DE102021200285A1 - Compaction vehicle in which a travel drive and a vibration unit are supplied with pressurized fluid from a common supply point - Google Patents

Abstract

The invention relates to a compaction vehicle (10) with at least one roller (20) for dynamically compacting a subsoil (11), the compaction vehicle (10) being in drive connection with at least one first hydraulic machine (21), with at least one roller (20) having a vibrating unit (30), which is drive-connected to an associated second hydraulic machine (31).According to the invention, the at least one first, the at least one second and one third hydraulic machine (21; 31; 41) are each connected to a common supply point (50 ) and are each connected to a common tank on the low-pressure side, so that they form an open hydraulic circuit, with the named connection to the supply point being continuously releasable in each case in such a way that a high pressure occurs in the at least one first, in the at least one second and in the third hydraulic machine (21; 31; 41) substantially equal to the pressure at the supply ngsstelle (50), wherein the at least one first, the at least one second and the third hydraulic machine (21; 31; 41) each have an adjustable displacement volume, with a displacement volume of the at least one second hydraulic machine (31) being adjustable such that the desired vibration intensity (81) results while the said connections to the supply point (50) are released.

Description

The invention relates to a compaction vehicle according to the preamble of claim 1.

From the EP 1342849 B1 a compaction vehicle in the form of a road roller is known. The compaction vehicle has two circular-cylindrical rollers, which roll on a subsoil in order to smooth it out. At least one of the rollers can be equipped with a vibrating unit to improve soil compaction.

From the DE 10 2010 056 531 A1 Another compaction vehicle is known, showing the motors which drive the roller and the vibratory unit. A hydraulic motor is specified as a possible embodiment of the motors mentioned.

A large variety of such compression vehicles is known from the prior art, and these can include up to six hydraulic motors. It would now be obvious to supply all these hydraulic motors with pressurized fluid in an open hydraulic circuit with a common pump, the direction of rotation and the rotational speed of each hydraulic motor being controlled with an associated valve. However, the throttling losses occurring in such valves are very large. For this reason, hydraulic motors are usually operated in a closed, hydraulic circuit, with the rotational speed and direction of rotation being set by adjusting the stroke volumes of the hydraulic machines in question. In a closed hydraulic circuit, however, it is not possible to connect any number of hydraulic motors to a common pump. A maximum of two hydraulic motors can usually be connected to a common pump and only if the two hydraulic motors are exposed to comparable loads.

Accordingly, a compression vehicle constructed in this way has several pumps, each of which is operated with a few associated hydraulic motors in a closed hydraulic circuit.

The aim of the invention is to create a compression vehicle with a hydraulic drive, with any configuration of hydraulic motors or first and second hydraulic machines being able to be implemented. In this case, ideally only a single pump or third hydraulic machine should be used in order to supply all hydraulic motors or first and second hydraulic machines with pressure fluid. Valves and the associated throttling losses in the primary energy transmission from the third hydraulic machine to the first and second hydraulic machines should be dispensed with as completely as possible.

According to claim 1, it is proposed that the at least one first, the at least one second and one third hydraulic machine are each connected to a common supply point on the high-pressure side and to a common tank on the low-pressure side, so that they form an open hydraulic circuit, with said connection to supply point can be continuously released in such a way that a high pressure in the at least one first, in the at least one second and in the third hydraulic machine is essentially equal to the pressure at the supply point, with the at least one first, the at least one second and the third hydraulic machine each have an adjustable displacement volume, wherein a displacement volume of the at least one second hydraulic machine can be adjusted in such a way that the desired vibration intensity results while the said connections to the supply point are released.

The vibration unit preferably comprises at least one mass which can be rotated with respect to an axis of rotation and whose center of gravity is arranged away from said axis of rotation, the at least one mass being in rotary drive connection with an associated second hydraulic machine. A plurality of masses are preferably provided, the eccentricity and direction of rotation of which are matched to one another in such a way that the sum total is an oscillating acceleration force which is aligned essentially perpendicularly to the substrate. The vibration unit is preferably arranged inside the roll in question.

A continuously releasable connection is to be understood on the one hand as a connection that is permanently open, and most preferably has a constant, small flow resistance. However, the continuously releasable connection can also be formed by a switching valve which has at least two discrete switching positions, the connection having a constant, small flow resistance in each switching position. There can be a switching position that is designed as a locked position, so that the associated hydraulic machine is clamped hydraulically in a torque-proof manner. For example, the direction of rotation of the associated hydraulic machine can be reversed with the switching valve, without the hydraulic machine having to be adjustable beyond the displacement volume of zero. There should be no continuously adjustable valve, as is usual with a hydraulic motor in an open circuit.

The supply point is preferably a space filled with pressurized fluid, with essentially the same pressure prevailing in the entire space mentioned. The supply point is preferably formed by an elongated line. The supply point is preferably not small in the form of a point, rather it has a spatial extent.

A hydraulic machine is to be understood as meaning a machine which converts hydraulic power into mechanical power in the form of a rotary movement and vice versa. The hydraulic machines mentioned are preferably axial piston machines. The at least one first and/or the at least one second hydraulic machine and the third hydraulic machine are preferably designed in a bent-axis design. This means that all hydraulic machines can be designed in such a way that they can be adjusted beyond the displacement volume of zero. For this reason, the bent-axis design that is otherwise preferred for hydraulic motors is not preferred. Said open hydraulic circuit is preferably operated with a liquid pressurized fluid, most preferably hydraulic oil being used.

Advantageous developments and improvements of the invention are specified in the dependent claims.

It can be provided that a direction of rotation of the at least one first hydraulic machine can be reversed by adjusting the displacement volume in question while the flow direction of the first hydraulic machine in question remains the same. The displacement volume of the at least one first hydraulic machine can therefore be adjusted beyond the zero displacement volume. This allows the direction of travel of the compaction vehicle to be reversed while the vibratory drive continues to run unchanged. The back and forth driving of the compaction vehicle, which is often encountered when compacting a road surface, with the vibration unit continuing to run constantly, can therefore be carried out without any problems. Changing the direction of travel can be done very gently. The direction of rotation of the at least one second hydraulic machine can also be reversed by adjusting the displacement volume. Depending on the design of the vibration unit, different vibration properties can be achieved in this way.

Provision can be made for the supply point to be connected to a hydraulic accumulator. For the controllability of the entire hydraulic drive, it is particularly advantageous if the pressure at the supply point maintains an essentially constant predetermined value. This predetermined value can change if the desired operating state changes, so it is only temporarily constant as long as the desired operating state does not change. As will be explained below, this pressure value is preferably set by adjusting the displacement volume of the third hydraulic machine. However, this regulation reacts comparatively sluggishly when the pressure at the supply point changes abruptly due to rapidly changing external loads on the at least one first or the at least one second hydraulic machine. With the hydraulic accumulator, such abrupt changes in the pressure at the supply point can be mitigated in such a way that the pressure regulation by means of the third hydraulic machine works sufficiently quickly. The filling and discharging speed of the hydraulic accumulator is preferably set in each case in such a way that the entire compaction vehicle has an optimally low energy consumption. A valve unit can be assigned to the hydraulic accumulator, which valve unit controls the exchange of pressurized fluid between the supply point and the hydraulic accumulator depending on the pressure at the supply point. This is intended in particular to prevent the hydraulic accumulator from being excessively filled. Furthermore, it should be avoided that an empty hydraulic accumulator disturbs the function of the hydraulic drive.

Two or more rollers can be provided, each of which is in rotary drive connection with its own first hydraulic machine, with all of the first and all of the second hydraulic machines being connected to the same supply point and the same tank. A separate first hydraulic machine is preferably assigned to each roller. Each roller is preferably assigned its own vibration unit with its own second hydraulic machine. In this case, the present invention is particularly useful since, compared to a conventional compression vehicle, a particularly large number of pumps or third hydraulic machines can be dispensed with.

Provision can be made for the supply point to be connected to a pressure sensor, with the displacement volume of at least one second hydraulic machine being adjustable as a function of the pressure measured by the pressure sensor and as a function of the desired vibration strength. The corresponding relationship is preferably stored in a characteristic map. The adjustment preferably takes place in the form of a control or a pilot control. This means that expensive controllers can be dispensed with. The positioning accuracy that can be achieved is often sufficient for a vibration unit.

Provision can be made for the supply point to be connected to a pressure sensor, with the displacement volume of the third hydraulic machine being adjustable as a function of the pressure measured by the pressure sensor. In a conventional hydraulic drive, one would prefer a pressure control working with a hydraulic pressure regulator at this point, since this has proven itself and works very reliably. The hydraulic pressure control also copes well with the strong pressure fluctuations that are often encountered in a hydraulic drive. Electronic pressure control is nevertheless preferred within the scope of the present invention, even though a high level of computing power has to be installed in the control device in order to achieve a control quality that is comparable to conventional hydraulic pressure control. As can be seen from the method explained below, the target value of this regulation should be adapted very flexibly to the current working conditions of the compaction vehicle. This is much easier to implement with an electronic pressure control than with a hydraulic pressure control. Furthermore, the proposed pressure sensor can be used when adjusting the at least one first and the at least one second hydraulic machine, this representing a preferred embodiment of the invention. The single pressure sensor can therefore be used for three different purposes.

A first control circuit can be provided, the actual variable of which is the pressure measured with the pressure sensor, the manipulated variable of which is the displacement volume of the third hydraulic machine. As a result, the pressure at the supply point is adjusted to a value specified by a target variable. The pressure mentioned is therefore no longer dependent on the driving resistance that the compaction vehicle has to overcome when driving. It is likewise not dependent on the set vibration strength or on the drive torque of the at least one second hydraulic machine.

The corresponding setpoint variable is preferably selected in such a way that the desired speed can be achieved at the at least one first hydraulic machine, with the stated speed determining the driving speed of the compression vehicle. The aim is to keep the pressure at the supply point as low as possible in order to save energy. The speed of the at least one first hydraulic machine is preferably measured at least indirectly with a first speed sensor.

It should be noted that all rollers typically rotate at the same peripheral speed, which is equal to the ground speed of the compactor vehicle. Accordingly, a single first speed sensor is normally sufficient. If slippage on the rollers is to be feared, a plurality of first speed sensors are preferably used in order to detect this slippage. The speed of the third hydraulic machine is preferably measured with a third speed sensor, with the corresponding measured value being taken into account in the regulation mentioned, in particular in determining the setpoint of the first control loop.

Accordingly, protection is claimed for a method in which a target value of the first control circuit is selected as a function of the desired driving speed of the compaction vehicle and/or as a function of the desired vibration intensity. With regard to the driving speed, for example, the drive torque of the rollers can be determined, which is necessary to reach the driving speed. The minimum required pressure at the supply point results from the maximum displacement volume of the first hydraulic machine. The same can be done with regard to the vibration intensity. The highest of the pressures determined in this way is decisive for determining the target value. The setpoint variable of the first control loop is preferably set in the form of a control, ie without feedback.

Provision can be made for at least one second hydraulic machine to be assigned a second speed sensor, by means of which a speed of the second hydraulic machine in question can be measured, with a second control circuit being provided whose actual variable is a measured value of the second speed sensor, the manipulated variable of which is the displacement volume of the relevant second hydraulic machine is. This allows the vibration strength to be adjusted very precisely. The intensity of the vibrations essentially does not fluctuate on changing surfaces with different damping characteristics. The target variable of the second control circuit corresponds to the speed desired at the second hydraulic motor in question. This in turn is proportional to the desired vibration intensity. The second control loop is preferably combined with the characteristics map explained further above, which then works as a so-called pilot control.

Provision can be made for the supply point to be formed by a line which extends over at least 50% of the length of the compaction vehicle in the direction of travel. This means that all hydraulic machines of the compaction vehicle can be connected to the supply point without any problems. It goes without saying that the free cross-sectional area of said line is preferably selected to be large enough that at all points essentially the same pressure prevails in the line.

Provision can be made for the at least one first hydraulic machine, the at least one second hydraulic machine and/or the third hydraulic machine each to have an actuating device which is set up to adjust the displacement volume of the relevant hydraulic machine essentially proportionally to an actuating signal. Said adjusting device preferably works hydraulically. It preferably includes an actuating cylinder, an actuating valve and a position sensor. Preferably, it includes a fourth control circuit, which regulates the displacement volume to a desired value specified by the control signal using the aforementioned components.

Provision can be made for at least one first hydraulic machine to be assigned a third control loop, the actual variable of which is the speed of the relevant first hydraulic machine, the manipulated variable of which is the displacement volume of the relevant first hydraulic machine. If several first hydraulic machines are provided, their displacement volume is set either the same or in a fixed ratio. In this case, too, only a single third control loop is provided. The driving speed can thus be set particularly precisely. As an alternative to this, it is conceivable to set the displacement volume of at least one first hydraulic machine by means of a further characteristic map, which has the desired driving speed and the measured value of the pressure sensor at the supply point as input variables.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

• 1 eine grobschematische Seitenansicht eines erfindungsgemäßen Verdichtungsfahrzeugs;
• 2 einen Schaltplan des hydraulischen Antriebs des Verdichtungsfahrzeugs nach 1;
• 3 die in 2 fehlende Ansteuerungsteuerung der zweiten Hydromaschine; und
• 4 eine alternative Verbindung der zweiten Hydromaschine mit der Versorgungsstelle und dem Tank.

The invention is explained in more detail below with reference to the accompanying drawings. It shows:

• 1 a highly schematic side view of a compression vehicle according to the invention;
• 2 a circuit diagram of the hydraulic drive of the compaction vehicle 1 ;
• 3 in the 2 lack of control of the second hydraulic machine; and
• 4 an alternative connection of the second hydraulic machine to the supply point and the tank.

1 shows a roughly schematic side view of a compaction vehicle 10 according to the invention. The present compaction vehicle 10 is designed in the form of a road roller, with which a subsurface 11 in the form of a freshly asphalted road can be rolled smooth. In the present case, the compaction vehicle 10 has two rotatable, circular-cylindrical rollers 20 which roll on the subsoil in order to smooth it. In the present case only the front roller 20 is driven by a first hydraulic machine 21 . It should be noted here that 1 shows an extremely simple embodiment of a compaction vehicle according to the invention. However, the present invention saves a lot of costs when many first and second hydraulic machines 21; 31 find use, for example, when all rollers 20 are driven and provided with a vibration unit 30 at the same time. The compaction vehicle can also have more than two rollers 20 .

Only the rear roller 20 is provided with a vibration unit 30 here. With the vibration unit 30, a pulsating force acting perpendicularly to the subsoil 11 is to be exerted on the assigned roller 20, so that the subsoil 11 is better compacted. A rotatably mounted mass 33 can be used for this purpose, for example, the center of gravity of which is arranged off the axis of rotation or eccentrically. This mass 33 is in rotary drive connection with an associated second hydraulic machine 31 .

Reference should also be made to the supply point 50 in the form of a line 54 which extends over at least 50% of the length of the compaction vehicle 10 in the direction of travel 15 . So everyone can in 2 and 3 shown connections to the first and second hydraulic machine 21; 31 to be produced. In the line 54 there is nevertheless essentially the same pressure everywhere.

2 FIG. 12 shows a circuit diagram of the hydraulic drive of compaction vehicle 10. FIG 1 . The hydraulic drive includes a supply point 50 in the form of an elongated line 54. The first, the second and the third hydraulic machine 21; 31; 41 connected at its high pressure side, with a permanently open, low-resistance fluid communication connection. No valves, throttles or the like are installed in this connection, so that the high pressure in the hydraulic machines 21; 31; 41 is substantially equal to the pressure at the supply point 50. The first, the second and the third hydraulic machine 21; 31; 41 are each designed as axial piston machines with adjustable displacement volume. The first and the second axial piston machine 21; 31 are preferably designed in swash plate design, whereby they are operated as a motor during most of the operating time. They are preferably adjustable beyond the displacement volume of zero. The third hydraulic machine 41 is preferably designed in the form of a swash plate, with it being operated as a pump most of the time. All hydraulic machines 21; 31; 41 are equipped with an adjusting device 13 which is set up in such a way that the displacement volume of the relevant hydraulic machine 21; 31; 41 is adjusted essentially proportionally to an associated control signal 14 . Accordingly, there is no hydraulic pressure and/or power control on the hydraulic machine 21; 31; 41 itself instead. Instead, the hydraulic drive is controlled as described below, with electronic control devices preferably being used.

The third hydraulic machine 41 is rotated by an associated drive motor 43 . The drive motor 43 is preferably a diesel engine, but any other type of motor, in particular an electric motor, can be used. The drive motor 43 preferably runs with a fixed direction of rotation. During most of the operating time, the third hydraulic machine 41 delivers pressurized fluid from the tank 12 to the supply point 50, working as a pump. Within the framework of the control according to the invention, however, it can also happen that pressure fluid flows from the supply point 50 via the third hydraulic machine 41 to the tank, with the third hydraulic machine 41 working as a motor and thus temporarily relieving the drive motor 43 .

The low-pressure sides of the first, second and third hydraulic machine 21; 31; 41 are each connected to the tank 12, resulting in an open hydraulic circuit. These connections to the tank are also open permanently and with little resistance, with preferably no valves, throttles or the like being arranged there. In principle, the entire hydraulic drive does not require any valves, the desired movement being achieved solely by adjusting the stroke volumes of the hydraulic machines 21; 31; 41 is brought about.

In the present case, however, the supply point 50 is assigned a valve unit 52 which is connected between the supply point 50 and an optional hydraulic accumulator 51 . With the hydraulic accumulator 51 peaks in the power requirement, for example when accelerating the vibration drive (No. 30 in 1 ), intercepted so that they do not overly load the drive motor 43, so that it does not have to be overly large. Furthermore, pressure peaks at the supply point 50 are intercepted by the hydraulic accumulator 51 . The valve unit 52 initially brings about an adjustment of a high pressure in the hydraulic accumulator 51 to a lower pressure at the supply point 50, so that the hydraulic accumulator 51 is discharged when it is sufficiently filled. It also causes the hydraulic accumulator 51 to be charged when the pressure inside it is less than the pressure at the supply point 50 . In this case, a predetermined charging volume flow is preferably not exceeded. The valve unit 52 can be purely hydromechanical. It is preferably electrically adjustable, being adjusted by the electronic control device 16 . The hydraulic accumulator 51 is preferably provided with a pressure sensor (not shown), which is connected to the electronic control device 16 so that the pressure in the hydraulic accumulator 51 can be regulated electronically.

With the first control circuit 60, a pressure is adjusted at the supply point 50, which is equal to the desired variable 63 of the first control circuit 60. This setpoint 63 is determined as a function of the desired travel speed of the compaction vehicle and the desired vibration strength of the vibration drive (No. 30 in 1 ) chosen. In this case, setpoint value 63 of first control circuit 60 is preferably selected to be so small that the adjustment range of first and second hydraulic machine 21; 31 is just about sufficient to achieve the desired operating parameters (travel speed, vibration intensity).

In the present case, the corresponding first controller 64 is designed as a PID controller, in which case a PI or an I controller can also be used. The first controller 64 is preferably implemented by an electronic controller 16 that includes a programmable digital computer. The difference between the setpoint variable 63 explained above and the actual variable 61 is supplied to the first controller 64 , a manipulated variable 62 which forms the manipulated signal 14 of the third hydraulic machine 41 being present at its output. The actual variable 61 of the first control loop 60 is the measured value of a pressure sensor 53 which is connected to the supply point 50 .

3 shows the in 2 lack of control of the second hydraulic machine 31. 2 and 3 together show a uniform hydraulic drive. 3 12 shows the most complex variant of the control, in which a pilot control is carried out by means of a characteristics map 80, with the pilot control being superimposed on a regulation with the second control circuit 70. There are applications in which the pilot control alone, without the second control loop 70, results in sufficiently good system behavior. There are also use cases where the second Control circuit 70 alone, without the pilot control, gives a sufficiently good system behavior.

The second control circuit 70 includes a second controller 74, which is designed here as a PID controller, although it can also be designed as a PI or I controller. The difference between the actual variable 71 and the setpoint variable 73 is fed to its input. The actual variable 71 is formed from the measured value of the second speed sensor 32, ie from the speed of the second hydraulic machine 31. The desired variable 73 corresponds to the speed of the second hydraulic machine 31, with which the desired vibration strength 81 is achieved. As already indicated, this control basically has an integral control behavior, in which case it subsequently reacts comparatively sluggishly to changes in setpoint variable 73 . This problem can be remedied with the pilot control.

The pilot control includes a characteristic map 80, which has the desired vibration intensity 81 and the measured value of the pressure sensor 53, ie the pressure at the supply point, as input variables. The characteristic map 80 gives the displacement volume to be set on the second hydraulic machine 31 as an output variable, with which the desired vibration intensity 81 is achieved at the current pressure at the supply point. Characteristic map 80 preferably includes a corresponding table of values, from which intermediate values are most preferably obtained by interpolation. This pilot control does not take into account, for example, that changing ambient temperatures also affect the required setting of the second hydraulic machine 31 . The second control circuit 70 counteracts this problem.

The output variables of characteristics map 80 and of second controller 74 are added, resulting in control signal 14 for second hydraulic machine 31 . One speaks here of a superimposition of a pilot control with a regulation.

4 shows an alternative connection of the second hydraulic machine 31 to the supply point 50 and the tank 12. In the embodiment according to FIG 2 these connections were permanently open. The embodiment after 4 is intended for cases in which the direction of rotation of the second hydraulic machine 31 is to be reversible, in which case no hydraulic machine that can be adjusted beyond the displacement volume of zero is to be used to save costs.

The second hydraulic machine 31 is therefore connected to a switching valve 34, which is designed as a 4/3-way valve. The switching valve 43 therefore has four connections and three switching positions. The switch positions are discrete switch positions, with essentially no intermediate positions in which the opening cross sections of the various connections change constantly.

The middle position is a locked position in which the second hydraulic machine 31 in question cannot move because it is hydraulically clamped. The connections to the tank 12 and the supply point 50 are blocked. in the in 4 left position of the switching valve 34, the second hydraulic machine rotates, for example, to the right, where it is in the in 4 right position of the switching valve 34 rotates to the left. As part of the reversal of the direction of rotation, the displacement volume is preferably set to zero or almost zero on the second hydraulic machine 31, while the switching valve 34 is adjusted. In the two outer switching positions, the connections between the second hydraulic motor 31 and the tank 12 or the supply point 50 are continuously released. A continuous adjustment of the corresponding opening cross-sections preferably does not take place while the vibration unit (No. 30 in 1 ) runs.

It is understood that the first hydraulic machine (No. 21 in 2 ) can be connected to the supply point 50 and the tank 12 in an analogous manner with an analog switching valve.

Reference List

10

compaction vehicle

11

underground

12

tank

13

actuator

14

control signal

15

driving direction

16

electronic control device

20

roller

21

first hydraulic machine

22

first speed sensor

30

vibration unit

31

second hydraulic machine

32

second speed sensor

33

eccentric mass

34

switching valve

41

third hydraulic machine

42

third speed sensor

43

drive motor

50

supply point

51

hydraulic accumulator

52

valve unit

53

pressure sensor

54

Management

60

first loop

61

Actual value of the first control loop

62

Manipulated variable of the first control loop

63

Setpoint of the first control circuit

64

first controller

70

second control loop

71

Actual value of the second control loop

72

Manipulated variable of the second control loop

73

Set point of the second control loop

74

second regulator

80

map

81

desired vibration level

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 1342849 B1 [0002]
• DE 102010056531 A1 [0003]

Claims (12)

Compaction vehicle (10) with at least one roller (20) for dynamically compacting a subsoil (11), the compaction vehicle (10) being in drive connection with at least one first hydraulic machine (21), with at least one roller (20) having a vibration unit (30) which is drive-connected to an associated second hydraulic machine (31), characterized in that the at least one first, the at least one second and one third hydraulic machine (21; 31; 41) are each connected to a common supply point (50) on the high-pressure side and are each connected to a common tank (12) on the low-pressure side, so that they form an open hydraulic circuit, with the named connection to the supply point being continuously releasable in each case in such a way that a high pressure occurs in the at least one first, in the at least one second and in the third hydraulic machine (21; 31; 41) substantially equal to the pressure at the supply point le (50), wherein the at least one first, the at least one second and the third hydraulic machine (21; 31; 41) each have an adjustable displacement volume, with a displacement volume of the at least one second hydraulic machine (31) being adjustable such that the desired vibration intensity (81) results while the said connections to the supply point (50) are released. Compaction vehicle (10) after claim 1 wherein a direction of rotation of the at least one first hydraulic machine (21) can be reversed by adjusting the displacement volume in question, while the flow direction of the first hydraulic machine (21) in question remains the same. Compaction vehicle (10) according to one of the preceding claims, in which the supply point (50) is connected to a hydraulic accumulator (51). Compaction vehicle (10) according to one of the preceding claims, wherein two or more rollers (20) are provided, each of which is in rotary drive connection with its own first hydraulic machine (21), with all of the first and all of the second hydraulic machines (21; 31) being connected to the same supply point (50) and the same tank (12) are connected. Compaction vehicle (10) according to one of the preceding claims, wherein the supply point (50) is connected to a pressure sensor (53), the displacement volume of at least one second hydraulic machine (31) depending on the pressure measured with the pressure sensor (53) and depending on the desired Vibration strength (81) is adjustable. Compaction vehicle (10) according to one of the preceding claims, wherein the supply point (50) is connected to a pressure sensor (53), the displacement volume of the third hydraulic machine (41) being adjustable as a function of the pressure measured by the pressure sensor (53). Compaction vehicle (10) after claim 6 , A first control loop (60) being provided, the actual variable (61) of which is the pressure measured by the pressure sensor (53), the manipulated variable (62) of which is the displacement volume of the third hydraulic machine (41). Compaction vehicle (10) according to one of the preceding claims, in particular according to claim 7 , wherein at least one second hydraulic machine (31) is assigned a second speed sensor (32), by means of which a speed of the relevant second hydraulic machine (31) can be measured, a second control circuit (70) being provided, the actual variable (71) of which is a measured value of the second speed sensor (32), its manipulated variable (72) being the displacement volume of the second hydraulic machine (31) in question. Compaction vehicle (10) according to one of the preceding claims, wherein the supply point (50) is formed by a line (54) which extends over at least 50% of the length of the compaction vehicle (10) in the direction of travel (15). Compaction vehicle (10) according to one of the preceding claims, wherein the at least one first hydraulic machine (21), the at least one second hydraulic machine (31) and/or the third hydraulic machine (41) each comprise an actuating device (13) which is set up to set the displacement volume of the relevant hydraulic machine (21; 31; 41) substantially proportionally to an actuating signal (14). Compaction vehicle (10) according to one of the preceding claims, wherein at least one first hydraulic machine (21) is assigned a third control circuit, the actual variable of which is the speed of the relevant first hydraulic machine (21), the manipulated variable of which is the displacement volume of the relevant first hydraulic machine (21). . A method wherein a compaction vehicle (10) according to claim 7 is used, with a setpoint (63) of the first control circuit (60) depending on the desired driving speed of the Compaction vehicle (10) and / or depending on the desired vibration strength (81) is selected.

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