crane

Abstract

To improve the operability of the crane during freefall. [Solution] A crane (100) has a free-fall function that drops the suspended load by gravity, comprising a winch drum (5) for raising and lowering a suspended load, a brake device (4) for braking the rotation of the winch drum, and an operating means (20) for operating the brake device, and is equipped with a rotation sensor (10) for detecting the rotational speed of the winch drum, and controls the braking force of the brake device so that the difference between the operating state of the operating means and the rotational speed of the winch drum detected by the rotation sensor becomes small during the period when the free-fall function is active.

Description

Technical Field

[0001] The present invention relates to a crane.

Background Art

[0002] A crawler crane has a free-fall function for allowing a suspended load to fall by gravity. During free fall, an operator operates a brake pedal to adjust the descending speed of the suspended load. As a control method for brake characteristics, a method using a hydraulic pilot valve has been conventionally known, but in recent years, a method using an electric pedal and a proportional valve has also become known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above conventional technology, during free fall, an operator needs to visually adjust the descending speed of the suspended load. For example, when the suspended load is heavy and when it is light, the operator must adjust the braking force while visually checking the descending speed of the suspended load. Therefore, there is room for improvement in the operability of the crane.

[0005] An object of the present invention is to improve the operability of a crane during free fall.

Means for Solving the Problems

[0006] To achieve the above objective, one aspect of the present invention provides a crane having a free-fall function that causes a suspended load to fall by gravity, comprising a winch drum for raising and lowering a suspended load, a braking device for applying a brake to the rotation of the winch drum, and an operating means for operating the braking device, wherein the crane is equipped with a rotation sensor for detecting the rotational speed of the winch drum, and the braking force of the braking device is controlled so as to reduce the difference between the operating state of the operating means and the rotational speed of the winch drum detected by the rotation sensor during the period in which the free-fall function is effective.

[0007] According to the present invention, the operability of the crane in freefall can be improved. Other problems, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0008] [Figure 1] This is an external side view of the crane. [Figure 2] This is a diagram showing the brake configuration of the main winch. [Figure 3] This is a block diagram showing the control configuration of the braking system. [Figure 4] This is a block diagram showing the control configuration of the brake device according to modified example 1. [Figure 5] This is a block diagram showing the control configuration of the brake device according to modified example 2. [Figure 6] This is a block diagram showing the control configuration of the brake device according to modified example 3. [Figure 7] This is a block diagram showing the control configuration of the brake device according to modified example 4. [Modes for carrying out the invention]

[0009] Hereinafter, a crane according to an embodiment of the present invention will be described with reference to the drawings.

[0010] Figure 1 is an external side view of a crane according to an embodiment. The crane 100 shown in Figure 1 is a crawler crane and comprises a traveling body 102, a slewing body 104 rotatably mounted on the traveling body 102 via a slewing device 103, a boom 105 rotatably attached to the tip of the slewing body 104, and sheaves 110, 111 and sheaves 117, 118 provided at the tip of the boom 105. A bucket 116, which is an example of an attachment, is suspended by a main hoisting rope 112 via sheaves 110 and 117, and an auxiliary hoisting rope 113 via sheaves 111 and 118. Of course, in addition to the bucket 116, other loads and such can also be lifted.

[0011] The slewing body 104 is equipped with a cab 109. The cab 109 is equipped with various operating levers (main hoisting lever 23 (see Figure 5), auxiliary hoisting lever, luffing lever, travel lever, slewing lever, etc.), and the user operates these levers to perform lifting operations, excavation operations, slewing operations, and travel operations of the crane 100. Buttons or dials may be used instead of the various operating levers. The cab 109 is also equipped with a display device (not shown) for displaying various information such as the operating status and warnings of the crane 100, and a controller 80 for controlling the operation of the crane 100 (see Figure 2).

[0012] The main hoisting rope 112 and the auxiliary hoisting rope 113 are wound around the main hoisting winch 106 and the auxiliary hoisting winch 107, respectively, mounted on the slewing body 104. By driving the winches 106 and 107, the ropes 112 and 113 are wound up or unwound, raising or lowering the suspended load. The bucket 116 can be lowered by suspending it with the main hoisting rope 112 and the auxiliary hoisting rope 113 and simultaneously driving the main hoisting winch 106 and the auxiliary hoisting winch 107. When lifting or lowering a load, either the main hoisting winch 106 or the auxiliary hoisting winch 107 can be used.

[0013] A pendant rope 114 is connected to the tip of the boom 105, and when the luffing winch 108 mounted on the slewing body 104 drives the luffing rope 115 in or out, the boom 105 is raised and lowered via the pendant rope 114.

[0014] Next, the configuration of the braking device according to the embodiment will be described. As mentioned above, the crane 100 is equipped with a main hoisting winch 106, an auxiliary hoisting winch 107, and a luffing winch 108, and each of the winches 106, 107, and 108 is equipped with a braking device of the same mechanism. Therefore, in the following description, the braking device of the main hoisting winch 106 will be described, and the description of the other braking devices will be omitted.

[0015] Figure 2 is a diagram showing the configuration of the main hoist winch. As shown in Figure 2, the main hoist winch 106 comprises a hydraulic motor 1, a brake device 2, a reduction gear 3, a brake device 4, a winch drum 5, and a rotation sensor 10.

[0016] The main hoisting winch 106 is equipped with a free-fall function. A brake device 2 is connected to one output shaft of the hydraulic motor 1, and a brake device 4 is connected to the other output shaft (the output shaft on the reduction gear 3 side). Brake devices 2 and 4 use a negative control system that applies a brake to the hydraulic motor 1 when not in operation. When the load is stopped, both brake devices 2 and 4 are engaged (brake state), and both brake devices 2 and 4 hold the load. When the load is hoisted up or down, brake device 2 is released and brake device 4 is engaged, transmitting power from the hydraulic motor 1 to the winch drum 5. When the load is free-falling, brake device 2 is engaged, and the descent speed of the load is controlled by adjusting the braking force of brake device 4. In other words, brake device 2 functions as a clutch device, brake device 4 functions as a clutch device when the load is stopped, hoisted up, and lowered, and functions as a brake device when the load is free-falling.

[0017] The free fall function becomes effective when the operator steps on a pedal provided inside the cab 109. This pedal may be combined with the brake pedal 20 or may be provided separately from the brake pedal 20. In the case of combination, by releasing a predetermined lock mechanism and the operator stepping on the brake pedal 20, the free fall function becomes effective. Of course, instead of the pedal, a configuration may be adopted in which the free fall function is activated by an operating means such as a button or a switch.

[0018] Incidentally, since the main winch 106 has a free fall function, it is provided with the brake device 2 and the brake device 4. However, when it does not have a free fall function, it is not necessary to provide the brake device 4.

[0019] The brake device 4 is a wet multi-plate type and includes a plurality of friction plates. When the plurality of friction plates are pressed and contacted by the biasing force of a pressing spring, it is in a braking state, and when the biasing force by the pressing spring disappears, the braking state is released. The same applies to the brake device 2.

[0020] FIG. 3 is a block diagram showing the control configuration of the brake device 4.

[0021] As shown in FIG. 3, the operation of the brake device 4 is controlled by the controller 80. That is, the controller 80 is responsible for controlling the braking force of the brake device 4.

[0022] The controller 80 includes, although not shown, a CPU that performs various operations, a storage device such as a ROM or an HDD that stores programs for the CPU to execute operations, a RAM that serves as a work area when the CPU executes programs, and a communication interface that is an interface for transmitting and receiving data to and from other devices. It is composed of hardware including a communication interface and software stored in the storage device and executed by the CPU. Each function of the controller 80 is realized by the CPU loading various programs stored in the storage device into the RAM and executing them.

[0023] The input side of the controller 80 is connected to a brake pedal 20, a speed adjustment switch 21, and a speed setting dial 22. The brake pedal 20, speed adjustment switch 21, and speed setting dial 22 are located inside the cab 109 and can be operated by the operator.

[0024] The brake pedal 20 is an operating means for activating the brake device 4. When the operator presses down on the brake pedal 20, the rotational speed of the winch drum 5 of the main hoist winch 106 is reduced. The brake pedal 20 is an electric pedal. The amount V1 pressed down on the brake pedal 20 is converted into an electrical signal and input to the controller 80. Alternatively, a hydraulic brake pedal may be used instead of an electric pedal. In this case, the hydraulic fluid pressure signal should be input to the controller 80.

[0025] The speed adjustment switch 21 is a push-button type, and the rotation speed of the winch drum 5 can be adjusted according to the length of time the push button is pressed. Of course, other types of switches may also be used. The speed adjustment switch 21 is also an example of an operating means for activating the brake device 4.

[0026] The speed setting dial 22 is a volume control for setting the upper limit of the rotational speed of the winch drum 5. Turning the volume control to a predetermined position sets the upper limit of the rotational speed of the winch drum 5 corresponding to that position.

[0027] Alternatively, instead of using the speed setting dial 22, the operator may input a numerical value for the upper limit speed, or the operator may select an arbitrary upper limit speed from a predetermined set of upper limit speeds (setting modes). In other words, any means can be used as long as the upper limit speed of the winch drum 5 can be set by a predetermined operation. For example, in the case of a configuration where the operator inputs a numerical value for the upper limit speed or selects a setting mode, it would be convenient to provide a touch panel for numerical input or speed selection inside the cab 109.

[0028] An electromagnetic proportional valve 15 is connected to the output side of the controller 80. The electromagnetic proportional valve 15 opens to an opening degree corresponding to the opening degree command Vout, introducing pressurized oil from the hydraulic power source 12 to the brake device 4. The brake device 4 adjusts the contact force of the friction plates described above using the introduced pressurized oil to provide the desired braking force to the rotation of the winch drum 5. In Figure 3, reference numeral 11 denotes a tank for storing hydraulic fluid.

[0029] The controller 80 includes a target rotational speed setting unit 30, an upper limit speed setting unit 31, a first-order lag processing unit 32, a speed deviation calculation unit 33, and a proportional valve output unit 34.

[0030] The target rotational speed setting unit 30 sets the target rotational speed Vt of the winch drum 5 based on the amount of depression V1 of the brake pedal 20 or the on / off signal V2 of the speed adjustment switch 21. In this embodiment, the target rotational speed Vt is output to the upper limit speed setting unit 31 such that the target rotational speed Vt decreases (the braking force increases) as the amount of depression V1 increases or the on time of the on / off signal V2 increases.

[0031] The upper speed limit setting unit 31 determines whether the input target rotational speed Vt exceeds the upper speed limit Vu set by the speed setting dial 22. If the target rotational speed Vt is less than or equal to the upper speed limit Vu, it outputs the target rotational speed Vt to the first-order lag processing unit 32. On the other hand, if the target rotational speed Vt exceeds the upper speed limit Vu, it outputs the upper speed limit Vu as the target rotational speed Vt to the first-order lag processing unit 32.

[0032] The first-order lag processing unit 32 performs a first-order lag process on the input target rotational speed Vt and outputs it to the speed deviation calculation unit 33. The first-order lag processing unit 32 is, for example, a low-pass filter. The target rotational speed Vt is smoothed by the first-order lag processing unit 32 and then output to the speed deviation calculation unit 33. The characteristics (time constant) of the first-order lag can be arbitrarily determined according to the crane operation.

[0033] The speed deviation calculation unit 33 calculates the speed deviation ΔV between the actual rotational speed Vm input from the rotation sensor 10 provided on the winch drum 5 and the target rotational speed Vt input from the first-order lag processing unit 32. The speed deviation calculation unit 33 then outputs the speed deviation ΔV to the proportional valve output unit 34.

[0034] The proportional valve output unit 34 outputs an opening command Vout to the electromagnetic proportional valve 15 based on the input speed deviation ΔV. The electromagnetic proportional valve 15 opens (operates) with an opening degree corresponding to the speed deviation ΔV between the actual rotational speed Vm from the rotation sensor 10 and the amount V1 pressed down on the brake pedal 20 (or the on / off signal V2 from the speed adjustment switch 21) and the target rotational speed Vt. In other words, in this embodiment, the opening command Vout is fed back to the controller 80 as the actual rotational speed Vm of the winch drum 5, and the rotational speed of the winch drum 5 is controlled (the braking force is controlled) to approach the target rotational speed Vt. Therefore, the winch drum 5 is automatically controlled to a rotational speed corresponding to the amount pressed down on the brake pedal 20 (or the on / off operation of the speed adjustment switch 21). That is, the controller 80 automatically controls the rotational speed of the winch drum 5 to match the operator's operation.

[0035] In the crane 100 configured in this way, the following is a summary of the operator's operation of the brake pedal 20 and the change in the rotational speed of the winch drum 5 when the operator free-falls the suspended load.

[0036] (Start of descent of suspended load ~ first half of descent) First, the operator presses the freefall pedal to activate the freefall function. Then, the operator operates the brake pedal 20 to increase the descent speed of the suspended load (without pressing the brake pedal 20 too hard). As a result, the controller 80 controls the braking force of the winch drum 5 so that the descent speed of the suspended load reaches the target rotational speed Vt (controlling it to weaken the braking force). At this stage, it is preferable from the standpoint of work efficiency to lower the suspended load as quickly as possible. Therefore, for example, the suspended load may descend at the upper limit speed Vu.

[0037] (Mid-stage of lowering a suspended load) When the suspended load is about to fall at the target speed, the operator maintains the amount of pressure applied to the brake pedal 20 to maintain that state. The controller 80 then controls the brake device 4 so that the rotational speed of the suspended load becomes the target rotational speed Vt. In this state, since the amount of pressure applied to the brake pedal 20 is constant, the opening command Vout of the electromagnetic proportional valve 15 output from the controller 80 also becomes approximately constant, and the suspended load descends at a constant descent speed.

[0038] (The latter half of the process of lowering a suspended load) As the suspended load approaches the ground, the operator increases the amount the brake pedal 20 is pressed. The controller 80 then outputs an opening command Vout for the electromagnetic proportional valve 15 to reduce the rotational speed of the winch drum 5. In this way, the rotational speed of the winch drum 5 is automatically adjusted to match the descent speed of the suspended load corresponding to the amount the brake pedal 20 is pressed.

[0039] Here, the distance between the suspended load and the ground may be detected, and the controller 80 may automatically control the braking device 4 to reduce the rotational speed of the winch drum 5 according to that distance. For example, the height of the suspended load relative to the ground can be calculated from the number of turns of the main hoisting rope 112 and the angle of the boom 105, and the controller 80 may automatically reduce the descent speed of the suspended load according to the calculation result.

[0040] The effects and advantages of this embodiment can be summarized as follows:

[0041] The controller 80 controls the braking force of the brake device 4 based on the difference between the amount the brake pedal 20 is pressed and the actual rotational speed from the rotation sensor 10, so that the difference is minimized. This allows the operator to lower the suspended load at a descent speed of their choice during freefall. As a result, work efficiency during freefall is improved.

[0042] Furthermore, since the controller 80 controls the braking force of the brake device 4 based on the on / off operation of the speed adjustment switch 21, it is very convenient for simple speed adjustments. In other words, the operator can lower the suspended load at their desired descent speed simply by turning the speed adjustment switch 21 on and off, without having to operate the brake pedal 20, making it very user-friendly.

[0043] Furthermore, the first-order delay processing unit 32 smooths the operation signal of the brake pedal 20 (i.e., the target rotational speed Vt), thereby improving the responsiveness of the brake pedal 20 and reducing braking shock.

[0044] (Variation 1) Figure 4 is a block diagram showing the control configuration of the brake device according to Modification 1. In Figure 4, three rotation sensors 10 are provided, and the signal abnormality diagnosis unit 35 monitors the signals from the three rotation sensors 10, selects a normal signal, and outputs it to the speed deviation calculation unit 33. In other words, in Modification 1, the rotation sensors 10 are redundant. Here, "redundancy" means having a backup to prepare for emergencies (including maintenance), and in this embodiment, it means that each of the multiple rotation sensors detects a single state of the object being detected.

[0045] The signal anomaly diagnosis unit 35, for example, if the value of one of the three rotation sensors 10 suddenly becomes 0 (or the maximum value), determines that rotation sensor 10 is abnormal and disables the signal from that rotation sensor 10. Then, based on the input signals from the remaining two rotation sensors 10, the target rotation speed setting unit 30 sets the target speed. With this configuration, even if there is an abnormality in one of the three rotation sensors 10, the rotation speed of the winch drum 5 can be controlled with high reliability. At this time, the controller 80 may also notify the display device that one of the rotation sensors 10 is abnormal. Note that to achieve redundancy, there should be at least one rotation sensor 10.

[0046] (Modification 2) Figure 5 is a block diagram showing the control configuration of the brake device according to Modification 2. A key feature of Figure 5 is that the rotational speed of the winch drum 5 can be adjusted not only by the amount of pressure applied to the brake pedal 20, but also by the amount of pressure applied to the main winding operation lever 23, which is an electric lever.

[0047] As shown in Figure 5, the controller 80 receives the operating amount V3 of the main hoisting lever 23. The target rotation speed setting unit 30 sets the rotation speed of the winch drum 5 based on the sum of the brake pedal 20's depression amount V1 and the main hoisting lever 23's lowering operation amount V3, for example, during the period when the freefall function is active. Alternatively, the rotation speed of the winch drum 5 is set based on the lowering operation amount V3 of the main hoisting lever 23 instead of the brake pedal 20's depression amount V1. Subsequent processing is performed in the same manner as in the embodiment described above.

[0048] With this configuration, the main winding lever 23 can be used for adjusting the braking force, further improving the operator's operability.

[0049] (Variation 3) Figure 6 is a block diagram showing the control configuration of the brake device according to Modification 3. A key feature of Figure 6 is that the opening command Vout of the electromagnetic proportional valve 15 is determined based on a value ΔV' obtained by adjusting the gain with respect to the speed deviation ΔV.

[0050] Specifically, the controller 80 has a weight input dial 24 connected to its input side. The weight input dial 24 is located inside the cab 109. By operating the weight input dial 24, the weight of the bucket 116 is input to the controller 80.

[0051] The controller 80 includes a gain conversion unit 36 ​​and a gain adjustment unit 37.

[0052] The gain conversion unit 36 ​​determines the gain G based on the input bucket weight Wb. The gain conversion unit 36 ​​then outputs the determined gain G to the gain adjustment unit 37. The gain adjustment unit 37 outputs a speed deviation ΔV' corresponding to the gain G to the proportional valve output unit 34 based on the input speed deviation ΔV.

[0053] The proportional valve output unit 34 outputs an opening command Vout for the electromagnetic proportional valve 15 based on the speed deviation ΔV' with the gain G adjusted.

[0054] According to this modified version 3, the descent speed of the bucket 116 can be controlled with braking characteristics corresponding to the weight of the bucket 116. In other words, the operator can control the braking characteristics to their preference depending on whether the weight of the suspended load is light or heavy. Therefore, usability is improved.

[0055] (Modification 4) Figure 7 is a block diagram showing the control configuration of the brake device according to Modification 4. Figure 7 is characterized in that, instead of manually inputting the weight of the bucket 116, the rotational speed of the winch drum 5 is controlled based on the load Wl of the luffing rope detected by the line pull detector 17.

[0056] In this configuration, the controller 80 can calculate the weight of the suspended load from the value of the line pull detector 17 and control the rotation speed of the winch drum 5 without the operator having to input the weight of the suspended load, making it easier for the operator to operate than in Modification 3. Also, since the line pull detector 17 is typically mounted on the crane 100, there is no need to provide a weight input dial 24 as in Modification 3. This also contributes to reducing the number of parts.

[0057] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. All technical matters included in the technical concept described in the claims are subject to the present invention. The embodiments described above are preferred examples, but those skilled in the art can realize various alternatives, modifications, variations, or improvements from the contents disclosed herein, and these are included in the technical scope described in the appended claims.

[0058] Furthermore, while a crawler crane was given as an example of a crane, the present invention is not limited to this and can be applied to all kinds of cranes, including other mobile cranes such as wheel cranes, truck cranes, rough terrain cranes, and all-terrain cranes, as well as tower cranes, overhead cranes, jib cranes, retractable cranes, stacker cranes, gantry cranes, unloaders, and foundation machinery such as earth drills. [Explanation of symbols]

[0059] 1. Hydraulic motor 2. Brake system 4. Brake system 5. Winding Drum (Winch Drum) 10 Rotation Sensor 11 tanks 12 Hydraulic source 15 Solenoid proportional valve 17 Line pull detector 20 Brake pedal (operating mechanism) 21 Speed ​​adjustment switch 22 Speed ​​setting dial 23. Main winding lever (electric lever) 24 Weight input dial 30 Target rotation speed setting unit 31 Upper limit speed setting section 32 First-order lag processing unit 33 Speed ​​deviation calculation section 34 Proportional valve output section 36 Gain conversion section 37 Gain adjustment section 80 Controllers 100 Cranes 102 Running body 103 Swivel device 104 Rotating body 105 Boom 106 Main hoist winch 107 Auxiliary winch 108 Luffing Winch 109 Cab

Claims

1. A winch drum for raising and lowering suspended loads, A braking device that applies a brake to the rotation of the winch drum, The system includes an operating means for operating the aforementioned brake device, In a crane having a free-fall function that causes suspended loads to fall by gravity, The system includes a rotation sensor for detecting the rotational speed of the winch drum, During the period in which the freefall function is active, The braking force of the braking device is controlled so that the difference between the operating state of the operating means and the rotational speed of the winch drum detected by the rotation sensor becomes small. A crane characterized by the following features.

2. In the crane according to claim 1, By performing a predetermined operation, the upper limit of the rotational speed of the winch drum is set. The braking force of the braking device is controlled so that the rotational speed of the winch drum does not exceed the upper limit. A crane characterized by the following features.

3. In the crane according to claim 1, Based on information regarding the load of the suspended load, the feedback gain is adjusted for the brake signal output to the brake device. A crane characterized by the following features.

4. In the crane according to claim 1, Multiple rotation sensors are provided, and redundancy is ensured by these multiple rotation sensors. A crane characterized by the following features.

5. In the crane according to claim 1, The winch drum is equipped with an electric lever for operating the winch drum, During the period in which the freefall function is active, the braking force can be adjusted by operating the electric lever. A crane characterized by the following features.

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