DE102007008567A1 - Servo unit has piezoelectric actuator and amplifier hub arrangement, where diaphragm partially limits pressure chamber, and is subjected to control pressure on far rear side of pressure chamber - Google Patents

Abstract

The servo unit (1) has a piezoelectric actuator (6) and a amplifier hub arrangement (10). A pressure chamber (22) has a piston element (18) combined with larger active surface (A1) and flexible and ductile wall arrangement. A transmission element is provided with comparatively smaller active surface (A2). A diaphragm (58) partially limits the pressure chamber, and is subjected to control pressure on the far rear side of the pressure chamber. An independent claim is also included for a hydraulic valve that has a servo unit.

Description

The The invention relates to a control device provided with a piezoelectric actuator according to the preamble of claim 1.

such Actuators with piezo actuator and hydraulic lift amplification are used when controlling a valve with high precision and speed is required.

According to the DE 37 14 337 C2 Be trained with piezo actuator actuators used to operate servo valves. In this known solution, the comparatively small stroke of a piezoelectric actuator is hydraulically amplified. In this case, the adjusting movement of the piezoelectric actuator is transferred to a piston element with a comparatively large effective area which, together with a piston of smaller effective area, delimits a pressure chamber. Upon displacement of the piston element with a larger effective area of the stroke of the piston is reinforced with a smaller effective area corresponding to the area ratio and transferred directly or indirectly to a control piston of a valve on the example, a pressure medium connection between a pressure port or a tank port and at least one working port or steered is. To compensate for a leakage of the pressure chamber limited by the two piston elements, a leakage compensation device is provided in the known solution.

The GB 2 193 386 A discloses an actuating device in which the pressure chamber bounded by the piston element with a larger effective area and by the piston with a smaller effective area is sealed to the outside via a bellows. This bellows is on the one hand fixed to the housing and on the other hand fixed to the actuated by piezoelectric actuator piston element with a larger effective area, so that its axial movement is made possible to increase or decrease the pressure chamber. Through this bellows, the guidance and the sealing of the piston element with a larger effective area compared to the solution mentioned above is greatly simplified.

Especially For valves that are to be operated with high dynamics - for example Injectors of internal combustion engines - is due the small stroke of the piezoelectric actuator a very large hydraulic Path reinforcement required, due to the required Dynamism is necessary, the control piston of the valve against a comparatively to move stiff return spring. This must be done by the piezo actuator a great force will be applied and accordingly one Control electronics provided with high power become. These requirements can be found in the conventional Solutions only by a comparatively complicated control electronics and a hydraulic lifting amplifier with large Area difference meet, causing the space and the price of the actuator are significantly affected.

the opposite the invention is the object of a to create a simple set-up device that controls a of valves with high dynamics allows.

These The object is achieved by an adjusting device having the features of the patent claim 1 solved.

According to the invention the adjusting device with a piezoelectric actuator running over a Hubverstärkungsanordnung with large and small Effective surface acts directly or indirectly on a control piston. One of the two active surfaces limited common pressure chamber has a wall portion formed by a membrane or the like is, facing away from the pressure chamber rear of a Control pressure is acted upon, so that due to deformation the diaphragm of the pressure chamber in addition to the volume change due the stroke of the piezoelectric actuator reduced or enlarged can be. According to this additional, by the Membrane-induced volume change can increase the lift be enlarged so that, for example, the Area difference of the aforementioned effective areas Lower can be performed to the same stroke gain as to get in conventional systems.

at a preferred embodiment of the invention the pressure chamber in sections by an elastically deformable wall assembly limited, preferably formed by two bellows sections one of which is on one side on the piston element with larger Effective area and the other one-sided on the control piston or the acting on this transmission element with a smaller effective area is fixed. That is, the bellows sections seal the two with larger and smaller effective area executed elements of the Hubverstärkeranordnung and the resulting limited pressure chamber to the outside.

at a particularly advantageous solution extends the Membrane approximately in the radial direction between the larger and the smaller effective area associated bellows sections.

at a particularly simple construction embodiment the control piston is designed with a control edge, over the the back of the diaphragm with the control pressure or a tank pressure can be acted upon.

For example, one of the back Side of the membrane limited rear space via a control channel with the control piston receiving valve bore of the valve be connected, said control channel is connected by adjusting two control edges with a pressure port or a tank port of the valve.

to Minimization of the pressure chamber volume (dead volume) can with larger Active surface executed piston element as a stepped piston be executed, whose section of smaller diameter in the limited of the smaller effective area part of the pressure chamber dips.

at In a preferred embodiment, the control piston is over a comparatively stiff return spring in the direction biased to a basic position.

to Detecting the actual stroke of the control piston, this can be a transducer be assigned, whose signal can be processed by a control electronics is.

at The design of the system is preferably made to ensure that the stiffness and the displacement of the membrane, the stiffness of the return spring, the characteristics of the above control edges of the control piston and the pressure in the pressure chamber are coordinated so that at a phase shift from about 135 ° (stroke piezoelectric actuator and stroke control piston) a gain of the system <1 is. These interpretations can cause instabilities be minimized at high dynamics of the system.

other advantageous developments of the invention are the subject of further Dependent claims.

in the Below is a preferred embodiment of Invention explained in more detail with reference to schematic drawings. Show it:

1 a diagram of a hydraulic valve with a controller and a control device with piezoelectric actuator and Hubverstärkung and

2 a block diagram of the control loop of a system according to 1 ,

1 shows in a simplified form a hydraulic valve 4 with an adjusting device 1 and a regulator 2 for controlling the stroke of a control piston 10 of the valve 4 , For example, a servo valve.

At the adjusting device 1 it is in principle a piezoelectric actuator 6 , whose stroke by a hydraulic - or better said - hydrostatic Hubverstärkeranordnung 8th is amplified and on the control piston 10 of the valve 4 acts. It should be expressly mentioned that the adjusting device 1 not only for the adjustment of control pistons 10 can be used, in principle, with such a control device, the bias of a force acting on a valve element biasing means or the like can be adjusted.

In the example in 1 The solution shown is the piezoelectric actuator 6 in a control room 12 a one-piece or multi-part valve housing 14 added. The control room 12 is frontally through a lid 16 sealed and connected via a unspecified tank line with a tank T, so that corre sponding in the control room 12 Tank pressure is applied. The piezo actuator 6 consists of a plurality of axially successively arranged piezoelectric disks of piezoelectric materials, which deform by applying an electrical voltage, in particular in the axial direction and thus perform a stroke. Depending on the polarity can be a shortening or an extension of the axial length of the piezoelectric actuator 6 be effected.

The basic principle of such piezoelectric elements is known and, for example, in the DE 37 14 337 C2 described, so that in this regard further Aufberungen are dispensable.

The excitation of such piezoelectric actuators 6 generated, acting in the axial direction force acts in the inventive solution on a cup-shaped piston element 18 whose front side 20 has a comparatively large effective area A1. The piston element 18 dives into a pressure room 22 one by a radial extension of the spool 10 leading valve bore 24 is formed. On a piston shirt 26 of the piston element 18 is an end of a bellows section 28 attached, the other end of the valve housing 14 is fixed. Through this bellows section 28 the pressure chamber is in the radial direction towards the control room 12 sealed. At the in 1 illustrated embodiment has the piston element 18 the Hubverstärkeranordnung 8th a slightly butted, radially recessed piston projection 30 which enters a radially recessed portion of the valve bore 24 dips. In this area is the piston bore 24 to an annulus 32 extended, which is connected via a likewise unspecified tank line with the tank T. The sealing of this annulus 32 opposite the pressure chamber 22 takes place via a further bellows section 34 , on the one hand, on a shoulder of the valve housing 32 and on the other hand on a frontal waistband 36 of the control piston 10 or attached to this acting transfer member. The frontal area of the Stirnbundes 36 is designed with an active surface A2, which is substantially smaller than the effective area A1 of the piston element 18 is. The piston projection 30 dive into these, from the bellows section 34 limited area of the pressure chamber 22 one. Through the piston protrusion 30 is the pressure medium volume in the pressure chamber 22 reduced, so that the dynamics is improved accordingly.

At the in 1 illustrated embodiment can via the valve 4 a connection of two working ports A, B with a pressure port P and / or a tank port T are set. In this case, the connection between the working ports A, B and said ports P and T is shut off in the illustrated basic position. When moving the control piston 10 from this basic position to the right (view after 1 ) is via a control edge 38 a connection between the working port A and the tank T and a control edge 42 opened a connection between the working port B and a pressure port P. At an axial displacement of the control piston 10 to the left is via a control edge 40 a connection from the working port A to the pressure port P and via a control edge 44 opened a connection from the working port B to the tank port T. The construction of such valves is well known, so that can be dispensed with a detailed description of the control edges forming piston collars and the associated annular spaces and channels.

At the in 1 illustrated embodiment is the control piston 10 via a return spring arrangement 46 in his in 1 pretensioned basic position. The stroke of the control piston 10 can be via a transducer 48 be recorded.

A special feature of the invention is that the control piston 10 or a corresponding component two control edges 50 . 52 are formed, via the one in the valve housing 14 trained control channel 54 with the pressure port P or the tank T is connectable. In the illustrated embodiment, the control edges 50 . 52 at a tax office 56 of the control piston 10 formed in the illustrated basic position, the connection of the tank T and the pressure port P to the control channel 54 is locked. The from the control piston 10 remote end portion of the control channel 54 flows into a back room 60 , which has an annular, the piston projection 30 encompassing membrane 58 from the pressure room 22 is separated. This membrane 58 extends in the radial direction approximately from that of the first bellows portion 28 limited area towards the bellows section 34 limited area and is pressure-tight on the peripheral walls of the valve body 14 established.

At an axial displacement of the control piston 10 to the right (view after 1 ) is over the control edge 50 the pressure medium connection between the pressure port P and the control channel 54 aufsteueuert, so that ensprechend in the back room 60 the high system pressure is applied to the membrane 58 bulges out to the left, leaving the volume of the pressure chamber 22 depending on the pressure in the pressure chamber 22 and the stiffness of the membrane 58 is reduced. When the control spool is moved to the left, the control edge is moved 52 a pressure medium connection between the tank T and the control channel 54 turned on, so in the back room 60 a very low pressure is applied and the membrane is arched out of the position shown to the right and corresponding to the volume of the pressure chamber 22 opposite the illustrated bulge of the membrane 58 is enlarged. That is, depending on the pressurization of the membrane 58 can the volume of the pressure chamber 22 additionally enlarged or reduced.

Upon excitation of the piezo actuator 6 this is for example enlarged in the axial direction, so that the resulting stroke on the piston element 18 is transmitted and this in the direction of a reduction of the pressure chamber 22 emotional. That about the piston element 18 displaced pressure medium volume causes an axial displacement of the control piston 10 , wherein the stroke is amplified in accordance with the area ratio A1 / A2.

The resulting axial displacement of the control piston 10 takes place against the force of the return spring arrangement 46 , wherein after passing over the cover over the control edge 50 the pressure medium connection between the control channel 54 and the pressure port P is turned on, so that in the rear space 60 the system pressure is applied and the membrane 58 is bulged to the left and displaced accordingly further volume, whereby an additional Hubverstärkung takes place. About the control edges 50 . 52 thus can the pressure in the backspace 60 be modulated and a Hubverstärkung on the control piston 10 be effected. The stroke of the control piston 10 dependent reinforcement across the membrane 58 thus represents a positive feedback.

The result of the excitation of the piezo-processor 6 caused stroke is via the transducer 48 detected and compared as an actual value (-x) with a desired value (w), which is predetermined for example via a joystick or the like. From the present control deviation (w - x) is then via the controller 2 a new actuating signal for controlling the piezoelectric actuator 6 generated.

In 2 the block diagram of such a control loop is shown.

The from the piezoelectric actuator 6 applied force F _{Pi ezo} counteracts that described in more detail below, on the front _page 20 acting compressive force -F in the pressure chamber 22 on the piston element 18 , so that it is acted upon by a resultant force .DELTA.F. The piston element 18 leads according to the characteristic assigned to it 62 a hub 18 through, being dependent on the over the characteristic 64 reproduced constant frontal surface the volume of the pressure chamber 22 is reduced. The resulting volume change ΔV (sum of the pressure chamber 22 taken volume and the volume displaced therefrom causes a by the characteristic 66 reproduced pressure change in the pressure chamber 22 depending on the stroke of the piston element 18 and the control piston 10 , This pressure in the pressure room 22 acts according to the marked feedback on the front page 20 of the piston element with the area A1 (characteristic 64 ), so that the resultant force -F acts against the force F _piezo .

gemäß der Kennlinie 74 einstellt. Der Steuerkolben 10 führt somit einen Hub y gegen die als konstant angenommene Federkraft der Rückstellanordnung 46 durch. Die zum Verfahren des Steuerkolbens 10 erforderliche Kraft wirkt entgegen der vom Piezoaktor 6 auf den Steuerkolben 10 übertragenen Kraft.The due to the volume change in the pressure chamber 22 applied pressure acts according to the characteristic 68 on the end face A2 of the control piston 10 , so that it is acted upon by a force which, contrary to the first approximate constant force -F _R (characteristic 67 ) of the return spring arrangement 46 acts. The resulting force acts on the through the characteristic 70 reproduced constant mass of the control piston 10 , so that it is accelerated with the acceleration ÿ (characteristic 72 ), and get a speed

according to the characteristic 74 established. The control piston 10 thus results in a lift y against the assumed as a constant spring force of the return assembly 46 by. The procedure for the control piston 10 required force counteracts that of the piezoelectric actuator 6 on the control piston 10 transmitted force.

Due to the stroke of the control piston 10 will be according to the characteristics 76 the control edges 50 respectively. 52 the pressure medium connection of the control channel 54 to the pressure port P and the tank port T turned on. Corresponding to the constant membrane surface (represented by the characteristic curve 76 ) and the characteristics of the control edges 50 . 52 and so on the membrane 58 acting pressure in the back room 60 leads the membrane 58 one by the characteristic 80 reproduced stroke, so that additional pressure medium in the pressure chamber 22 is displaced. The resulting volume change .DELTA.V thus results from the sum of the over the piston element 18 and over the membrane 58 displaced volume minus the due to the stroke of the control piston 10 taken volume.

The aforementioned characteristics, in particular the rigidity and the displacement volume of the membrane 58 , the spring rate of the return spring arrangement 46 , the characteristics of the control edges 50 . 52 as well as the system pressure at the pressure port P are coordinated so that the gain of the system at a phase shift of about 135 ° <1, so that instabilities of the system are avoided.

As mentioned above, the inventive Actuating device with a piezoelectric actuator, a hydrostatic Hubverstärkung and additional stroke reinforcement by means of membrane also for the operation of other stroke-dependent Actuators are used.

Disclosed is an actuator with a on a hydraulic Hubverstärkeranordnung acting piezoelectric actuator, wherein a larger effective area of Hubverstärkeranordnung together with a smaller effective area a control piston or a transmission element a Pressure chamber limited, so that an adjusting movement of the piezoelectric actuator transferable to the control piston or the transmission element is. According to the invention, the pressure chamber is in sections bounded by a membrane whose rear side facing away from the pressure chamber can be acted upon by a control pressure.

1

setting device

2

regulator

4

Valve

6

piezo actuator

8th

Hubverstärkeranordnung

10

spool

12

control room

14

valve housing

16

cover

18

piston element

20

front

22

pressure chamber

24

valve bore

26

skirt

28

bellows

30

piston projection

32

annulus

34

bellows

36

end union

38

control edge

40

control edge

42

control edge

44

control edge

46

Return spring arrangement

48

transducer

50

control edge

52

control edge

54

control channel

56

control collar

58

membrane

60

backcourt

62

curve (Stroke)

64

curve (Area A1)

66

curve (.DELTA.V)

68

curve (Area A2)

69

curve (Return spring)

70

Characteristic (mass 10 )

72

curve (Acceleration)

74

curve (Speed)

76

curve (Membrane area)

78

Characteristic (control edge 50 . 52 )

80

curve (Cone excursion)

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

• - DE 3714337 C2 [0003, 0024]
• - GB 2193386 A [0004]

Claims (10)

Actuation device with a piezoelectric actuator ( 6 ), and a Hubverstärkeranordnung whose piston element ( 18 ) with a larger effective area (A1) together with a - preferably elastically deformable - wall arrangement ( 28 . 34 ) and a control piston ( 10 ) or a transmission element with a comparatively smaller effective area (A2) a pressure chamber ( 22 ), so that an actuating movement of the piezoelectric actuator ( 6 ) via the Hubverstärkeranordnung on the control piston ( 10 ) or the transmission element acts, characterized by a pressure chamber ( 22 ) sectionally limiting membrane ( 58 ), whose from the pressure chamber ( 22 ) facing away from the rear side of a control pressure can be acted upon. Setting device according to claim 1, wherein a wall region of the pressure chamber ( 22 ) by two bellows sections ( 28 . 34 ) or the like, one of which on the piston element ( 18 ) with larger effective area (A1) on one side and the other one-sided on the control piston ( 10 ) or the transmission element is fixed. Adjusting device according to claim 2, wherein the membrane ( 58 ) approximately in the radial direction between the two bellows sections ( 28 . 34 ). Adjusting device according to one of the preceding claims, wherein the control piston ( 10 ) or the transmission element control edges ( 50 . 52 ), over which the back of the membrane ( 58 ) can be acted upon by the control pressure. Adjusting device according to claim 4, wherein one of the back of the membrane ( 58 ) limited back space ( 60 ) via a control channel ( 54 ) with a control piston ( 10 ) receiving valve bore ( 24 ), the back space ( 60 ) by adjusting the control edges ( 50 . 52 ) is connectable to a pressure port (P) or a tank port (T). Actuating device according to one of the preceding claims, wherein the piston element ( 18 ) with a larger effective area (A2) is designed as a stepped piston. Adjusting device according to one of the preceding claims, wherein the control piston ( 10 ) via a return spring arrangement ( 46 ) in the direction of the piston element ( 18 ) is biased. Actuating device according to one of the preceding claims, having a position transducer ( 48 ) for detecting the stroke (y). Actuating device according to one of the claims 1, 4 and 7, wherein the stiffness and the displacement volume of the membrane ( 58 ), the spring rate of the return spring arrangement ( 46 ), the characteristics of the control edges ( 50 . 52 ) as well as the system pressure in the pressure chamber ( 22 ) are matched to one another such that in the case of a phase shift between the stroke of the piezoelectric actuator ( 6 ) and the stroke (y) of the control piston ( 10 ) of about 135 ° is a gain of the system ≤ 1. Hydraulic valve with an adjusting device according to one of claims 1 to 9.