Restart procedure and restart arrangement for starting an internal combustion engine of a motor vehicle

Abstract

Restart procedure for automatically starting an internal combustion engine (2) of a motor vehicle (3) by means of a brake pedal actuation with: Detecting a brake pressure (p) using a brake pressure sensor (14), Output of a corresponding brake pressure signal sequence to a control unit (13), Determining a brake pressure profile (p Pr ) from the brake pressure signal sequence, Determining a reference pressure value (p R ) from the brake pressure profile, Detecting a brake release state when releasing a brake pedal from the determined reference pressure value (p R ) a brake pressure drop (Δp) is detected, which has a pressure drop limit value (Δp) G ) exceeds, and Issuing a start signal (S WS ) to a starter (15) for starting the internal combustion engine (2) when the brake release state has been detected, characterized in that the pressure drop limit (Δp G) depending on the determined reference pressure value (p R ) and / or from the determined brake pressure profile (p Pr ) can be determined.

Description

[0001] The invention relates to a restart method and a restart arrangement for starting an internal combustion engine of a motor vehicle. The invention also relates to a vehicle with a restart arrangement.

[0002] Such methods and arrangements are now widespread within the framework of start-stop functionality. Start-stop systems allow the combustion engine to be temporarily switched off during stationary phases without the driver having to manually operate the accelerator. At the end of such a standstill phase, the switched-off combustion engine is automatically restarted as soon as the driver wants to continue driving. Restarting also occurs without manual operation of the accelerator.

[0003] Several methods and corresponding devices for restarting a vehicle have already been implemented. In one method according to EP 1 063 424 B1, the restart process is initiated based on the position of the brake pedal, which is detected by suitable sensors. When the brake pedal is released from its engaged position (brake position), the vehicle's internal combustion engine is started when the brake pedal returns to its initial position. The starting process is triggered by detecting a specific intermediate position of the brake pedal as it returns to its initial position.

[0004] A pressure-controlled method is known from EP 1 548 864 B1. Here, the time course of the brake pressure when the brake pedal is released is evaluated, and the restart process is triggered based on a negative brake pressure gradient. The brake pressure gradient must exceed a threshold value for the control electronics in a control unit to initiate the restart process as part of a start-stop function. With this solution, it can happen that the threshold value is not reached if the brake is released very slowly, so additional measures are required to initiate the restart.

[0005] For example, an additional lower threshold p can be added. SU The brake pressure is taken into account, at which point the restart process is initiated. This relationship is derived from the Fig. 5 recognizable in which a braking force profile p Pr(Braking force p over time t) is represented. The stopping phase begins when a stopping threshold p is exceeded. SS and ends when the aforementioned lower threshold p is not reached. SU , at which the restart is triggered. The value p is... SU to achieve a fixed pressure difference Δp Fix below the value p SS .

[0006] Especially in conjunction with the gradient method, where the restart process is not triggered due to an insufficient braking gradient, but only when the lower pressure threshold p is undershot. SU , such a restart may be perceived as delayed.

[0007] DE 10 2013 216 622 A1 discloses a restart method according to the preamble of claim 1.

[0008] The task is to provide a restart procedure or restart device that ensures sensitive start-stop functionality.

[0009] This problem is solved by the inventive method according to claim 1 and by the restart arrangement according to claim 10. A vehicle with such a restart arrangement is the subject of claim 13.

[0010] Further advantageous embodiments of the invention will become apparent from the dependent claims and the following description of preferred embodiments of the present invention.

[0011] The restart method according to the invention for the independent starting of an internal combustion engine of a motor vehicle by means of a brake pedal actuation is characterized by the following: First, the brake pressure is measured by a brake pressure sensor, and the corresponding brake pressure signal sequence is sent to a control unit, such as an engine control unit (ECU). Based on this brake pressure signal sequence, a brake pressure profile is determined, from which a reference pressure value is calculated. This reference pressure value serves as a (variable) output value for detecting the brake release state. This means that the stop phase of a start-stop system is not terminated based on fixed, preset brake pressure thresholds, but rather based on the determined reference pressure value.

[0012] The brake release state is detected when, upon releasing the brake pedal, a brake pressure drop is detected from the determined reference pressure value (variable) that exceeds a pressure drop limit, i.e., a specific (but potentially variable) deviation from the reference pressure value. The start signal to a starter for starting an internal combustion engine is then sent when this brake release state has been detected.

[0013] According to the invention, the pressure drop limit can be determined as a function of the determined reference pressure value. It can, for example, be determined as a percentage deviation from the reference pressure value. This allows, for instance, the pressure drop limit to be increased or decreased in the same way at very high maximum brake pressures in order to detect the brake release state.

[0014] With the inventive method described above, it is possible to derive a sensitive and, if necessary, driver-specific restart condition based on individual braking behavior – by determining an individual reference pressure value from an actual brake pressure profile – and this restart condition is determined on the basis of a variable brake release state. This noticeably improves the restart behavior for the driver by ensuring that it always feels "the same," even if tailored to the individual driver. The restart behavior is thus optimized.

[0015] There are versions where the reference pressure value can be determined depending on a profile section of the calculated brake pressure profile. Typically, a brake pressure profile during a start-stop phase – which is actually a stop-start phase – has a hat-like shape (see...). Fig. 3-5). This means that initially there is a relatively steep increase in brake pressure, which is kept largely constant on a plateau during the stop phase, and then drops again shortly before restarting until the brake pressure is completely released. To influence the restart behavior, different sections of this profile can now be evaluated to determine a reference pressure value.

[0016] For example, it is possible to evaluate the ascent section and determine the reference pressure value in the transition phase from the ascent to the plateau phase.

[0017] Another possibility is to evaluate the profile of the plateau section in which the maximum brake pressures are maintained by calculating an average value from these signals.

[0018] Another possibility is to, for example, record the transition from the plateau section to the waste section and define a reference pressure value here.

[0019] Another variation can also consist of calculating the average of the transition values ​​from the rising section to the plateau section and from the plateau section to the falling section, thus determining the reference pressure value.

[0020] In one embodiment of the method, the reference pressure value is determined based on several start-stop cycles within an operating cycle (e.g., a specific driver's journey). This makes it possible to determine a driver-specific, preferred reference pressure value and define it as the starting point for determining the brake release state.

[0021] A particularly simple method for determining the reference pressure value is to determine the maximum brake pressure of a determined brake pressure profile and, starting from this, to record the brake release state.

[0022] In addition, there are also designs in which the pressure drop limit is variable and can be individually determined.

[0023] In other methods, the pressure drop limit can also be increased or decreased linearly, degressively or progressively with the reference pressure value.

[0024] The pressure drop limit can also be determined in other methods depending on the adjustable shift characteristics of an automatic transmission. For example, it is increased with an emissions-optimized shift and driving characteristic to allow for a later restart and a longer stop phase, while it is shortened with a sporty shift and driving characteristic to keep the stop phases as short as possible.

[0025] There are also methods where the pressure drop limit can be determined based on a driver type classification. Such driver type classifications are implemented in motor vehicles, for example, in adaptive automatic transmissions.

[0026] To further individualize the brake release behavior or improve the restart behavior, additional restart conditions can also be introduced for initiating the restart.

[0027] For example, a condition can be added that a lower threshold is undershot to trigger the restart function. This is useful, for instance, if determining the reference pressure value or the pressure drop limit is not possible or fails for any reason.

[0028] Furthermore, it is also possible to activate a master brake switch when releasing the brake, which can be combined, for example, with a manual transmission or with the selector lever of an automatic transmission. The stop state is ended, or the restart is triggered, for example, when the gear selector is moved from the park to a drive position, thereby initiating a start-up process.

[0029] There are also versions where the output of the brake pressure signal sequence can be switched on or off, and the restart process is triggered, for example, only due to a brake pedal position or when a lower pressure threshold is undershot.

[0030] There are further situations in which the restart procedure should be prevented for safety or other functional reasons. These include, for example, a situation where a vehicle door, trunk lid, and / or hood is open.

[0031] Another situation can arise, for example, when a sensor or detector registers an accident. This includes, for example, significantly increased acceleration values, the deployment of an airbag, or an unusual change in the vehicle's position from its normal position (skidding, rollover, etc.).

[0032] To protect a power source (deep discharge of a battery), a lower voltage limit can also be set in the vehicle electrical system, below which a restart process is not carried out.

[0033] The same applies, for example, if a parking brake is engaged at the same time and therefore a brake pressure-dependent restart request should be avoided.

[0034] Another aspect of the invention relates to a restart arrangement for a motor vehicle comprising a hydraulic braking system, a brake pressure sensor, a starter, and a control unit, wherein the control unit is in communication with the starter and the brake pressure sensor, and the control unit contains a restart algorithm as an executable program with which the restart method according to the invention can be carried out. With such a configuration, it is particularly easy to implement the method according to the invention in a vehicle by means of a purely programming measure, optionally also subsequently by means of a software update.

[0035] It is advisable to design the entire restart procedure to be selectable and switchable. In a particular embodiment, the switch can be operated, for example, via a gear selector lever or arranged as a separate switch in an easily accessible location on the lever.

[0036] A vehicle with such a restart arrangement can either have its start-stop behavior individually adapted to the driver or adapted to other boundary conditions (environmental protection / emissions / consumption, wear, etc.).

[0037] Exemplary embodiments of the invention will now be described by way of example and with reference to the accompanying drawing. The drawing shows: Fig. 1 a schematic overview of a vehicle configuration with which the restart method according to the invention can be carried out or which includes a restart arrangement according to the invention. Fig. 2 a functional diagram showing the essential components of an embodiment of a method according to the invention. Fig. 3 a brake pressure-time diagram in which aspects of a method according to the invention become clear; and Fig. 4. A brake pressure-time diagram illustrating the difference to a prior art method; and Fig. 5 a brake pressure time diagram, which represents a known restart procedure / start-stop procedure.

[0038] The basic function of the restart method according to the invention and the components required for it will first be explained using the following: Fig. 1 explained.

[0039] The overview in Fig. Figure 1 schematically shows a motor vehicle 1 with an internal combustion engine 2 that drives the wheels 3. The wheels 4 are not shown driven here, but can also be driven in other embodiments. All wheels 3, 4 have hydraulically actuated brakes 5, which are part of a hydraulic braking system in which the brakes 5 are actuated via the brake pedal 6, a brake pressure booster 7, a master brake cylinder 8, a hydraulic power unit 9 with a hydraulic pump 10 and brake lines 11.

[0040] The actuation of the brake pedal 6 is detected, for example, by a switch 12, which is connected to a control unit 13 via a signal line 17. The brake pressure built up in the brake lines 11 and / or in the brake pressure booster 7 is detected by a brake pressure sensor 14, which also supplies corresponding brake pressure data to the control unit 13 via a signal line 17.

[0041] The combustion engine 2 is started as needed by an electric starter 15, which is also connected to the control unit 13 via a signal line 17 and receives a start signal from there if necessary. The electric starter can, for example, be designed as a starter-generator integrated on the crankshaft (ISG) or coupled to the engine via a belt drive (BSG). It can also be an electric drive motor in a hybrid drive concept.

[0042] Furthermore, a bus system 16 (e.g., a CAN bus system) can be provided, through which communication and signal transmission between various electrical and electronic units in the motor vehicle 1 is realized. These include, for example, the combustion engine itself, the switch 12, the brake pressure sensor 14, the electric starter 15, and the hydraulic pump 10. Additional sensors 18 and function switches 19 are also connected to the control unit 13 via the signal lines 17 and can control the restart functions shown below.

[0043] Signal lines 17 are in Fig. 1 are shown as solid lines and hydraulic or pressure lines 11 as dashed lines.

[0044] The start-stop functionality is implemented in the system described above as follows. The brake pressure sensor 14 detects a brake pressure p, which sends corresponding brake pressure signals to the control unit 13. Alternatively and / or additionally, actuation of the brake pedal can also be signaled to the control unit 13 via the switch 12.

[0045] Once a certain brake pressure has been built up, the control unit 13 signals a stop signal to the engine.

[0046] When a restart condition occurs, control unit 13 sends a restart signal S WS to the electric starter 15, which then restarts the combustion engine 2.

[0047] Based on Fig. 2 The process of the method according to the invention will now be explained. In the control unit 13, a restart algorithm with several function blocks can be called up, which is available in the control unit (13) as an executable program with which the restart procedure can be carried out.

[0048] The brake pressure signals from the brake pressure sensor 14, which represent the brake pressure p, run into a first functional block 101, where they are converted into a brake force profile p Pr further processed (see also Fig. 3 - Fig. 5).

[0049] In a second functional block 102, p is derived from this braking force profile. Pr a reference pressure value p R Determined. In a third functional block 103, a pressure drop limit Δp is determined. G determined. And in a fourth functional block 104, a brake release state is recorded when, upon releasing the brake pedal, starting from the determined reference pressure value p RA brake pressure drop Δp is detected, which exceeds the pressure drop limit Δp. G This occurs when the (absolute) brake pressure p detected by brake pressure sensor 14 falls below the difference between the reference pressure value p and the actual brake pressure p. R and the pressure drop limit Δp G The threshold is not exceeded. Subsequently, the restart signal S is generated in a fifth functional block 105. WS Power is transferred to starter 15 and the combustion engine 2 is restarted.

[0050] Determining the reference pressure value p R and the pressure drop limit Δp G will now be based on the Fig. 3 explained. Different approaches are possible, but they all follow the same basic principle.

[0051] In a first embodiment, the brake pressure profile p is used as a basis. Pr the maximum brake pressure p Max determined and used as a reference pressure value p RThe restart condition is then defined as the pressure drop from the maximum brake pressure p. Max a certain Δp must be present for the restart signal S to be generated. WS is released and the stop phase t St The process ends between t0 and t1. This ensures that the braking force is not affected by the actual maximum braking pressure p reached. Max The restart signal is always generated at the same brake pressure drop Δp. This enables a sensitive, rapid, and consistently perceived restart condition.

[0052] In alternative embodiments, the reference pressure value p can be R can also be determined in other ways, e.g. by analyzing different phases / sections of the brake pressure profile. Fig. Figure 3 shows a profile section I, in which the transition from an ascending phase to a plateau phase is detected. This value p RI can then be used as the reference pressure value pR be determined.

[0053] In another embodiment, a descent phase (section III in Fig. 3) considered in which the transition from the plateau phase to the decline phase is viewed as p RIII is determined and this value is used as the reference pressure value p R is determined.

[0054] It is also possible to evaluate only the plateau phase (section II) and, for example, to calculate an average maximum value as p. RII to calculate, which then serves as the reference pressure value p R is intended to serve this purpose.

[0055] Similarly, there are embodiments in which the pressure drop limit Δp G also variable depending on the brake pressure profile p Pr or is determined in some other way.

[0056] It is also possible to change the reference pressure value p R and the pressure drop limit Δp G from several determined braking force profiles p Prto determine, for example, those determined during a journey by a particular driver.

[0057] For example, it can be expressed as a percentage in relation to the reference pressure value p. R stand. However, it can also be stipulated that the pressure drop limit Δp G progressive, degressive or linear with the reference pressure value p R and in particular with a corresponding maximum brake pressure p Max varies. In the Fig. 3 this is indicated by the designations Δp GI up to Δp GIII hinted at.

[0058] Further conditions can be found in the Fig. The sixth and seventh functional blocks 106 and 107 shown in Figure 2 can be implemented. For example, functional block 106 can determine the pressure drop limit Δp via a so-called driver type classification. GThis can be determined, or alternatively, via the shift characteristics of an automatic transmission. This takes into account, for example, the tendency to drive more or less "sportily." It can be assumed that, for example, with a sporty shift characteristic or a sporty driver type classification, the pressure drop limit Δp G is reduced, so that an earlier restart of the combustion engine 2 takes place.

[0059] Further conditions for the output of the restart signal S can also be specified via the seventh function block 107. WS These conditions must be considered and can be expressed as AND and / or OR conditions. For example, this could include the additional consideration of falling below a lower brake pressure threshold p. SU be the point at which a restart signal is to be issued.

[0060] Or the restart signal S WSis triggered or blocked via one or more switches 18 or sensors 19. This can be achieved by detecting certain positions of vehicle components such as vehicle doors, luggage compartment lids and the hood, by recognizing accident situations, by detecting that a lower voltage limit in the vehicle electrical system has been undershot, or by signaling that, for example, a parking brake is engaged, and in such cases by sending a restart signal S. WS This is prevented by the activation of the brake pedal 6.

[0061] The difference to a conventional restart request, as described by the Fig. As described in section 5 of the introduction, the Fig. 4. Starting from the braking profile p Pr recorded maximum braking value p Max , which serves as the reference pressure value p R is determined, and a specified or otherwise determined pressure drop limit Δp GAccording to the present invention, the stop phase ends after a period Δt1. Δt1 is the period between times t0 and t1.

[0062] In the conventional method, the stop phase ends only after a significantly longer period Δt2, which lies between times t0 and t2. This allows for a faster and therefore more sensitive restart, or even an earlier restart. With the method according to the invention, the driver experiences a more immediate reaction (better response behavior) to the release of the brake. This response behavior can be determined by measuring the reference pressure value p. R and the pressure drop limit Δp G further optimized or individualized. Reference symbol list 1 motor vehicle 2 Internal combustion engine 3 wheels 4 wheels 5 brakes 6 Brake pedal 7 Brake pressure booster 8 master brake cylinders 9 Hydraulic unit 10 Hydraulic pump 11 Brake line 12 switches 13 Control unit 14 Brake pressure sensor 15 electric starters 16 bus system 17 Signal line 18 switches 19 Sensor p Brake pressure t time p SU lower threshold p SS Stop threshold Δp Fix fixed pressure difference P Pr Braking force profile p R Reference pressure value p Max maximum braking force Δp brake pressure drop Δp G Pressure drop limit t St Engine stop time t0, t1, t2 Time points S WS Restart signal I - III Braking force profile sections 101 first function block 102 second function block 103 third functional block 104 fourth functional block 105 fifth functional block 106 sixth functional block 107 seventh function block

Claims

[1] Restart method for automatically starting an internal combustion engine (2) of a motor vehicle (3) by means of a brake pedal actuation with: Detecting a brake pressure (p) using a brake pressure sensor (14), Output of a corresponding brake pressure signal sequence to a control unit (13), Determining a brake pressure profile (p Pr ) from the brake pressure signal sequence, Determining a reference pressure value (p R ) from the brake pressure profile, Detecting a brake release state when releasing a brake pedal from the determined reference pressure value (p R ) a brake pressure drop (Δp) is detected, which has a pressure drop limit value (Δp) G ) exceeds, and Issuing a start signal (S WS ) to a starter (15) to start the internal combustion engine (2) when the brake release state has been detected, characterized by , that the pressure drop limit (Δp G) depending on the determined reference pressure value (p R ) and / or from the determined brake pressure profile (p Pr ) can be determined. [2] Restart method according to claim 1, characterized by , that the reference pressure value (p R ) depending on a profile section (I; II; III) of the determined brake pressure profile (p Pr ) can be determined. [3] Restart method according to claim 1 or 2, characterized by , that the reference pressure value (p R ) depending on several stopping cycles within an operating cycle by evaluating several brake pressure profiles (p Pr ) can be determined. [4] Restart method according to claim 1, 2 or 3, characterized by , that the reference pressure value (p R ) a maximum brake pressure (p Max ) of a determined brake pressure profile (p Pr ) is. [5] Restart method according to any one of claims 1 to 4, characterized by , that the pressure drop limit (Δp G) can be determined depending on an adjustable shift characteristic of an automatic transmission. [6] Restart method according to any one of claims 1 to 5, characterized by , that the pressure drop limit (Δp G ) depending on a driver type classification of the respective driver. [7] Restart method according to any one of the preceding claims, characterized by , that the start signal (S WS ) is submitted if at least one of the following conditions is met: The brake release state was recorded. The brake pressure falls below a lower threshold value (p SU ), When the brake is released, a main brake switch (8) is actuated. [8] Restart method according to any one of the preceding claims, characterized by , that the output of the brake pressure signal sequence can be optionally switched on or off. [9] Restart method according to any one of the preceding claims, characterized by , that the sending of the start signal (S WS ) is prevented if at least one of the following states is detected by means of a switch (18) and / or a sensor (19): a vehicle door, a trunk lid and / or a hood is open, an accident situation exists A lower voltage limit in the vehicle electrical system has been breached. The parking brake is engaged. [10] Restart arrangement for a motor vehicle (1) comprising a hydraulic brake system, a brake pressure sensor (14), a starter (15) and a control unit (13), wherein the control unit (13) is in communication connection (16; 17) with the starter (15) and the brake pressure sensor (14) and the control unit (13) contains a restart algorithm as an executable program with which the restart procedure according to one of the preceding claims can be carried out. [11] Restart arrangement according to claim 10 with a switch (18) by which the restart procedure can be selectively switched on or off. [12] Restart arrangement according to claim 11, characterized by , that the switch (18) can be operated via a gear selector lever or is arranged on it. [13] Vehicle with a restart arrangement according to any one of claims 10 to 12.

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