EP4339441A1

EP4339441A1 - Method for an activation and deactivation of a bank of an internal combustion engine

Info

Publication number: EP4339441A1
Application number: EP23196328.1A
Authority: EP
Inventors: Fabio Ramundo; Raul Rodriguez; Tommaso CANGEMI
Original assignee: FPT Industrial SpA
Current assignee: FPT Industrial SpA
Priority date: 2022-09-15
Filing date: 2023-09-08
Publication date: 2024-03-20

Abstract

Method of managing a changeover between an activation condition and a deactivation condition and viceversa of a bank (E1, E2) of an internal combustion engine (E) comprising a first (E1) and a second bank (E2), the method comprising a step of respectively gradual decrease or increase of a torque supplied by a first bank (E1) subject to deactivation or reactivation and a corresponding increase or decrease of a torque supplied by the second bank (E2).

Description

Field of the invention

The present invention relates to the field of methods of managing the switching between the activation and deactivation conditions of a bank of an internal combustion engine comprising two banks.
In particular, the invention concerns a diesel engine implementing the method.

State of the art

The deactivation and relative reactivation of a non-zero subset of the cylinders of an internal combustion engine is known. This technique is generally named CDA by the acronym Cylinders De-Activation.
CDA can be used primarily to manage exhaust gas temperature in diesel engines. In fact, it allows maintaining a sufficiently high temperature of the exhaust gas post-treatment systems when the engine is operated at low rotation speed and low load. This effect allows to avoid the activation of techniques that aim at forcing the heating of the exhaust gas post-treatment system while operating the engine at low load and low rotation speed. These heating techniques, in fact, tend to worsen fuel consumption and produce unburned hydrocarbons.
The CDA allows to reduce the flow of air that does not participate in combustion, towards the engine exhaust manifold, reducing its cooling.
CDA, both in diesel engines and in Otto cycle engines, also allows improving fuel consumption at low load and low engine rotation speed thanks to the elimination of pumping losses in the subset of deactivated cylinders and at the same time allows operate the remaining active cylinders at a greater load, proportionally, to the ratio between the active cylinders and the total number of engine cylinders. The movement of the working point of the active cylinders is carried out to achieve greater efficiency of the engine itself or to reach an operating condition that benefits the operation of the exhaust gas post-treatment device.
CDA is essentially based on the possibility of deactivating the valve train of a cylinder and deactivating the introduction of fuel into the same cylinder while the engine is operated.
Generally, CDA in combustion is activated when the engine is operated in an operating area below a predetermined load and rotational speed.
In engines comprising two banks arranged in a V, CDA is generally operated for an entire bank.
In order to equalize the deterioration of the two banks, the CDA is appropriately alternated between the two banks.
Deactivation of the valve train is generally achieved, after deactivation of the relative injector, when the valves are closed to prevent the valves from being damaged by hitting their seats.
It is therefore clear that CDA is designed to be an ON/OFF type process.
However, if the engine is under constant torque generation conditions and the CDA enable conditions are met, the processing unit that controls engine operation, generally referred to as the ECU, commands the initiation of CDA for a bank and at the same time increases the fuel injected into the other bank to keep the overall torque generated by the engine unchanged, despite the reduction in the number of active cylinders. During this transitory condition, i.e. in the time interval of deactivation of one bank and increase in load for the other bank, the dynamic response of the air circulating in the intake manifold must be sufficiently fast to allow the bank that remains in combustion to have sufficient air to allow the increased injected fuel to burn adequately.
During the transitional condition there is a large production of unburned hydrocarbons HC and CO by the cylinders that remain active and the production of NOx by the cylinders subject to deactivation.
Similar considerations can be proposed when the transient condition leads to the deactivation of the CDA, which corresponds to the reactivation of all the cylinders of the internal combustion engine.
CDA operated while the engine is dragged is also known, for example when the vehicle is going downhill. However, this condition of the CDA is not the object of the present invention.
According to the CDA activation and deactivation management schemes, there are significant variations in the torque delivered by the internal combustion engine.

Summary of the invention

The aim of the present invention is to indicate a method of managing a changeover between an activation condition and a deactivation condition and viceversa of a bank of an internal combustion engine comprising two banks, so as to minimize variations in torque generated by the engine internal combustion.
Another purpose of the present invention is to limit, following the activation of the CDA, the emission peaks of HC and CO relative to the cylinders that remain active and of NOx relative to the cylinders subject to deactivation.
The present invention refers exclusively to CDA in combustion, i.e. while the engine delivers a driving torque.
The basic idea of the present invention is to gradually transfer the torque generated by the two banks towards a single bank, so that only one of the two banks generates all the torque requested to the engine, and subsequently to deactivate the other bank.
This transfer is essentially carried out by applying a negative ramp to the flow of fuel injected into the bank subject to deactivation and a positive ramp to the flow of fuel injected into the bank which remains operational.
Preferably, the transfer of the torque supplied from one bank of the engine to another does not only imply a reduction of fuel in one bank and a similar increase of fuel in the other bank, as it is possible to take further phenomena into account.
According to a preferred aspect of the present invention, the two banks of the same internal combustion engine are modelled using two independent models.
Each model estimates the efficiency of the respective bank

depending on the supply pressure measured "at the Rail" and
the fuel injection timing,

On the basis of these estimates, the fuel injection on the two banks is controlled.
In particular, the variation in pumping losses of the bank being switched off, caused precisely by the gradual deactivation or activation procedure, is taken into account to regulate the injection of fuel into the bank which remains active.
More specifically, each model estimates the mass of air trapped in the cylinders of the bank subject to deactivation, before and after the deactivation of the relevant valve train, and estimates the pumping losses until the air trapped in the cylinders is completely dissipated.
So that, after the deactivation of one of the two banks, the pumping losses caused by the trapped air follow a negative exponential trend. This involves an additional contribution of fuel to be injected into the bank, which remains active according to a similar trend, in order to compensate for these pumping losses.
When the CDA procedure is deactivated, the valve train of the deactivated bank is first reactivated and then power is resumed on that bank in order to transfer half of the torque generated by the engine. The transfer of the torque generated by the engine from a single bank to both banks is carried out as in the activation phase of the CDA procedure, by means of a positive ramp, which gradually increases the power supply of the reactivated bank and at the same time a negative ramp which gradually decreases the power supply to the bank that has remained active, so as to obtain a fair distribution of the torque generated by the engine between the two banks. By engine-generated torque, it is meant "the total torque generated by the internal combustion engine".
According to a preferred aspect of the present invention, the injection of fuel into the bank being deactivated or reactivated is interrupted when a predetermined air/fuel ratio is reached for a diesel cycle engine, hereinafter indicated with the symbol "A/F", with the aim of limiting the generation of NOx in the cylinders subject to deactivation.
According to a further aspect of the present invention, the urea-based reducing agent injector, arranged upstream of the SCR, from the acronym "Selective Catalytic Reduction", which is a NOx reduction device, is controlled to increase a flow rate of reducing agent during the deactivation or reactivation of a bank, in order to compensate for any increase in NOx produced by the bank being turned off or reactivated.
According to a preferred variant of the invention, which is combined with any of the previous variants, a delayed fuel injection timing is applied to the bank being shut down, so as to limit the generation of NOx.
The dependent claims describe preferred variants of the invention, forming an integral part of the present description.

Brief description of the figures

Further objects and advantages of the present invention will be clear from the following detailed description of an example of its implementation (and its variants) and from the attached drawings given purely for explanatory and non-limiting purposes, in which:

+ Fig. 1 schematically shows an internal combustion engine equipped with two banks, i.e. two groups of cylinders with relative pistons operationally connected to a common crankshaft;
+ Fig. 2 discloses a time diagram of several representative curves from top to bottom
- Average torque TT delivered by the engine and the average torque TBK1 and TBK2 delivered by each bank;
- The CDA Request Signal bank deactivation request signal,
- The Wx Signal control signal of the valve train deactivation means of a bank,
- Boost Pressure,
- VGT Position control signal of the turbine geometry configuration,
- SOIBK1 and SOIBK2 injection timing of each of the two cylinder banks.
+ Fig. 3 shows a high-level control diagram representative of the models used to control the power supply of the engine banks.

The same reference numbers and letters in the figures identify the same elements or components or functions.
It should also be noted that the terms "first", "second", "third", "higher", "lower" and the like may be used here to distinguish various elements. These terms do not imply a spatial, sequential, or hierarchical order for the modified elements unless specifically indicated or inferred from the text.
The elements and characteristics illustrated in the different preferred embodiments, including the drawings, can be combined with each other without departing from the scope of protection of the present application as described below.

Detailed description

Fig. 1 shows an internal combustion engine E with two V-cylinder banks, E1 and E2.
Hereinafter a bank or a group of cylinders will be referred. However, since the engine is divided into two banks, the group has a number of cylinders equal to half the total number of cylinders. Furthermore, when the engine is operational, the expansion phase alternates neatly between the cylinders of the two groups.
Each bank includes means for implementing the opening of the intake and exhaust valves and means for deactivating the means for implementing the opening of the intake and exhaust valves, indicated by VV1 and VV2.
For example, the solutions shown in US10851682B2 can be implemented to simultaneously create the means for implementing the opening of the valves and means for deactivating the means for implementing the opening of the valves, both for the intake valves and for the exhaust valves.
The engine is equipped with fuel injection means EJ1 and EJ2 to inject fuel into the cylinders of the first E1 and second bank E2, respectively.
The cylinders are evidently equipped with respective pistons operationally connected to a common crankshaft KK, ECU control means are arranged to control the operation of the engine. These are arranged to receive a torque request from a user, for example through an accelerator pedal or from the cruise control, and to control the delivery of torque by the engine E.
The processing unit is configured to determine when it is appropriate to keep all the cylinders active or when it is appropriate to activate the CDA deactivation procedure of one of the two banks.
According to the present invention, any procedure for deactivating and activating a bank of cylinders includes the gradual transfer of the torque delivered from one bank to another, respectively so that only one bank delivers the required power to the engine or so that the banks contribute equally.
Evidently, any gradual transfer of the delivered torque can only be performed while the valve actuation means are active. Therefore, in the event of deactivation of a bank, the torque is first transferred between the banks and then the deactivations means are activated to deactivate the means for actuating the opening of the valves. Conversely, to reactivate a bank it is necessary first to reactivate the means for implementing the opening of the valves and then gradually transfer the torque between the banks until the overall torque is equally distributed on both banks.
In Fig. 4 essentially only two injectors EJ1 and EJ2 are shown. Evidently, in the case of a diesel cycle engine, each cylinder is equipped with its own injector to inject the fuel directly into the combustion chamber.
The means for deactivating the valve actuation means generally comprise a solenoid valve, which is used to pressurize a device which deactivates the valve actuation means. For each of the two banks two solenoid valves are therefore necessary, one for the intake valves and one for the exhaust valves.
Therefore, if the engine is divided into two groups of cylinders, a total of four solenoid valves are required to control the activation and deactivation of the means of actuating the intake and exhaust valves of both groups of cylinders.
The control means ECU is configured to control the actuation means VV1 and VV2 of the solenoid valves and the injectors EJ1 and EJ2, so as to achieve the object of the present invention.
For convenience, the symbols VV1 and W2 indicate both the valve actuation means and the control valves for the activation and deactivation of the same actuation means.
For convenience, VVx means any of the means VV1 and VV2 in relation to the controlled bank.
In particular, various calculation processes are carried out in the control means. A first process is responsible for deciding whether or not it is appropriate to deactivate a bank of the engine in relation to its operating point.
When this process decides to deactivate a bank or to reactivate a previously deactivated bank, the ECU controls the injectors EJ1 and EJ2 and the solenoid valves VV1 and VV2 as described above.
Preferably, the control means also implement two identical models to simulate the two banks independently.
Each model estimates the ratio between the torque delivered and the corresponding fuel injected into each operating cylinder bank

of the supply pressure "to the Rail" and
the fuel injection timing,

in order to calculate the corresponding pumping losses. Models can be found in the literature.
On the basis of these estimates, the fuel injection on each of the two banks is controlled.
More specifically, the pumping losses of the bank being deactivated or reactivated contribute to regulating the fuel injected into the other bank, so that the gradual transfer of the delivered torque occurs smoothly and gradually.
After deactivation of the valve actuation means, as is known, air remains trapped in the deactivated cylinders. This air involves additional work, which must be compensated by the bank which remains active until this trapped air is completely dispersed, typically in the engine crankcase.
The fuel injection means of the bank that remains active are controlled to increase the fuel injected according to a positive ramp, while the fuel injection means of the bank being deactivated are controlled to decrease the fuel injected according to a negative ramp. The negative ramp does not necessarily reach a zero injection value in a linear way. A discontinuity can be provided which brings the quantity of fuel injected to zero when this quantity is lower than a predetermined threshold, which can be greater than zero or equal to zero.
This choice can be advantageous when the torque contribution of the bank being shut down is negligible given the excess NOx produced due to excessively lean combustion.
To understand the concept of a negative ramp ended with and interruption step, it is sufficient to look at the first group of curves starting from the top of Fig. 2.
Preferably, the slope of the ramps must be calibrated so as not to exceed the dynamics of the variable geometry turbine TB, i.e. of the variable geometry VGT of the turbocharger TB, which is common for the two banks, so that it can adapt to variations in conditions of enthalpy load.
In fact, by deactivating an entire bank, a change in enthalpy load for the turbine is essentially due to the reduction in the flow of exhausted gas that passes through it following the deactivation of a bank. From this perspective, a single exhaust gas post-treatment device connected to the turbine outlet is envisaged.
More preferably, the slope of the ramps is selected to exploit the dynamics of the VGT, so as to make the transfer of the delivered torque as rapid as possible, but without putting the turbine in crisis.
It is worth highlighting that to increase the quantity of fuel injected into a bank it is necessary to increase the rail pressure. However, the dynamics of the rail pressure appears to be at least an order of magnitude faster than the dynamics of the VGT, therefore, by limiting the slope of the ramps as a function of the dynamics of the VGT one is reasonably certain of respecting all the other dynamics that intervene during the torque transfer procedure between the two banks.
Fig. 2 shows several contemporary curves, plotted as a function of time.
The first group of curves represents the delivery of the torque TT by the engine given by the average torque generated TBK1 and TBK2 by each of the two engine banks.
The second curve represents the CDA Request Signal of the deactivation of an engine bank.
The third curve represents the activation signal of the solenoid valves, which determine the deactivation of a bank. It is noted that there is a time delay between a first instant of start of the step representing the CDA request signal and a second instant of start of the step representing the activation signal of the solenoid valves.
In the time interval between these first and second time instants, the transfer of the couple from one bank to the other takes place. It is, therefore, noted that the first curve TT splits into the two curves TBK1 and TBK2. TBK2 clearly indicates that the second bank is gradually de-powered and then definitively deactivated at the second time instant.
Conversely, when the step representing the deactivation of a bank ceases, the TBK2 curve presents a positive ramp and viceversa the TBK1 curve presents a negative ramp, so that the two average torque output curves TBK1 and TBK2 of the two banks re-join the average common value TT.
In the same time interval, the supply pressure of the rail, the fourth curve from the other, is also appropriately adjusted so as to be able to cope with the greater quantity of fuel to be injected into the only bank that remains operational during and after the deactivation of the other banked.
The fifth curve represents the VGT variable geometry adjustment. It can be clearly seen that the VGT is adjusted to compensate for the deactivation of one bank and then stabilizes at a lower value, when the engine, despite delivering greater torque, has reactivated both banks.
The last curve reports the fuel injection advance times for the two banks. Also in this case it can be seen, especially when compared with the first curve, that not only the quantity of fuel injected is reduced, but its injection is also delayed to limit the production of polluting species such as NOx.
Substantially, when the ECU judges that it is possible to satisfy the torque request by using a single bank, then the torque supplied by the two banks differs: so that while the first progressively reduces the torque supplied, the second gradually compensates for the lower torque supplied by the first bank.
At the same time, the fuel injection means of the bank being deactivated are controlled to decrease the injected fuel according to the negative ramp.
When the valve actuation means of the bank being deactivated are deactivated, the model calculates the air trapped in the cylinders and the consequent pumping losses. At the same time, the fuel injection means of the other bank are controlled so as to inject an additional quantity of fuel proportional to the pumping losses caused by the air trapped in the cylinders.
Fig. 3 shows a block diagram of the control of the two banks. The two models MD1 and MD2 of the respective banks E1 and E2 receive various engine-operating parameters as input, including

Engine speed,
Boost pressure,
Pressure measured at the rail,
Torque required for the respective banks,
Injection timing for the respective banks,
Exhaust pressure,
Friction losses in the respective banks,
Status of the Oil Control Valves on the respective banks to determine the collapse or activation of the exhaust valves,
Boost pressure on the respective cylinder banks when the intake valves are deactivated.

Based on these parameters, the models estimate the pumping losses of the respective bank.
This information is passed to blocks FC1 and FC2 which calculate the fuel to be injected into the respective bank and on the basis of

the torque required for the respective bank and control the injectors EJ1 and EJ2 accordingly;
crankshaft KK rotation speed,
current pressure at the "Rail" fuel line,
injection timing.

When one of the banks is deactivated, information about the pumping losses is made available to the FCx block of the other bank to compensate for them.
Blocks FC1 and FC2 can also control the injection advance and other engine operating parameters.
When the engine has positive ignition, to control the torque delivered by each of the two banks it is further necessary to equip the intake manifolds of each bank with a respective butterfly valve. In this way, it is possible to transfer the torque from one bank to the other, guaranteeing stoichiometric power supply to both banks.
When the engine is diesel cycled, however, it is easier to transfer the torque delivered between the two banks, but lean combustion leads to an increase in NOx. To overcome this problem, it is intervened on the timing of the fuel injection of the bank being switched off, delaying it with respect to a reference timing and/or it is intervened on the common exhaust gas post-treatment system (ATS) with a greater injection of Urea-based reducing agent.
Generally, the ATS includes additional components, including a DOC in the case of a diesel cycle engine or a three-way catalyst in the case of a positive ignition engine.
Furthermore, the ATS can be equipped with a particulate filter and means for eliminating excess ammonia downstream of all the components of the ATS.
According to a further preferred variant of the invention which can be combined with any of the previous variants, the deactivation of a bank can be achieved, for a diesel cycle engine, when, as the air-fuel ratio increases, it reaches a predetermined value.
The present invention can advantageously be carried out by means of a computer program, which includes coding means for carrying out one or more steps of the method, when this program is executed on a computer. It is therefore understood that the scope of protection extends to said computer program and further to computer readable means comprising a recorded message, said computer readable means comprising program coding means for carrying out one or more steps of the method, when said program is run on a computer.
Constructive variations to the non-limiting example described are possible, without departing from the scope of protection of the present invention, including all the equivalent embodiments for a person skilled in the art, to the contents of the claims.
From the above description, the person skilled in the art is able to realize the object of the invention without introducing further construction details.

Claims

Method of managing a changeover between a condition of complete activation and a condition of complete deactivation and viceversa of a first bank (E1, E2) of an internal combustion engine (E) comprising said first (E1) and a second bank (E2), the method comprising a step respectively of gradual decrease or increase of a torque supplied by the first bank (E1), subject to complete deactivation or complete reactivation, and a corresponding increase or decrease of a torque supplied by the second bank (E2), so that an overall torque delivered by the engine constantly coincides with a previously acquired target torque.
Method according to claim 1, wherein when the first bank is subject to deactivation the method comprises in succession:
- gradual decrease in the torque supplied by the first bank and simultaneous and proportionate increase in the torque supplied by the second bank,

- deactivation of the actuation means of the intake and exhaust valves (VV1, VV2) of the first bank when the torque supplied by the first bank reaches a pre-established threshold.
Method according to claim 1, wherein when the first bank is subject to reactivation the method comprises in succession,
- reactivation of means for actuating the intake and exhaust valves of the first bank,

- gradual increase in the torque supplied by the first bank and simultaneous and proportionate decrease in the torque supplied by the second bank, so as to constantly and overall equal the torque required from the engine (E).
Method according to any one of the previous claims, wherein said internal combustion engine comprises at least one turbocharger equipped with a variable geometry turbine, and wherein said torque increase and decrease steps are carried out according to ramps having a slope as a function of a dynamics of the variable geometry.
Method according to claim 2, further comprising a step of deactivating the first bank by deactivating the relating actuation means of respective intake and exhaust valves and of estimating a mass of air trapped in the first bank, following the deactivation of the actuation means of the intake and exhaust valves, and to calculate corresponding pumping losses and to simultaneously compensate said pumping losses by means of a corresponding and proportionate quantity of fuel to be injected into the second bank.
A method according to any one of the preceding claims, further comprising a step of delaying a fuel injection timing in the first bank during the increase or decrease phase of the delivered torque, respectively during the reactivation or deactivation condition, so as to limit a NOx generation.
The method according to any one of the preceding claims, wherein when the internal combustion engine is spark ignited, the method comprises a preliminary step of arranging a throttle valve for each bank or a throttle valve for each intake manifold of each cylinder so as to maintain a stoichiometric power ratio of each cylinder during the gradual deactivation or activation of the bank.
Control unit (ECU) for controlling the operation of an internal combustion engine comprising two cylinder banks, configured to operate a changeover between an activation condition and a deactivation condition and viceversa of a cylinder bank (E1, E2) of the internal combustion engine (E) and configured to carry out all the steps of any of claims from 1 to 7.
Computer program comprising instructions for causing the processing unit of claim 7 to implement the method according to any of claims 1 to 7.
A computer readable medium having stored the program of claim 9.
Internal combustion engine (E) comprising first (E1) and second banks (E2), first and second injection means (EJ1, EJ2) for injecting fuel independently into the first and second banks and actuation means (VV1, VV2) to implement the independent opening of intake and exhaust valves of the first and second banks and control means (ECU) according to claim 7, to control a changeover between an activation condition and a deactivation condition and viceversa of the first bank (E1), according to the method according to claim 1.