Restarting method and restarting assembly for starting an internal combustion engine of a motor vehicle

Abstract

The invention relates to a restarting method for automatically starting an internal combustion engine (2) of a motor vehicle (3) by means of a brake pedal actuation, comprising the following steps: detecting a brake pressure (p) by means of a brake pressure sensor (14); emitting a corresponding brake pressure signal sequence to a control device (13); determining a brake pressure profile (p.sub.pr) from the brake pressure signal sequence; determining a reference pressure value (p.sub.R) from the brake pressure profile; detecting a brake release status, wherein, with the release of a brake pedal, a brake pressure decrease (Δp) is detected based on the determined reference pressure value (p.sub.R), with said decrease exceeding a pressure decrease limit value (Δp.sub.G); emitting a starting signal (S.sub.WS) to a starter (15) for starting the internal combustion engine (2), if the brake release status has been detected. The invention also relates to a restarting assembly for a motor vehicle (1) for carrying out a method of this type.

Claims

1. A restarting method for automatically starting an internal combustion engine of a motor vehicle by a brake pedal actuation, comprising: recording a plurality of brake pressures by a brake pressure sensor; outputting an associated brake pressure signal sequence to a control unit; defining a first brake pressure profile from the brake pressure signal sequence; determining at least one reference pressure value from the first brake pressure profile; wherein the at least one reference pressure value includes a first reference pressure value for a first period of time, wherein the first reference pressure value is the highest brake pressure of the plurality of recorded brake pressures of the first brake pressure profile; recording a brake release status in response to a brake pressure drop being recorded that exceeds a pressure drop limit value using the determined at least one reference pressure value as a baseline; and sending a start signal to a starter for starting the internal combustion engine in response to the brake release status being recorded.

2. The restarting method as recited in claim 1, further comprising determining a second reference pressure value as a function of a second profile section of the determined first brake pressure profile corresponding to a second period of time.

3. The restarting method as recited in claim 1, further comprising determining the at least one reference pressure value as a function of a plurality of start-stop cycles within an operating cycle by evaluating each of a plurality of brake pressure profiles of the plurality of start-stop cycles, wherein the first brake pressure profile corresponds to one of the plurality of start-stop cycles.

4. The restarting method as recited in claim 1, wherein the pressure drop limit value is defined as a proportional deviation from the determined at least one reference pressure value, or the pressure drop limit value is linearly modified in response to the determined at least one reference pressure value.

5. The restarting method as recited in claim 1, wherein the pressure drop limit value is defined as a function of adjustable shifting characteristics of an automatic transmission.

6. The restarting method as recited in claim 1, wherein the pressure drop limit value is defined as a function of a driver type classification of a particular driver.

7. The restarting method as recited in claim 1, wherein the start signal is sent in response to at least one of the following conditions being met: the brake release status was recorded; the brake pressure undershoots a lower threshold; and a master brake switch is actuated in response to the brake being released.

8. The restarting method as recited in claim 1, the outputting of the brake pressure signal sequence being able to be optionally enabled or disabled.

9. The restarting method as recited in claim 1, further comprising disabling the sending of the start signal in response to at least one of the following statuses being sensed by a switch and/or a sensor: a vehicle door, a luggage-compartment lid and/or an engine hood are open; there is an accident situation; a lower voltage limit in the electrical system is undershot; and a parking brake is applied.

10. A restarting assembly for a motor vehicle, comprising a hydraulic brake system, a brake pressure sensor, a starter, and a control unit, the control unit being in a communication connection with the starter and the brake pressure sensor, and the control unit including a restarting algorithm as an executable program configured to implement the restarting method according to claim 1.

11. The restarting assembly as recited in claim 9, further having a switch that can be used to optionally enable or disable the restarting method.

12. The restarting assembly as recited in claim 11, wherein the switch is actuatable by a transmission selector lever or being configured thereon.

13. A vehicle comprising a restarting assembly according to claim 10.

14. The restarting method of claim 2, wherein a first profile section corresponding to the first period of time is a section of the first brake pressure profile which includes the highest brake pressure of the plurality of recorded brake pressures, the method further comprising: detecting a first transition of the first brake pressure profile from the second profile section to the first profile section, or from the first profile section to the second profile section, and setting the second reference pressure value to the brake pressure at the detected first transition of the first brake pressure profile.

15. The restarting method of claim 14, wherein: the first profile section has a plateauing slope in comparison to the second profile section; and the second profile section is a section of the first brake pressure profile with a rising slope before the first period of time or a descending slope after the first period of time.

16. The restarting method of claim 15, wherein the second profile section is the section of the first brake pressure profile with the rising slope before the first period of time, and the first brake pressure profile has a third profile section which is the section of the first brake pressure profile with the descending slope after the first period of time, the method further comprising: detecting a second transition of the first brake pressure profile from the first profile section to the third profile section; and setting a third reference pressure value to the brake pressure at the detected second transition.

17. The restarting method of claim 1, wherein the pressure drop limit has a first value which is a difference between the first reference pressure value and a predefined pressure value, and a first brake release status is recorded if the break pressure drop exceeds the first value of the pressure drop limit.

18. The restarting method of claim 2, wherein the pressure drop limit has a first value which is a difference between the first reference pressure value and a predefined pressure value, the pressure drop limit has a second value which is a difference between the second reference pressure value and the predefined pressure value, and the first value of the pressure drop limit is greater than the second value of the pressure drop limit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of present invention will be described exemplarily below and with reference to the attached drawing, in which:

(2) FIG. 1 is a schematic general depiction of a vehicle configuration that may be used to execute the restarting method according to the present invention, respectively that includes a restarting assembly according to the present invention.

(3) FIG. 2 is a functional diagram showing the essential components of an exemplary embodiment of a method according to the present invention.

(4) FIG. 3 is a brake pressure time diagram in which aspects of a method according to the present invention will become apparent; and

(5) FIG. 4 is a brake pressure time diagram clarifying the difference from a related art method; and

(6) FIG. 5 is a brake pressure time diagram illustrating a known restarting method/start-stop method.

(7) The basic function of the restarting method according to the present invention and the requisite components are first clarified with reference to FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(8) The general depiction in FIG. 1 schematically shows a motor vehicle 1 having an internal combustion engine 2 that drives wheels 3. Wheels 4 are shown here as non-driven wheels. In other specific embodiments, however, they may likewise be driven. All of wheels 3, 4 have hydraulically actuatable brakes 5 that are part of a hydraulic brake system, where brakes 5 are actuated via brake pedal 6, a brake booster 7, a brake master cylinder 8, a hydraulic power unit 9 having a hydraulic pump 10, and via brake lines 11.

(9) The actuation of brake pedal 6 is sensed by a switch 12, for example, that communicates via a signal line 17 with a control unit 13. A brake pressure sensor 14 records the brake pressure that has built up in brake lines 11 and/or in brake booster 7. It supplies brake pressure data indicative thereof to control unit 13, likewise via a signal line 17.

(10) Internal combustion engine 2 is started, as needed, via an electrical starter 15 that likewise communicates via a signal line 17 with control unit 13 and, from there, receives a start signal, if indicated. The electrical starter may be configured as a starter generator, for example, that is integrated on the crankshaft (ISG) or is coupled via a belt drive (RSG) to the engine. It may also be an electrical drive engine in the case of a hybrid drive concept.

(11) In addition, a bus system 16 (for example, a CAN bus system) may be provided via which the communication and signal transmission are realized among various electrical and electronic units in motor vehicle 1. This includes the internal combustion engine itself, for example, switch 12, brake pressure sensor 14, electrical starter 15, and hydraulic pump 10. Other sensors 19 and function switches 18 are likewise connected via signal lines 17 to control unit 13 and, there, may control the restarting functions described in the following.

(12) Signal lines 17 are shown in FIG. 1 as solid lines, and hydraulic or pressure lines 11 as dashed lines.

(13) In the case of the system described above, a start-stop functionality is realized in the following manner A brake pressure p is recorded by brake pressure sensor 14. It sends brake pressure signals indicative thereof to control unit 13. Alternatively and/or additionally, an actuation of the brake pedal may also be signaled via switch 12 to control unit 13.

(14) In response to the build-up of a defined brake pressure, control unit 13 transmits a stop signal to the engine.

(15) Upon the occurrence of a restarting condition, control unit 13 sends a restart signal S.sub.WS to electrical starter 15, which then restarts internal combustion engine 2.

(16) The functional sequence of the method according to the present invention will now be explained with reference to FIG. 2. In this regard, a restarting algorithm having a plurality of functional blocks is retrievable in control unit 13. It is provided in control unit (13) as an executable program that may be used to implement the restarting method.

(17) The brake pressure signals from brake pressure sensor 14, that represent brake pressure p, propagate into a first functional block 101, where they are further processed into a brake force profile p.sub.Pr (in this regard, see also FIG. 3-5).

(18) In a second functional block 102, a reference pressure value p.sub.R is determined from this brake force profile p.sub.Pr. In a third functional block 103, a pressure drop limit value Δp.sub.G is determined. And, in a fourth functional block 104, a brake release status is recorded when, upon releasing the brake pedal, using determined reference pressure value p.sub.R as a baseline, a brake pressure drop Δp is recorded that undershoots pressure drop limit value Δp.sub.G. This case occurs in response to (absolute) brake pressure p recorded by brake pressure sensor 14 undershooting the differential between reference pressure value p.sub.R and pressure drop limit value Δp.sub.G. In a fifth functional block 105, restart signal S.sub.WS is then sent to starter 15, and internal combustion engine 2 is started again.

(19) It will be explained below with reference to FIG. 3, how reference pressure value p.sub.R and pressure drop limit value Δp.sub.G are defined. Various approaches are possible. However, they follow from the same basic principle.

(20) In a first exemplary embodiment, maximum brake pressure p.sub.Max is determined on the basis of brake pressure profile p.sub.Pr and specified as reference pressure value p.sub.R. Using maximum brake pressure p.sub.Max as a baseline, the restarting condition is then specified as the pressure drop being a defined Δp in order for restart signal S.sub.WS to be sent and for stop phase t.sub.St between t.sub.0 and t.sub.1 to be ended (hatched surface area in the diagram). It is thus ensured that the restart signal is generated independently of actually reached maximum brake pressure p.sub.Max always in response to same brake pressure drop Δp. It is, thus, possible to realize a restarting condition that is perceived as being responsive, rapid and consistent.

(21) Alternative exemplary embodiments provide that reference pressure value p.sub.R may also be specified in a different manner, for example, by analyzing various phases/sections of the brake pressure profile. In this regard, FIG. 3 shows a profile section I in which the transition from a rising phase into a plateau phase is detected. This value p.sub.RI may then be specified as reference pressure value p.sub.R.

(22) In another exemplary embodiment, a falling phase (section III in FIG. 3) is considered, where the transition from the plateau phase into the falling phase is determined as p.sub.RIII, and this value is specified as reference pressure value p.sub.R.

(23) It is also possible to only evaluate the plateau phase (section II) and, there, to calculate an average maximum value as p.sub.RII, for example, which is then to be used as reference pressure value p.sub.R.

(24) Similarly, there are exemplary embodiments where pressure drop limit value Δp.sub.G is also variably determined as a function of brake pressure profile p.sub.Pr or in a different manner.

(25) It is also possible to define reference pressure value p.sub.R and pressure drop limit value Δp.sub.G from a plurality of determined brake force profiles p.sub.Pr that are defined during a drive of a specific driver, for example.

(26) Thus, it may be in a proportional relationship with reference pressure value p.sub.R, for example. It may also be provided, however, that pressure drop limit value Δp.sub.G varies progressively, degressively or also linearly with reference pressure value p.sub.R and especially with a corresponding maximum brake pressure p.sub.Max. This is indicated in FIG. 3 by designations Δp.sub.GI′ through Δp.sub.GIII.

(27) Other conditions may be realized as a function of sixth and seventh functional blocks 106, 107 depicted in FIG. 2. For example, functional block 106 may define pressure drop limit value Δp.sub.G as a function of what is referred to as a driver type classification or also, alternatively, as a function of the shifting characteristics of an automatic transmission. The tendency for driving in a more or less “sporty” fashion is considered in this manner. It may be thereby assumed, for example, that pressure drop limit value Δp.sub.G is reduced in response to sporty shifting characteristics or a sporty driver type classification, so that an earlier restarting of internal combustion engine 2 follows.

(28) Via seventh functional block 107, other conditions for sending restart signal S.sub.WS may also be taken into consideration. They may be considered as AND and/or as OR conditions. For example, this may be the additional consideration of an undershooting of a lower brake pressure threshold value p.sub.SU, where a restart signal is to be sent.

(29) Or restart signal S.sub.WS is triggered or blocked by one or more switches 18 or sensors 19. This may be realized by recording defined positions of vehicle components, such as vehicle doors, luggage-compartment lids and the engine hood, by recognizing accident situations, a lower voltage limit in the electrical system is undershot or it is signaled, for example, that a parking brake is applied, and, in such cases, a restart signal S.sub.WS is sent by actuation of brake pedal 6.

(30) FIG. 4 shows the distinction from a conventional restarting request, as is described with reference to FIG. 5. The stop phase is ended in accordance with the present invention following a time period Δt.sub.1 using maximum pressure value p.sub.Max as a baseline that is recorded via brake profile p.sub.Pr and is specified as reference pressure value p.sub.R, and a specified or differently determined pressure drop limit value Δp.sub.G. Δt.sub.1 is the time period between points in time t.sub.0 and t.sub.1.

(31) In accordance with the conventional method, the stop phase only ends after an appreciably longer period of time Δt.sub.2 that is between points in time t.sub.0 and t.sub.2. Thus, a more rapid and, consequently, more responsive restarting or also earlier restarting is possible. In the method according to the present invention, the driver perceives an immediate reaction (better response behavior) to the releasing of the brake. This response behavior may be further optimized or customized by defining reference pressure value p.sub.R and pressure drop limit value Δp.sub.G.

LIST OF REFERENCE NUMERALS

(32) 1 motor vehicle 2 internal combustion engine 3 wheels 4 wheels 5 brakes 6 brake pedal 7 brake booster 8 brake master cylinder 9 hydraulic power unit 10 hydraulic pump 11 brake line 12 switch 13 control unit 14 brake pressure sensor 15 electrical starter 16 bus system 17 signal line 18 switch 19 sensor p brake pressure t time p.sub.SU lower threshold value p.sub.SS stop threshold value Δp.sub.Fix fixed pressure difference p.sub.Pr brake force profile p.sub.R reference pressure value p.sub.Max maximum braking force Δp brake pressure drop Δp.sub.G pressure drop limit value t.sub.St engine stop time t.sub.0, t.sub.1, t.sub.2 points in time S.sub.WS restart signal I-III brake force profile sections 101 first functional block 102 second functional block 103 third functional block 104 fourth functional block 105 fifth functional block 106 sixth functional block 107 seventh functional block