SE540017C2 - Procedure and system for driving a vehicle, where the charge pressure is controlled - Google Patents

Abstract

The present invention relates to a method of driving a vehicle (100), said vehicle (100) comprising an internal combustion engine (101) having at least one combustion chamber, said vehicle (100) further comprising means for pressurizing air for supply to said combustion chamber, and wherein said vehicle (100) further comprises at least a first braking system. The method comprises: - in reducing a torque request from a second level to a first, compared to said second level lower, level, determining whether said first braking system is activated, and if said first braking system is activated, maintaining the pressure of said air supplied to said combustion at a higher second pressure (P), compared with a first pressure (P) required at said first level (P.)

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method and a system for driving a vehicle. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... In particular, the invention relates to a method and a system for driving a vehicle in which air supply to an internal combustion chamber of a single-combustion engine can be actively influenced. The present invention also relates to a vehicle, as well as a computer program and a computer program product, which implement the method according to the invention. Background of the invention When driving heavy vehicles, such as lorries, buses and the like. Over time, the vehicle economy has had an increasing impact on the profitability of the business in which vehicles are used. In general, in addition to the vehicle acquisition cost, the main expense items are the ongoing operation of a vehicle by the vehicle's driver, costs for repairs and maintenance, as well as fuel for propelling the vehicle.

Depending on the type of vehicle, different factors can have different major impacts, but in general fuel consumption is a large expense item, and since the utilization rate for heavy vehicles is often high, with associated large total fuel consumption, the fuel cost can affect the profitability of an owner of the vehicle. a shipping company or the like, to a very large extent.

Thus, any opportunity to reduce fuel consumption can affect profitability in a positive way, and in particular long-distance driving, it is particularly important to optimize fuel consumption. For example. For this purpose, 10 long-distance vehicles have been developed, which are characterized by a typical cruising speed for the internal combustion engine, whereby the cruising speed is adapted for a certain cruising speed. Typical cruising speeds, depending on the region and / or type of road, can e.g. be 80 km / h, 85 km / h or 89 km / h.

In addition to fuel economy, it becomes increasingly important for heavy vehicles that the vehicle's driving is experienced as comfortable and intuitive for the vehicle's driver. For example. For example, the use of automatic transmission gears, where shifting is controlled, in whole or in part, by the control system normally present in the vehicle, can facilitate the operation of the vehicle.

Automatic shifting also enables additional degrees of freedom in controlling the vehicle's progress from a fuel economy perspective, e.g. by using the vehicle's control system to ensure that the vehicle is driven in a gearbox that is advantageous from a fuel consumption point of view.

However, good driver comfort also means other aspects, such as ensuring good driveability, ie. that the vehicle from a performance point of view at e.g. It is an object of the present invention to provide a method of driving a vehicle which can further reduce the fuel consumption of the vehicles of an internal combustion engine, while the method of performing good driving of the vehicle. This object is achieved by a method according to claim 1.

The present invention relates to a method of driving a vehicle, said vehicle comprising an internal combustion engine, such as e.g. a diesel engine, having at least 10 a combustion chamber, said vehicle further comprising means for pressurizing air for supply to said combustion chamber, and wherein said vehicle further comprises at least a first braking system. The method comprises: - in reducing a torque request from a second level to a first, compared to said second level lower, level, determining whether said first braking system is activated, and - if said first braking system is activated, maintaining the pressure of said to said combustion supplied air wide, compared to a first pressure required at said first level, higher second pressure.

As mentioned above, it is desirable that a vehicle can be driven in as fuel efficient a manner as possible, and as long as the vehicle is driven at a constant speed along a horizontal path, the vehicle's fuel efficiency will be controlled by how close the optimum efficiency of the internal combustion engine operates.

At the same time, it is important many times that the vehicle shows good driveability, and in e.g. a torque request from the driver of the vehicle can respond quickly with an expected increase in torque delivered.

Internal combustion engines, such as e.g. diesel engines, can be dependent on a compression of the combustion air supplied to the combustion in order to be able to emit a high torque / high power, and in order to be able to achieve good drivability, a control is applied in many situations where the pressure of the air supplied to the combustion is maintained. which is actually required from the point of view of incineration. With the aid of the higher pressure, an air margin is created, which means that a certain increase of a quantity of fuel supplied can be carried out without the air / fuel ratio falling during combustion to a value which is too low, whereby the power of the internal combustion engine is made faster available. The air margin thus improves the vehicle's performance, and thus driveability, from a driver's perspective.

A disadvantage of applying such an air margin, i.e. maintaining the air supplied to the combustion wide, compared with a required pressure, higher pressure, is that a larger gas exchange work is performed by the combustion engine, with associated losses as a result.

By determining according to the present invention whether a braking system is activated, i.e. whether a braking force is applied to counteract the travel of the vehicle in the direction of travel, and, in the case said braking system is activated, maintain the pressure of the supply air to the combustion at a higher pressure, the combustion air pressure can be maintained without any increase in losses.

Since a braking system is activated, there will still be a loss in the form of the energy that is converted into the braking system, such as e.g. in the form of heat. By maintaining according to the present invention a high pressure for the air supplied to the combustion, with increased gas exchange work, and thus engine braking force, as a result, applied braking force can instead be reduced to a level corresponding to the losses caused by increased gas exchange work.

Since decelerated energy is often decelerated in a way where the energy is not used for later use, the present invention has the advantage that even if the losses during braking are essentially the same, the higher combustion air pressure will lead to better drivability, ie. the vehicle will be able to be driven with a better response, 10 ie. is experienced more vigorously by the driver of the vehicle because a greater force will immediately be available when needed, e.g. if braking is immediately followed by an acceleration with large torque requirements. The invention thus has as a result that the vehicle can often be driven with a high available force when needed without a negative effect on fuel consumption.

According to one embodiment of the invention, only if one braking system is activated as above is determined, while according to another embodiment of the present invention it is also determined whether an applied braking force exceeds any applicable first braking force. This first braking force edge.ex. consists of a braking force corresponding to the braking force obtained by increased gas exchange work according to the present invention.According to the invention, it is determined whether one driving brake system is activated, dojan: nligt fn another 'fßfw fl fff- »F» WW .å-.a- ~ C «~ + ~ '»' W“ -. ~ L ~ »-» - ~ w! 1 »» Rfwf f ~ «~ + - M1. ~ ßw ~ 1 f \ A \. ».;« ~ J Jlllll-jç Li; ~ _L._, YES \, 1 \ J \ .. I _, '._, L, L_L¿- JJ' _) _'_ \, \ 1¿ LL .LL \, 1 \ VJ \, According to one embodiment of the present invention states that the engine braking system is activated, and as long as the service braking system is not activated, the sustained pressure of the air supplied to the combustion at a higher pressure for a first time is activated for a first time as long as the service braking system is not activated. The earth brake system is activated, the pressure is maintained for the supply air to the combustion during a second compared with the said first time long-term. Since the increase in losses caused by high-pressure air is offset by losses caused by the braking system, the period of time during which the combustion air pressure is maintained is allowed to be longer than is normally the case. According to one embodiment, the combustion air pressure is maintained, provided that a braking system is activated, as long as possible, ie. the combustion air pressure is maintained for as long as possible as long as a braking force is applied. Since the combustion air pressure is usually achieved by means of exhaust gases from the combustion driven turbocharger, and since the internal combustion engine during braking is usually supplied with little or no fuel supply, the resulting low exhaust gas flow will result in the combustion air pressure not being able to recover for some time.

Additional features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments and the accompanying drawings.

Brief Description of the Drawings Fig. 1A shows a driveline of a vehicle in which the present invention can be used; Fig. 1B shows a control unit in a vehicle control system; Fig. 2 shows an exemplary method according to the present invention; Fig. 3 shows an example of driving a vehicle with retention of a combustion air pressure; Fig. 4 shows an example of driving a vehicle with retention of a combustion air pressure according to one embodiment of the present invention; Fig. 5 shows a further exemplary method according to the present invention; Fig. 6 shows yet another exemplary method according to the present invention; Detailed Description of Embodiments Fig. 1A schematically shows a driveline in a vehicle 100 according to an embodiment of the present invention. The vehicle 100 shown schematically in Fig. 1 comprises only one axle 104, 105 with drive wheels 113, 114, but the invention is also applicable to vehicles where more than one axle is provided with drive wheels, as well as to vehicles with one or more additional axles, such as one or more support axles. The driveline comprises a single-combustion engine 101, which in a conventional manner, via a shaft emanating on the internal combustion engine 101, usually via a flywheel 102, is connected to a gearbox 103 via a single clutch 106. The clutch 106 may be a manually or automatically controlled clutch on the cane seed, and be arranged to be shifted by the driver of the vehicle 100 or automatically by the control system of the vehicle. According to an alternative embodiment, the vehicle 100 is provided with a clutch-free driveline.

A shaft 107 emanating from the gearbox 103 drives the sedan gears 113, 114 via an end gear 108, such as e.g. unusual differential, and drive shafts 104, 105 connected to said final gear 108.

The present invention relates to internal combustion engines, in particular diesel engines, in which the amount of air supplied to a single-combustion chamber, such as e.g. a cylinder, can be actively regulated.

In the case of a diesel engine without the possibility of actively regulating the air supplied to the combustion, the combustion air available during combustion will be the air sucked in by the downward movement of the piston, the intake air consisting of air sucked in from the vehicle environment. The amount of air during combustion is thus essentially the same for each combustion cycle (low variations can occur, for example, depending on external factors, such as prevailing air pressure, temperature, etc.).

This means that only a certain amount of fuel can be injected before the combustion air / fuel ratio (AFR) becomes undesirably low. The ratio between a stoichiometric ratio AFRSUW and the actual ratio between air and fuel supplied to the combustion (the ratio between the mass of air (kg) and petrol (kg) supplied to the combustion, is generally called lambda care, Ä, when APR lambda care - is defined as Ä = - As is well known, and AFRstök as appears from the equation means a lambda protection = 1 a fuel / air ratio when stoichiometric combustion is obtained, ie. AFR = AFRQÖL and then major and minor lamb care mean air surplus and air deficit at the time of incineration. As is well known, however, there are methods for increasing the effect of e.g. diesel engines by means of compression of the air supplied to the combustion supply a larger air mass to the combustion, whereby the larger air mass means that a correspondingly larger multipurpose fuel can be supplied with maintained air / fuel ratio, and thus higher power development, as a result.

The compression of supplied air can, as is well known, be accomplished in various ways. For example. the compression can be achieved by means of a turbocharger 119, such as a VGT (variable geometry turbocharger) generator or a turbocharger with dump valve (waste gate). l0 With the help of e.g. such, or other applicable, turbochargers can thus be compressed by the air supplied to the combustion, whereby also lambda values can be regulated since different amounts of air can be supplied for a given amount of supplied fuel.

However, an increase in the lambda value Ä for a given operating point usually also requires a certain increase in the amount of fuel supplied. This is because the supply of a larger amount of air will result in a larger gas exchange work, with associated losses, which may lead to an increase in supplied fuel. to overcome losses caused by increased throttle work so that a desired flywheel torque can still be maintained.

As mentioned above, however, many times it is required that a certain compression is maintained in order for the vehicle to show good drivability from a driver's perspective, despite the fact that this entails increased fuel consumption. The present invention relates to a method for utilizing and maintaining compression in situations when this does not entail any increased cost in driving the vehicle.

An exemplary method 200 according to the present invention is shown in Fig. 2, and the invention may be implemented in any suitable control unit, such as e.g. the control unit 117 shown in Fig. 1A.

In general, control systems in modern vehicles usually consist of a communication bus system consisting of one or more communication buses for interconnecting a number of electronic control units (ECUs), or controllers, and various components arranged on the vehicle. Such a control system may comprise a large number of control units, and the responsibility for a specific function may be divided into more than one control unit.

For the sake of simplicity, in Fig. 1A only the control units 116, 117, 118 are shown, but vehicles 100 of the type shown often comprise considerably more control units, which is well known to those skilled in the art.

In the present example, the clutch is an automatically controlled clutch, the control unit 116 controlling the clutch 106 via a clutch actuator (not shown) as well as the gearbox 103.

The control unit 118 constitutes a brake control unit and is responsible for one or more brake system functions. For example. the vehicle100 comprises a service braking system, which customary e.g. can include brake discs with associated brake pads (not shown) arranged next to each wheel, and the contact pressure of the brake pads against the brake discs is controlled by means of the brake control unit 118, which in a manner sends signals to the regulator (s) regulating braking force in the service brake system. The brake control unit 118 can e.g. be arranged to control only the vehicle's braking system, but may also be arranged to control one or more of the vehicle's other braking systems, where such occurs. For example. For example, the vehicle may include a retarder as shown below, and / or other auxiliary brake systems such as exhaust and engine brakes. Based on applicable commands from eg drivers or other control units, control signals are sent to applicable system modules for the request of the desired braking force.

The control unit 117, in which the present invention in the illustrated embodiment is implemented, controls the engine 101 of the vehicle 100. The invention may alternatively be implemented in a control unit dedicated control unit, or in whole or in part in one or more other control units already existing at the vehicle 100.

The control of the control unit 117 (or the control unit (s) at which the present invention is implemented) control of switching time according to the present invention will probably depend on signals received from other control vehicle arranged (also not shown), and / or information from e.g. . different sensor / sensors arranged at the vehicle. It generally applies that control units of the type shown are normally arranged to receive sensor signals from different parts of the vehicle 100.

Control units of the type shown are also usually arranged to emit control signals to various vehicle parts and vehicle components.

The control is often controlled by programmed instructions. These programmed instructions typically consist of a computer program, which when executed in a computer or controller causes the computer / controller to perform desired control, such as method steps of the present invention. The computer program is usually part of a computer program product, the computer program product comprising an appropriate storage program. l26 stored on said storage medium l2l. The said digital storage medium l2l can e.g. consists of any group: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk drive, etc., and be arranged in or in connection to the control unit, the computer program is executed by the control unit. By following the instructions of the respirator program, the behavior of the vehicle in a specific situation can thus be adapted.

An exemplary control unit (control unit 117) is shown schematically in Fig. 1B, wherein the control unit may in turn comprise a calculation unit 120, which may consist of e.g. any type of flashlight of processor or microcomputer, e.g. a Digital Signal Processor (DSP), or an Application 12 Specific Integrated Circuit (ASIC). The computing unit 120 is connected to a memory unit 121, which provides the computing unit 120 e.g. the stored program code 126 and / or the stored data calculation unit 120 need to be able to perform calculations. The calculation unit 120 is also arranged to store partial or final results of calculations in the memory unit 121.

Furthermore, the control unit 117 is provided with devices 122, 123, 124, 125 for receiving and transmitting input and output signals, respectively. These input and output signals may contain path shapes, pulses, or other attributes, which the devices 122, 125 for receiving input signals may be detected as information for processing the computing unit 120. The output signals 123, 124 for transmitting output signals are arranged to convert calculation results from the calculation unit 120 into output signals for transmission to other parts of the vehicle control system and / or the decomponent (s) for which the signals are intended. Each of the connections to the devices for receiving and transmitting input and output signals, respectively, may consist of one or more of a cable; a data bus, such as a CAN bus (ControllerArea Network bus), a MOST bus (Media Oriented SystemsTransport), or any other bus configuration; or by a wireless connection. Returning to the method 200 shown in Fig. 2, this ice step 201 begins, where it is determined whether the pressure P for the combustion air exceeds any applicable limit value. The pump limit value Plm fl can e.g. be set to a pressure above which the combustion air pressure consists of an overpressure, i.e. a pressure exceeding the saving atmospheric pressure. Thus the range limit Pina e.g. consists of atmospheric pressure. According to a preferred embodiment, however, the limit value Pimu consists of a, 10 l3 compared to the prevailing atmospheric pressure, higher pressure, such as a slightly applicable pressure exceeding the atmospheric pressure. For example. The Pina cantilever care consists of some applicable proportion of the maximum pressure to which the combustion air can be pressurized when driving a vehicle. For example. For example, the boundary material Pina may consist of an arbitrary applicable proportion in the range 70-100% of the maximum pressure Pm fl to which the combustion air is pressurized when driving the vehicle 100, typically at maximum load.

As long as the pressure condition is not met, the residual process in step 201 is performed, while the process thus passes to stage 202 when the combustion air pressure P exceeds the limit value Pina. In step 202, it is determined whether the torque required by the internal combustion engine 101 is reduced. According to an embodiment of the invention, it is determined whether the torque request is reduced to some applicable extent, such as e.g. by a certain number of percentages or to some applicable level, such as any applicable percentage of maximum releasable torque. After the torque request has been reduced according to step 202, the process proceeds to step 203.

This is illustrated at t1 in Fig. 3, which shows an example of a function for improving the driveability of the vehicle 100 from, for example, a driver's perspective. Fig. 3 shows how the fuel supply Q varies over time t when driving the vehicle 100 long (not shown) wave sections. At time t0 the vehicle 100 is driven with a high emitted torque from the internal combustion engine 101, and then with a relatively high fuel supply Q amounting to a level Q2, and at time t1 the torque demand is reduced, whereby fuel supply to the internal combustion engine 10 is reduced by a level Q1 delivered torque. At the same time, the combustion air pressure P of the air supplied to the combustion changes as shown in the figure.

The fuel demand Q of the vehicle 100 can decrease from the relatively high level Q to the relatively low level Q1, e.g. due to the vehicle's 100 driver releasing the accelerator pedal, or due to the torque request being reduced by e.g. a cruise control function. Thus, at time t1, the driving force requirement decreases to a relatively low driving force requirement, but instead of simultaneously controlling the combustion air pressure P in such a way that it sinks as low a level as possible, with associated associated fuel saving as a result, the combustion air pressure is maintained at level P, to the time tg, and only at this time tg the combustion air pressure P is lowered to a level P1, which from a fuel consumption point of view constitutes a combustion air pressure P which gives rise to a more economical air / fuel ratio Ä, and which e.g. results in the lowest air / fuel ratio Ä allowed by eg prevailing government regulations and / or e.g. from the point of view of smoke restriction.

This functionality, called the Low LoadCase (LLC), is intended to maintain a high combustion air pressure P, such as e.g. by maintaining a high turbo speed, for a certain period of time tH, ie. between 1 and tg in Fig. 3, such as e.g. 1-3 seconds, even after a torque request has decreased. In this way, the holding motor response is high during this predetermined time tH to ensure that a high force can be directly, or at least substantially directly, made available if the conditions of the vehicle's performance during said time tH become such that a high driving force is again required, e.g. may be the case if the torque demand is reduced due to shifting to another shift, in which case high power is often desired care immediately after shifting, e.g. If a combustion air pressure P is maintained at the pressure P2 during the period tH, the fuel supply during this time period can be immediately raised again to the level Q2 without risk of the air / fuel ratio Ä being somewhat impermissible, thus the entire time taken out. tooch ti in Fig. 3 directly, or at least substantially directly, is available when needed.

According to the method shown in Fig. 2, the vehicle 100 is driven with the low load function exemplified in Fig. 3 activated, ie. the pressure P of the air supplied to the combustion is maintained at a higher pressure for a first time after the torque request has decreased. In step 203, therefore, a setpoint Pnn is set for the combustion air pressure P equal to P2, i.e., the engine control will aim to maintain the combustion air pressure P at the level Pg prevailing the internal torque demand decreased at t1. At the same time, a timer is started after first being set to 0, after which the procedure proceeds to step 204. In step 204 it is determined whether the timer tt has reached the time limit tina, when the time limit tina constitutes the time limit for said low load function, which as above can be 1-3 seconds. As long as the time limit thaw has not been reached, the process remains in step 204 so that, when the time limit thaw has been reached, proceeding to step 205.

In step 205, it is determined whether the vehicle's 100-degree braking system has applied the brakes:;: tm years activated.f »4» fï- «J ~ f-- ~ x'x" - «“ m »vf -'- F. 4 ~ l fi f M \ /. n JaJáur \, k. LJ _, -vv JÅJII., J.¿L, LL _L ~ _L \, 1 _ \, \, <. ~ __, x. f »» I x 14 »x 1 , - fl g 4 J. .n .L, v. ~ JZ \ L KLL A. ._ »_, .A_, y, \« J. KL »_ -_ bl 4 Rix / j 1 v,. , c- KL xx - ~ - xxvxx vv ”x ~ x Y l LJ / LL .PJ J Ü, f J 1 4. J JJ 1. / Líx ._ 4. l AL x) y L x“ ““ * u ”t'g ^ t, * o ^" t "" ^ “¿t 0m it in step 205 is determined that \ va, x_4 v -_. LL _, -_. 1:11 .. -_ ».._- ~. -_. j .. J. _, _-_. L o I H so not the case, ie. driving brake system 16 LV, ~ f I www-f ~ fïf -F ~ -, 'Ä. - \ 'Iw' ~ «« f 11% .- .. \ ,. L. v. LJ-.LJ-.LLLL-o fl v .v_r_a..J __ ..! o .. ._.-_ ». V .... L. \, otherwise ciru-activated, the procedure proceeds to step 206 the low pressure setpoint Pn fi for the combustion air pressure P at the control of the combustion engine 101 is set to the pressure P1 currently required, which e.g. can be the atmospheric pressure if the driving force requirement is low, and / or the pressure required to have the lowest air / fuel ratio As allowed by e.g. prevailing government regulations and / ellert.ex. from the point of view of smoke restriction shall not be less than.

The procedure then returns to step 201. Ie. in the event that the iegee service braking system is not activated, the engine management functions exactly as in the case the vehicle 100 is driven with activated low load function.

If in step 205 on the other hand it is determined that now. -. . '..._. When the brake system is activated, the process proceeds to step 207, when the pressure set PH; for the combustion air pressure P Continued is maintained at the pressure that prevailed within the reduction of the requested driving force, ie. in the present example pressure P2. Pressure exchange PH; however, it is not necessary to set the pressure P2, but can also constitute another applicable, but still compared with the pressure P1 higher, pressure, such as e.g. 70-100% of the pressure P2.

The combustion air pressure P is thus maintained after the time t2 continued at a high level with larger combustion engine losses due to greater gas exchange work as above as a result.

This is illustrated in Fig. 4, when also the braking torque L of the engine is illustrated, when L2 represents the total combustion engine losses at a combustion air pressure P2 according to above, when L1 represents the total combustion engine losses at a reduction of the combustion A1 and the loss of combustion caused by losses due to the larger gas exchange work at the combustion air pressure P2. These engine losses due to the intermittent gas exchange work can e.g. constitute a braking torque in the order of magnitude of 50-100 newton meters, ie. engine loss increases with this care at a high maintained combustion air pressure. The difference with respect to Fig. 3 is illustrated in Fig. 4 by indicating the pressure change according to Fig. 3 with a dashed line 401, which thus takes place already at the time in Fig. 3. Likewise, a dashed line 402 indicates the correspondingly lower losses in gas exchange work which occur in Figs. 3 previously the reduction of the combustion air pressure.

However, since the combustion air pressure according to the present invention is maintained when the service brake system is activated, the increased engine losses can be compensated by a reduction of the applied braking torque, i.e. the brakes can operate to a correspondingly lesser degree, thus keeping the total losses regarding engine losses and the brake force loss constant at a constant level. Thus, according to the present invention, the high combustion air pressure can be maintained without any actual cost in the form of e.g. increased fuel consumption.

This has the advantage that in cases where the vehicle 100 is to be rapidly accelerated after braking, a large proportion or all of the power (torque) the combustion engine 101 can generate will be substantially immediately available without otherwise inevitable delay occurring when the combustion air pressure must first be built up before full torque can be delivered by the internal combustion engine.

The present invention also has the advantage that since the brakes can operate to a correspondingly lesser extent, a reduced brake system wear is obtained, e.g. with respect to brake pads or other 18 components present in the vehicle's braking system. However, the reduced torque demand will usually mean that the combustion air pressure will not be able to be maintained for any length of time. For this reason, it is determined in step 208 whether the prevailing combustion air pressure exceeds any applicable limit value. This limit value Ping can be set to any applicable limit value, such as e.g. a value representing a level because the combustion air pressure has decreased to some applicable pressure due to the fact that the pressure can no longer be maintained, which often occurs when the reduced combustion engine work results in a reduced driving force (exhaust flow) for driving the turbocharger. The limit value Pnmzkan e.g. represent the atmospheric pressure, or a pressure level in the vicinity thereof. The limit value Ping can e.g. also consist of the pressure currently required at the rescue propulsion request, or an applicable pressure between the required combustion air pressure at the rescue propulsion request and the pressure P2. Furthermore, the pressure setpoint Pnn can be arranged to change with time when the braking system is activated, and e.g. the back pressure Pi is lowered or the limit value Ping is lowered in some applicable way.

When the combustion air pressure is below the limit value Pnmm which is shown at time tg in Fig. 4, the process repeats step 201 via step 206 as above, while as long as the combustion air pressure exceeds said limit Ping repeats the process to step 205 to determine whether any brake and brake system is still active. In this case, the combustion air pressure P is maintained in as many cases as possible. If it is then determined in step 205 that the braking system is no longer activated, the procedure returns directly to step 201 via step 206 as above. The invention thus enables maximum drivability to be maintained for as long as possible without causing increased losses.

Furthermore, the criterion exemplified in step 207, instead of being controlled by the pressure to which the combustion air pressure P has decreased, can instead be controlled by a second timer, this second timer occurring at a time which, compared with time thaw, causes the combustion air pressure to be maintained for a time. thaw for a long time. This second timer can e.g. be arranged to be started at the same time as the timer tm and thereby run into a compared with time thaw longer time.

The said second time can alternatively e.g. is triggered from the aforementioned braking system is activated, whereby the second timer can run at a time which can be both longer and shorter compared to the time thaw, but then the total time will exceed the time thaw. Transition from step 205 or step 207 to step 206 can thus according to one embodiment be arranged to take place when the second timer has reached a certain time, regardless of whether the braking system is still active, and regardless of whether the re-combustion air pressure P has not yet decreased to the Piimz level.

The method shown in Fig. 2 can be arranged to be carried out as soon as a reduction of the torque requested takes place. Alternatively, the method can be arranged only at a larger reduction of the torque committed, such as e.g. only provided that the reduced torque demand constitutes a maximum of 80% of the torque demand before reduction.

According to the method shown in Fig. 2, the vehicle is driven with the low load function according to Fig. 3 activated. There are dock situations where it can be advantageous to have the front vehicle without such a low load function activated. An example of this is shown in the parallel Swedish application 1250775-2, entitled "PROCEDURES AND SYSTEMS FOR DRIVING VEHICLES II", with the same applicant as the present invention, where the vehicle can be driven according to a first mode and according to a second mode, and then in the said other mode functions such as the said low-load function are deactivated when deemed appropriate in order to reduce fuel consumption. However, the present invention is still applicable even to e.g. situations as described according to the method described in the said parallel patent application, or generally when low load function is lacking.

An example of a method according to the present invention in such situations is shown in Fig. 5. The method steps 501-502 shown in Fig. 5 correspond entirely to the method steps 201-202 in Fig. 2 and are therefore not explained in more detail. According to the method shown in Fig. 5, however, retention of the combustion air pressure P is normally applied, which may be the case, for example, if such a function is completely absent, or the vehicle is driven according to said second mode according to the said parallel application "PROCEDURE AND SYSTEM OF PREPARING" .

Thus, it is already determined in step 503 whether any braking system is activated. If not, the proceeding proceeds to step 504, which corresponds to step 206 in Fig. 2, i.e. stock exchange PH; for the combustion air pressure P is set directly after the reduction of the torque demand in step 502 to the combustion air pressure required at the new torque level. According to this embodiment, the drivability of the vehicle is thus directly affected by a reduction in torque requested as long as no braking system is activated.

If, on the other hand, it is determined in step 503 that some braking system has been activated, the procedure proceeds to step 505, which corresponds to step 207 in Fig. 2 and wherein the combustion air pressure P via steps 505-506 is then maintained as long as possible according to the weather described in connection with steps 207-208 in fig. 2. Since the present invention does not give rise to increased fuel consumption when any braking system is activated, the invention thus allows the vehicle's driveability to be maintained at a high level in many situations without giving rise to increased fuel consumption, and thus in many situations good driving ability is possible. the attachment of the vehicle is actually driven in a way that prioritises low fuel consumption before good driveability.

As will be appreciated, the present invention is not limited to the above-described embodiments of the invention, except for and embodied embodiments within the scope of the appended independent claims.

For example. know the method with its method steps other than end embodiments within the scope of the present invention. For example, if the method is similar to the type shown in Fig. 6, therefore the step steps 601-602 are also completely corresponded to the method steps 201-202 in Fig. 2.

Instead of, as in Fig. 2, directly starting the timer, Fig. 6 already determines in step 603 whether the braking system is active. If the trap continues in the process of steps 604-605, which is also counteracted by steps 207-208 in Fig. 2, the combustion air pressure P is maintained for as long as possible. In addition, the above-described embodiment with the said change timer is also applied here.

If in step 603 it is ascertained that the braking system is not active, the procedure proceeds to step 606, where the said timer is set to zero and is started according to the enemy. At the same time, just as in step 203, the setpoint Pn fi for the combustion air pressure Plikä is set to P2, after which the method proceeds to step 607, whereby the timer tt is set to the time limit tina, where the time limit timu is also the time limit for the above function 22. Once the time limit has been reached, the process proceeds to step 608, where it is still determined whether any applicable braking system is activated. If not, the process returns to step 601 via step 608 where the pressure setpoint PH; for the combustion air pressure P set the pressure P1 currently required. If, on the other hand, it is found that the applicable braking system is activated, the process proceeds to step 604 for retaining the combustion air pressure as previously described.

Claims (1)

A method of driving a vehicle (100), said vehicle (100) comprising an internal combustion engine (101) having at least one combustion chamber, said vehicle (100) further comprising means for pressurizing exhaust air for supply to said combustion chamber, and wherein said vehicle (100 ) further comprising at least one first braking system, characterized in that the method comprises: - in reducing a torque request from a second level to a first, compared to said second level lower, level, determining whether said first braking system is activated, and - if said first braking system is activated, maintaining the pressure of said air supplied to said combustion chamber at an combustion chamber at a first pressure (P1) required at said first level, higher second pressure (Py. Method according to claim 1, said method further comprising: - if said first braking system is activated, the maintenance pressure of said to said fëfbfä flfl i fl gförbrä air supplied to said second pressure (P2), and if said braking system is not activated, the set pressure of said air supplied to said combustion chamber to a pressure substantially equal to said first pressure (P fl). A method according to claim 1, wherein said method comprises: - if said first braking system is activated, maintaining the pressure of said air supplied to said 24 êëæbæä flfl in combustion chamber at said second pressure (P2) for a second time, and - if said braking system is not activated, maintained for the air supplied to said combustion chamber in said combustion chamber at said second pressure (P2) for a first, compared with said second time shorter, time. The method of claim 3, further comprising activating said first braking system during said first time, maintaining the pressure of said air supplied to said combustion chamber in the combustion chamber substantially at said second pressure (P2) during said second time. A method according to claim 4, wherein, if said first brake system is activated during said first time, the pressure of said air supplied to said combustion chamber air is maintained substantially at said second pressure (P2) during said second time, said second time being counted from the time said first time. from the activation of said braking system. A method according to any one of claims 1-5, further comprising maintaining a pressure setpoint (Pmf) of the pre-pressure of said air supplied to said combustion chamber at said second pressure (P2) as long as said first braking system is activated. A method according to any one of the preceding claims, further comprising, when said first braking system is activated, maintaining a pressure setpoint (Pæf) of the pre-pressure of said air supplied to said êërërän fl i för combustion chamber at a higher pressure compared to said first pressure (P1) as long as the pressure of said Air supplied to the combustion chamber exceeding a limit value exceeds a limit value (P fi m fi. A method according to any one of claims 1-7, further comprising: - determining whether the braking force applied by said first brake system exceeds a first braking force, and - maintaining a pressure setpoint (Pæ); A method according to claim 8, wherein said first braking force corresponds to at least half the difference between the difference between said first brake (P1) and higher air supply at a higher pressure compared to said first pressure (P1) if the braking force applied by said first braking system exceeds said first braking force. gas exchange work pressurizing said combustion air to said second pressure (P2) and performing gas exchange work pressurizing said combustion air to said first pressure (P fl. A method according to any one of the preceding claims, wherein said first braking system consists of a service braking system. A method according to any one of the preceding claims, wherein delivering the required torque at said second level requires a second, compared to an air pressure required at said first level, higher air pressure. A method according to any one of the preceding claims, wherein said second pressure (P2) constitutes 70-100% of the required torque for emitting averaged torque at said second level for the air supplied to the combustion chamber. 13. 14. 15. 16. 17. 26 A method according to any one of the preceding claims, further comprising maintaining the pressure of said said combustion chamber luft in combustion chamber supplied air at said second pressure (P2) if said first braking system is activated, and if at said first level the required torque is 0-80% of the torque required at said second level. Method according to any one of the preceding claims, wherein said first pressure consists of a pressure which essentially results in an air / fuel ratio constituting a limit value permitted by the manufacturer or authority regulation when driving said vehicle. Computer program comprising program code, which when said program code is executed in a computer causes said computer to perform the method according to any one of claims 1-14. A computer program product comprising a computer readable medium and a computer program according to claim 15, wherein said computer program is included in said computer readable medium. A system for driving a vehicle (100), said vehicle (100) comprising an internal combustion engine (101) with at least one combustion chamber, said vehicle (100) further comprising means for pressurizing air supply to said combustion chamber, and said vehicle (100) further comprises at least one first braking system, characterized in that the system comprises: - means for determining when a torque request from a second level to a first, compared to said second level lower, level, whether said first braking system is activated, and - means for, if said first braking system is activated, maintaining the pressure of the air supplied to said combustion chamber at an air combustion chamber at a first pressure (P1) required at said first level, higher second pressure (Py. 18. Vehicle, characterized in that it comprises a system according to claim 17.