Ground compaction device with electric drive

Abstract

To provide a ground compaction device acting as a vibratory tamper, allowing a compact construction with the fewest possible number of components.SOLUTION: A ground compaction device comprises an upper mass (1), and a lower mass (2) with a ground element (4) for compacting the ground, movable relative to the upper mass (1) and connected to the upper mass (1) via a spring device (3). The upper mass (1) is provided with a drive for inducing a working movement of the ground element. The drive comprises a tamping device and an electric motor (20) for driving the tamping device. The tamping device comprises a crank wheel (23) rotatably driven by an electric motor (20), a connecting rod (25) connected to the crank wheel (23), and a reciprocating tamping piston (26) connected to the connecting rod (25). The tamping piston (26) cooperates with the spring device (3).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a ground compaction device with an electric drive.

[0002] A variety of such ground compaction devices, in particular so-called vibrating or rocking tampers, are known and are used for compacting the ground and asphalt layers. In this case, the tampers are variously driven by internal combustion engines, for example two-stroke engines. It is also known to provide an electric drive motor.

[0003] In electric drives, an electric motor is typically driven at a relatively high speed and drives, via a reduction gear, a spring-mass system that serves as a compaction system. In this case, the electric drive motor is supplied with power from the current grid or from a portable battery.

[0004] The electric drive motor has a stator and a rotor. Asynchronous machines with short-circuited rotors and brushless direct current motors (BLDC motors) have proven suitable.

[0005] Depending on the design of the drive motor and the operating mode of the vibration tamper, a reduction gear is required to match the rotational speed (compaction frequency) required by the compaction system. This type of gear requires construction space and additional components. Furthermore, this reduces the efficiency of the drive, which is particularly undesirable due to the limited electrical capacity of the available batteries.

[0006] 1 shows an example of a vibration tamper known from the prior art, which comprises an upper mass 1 and a lower mass 2 that is movable relative to the upper mass 1. The lower mass 2 is connected to the upper mass 1 via a spring arrangement 3. The spring arrangement 3 supports a spring-mass system in which a forcing movement introduced via the upper mass 1 causes a spring-elastic compacting movement of a ground plate 4 provided on the lower mass 2.

[0007] The upper mass 1 is provided with an electric motor 5, which drives a crank wheel 7 in rotation via a reduction gear 6. The crank wheel 7 is provided with a crank pin 8 which is connected to a connecting rod 9. The connecting rod 9 is also connected to a compaction piston 10, the end of which cooperates with the spring device 3 in a manner known per se.

[0008] A gripping device 11, for example a gripping handle, is attached to the upper mass 1 via a vibration isolator 12, for example a rubber cushion. An operator can guide the vibration tamper in the gripping device 11 by hand.

[0009] The gripping device 11 is fitted with an energy storage device in the form of a battery 13 .

[0010] In the embodiment of the conventional vibration tamper shown in Figure 1, a battery 13 is connected to the electric motor 5, which not only provides an electrical supply line to the electric motor 5 but also allows a cooling air flow through the battery 13 and the electric motor 5. The cooling air flow can be generated by a blower (not shown), for example by a fan provided on the electric motor 5.

[0011] In order to be able to accommodate the various components in the tamper, the drive motor must usually be arranged outside the compaction axis, which results in a tilting moment when the tamper is in operation, which reduces the action of the tamper and worsens its guiding properties.

[0012] The problem underlying the present invention is to provide a ground compaction device acting as a vibration tamper, which allows for a particularly compact construction with as few components as possible.

[0013] This problem is solved according to the invention by a ground compaction device having the features of claim 1. Advantageous configurations are set out in the dependent claims.

[0014] The present invention describes a ground compaction device comprising an upper mass and a lower mass with ground-contacting elements for compacting the ground, the lower mass being movable relative to the upper mass and connected to the upper mass via a spring device, the upper mass being provided with a drive device for inducing a working movement of the ground-contacting elements. The drive device comprises a compaction device and an electric motor for driving the compaction device, the compaction device comprising a crank wheel rotatably driven by the electric motor, a connecting rod connected to the crank wheel, and a reciprocable compaction piston connected to the connecting rod, the compaction piston cooperating with the spring device. The electric motor comprises a stator and a rotor, the rotor being fixedly or resiliently connected to the crank wheel.

[0015] The rotor and crank wheel therefore form a single unit, so to speak, and relative rotation between them is not possible except for allowable elasticity, for example, if they are elastically coupled. There is no transmission, particularly a reduction gear, between the rotor and crank wheel, as is required in the prior art.

[0016] The electric motor may be a reluctance machine, in particular a synchronous reluctance machine, in which case synchronous reluctance machines with segmented stators have proven particularly suitable, in which the stator extends only over a certain angular range (stator block).

[0017] The direct connection between the rotor and the crank wheel eliminates the need for an otherwise intervening reduction gear, thereby saving a considerable number of components. By appropriately designing the electric motor, it is possible to operate it at low rotational speeds that are already suitable for the compaction process and the desired compaction frequency. Therefore, the electric motor must provide sufficient torque at these low rotational speeds to ensure that the compaction process can be carried out powerfully. Reluctance machines are particularly suitable in this case.

[0018] The omission of a reduction gear allows for a particularly compact structure of the earth compaction device, which further allows for an advantageous weight or mass distribution of the components. In other words, with a suitable configuration of the electric motor and the compaction device, the center of gravity of the electric motor can be arranged on the compaction axis, i.e., on the longitudinal axis of the movement of the lower mass and the compaction piston. There is no leverage between the movement of the lower mass and the center of gravity of the electric motor. This makes it possible to avoid undesirable tipping moments during operation of the tamper.

[0019] The rotor may be formed on the circumferential surface of the crank wheel. In this embodiment, the rotor replaces the crank wheel, so to speak, or the rotor becomes part of the crank wheel. This allows the rotor and the crank wheel to be integrated into one part. In this case, the rotor may be arranged radially outer on the circumferential surface of the crank wheel. The crank wheel and the rotor form one unit, so that the rotor can take over the function of the crank wheel, i.e., drive or move the connecting rod in particular. This eliminates the need for a classic motor shaft to connect the rotor to the crank wheel.

[0020] The outer periphery of the crank wheel must be configured in an appropriate manner so that it can be used as a rotor.

[0021] The rotor may therefore have a plurality of rotor poles which may be arranged on the circumferential surface of the crank wheel.

[0022] The rotor poles can be constructed in layers, i.e., in the form of metal sheets stacked one on top of the other to form a laminated metal sheet. For electromagnetic reasons, a layered structure can be provided for the rotor, so that the rotor poles, or the pole wheels formed thereby by the rotor poles, are preferably formed from laminated metal sheets.

[0023] The rotor poles may be configured together with the crank wheel. That is, the rotor poles and crank wheel together consist of metal sheets stacked on top of each other. The metal sheets may, for example, include the contours of the rotor poles on their periphery and the contours of the crank wheel on their interior. The metal sheets are stacked on top of each other and assembled to form the rotor with the rotor poles and the crank wheel. The metal sheets may be joined together in any suitable manner, for example by pin connections (press fit) or screw connections.

[0024] In one variation, the crank wheel can be non-laminated and support laminated rotor poles, i.e., laminated pole wheels, on its circumferential surface. The crank wheel can therefore be solid, for example, constructed as a turned part (steel turned part or cast iron turned part). The crank wheel serves as a support for the rotor with the rotor sheet metal and supports the laminated sheet metal for the rotor poles on its circumferential surface. A laminated sheet metal ring is therefore attached to the circumferential surface of the crank wheel.

[0025] The stator may surround the rotor over an angle less than 360°. Therefore, in this variation, the motor stator may no longer be configured as a closed rotating element or ring, but may extend only over a defined angular range. The stator may thus be configured as a stator segment or stator block, and may extend over an angle of, for example, 270° or less, 180° or less, 120° or less, or 90° or less.

[0026] It is therefore possible to distribute a number of stator segments or stator blocks around the rotor, which allows the performance and in particular the torque of the motor to be increased.

[0027] The stator may be arranged above the rotor in a defined working position of the earth compaction device. For example, the stator may be held in a motor cover or in a cover of the drive casing or crank casing. In this case, the stator may not form a structural unit with the rotor. In particular, the stator and rotor may not be housed separately from the crank wheel in a common electric motor casing. Instead, the stator, rotor, and crank wheel may be arranged in a common casing or separately from each other.

[0028] In one variant, at least two crank wheels can be provided, each with a rotor on its periphery, and both crank wheels drive the connecting rod together. Thus, in this embodiment, multiple rotors and stators can be provided, which allows for a particularly powerful drive of the compaction device.

[0029] In particular, the two crank wheels and the rotors associated with them can be aligned coaxially with one another, so that the connecting rod can be driven in the desired manner.

[0030] At least a portion of the drive may be enclosed by a drive casing, and an air flow generating device may be provided for generating a cooling air flow in the drive casing for cooling the rotor and the stator. The drive casing can therefore also be understood as a crank casing or a motor casing, and the inside of the drive casing accommodates, inter alia, the stator, the rotor, the crank wheel, at least a portion of the connecting rod, and possibly also a portion of the compaction piston.

[0031] By means of the air flow device, it is possible to create a cooling air flow inside the drive unit housing and thus to remove heat from the rotor and stator and possibly also from the compaction device.

[0032] The airflow generating device may have at least one of the following operating principles: the movement of the tamping piston can cause an air pumping action for generating the cooling airflow, or the rotor is provided with at least one fan blade for generating the cooling airflow. Thus, the tamping piston on the one hand and the rotor on the other hand have effective areas for intentionally generating air movements that can generate or support the desired cooling airflow.

[0033] The drive unit casing may be provided with an air inlet for letting air in from the periphery and an air outlet for letting air out to the periphery, the air inlet may be provided with a check valve for setting the air flow direction from the periphery into the drive unit casing, and the air outlet may be provided with a check valve for setting the air flow direction from the drive unit casing to the periphery.

[0034] The check valve is therefore a directional valve that allows air flow in only one direction, i.e., into the drive casing via the air inlet or out of the drive casing via the air outlet. The check valve may have, for example, a rubber flap-like element that opens or closes the corresponding opening depending on the air flow direction.

[0035] As a result, fresh air can be drawn into the drive casing from the surroundings via the air inlet during the pumping action of the compaction piston and thus the change in the air volume inside the drive casing, and can be expelled via the air outlet during the compression action of the compaction piston, thereby achieving a constant air exchange and thus a cooling effect inside the drive casing.

[0036] A motor control device may be provided for controlling the electric motor so that the rotational speed of the rotor, and thus the rotational speed of the crank wheel via one or more rotations of the rotor, can be changed. The motor control device thus serves to intentionally change the rotational speed and thus the torque. This change is therefore based not only on the reaction of the compaction system and thus the ground to be compacted, but also on intentional control by the motor control device.

[0037] This allows for variations in the movement of the compaction base, which can be used to dynamicize the compaction process and also to settle the machine: for example, if the compaction device is bouncing on hard ground, the drive energy of the motor is reduced, which allows the compaction device to settle.

[0038] Similarly, a short-term increase in the rotational speed can cause a double impact of the compaction device on the ground to be compacted, which in turn reduces the repulsive forces acting on the operator guiding the compaction device in the event of simultaneously high compaction energies.

[0039] The motor controller can also be used to scale the torque, allowing different forces to be applied to the ground.

[0040] These and other advantages and features of the present invention will be explained in more detail below, by way of example, with reference to the accompanying drawings. [Brief explanation of the drawings]

[0041] [Figure 1] 1 shows a vibrating tamper known from the prior art as a ground compaction device; [Figure 2] 1A and 1B are a side view and a front view showing a cross section of a vibration tamper as a ground compaction device according to the present invention. [Figure 3] 1A-1C are cross-sectional front views of different variations of vibration tampers according to the present invention; [Figure 4] 10A and 10B show another variation of the vibration tamper according to the present invention. [Figure 5] FIG. 1 shows a variation of a vibration tamper with a fixed connection between the rotor and crank wheel. [Figure 6] FIG. 1 shows a vibration tamper with an air flow creating device. [Figure 7] 10A and 10B are diagrams showing variations of the air flow creating device. [Figure 8] FIG. 10 is a diagram showing another embodiment of an air flow creating device. [Figure 9] FIG. 1 shows a vibration tamper with an attachable gripping device. [Figure 10] FIG. 1 shows one variation of a vibration tamper according to the present invention.

[0042] 2 shows a vibrating tamper as a ground compaction device according to the invention in a cross-sectional side view in the left part of the figure and in a cross-sectional front view in the right part of the figure. Insofar as components functionally correspond to the components of the vibrating tamper described above in relation to the prior art shown in FIG. 1, the same reference numerals are used.

[0043] The vibration tamper therefore comprises an upper mass 1 and a lower mass 2 which is movable relative to the upper mass 1. The lower mass 2 is connected to the upper mass 1 via a spring arrangement 3. The spring arrangement 3 supports a spring-mass system in which a forcing movement (linear reciprocating movement of a tamping piston) introduced via the upper mass 1 causes a spring-elastic tamping movement of a ground plate 4 provided on the lower mass 2.

[0044] A gripping device 11, e.g. a gripping handle, is attached to the upper mass 1 via a vibration isolator 12, e.g. a rubber cushion. An operator can manually guide the vibration tamper in the gripping device 11. An energy storage device in the form of a battery 13 is attached to the gripping device 11.

[0045] Inside the upper mass 1 is an electric motor 20 with a stator 21 and a rotor 22. The electric motor 20 is configured as a synchronous reluctance machine, with the stator 21 being a segmented stator which extends only over a range of approximately 90°, as can be seen in the right part of FIG.

[0046] The rotor 22 is disposed on the outer peripheral surface of the crank wheel 23. As a result, the crank wheel 23 is an integral part of the electric motor 20 and is directly driven by the electric motor 20 without the need for a transmission.

[0047] In this case, the rotor 22 may be formed to be somewhat wider than the thickness of the crank wheel 23, as can be seen in the left part of FIG. 2, so that the rotor 22 somewhat covers the crank wheel 23.

[0048] The crank wheel 23 drives a connecting rod 25 via a crank pin 24, which in turn linearly reciprocates a compaction piston 26 in a manner known per se. The compaction piston 26 cooperates with the spring device 3 to achieve a spring-elastic compaction movement of the contact plate 4 on the basis of the guided reciprocation of the compaction piston 26.

[0049] In the upper mass 1, a battery 13 is also provided on the gripping device 11, which is connected to the upper mass 1 via a vibration isolator 12. The battery 13 is used to supply energy to the electric motor 20.

[0050] The rotor 22 is of layered construction and therefore comprises laminated sheet metal which is mounted on or supported by the crank wheel 23, which is constructed, for example, as a turned or forged part. In one variant, the rotor 22 and the crank wheel 23 can be formed from laminated sheet metal, i.e., the rotor 22 and the crank wheel 23 can be of layered construction.

[0051] Figure 3 shows different variations of the tamper shown in Figure 2, each having a differently configured rotor 22 with differently configured rotor poles. In particular, it can be seen that in the different variations shown in Figures 3a-3f, the rotors have different numbers of rotor poles.

[0052] In particular, the different variations have the following characteristics: a: Combination of crank wheel and synchronous reluctance ring motor b: Synchronous reluctance rotor as crank wheel c: Crank wheel with magnets arranged on the periphery d: Crank wheel with magnets arranged on the periphery and / or inside e: crank wheel as asynchronous motor rotor; also possible as a combination f: Shaped magnetic poles in an asynchronous motor, magnet motor or synchronous reluctance motor.

[0053] Figure 4 shows, in part a on the left, a variant in which two crank wheels 23 are driven by rotors 22 arranged on the periphery. Correspondingly, two electric motors 20 are provided, arranged coaxially with respect to one another. The crank wheels 23 together drive a connecting rod 25. The double motor arrangement makes it possible to realize a particularly compact and powerful drive.

[0054] In the variant shown in Figure 4b, the rotor 22 is arranged axially offset relative to the crank wheel 23. This allows the weight distribution along the compaction axis to be optimally configured.

[0055] Figure 5 shows another embodiment of the variant shown in Figure 4b, in which the rotor 22 and the crank wheel 23 are arranged coaxially on a common shaft 27 and are connected to each other in a positively locking manner at least in the circumferential direction by a shaft-hub connection (here a parallel key connection).

[0056] FIG. 6 shows a vibration tamper similar to the vibration tamper shown in FIG.

[0057] It is further evident that the compaction piston 26 together with the spring device 3 forms a kind of air pump, which periodically compresses and decompresses the air inside the drive casing 28 which surrounds the electric motor 20, the crank wheel 23 and part of the compaction device.

[0058] The alternating compression and decompression causes air to move inside the drive casing 28 , thereby creating a cooling airflow that cools the components of the electric motor 20 .

[0059] 7 shows another embodiment with an airflow device, which has fan blades 29 arranged on the rotor 22 or crank wheel 23. The rotation of the rotor 22 and crank wheel 23 causes air to circulate inside the drive casing 28, which provides cooling.

[0060] FIG. 8 shows another variation of the air flow creating device.

[0061] This principle is based on the diagram of Figure 6, whereby a pumping action is achieved inside a drive casing 28 by linear movement of the lower mass 2 by means of a spring device 3. The drive casing 28 has an air inlet 30 and an air outlet 31. The air inlet 30 is connected to a first check valve 32 (inlet check valve 32) via an air passage 30a. The air outlet 31 is provided with an outlet check valve 33.

[0062] FIG. 8 further shows that air is guided over the battery 13 via an air passage 30a extending between the inlet check valve 32 and the air inlet 30, so that the air first cools the battery 13 before reaching the interior of the drive casing 28.

[0063] Due to the alternating positive and negative pressures inside the drive casing 28 during the compacting movement of the lower mass 2, air is alternately sucked into the drive casing 28 via the inlet check valve 32 and the air inlet 30 and discharged via the air outlet 31 and the outlet check valve 33. A constant cooling air flow can thus be generated inside the drive casing 28 by the pumping movement of the lower mass 2.

[0064] Figure 9 shows an example of a compaction device according to the invention with a foldable grip handle 34, in which the left part of the figure shows the grip handle 34 in a folded position, e.g. a particularly compact transport position, while in the right part of the figure the grip handle 34 is shown in an open position, i.e. an operating or working position.

[0065] The battery 13 may be connected to the drive casing 28 via an elastic hose 35 which serves as an air passage 30a, thereby enabling the cooling air guide of the type described above and allowing the grip handle 34 to be folded.

[0066] Figure 10 shows a variation on the vibration tamper shown in Figure 2. The stator 21 is rotated by 90° in the direction of the rotation axis of the rotor 22, i.e. relative to the rotor 22 and thus relative to the crank wheel 23. This makes it possible to reduce the structural height of the drive casing 28 and thus of the entire tamper.

[0067] It is desirable that the air passage 30a extending at least between the casing of the battery 13 and the drive casing 28 has a certain elasticity in all the variants shown, in particular in the variants of Figures 2, 4, 8 and 10, so that the relative movements of the gripping device 11 supporting the battery 13 with respect to the drive casing 28 of the upper mass 1 can be compensated.

Claims

1. 1. A ground compaction device comprising: An upper mass (1), a lower mass (2) movable relative to the upper mass (1) and connected to the upper mass (1) via a spring device (3) and provided with ground-contacting elements (4) for compacting the ground; It is equipped with The upper mass (1) is provided with a drive for inducing a working movement of the ground contact element, The drive device includes a compaction device and an electric motor (20) for driving the compaction device; the compaction device includes a crank wheel (23) that can be rotated by the electric motor (20), a connecting rod (25) connected to the crank wheel (23), and a compaction piston (26) that can move back and forth and that is connected to the connecting rod (25), the compaction piston (26) cooperating with the spring device (3); The electric motor (20) has a stator (21) and a rotor (22), and A ground compaction device, wherein the rotor (22) is fixedly or resiliently connected to the crank wheel (23).

2. 2. The soil compaction device according to claim 1, wherein the rotor (22) is formed on the circumferential surface of the crank wheel (23).

3. 3. The earth compaction device according to claim 1, wherein the rotor (22) has a plurality of rotor poles, the rotor poles being arranged on the circumferential surface of the crank wheel (23).

4. 3. The earth compaction device according to claim 1, wherein the rotor poles are arranged in layers.

5. 3. The earth compaction device according to claim 1, wherein the rotor poles are arranged in layers together with the crank wheel (23).

6. 3. The earth compaction device according to claim 1, wherein the crank wheel (23) is of non-laminar construction and supports the laminar rotor poles on its circumferential surface.

7. 3. The earth compaction device according to claim 1, wherein the stator (21) surrounds the rotor (22) through an angle of less than 360°.

8. 3. The earth compaction device according to claim 1, wherein the stator (21) is arranged above the rotor (22) in the normal working position of the earth compaction device.

9. At least two crank wheels (23) are provided, and one rotor (22) is provided on the circumferential surface of each of the crank wheels (23), 3. The earth compaction device according to claim 1, wherein the connecting rod (25) is driven by both crank holes (23) together.

10. At least a portion of the drive unit is enclosed by a drive unit casing (28); 3. The earth compaction device according to claim 1, further comprising an air flow forming device for forming a cooling air flow in the drive device casing (28) for cooling the rotor (22) and the stator (21).

11. The air flow generating device operates according to the following principle: The movement of the compaction piston (26) can cause an air pumping action to form the cooling air flow; the rotor (22) is provided with at least one fan blade (29) for forming the cooling airflow; 3. The soil compaction device according to claim 1, wherein the soil compaction device has at least one of the following operating principles:

12. The drive casing (28) is provided with an air inlet (30) for drawing in air from the surroundings and an air outlet (31) for drawing air out to the surroundings; The air inlet (30) is provided with a check valve (32) for directing air flow from the periphery into the drive casing (28); and 3. The device according to claim 1, wherein the air outlet (31) is provided with a check valve (33) for setting the air flow direction from the drive casing (28) to the surroundings.

13. 3. The ground compaction device according to claim 1, further comprising a motor control device for controlling the electric motor so that the rotation speed of the rotor (22) and thus the rotation speed of the crank wheel (23) through one or more rotations of the rotor (22) can be changed.

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