Percussion and / or tamping device with improved electric drive

Abstract

A percussion or tamping device is specified, comprising a working device for generating a percussion or tamping movement; an electric motor (1) for driving the working device; and a drive train (4) for transmitting a rotary movement generated by the electric motor (1) to the working device; wherein an energy store (8) is provided in the drive train (4); and wherein the energy store (8) is designed such that it alternately stores and releases energy during a percussion or tamping cycle in order to even out the energy consumption of the electric motor (1).

Description

[0001] The invention relates to a percussion or tamping device with an improved electric drive.

[0002] Impact devices are well known. These can be, for example, breaker hammers or rotary hammers, which, during operation, exert blows on a tool, such as a chisel.

[0003] Tamping devices are also known, especially rammers for soil compaction.

[0004] Such machines are increasingly being equipped with an electric drive, with the electrical energy required for the electric drive being provided by a battery that serves as a storage device and is located on the machine itself.

[0005] Due to their design and operating principle, such devices or machines for impacting and / or pounding have uneven power requirements. In particular, the power requirement can vary significantly during a working cycle, i.e., a impact or pounding process.

[0006] For example, when the ground contact plate (tamping foot) of a rammer hits the ground, a high power requirement occurs within a very short period of time, namely during the tamping action on the ground, to keep the electric motor at a constant speed against the kickback from the rammer. The impact on the ground and the resulting kickback exert a strong braking effect on the motor, which it attempts to counteract by increasing its power consumption.

[0007] This creates very high peak currents throughout the system, which can be detrimental to the battery. In particular, the battery's efficiency, service life, and runtime can be significantly reduced due to the widely varying currents, but especially due to the very high peak currents.

[0008] In addition, the battery control system (BMS - battery management system) and, if necessary, the motor electronics must be designed for these high peak currents.

[0009] The same problem arises with breakers. The temporarily high peak currents can also place a significant strain on the battery.

[0010] In addition to reducing the battery life and running time, the high motor currents also lead to a higher cooling requirement for the battery cells and an overall poorer overall efficiency.

[0011] The invention is therefore based on the object of providing a percussion or tamping device with an improved electric drive in which the high peak currents previously occurring can be reduced.

[0012] The object is achieved according to the invention by a percussion or stamping device having the features of claim 1. Advantageous embodiments are specified in the dependent claims.

[0013] A percussion or tamping device is specified, comprising a working device for generating a percussion or tamping movement; an electric motor for driving the working device; and a drive train for transmitting a rotary movement generated by the electric motor to the working device; wherein an energy storage device is provided in the drive train; and wherein the energy storage device is designed such that it alternately stores and releases energy during a percussion or tamping cycle in order to even out the energy consumption of the electric motor.

[0014] The impact or tamping device can be designed, for example, as a tamper for concrete compaction or as a breaking hammer.

[0015] Depending on the design, the working device can be a percussion device, a percussion mechanism, or a tamping device. The structure of such devices is well known and therefore need not be explained in detail here.

[0016] The electric motor can typically have a power in a range of 1.5 kW to 3 kW and can therefore be suitable for driving a manually operated impact or tamping device.

[0017] The energy storage device makes it possible to store energy during an impact or tamping cycle and then release it again afterwards, thus evening out the energy consumption of the electric motor. In particular, the energy storage device can ensure that the strong kickback energy, which can occur, for example, when a tamping foot hits already compacted soil, is not completely and directly fed back to the electric motor, which would result in the high peak currents explained above. Instead, the energy storage device is able to either absorb kickback energy in this case or support the action of the motor against the kickback energy. The motor itself can then run more smoothly, so that its power consumption can also be evened out. Very high peak currents can be avoided in this way.

[0018] For example, the energy storage device can be designed to have additional inertia, which can be used to store energy in the system. The inertial energy can be stored, particularly in the drive train, with the help of the energy storage device.

[0019] For example, the energy storage device can have an additional rotating mass to increase the moment of inertia of the drive train. The drive train can be understood broadly and encompass the entire drive system, from the electric motor to the working movement, i.e., the impact or pitching motion.

[0020] The energy storage device must be installed at a suitable location. In particular, the energy storage device should be positioned in the power or torque flow between the electric motor and the point of action (tamping foot on a rammer, chisel on a breaker) or positioned in such a way that it can influence the power or torque flow.

[0021] The drive train can have a motor shaft of the electric motor, and the energy storage device can have a flywheel as an additional rotating mass arranged on the motor shaft. The rotating mass or flywheel should be firmly coupled to the motor shaft. For example, the rotating mass or flywheel can be firmly connected to the motor shaft, e.g., positively or frictionally connected, so that it is directly coupled to the rotation of the motor shaft. The additional inertia caused by the rotating mass of the flywheel can store energy to increase the inertia in the drive train system.

[0022] A fan wheel can be arranged on the motor shaft to generate a cooling air flow during operation of the electric motor, whereby the flywheel can be arranged on the fan wheel. In this case, it may be expedient to also utilize the space available for the fan wheel with a flywheel.

[0023] In one variant, the flywheel and the fan wheel can be integrated into a single, particularly one-piece, component.

[0024] In another variant, the flywheel and the fan wheel can be provided as individual components that are arranged or attached together on the motor shaft.

[0025] With both the integrated solution and the split solution with separate components, it is possible to reduce the height of the fan impeller (axial extension). This frees up space that can be used by the flywheel. Reducing the height of the fan impeller and thus also the efficiency of the fan impeller is possible because the drive components require less cooling. Due to the effect of the flywheel - as explained above - a reduction in peak currents is achieved, which means less cooling of the components is required. Accordingly, it is sufficient to design the fan or fan impeller with a weaker cooling effect. Even a small cooling air flow can be sufficient to provide adequate cooling.

[0026] In the split solution explained above with individual, separate components (flywheel, fan wheel), the two components can also be assembled together beforehand before being mounted as a unit on the motor shaft.

[0027] The electric motor may have a rotor mounted on the motor shaft, whereby the moment of inertia of the additional rotating mass may be greater than or equal to the combined moment of inertia of the motor shaft and rotor of the electric motor. Accordingly, it is important that the additional rotating mass has a significant moment of inertia relative to the motor shaft and rotor in order to achieve the desired equalization of power consumption.

[0028] For example, the combined moment of inertia of the flywheel and fan wheel can be greater than or equal to the combined moment of inertia of the motor shaft and rotor of the electric motor.

[0029] The electric motor can typically comprise a rotor and a stator. The rotor can be mounted on the motor shaft as a separate component. Alternatively, it can be integrated with the motor shaft to form a single component.

[0030] The combined moment of inertia can be calculated as the sum of the individual moments of inertia of the flywheel and fan wheel on the one hand, and of the motor shaft and rotor on the other. However, in a direct comparison, the combined moment of inertia of the flywheel and fan wheel should be greater than that of the motor shaft and rotor. Therefore, the moment of inertia of the motor shaft and rotor can be at least doubled by the flywheel and fan wheel.

[0031] The combined moment of inertia of the flywheel and the fan wheel can be at least 10%, in particular at least 25%, in particular at least 50% greater than the combined moment of inertia of the motor shaft and the rotor of the electric motor.

[0032] In this context, it should be noted that in a conventional electric drive, the fan wheel is usually made of a very lightweight material, such as plastic or aluminum. Accordingly, the moment of inertia of the fan wheel (without the flywheel) is considerably lower than the combined moment of inertia of the motor shaft and rotor, which are often made of other materials, such as steel or cast iron. In the invention, however, a much higher moment of inertia is achieved due to the additional rotating mass.

[0033] In a specific embodiment, the combined moment of inertia of the motor shaft and rotor can range from 1,300 to 1,700 kg mm². In particular, the moment of inertia can be 1,500 kg mm². This value is typical for an electric motor with a power range of 1.5 kW to 3 kW.

[0034] The combined moment of inertia of the flywheel and fan wheel can be in the range of 1,800 to 2,200 kg mm 2<, particularly 2,000 kg mm 2<.

[0035] These values ​​have proven themselves in practice and have led to significant reductions in peak currents.

[0036] Drive systems are known in the prior art in which a centrifugal clutch is provided between the drive motor and the working device. The centrifugal clutch only closes the torque flow when the drive motor has reached a certain, defined speed. This is intended to allow the drive motor to initially rev up in a lower speed range without torque load. When the defined speed is exceeded, the centrifugal clutch closes, allowing the drive energy of the drive motor to be transferred to the drive train.

[0037] In one variant, the impact device or tamping device according to the invention can be designed in such a way that no centrifugal clutch is required in the drive train. In this case, the electric motor and the drive train are permanently and directly engaged, so that the drive train is driven immediately when the electric motor is started. No centrifugal clutch is arranged between the electric motor and the drive train.

[0038] Thus, a gear provided in the drive train between the motor shaft and the impact mechanism or stamping mechanism can be permanently engaged and driven. The gear can have a fixed or constant gear ratio. For example, the gear can use gears and shafts, so that no slippage can occur in the gear. However, slippage cannot be avoided when using a centrifugal clutch. However, as mentioned above, the described design does not require a centrifugal clutch.

[0039] In one design, the fan wheel can be located on the side of the electric motor facing away from the gearbox. This means that the gearbox is located at one end of the motor shaft, and the fan wheel or, if applicable, the flywheel is located at the other end of the motor shaft.

[0040] The battery and electronics, in particular a frequency converter that converts the battery's DC voltage into an AC voltage suitable for the electric motor, can be mounted on a drawbar or a guide handle / guide bar, which can be used to guide the machine. The drawbar or guide handle can be mounted on an upper mass of the impact or tamping device in a vibration-decoupled manner. The upper mass is separated from a lower mass by a vibration-decoupling device. The lower mass is movable relative to the upper mass and has, for example, a ground contact plate for soil compaction.

[0041] The invention enables the implementation of a modular system. In particular, a space can be provided on the electric drive that can be used either entirely by the fan wheel or, alternatively, jointly by a combination of fan wheel and flywheel. In this way, even a conventional electric drive known from the prior art can be easily converted and equipped with a flywheel to even out the current flow.

[0042] Depending on the requirements and application, the motor shaft can then be determined with the fan wheel alone or with a combination of fan wheel and flywheel, without having to change other components of the electric drive.

[0043] The invention is explained in more detail below using examples with the aid of the accompanying figures. They show: Fig. 1 a cross-section through an electric drive with a conventional design; Fig. 2 a section through an electric drive according to the invention; Fig. 3 the current curve over time in a conventional electric drive; and Fig. 4 the current curve over time in an electric drive according to the invention.

[0044] Fig. 1 shows a schematic cross-section through a state-of-the-art electric drive that can be installed in an impact or tamping device. The electric drive can be used, for example, to drive a tamper for soil compaction. For this purpose, the electric drive can be attached to a tamper housing and connected accordingly.

[0045] The electric drive comprises an electric motor 1 with a stator 2 and a rotor 3, which is mounted on a motor shaft 4. A shaft end 5 can be connected to a working device (not shown). In the case of a rammer for soil compaction, the working device is a correspondingly designed and known rammer. Alternatively, the electric drive can also be attached to an impact device, e.g., a breaker. In this case, the shaft end 5 is connected to a correspondingly designed impact device, e.g., an air-spring impact mechanism.

[0046] Opposite the shaft end 5, a shaft shoulder 6 is provided on the motor shaft 4, on which a fan wheel 7 is arranged.

[0047] When the electric motor 1 is operating, the rotor 3 drives the motor shaft 4. This also causes the fan wheel 7 to rotate, generating a cooling air flow for the electric motor 1, which can be directed past the rotor 3 and stator 2 in particular.

[0048] Fig. 2 shows an electric drive according to the invention, which is largely analogous to the electric drive of Fig. 1 Accordingly, the same reference numerals are used.

[0049] In the variant of Fig. 2 However, the height of the fan wheel 7, i.e. the axial extension of the fan wheel 7, is compared to the variant of the prior art according to Fig. 1 The fan wheel 7 is thus smaller and results in a lower cooling air flow, which, however, is unproblematic due to the more uniform power consumption, as will be explained later.

[0050] The space freed up by reducing the size of the fan wheel 7 is filled with a flywheel 8, which serves as an additional rotating mass and is also mounted on the shaft shoulder 6. The flywheel 8 is made of a suitable material to provide a suitable flywheel mass. For example, metallic materials such as cast metal, steel, or aluminum are conceivable.

[0051] The flywheel significantly increases the inertia of the entire system without requiring modification of the electric motor 1, particularly the motor shaft 4 and the rotor 3. This makes it possible to continue using standard electric drives without requiring modification of other components.

[0052] Fig. 3 shows an example of a comparative measurement on a state-of-the-art electric drive, with the current drawn from a battery plotted over the measurement time. It can be seen that the current reaches a strength of up to 100 A in each cycle. A total of six cycles are shown in the diagram.

[0053] The effective value of the current (RMS current value) is 48.5 A in the example shown.

[0054] In comparison, Fig. 4 The battery current drawn by the electric motor was measured over time in an electric drive equipped according to the invention with a flywheel 8. It can be seen that the peak currents are now only approximately 75 A, thus being reduced by approximately 25%. The RMS current value was reduced from 48.5 to 44.4 A, i.e. by 9%.

[0055] By comparing the measurement curves of Fig. 3 and 4It is clearly visible how the additional inertia due to the rotating mass in the form of the flywheel 8 creates a

[0056] This allows for a more homogeneous current flow. This results in a lower load on the battery powering electric motor 1.

[0057] The invention allows for the provision of an additional rotating mass in or on the motor to increase inertia. The electric motor 1 itself, i.e., the motor shaft 4 and the rotor 3, do not need to be modified.

[0058] Due to thermal losses in the electric motor 1, it must be cooled by means of the fan wheel 7. The fan wheel 7 or the shaft end there (shaft shoulder 6) can be used for the additional inertial mass in the form of the flywheel 8.

[0059] The improved efficiency also makes it possible to reduce motor cooling. Therefore, the reduced height of fan impeller 7 may be sufficient.

[0060] The fan wheel 7 and the flywheel 8 can be manufactured as a single piece. It is also possible to mount the two components separately on the motor shaft 4 as a two-piece construction.

Claims

1. Impact or tamping device, comprising - a working device for generating an impact or tamping movement; - an electric motor (1) for driving the working device; and - a drive train (4) for transmitting a rotary movement generated by the electric motor (1) to the working device; wherein - an energy store (8) is provided in the drive train (4); and wherein - the energy store (8) is designed such that it alternately stores and releases energy during an impact or tamping cycle in order to even out the energy consumption of the electric motor (1).

2. Impact or tamping device according to claim 1, wherein the energy storage device has an additional rotating mass (8) for increasing the moment of inertia of the drive train (4).

3. Impact or tamping device according to one of the preceding claims, wherein - the drive train comprises a motor shaft (4) of the electric motor (1); and wherein - the energy storage device comprises a flywheel (8) as an additional rotating mass, which is arranged on the motor shaft (4).

4. Impact or tamping device according to claim 3, wherein - a fan wheel (7) is arranged on the motor shaft (4) for generating a cooling air flow during operation of the electric motor (1); and wherein - the flywheel (8) is arranged on the fan wheel (7).

5. Impact or tamping device according to claim 4, wherein the flywheel (8) and the fan wheel (7) are integrated into one component.

6. Impact or tamping device according to claim 4, wherein the flywheel (8) and the fan wheel (7) are individual components arranged together on the motor shaft (4).

7. Impact or tamping device according to one of the preceding claims, wherein - the electric motor (1) has a rotor (3) arranged on the motor shaft (4); and wherein - the moment of inertia of the additional rotating mass (8) is greater than or equal to the combined moment of inertia of the motor shaft (4) and rotor (3) of the electric motor (1).

8. Impact or tamping device according to one of the preceding claims, wherein - the electric motor (1) has a rotor (3) arranged on the motor shaft (4); and wherein - the combined moment of inertia of the flywheel (8) and fan wheel (7) is greater than or equal to the combined moment of inertia of the motor shaft (4) and rotor (3) of the electric motor (1).

9. Impact or tamping device according to one of the preceding claims, wherein the common moment of inertia of the flywheel (8) and fan wheel (7) is at least 10%, in particular at least 25%, in particular at least 50% greater than the common moment of inertia of the motor shaft (4) and rotor (3) of the electric motor (1).

10. Impact or tamping device according to one of the preceding claims, wherein the joint moment of inertia of the motor shaft (4) and rotor (3) is in a range of 1,300 to 1,700 kg*mm 2 lies.

11. Impact or tamping device according to one of the preceding claims, wherein the joint moment of inertia of the flywheel (8) and fan wheel (7) is in a range of 1,800 to 2,200 kg*mm 2 lies.

Images