DE102008013846A1 - Agricultural work machine with noise-damped cabin - Google Patents

Abstract

A self-propelled agricultural work machine with a driver's cab (18) and a noise source (10) outside the driver's cab (18), from which a vibration on a first path (21) in the cab (18) is transferable, has a compensator (38) which is drivable to the popped phase and amplitude to emit a sonic vibration that compensates for the vibration transmitted to the cab (18).

Description

The The present invention relates to a self-propelled agricultural Working machine such as a tractor, a forage harvester, a combine harvester or the like with a driver's cab and a noise source outside the cab, from the one vibration in the cab transferable is.

Such a work machine is off, for example US 2001/0044 685 A1 known. In this known work machine, a driver's cab is connected to the chassis via three actively controlled air bearings, which represent transmission paths for noise and vibrations that occur when driving over bumps from the chassis to the driver's cab. Although the effect of the three air bearings can be coordinated in such a way that gradients are compensated within certain limits and the cab retains a horizontal orientation even on sloping ground. However, the noise damping effect of the air bearings is not coordinated, so that superimposed on the air bearing transmitted structure-borne noise and transmitted through the air sound in the cab. In particular, when the work machine is used for noisy work, the noise level in the cabin can therefore easily reach a disturbing level for the driver.

EP 1 800 955 A2 proposes for noise damping in the cab of a work machine, an inner lining, communicate in the cavity resonators in the lining with the interior of the cabin. Such cavity resonators act by appropriate spectral components of the cabin noise to excite the resonators to vibrate and the vibration is damped in the resonator. Prerequisite for the effectiveness is that the resonance frequencies of the resonators coincide with the frequencies to be damped. Since the resonators are much smaller than the cabin itself, a damping of low natural vibrations of the cabin is not possible. In addition, the effectiveness of the noise attenuation is limited by the strength of the coupling between cabin and resonators. The larger the openings between the two, the more vibrational energy can enter the resonators, but the lower the quality of the resonators, ie, the lower is the proportion of the injected vibrational energy, which is actually destroyed in the resonators. Therefore, the performance of this known concept is limited.

task The invention is a self-propelled agricultural machine to create, which allows the noise level in the cab also in the performance of noisy work effectively limit.

The Task is solved by a self-propelled agricultural working machine with a driver's cab and a noise source outside the cab, from the one oscillation transferable on a first way in the driver's cab is a compensator element with a phase and amplitude the phase and amplitude matched to the transmitted vibration is drivable to emit a sound vibration, which is the compensated for vibration transmitted to the cab. By the vibration emitted by the compensator element the vibration can be extinguished from outside the noise level in the cabin is noticeably reduced. Since that Compensator element driven and not purely passive by the in The cabin is excited by existing vibrations, can be a significant stronger effect than passive ones Resonator with a coupling opening of comparable size.

Of course An agricultural machine can also have several sources of noise have, each of which as proposed here alone or can be mitigated with others.

Preferably the compensator element is part of a second transmission path from the noise source to the driver's cabin, its phase shift and / or attenuation / gain are adaptable. Thus, the movement of the compensator element changes bear the vibration behavior of the noise source, even before they have spread into the cabin, in contrast for passive damping via resonators, the first then be stimulated and take effect, if that Noise the cabin has already reached.

By doing the shares of the Cabin noise cancel each other out, a noise level can be achieved in the cabin, the is lower than the noise level resulting from the transmission from noise to a single of the transmission paths would result.

While Driving noise due to the mostly unperiodic contour of the busy underground are by nature broadband, that has Spectrum of machine operating noise caused by the Periodicity of the noise causing Machine movements usually a small number of narrowband intensity peaks. An effective noise cancellation in the frequency domain These power peaks can therefore be enough to reduce the noise level significantly reduce in the cabin.

Around possibly load-related frequency fluctuations of the machine movement It is sufficient if the transformer one on a periodically moving element of the noise source arranged frequency sensor and one of the frequency sensor detected frequency of the element tunable first frequency generator includes. This frequency generator is expediently on the strongest noise frequency of the noise source Voted; this may - depending on the structure of the noise source - to the detected frequency as well as a harmonic act of it.

Preferably the transmitter further comprises at least a second one tunable frequency generator, which is tuned to a harmonic of the tuning frequency the first frequency generator is tuned.

Around an effective noise cancellation of the two Frequencies should allow phase shifting and / or Damping for both frequencies independently be adaptable to each other. If such an adaptation is not continuous, but only taking place at certain times are changes in the amplitude and phase relationship of the two frequencies perceptible in the driver's cab. As a result, the driver is from the normal operating noise shielded, changes the operating noise, which gives him information about any interference or other requiring a response Deliver events, but remain clearly perceptible.

at a preferred application includes the noise source a crop processing, oscillating or rotating element such as a chopper drum, and the frequency sensor is arranged to detect the movement frequency of this element.

If the rotating element is occupied by an integer number n of tools is, the tuning frequency of the first frequency generator can suitably be n times the rotational frequency of the rotating element.

The Tuning frequency should be tuned to a cavity mode of the driver's cab be because noises whose frequency coincides with such a cavity mode, tend to be resonantly amplified in the cab too and thereby a disturbing volume level reach if no appropriate countermeasures are taken. In addition, cavity modes are particularly effective Suppress because there are no run-time effects that occur can cause locally different oppression d. H. the phases of the standing wave to be suppressed and the wave radiated from the compensator element are location independent.

Preferably at least the frequency of the basic mode of the driver's cab is in Tuning range of the frequency generator.

Around a noise cancellation in a closed To enable control loop, a microphone can be used for recording the noise level in the cabin and a control circuit for adapting phase shift and / or damping / amplification the adaptable second transmission path based on the recorded Noise level be provided. Such a control circuit can be continuously in operation to reduce the noise level to minimize at any time; but it may also be appropriate be to operate them from time to time and while fixed values of phase shift and / or damping / gain subsequently to make changes to the Audible noise generated by the noise source close.

When supporting noise-suppressing measure can be a swinging wall surface of the cab to an excitable at the oscillation frequency of the wall surface Resonator be coupled. By getting energy, otherwise only the vibration of the wall surface stimulates, on the wall surface and distributes the resonator, the vibration amplitude of the wall surface and thus reduces the noise emission.

Preferably if the resonator is damped more strongly than the wall surface, in order to continuously remove vibration energy from it.

When swingable wall surface comes in particular one Window of the cab and as a resonator on the disc mounted windscreen wiper into consideration.

Further Features and advantages of the invention will become apparent from the following Description of embodiments with reference on the attached figures. Show it:

1 a schematic representation of a forage harvester as an example of an agricultural machine according to the invention;

2 a typical spectrum of the cabin noise of a forage harvester with or without noise damping according to the invention;

3 a block diagram of an adaptable transformer; and

4 a schematic representation of a Auxiliary noise reduction device.

1 shows a schematic representation of a self-propelled forage harvester 1 as an example of a working vehicle according to the invention. The forage harvester 1 is equipped with a chassis 4 a vehicle frame 6 , one on the front of the vehicle frame 6 mounted recording attachment 8th which serves to pick up crops from the ground and feed the material into a conveyor channel, and a chopper plant 10 , a post-accelerator 12 and a chute 14 , which are successively arranged in the delivery channel, a motor 16 for driving the chassis 4 and the moving parts of the receiving attachment 8th , the shredder 10 and the post-accelerator 12 and a driver's cab 18 ,

The component of the forage harvester 1 that's the strongest contributor to his in the cab 18 audible operating noise is a chopper drum of the shredder 10 , On a shaft of the chopper drum is an angle encoder 20 arranged, which delivers a signal pulse per revolution or per integer fraction of a revolution of the cutterhead. These signal pulses are from a control circuit, not shown, of the engine 16 received to regulate its performance so that the speed of the cutterhead despite varying load on the cutterhead by the different crop flow remains in a predetermined range.

2 shows a typical spectrum of the in the cab 18 audible operating noise in the form of a bar graph with a resolution of three bars per octave. The cutterhead rotates with one of the control circuitry of the engine 16 regulated speed from 30 to 35 Hz (1800-2100 rpm), corresponding to the bar at the left edge of the diagram. As you can see, this only makes a small contribution to the operating noise; by far the majority of the noise power is attributed to frequencies in the range of 80 to 6000 Hz. In this frequency range, three beams at 250, 500 and 1000 Hz are particularly noticeable, which are significantly more powerful than their neighbors. They result from the fact that the chopper drum is equipped with nine circumferentially equally spaced groups of knives, ie they correspond to the fundamental frequency of the operating noise of the knives and their second and fourth harmonics in the frequency bands 9 × (30-35) Hz = 270- 315 Hz, 18 × (30-35) Hz = 540-630 Hz and 36 × (30-35) Hz = 1080-1260 Hz, respectively. Chopping drums with six, twelve or 18 knife groups are also common; For these, intensity peaks of the noise would result in correspondingly shifted frequencies.

Reduce the intensity of these spectral components to those of neighboring frequencies, such as hollow and hatched areas of the bars in 2 indicated, this is sufficient to suppress the noise level, for example, from about 92 to about 85 dB (A).

The invention provides to selectively suppress the blade frequency and its harmonics, by adding to the operating noise, which is known as structure-borne noise in forage harvesters 1 from the shredder 10 to the driver's cab 18 or directly as airborne sound propagated on another transmission path noise is superimposed, this second transmission path is adjusted in terms of phase shift and damping / amplification in order to achieve in the driver's cab an antiphase superimposition of the transmitted noise on the different ways. Such a second transmission path can be implemented in different ways, for example in the form of a hydraulic line containing a hydraulic fluid excited to vibrate in contact with a diaphragm on the chopper drum, and its vibrations are applied directly to a wall or wall of the cab 18 transferred as Kompensatorelement. Such a conduit may be length-adaptable to achieve phasing, for example it may include as adjustable attenuator a constriction of adjustable cross-section.

Preferred is an implementation of the second transmission path in electronic form, as in 3 shown. The figure shows the arranged on the shaft of the cutterhead angle sensor 20 and schematically with the 21 designated transmission path for body or airborne sound. The angle encoder 20 provides one pulse per revolution of the chopper shaft to a phase difference detector 22 , This forms together with a voltage controlled oscillator 24 and a frequency divider 26 a known PLL loop, the oscillator 24 a signal coupled to the rotation of the chopping drum phase at n times the rotational frequency of the chopper drum. In the present case, n is equal to four times the number of knife groups, ie n = 4 × 9 = 36, so that the output signal of the voltage-controlled oscillator 24 tuned to the fourth harmonic of the blade noise.

The frequency divider 26 consists here of three stages connected in series, a 1: 2 divider 26a , at whose output the second harmonic of the knife frequency can be tapped, a 1: 2 divider 26b whose output provides the fundamental frequency of the knives and a 1: 9 divider which provides the cutterhead frequency. The frequency divider 26c can be omitted if an angle encoder 20 is used, which provides nine pulses per revolution of the chopper shaft.

At the outputs of the oscillator 22 and the 1: 2 divider 26a . 26b are each RC members 28a . 28b . 28c and amplifiers 30a . 30b . 30c whose phase delay or amplification factor is connected by a control circuit 32a . 32b respectively. 32c is predetermined. These control circuits 32a . 32b . 32c each have one over a narrow band filter 34a . 34b . 34c with a microphone 36 in the driver's cabin 18 connected signal input. The outputs of the amplifiers 30a . 30b . 30c are connected to a speaker 38 as a compensation element in the driver's cab 18 connected.

In a tuning operation mode of the control circuits 32a , b, c, these each vary the RC elements and amplifiers 28a , b, c, resp. 30a , b, c predetermined phase shifts and gain factors, the signal level at its input and thus the operating noise in the cabin 18 to minimize.

As the phase of the knife movement over the angle encoder 20 is detected and the propagation conditions of sound between the chaff 10 and the driver's cab 18 do not vary significantly over time, need the control circuits 32 not constantly working in tuning mode, but once found optimum phase delays and gains can be maintained over long time intervals. Changes in operating noise, giving the driver important information about the function of the forage harvester 1 can not be shielded from him.

If during operation of the forage harvester at all ever a re-optimization is needed, this can become restrict to the gain factors, since these depending on the processed crop and the strength of the crop stream can vary. The occurring during the sound propagation Phase delays essentially change Not.

The filters 34 each may have a fixed pass band corresponding to 36 times, 18 times, and 9 times the control bandwidth of the cutterhead, respectively; In order to achieve a higher selectivity, tuneable filters may also be used whose passband is centered around the frequency of a reference signal supplied to them, which in the case of the filter 34a to the output signal of the oscillator 24 , at the filter 34b to the output signal of the frequency divider 26a and the filter 34c to the output signal of the frequency divider 26b can act.

The noise suppression device of 3 is particularly useful then applicable when the knife frequency or one of their harmonics at the same resonant frequency of a cavity mode of the cab 18 is because in such cases, the noise level in the cabin, when not actively attenuated, can reach very high values due to resonance peaking. In particular, low cavity modes, especially the fundamental mode, with the structure of the 3 very effectively damped.

Another tool for noise reduction in the cabin is in 4 shown. One on a disc 40 The windscreen wiper arranged in the cab includes one on an arm 41 pivoting movable wiper blade 42 and on an opposite side of the disc 40 an electric motor 43 for driving the movement of the arm 41 , The motor 43 is with the disc 40 via a spring, here in the form of a dissipative rubber buffer 44 connected, which is a vibration of the engine 43 in relation to the disc 40 with a resonant frequency similar to a natural frequency of the disc 40 allows. That's how the disk stirs 40 if it is resonantly excited by operating noise, at the same time the engine 43 to vibrate, causing the disc 40 Vibration energy withdrawn and in the rubber buffer 44 is dissipated. This reduces the swing stroke of the disc 40 and as a result, their noise emission.

A corresponding damping effect is also achievable if the anchor 45 of the motor 43 axially movable with respect to its stand 46 is suspended. An attenuation of the anchor vibration is then with the help of the anchor 45 carrying springs and deflected by its vibration springs realized; it is also conceivable, the anchor vibration by between anchor 45 and stand 46 to dampen induced currents.

The motor 43 is here in the middle of the disc 40 arranged. This allows a continuously rotating wiping movement without reversal of direction, which is the mechanical structure or the electrical control of the motor 43 simplified. In addition, there is the engine 43 at the center of the disc 40 also at the point where the fundamental vibration of the disc 40 reaches its highest amplitude and is therefore most effectively attenuated by the windscreen wiper.

Though the invention above is specific to a forage harvester has been described to those skilled in the Hand that they also work on other agricultural machines, like for example on a combine harvester to dampen the transmission operating noise of the threshing drum, the shaking floors or other periodically moving aggregates of the combine harvester can be used.

1

Forage

4

landing gear

6

vehicle frame

8th

recording intent

10

Häckselwerk

12

post-accelerator

14

chute

16

engine

18

cab

20

angle encoder

21

transmission path

22

Phase difference detector

24

VCO

26

frequency divider

28

RC element

30

amplifier

32

control circuit

34

filter

36

microphone

38

speaker

40

disc

41

poor

42

wiper blade

43

engine

44

rubber buffers

45

anchor

46

stand

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 2001/0044685 A1 [0002]
• EP 1800955 A2 [0003]

Claims (13)

Self-propelled agricultural machine with a driver's cabin ( 18 ) and a noise source ( 10 ) outside the driver's cab ( 18 ), of which a vibration on a first way ( 21 ) in the driver's cab ( 18 ) is transferable, characterized in that a compensator element ( 38 ) is drivable with a phase and amplitude adapted to the phase and amplitude of the transmitted oscillation, in order to emit a sound vibration which is transmitted to the driver's cabin ( 18 ) compensates for the transmitted vibration. Work machine according to claim 1, characterized in that the compensator element ( 38 ) Part of a second of the noise source ( 10 ) to the cabin ( 18 ) is extending transmission path whose phase shift and / or attenuation / amplification can be adjusted. Work machine according to claim 2, characterized in that the second transmission path arranged on a periodically moving element of the noise source frequency sensor ( 20 ) and one based on one of the frequency sensor ( 20 ) detected frequency of the element tunable first frequency generator ( 24 . 26a . 26b ). Work machine according to claim 3, characterized in that the second transmission path further comprises at least one second tunable frequency generator ( 24 . 26a ; 24 ), which is based on a harmonic of the tuning frequency of the first frequency generator ( 24 . 26a . 26b ) is tuned. Work machine according to claim 3 or 4, characterized in that the noise source ( 10 ) comprises an agricultural crop processing oscillating or rotating element and that the frequency sensor ( 20 ) is arranged to detect the movement frequency of this element. Working machine according to claim 5, characterized in that the rotating element is occupied by an integer number n of tools and the tuning frequency of the first frequency generator ( 24 . 26a . 26b ) is n times the rotational frequency of the rotating element. Work machine according to claim 6, characterized that the rotating element is a chopper drum and the tools are knives of the chopper drum. Work machine according to claim 6 or 7, characterized in that the tuning frequency to a cavity mode of the driver's cab ( 18 ) is tunable. Work machine according to claim 8, characterized in that the cavity mode is the basic mode of the driver's cab ( 18 ). Work machine according to one of the preceding claims, characterized by a microphone ( 36 ) for recording the noise level in the cabin ( 18 ) and a control circuit ( 32a . 32b . 32c ) for adapting phase shift and / or attenuation / gain of the second transmission path based on the recorded noise level. Work machine according to one of the preceding claims, characterized in that an oscillatable wall surface ( 40 ) of the driver's cab ( 18 ) to one at the oscillation frequency of the wall surface ( 40 ) excitable resonator ( 43 ) is coupled. Work machine according to claim 11, characterized in that the resonator ( 43 ) stronger than the wall surface ( 40 ) is muffled. Work machine according to claim 11 or 12, characterized in that the oscillatory wall surface a window pane ( 40 ) and the resonator on the disc ( 40 ) mounted windshield wiper ( 43 ).