START-STOP AUTOMATIC FOR ONE ENGINE

Abstract

Start-stop automatic system (101) for an engine (102), comprising a detection device (105) for detecting a recurring work cycle (130) of a work vehicle (100) based on at least one operating parameter; and a switching control (107) for determining a switching-off time (172) of the engine (102) based on the operating parameter within the work cycle (130).

Description

[0001] The invention relates to an automatic start-stop system for an engine, a work vehicle with an automatic start-stop system and a start-stop method for an engine.

[0002] With conventional automatic start-stop systems, the engine is switched on when the load demand exceeds a certain threshold and switched off when the load demand falls below an engine-off threshold. Additionally, the time since the last engine start can also be taken into account. However, frequent engine shutdown and subsequent restart leads to high wear, high fuel consumption, and high emissions.

[0003] An unnecessary shutdown of the engine occurs, for example, when the load requirement falls below a certain threshold but is then immediately increased again.

[0004] The automatic start-stop system for an engine according to the invention comprises a detection device for detecting a repetitive work cycle of a work vehicle based on at least one operating parameter, and a switching controller for determining a switch-off point of the engine based on the operating parameter within the work cycle. The automatic start-stop system achieves the technical advantage that switch-off points can be more accurately determined and unnecessary engine shutdown is prevented. This can increase the service life of the engine and reduce fuel consumption and pollutant emissions.

[0005] In an advantageous embodiment of the automatic start-stop system, the switching control is configured to determine the engine's switch-on time based on the operating parameter. In this case, the operating parameter can be the same operating parameter used to determine the engine's switch-off time. However, one or more other operating parameters can also be used to determine the switch-on time. This achieves the technical advantage, for example, that switch-on times can also be determined more accurately, improving the engine's switch-on behavior.

[0006] In a further advantageous embodiment of the automatic start-stop system, the operating parameter is an engine speed and / or a direction of travel of the work vehicle and / or an idle state of the engine. This achieves the technical advantage, for example, of using operating parameters that allow repetitive work cycles to be particularly well recognized. The direction of travel can be used to determine the switch-off or switch-on time, for example, if long idle times are expected in the repetitive work cycle depending on the direction of travel.

[0007] In a further advantageous embodiment of the automatic start-stop system, the switching control is designed to determine the switch-off and / or switch-on time of the engine within the operating cycle when the operating parameter exceeds or falls below a predetermined threshold. This achieves the technical advantage, for example, that the switch-off and / or switch-on time can be determined in a simple manner.

[0008] In a further advantageous embodiment of the automatic start-stop system, the shift control is designed to predict a future operating profile based on the at least one detected operating parameter and / or to determine the engine switch-off and / or switch-on time using a predefined rule or an optimization of the operating parameter within the operating cycle. This achieves the technical advantage, for example, that the switch-off and / or switch-on time can be determined quickly and accurately.

[0009] In a further advantageous embodiment of the automatic start-stop system, the switching control is designed to specify a maximum of one engine switch-off and / or switch-on time within a working cycle. This achieves the technical advantage, for example, of preventing the engine from being switched off and on again multiple times unnecessarily during a working cycle.

[0010] In a further advantageous embodiment of the automatic start-stop system, the detection device is designed to compare a detected operating cycle with a pre-stored operating cycle or multiple pre-stored operating cycles in which the engine switch-off and / or switch-on time is determined. This achieves, for example, the technical advantage that the engine switch-off and / or switch-on time can be easily determined by comparing it with the pre-stored operating cycle.

[0011] In another advantageous embodiment of the automatic start-stop system, the work vehicle is a wheel loader or dump loader. This achieves the technical advantage of increasing the engine life of the wheel loader or dump loader. The automatic start-stop system is particularly advantageous here, as wheel loaders or dump loaders often perform repetitive work processes.

[0012] In another advantageous embodiment of the automatic start-stop system, the engine is a combustion engine. This achieves the technical advantage of reducing fuel consumption and pollutant emissions in a simple manner.

[0013] The work vehicle according to the invention is equipped with the automatic start-stop system described above. This work vehicle achieves the same technical advantages as the automatic start-stop system.

[0014] The method according to the invention for operating a work vehicle comprises the steps of detecting a repetitive work cycle of a work vehicle based on at least one operating parameter and determining a switch-off point of the engine based on the operating parameter within the work cycle. This method achieves the same technical advantages as the automatic start-stop system or the work vehicle.

[0015] Embodiments of the invention are explained in more detail with reference to the following figures. Fig. 1 a schematic representation of a work vehicle; Fig. 2 a schematic representation of a repeating work cycle; Fig. 3 a graphical representation of various operating parameters of a repetitive work cycle of a work vehicle; Fig. 4 a graphical representation of various operating parameters of a repeating work cycle of a work vehicle over several cycles; Fig. 5 a schematic representation of an optimization of the switch-off times and switch-on times using a DP-PMP algorithm; Fig. 6 a schematic representation of an exemplary DP-PMP algorithm; Fig. 7 a graphical representation of an exemplary long-term planning of the state of charge; Fig. 8 a graphical representation of an exemplary long-term planning of the state of charge; Fig. 9 a graphical representation of a real-time control for various operating parameters; and Fig. 10 a block diagram of a start-stop procedure for an engine.

[0016] Fig. 1 shows a schematic representation of a work vehicle 100 with an internal combustion engine 102 and an electric machine 104. The work vehicle 100 is, for example, a wheel loader or a dump truck. The work vehicle 100 includes a hybrid drive train 106 for mechanical propulsion of the work vehicle 100. The electric drive units 118 are located in the hybrid drive train 106. The drive units 118 are formed, for example, by electric motors with associated inverters. The drive units 118 are supplied with electrical energy via the battery 122. The battery 122 is, for example, a high-voltage battery.

[0017] The hybrid drivetrain 106 further includes the internal combustion engine 102, which can be coupled into the hybrid drivetrain 106 as needed. For this purpose, a clutch 120 is used, which controllably engages or disengages the internal combustion engine 102. In this way, the electric drive units 118 can be used to propel the work vehicle 100, or the battery 122 can be charged via the electric machine 104. The position of a control pedal represents the requested drive torque and is used to control the electric drive units 118.

[0018] The internal combustion engine 102 is connected to an automatic start-stop system 101. The automatic start-stop system 101 comprises a detection device 105 and a switching controller 107. The detection device 105 serves to detect a repetitive working cycle of the work vehicle 100 based on at least one operating parameter, such as the engine speed and / or the direction of travel. However, one or more other operating parameters or temporal profiles of the operating parameters can also be used. The switching controller 107 can determine a switch-off time of the engine 102 based on the detected operating parameters and switch the engine 102 off at this time. The switching controller 107 can also determine a switch-on time of the engine 102 based on the detected operating parameters and switch the engine 102 on at this time. Between the switch-off and switch-on times, the engine 102 is not running and does not consume any fuel.

[0019] Furthermore, certain components of the work vehicle 100 are moved via a hydraulic system. In this case, pressure is generated using hydraulic oil and converted into mechanical energy. For example, the work vehicle 100 comprises a bucket whose movement is hydraulically controlled. In this case, a user actuates an operating lever (joystick) 110 to initiate the movement of the bucket via a valve control 124. The valve control 124 directs the hydraulic oil to hydraulic pistons, which cause a corresponding movement of the bucket. Furthermore, with a hydraulic power steering system (orbitrol steering) 112, the steering position of the wheels can also be hydraulically controlled. In this case, the user actuates a steering wheel to initiate the movement and control of the wheels, also via a valve control 112.Depending on the operation of the operating lever 110 and the steering wheel, the user requests a flow rate of hydraulic oil for the valve control of the respective component.

[0020] The hydraulic pump 116 is driven independently of the hybrid drivetrain 106 by an electric motor 104. The electric motor 104 is powered by the battery 122, which also supplies power to the drive units 118 with the electric motors. The battery 122 is connected to the electric motor 104 via a DC-AC converter 128. In this way, the battery 122 can be charged via the internal combustion engine 102.

[0021] Fig. 2 shows a schematic representation of a repeating work cycle 130, such as a so-called "V-cycle" of a wheel loader. The work cycle 130 comprises four phases A, B, C, and D. Each phase of the repeating work cycle 130 comprises a specific action that causes and is reflected in a different course of the operating parameters. Phase A comprises driving forward to a loading location 132 and tilting the bucket 134 upward. Phase B comprises driving back to the starting point 136. Phase C comprises driving forward to an unloading location 138 while raising the bucket 134 and unloading the bucket 134 at the unloading location 138 by tilting the bucket 134 downward. Phase D comprises driving back to the starting point 136 while lowering the bucket 134. This work cycle 130 is repeated several times by the wheel loader in this or a similar manner.All phases A, B, C, and D can be recognized in the course of the operating parameters. In general, the repetitive work cycle can also be structured differently.

[0022] Fig. 3a) to 3e) show temporal progressions of various operating parameters within a single working cycle 130. In Fig. 3a) shows the control pedal positions of two pedals as operating parameters, namely an accelerator and a brake pedal. Curve 140 represents the position of accelerator pedal 140, and curve 142 represents the position of the brake pedal. Fig. 3b) the absolute speed of the work vehicle 100 is shown as an operating parameter. In Fig. 3c) the movement of the operating lever 110 and the hydraulic oil flow rate or pressure requested by the user are shown as operating parameters. Fig. 3d) three different lengths of the hydraulic cylinders are shown as operating parameters, which correspond to the operation of the operating lever 110. In Fig. 3e), the power of the internal combustion engine 102 is represented by curve 154, the power of the hydraulic pump 116 by curve 156, and the power of the hydrostatic transmission (HST) by curve 158. The time curve 154 of the engine speed correlates with the time curve of the accelerator pedal position.

[0023] These progressions form recurring patterns that occur in the same or a similar manner in each recurring work cycle 130 of the work vehicle 100. Based on the progressions and patterns shown, a recurring work cycle 130 of the work vehicle 100 can be clearly recorded and recognized by the detection device 105. Furthermore, the work cycle can be divided, for example, into phases A, B, C, and D.

[0024] To identify a work cycle, for example, the curves of the recorded operating parameters of the work cycle 130 can be compared with one or more digitally pre-stored curves of the respective operating parameters in the recording device 105. For this purpose, the recording device 105 comprises a digital memory and a microprocessor with the pre-stored curves in digital form. The pre-stored curves also specify the switch-off times and / or switch-on times. If a curve with a high degree of agreement is found, the switch-off times and / or switch-on times are adopted from this pre-stored curve.

[0025] However, it is also possible to record duty cycles 130 using autocorrelation or cross-correlation of the temporal profiles. Autocorrelation makes it possible to determine relationships in a recorded temporal profile at different points in time. Cross-correlation, on the other hand, indicates the correlation between temporal profiles of different operating parameters. It is also possible to determine suitable switch-off times and / or switch-on times using pattern recognition, whereby an algorithm locates repetitions or regularities in large data sets or across different data sets. Using pattern recognition, the algorithm can also make a performance prediction and use this to develop a rule-based strategy for determining the switch-off times and / or switch-on times. Furthermore, the rule-based strategy can be further refined through optimization over the prediction horizon.

[0026] Fig. 4a) to 4d) show temporal progressions of various operating parameters over several working cycles. Fig. 4a) the power of the hydraulic pump 116 is shown in curve 156 and the power of the electric drive unit (EDU) is shown in curve 160 as operating parameters. Fig. 4b) the flow rate of the hydraulic pump 116 is shown as an operating parameter in curve 162. In Fig. 4c) curve 164 shows the engine torque of pure hybrid operation 100 and curve 166 shows the engine torque with an operating parameter optimized by the algorithm in hybrid and electric operation. Fig. 4d), the state of charge (SoC) of the battery 122 in pure hybrid operation is shown in curve 168 and the state of charge in partial hybrid operation is shown in curve 170 as operating parameters. Fig. 4a) to 4d) show that the operating parameters exhibit similar patterns in repetitive working cycles 130.

[0027] The highlighted areas indicate time periods between the switch-off time 172 and the switch-on time 174, during which the internal combustion engine 102 is switched off by the switching control 107. After the time period has elapsed, the internal combustion engine 102 is switched on again by the switching control 107 at the switch-on time 174. This time period, which is defined by the respective switch-off times 172 and the switch-on times 174, is determined in each work cycle 130 based on operating parameters. The switching control 107 thereby determines the switch-off time 172 and the switch-on time 174 within the work cycle 130.

[0028] This allows optimal switch-off times 172 and switch-on times 174 to be determined for recurring work processes that frequently occur in work vehicles 100. This prevents unfavorable switch-off or idling operation of the combustion engine 102.

[0029] The switch-off times 172 and switch-on times 174 can be optimized using dynamic programming. Dynamic programming (DP) is a method for algorithmically solving an optimization problem by dividing it into subproblems and systematically storing intermediate results.

[0030] Fig. Figure 5 shows a schematic representation of an optimization of the switch-off times 172 and / or switch-on times 174 using a DP-PMP algorithm (Dynamic Programming-Pontryagin's Minimum Principle algorithm). A DP-PMP algorithm can be designed, for example, as follows: minuss(k)∈U∑k=0N−1[m˙f(k)Δt+s⋅SO˙C(k)Δt+ms(k)] ms(k)={ms:uss(k)=10:Otherwise uss(k)={−1:ICE switch off0:Sustain1:ICE switch on Sice(k+1)=Sice(k)+uss(k) Sice(k)={0:ICE off1:ICE on

[0031] Optimization using a DP-PMP algorithm occurs in several steps. The first step is phase detection 176. A phase detection module can be modeled using Stateflow. The relevant phases of a duty cycle 130, such as the charging cycle, acceleration, and / or constant speed phases, can be predefined therein. The driver input signals detected by the detection device 105, such as power and / or flow requirements, are preprocessed in this step and fed to the phase detection module. Phase transitions are detected by the phase detection module when the required conditions for the respective predefined phases are met. The respectively detected driver input signals are stored with the corresponding assigned phase for later use.

[0032] A further step is scenario coordination 178. A driving scenario is predicted and a scenario vector with predicted phases is created depending on the current phase and other available information, such as an operating parameter within the duty cycle 130 or driver input signals.

[0033] A further step is the power and / or flow forecast 180. Based on the scenario vector and other available information, such as the detected history of a selected operating parameter within the duty cycle 130, power forecast vectors and flow forecast vectors are created.

[0034] In the next step, namely the application of the DP-PMP algorithm by means of a DP-PMP module 182, the optimization problem for the individual detected phases is solved over the forecast horizon and thus the switching-on and switching-off times of the motor are computationally optimized. Fig. Figure 6 shows a schematic representation of an exemplary DP-PMP algorithm. Additionally, an optimized equivalence factor s for adjusting the state of charge of the battery 122 can be determined by executing the DP-PMP algorithm. The outputs of the applied DP-PMP algorithm are, on the one hand, calculated optimal switching on and off times of the internal combustion engine (Internal Combustion Engine State - ICE State) and, on the other hand, an optimized equivalence factor s, which remains constant over the forecast horizon.

[0035] In a further step, namely the start and / or stop control 184, the calculated optimal start and stop times of the combustion engine are forwarded from the DP-PMP module 182 to the switching control 107. The switching control 107 checks the engine start / stop conditions and determines the respective actual start and / or stop times 172, 174 of the engine 102. In a further step, the ECMS 186, the optimal charging power for the battery 122 can be calculated via ECMS (Equivalent Consumption Minimization Strategy) using the optimized equivalence factor s determined via the DP-PMP algorithm.

[0036] In a further step, the long-term planning of the state of charge (SOC) 188, the optimal state of charge trajectory can be calculated using the DP-PMP algorithm.

[0037] Fig. 7 and Fig. 8 show graphical representations of an example long-term planning of the state of charge. The phases A, B, C, and D of a work cycle are shown in Fig. 7 are plotted as states 1 to 4 and together correspond to one charging cycle.

[0038] For long-term planning of the state of charge (SOC) 188, the forecast horizon is longer than that of the scenario vector, as additional requirements such as electric driving zones can be taken into account. For long-term planning of the state of charge 188, for example, the first charging cycle can be performed with an initial equivalence factor and without automatic start / stop, as no cycle information is yet available for this charging cycle. This is, for example, shown as area A in Fig. 8. The data of a repeating work cycle 130 of the work vehicle 100 acquired in this cycle based on at least one operating parameter, such as the calculated switch-on and switch-off times of the combustion engine from the first charging cycle or the calculated equivalence factor s of the first charging cycle, are optimized for the second charging cycle using the power requirement of the first charging cycle using the DP-PMP algorithm. This is shown, for example, as area B in Fig. 8 shown.

[0039] A control strategy can be implemented as a real-time control in the form of a so-called model predictive control (Receding Horizon Control - RHC). This is Fig. 9 graphically on the one hand in Fig. 9a) for the charge level and secondly in Fig. 9b) for the switching on and off times of the combustion engine. For this purpose, the forecast horizon is created with the power and / or flow requirements in each phase. The equivalent fuel consumption for the hybrid and electric modes is calculated using the DP-PMP algorithm based on the predicted power and / or flow rate and the equivalence factor s. This achieves the technical advantage, for example, of minimizing the total costs, taking into account the engine start-up costs, since fuel consumption is minimized. Furthermore, by simulating the state of charge, the equivalence factor can be optimized based on the deviation from the actual state of charge, allowing the equivalence factor to be adjusted in real time.

[0040] Fig.10 shows a schematic representation of a start-stop method for an engine 102. In step S101, a repetitive operating cycle 130 of a work vehicle 100 is recorded based on at least one operating parameter. In the subsequent method step S102, a switch-off time 172 of the engine 102 is determined based on the operating parameter within the operating cycle 130.

[0041] The method offers the advantage of preventing unnecessary shutdown of the engine 102. Frequent shutdown and subsequent restart of the engine 102 leads to high wear, high fuel consumption, and high emissions. Furthermore, this method improves the handling and user-friendliness of a work vehicle 100, since the shutdown point 172 of the engine 102 is selected at a favorable time.

[0042] All features explained and shown in connection with individual embodiments of the invention can be provided in different combinations in the subject matter according to the invention in order to simultaneously realize their advantageous effects.

[0043] All method steps can be implemented by devices suitable for performing the respective method step. All functions performed by physical features can be a method step of a method.

Claims

[1] Automatic start-stop system (101) for an engine (102), comprising: - a detection device (105) for detecting a repetitive work cycle (130) of a work vehicle (100) based on at least one operating parameter; and - a switching control (107) for determining a switch-off time (172) of the motor (102) on the basis of the operating parameter within the working cycle (130). [2] Automatic start-stop system (101) according to claim 1, wherein the switching control (107) is designed to determine a switch-on time (174) of the engine (102) on the basis of the operating parameter. [3] Automatic start-stop system (101) according to one of the preceding claims, wherein the operating parameter is an engine speed and / or a direction of travel of the work vehicle (100) and / or an idling of the engine (102). [4] Automatic start-stop system (101) according to one of the preceding claims, wherein the switching control (107) is designed to predict a future operating profile on the basis of the at least one detected operating parameter and / or to determine the switch-off and / or switch-on time (172, 174) of the engine (102) by means of a predefined rule or an optimization of the operating parameter within the working cycle (130). [5] Automatic start-stop system (101) according to one of the preceding claims, wherein the switching control (107) is designed to determine at most one switching-off and / or switching-on time (172, 174) of the engine (102) in a working cycle (130). [6] Automatic start-stop system (101) according to one of the preceding claims, wherein the detection device (105) is designed to compare a detected working cycle (130) with one or more digitally pre-stored profiles with a pre-stored working cycle or a plurality of pre-stored working cycles in which the switch-off and / or switch-on time (172, 174) of the engine (102) is specified. [7] Automatic start-stop system (101) according to one of the preceding claims, wherein the work vehicle (100) is a wheel loader or a dump loader. [8] Automatic start-stop system (101) according to one of the preceding claims, wherein the engine (102) is an internal combustion engine (102). [9] Work vehicle (100) with an automatic start-stop system (101) according to one of claims 1 to 8. [10] Start-stop method for an engine (102), comprising the steps: - detecting (S101) a repetitive work cycle (130) of a work vehicle (100) based on at least one operating parameter; and - Determining (S102) a switch-off time (172) of the motor (102) on the basis of the operating parameter within the working cycle (130).

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