Electromagnetic imbalance control device for soil compaction equipment

Description

[0001] The invention relates to a soil compaction device with an unbalance exciter.

[0002] Such soil compaction devices are often also referred to as vibrating plates or vibratory plates. They typically have an upper mass and a lower mass that can be moved relative to the upper mass. Such vibrating plates are usually powered by an internal combustion engine, which is then added to the upper mass. A ground contact plate is attached to the lower mass, which can be used to compact the soil below.

[0003] The ground contact plate is subjected to an unbalance force by an imbalance exciter, thus causing vibration, to achieve the desired soil compaction. The unbalance exciter and the ground contact plate are thus considered part of the sub-mass.

[0004] A vibration decoupling device, for example a spring device with the aid of rubber buffers, is provided between the upper mass and the lower mass so that the strong vibrations generated on the lower mass are transmitted to the upper mass to only the smallest possible extent.

[0005] The unbalance exciter often has one or more unbalance shafts carrying an unbalance mass to achieve the desired vibration effect when the unbalance shafts or unbalance masses rotate. To rotate the unbalance shaft(s), the drive energy of the drive motor is transmitted in a suitable manner. For example, in smaller vibrating plates, a belt drive may be provided between the combustion engine located on top and the unbalance exciter located on the bottom mass. For larger, more powerful vibrating plates, a hydraulic system is often used to transmit the drive energy.

[0006] Fig. 1 shows an example of a vibrating plate known from the prior art serving as a soil compaction device.

[0007] The vibrating plate has an upper mass 1 and a lower mass 2 that is movable relative to the upper mass 1. The lower mass 2 is coupled to the upper mass 1 via rubber buffers 3 that serve as a vibration decoupling device.

[0008] In this way, the strong vibrations occurring at the lower mass 2 are only transmitted to the upper mass 1 in a damped manner.

[0009] The upper mass 1 has a supporting frame 4, on which, in the example shown, an internal combustion engine 5 is mounted, which is also assigned to the upper mass 1. The internal combustion engine 5 is enclosed by a protective frame 6.

[0010] The base mass 2 has a soil contact plate 7, which can be used to compact the soil underneath. A vibration exciter or imbalance exciter 8, also belonging to the base mass 2, is arranged on the upper side of the soil contact plate.

[0011] The unbalance exciter 8 has at least one, but often two or more, unbalance shafts, which are rotationally driven by the combustion engine 5. Due to the unbalanced masses carried by the unbalance shafts, strong centrifugal forces arise, which lead to corresponding vibrations of the ground contact plate 7 and thus of the entire base mass 2. These vibrations are desirable and serve to effectively compact the soil.

[0012] Two principles in particular have prevailed for transmitting the drive energy from the combustion engine 5 to the imbalance exciter 8. For smaller vibrating plates, a V-belt drive is generally provided between the combustion engine 5 and the imbalance exciter 8, and thus between the upper mass 1 and the lower mass 2. For larger, more powerful vibrating plates, the combustion engine 5 drives a hydraulic pump, allowing a hydraulic fluid to be pressurized. A hydraulic motor is then provided on the imbalance exciter 8, which is driven by the hydraulic pressure to rotate the imbalance shafts present in the imbalance exciter 8.

[0013] To carry out the Fig. 1 In the vibration plate shown, a guide bar 9 is also attached to the upper mass 2 or the support frame 4. A throttle lever 10 is provided on the guide bar 9 for influencing the engine speed of the internal combustion engine. Furthermore, a control handle 11 is arranged at the upper end of the guide bar 9, via which the relative rotational position of the unbalance shafts in the unbalance exciter 8, in particular their phase position relative to one another, can be adjusted in a known manner. In this way, forward and reverse travel of the vibration plate can be achieved in a conventional manner.

[0014] Instead of the combustion engine 5, it is also known to use an electric motor. Likewise, vibrating plates are known in the prior art in which the electric motor is mounted directly on the base mass 2, namely in particular on the ground contact plate 7 near the imbalance exciter 8, in order to drive the one or more imbalance shafts in the imbalance exciter 8.

[0015] When the electric motor is installed on the base of the vibrating plate, the electric motor and the imbalance exciter (vibration exciter) perform different tasks. The electric motor generates the torque to drive the imbalances, while the rotating imbalances of the imbalance exciter generate the forces necessary to move the vibrating plate.

[0016] As the power of electric motor-driven vibrating plates increases, the mass and volume of the motors and imbalances increase accordingly, which leads to a significant increase in the overall construction volume.

[0017] DE 21 63 019 A1 discloses an electrically driven unbalance vibrator with a cage-type unbalance rotor. The unbalance rotor has a laminated core recessed in the form of a longitudinal groove extending over an angular range of less than 180° and open to the outside.

[0018] DE 24 07 721 A1 discloses another electrically driven unbalance vibrator with a similar structure.

[0019] DE 11 2016 000 636 T5 shows a vibration device for vibration compressors.

[0020] US 2003 / 108389 A1 discloses a system for electrically driving and vibrating a soil compaction roller.

[0021] US 6 025 668 A generally describes a reluctance motor with grooved stator poles.

[0022] DE 923 017 C shows a mechanical vibration exciter driven by an electric motor, in which a rotating imbalance is provided which can be changed by adjusting a mass which is movable relative to the rotating part.

[0023] The invention is based on the object of providing a soil compaction device driven by an electric motor which has a simplified and more compact design compared to the prior art.

[0024] The object is achieved by an unbalance exciter for a soil compaction device according to claim 1 and by a soil compaction device with the features of claim 10. Advantageous embodiments are specified in the dependent claims.

[0025] An unbalance exciter for a soil compaction device is specified, comprising an electric motor having a rotor and a stator at least partially enclosing the rotor, wherein the rotor has an unbalance mass which can be moved at least partially past an inner side of the stator during rotation of the rotor.

[0026] Thus, the rotor is not only designed as a component of the electric motor, but also serves as an unbalanced shaft, carrying the unbalanced mass to generate the desired vibration forces during motor operation. In particular, the rotor can thus serve simultaneously as the drive shaft of the electric motor and as an unbalanced mass. Accordingly, the rotor can also be referred to as an "unbalanced rotor."

[0027] The stator can be designed as a magnetic exciter of the rotor.

[0028] In this way, an unbalance exciter is specified which has a particularly compact design, since the drive motor and unbalance exciter components are no longer provided separately from one another, but are formed by a single unit.

[0029] Due to the unbalance mass integrated into the rotor of the electric motor, no additional unbalance shaft driven by the electric motor is required.

[0030] The unbalanced mass can be moved at least partially past the inside of the stator during rotation of the rotor. This means that at least part of the unbalanced mass is not axially offset from the stator, but rather is arranged axially at the same height as the stator. This part of the unbalanced mass belonging to the rotor thus moves through the space enclosed by the stator.

[0031] Although a further portion of the unbalanced mass can also be arranged axially offset from the stator, i.e., outside the space enclosed by the stator, it is essential for the invention that a significant portion of the unbalanced mass is integrated into the electric motor, i.e., enclosed by the stator.

[0032] The rotor may have an additional mass over part of its circumference as an unbalanced mass, with no counterweight provided opposite the rotor's rotational axis to compensate for the unbalanced mass. The principle of the unbalanced mass is that it creates a mass imbalance for the rotor. Only then can the desired unbalance, which is necessary to generate the vibrations, be achieved during rotor rotation.

[0033] The additional mass on the rotor causing the imbalance mass can amount to at least 5% of the total rotor mass. Only if this additional mass is significant, i.e., at least 5% of the total rotor mass, can the desired imbalance force and thus vibration effect be achieved during operation. For variants, even larger imbalance masses can be used, for example, at least 10% or at least 15% of the total rotor mass.

[0034] The rotor can have multiple rotor poles distributed around its circumference, while the stator can have multiple stator poles distributed over a circular arc to realize an electromotive function in interaction with the rotor poles. It is unnecessary to go into the details of the construction of conventional electric motors suitable for the present application (e.g., reluctance motors, in particular switched reluctance motors, synchronous motors, asynchronous motors) in detail here, as they are widely known.

[0035] If necessary, suitable control devices, frequency converters, etc. may also be required to implement the electromotive function.

[0036] The unbalanced mass is designed as a mass that extends over part of the circumference of the rotor, with at least one rotor pole also being formed in the circumferential region of the rotor where the unbalanced mass is provided. This means that the unbalanced mass has the rotor poles necessary to achieve the electromotive function on its circumference. Additionally, mass elements can be provided on or between some of these rotor poles to thus form the unbalanced mass on the rotor.

[0037] At least one rotor pole is also formed in the circumferential area of ​​the rotor where no imbalance mass is provided. Here, the rotor structure corresponds to a "classic" rotor, which does not carry any additional imbalance mass in this area.

[0038] The rotor can be formed in one piece from a soft magnetic material. This soft magnetic material can be iron, in particular, which also advantageously has a high density to ensure a strong vibration effect from the unbalanced mass during rotor operation.

[0039] Alternatively, the rotor can also be assembled from different components, so that the "poles" and "unbalanced mass" components can be made of different materials. In particular, the unbalanced masses can be designed, for example, in the form of steel bodies that are attached in a suitable manner, for example by screw connections, to the actual rotor containing the poles. Conversely, a steel body can also serve as a base for the unbalanced masses, with the poles made of soft magnetic material being attached in a suitable manner to the steel body and supported by it. The poles can also be made, for example, from an electrical sheet.

[0040] In one variant, the stator can be cylindrical, i.e., completely enclosing the rotor around its circumference. The stator is then essentially designed as a hollow cylinder.

[0041] In an alternative embodiment, the stator can surround the rotor only by a circular segment on its circumference. In this case, the stator is designed as a partial stator, for example, as a hollow cylinder segment. In cross-section, the stator then essentially has the shape of a circular segment.

[0042] The stator can extend over a suitable angle along the circumference of the rotor, for example, up to 180°. An angle range of 90 to 270° is also possible.

[0043] For the operation of the electric motor, it is therefore not absolutely necessary for the stator to completely enclose the rotor's circumference. It may be sufficient for the electromagnetic fields generated by the stator to be generated only over a portion of the circumference.

[0044] The stator poles can be distributed over the inner circumference of the stator.

[0045] It has proven particularly advantageous if the electric motor is designed as a reluctance motor. While other motor principles are also possible, as explained above, the reluctance motor has proven particularly advantageous due to its principle.

[0046] In a reluctance motor, the torque in the rotor is generated exclusively by the reluctance force, so the motor is neither equipped with permanent magnets nor has electrical windings. This principle also eliminates any type of wear-prone slip rings and brushes. The rotor has distinct poles and is made of a highly permeable, soft magnetic material such as electrical steel.

[0047] The fact that the reluctance motor has a low torque density compared to permanent magnet machines such as synchronous motors is unproblematic for applications in an unbalance exciter. In this case, the unbalance mass only needs to be brought to the desired speed and maintained there. Once the unbalance exciter has started up, the reluctance motor's rated torque is sufficient to maintain the speed.

[0048] A frequency converter is usually used to control the reluctance motor, which also enables direct starting of the motor.

[0049] The described imbalance exciter can be used particularly advantageously in a soil compaction device. In particular, the soil compaction device comprises an upper mass and a lower mass movable relative to the upper mass, comprising a ground contact plate for soil compaction. A vibration decoupling device can be arranged between the upper mass and the lower mass to prevent or only minimally transmit the vibrations of the lower mass to the upper mass. An imbalance exciter of the type described above is arranged on the lower mass to apply an imbalance force to the ground contact plate.

[0050] Such a soil compaction device can in particular be a vibrating plate or vibrating plate, with which soil can be effectively compacted or stones can be vibrated into the soil.

[0051] The soil compaction device can be designed as a hand-held soil compaction device, in which case a guide device, such as a drawbar, is preferably attached to the top, via which the operator can guide the soil compaction device. In one variant, the soil compaction device can also be remotely controlled, in which case no guide drawbar is required. In particular, the unbalance or vibration forces generated by the unbalance exciter can achieve a driving movement (forward, backward) and also a steering movement (left turn, right turn) of the soil compaction device.

[0052] In one variant, the base mass can have at least two unbalance exciters, which can be controlled independently of one another by a control device. It is also possible for one unbalance exciter to contain several electric motors with rotors and associated unbalance masses, the rotation of which can each be individually controlled. This allows each of the unbalance exciters or each of the unbalance rotors to generate a different unbalance force, thus steering the soil compaction device.

[0053] For this purpose, the control device can be designed to enable electrical control of the electric motors in the unbalance exciters.

[0054] In particular, the control device can be used to effect different rotational positions of the respective rotors in the imbalance exciters. The rotational position is understood to be the respective angular position of the imbalance mass assigned to a rotor, i.e., in particular, the center of gravity of the imbalance mass. If, for example, two rotors are arranged axially next to one another on a ground contact plate, even slightly different rotational positions of the rotors relative to one another (phase position) and thus of the imbalance masses carried by them can cause a torque about the vertical axis (yaw axis) of the ground contact plate and thus of the soil compaction device, which in turn generates a rotation of the soil compaction device about the vertical axis. In this way, the soil compaction device can be easily steered.

[0055] In one variant of the soil compaction device, the imbalance exciter can be arranged on the upper side of the ground contact plate. This allows for a particularly effective transmission of the vibrations generated by the imbalance exciter into the ground contact plate, thus achieving effective soil compaction.

[0056] The ground contact plate may have a recess on its upper side, wherein the rotor of the unbalance exciter may be positioned on the ground contact plate in such a way that it protrudes at least partially into the recess.

[0057] A recess can also be understood as a space between two or more reinforcing ribs. Such ribs are often provided on the upper side of ground contact plates, which are usually manufactured as cast parts or welded constructions.

[0058] The unbalance exciter can be positioned on top of the ground contact plate in such a way that a portion of the rotor (the lower part of the horizontally positioned rotor) can protrude into the corresponding recess or the space between the reinforcing ribs. This allows the rotor to be at least partially recessed into the ground contact plate, significantly reducing its overall height. The rotor is positioned as close as possible to the underside of the ground contact plate.

[0059] The wall thickness between the bottom of the recess and the underside of the ground contact plate can range from 10 mm to 30 mm, e.g., approximately 20 mm. This makes it possible to position the rotor very low and keep the overall height low.

[0060] The distance between the outer surface of a virtual cylinder surrounding the rotor and the underside of the ground contact plate can range from 10 mm to 80 mm, e.g., between 30 mm and 40 mm, e.g., approximately 35 mm. The virtual cylinder thus circumscribes the rotor, or rather, the space occupied by the rotor during rotation. The distance between the outer surface of this virtual cylinder should be as small as possible to keep the overall height low and to effectively transmit vibrations to the ground contact plate.

[0061] The ground contact plate can form part of the housing of the unbalance exciter. In particular, the ground contact plate can form the lower part of the housing, while an upper part of the housing can be attached to the top of the ground contact plate in the manner of a cover. Accordingly, no separate housing component is required on the underside of the exciter, thus saving construction effort, material costs, and manufacturing costs.

[0062] Since the ground contact plate itself can be part of the housing of the unbalance exciter (here in particular the lower part of the housing), it is also possible to move the position of the rotor as downwards as possible.

[0063] With the measures described here, it is possible to achieve a compact design of the unbalance exciter on the ground contact plate, even with an electric motor-driven unbalance exciter of the type described above. Otherwise, the electric motor driving the unbalance exciter would take up a lot of space and cause the rotor with the unbalance mass to be positioned at a considerable distance from the compacting underside of the ground contact plate.

[0064] These and other advantages and features of the invention are explained below using an example with the aid of the accompanying figures. They show: Fig. 1 an example of a vibration plate known from the prior art; Fig. 2 a schematic section through an unbalance exciter according to the invention; Fig. 3 an example of an unbalance exciter mounted on a ground contact plate; Fig. 4 another example of an unbalance exciter mounted on a ground contact plate; and Fig. 5 A schematic representation of the distance between the rotor and its virtual surface and the underside of a ground contact plate.

[0065] The basic structure of a vibration plate has already been described above using Fig. 1 explained the state of the art.

[0066] According to the invention, instead of the vibration plate of Fig. 1 An electric motor drive is provided in place of the existing combustion engine 5, which is integrated into a single unit together with the unbalance exciter 8. A vibration plate according to the invention thus differs from the one in Fig. 1 The vibration plate shown is characterized primarily by the fact that an electric motor drive is provided and that the electric motor drive and the unbalance exciter comprise an integrated, common unit.

[0067] Fig. 2 shows a basic schematic cross-section through an unbalance exciter 20 according to the invention, which is also designed as an electric motor.

[0068] The unbalance exciter 20 according to the invention has a rotor 21 and a stator 22. As Fig. 2 As shown, the stator 22 preferably does not completely enclose the rotor 21 in a sleeve-like manner over 360° around the circumference. Rather, according to a preferred embodiment of the invention, the stator 22 is designed as a partial stator in the form of a semi-cylindrical sleeve and extends only over an angle of 180°.

[0069] Several rotor poles 23 (in the example shown, a total of eight rotor poles) are formed on the circumference of the rotor 21. In contrast, several stator poles 24 (in the example shown, a total of six stator poles) are distributed around the (half) circumference of the stator. The stator poles 24 are arranged in Fig. 2 numbered 1 to 6.

[0070] In the Fig. 2 In the rotor 21 shown, the spaces between the rotor poles 23 in the lower area are filled by additional masses 25 integrally connected to the rotor poles 23 (in the example shown, a total of four masses 25), which together form an unbalance mass. In particular, these mass elements 25 are not assigned any counterweights, such as Fig. 2 For example, the rotor 21 in the upper half of the picture Fig. 2 the spaces between the rotor poles 23 are left free.

[0071] Accordingly, due to the asymmetrical mass distribution during rotation, the rotor 21 generates a considerable unbalance force, which can advantageously be introduced directly into the ground contact plate 7 of the vibrating plate and serve to compact the soil.

[0072] The imbalance exciter 20 shown and the electric motor implemented thereby are advantageously designed as a reluctance motor. In particular, the electric motor can be designed as a switched reluctance motor. Accordingly, the stator poles 24 are switched through one after the other, namely in the pole combinations 4-1, 5-2, 6-3. For this purpose, a control device (not shown) is provided, which may include, among other things, a frequency converter.

[0073] In the described electromagnetic imbalance exciter 20, the rotor 21 is thus designed both as the drive shaft of the motor and as the imbalance shaft. The stator 22 serves as the magnetic exciter of the rotor 21. This allows for a very compact design of the imbalance exciter 20, keeping costs, weight, and volume within defined limits.

[0074] In an advantageous variant, the electric motor realized by the unbalance exciter 20 can utilize the physical properties of a reluctance motor, in which the rotor torque is generated by the reluctance force. The active part of the motor is neither equipped with magnets, nor are there any electrical windings, short-circuit bars, or similar components on the rotor 21, as is common in induction motors. Wear-prone slip rings and brushes are also absent.

[0075] The pronounced rotor poles 23 of the rotor 21 can be made of a soft magnetic material with high permeability, as is also used in electric motors.

[0076] In particular, two designs of the rotor 21 are possible: On the one hand, the rotor 21 can be made entirely in one piece from the soft magnetic material. In one variant, the rotor 21 can also be assembled from several components. In particular, it is possible to manufacture the mass elements 25 as separate components from steel and then connect them to the remaining components of the rotor 21 in a suitable manner.

[0077] The commutation of the rotor 21 occurs via the electrically excited stator poles 24, which interact with the rotor poles 23. The operating principle in this case is that of a synchronous machine with a frequency converter individually assigned to the imbalance.

[0078] The structure shown allows the stator 22 to be assembled from subsegments, whereby—as already explained—it is not necessary to design the stator 22 as a cylinder, as is the case with conventional electric motors. The only decisive factor for the function of the machine is that rotation of the rotor 21 can be generated by switching the stator coils (stator poles 24).

[0079] Compared to induction machines, such a motor has a higher efficiency in synchronous operating mode.

[0080] Additionally, it is possible to adjust the rotor position by arranging and / or controlling the magnetically active poles 23, 24 of the stator 22 and rotor 21. If multiple unbalance rotors are provided in the unbalance exciter 20, the positions of the various unbalance rotors (rotors 21) can be adjusted relative to each other, allowing the direction of movement of the vibrating plate to be controlled without additional components (such as a hydraulic or mechanical unbalance adjustment).

[0081] Fig. 3 shows an example of a soil compaction device with ground contact plate 7 and unbalance exciter 20 mounted on it.

[0082] The unbalance exciter 20 has the rotor 21, which is rotatably mounted in the stator 22. The stator 22 is housed in an exciter housing 12, which is attached to the top of the ground contact plate 7.

[0083] In the Fig. 3 In the operating principle shown, the distance between the rotation axis of the rotor 21 and the underside of the ground contact plate 7 is relatively large.

[0084] Fig. 4 shows a variant in which this distance is significantly smaller.

[0085] For this purpose, the stator 22 is only half-shell-shaped, so that it surrounds the rotor 21 only over a circular segment on the circumference, similar to Fig. 2 The stator 22 extends over an angle of approximately 180 degrees.

[0086] On the upper side of the ground contact plate 7, a recess 13 is also provided, into which the rotor 21 projects. In this way, the rotor 21 can be brought very close to the underside of the ground contact plate 7, which is effective for compaction.

[0087] In particular, Fig. 5 in a schematic detail enlargement of Fig. 4 that the rotor 21 can be surrounded on its outer circumference by an imaginary virtual cylinder 14, the outer surface of which has a distance A to the underside of the ground contact plate 7. This distance can be very small and lie in a range from 10 mm to 80 mm, e.g., approximately 35 mm.

[0088] In the variant of Fig. 4 The exciter housing 12 is designed in half and forms the upper half, which is attached to the ground contact plate 7. The lower half of the exciter housing 12 is missing. Its function is taken over directly by the ground contact plate 7 itself or the recess 13.

[0089] The exciter housing 12 encloses the stator 22, which is also only half formed.

[0090] Because the lower half of both the exciter housing 12 and the stator 22 is missing, it is possible to move the position of the rotor 21 downwards relative to the ground contact plate 7 and to position the rotor 21 closer to the underside of the ground contact plate 7.

Claims

1. Unbalance exciter (20) for a ground compaction device, comprising - an electric motor which has a rotor (21) and a stator (22) which at least partially encloses the rotor (21); wherein - the rotor (21) has an unbalance mass (25) which can be moved past an inner side of the stator (22) at least partially during a rotation of the rotor (21); - the unbalance mass (25) is configured as a mass which extends over a part of the circumference of the rotor (21), characterised in that - at least one rotor pole (23) is also formed in the circumferential region of the rotor (21) in which the unbalance mass (25) is provided; and in that - at least one rotor pole (23) is also formed in the circumferential region of the rotor (21) in which no unbalance mass (25) is provided.

2. Unbalance exciter (20) as claimed in claim 1, wherein the rotor (21) has, over a part of its circumference, an additional mass as an unbalance mass (25), with respect to which no countermass to compensate for the unbalance mass is provided oppositely in relation to the axis of rotation of the rotor (21).

3. Unbalance exciter (20) as claimed in any one of the preceding claims, wherein the additional mass producing the unbalance mass (25) is at least 5 per cent of the total mass of the rotor (21).

4. Unbalance exciter (20) as claimed in any one of the preceding claims, wherein - the stator (22) has a plurality of stator poles (24) distributed over an arc of a circle in order to implement an electromotive function in cooperation with the rotor poles (23).

5. Unbalance exciter (20) as claimed in any one of the preceding claims, wherein the rotor (21) is formed in one piece from a soft magnetic material.

6. Unbalance exciter (20) as claimed in any one of the preceding claims, wherein the stator (22) surrounds the rotor (21) in the manner of a cylinder.

7. Unbalance exciter (20) as claimed in any one of claims 1 to 5, wherein the stator (22) surrounds the rotor (21) only over a circular segment on the circumference.

8. Unbalance exciter (20) as claimed in any one of the preceding claims, wherein the stator poles (24) are distributed over the inner circumference of the stator (22).

9. Unbalance exciter (20) as claimed in any one of the preceding claims, wherein the electric motor is designed as a reluctance motor.

10. Ground compaction device, comprising - an upper mass (1); - a lower mass (2) which is movable relative to the upper mass (1) and has a ground contact plate (7) for ground compaction; - a vibration decoupling device (3) acting between the upper mass (1) and the lower mass (2); and comprising - at least one unbalance exciter (20) as claimed in any one of the preceding claims, associated with the lower mass (2), for applying an unbalance force to the ground contact plate (7).

11. Ground compaction device as claimed in claim 10, wherein the lower mass (2) has at least two unbalance exciters (20) which can be activated independently of one another by means of a control device.

12. Ground compaction device as claimed in claim 11, wherein different rotational positions of the respective rotors (21) in the unbalance exciters (20) can be effected by means of the control device.

13. Ground compaction device as claimed in any one of claims 10 to 12, wherein the unbalance exciter (20) is arranged on an upper side of the ground contact plate (7).

14. Ground compaction device as claimed in any one of claims 10 to 13, wherein - the ground contact plate (7) has a recess on its upper side; and wherein - the rotor (21) is positioned on the ground contact plate (7) such that it protrudes at least partially into the recess.

15. Ground compaction device as claimed in claim 14, wherein a wall thickness between a bottom of the recess and an underside of the ground contact plate (7) is in a range of 10 mm to 30 mm.

16. Ground compaction device as claimed in any one of claims 10 to 15, wherein a distance (A) of a lateral surface of a virtual cylinder, which circumscribes the rotor (21), to an underside of the ground contact plate (7) is in a range of 10 mm to 80 mm, in particular in a range of 30 mm to 40 mm, in particular is 35 mm.

17. Ground compaction device as claimed in any one of claims 10 to 16, wherein the ground contact plate (7) forms a part of a housing of the unbalance exciter (20).