Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
  • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
  • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
  • B06B1/20—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of a vibrating fluid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
  • F15B21/12—Fluid oscillators or pulse generators

Definitions

• the invention relates to a device for controlling a hydrostatic drive with a periodically actuated switching valve, which connects a resonance tube connected to the hydrostatic drive to form standing pressure waves of the hydraulic fluid under resonance conditions alternately to a pressure fluid supply line and to a return line.
• the invention is therefore based on the object of designing a device for controlling a hydrostatic drive of the type described at the outset using simple constructional means so that the working pressure for the drive is independent of its working path between the maximum pressure offered via the hydraulic medium supply line and the pressure of the return line can be set, with a high degree of efficiency and good dynamics.
• the invention solves this problem in that the resonance tube has a pressure output in an oscillation node of the standing pressure waves and in that the switching times of the switching valve can be controlled while the switching frequency remains the same.
• the arrangement of the pressure output in an oscillation node of the pressure waves means that the pressure waves of the orders assigned to this node can be suppressed at the pressure output, so that the pulsation of the working pressure at the pressure output is comparatively low despite pulsed activation.
• the resonance tube connected to the control valve forms a main resonator, at the pressure output of which at least one secondary resonator with a resonance tube connects, which in turn has a pressure output in an oscillation node which has standing pressure waves which form in this resonance tube, and that the resonance tube of the main resonator is either connected in parallel with an additional resonance tube or can be connected at both ends to the pressure medium supply line and the return line via switching valves which can be actuated in opposite directions is.
• At least two secondary resonators are provided, these are each to be connected to the pressure output of the preceding resonator and, with the exception of the secondary resonator on the output side, to be formed from a parallel connection of at least two resonance tubes, one of which has the pressure output for connecting the subsequent resonator, and thus also in the region of the secondary resonators, the resonance conditions for the pressure waves forming in their resonance tubes can be met. With each additional secondary resonator, higher order pressure waves can be suppressed, so that the remaining ripple can be adapted to the respective tolerance ranges.
• the mutual spatial arrangement of the resonance tubes connected in parallel plays no role in the operation of this parallel connection.
• the resonance tubes connected in parallel can therefore be arranged in accordance with the respective space available. Particularly simple, space-saving design conditions result in this connection if the resonance tubes connected in parallel enclose one another coaxially.
• the control valve can be assigned a control device for tracking the switching frequency to the possibly changing resonance frequency of the resonator connected directly to the control valve .
• the main resonator can be used for a specific measuring location pressure setpoint determined in a certain position of the switching valve is given, which is compared with the actual pressure determined at this measuring location at the corresponding switching valve position, so that any setpoint / actual value difference that may occur can be corrected by adjusting the switching frequency of the switching valve.
• Another possibility is to monitor the position of an oscillation node of the standing pressure waves. If the switching frequency of the switching valve remains the same, a change in the resonance frequency causes the node to shift, so that pressure fluctuations are detected at the original node, which can be used to adjust to the resonance frequency by controlling the switching frequency of the switching valve.
• the switching valve must ensure the switching frequencies which are comparatively high in order to maintain the resonance frequencies, specifically in the case of pressure pulses with flanks which are as steep as possible.
• the switching valve it is proposed in a further embodiment of the invention to design the switching valve as a rotary piston valve with a rotary piston coaxially surrounding the resonance tube, the rotary piston arranged axially one behind the other in a housing, on the one hand with the hydraulic medium supply line and on the other hand with the return line passes through connected annular chambers and in the area of these annular chambers has control edges forming through-openings which cooperate with through-openings of the resonance tube, the release of which can be controlled for the switching times by a rotatable control sleeve with control edges.
• the speed of rotation of this rotary piston valve determines the switching frequency of the switching valve, so that the switching frequency can be controlled very easily via the rotary drive.
• the rotary piston opens and closes the through openings of the resonance tube alternately in the area of the two housing chambers, the switching times being additionally adjustable by means of the control sleeve, which is rotatably adjustable relative to the resonance tube and which sooner or later releases the through openings in the resonance tube via its control edges. With the help of this control sleeve, the pressure pulse width and thus the desired working pressure can be adjusted in a simple manner.
• the fluid friction results in losses within the resonance tubes, which result in a reduction in efficiency.
• the friction losses which occur as a result of a relative movement between the hydraulic medium and the tubular body can be largely prevented if the tubular body of the resonance tube or the resonance tubes is formed orthotropically with a greater rigidity in the circumferential direction compared to the axial direction.
• the lower axial rigidity of the tubular body allows it to be taken along by the hydraulic medium and thus to reduce the friction losses.
• an immovable fixing of the tube ends must be ensured.
• the tubular body of the resonance tube or the resonance tubes can consist of a corrugated tube.
• plastic pipes in a correspondingly orthotropic manner, although care must be taken to ensure that the dissipation in the pipe body itself remains as small as possible.
• the expansion behavior of the tubular body in the circumferential and longitudinal directions can also be coordinated with one another in such a way that a corresponding change in length of the tubular body arises as a result of a circumferential expansion caused by the liquid pressure and the associated shortening. If the negative longitudinal expansion of the tubular body corresponds to the liquid compression at a given hydraulic medium pressure, there is no ralative movement between the hydraulic medium and the tubular body.
• Fig. 1 shows an inventive device for controlling a hydrostatic
• FIG. 2 is a block diagram of an inventive device with a
• FIG. 3 Main and two secondary resonators, FIG. 3 a device corresponding to FIG. 2 in a construction variant, FIG. 4 a further embodiment of a device according to the invention, FIG. 5 a resonator with orthotropic resonance tubes connected in parallel in a simplified axial section,
• FIG. 6 shows a simplified axial section through a switching valve
• FIG. 7 shows a section along the line Vll-Vll of FIG. 6
• FIG. 8 shows a section along the line Vlll-Vlll of FIG. 6.
• the device for controlling a hydrostatic drive 1, which is indicated as a working cylinder, has a switching valve 2, which is actuated periodically via a suitable drive 3.
• This switching valve 2 connects a resonance tube 4 alternately with a hydraulic medium supply line 5 and a return line 6 to a prestressed hydraulic medium tank.
• the length of the resonance tube 4 corresponds to an integral multiple of the wavelength of the pressure waves of the hydraulic medium which form in the resonance tube 4 and which spread over the length of the resonance tube 4 due to the pressure pulses resulting from the actuation of the switching valve.
• the resonance tube 4 also forms a fixed reflection end for these pressure waves, pressure waves of different orders with resonance nodes arise in the resonance tube 4 under resonance conditions, in which the pressure waves passing through these nodes have no amplitude, so that through a pressure outlet 7 in the area of such a node, the pressure waves assigned to it are suppressed and the working pressure connected to this pressure outlet 7 is subjected to a working pressure which is subject to correspondingly lower fluctuations.
• the working path of the drive 1 connected to the pressure output 7 has no influence on the resonance conditions in the resonance tube 4, which creates simple control conditions because of the switching times of the switching valve which determine the pressure pulse width 2 at a switching frequency matched to the resonance frequency, the effective value of the working pressure at the pressure outlet 7 can be set as desired between a maximum pressure corresponding to the pressure in the hydraulic medium supply line 5 and a minimum pressure corresponding to the pressure in the return line 6.
• the influencing variables on the resonance conditions cannot always be regarded as constant.
• the toughness and the compressibility of the hydraulic medium change with the temperature subject to fluctuations, so that the device must be adapted to the changing resonance conditions if the highest possible efficiency is desired.
• This adaptation can be achieved comparatively simply by tracking the switching frequency of the switching valve 2, as is indicated schematically in FIG. 1.
• the drive 3 for the switching valve 2 is controlled via a control device 8, which monitors a possible displacement of an oscillation node.
• the pressure transducer 9 connected to the resonance tube 4 in the area of the node and a bandpass filter 10 matched to the frequency of the pressure waves passing through the node, the pressure amplitudes of the pressure waves associated with the vibration node associated with the displacement of the node can be detected and to control the switching valve drive 3 in the sense of tracking the switching frequency to the resonance frequency.
• the band filter 10 can be matched to the respective switching frequency of the switching valve, which is illustrated in FIG. 1 by a control line 11 between the switching valve drive 3 and the band filter 10.
• the pressure outlet 7 can be provided in the area of vibration nodes of the higher-order pressure waves, there are generally particularly favorable conditions in the area of a vibration node of the reason for the pressure vibrations, that is to say in the longitudinal center of the resonance tube 4.
• the fundamental wave and suppresses the pressure waves with an odd atomic number at the pressure outlet 7.
• the pressure output 7 of the Resonance tube 4, an additional resonance tube 12 and, if necessary, additional resonance tubes 13 are subsequently connected, in each case to the pressure outlet 7 of the immediately preceding resonance tube.
• the resonance tubes are each formed with half the length of the upstream resonance tube, as shown in FIGS. 2 to 4.
• the pressure harmonics of the orders 2, 6, 10, ... are suppressed at the pressure output 7 of the resonance tube 12 and the pressure harmonics of the orders 4, 12, 20, ... are suppressed at the pressure output 7 of the resonance tube 13, so that the residual fluctuations in the working pressure on Pressure output 7 of the resonance tube 13 turn out to be comparatively small. If necessary, this residual pulsation can be further reduced by adding additional resonance tubes.
• a resonance tube 4a is connected in parallel with the resonance tube 4, so that this parallel connection of the resonance tubes 4 and 4a results in a main resonator A.
• the secondary resonator B connected to the main resonator A consists of a parallel connection of the resonance tubes 12 and 12a. Such a parallel connection for the resonance tube 13 is not necessary for the secondary resonator C on the output side.
• Another possibility of forming a fixed reflection end for the main resonator A, according to FIG. 3, is to provide a switching valve 2a actuated in the opposite direction to the switching valve 2 at the end of the resonance tube 4, so that the resonance tube 4 is connected on one side to the hydraulic medium supply line 5 and is connected at the other end to the return line 6 and vice versa, with the respective resonance frequency.
• the resonance tubes can be formed orthotropically, with a correspondingly lower rigidity being required in the axial direction so that the tube body can be carried along by the hydraulic medium in the axial direction.
• the resonance tubes consist of corrugated tubes, which is illustrated in FIG. 5 for the main resonator A. In such a case, it must of course be ensured that the pipe ends are held so that they cannot move, which is not shown in more detail for reasons of clarity.
• the pressure outlet 7 is formed by a connecting sleeve 14 which is penetrated axially displaceably by the resonance tube 4. Since the connecting sleeve 14 surrounds the resonance tube 4 at a radial distance, the sealing is achieved by ring sleeves 15, which allow the relative displacement between the tube and the sleeve.
• a housing 16 enclosing the resonance tube 4, in which a rotary piston 17 coaxial with the resonance tube 4 is rotatably mounted, which passes through two annular chambers 18 and 19 of the housing 16 arranged axially one behind the other and in the region of both annular chambers 18, 19 has control openings forming passage openings 20 which cooperate with passage openings 21 of the resonance tube 4.
• a rotationally adjustable control sleeve 22 is mounted in the housing 16, which is provided with through openings 23 and control edges 24 formed by these. This control sleeve 22 can be adjusted via a ring gear 25.
• the passage openings 20 in the region of the annular chamber 18 connected to the hydraulic medium supply line 5 reach the region of the passage openings 21 of the resonance tube 4, so that the resonance tube 4 is connected to the hydraulic medium supply line 5 until the control edges of the control sleeve 22 ensure that the passage openings 20 of the rotary piston 17 are closed in the region of the annular chamber 18.
• the through openings 20 of the rotary piston 17 in the area of the annular chamber 19 connected to the return line 6 are opened by the associated control edges 24 until they come out of the area of the through openings 21 of the resonance tube 4, whereby an alternating connection of the resonance tube 4 to the Hydraulic medium supply line 5 and to the return line 6 is ensured.
• the switching times are determined via the rotational position of the control sleeve 22 relative to the resonance tube 4, while the switching frequency for a given number of passage openings distributed over the circumference depends only on the rotational speed of the rotary piston 17.
• the pulse width can therefore be adjusted as desired at a set switching frequency by rotating the control sleeve 22 to control the hydrostatic drive 1, which is reflected in a corresponding change in the working pressure at the pressure outputs 7.
• annular chambers 18 and 19 are advantageous, in which pressure-elastic bodies can be used for this purpose, for example with compressed gas, for. B. nitrogen, filled ring hoses 27, which are indicated by dash-dotted lines in FIG. 6.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Analytical Chemistry (AREA)
• Chemical & Material Sciences (AREA)
• Fluid-Pressure Circuits (AREA)
• Valve Device For Special Equipments (AREA)
• Vehicle Body Suspensions (AREA)
• Hydraulic Clutches, Magnetic Clutches, Fluid Clutches, And Fluid Joints (AREA)
• Reciprocating Pumps (AREA)
• Apparatuses For Generation Of Mechanical Vibrations (AREA)

Applications Claiming Priority (4)

Publications (2)

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Family Applications (1)

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• 1995
  • 1995-02-01 AT AT0016995A patent/AT403219B/de not_active IP Right Cessation
• 1996
  • 1996-01-31 US US08/894,494 patent/US5974800A/en not_active Expired - Fee Related
  • 1996-01-31 CZ CZ972285A patent/CZ283346B6/cs not_active IP Right Cessation
  • 1996-01-31 EP EP96901186A patent/EP0807212B1/fr not_active Expired - Lifetime
  • 1996-01-31 WO PCT/AT1996/000015 patent/WO1996023980A2/fr not_active Ceased
  • 1996-01-31 DE DE59606770T patent/DE59606770D1/de not_active Expired - Lifetime
  • 1996-01-31 AT AT96901186T patent/ATE200559T1/de not_active IP Right Cessation

Non-Patent Citations (1)

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