the target speed. If not, the system returns to step S107 (further increasing the requested braking torque). If so, the system proceeds to step S110, where the braking torque supplied by prime mover 16 is slightly greater than that required to reach the target braking torque requested of 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 providing the target braking torque to the cable winch 12.

[0068] The control shown causes the load 1 to descend at a constant speed (or the cable winch 12 to rotate at a constant prime mover speed). [Explanation of symbols]

[0069] 1 load 10. Work Machinery 11. Boom 12 Cable winch 14 Cable 15 Hydraulic tank 16 Prime Mover 17 Exhaust duct 18 Braking device (motor brake) 19 Transfer case 20 Controller 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 provided with a braking device (18) that generates a braking torque that resists an externally generated torque, The working machine (10) is configured such that, when the load (1) descends, the controller (20) controls the brake device (18) and the prime mover (16) in accordance with a predetermined target braking torque and a braking torque obtained by the prime mover (16), so that the load (1) descends at a predetermined, particularly constant, speed.

2. 2. A work machine (10) according to claim 1, The working machine (10) is configured such that the prime mover (16) is an internal combustion engine, and the braking device (18) of the prime mover (16) preferably includes an air vane arranged in an exhaust duct (17) and / or a throttle valve and / or a compression release brake arranged in an intake duct.

3. A work machine (10) according to claim 1 or 2, The controller (20) is configured to generate a target braking torque based on at least the detected current load, the current payout rate of the cable (14), the desired lowering rate and / or the desired rotational speed of the load (1), and / or to determine a braking torque to be provided by the prime mover (16) based on at least the detected current rotational speed of the prime mover (16).

4. A work machine (10) according to any one of claims 1 to 3, The controller (20) is configured to control the rotational speed to a target rotational speed in order to provide 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 and / or closed-loop control of the braking device (18) and to control the rotational speed of the prime mover (16) via at least one further prime mover parameter, in particular a fuel injection system.

5. A work machine (10) according to any one of claims 1 to 4, The working machine (10) is configured such that the prime mover (16) is an internal combustion engine equipped with a fuel injection device, the controller (20) performs open-loop control and / or closed-loop control of the braking device (18) so that the braking torque generated from the braking device (18) is greater than a target braking torque, and the controller (20) controls the rotational speed, in particular the rotational speed of the prime mover (16) via the fuel injection device to equalize the greater braking torque of the braking device (18) and preferably set the target braking torque for the cable winch (12).

6. A work machine (10) according to any one of claims 1 to 5, 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 instead of or in parallel with the prime mover braking device (18) for generating a braking torque on the cable winch (12), and the hydraulic braking device (30) comprises at least one hydraulic brake with a hydraulic pump (31) and in particular a pressure relief valve (32), and preferably at least one hydraulically operated cooling device for cooling hydraulic oil.

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

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

9. A work machine (10) according to any one of claims 1 to 8, The cable winch (12) is connected to the prime mover (16) via a transfer case (19) and is drivable, in particular, via a closed hydraulic circuit (40) connected between the transfer case (19) and the cable winch (12), and preferably a hydraulic braking device (30) is connected to the transfer case (19).

10. A work machine (10) according to any one of claims 1 to 9, The work machine (10) further comprises a detection device connected to the controller (20) for detecting a current rotational speed and / or a current load and / or a current torque.

11. A method for lowering a load (1) using a work machine (10) according to any one of claims 1 to 10, comprising the steps of: The controller (20) controls the brake device (18) based on a desired braking torque and a braking torque that can be supplied by the prime mover (16), thereby controlling the prime mover (16) so that the load (1) descends at a predetermined, particularly constant, speed.

12. 12. The method of claim 11, The method includes: the prime mover (16) being an internal combustion engine equipped with a fuel injection device; the controller (20) performing open-loop control and / or closed-loop control of the brake device (18) so that the braking torque generated by the brake device (18) is greater than the target braking torque; and the controller (20) controlling the speed of the prime mover (16) via the fuel injection device so that the greater braking torque of the brake device (18) is averaged, and in particular the target braking torque is set at the cable winch (12).

13. 13. The method of claim 11 or 12, The method includes the work machine (10) including a hydraulic brake (30) for braking the cable winch (12), and the controller (20) brakes the descent of the load (1) using a brake (18) of the prime mover (16), and temporarily activates the hydraulic brake (30) only when the detected current load is a load that exceeds a predetermined limit value.

14. 13. The method of claim 11 or 12, The work machine (10) is provided with a hydraulic braking device (30) for braking the cable winch (12), and the controller (20) brakes the descent of the load (1) via the hydraulic braking device (30) in a first braking stage, 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) and simultaneously increases the braking torque transmitted to the cable winch (12) by the braking device (18) of the prime mover (16), and the descent speed of the load (1) is preferably kept constant during the transmission of the braking torque from the hydraulic braking device (30) to the braking device (18) of the prime mover (16).

15. 1. A computer program product comprising: A computer program product comprising instructions which, when executed, cause a work machine (10) according to any one of claims 1 to 10 to perform the steps of the method according to any one of claims 11 to 14.

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