Method for starting an electric drive motor of an electrically drivable bicycle - Patent application

Abstract

[Solution] The present invention relates to a method for starting an electric drive motor (10) of an electrically drivable bicycle, which activates the drive assistance provided by the electric drive motor (10), and a method for starting an electric drive motor (10) of an electrically drivable bicycle, which deactivates the drive assistance provided by the electric drive motor (10).

Description

[Technical Field]

[0001] The present invention relates to a method for starting an electric drive motor of an electrically drivable bicycle, as well as a computer program, a machine-readable storage medium and an evaluation unit provided for carrying out such a method. [Background technology]

[0002] The state of the art knows two-wheeled vehicles, in particular bicycles such as e-bikes / pedelecs, which can propel the two-wheeled vehicle forward by supplementing the driving force provided by the user with a motor, in particular an electric motor. In the case of pedelecs, for example, such motor assistance is only permitted when the cyclist is also pedaling assisted by the cyclist. To ensure that this condition is met, various sensors are often used that are installed to detect when the cyclist is pedaling. Examples of such sensors are torque sensors and rotation speed sensors.

[0003] In the case of e-bikes, which often have torque sensors in the pedals, motor assistance typically only occurs after a driver torque threshold, e.g., approximately 7 Nm, is exceeded, after which the motor subsequently provides many times the driver's power to drive the two-wheeler. Until this point is reached, the motor is usually not yet running (i.e., its RPM corresponds to a value of zero), so it takes some time for the motor to reach the speed of the bicycle's crank. During this time, there is no reaction force yet due to the freewheel used to connect the motor to the bicycle's powertrain, so the motor's RPM increases correspondingly very rapidly. When the freewheel engages, this can simultaneously cause strong vibrations in the powertrain, and in this regard, load-absorbing methods are often used to partially compensate for these vibrations. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 025876 [Patent Document 2] European Patent Application Publication No. 2706005 [Patent Document 3] European Patent Application Publication No. 0650887 [Patent Document 4] European Patent Application Publication No. 2743166 [Patent Document 5] German Patent Application Publication No. 102018132780 [Patent Document 6] German Patent Application Publication No. 102014218020 [Patent Document 7] Japanese Patent Publication No. 2020-128185 Summary of the Invention

[0005] According to the present invention, a method is proposed for starting an electric drive motor (hereinafter also referred to as "drive motor" for short) of an electrically drivable bicycle (hereinafter also referred to as "bicycle" for short), such as an e-bike or pedelec. The electric motor is coupled by a freewheel to the powertrain of the bicycle in such a way that the torque that can be generated by the drive motor, via the freewheel, assists in driving the bicycle in the forward direction of travel.

[0006] In a first step of the method according to the invention, the pedal stroke rate (also called cadence) of the cyclist is detected, which is preferably determined on the basis of a rotational speed sensor of the bicycle, for example a rotational speed sensor known from the prior art.

[0007] In a second step of the method according to the present invention, if the detected pedal strokes of the driver exceed a predefined pedal stroke threshold, the electric drive motor is operated with a predefined default first target speed for the drive motor and a predefined default first torque for the drive motor that are less than the driver's pedal strokes. The first torque is a correspondingly smaller maximum allowable torque that can be used to reach the first target speed. The pedal stroke threshold may also correspond to a value of 0 revolutions per minute. Preferably, the bicycle includes an evaluation unit that receives speed information from a bicycle speed sensor and torque information from a torque sensor and controls and / or regulates the drive motor based on the speed information and torque information. The respective target speeds and / or torques and / or corresponding thresholds or quantities for deriving them are preferably stored in an internal and / or external memory unit that is information-technically coupled to the evaluation unit.

[0008] It should be noted that before the second method step is performed, the drive motor has, for example, a rotational speed of zero, but it is also conceivable that at this point the drive motor has a rotational speed greater than zero but less than the first target rotational speed.

[0009] Similarly, it should be noted that the target speeds and torques for the drive motors described here and below represent values ​​as they occur or exist in the powertrain, since in some cases a gear ratio between the drive motor and the powertrain (specifically, between the motor and the sprocket) is used. In other words, these values ​​do not necessarily represent the target speeds and torques directly at the drive motor shaft, but rather the resulting values ​​in the powertrain.

[0010] It should further be noted that the transition from the first to the second method step can be linked to additional conditions, such as that the driver's pedal strokes do not repeatedly fall below a new pedal stroke threshold (alternatively, a hysteresis function or the like can also be used here), and / or that the pedal strokes do not increase further for a predefined period of time, and / or that a certain driver torque must first be recorded after several successive starting operations without any subsequent driver torque.

[0011] In a third step of the method according to the present invention, if the driver torque applied by the driver to the powertrain exceeds a first predefined driver torque threshold, the electric drive motor is operated at a second predefined default target speed for the drive motor that is higher than the first target speed and at a second predefined default torque for the drive motor. It should be noted that the second torque is the maximum allowable torque that can be used to reach the second target speed and may be correspondingly smaller. Preferably, the second torque is substantially equal to the first torque or at least has the same order of magnitude as the first torque, without limiting the possible ratio of the two torques to each other. Preferably, in this third method step, the second target speed and the second torque are selected so that a freewheel, which is provided to couple the drive motor to the powertrain, is engaged and the torque applied by the drive motor to the powertrain already produces a slight tension on the bicycle chain in the forward direction of travel. However, other effects of the second target speed and the second torque on freewheel engagement and / or chain tension are also conceivable in connection with the method according to the invention. Essentially, the first torque and the second torque are determined so that they do not substantially result in a driving assistance or do not result in a driving assistance that is perceptible by the cyclist. For example, both torque values ​​are determined so that they do not exceed a value of 5 Nm each.

[0012] In a fourth step of the method according to the present invention, if the driver torque exceeds a predefined second driver torque threshold, which is higher than the first driver torque threshold, the drive motor is activated with a predefined third default torque, where the third driver torque is a target torque to be reached and is determined to result in a predefined drive assistance. Since the freewheel is preferably already engaged at this point, there is no difference in the driver's pedaling speed when proceeding to the fourth method step, so that load shocks can be prevented or significantly reduced when the actual drive motor assistance torque is applied. This allows the method according to the present invention to achieve numerous advantages, including improved riding comfort, reduced structural and / or material loads, and correspondingly increased durability of bicycle components. A further advantage is that the method according to the present invention allows for faster activation of drive motor assistance, which allows for particularly dynamic / sporty driving.

[0013] Since the respective target speeds in the second and third method steps represent actual reference variables for controlling and / or regulating the drive motor, these method steps can be assigned to one start-up mode of the drive motor, designated here as the speed-start-up mode. In contrast, the start-up mode for the drive motor represented by the fourth method step can be considered a torque-start-up mode, since the third torque here represents an actual reference variable for controlling and / or regulating the drive motor. Correspondingly, the evaluation unit for starting the drive motor switches from the speed-start-up mode to the torque-start-up mode when transitioning from the third method step to the fourth method step. In this context, it is conceivable that the respective start-up modes are implemented in the evaluation unit by two independent logic and / or software units, with switching between them as the situation dictates.

[0014] Furthermore, according to the present invention, a method for starting an electric drive motor of an electrically drivable bicycle is proposed. The embodiment of the bicycle and the coupling of the drive motor to the power train of the bicycle generally correspond to the description of the method above, and therefore this is pointed out to avoid repetition.

[0015] In one step of the method according to the present invention, the rider torque applied by the rider of the bicycle to the bicycle's powertrain and the number of pedal strokes by the rider are detected.

[0016] In a further step of the method according to the invention, the electric drive motor is operated with a predefined default third target speed and a predefined default fourth torque for the drive motor if the driver torque is less than or equal to a predefined third driver torque threshold for a first predefined time period. The first predefined time period may correspond, for example, to a time period between 200 ms and 300 ms, or may correspond to a different time period. It should be noted that the fourth torque is a correspondingly smaller maximum allowable torque that can be used to reach the third target speed.

[0017] In a further step of the method according to the present invention, if the driver torque (MF) is equal to or less than the third driver torque threshold for a second predefined time period longer than the first time period, or if the pedal rotation rate exceeds a predefined pedal rotation rate threshold (e.g., one rotation) while the driver torque (MF) is equal to or less than the third driver torque threshold (MFS3), the electric drive motor is operated at a predefined default value for a fourth target rotation rate that is less than the third target rotation rate and at a predefined default value for a fifth torque for the drive motor, the drive motor being coupled to the bicycle's powertrain by freewheeling, and the fourth and fifth torques being determined so as not to substantially provide drive assistance. Note that the fifth torque is a maximum allowable torque that can be used to reach the fourth target rotation rate and may be correspondingly smaller. For example, both torque values ​​are determined so as not to exceed a value between 4 Nm and 5 Nm, respectively. The second predefined time period may, for example, correspond to a time period between 800 ms and 1000 ms or a different time period.

[0018] The method described above offers the advantage, inter alia, that the transition from an active drive motor assistance to an inactive drive motor assistance is preferably not perceptible, either tactilely or acoustically, by the cyclist, which improves riding comfort, especially for the cyclist.

[0019] It should be noted generally that the above-described method does not fundamentally limit the possible transitions between the individual method steps. In particular, if the bicycle driver does not fulfill all the conditions necessary for a transition from non-drive motor-assisted driving to drive motor-assisted driving or vice versa (for example, because the driver has previously terminated the starting process or reapplies a briefly interrupted driver torque), it is conceivable to return to the respective previous method step depending on further boundary conditions (for example, to switch back to the respective starting state without limiting the method according to the invention).

[0020] In summary, the present invention relates to a method for starting an electric drive motor of an electrically drivable bicycle, which activates the drive assistance provided by the electric drive motor, and a method for starting an electric drive motor of an electrically drivable bicycle, which deactivates the drive assistance provided by the electric drive motor.

[0021] The dependent claims show advantageous further configurations of the invention.

[0022] In a preferred embodiment of the invention, the pedal stroke threshold corresponds to a value between 5 and 25 revolutions per minute, preferably between 10 and 20 revolutions per minute, and particularly preferably to a value of 15 revolutions per minute. Furthermore, the target rotational speed corresponds to a value between 60% and 99%, preferably between 70% and 90%, and particularly preferably to a value of 80% of the previously detected driver pedal strokes. Particularly preferably, the second target rotational speed substantially corresponds to the driver's pedal strokes. Particularly preferably, the second target rotational speed corresponds exactly to the detected driver pedal strokes or corresponds to a value higher than this.

[0023] Advantageously, the first driver torque threshold corresponds to a value between 1 Nm and 9 Nm, preferably between 3 Nm and 7 Nm, and particularly preferably between 5 Nm. Furthermore, the second driver torque threshold corresponds to a value between 4 Nm and 15 Nm, preferably between 6 Nm and 12 Nm, and particularly preferably between 7 Nm and 9 Nm. Furthermore, the third torque corresponds to a value that is advantageously at least twice, advantageously at least three times, and particularly preferably at least four times the respective driver torque.

[0024] In a further advantageous embodiment of the invention, the transition between the second torque and the third torque is performed step by step. This can be achieved by setting one or more intermediate values ​​between the second torque and the third torque while the transition between these two values ​​continues, so that a more or less gentle transition between the two values ​​is achieved. This makes it possible to further reduce the tactile and / or acoustic effects of such a transition, which may still be barely perceptible by the cyclist, and thus further improves riding comfort.

[0025] Preferably, the predefined third target speed substantially corresponds to the pedal stroke of the rider, and particularly preferably corresponds to at least the previously detected pedal stroke. Furthermore, the third rider torque threshold preferably corresponds to a value between 4 Nm and 15 Nm, preferably between 6 Nm and 12 Nm, and particularly preferably between 7 Nm and 9 Nm. Alternatively or additionally, the electric drive motor is deactivated (i.e., switched to zero current) if the rider torque is below the third rider torque threshold for a predefined third time period that is longer than the first and second times, or if the rider's pedal stroke rate gradually slows while the rider torque (MF) is below the third rider torque threshold (MFS3). This allows for saving electrical energy (e.g., in the battery) stored on the bicycle. The predefined third time period corresponds, for example, to a time period between 1500 ms and 3000 ms, or a different time period.

[0026] In a further advantageous embodiment of the present invention, the respective torque for the drive motor is determined taking into account the estimated load on the drive motor. To this end, the current measured values ​​of the bicycle's speed and torque sensors are advantageously used in each case, making it possible to determine the exact engagement state of the drive motor (whether it is already engaged or still rotating freely) based on these measured values, even in the case of changing load conditions (e.g., climbing a mountain road under full load, changing gears, etc.). This information is then taken into account as a control and / or adjusting variable when determining the respective torque. It should be noted that this can be advantageously used both during the process of activating and deactivating the drive motor assistance. Furthermore, it is possible to take the estimated load into account only for a portion of the respective torque values ​​in the method according to the present invention.

[0027] Furthermore, the invention proposes a computer program provided for carrying out the method according to the above description.

[0028] The present invention also provides a machine-readable storage medium on which the computer program is stored, such as an electronic and / or magnetic and / or optical and / or other storage medium.

[0029] The present invention further proposes an evaluation unit that is provided for carrying out the method according to the above description. The evaluation unit may be configured, for example, as an ASIC, FPGA, processor, digital signal processor, microcontroller, etc. It is also conceivable that the evaluation unit is a component of the electronic unit of the drive motor or an independent component. It is also conceivable that the evaluation unit is informationally coupled to an internally and / or externally connected memory unit, for example, for storing data received and / or calculated by the evaluation unit. It is also conceivable that the memory unit is such a memory unit that contains the computer program implementing the method steps according to the present invention, and that this computer program is executed by the evaluation unit.

[0030] Some embodiments of the present invention will now be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a flow chart illustrating the steps of one embodiment of a method according to the present invention. [Figure 2] 4 is a flow chart illustrating steps of one embodiment of another method according to the present invention. [Figure 3] 1 is a schematic diagram of components according to the invention of a bicycle; DETAILED DESCRIPTION OF THE INVENTION

[0032] FIG. 1 shows a flow chart illustrating the steps of one embodiment of a method according to the invention for starting an electric drive motor 10 of an electrically drivable bicycle, in a starting state of the bicycle in which the drive motor 10 does not provide drive assistance and the rider does not apply a rider torque MF.

[0033] In step 100, the pedal strokes FT of the cyclist are determined by the evaluation unit 30 of the bicycle, by the evaluation unit 30 receiving the measurement signals of the rotational speed sensors of the bicycle.

[0034] If the driver's pedal speed FT exceeds the pedal speed threshold FTS, which has a magnitude of 15 revolutions per minute, the drive motor 10 is activated in step 200 by the evaluation unit 30 with a default value for the first target rotation speed N1, which here corresponds to 80% of the detected driver's pedal speed FT, and a default value for the first torque M1 for the drive motor 10. The first torque M1 here corresponds to an initial value of 8 Nm and is automatically reduced to a value of 4 Nm within a time period of 200 ms. It should be noted that the first torque M1 is the maximum permissible torque.

[0035] If the driver torque MF applied by the driver via pedals 60 to the bicycle powertrain exceeds a first driver torque threshold MFS1, which corresponds to a value of 5 Nm in this case, then in step 300, drive motor 10 is operated at a second target rotation speed N2, which corresponds to the detected pedal stroke FT, and with a second torque M2 for drive motor 10, which corresponds to a value of 8 Nm in this case. This step causes drive motor 10, which is coupled to the bicycle powertrain by a freewheel, to now be engaged with the powertrain via the freewheel.

[0036] Next, when the driver torque MF exceeds a second driver torque threshold MFS2, which here corresponds to a value of 7 Nm, the drive motor 10 is operated in step 400 with a default value of a third torque M3, which here corresponds to a value four times the driver torque MF.

[0037] Advantageously, the transition between the second torque M2 and the third torque M3 is performed using a plurality of intermediate values, so that a smooth transition between the second torque M2 and the third torque M3 is achieved.

[0038] Furthermore, it is preferable to detect an estimated load on the drive motor 10 based on the measured values ​​of a rotational speed sensor and a torque sensor, and incorporate this information into the determination of the torque value at each time.

[0039] FIG. 2 shows a flow chart illustrating the steps of one embodiment of another method according to the present invention for starting the electric drive motor 10 of an electrically drivable bicycle, in this case a starting state of the bicycle in which the drive motor 10 provides active drive assistance while the rider applies a rider torque.

[0040] In step 500, the evaluation unit 30 of the bicycle receives measurement signals from the bicycle's rotation speed sensor and torque sensor, thereby detecting the driver torque MF acting on the powertrain by the bicycle rider and the rider's pedal stroke FT.

[0041] If the driver torque MF is less than or equal to the third driver torque threshold MFS3, here corresponding to a value of 7 Nm, for a first time T1, here corresponding to a value of 200 ms, then in step 600 the drive motor 10 is operated with the default value of the third target speed N3 for the magnitude of the currently detected pedal stroke FT and the default value of the fourth torque M4, here corresponding to a value of 15 Nm.

[0042] Next, if the driver torque MF is less than or equal to the third driver torque threshold MFS3 for a second time T2, which corresponds to a value of 800 ms here, the drive motor 10 is operated at a default value for the fourth target rotation speed N4, which corresponds to 80% of the current pedal stroke TF here, and a default value for the fifth torque M5, which corresponds to a value of 4 Nm here.

[0043] Next, if the rider torque MF is less than or equal to a third rider torque threshold MFS3 for a third time T3, here corresponding to a value of 1.5 s, operation of the electric drive motor 10 is stopped in order to conserve electrical energy from the bicycle battery 50.

[0044] 3 is a schematic diagram of the components of a bicycle according to the present invention. The bicycle has an electric drive motor 10, which is supplied with electrical energy by means of a storage battery 50. The drive motor 10 is coupled to the bicycle chain 40 of the bicycle by means of a freewheel (not shown), and is arranged to provide driving assistance to the bicycle in the coupled state. The bicycle further has two pedals 60, via which the bicycle rider can apply a rider torque MF to the bicycle chain 40. The drive motor 10 includes an evaluation unit 30, which is information-technically coupled to a memory unit 20 and is arranged to carry out all steps of the method according to the present invention described in this disclosure based on a computer program filed in the memory unit 20. [Explanation of symbols]

[0045] 10 Electric drive motor 20 Storage media, memory units 30 evaluation units 100 Steps to detect the number of steps 200. Activating the electric drive motor if the number of pedal strokes exceeds the pedal stroke threshold. 300. Activating the electric drive motor if the driver torque exceeds a first driver torque threshold. 400. Activating the electric drive motor if the driver torque exceeds a second driver torque threshold. 500 Step of detecting driver torque and pedaling frequency 600 activating the electric drive motor if the driver torque is less than or equal to a third driver torque threshold. 700 activating the electric drive motor if the driver torque is less than or equal to a third driver torque threshold or if the pedal rotation rate exceeds a pedal rotation threshold. 800. Stopping operation of the electric drive motor FT Steps FTS step count threshold M1 First Torque M2 Second torque M3 Third Torque M4 4th Torque M5 5th Torque MF Driver Torque MFS1 First Driver Torque Threshold MFS2 Second Driver Torque Threshold MFS3 Third Driver Torque Threshold N1 First target rotation speed N2 Second target rotation speed N3 Third target rotation speed N4 Fourth target rotation speed T1 First Time T2 Second Time

Claims

1. A method for controlling an electric drive motor (10) of an electrically drivable bicycle, comprising: Detecting a pedal stroke count (FT), which is the number of times the bicycle rider steps on the bicycle pedals per unit time (100); a step (200) of operating the electric drive motor (10) at a first target rotation speed (N1) less than the pedal stroke number (FT) and at a first torque (M1) if the detected pedal stroke number (FT) exceeds a pedal stroke number threshold (FTS) predefined for determining whether to start the electric drive motor (10); a step (300) of operating the electric drive motor (10) at a second target rotation speed (N2) equal to the pedal stroke (FT) and at a second torque (M2) so that the electric drive motor (10) and the powertrain are engaged via a freewheel, if the value of the driver torque (MF) applied by the driver to the powertrain of the bicycle after starting the electric drive motor (10) exceeds a predefined first driver torque threshold (MFS1); operating (400) the electric drive motor (10) at a third torque (M3) if, during engagement of the electric drive motor (10) with the powertrain, the value of the driver torque (MF) exceeds a predefined second driver torque threshold (MFS2) that is higher than the first driver torque threshold (MFS1); and each of the first torque (M1) and the second torque (M2) being predefined such that operation of the electric drive motor (10) does not assist driving by the driver; the third torque (M3) is a predefined target torque such that operation of the electric drive motor (10) assists driving by the driver; The electric drive motor (10) is coupled to the powertrain by the freewheel, allowing the electric drive motor (10) to transmit torque to the powertrain in the forward driving direction when engaged. method.

2. the footstep threshold (FTS) is between 5 and 25 revolutions per minute; and / or The first target rotation speed (N1) is any value in a range from 60% to 99% of the number of times of pedaling (FT), The method of claim 1.

3. The first driver torque threshold (MFS1) is any value in the range of 1 Nm to 9 Nm, the second driver torque threshold (MFS2) is any value in the range of 4 Nm to 15 Nm; and / or The value of the third torque (M3) is equal to or greater than twice the value of the driver torque (MF). The method according to claim 1 or 2.

4. and operating the electric drive motor (10) at a torque of an intermediate value between the value of the second torque (M2) and the value of the third torque (M3) during a period from when the electric drive motor (10) is operated at the second torque (M2) to when the electric drive motor (10) is operated at the third torque (M3). The method according to any one of claims 1 to 3.

5. A method for controlling an electric drive motor (10) of an electrically drivable bicycle, comprising: Detecting (500) a rider torque (MF) applied by the rider of the bicycle to the bicycle's powertrain and a pedal stroke (FT), which is the number of times the rider pedals the bicycle per unit time; a step (600) of operating the electric drive motor (10) at a third target rotation speed (N3) equal to the pedal stroke (FT) and at a fourth torque (M4) predefined so that the electric drive motor (10) does not assist the rider in driving, if the value of the rider torque (MF) is equal to or less than a third predefined rider torque threshold (MFS3) for a first predefined time (T1) when the electric drive motor (10) is engaged with the power train of the bicycle via a freewheel and the electric drive motor (10) is operating to assist the rider in driving; operating (700) the electric drive motor (10) at a predefined fourth target speed (N4) that is less than the third target speed (N3) and at a fifth torque (M5) that is less than the fourth torque if, with the electric drive motor (10) and the powertrain engaged, the value of the driver torque (MF) is less than or equal to the third driver torque threshold (MFS3) for a predefined second time (T2) that is longer than the first time (T1), or if, with the electric drive motor (10) and the powertrain engaged, the pedal rotation speed exceeds a predefined pedal rotation threshold while the value of the driver torque (MF) is less than or equal to the third driver torque threshold (MFS3); and The electric drive motor (10) is coupled to the powertrain by the freewheel, allowing the electric drive motor (10) to transmit torque to the powertrain in the forward driving direction when engaged. method.

6. 6. The method of claim 5, wherein the third driver torque threshold (MFS3) is any value in the range of 4 Nm to 15 Nm.

7. and deactivating the electric drive motor (10) if, while the electric drive motor (10) and the powertrain are engaged, the value of the driver torque (MF) is equal to or less than the third driver torque threshold (MFS3) for a predefined third time (T3) that is longer than the second time (T2), or if, while the electric drive motor (10) and the powertrain are engaged and the value of the driver torque (MF) is equal to or less than the third driver torque threshold (MFS3), the driver's pedal stroke (FT) decreases over time.

7. The method according to claim 5 or 6.

8. measuring a physical quantity related to a load applied to the electric drive motor (10); and determining a torque to be commanded to the electric drive motor (10) based on the measured physical quantity. The method according to any one of claims 1 to 7.

9. A method for causing a computer controlling an electric drive motor (10) to execute the method according to any one of claims 1 to 8, Computer program.

10. A computer program according to claim 9 is stored on the A machine-readable storage medium (20).

11. Carrying out the method according to any one of claims 1 to 8 An evaluation unit (30).

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