KR102027076B1 - A detection method for detecting a gap size of a gap between the injector valve assembly and the piezoelectric stack, and a starting method for starting the actuator unit of the piezoelectric stack. - Google Patents

Abstract

The present invention relates to a detection method for detecting a gap size 34 of a gap 32 between an injector valve assembly 12 of an internal combustion engine and a piezoelectric stack 14 designed to activate an injector valve assembly 12. The period Δt required for the friction engagement between the injector valve assembly 12 and the piezoelectric stack 14 to occur is then determined, and then the gap size 34 of the gap 32 is determined from this period Δt. . Moreover, this invention relates to the starting method for starting the actuator unit 22 of the piezoelectric stack 14 in which the said detection method is performed.

Description

A detection method for detecting a gap size of a gap between the injector valve assembly and the piezoelectric stack, and a starting method for starting the actuator unit of the piezoelectric stack.

The present invention relates to a detection method for detecting a gap size of a gap between an injector valve assembly and a piezoelectric stack provided to activate an injector valve assembly. The invention also relates to a starting method for starting an actuator unit of a piezoelectric stack used to activate an injector valve assembly.

The actuator unit of the piezoelectric stack used to activate the injector valve assembly of the internal combustion engine typically comprises a component having a plurality of electrode layers and a plurality of material layers that are configured as a stack and also respond to electric field application. In this case, each material layer is disposed between two electrode layers. When an electric field is applied to the actuator unit through the electrode layer, the layer of material expands and the actuator unit extends along the longitudinal axis of the actuator unit as a whole. This deflection may then be transferred to another component, for example an injector valve assembly of the internal combustion engine, to raise the injector needle away from the needle seat to inject fuel into the combustion chamber of the internal combustion engine.

Opening and closing of the injector needle of the injector valve assembly is accomplished by directly or indirectly conveying the longitudinal expansion of the actuator unit to the injector valve assembly, wherein the longitudinal expansion is any point between the injector valve assembly and the piezoelectric stack with the actuator unit. It is delivered by a force fit that occurs at.

DE 10 2013 206 933 A1 discloses an embodiment in which the piezoelectric stack is modularized so that the piezoelectric stack has not only the actuator unit described above but also a sensor unit coupled to the actuator unit by pressure fitting. In this case, the sensor unit has at least one ceramic material layer with two electrode layers in each case. As a result, the change in the force transmitted to the piezoelectric stack due to the opening and closing of the injector needle can be detected, so that the opening and closing time of the injector needle can be detected.

In the installed state, the piezoelectric stack and the injector valve assembly fill the gap between the piezoelectric stack and the injector valve assembly, which varies with the life of the two elements, for example, due to deterioration of the actuator unit or wear or wear on the two elements. Have

As the demand for emissions and consumption increases, the demand for fuel injection into the combustion chamber increases due to the high pressure, high temperature, and multiple injections that require higher accuracy for metering the injected fuel. To achieve the required accuracy, it is not enough to drive the injector in the operating mode, and closed loop control is necessary. In particular, it is also important to be able to compensate for the gap between the injector valve assembly and the piezoelectric stack in such closed loop control, which must know the gap size, in particular the gap size that varies with life.

Accordingly, it is an object of the present invention to present a detection method for detecting such gap size.

This object is achieved with a detection method having the features of claim 1.

A further object is to present a maneuvering method for manipulating an actuator unit that can be used to compensate for the gap size.

The starting method for starting the actuator unit of the piezoelectric stack is the subject of the equivalent claims.

Advantageous refinements of the invention are the subject of the dependent claims.

The detection method for detecting the gap size of the gap between the injector valve assembly of the internal combustion engine and the piezoelectric stack for activating the injector valve assembly,

Providing a piezoelectric stack having an actuator unit and a sensor unit coupled to each other by a pressure fit, the sensor unit being configured to detect a force gradient applied to the actuator unit;

Providing an injector valve assembly that is activated during operation by an actuator unit, the injector valve assembly and the piezoelectric stack being disposed at a distance from each other over a gap having an unknown gap size;

Detecting a voltage signal of the sensor unit;

Applying a defined voltage pulse to the actuator unit to cause the actuator unit to deflect along the actuator unit longitudinal axis while reducing the gap;

Detecting a period during which the voltage pulse is applied to the actuator unit starting from the first time at which the voltage pulse starts to be applied and up to a second time when a voltage gradient occurs in the detected voltage signal of the sensor unit; And

Identifying the gap size of the gap from the detected period and the defined voltage pulse.

The detection method includes utilizing the insight that a force shock occurs in the piezoelectric stack due to the pressure fit between the piezoelectric stack and the injector valve assembly. Since the force shock coincides with, for example, the force gradient generating electric charges, the voltage can be grasped from the outside. The pressure fit and hence the force gradient occurs at the moment the gap between the piezoelectric stack and the injector valve assembly is overcome. Since the voltage applied to the actuator unit for expansion is known, the gap size of the gap can be inferred over the measurement period until the sensor unit detects a pressure fit with the injector valve assembly.

To this end, a group of previously identified characteristic curves is advantageously stored, which sets the gap size of the gap for a predefined voltage pulse based on the period for which the voltage pulse is applied.

In order to be able to compensate for the gap size of a subsequent gap by, for example, closed loop control, it is necessary to identify the measurement variable defined from the system to calculate the controlled variable applicable from the system. In this case, the modular design of the piezoelectric stack comprising the actuator unit and the sensor unit is advantageously used to confirm the gap size. Thus, since existing sensor units are already in use, there is no need to provide additional sensors for checking the gap size. In this case, the sensor unit detects a force rise at a second time the piezoelectric stack achieves a pressure fit with the injector valve assembly.

Preferably, the gap size of the gap between the piezoelectric stack and the injector valve assembly is detected for every activation cycle of the injector valve assembly. Thus, for example, it is possible to capture additional data regarding the effects of aging on the elements or the effects of abrasion on the elements, such as decay or wear of the actuator unit, which is reflected in the gap size, which changes over time, for example. have.

In the above improvement, a positive voltage gradient is detected in the voltage signal of the sensor unit at the second time. Accordingly, if the signal of the sensor unit indicating the voltage gradient is positive, it can be immediately identified that the second time exists.

Preferably, a second voltage gradient is detected in the voltage signal of the sensor unit at a third time that the injector needle of the injector valve assembly rises away from the needle seat. As a result, the injector can be opened to advantageously detect the exact time of injecting the fuel to be detected.

Specifically, in this case a negative voltage gradient is detected in the voltage signal of the sensor unit. Accordingly, arithmetic symbols can be used to detect whether the force gradient of the piezoelectric stack is caused by a pressure fit generated between the piezoelectric stack and the injector valve assembly or by the injector needle raised from the needle seat.

In particular, in the case of an injector unit using direct transfer of longitudinal expansion from the actuator unit to the injector valve assembly, the third voltage in the voltage signal of the sensor unit at the fourth time the injector needle is in contact with the needle seat by a pressure fit. A gradient is detected and the fourth time and the second time surround the third time. In this case, a negative voltage gradient is advantageously detected at the fourth time. Closure of the injector and thus termination of fuel injection also results in a force gradient of the piezoelectric stack that can be detected by the sensor unit using the voltage gradient. Thus, it is now possible to accurately detect when the sensor unit to be used has a pressure fit of the injector valve assembly, when the injector needle is opened, and when the injector needle is closed again. Thus, the fuel injected into each combustion chamber can be accurately metered. In addition, from the measured data, a closed loop control can be provided that can compensate for the effects of aging so that fuel can be continuously and accurately injected into each combustion chamber.

The starting method for starting the actuator unit of the piezoelectric stack for activating the injector valve assembly of the internal combustion engine includes a predetermined open voltage applied to the actuator unit such that the actuator unit raises the injector needle of the injector valve assembly away from the needle seat. It includes having a pulse. Open voltage pulse,

Performing the above-described detection method to detect a gap size of a gap between the piezoelectric stack and the injector valve assembly; And

A preliminary voltage pulse is applied to the actuator unit after the step of closing the gap between the actuator unit and the injector valve assembly.

As the gap size is now known, it is possible to compensate for the gap by readjusting the actuator unit by a preliminary voltage pulse applied to the actuator unit, so that the actuator unit deflects and overcomes the gap.

To this end, it is advantageous to store an additional group of characteristic curves in which the magnitude of the preliminary voltage pulse required to close the gap can be read.

Thus, the actuator unit can be operated based on a very accurate measurement of the detection method using preliminary voltage pulses, reaching a reproducible state without a gap between the piezoelectric stack and the injector valve assembly at each time the injection is to begin. Thus, injection maneuvers may be completely independent of the absolute length of the piezoelectric stack, the effects of wear, and the like. As a result, negative interference variables such as changes in the absolute length of the piezoelectric stack and in particular the effect of wear on the needle sheet can be eliminated, and a reproducible opening and closing response from the injector needle can be obtained.

At the same time, the required reserve voltage pulse means that by applying the reserve voltage pulse it is possible to detect when the gap can no longer be compensated, which means that service is required. In this case, the signal can be output to the outside as a wear indicator.

Preferably, the preliminary voltage pulse is determined from the gap size identified using the detection method, which in particular is newly determined for each activation cycle of the injector valve assembly. Thus, it is also possible to ensure that the gap size that changes over the lifetime is continuously compensated for the lifetime of the device.

Preferably, the detection method is performed in a first operating cycle of the injector valve assembly and the application of the preliminary voltage pulse to the actuator unit is performed during a second operating cycle of the injector valve assembly occurring after the first operating cycle. Thus, the detection method is advantageously used, among other things, to detect how large the gap size is at present, so that the required preliminary voltage pulse can be identified. Until the next activation cycle, this preliminary voltage pulse is not used to compensate the gap.

In this case, if a preliminary voltage pulse is provided to the actuator unit considerably earlier, it is advantageous that a voltage pulse for opening the injector needle can be output to the actuator unit without a time delay as provided for this. For example, the preliminary voltage pulse can also be provided quickly immediately after the detection method is performed, even though the actual subsequent injection will not occur until much later.

It is advantageous for the first activation cycle and the second activation cycle to be directly continuous with one another in time.

In general, the entire injector includes an actuator, a valve assembly having a valve seat and a valve piston, and a nozzle having a nozzle seat and a needle.

The injector unit for injecting fuel into the combustion chamber of the internal combustion engine has an injector valve assembly having an injector needle, the injector needle and the needle seat forming the injector valve. The injector unit also has a piezoelectric stack having an actuator unit and a sensor unit that are coupled to each other in a pressure fit manner. In this case, the sensor unit is configured to detect a force gradient acting on the actuator unit, and the actuator unit is configured to activate the injector valve assembly. The piezoelectric stack and injector valve assembly have a gap with an unknown gap size formed therebetween. Also provided is a control unit configured to detect a voltage signal of the sensor unit and apply a voltage pulse to the actuator unit. In this case, the control unit is configured to perform the above-described detection method and to carry out the above-mentioned starting method.

For this purpose, the control unit has, for example, two cited groups of characteristic curves, and means for detecting the voltage gradient of the voltage signal of the sensor unit. The control unit also advantageously has an element that can be used to ascertain the gap size of the gap and the required magnitude of the preliminary voltage pulse to close the gap from various parameters. It is also advantageous for the control unit to have an output device for outputting a voltage pulse to the actuator unit, so that the actuator unit can change its length along the actuator unit longitudinal axis.

Advantageous refinements of the invention are described in more detail on the basis of the accompanying drawings in which:
1 shows a schematic diagram of a first embodiment of an injector unit having an injector valve assembly and a piezoelectric stack, the injector unit operating according to a functional principle that is operated directly;
2 shows a schematic diagram of a second embodiment of an injector unit having an injector valve assembly and a piezoelectric stack, the injector unit operating in accordance with the functional principles of servo operation;
3 shows a schematic longitudinal cross-sectional view through the piezoelectric stack of FIGS. 1 and 2 in more detail;
4 is a flow diagram illustrating a detection method for detecting a gap size of a gap between the injector valve assembly and piezoelectric stack of FIGS. 1 and 2;
5 is a flow chart illustrating a method for starting the actuator unit of the piezoelectric stack of FIGS. 1-3 to overcome the detected gap as shown in FIG.
6 is a schematic diagram of a control unit configured to execute the detection method shown in FIG. 4 and the start up method shown in FIG.

1 and 2 are schematic diagrams of the injector unit 10 used to inject fuel into the combustion chamber of the internal combustion engine, respectively. The injector unit 10 has an injector valve assembly 12 and a piezoelectric stack 14 that can be used to activate the injector valve assembly 12. The injector valve assembly 12 has an injector needle 16 configured to interact with the needle seat 18 such that the injector valve 20 is formed. When the injector needle 16 is raised away from the needle seat 18, the injector valve 20 is opened and fuel can be injected into each combustion chamber connected to the injector unit 10. However, when the injector needle 16 comes in contact with the needle seat 18 again by pressure fitting, the injector valve 20 is closed and the fuel injection ends.

The piezoelectric stack 14 has an actuator unit 22 and a sensor unit 24, as described in more detail below with reference to FIG. 3. These units are disposed one above the other in the piezoelectric stack 14 along the actuator unit longitudinal axis 26, and the sensor unit 24 is placed on top of the actuator unit 22 (see FIG. 3) or of the actuator unit 22. It may be placed elsewhere below.

The piezoelectric stack 14 is connected with a control unit 28 that can first detect the voltage signal from the sensor unit 24 but secondly also output a voltage pulse to the actuator unit 22. The actuator unit is inflated along the actuator unit longitudinal axis 26.

This expansion along the actuator unit longitudinal axis 26 causes, for example, the piezoelectric stack 14 to move towards the injector valve assembly 12 via a pin 30 mounted thereon. In this process, the gap 32 which is always present in the installation state of the injector valve assembly 12 or of the piezoelectric stack 14 is overcome and the gap size 34 of that gap is changed over the life of the individual elements. Once the gap 32 is overcome and the actuator unit 22 is further deflected along the actuator unit longitudinal axis 26, the injector needle 16 is moved from the piezoelectric stack 14 by the operation unit 36. It is lifted from the needle sheet 18 by the force acting on the operation unit 36. When the voltage application to the actuator unit 22 ends, the actuator unit retracts along the actuator unit longitudinal axis 26 to terminate the contact between the injector valve assembly 12 and the piezoelectric stack 14 and the injector needle. 16 may return the needle sheet 18 again.

1 shows a directly operated functional system in which the operation unit 36 raises the injector needle 16 from the injector needle 18 by the lever 38 when a force is applied from the piezoelectric stack 14.

2 shows an alternative refinement in which the injector unit 10 functions by servo operation, the operation unit 36 exerting a closing force on the injector needle 16 by the fluid pressure present in the control chamber 40. And a fluid filling control chamber 40 which maintains the injector needle in the needle sheet 18 in this manner. When the piezoelectric stack 14 contacts the valve element 42 of the operation unit 36 via the pin 30, the fluid pressure in the control chamber 40 is reduced, so that the injector needle 16 causes the needle sheet ( 18).

FIG. 3 shows a schematic longitudinal cross section through the piezoelectric stack 14 of FIGS. 1 and 2 in more detail.

The piezoelectric stack 14 has an actuator unit 22 and a sensor unit 24, which are arranged up and down each other along the actuator unit longitudinal axis 26 in the exemplary embodiment shown in FIG. 3, in particular The sensor unit 24 is disposed on the side of the actuator unit 22 remote from the injector valve assembly 12. However, reverse arrangement of the actuator unit 22 and the sensor unit 24 is also possible.

The actuator unit 22 includes a plurality of electrode layers and a plurality of material layers, arranged in response to an electric field application and alternately stacked with one another along the actuator unit longitudinal axis 26. The electrode layer and the material layer are not shown in FIG. 3 for clarity reasons. Electrical contact with the electrode layer is through an external electrode 44 electrically connected to the electrode layer via an electrical conductor 46. However, contact with the external electrode 44 can also be made in other ways. The external electrode 44 is connected to the control unit 28, which can transmit voltage pulses to the actuator unit 22 using the external electrode 44 so that the actuator unit is the actuator unit longitudinal axis 26. ) Can expand. The actuator unit 22 is connected to the sensor unit 24 by a pressure fit. The sensor unit 24 also advantageously has a sensor body 48 formed of the same material as the material forming the material layer of the actuator unit 22, for example. The sensor body 48 has, in particular, electrode layers 50 arranged on two opposite side regions 52 arranged along the actuator unit longitudinal axis 26. The electrode layer 50 is connected to a voltage measuring device 54 which forwards the voltage signal of the sensor unit 24 to the control unit 28.

Since the control unit 28 can detect the voltage signal of the sensor unit 24 transmitted through the voltage measuring device 54, all force gradients generated in the piezoelectric stack 14 are controlled by the control unit 28. Can be detected.

This also allows the control unit 28 to be used to perform a detection method that can be used to reliably detect the gap size 34 of the gap 32 between the injector valve assembly 12 and the piezoelectric stack 14. do.

A flow chart for the detection of this gap size 34 is shown at this end of FIG. 4.

First, the flowchart includes the first time t ₁ being detected, in which the actuator unit 22 has a voltage pulse applied from the control unit 24 to the actuator unit. Next, it is detected when the voltage gradient dU occurs at the second time t ₂ in the voltage signal reported from the sensor unit 24 to the control unit 28. Then, from the two times t ₁ , t ₂ , the period Δt elapsed before the voltage gradient dU occurs can be detected. Subsequently, by using the first group K ₁ of characteristic curves that set the gap size 34 based on the period Δt, the gap size 34 present at this point in time can be identified. At the same time, the voltage signal of the sensor unit 24 is further detected by the control unit 28, so that the third time t _{3 at} which another voltage gradient dU occurs, i.e., the injector needle 16 has a needle sheet. It can be seen when it rises away from (18). To distinguish between the second time t ₂ and the third time t ₃ , an arithmetic sign of the voltage gradient is used, which is positive at time t ₂ and negative at time t ₃ . Over time, in particular in the case of directly driven injector units, an additional voltage gradient dU with a positive arithmetic sign can also be detected at the fourth time t ₄ , which is a function of the injector needle 16. Due to closure.

FIG. 5 is a flow diagram schematically showing a starting method that may be used to start the actuator unit 22 via the control unit 28. The flowchart includes first identifying the gap size 34 of the gap 32 between the injector valve assembly 12 and the piezoelectric stack 14, as described with reference to FIG. 4. From the second group of characteristic curves K ₂ , which sets the magnitude of the preliminary voltage pulse required to close the gap 32 based on the identified gap size 34, the preliminary voltage required to close the gap 32. The magnitude of the pulse is checked.

Subsequently, in a subsequent step, this preliminary voltage pulse is applied to the actuator unit 22. The actuator unit 22 then has an open pulse applied to itself to lift the injector needle 16 away from the needle sheet 18.

The control unit 28 is configured to perform both the confirmation method shown in FIG. 4 and the activation method shown in FIG. 5. For this purpose, the control unit 28 has a group K ₁ and K ₂ of characteristic curves as schematically shown in FIG. 6. Also provided is a detection device 56 for detecting a voltage gradient dU of the voltage signal from the sensor unit 24. The control unit 28 also includes an output device 60 including a timing device 58 and an open pulse output device 62 that outputs an open pulse to the actuator unit 22 to open the injector needle 16. ). The open pulse output device 62 provides the timing device 58 with a signal when the open pulse is output to the actuator unit 22. The detection device 56 provides the timing device 58 with a signal when the voltage gradient dU is confirmed by the sensor unit 24. From this, the timing device 58 can determine the period Δt.

In addition, the control unit 28 has a confirmation unit 64 provided to confirm the gap size 34. For this purpose, the confirmation unit is supplied with the detected period Δt, the group of characteristic curves K ₁ , and the magnitude of the open pulse from the timing device 58. From these data, the gap size 34 can be identified because the group K ₁ of characteristic curves sets the gap size 34 based on the period Δt and the magnitude of the open pulse.

In addition, the control unit 28 has a second group of characteristic curves that set the preliminary voltage pulses necessary to close the gap 32, in particular based on the identified gap size 34 and the identified gap size 34. K ₂ ) has a determining unit 66 provided to determine the magnitude of the preliminary voltage pulse. The output device 60 includes not only the open pulse output device 62 but also the preliminary voltage pulse output device 68 to which the preliminary voltage pulse determined from the determination unit 66 is supplied. Subsequently, the preliminary voltage pulse output device 68 outputs a signal corresponding to the determined preliminary voltage pulse to the actuator unit 22 so that the actuator unit 22 causes the actuator unit longitudinal axis 26 to disappear. Can expand along.

Claims (10)

A detection method for detecting a gap size of a gap between an injector valve assembly 12 of an internal combustion engine and a piezoelectric stack 14 for activating the injector valve assembly 12,
Providing a piezoelectric stack 14 having an actuator unit 22 and a sensor unit 24 coupled to each other by a pressure fit, wherein the sensor unit 24 is connected to the actuator unit 22. Providing the piezoelectric stack, configured to detect an applied force gradient;
Providing an injector valve assembly 12 that is activated during operation by the actuator unit 22, wherein the injector valve assembly 12 and the piezoelectric stack 14 have a gap having an unknown gap size 34. Providing the injector valve assembly disposed at a distance from each other over 32);
Detecting a voltage signal of the sensor unit (24);
Applying a defined voltage pulse to the actuator unit (22) to cause the actuator unit (22) to deflect along the actuator unit longitudinal axis (26) while reducing the gap (32);
To the second time (t ₂₎ that is a first time (t ₁₎ beginning with the detected voltage gradient (dU) in the voltage signal of the sensor unit 24 from the beginning to be applied to the voltage pulse generating the voltage pulse Detecting a period Δt that is applied to the actuator unit; And
Identifying the gap size 34 of the gap 32 from the detected period Δt and the defined voltage pulse,
At a third time t ₃ , a second voltage gradient dU is detected in the voltage signal of the sensor unit 24, in which the injector needle 16 of the injector valve assembly 12 causes the needle seat 18. Away from, in particular a negative voltage gradient dU is detected in the voltage signal of the sensor unit 24,
At a fourth time t ₄ , a third voltage gradient dU is detected from the voltage signal of the sensor unit 24, and at this time, the injector needle 16 is pressed against the needle sheet 18 by pressure fitting. The fourth time t ₄ and the second time t ₂ surround the third time t ₃ , in particular at the fourth time t ₄ of the sensor unit 24. A detection method, characterized in that a positive voltage gradient dU is detected in the voltage signal. 2. The gap size 34 of the gap 32 between the piezoelectric stack 14 and the injector valve assembly 12 is detected every every activation cycle of the injector valve assembly 12. Detection method. The detection method according to claim 1 or 2, wherein a positive voltage gradient (dU) is detected in the voltage signal of the sensor unit (24) at the second time (t ₂ ). delete delete As a starting method for starting the actuator unit 22 of the piezoelectric stack 14 for activating the injector valve assembly 12 of an internal combustion engine,
The actuator unit 22 has a predetermined open voltage pulse applied to the actuator unit to raise the injector needle 16 of the injector valve assembly 12 away from the needle seat 18,
The open voltage pulse,
Detecting the gap size (34) of the gap (32) between the piezoelectric stack (14) and the injector valve assembly (12) by performing the detection method as claimed in claim 1 or 2; And
Applying a preliminary voltage pulse to the actuator unit 22 to close the gap 32 between the actuator unit 22 and the injector valve assembly 12.
The actuation method is later applied to the actuator unit (22). 7. The preliminary voltage pulse according to claim 6, wherein said preliminary voltage pulse is determined from said gap size (34) identified using said detection method, said preliminary voltage pulse being newly determined for each activation cycle of said injector valve assembly (12). Starting method characterized in that. The method of claim 6, wherein the detection method is performed in a first activation cycle of the injector valve assembly 12, wherein application of the preliminary voltage pulse to the actuator unit 22 occurs at a time after the first activation cycle. Starting in the second activation cycle of the injector valve assembly (12). 9. A method according to claim 8, wherein the first activation cycle and the second activation cycle are directly continuous with each other in time. As an injector unit 10 for injecting fuel into a combustion chamber of an internal combustion engine,
An injector valve assembly (12) having an injector needle (16), wherein the injector needle (16) and the needle seat (18) form an injector valve (20);
A piezoelectric stack 14 having an actuator unit 22 and a sensor unit 24 coupled to each other by a pressure fit, the sensor unit 24 being configured to detect a force gradient acting on the actuator unit 22. And the actuator unit 22 is configured to activate the injector valve assembly 12, the gap of an unknown gap size 34 in which the piezoelectric stack 14 and the injector valve assembly 12 are formed therebetween. A piezoelectric stack having 32; And
A control unit 28 configured to detect a voltage signal of the sensor unit 24 and apply a voltage pulse to the actuator unit 22,
The control unit (28) is configured to carry out the detection method according to claim 1 or 2.

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