DE102010039165A1 - Positioning device for use in combustion engine of vehicle, has piezoelectric actuator placing position element in one direction and another piezoelectric actuator placing position element in another direction - Google Patents

Abstract

The device has a position element (2) i.e. needle, movably arranged between directions (A), where the directions are opposite to each other. A piezoelectric actuator (3) places the position element in one direction and another piezoelectric actuator places the position element in another direction. A control unit (5) comprises a computing device (6) that is laid out to compute an exact position of the position element based on each deactivated detected signals of the former piezoelectric actuator. The two piezoelectric actuators are directly in contact with the position element. An independent claim is also included for a method for regulating a regulating device with a position element.

Description

State of the art

The present invention relates to an adjusting device.

Adjusting devices for fluid injection are known from the prior art in various configurations with needle-shaped adjusting elements, which are actuated by means of a ceramic piezoelectric actuator to realize faster fluid injections. In this case, it is of particular disadvantage that due to the property degradation of the piezoelectric actuators as a function of the number of electrical cycles no direct correlation between the applied voltage and the expansion of the piezoelectric actuator is possible. Thus, the actual position of the actuator can not be determined exactly at each time of the injection process. Furthermore, each individual piezoelectric actuator in the production has to be measured and coded in a time-consuming and cost-intensive manner in order to determine the individual lifting capacity for a fluid metering.

Disclosure of the invention

The adjusting device according to the invention with the features of claim 1 has the advantage that in this case two serially arranged piezoelectric actuators are used, which allow precise positioning of the actuating element at any time of the injection process and thus a more precise dosage of the injected fluid. This is inventively achieved in that the adjusting device comprises an actuating element, which is arranged to be movable in a first direction and a second direction, wherein the first and second directions are opposite to each other. Furthermore, the adjusting device comprises a first piezoelectric actuator and a second piezoelectric actuator, the first piezoelectric actuator setting the adjusting element in the first direction, and the second piezoelectric actuator setting the adjusting element in the second direction. The production steps for the measurement and coding of the piezoelectric actuators can thus be omitted, which leads to a considerable cost savings and significantly shorter production times.

The dependent claims show preferred developments of the invention.

According to a preferred embodiment of the invention, the first piezoelectric actuator sets the actuating element from a starting position to a setting position in the first direction and the second piezoelectric actuator returns the actuating element from the setting position to the starting position in the second direction. As a result, a reliable opening or closing of the actuator is achieved with high dynamics.

Further preferably, the adjusting device comprises a control unit, which is connected to the first and second piezoelectric actuator. The control unit is designed to alternately activate and / or control the first and second piezoelectric actuators and also to detect the signals of the deactivated or non-actuated piezoactuator. The deactivated piezoelectric actuator is used here as a sensor and detects the force exerted by the activated piezoelectric actuator on it as a signal that can be used to position the positioner. From this information is the exact strain of the first piezoelectric actuator and thus determine the stroke of the control element. A complex measurement for the selection of the piezoelectric actuators to be used in production can therefore be omitted.

In a further advantageous embodiment of the invention, the control unit comprises a computing device which is designed to calculate an exact position of the actuating element based on the detected signals of the respectively deactivated piezoelectric actuator. Due to the calculated positioning of the piezoelectric actuator at any time during the injection process, the fluid metering can be done much more accurately than via the conventional coding of the piezoelectric actuator. By eliminating the hitherto necessary, complex feedforward correction functions in the control unit for correcting the injected fluid quantity, the structure and the design of the control unit can also be substantially simplified. Furthermore, by tuning with the detected, actually injected fluid quantity and the setpoint defined by the control unit tuning, z. B. by an intermediary of another control unit, which changes the target amount, are made much more difficult.

Preferably, the first piezoelectric actuator and / or the second piezoelectric actuator contacted directly the actuator. Due to the direct actuation of the actuator components can be omitted, which minimizes the number of components and has a significant cost savings.

In a further advantageous embodiment of the invention, the second piezoelectric actuator on a passage opening for performing the actuating element. As a result, a low-wear, reliable management of the control element is ensured. By a corresponding adaptation of the internal electrode design of the second piezoelectric actuator electrical flashovers are avoided at the passage opening to the actuator.

Further preferably, the actuator is a needle having at one end a flat foot region which is arranged between the first and second piezoelectric actuator. As a result, mechanical errors, such. B. jamming of the Stellelements, or wear, such. B. by coking of the control element and / or adjacent components, due to the simple structure of the actuator are easily diagnosed.

Preferably, the adjusting device comprises a spring element for supporting a provision of at least one of the piezoelectric actuators. As a result, a faster closing of the actuating element, which is pressed with increased return speed and greater restoring force in a valve seat, reachable, whereby, for example, when used in a vehicle, a significantly reduced amount of fluid must be injected into the combustion chamber. This leads to improved idling behavior and emission behavior of the engine.

Furthermore, the invention relates to a method for setting an adjusting device with an actuating element, a first piezoelectric actuator and a second piezoelectric actuator. In this case, in a first method step, the first piezoelectric actuator is activated in a first direction in order to set the adjusting element from a starting position into a setting position. In this case, the second deactivated piezoactuator operates as a sensor, which receives the forces acting on it from the actuator and transmitted to the control unit. In a second method step, the first piezoelectric actuator is deactivated and the second piezoelectric actuator is activated in a second direction in order to reset the adjusting element from the setting position to the starting position. In this case, the first piezoelectric actuator acts as a sensor and absorbs the forces acting on the second piezoelectric actuator and transmits them to the control unit. The control unit calculates an exact position of the control element based on the transmitted signals. Due to the simple control sequence, a reliable and cost-effective control of the control element can be realized. With the method according to the invention, a quantity of fluid can be determined much more accurately than via the conventional piezoactuator selection in production, which results in a significant increase in the efficiency of internal combustion engines in which the adjusting device is used. Furthermore, a more cost-effective production of the adjusting device with a small number of manufacturing steps and shorter cycle times can be achieved. Alternatively, the actuating element according to the invention can also be actuated indirectly via a servo valve with a reversal of motion, whereby an employment in a wide range of internal combustion engines is possible.

According to a preferred embodiment of the method, an opening duration for a fluid injection, in particular a fuel injection or fuel injection, is determined based on the calculated position of the actuating element. As a result, even with injection processes with very high frequency or very short cycle times, a precise metering of the fluid can take place in all load ranges of the internal combustion engine.

drawing

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing is:

1 4 is a partial sectional view of a control device according to a first preferred embodiment of the invention,

2 a further sectional partial view of the adjusting device of 1 .

3 a cross-sectional view of a first piezoelectric actuator of the first embodiment,

4 a cross-sectional view of a second piezoelectric actuator of the first embodiment, and

5 a sectional partial view of the adjusting device according to a second preferred embodiment of the invention.

Embodiments of the invention

The following is with reference to 1 to 4 an adjusting device according to a first preferred embodiment of the invention described in detail.

1 shows a sectional partial view of an actuating device 1 according to the first embodiment of the invention. The adjusting device 1 includes an actuator 2 , a first piezoelectric actuator 3 and a second piezoelectric actuator 4 , which are preferably formed as a ceramic multilayer piezoelectric actuators and in a housing 9 are arranged, which a fluid via a fuel line 10 is supplied. Furthermore, the adjusting device comprises 1 one outside the case 9 arranged control unit 5 with a computing unit provided therein 6 , which with the first piezoelectric actuator 3 and the second piezoelectric actuator 4 electrically connected. The first and second piezo actuators 3 . 4 wise, as in 3 and 4 represented, each having a square cross section. Alternatively, the piezo actuators could also have a circular cross-section. The trained as a needle actuator 2 has a flat foot area 7 on that between the first and second piezoelectric actuator 3 . 4 is arranged and at the first and second piezoelectric actuators 3 . 4 directly applied or contacted. One with the foot area 7 connected neck area 12 of the actuating element 2 is, as well as from the cross-sectional view of 4 can be seen by a in the second piezoelectric actuator 4 trained passage opening 12 passed. A the foot area 7 opposite end region 13 of the actuating element 2 is cone-shaped and closes one in the housing 9 opposite arranged valve seat 11 , 1 shows a starting position of the actuating element 2 which is the closed position.

According to the method according to the invention is for opening the actuator 1 the first piezoelectric actuator 3 from the control unit 5 activated or activated in a first direction A shown as arrow. As a result of the electrical current or load, the first piezoelectric actuator expands 3 off and that with the foot area 7 adjoining control element 2 is moved from a home position to a parking position. The at the foot area 7 Opposite fitting and on the housing 9 supported second piezoelectric actuator 4 , which is deactivated or not activated, in this case by the first piezoelectric actuator 3 generated force compressed. It should be noted that the term "deactivated" here in the sense of "at rest or in rest position" is to be understood, in which the electrically not loaded here and for moving the control element 2 unused second piezoelectric actuator 4 is merely compressed and is connected as a sensor, the forces acting on it from the actuator 2 receives. The case detected sensor signals of the second piezoelectric actuator 4 be to the arithmetic unit 6 in the control unit 5 transmitted based on an exact position of the actuator 2 calculated.

As in 2 shown, the end raises 13 of the actuating element 2 due to the expansion of the first piezoelectric actuator 3 in the first direction A from the valve seat 11 in the parking position, so that through the fuel line 10 supplied fluid to the outside of the housing 9 can flow out.

To the actuator 2 back to the valve seat 11 reset or the adjusting device 1 to close, now becomes the second piezoelectric actuator 4 from the control unit 5 activated and the first piezoelectric actuator 3 disabled. Here, the second piezoelectric actuator expands 4 off and moves the actuator 2 from the in 2 shown positioning position in a second direction B shown by an arrow back to the starting position. This will be the first deactivated piezo actuator 3 compressed, which is now connected as a sensor to that of the second piezoelectric actuator 4 To detect applied to him force and as sensor signals to the computing unit 6 in the control unit 5 to transmit based on it again an exact position of the actuator 2 calculated.

Based on the calculated and known positions of the actuator 2 At any time of the injection process, the so-called needle flight behavior, the required amount of fluid can be determined with much higher precision than by the piezoelectric actuator measurement and coding conventionally used in the prior art prior to installation. This results in great fuel savings potential.

Hereinafter, with reference to 5 an adjusting device according to a second preferred embodiment of the invention described in detail. The same or functionally identical components are designated here by the same reference numerals as in the first embodiment.

In contrast to the first embodiment described above, the second embodiment has a spring element 8th in support of a provision of the actuator 2 on. The spring element 8th is between the second piezoelectric actuator 4 and the foot area 7 of the actuating element 2 arranged. Alternatively, the spring element 8th also between the second piezoelectric actuator 4 and the housing 9 be arranged. This allows a faster closing of the actuating element 2 will be realized.

Although not shown in the figures, in all the described embodiments additionally a hydraulic coupler between the first piezoelectric actuator 3 and the housing 9 can be arranged or switched behind to provide a heat-related length compensation

The adjusting device according to the invention 1 has the advantage that by the use and separate control of two serially installed piezo actuators 3 . 4 one of the piezo actuators can always work as a sensor and an exact position of the control element 2 can determine. Thus, a more precise determination of the amount of fluid is achieved in both directly and indirectly actuated piezoelectric actuators. Furthermore, fuel consumption and emission behavior can be further reduced and future prescribed limits can be met or exceeded.

Claims (10)

Actuating device comprising: - an actuating element ( 2 ) arranged movably in a first direction (A) and a second direction (B), the first and second directions (A, B) being opposite to each other, - a first piezoactuator ( 3 ), and - a second piezoelectric actuator ( 4 ), - wherein the first piezoelectric actuator ( 3 ) the actuator ( 2 ) in the first direction (A), and - wherein the second piezoelectric actuator ( 4 ) the actuator ( 2 ) in the second direction (B). Setting device according to claim 1, characterized in that the first piezoelectric actuator ( 3 ) the actuator ( 2 ) from a starting position into a Positioning position in the first direction (A) and the second piezoelectric actuator ( 4 ) that actuator from the setting position to the starting position in the second direction (B) reset. A control device according to claim 1 or 2, further comprising a control unit ( 5 ), which with the first and second piezoelectric actuators ( 3 . 4 ) and is adapted to the first and second piezoelectric actuator ( 3 . 4 ) and which is further designed to detect signals of the respective deactivated piezoelectric actuator. Setting device according to claim 3, characterized in that the control unit ( 5 ) a computing device ( 6 ), which is designed, an exact position of the actuating element ( 2 ) based on the detected signals of the respective disabled piezoelectric actuator to calculate. Adjusting device according to one of the preceding claims, characterized in that the first piezoelectric actuator ( 3 ) the actuator ( 2 ) directly contacted, and / or that the second piezoelectric actuator ( 4 ) the actuator ( 2 ) contacted directly. Adjusting device according to one of the preceding claims, characterized in that the second piezoelectric actuator ( 4 ) a passage opening ( 12 ) for performing the actuating element ( 2 ) having. Adjusting device according to one of the preceding claims, characterized in that the actuating element ( 2 ) is a needle having at one end a flat foot area ( 7 ), which between the first and second piezoelectric actuator ( 3 . 4 ) is arranged. Adjusting device according to one of the preceding claims, further comprising a spring element ( 8th ) in support of a provision of at least one of the piezo actuators ( 3 . 4 ). Method for setting an actuating device with an actuating element ( 2 ), a first piezoelectric actuator ( 3 ) and a second piezoelectric actuator ( 4 ), comprising the steps: - activating the first piezoelectric actuator ( 3 ) in a first direction (A) to the actuator ( 2 ) from a starting position to a setting position, wherein the second piezoelectric actuator ( 4 ) is disabled and works as a sensor and that on the second piezoelectric actuator ( 4 ) acting forces from the actuator ( 2 ) and to the control unit ( 5 ), and - deactivating the first piezoelectric actuator ( 3 ) and activating the second piezo actuator ( 4 ) in a second direction (B) to the actuator ( 2 ) from the setting position to the starting position, wherein the first piezoelectric actuator ( 3 ) works as a sensor and the second piezoelectric actuator ( 4 ) absorbs acting forces and to the control unit ( 5 ), the control unit ( 5 ) based on the transmitted signals an exact position of the actuating element ( 2 ). Method for setting an adjusting device according to claim 9, characterized in that based on the calculated position of the actuating element ( 2 ) an opening duration for a fluid injection, in particular a fuel injection or fuel injection, is determined.

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