Combustion engine and method for operating a combustion engine

Description

[0001] The invention relates to an internal combustion engine with a crankshaft and a plurality of adjustable camshafts. Furthermore, the invention relates to a method for assembling the internal combustion engine and preparing it for operation.

[0002] An operating method for an internal combustion engine with an electromechanical camshaft adjuster is described in DE 102 59 133 A1. The camshaft adjuster, an arrangement for adjusting the angle of rotation between a camshaft and a crankshaft of the internal combustion engine, has a modular design in this case. Components of the arrangement are also partially used by other control and regulating devices of the internal combustion engine. A control unit of the electric motor of the camshaft adjuster is connected to a second control unit, which is the engine control unit of the internal combustion engine.

[0003] Hydraulic or electromechanical camshaft adjusters are primarily used as camshaft adjusters. The latter are more complex and expensive, but offer, among other things, improved responsiveness and the advantage of allowing camshaft adjustment even when the combustion engine is at a standstill. For further information, see document DE 10 2012 219 297 A1.

[0004] Further methods for operating camshaft adjusters are disclosed, for example, in documents DE 102 36 507 A1, DE 10 2005 022 714 A1, DE 10 2017 104 015 A1, DE 10 2019 118 689 A1, and DE 102 42 659 A1. DE 10 2019 113 300 B3 shows camshaft control units with two different network topologies, one of which is the CAN bus and the other of which fulfills real-time bus requirements.

[0005] To minimize inertia forces, modern internal combustion engines typically have a camshaft for each valve bank. A V-engine, therefore, typically has two intake and two exhaust camshafts. To maximize the valve train's versatility, the timing of each camshaft is adjustable with its own camshaft adjuster. The camshaft adjusters are independently adjustable and can be individually controlled by an engine control unit via the CAN bus, enabling the greatest possible variability.

[0006] Such a valve train is complex to manufacture and assemble, so it's desirable to use as many common parts as possible. However, the camshaft adjusters still need to be individually adjustable. To achieve this, they must be configured to respond only to the CAN signal intended for them and set the desired target angle.

[0007] Therefore, a system architecture is known from the state of the art in which each camshaft adjuster has a motor including electronics and software, with each electric motor handling the angle determination and control loop of a single camshaft. To enable individual targeting, different configuration data sets are stored in an electronics memory. This requires that different configurations be kept available during manufacture and assembly of the internal combustion engine. Both of these increase production costs and pose the risk of confusion during assembly if the components are otherwise externally identical or similar in order to benefit from the common parts principle.

[0008] Another option is to install identical components and, after assembly at the end of the line, store individual configuration data sets in the camshaft adjusters. This is time-consuming and laborious. Furthermore, there is no guarantee that confusion will occur.

[0009] The invention is based on the object of further developing an internal combustion engine with multiple camshaft adjusters compared to the cited prior art, with the aim of using resources as efficiently as possible. Furthermore, the invention is based on the object of providing a method in which the correct assignment of the camshaft control units can be carried out as automatically as possible.

[0010] The first sub-object is solved by an internal combustion engine having the features of claim 1. The second sub-object is solved by a method having the features of claim 6. The embodiments and advantages of the invention explained below in connection with the device also apply mutatis mutandis to the operating method, and vice versa. Advantageous further developments of the invention are described in the subclaims.

[0011] The internal combustion engine is preferably designed as a reciprocating piston engine and is preferably a four-stroke engine. It has a crankshaft which, via a timing drive, drives several camshafts, by means of which the gas exchange takes place as part of the valve train. The angular position of the crankshaft can be determined using a crankshaft sensor. The crankshaft angle is calculated from the signal from the crankshaft sensor. The calculation can be performed by evaluation electronics located on the sensor, in a central engine control unit, or in another control unit. In a preferred embodiment of the invention, an engine control unit (ECU) makes the crankshaft signal available to other engine subassemblies. The signal can simply be amplified in terms of signal strength and / or enriched with additional information.Signal processing is also possible, so that the crankshaft angle calculated from the crankshaft signal is transmitted as a new crankshaft signal. In the latter case, it can be transmitted digitally as discrete values; preferably, it is provided as a continuous analog signal.

[0012] The internal combustion engine has multiple camshafts. For many internal combustion engines, it is advisable to provide one camshaft per valve bank to minimize moving masses. For example, a V-engine according to the invention has two intake camshafts and two exhaust camshafts.

[0013] At least some, and preferably all, camshafts are adjustable in their phase position relative to the crankshaft by a camshaft adjuster physically connected to the camshaft. The invention also encompasses internal combustion engines in which only some of the camshafts are equipped with camshaft adjusters, or in which one or more camshaft adjusters do not have the properties of claim 1 or participate in the method according to claim 6. For these camshaft adjusters, a logical assignment could be hard-coded, or their logical assignment could be performed manually.

[0014] The camshaft adjusters are controlled or regulated by camshaft control units. These are typically formed by a controller, which is located, for example, in part of an electric motor of an electric camshaft adjuster. In a preferred embodiment, each camshaft adjuster has its own camshaft control unit. The camshaft control unit can be used to adjust the camshaft adjuster to a target value predetermined by the engine control unit. The advantage of locally maintaining a camshaft control unit is that the engine control unit is relieved of computing and thermal load. Furthermore, short signal transmission paths increase control quality and improve electromagnetic compatibility.

[0015] At least two, preferably all, camshaft control units are connected in a line. "Connected in a line" refers to a linear network topology. This means that the camshaft control units logically form a chain, with all links except the outermost ones having a predecessor and a successor. One of the initially outer chain links can be connected to the engine control unit, which then forms the beginning of the chain. The other outer chain link preferably remains unconnected at one end.

[0016] The first network topology is preferably physically predetermined. For this purpose, the camshaft control units are connected to one another, for example by cables. The crankshaft signal is transmitted via this first network topology, whereby in a first state of a camshaft control unit, forwarding of the crankshaft signal is prevented. In a second state, the crankshaft signal is forwarded. It can be passed on unprocessed or amplified. It can be processed or enriched with additional information, for example by modulation. In the second state of the camshaft control unit, the crankshaft signal is preferably replicated by the camshaft control unit. As soon as the camshaft control unit forwards the crankshaft signal, it transmits an additional signal in parallel.

[0017] The predefined, linear network topology enables a delayed, logical assignment of the camshaft control units to the camshaft adjusters. This allows the camshaft adjusters, including the camshaft control units, to be provided as identical parts. Assembly is also simplified because confusion between camshaft adjusters and camshaft control units cannot occur during installation. The camshaft adjusters can be physically installed together with a camshaft control unit. However, during assembly, the camshaft control unit does not know which camshaft it logically belongs to and therefore which camshaft control signal sent by the engine control unit it should respond to.

[0018] The logical assignment only occurs after assembly during a learning process. At the beginning of the learning process, all camshaft control units are in the initial state, meaning that no camshaft control unit is allowed to forward the crankshaft signal.

[0019] Each camshaft control unit that receives the crankshaft signal determines the additional signals arriving simultaneously or within a specified time window. If a camshaft control unit receives only the crankshaft signal but no additional signal within a specified time interval, it assigns itself the logical number 1 in the linear network topology and will henceforth process camshaft control signals from the engine control unit intended for the first camshaft. After the logical assignment to the first camshaft, the camshaft control unit switches to the second state. In this state, it forwards the crankshaft signal and sends an additional signal in parallel. This can be information about its successful assignment; this will usually include its number.

[0020] The additional signal can be transmitted additionally on the first network topology. It is preferably transmitted on a second network topology, such as a CAN bus. The second network topology has fewer bandwidth restrictions and is not limited to a linear topology. Therefore, it is advantageous for the second and first network topologies to be physically separate and configured differently.

[0021] The camshaft control unit physically next in the first network topology receives the crankshaft signal and, at the same time, the additional signal information from the first camshaft control unit, but no additional signal. This allows it to determine that it forms the second link in the chain and logically assigns itself the number 2. Like the first camshaft control unit before it, it switches from the first state to the second state and now forwards the crankshaft signal along with its own additional information. All subsequent camshaft control units operate according to the same principle and can determine their own position in the chain from the number of additional information items sent or from the highest number sent.The advantage of this logical assignment according to the invention is that all camshaft control units can use the same software or circuit logic, and their position in the chain can be determined from the hardware-encoded network topology. The hardware and software of the camshaft control units can thus be identical.

[0022] Since the total number of existing camshaft control units is known, the engine control unit can terminate the learning process as soon as it receives an additional signal from the last camshaft control unit. To increase robustness, a PWM or pulse signal could be generated instead of the disabled replication, which communicates the engine number to the next engine. This can also be provided as a fallback solution, for example, if CAN reception is disrupted.

[0023] The learning process is preferably initiated once after assembly or after one of the camshaft control units has been replaced. For this purpose, each camshaft control unit can be equipped with a permanent data memory, such as an EEPROM, in which the information about the logical assignment is stored, so that the learning process only needs to be performed once.

[0024] When the internal combustion engine is first started or restarted, the information about the logical assignment is then immediately available. Alternatively, the learning process occurs automatically before the internal combustion engine starts if the engine control unit does not receive information about its logical assignment from one of the camshaft control units within a predetermined time window. In another embodiment, learning occurs before each start of the internal combustion engine.

[0025] The described teach-in process is superior to manual assignment because it only needs to be initiated centrally once. Furthermore, no physical access to the camshaft control units is required after installation. Furthermore, incorrect assignment, such as duplicate assignment, is eliminated. There is also little additional work involved in assembly because the camshaft control units are equipped with connectors anyway, so the additional effort is limited.

[0026] In some internal combustion engines, different camshaft adjuster types are installed on the intake and exhaust sides. For cost reasons, often only the intake camshafts are equipped with electric camshaft adjusters, while the exhaust camshafts are equipped with hydraulic camshaft adjusters. This also results in differences in the camshaft control units. For example, in these mixed variants, only some of the camshaft control units participate in the described teach-in process. In the other part of the camshaft control units, their logical position can be determined in a different way. Alternatively, the different camshaft adjuster types can form two chains. In this case, the teach-in method according to the invention is applied to each chain.

[0027] In one embodiment of the invention, control of a camshaft position is only performed after the logical assignment of the corresponding camshaft control unit. This prevents situations in which the internal combustion engine fails to start or in which damage may occur due to different cam geometries. Alternatively, control or regulation takes place within a range that allows emergency operation of the internal combustion engine.

[0028] In summary, the invention enables a common parts strategy in which identical camshaft adjusters including camshaft control units can be installed by the camshaft control units themselves learning to which camshaft they are mounted and logically assigned. Description of the drawing

[0029] An embodiment of the invention is explained in more detail below with reference to a drawing. In the drawings: Fig. 1 shows a symbolic representation of an internal combustion engine with a camshaft adjuster, a camshaft control unit and an engine control unit, and Fig. 2 shows a symbolic representation of an engine control unit which is connected to four camshaft control units via a first network topology.

[0030] One in Figure 1 The combustion engine 1, which is only symbolically represented and whose engine block is designated by 2, has an electromechanical camshaft adjuster 3. An actuating gear 4 of the camshaft adjuster 3 is constructed as a three-shaft gear, for example a wave gear. A first shaft of the actuating gear 4 is identical to or fixedly connected to a belt or chain wheel and rotates in a manner known per se at half the crankshaft speed of the combustion engine 1. A second, output-side shaft of the actuating gear 4 is non-rotatably connected to the camshaft 10 to be adjusted ( Fig. 2). To adjust the angle between the input-side shaft connected to the chain or belt wheel and the output-side shaft of the adjusting gear 4, the latter has a third shaft in the form of an adjusting shaft, which is non-rotatably coupled to the motor shaft of an electric motor 5, which is assigned to the camshaft adjuster 3.

[0031] The electric motor 5 is controlled by the camshaft control unit 6 via a line 9. The camshaft control unit 6 is linked to the engine control unit 7 of the internal combustion engine 1 via a second network topology, in this case a CAN bus 8. The engine control unit 7 is only slightly burdened by the processing of data relating to the operation of the camshaft adjuster 3.

[0032] In Figure 1For clarity, only one camshaft adjuster 3 is shown. In addition to the CAN bus 8, there is a line 15, which links the camshaft control unit 6 to the engine control unit 7 and forms part of a first network topology 16. The line 15 is used to send the crankshaft signal from the engine control unit 7 to the camshaft control unit 6. The data volume of the transmitted crankshaft signal is only a small fraction of the data transmitted via the CAN bus 8 between the camshaft control unit 6 and the engine control unit 7. Thus, in contrast to the CAN bus 8, the information is available practically in real time using the line 15.

[0033] Out of Figure 2shows the first network topology 16 with an engine control unit 7 and four camshaft control units 21, 22, 23, 24, which are connected to one another by a cable 15. The camshaft control units 21, 22, 23, 24 are integrated into the respective drive motors of the camshaft adjusters 11, 12, 13, 14. Together with the engine control unit 7, the four camshaft control units 11, 12, 13, 14 form a chain so that the components are connected in a line. For this purpose, all camshaft control units 11, 12, 13, with the exception of the last one, are connected to exactly two neighbors, with the engine control unit 7 being considered the zeroth link in the chain. Due to the linear topology, well-ordering is possible, so that the sequence is fixed after assembly in the internal combustion engine.

[0034] The crankshaft signal, which is sent by the engine control unit 7, is fed to the camshaft control unit 11 via line 15. The software on the drive motor can control whether replication is active or deactivated. As long as the electric motors do not know their logical position (first state), they are not allowed to replicate the crankshaft signal and transmit it to the CAN bus 8 (in Fig. 2 not shown) do not send.

[0035] If one of the camshaft control units 21, 22, 23, 24 receives a crankshaft signal but no CAN signal from another camshaft adjuster 11, 12, 13, 14 and is not yet logically assigned, it will designate itself as engine number 1 and store this number internally. The camshaft control unit 21 then begins to replicate the crankshaft signal on the first network topology 16 and send information about its number via the CAN bus 8.

[0036] If one of the camshaft control units 21, 22, 23, 24 receives a crankshaft signal, a CAN signal from engine 1, or no CAN signal from another camshaft adjuster 12, 13, 14, and is not yet logically assigned, it will designate itself as engine number 2 and store this number internally. The camshaft control unit 22 then begins to replicate the crankshaft signal on the first network topology 16 and send information about its number via the CAN bus 8.

[0037] If one of the additional camshaft control units 21, 22, 23, 24 receives a crankshaft signal, a CAN signal from n-1 engines, no CAN signals from other camshaft adjusters 11, 12, 13, 14, and is not yet logically assigned, it will designate itself as engine number n and store this number internally. The camshaft control unit 23, 24 then begins to replicate the crankshaft signal on the first network topology 16 and send information about its number via the CAN bus 8.

[0038] The camshaft control units 21, 22, 23, and 24 permanently store the determined engine numbers in their internal memory (EEPROM or similar), so the learning procedure only needs to be performed once after installation or when replacing the engine. Alternatively, the function can also be performed every time the engine is started. The number of camshaft control units 21, 22, 23, and 24 is permanently stored in the engine control unit 7, so that an abort condition exists for this learning process of the logical assignment.

[0039] To increase robustness, instead of the switched off replication, a PWM or pulse signal can be generated in which the engine number can be communicated to the following engine, for example if CAN reception is disturbed. List of reference symbols

[0040] 1 Internal combustion engine 2 Engine block 3 Camshaft adjuster 4 Actuating gear 5 Electric motor 6 Camshaft control unit 7 Engine control unit of the internal combustion engine 8 CAN bus 9 Cable 10 Camshaft 11 First camshaft 12 Second camshaft 13 Third camshaft 14 Fourth camshaft 15 Cable 16 First network topology 17- 18- 19- 20- 21 First camshaft control unit 22 Second camshaft control unit 23 Third camshaft control unit 24 Fourth camshaft control unit

Claims

1. An internal combustion engine (1), having: - a crankshaft, the position of which is described by a crankshaft angle, - a crankshaft sensor, which provides a crankshaft signal for determining the crankshaft angle, - a plurality of camshafts (10, 11, 12, 13, 14), which each have a camshaft adjuster (3) and a camshaft control unit (6, 21, 22, 23, 24), - a first network topology (16), which connects the camshaft control units (6, 21, 22, 23, 24) to one another in a line and via which first network topology the crankshaft signal can be transmitted unprocessed, amplified or processed, wherein - in a first state, the camshaft control units (6, 21, 22, 23, 24) are designed to prevent the forwarding of the crankshaft signal and in a second state are designed to forward or replicate the crankshaft signal and to send an additional signal.

2. The internal combustion engine (1) according to claim 1, characterised in that - each camshaft control unit (6, 21, 22, 23, 24) has a data memory in which information can be stored regarding which camshaft (10, 11, 12, 13, 14) it is logically assigned to, - the first state is formed by the state of indeterminate logical assignment of the camshaft control unit (6, 21, 22, 23, 24) to a camshaft (10, 11, 12, 13, 14), - the second state is formed by the state of a specific logical assignment of the camshaft control unit (6, 21, 22, 23, 24) to a camshaft (10, 11, 12, 13, 14), - and the additional signal has information about the logical assignment.

3. The internal combustion engine (1) according to claim 1 or 2, characterised in that some or all of the camshaft control units (6, 21, 22, 23, 24) are designed as identical parts in terms of hardware and software.

4. The internal combustion engine (1) according to any one of the preceding claims, characterised by - an engine control device (7), which is connected to exactly one camshaft control unit (6, 21, 22, 23, 24) in the first network topology (16) and which specifies target angles for the camshaft control units (6, 21, 22, 23, 24) using camshaft control signals, - a second network topology, via which both the camshaft control signals from the engine control device (7) to the camshaft control units (6, 21, 22, 23, 24) and the additional signals are sent.

5. The internal combustion engine (1) according to claim 4, characterised in that the first network topology (16) is implemented by cables, wherein each of the camshaft control units (6, 21, 22, 23, 24) has a cable input and a cable output for the first network topology (16) and the second network topology is designed to be physically separate from the first network topology (16).

6. A method for teaching an internal combustion engine (1) according to any one of the preceding claims, characterised in that - in a first configuration phase the camshaft control units (6, 21, 22, 23, 24) do not know their logical assignment to the camshaft adjusters (3), - in a second configuration phase the crankshaft angle signal is supplied to the first camshaft control unit (6, 21, 22, 23, 24) in the first network topology (16) via the first network topology (16), wherein the first camshaft adjustment unit performs its logical assignment to the first camshaft adjuster (3) by the presence of the crankshaft signal in the simultaneous absence of the additional signals, - the first camshaft control unit (6, 21, 22, 23, 24) prevents the forwarding until the logical assignment to the first camshaft adjuster (3) has been made and, after the logical assignment has been made, forwards or replicates the crankshaft signal in the first network topology (16) and sends an additional signal that contains information about its logical assignment.

7. The method according to claim 6, characterised in that the crankshaft angle signal is supplied to a subsequent camshaft control unit (6, 22, 23, 24) in the first network topology (16) via the first network topology (16) after the logical assignment of the preceding camshaft control unit (6, 21, 22, 23) in the first network topology (16) has been completed and the subsequent camshaft control unit (6, 22, 23, 24) performs its logical assignment to the camshaft adjuster (3, 12, 13, 14) by the presence of the crankshaft signal as a function of the additional signal(s) present.

8. The method according to claim 6 or 7, characterised in that the logical assignment is stored in an internal memory of the camshaft control unit (6, 21, 22, 23, 24).

9. The method according to any one of claims 6 to 8, characterised in that the camshaft angles are controlled or regulated exclusively by the camshaft control units (6, 21, 22, 23, 24) after the second configuration phase has been completed.

10. The method according to any one of claims 6 to 9, characterised in that the internal combustion engine (1) has an engine control device (7), and a logical assignment or logical reassignment of the camshaft control units (6, 21, 22, 23, 24) can be brought about by an individual instruction to the engine control device (7).