Method for operating a drive of an electric bicycle, having a process of ascertaining an overheating protection of the electric drive

Abstract

The invention relates to a method for operating a drive of an electric bicycle (1), having a process of ascertaining an overheating protection of an electric drive (2). The method has the steps of receiving and / or reading state data, wherein the state data comprises the temperature of the electric drive (2) and the temperature gradient of the electric drive (2); receiving an overheating protection characteristic field (5) and / or reading the overheating protection characteristic field (5) from a storage device, said overheating protection characteristic field (5) indicating the maximum permissible output of the electric drive (2) on the basis of the state data; ascertaining the maximum permissible output from the overheating protective characteristic field (5) using the state data; and outputting an output which maximally equals the maximum permissible output of the electric drive (2).

Description

[0001] Description

[0002] title

[0003] Method for operating a drive of an electric bicycle with a determination of an overheating protection of the electric drive

[0004] The present invention relates to a method for operating a drive of an electric bicycle with a determination of an overheating protection of an electric drive of the electric bicycle, as well as to an electric bicycle.

[0005] State of the art

[0006] The sales success of an electric bicycle depends, among other things, on the interaction between the behavior of the electric motor and the electric bicycle rider. While the electric bicycle is being driven by the rider, the electric motor provides support and provides torque to assist the rider in driving the electric bicycle. Critical temperatures must be avoided when operating the electric motor. Exceeding these critical temperatures will cause damage to the electric motor, which could lead to motor failure, a reduction in the service life of the electric motor, or even a fire. Therefore, reaching such critical temperatures must be avoided at all costs.

[0007] To protect the electric motor, characteristic maps are stored in the electric motor control system which switch the electric motor off at a switch-off temperature which is lower than the critical temperature. However, the rider of the electric bike would not find it pleasant if the electric motor switched off abruptly without prior notice or warning. Current characteristic maps for controlling electric motors take this into account by limiting the electric motor's power at a temperature which is lower than the switch-off temperature. In this way, the electric motor control system suggests to the rider that the switch-off temperature and the corresponding drop in power of the electric motor can be expected with a further increase in temperature. This enables the rider to reduce the power required by the electric motor in good time and to avoid a drop in assistance due to the electric motor overheating.

[0008] Disclosure of the invention

[0009] The inventive method for operating a drive of an electric bicycle with a determination of overheating protection of an electric drive with the features of claim 1 comprises several steps. One step comprises receiving and / or reading status data, wherein the status data includes a temperature of the electric drive and a temperature gradient of the electric drive. By receiving and / or retrieving the temperature gradient of the electric drive, a temporal rate of change of the temperature of the electric drive can be taken into account in addition to the current temperature of the electric drive.

[0010] A further step involves receiving an overheating protection map and / or reading the overheating protection map from a memory, wherein the overheating protection map indicates a permissible maximum power of the electric drive depending on the status data. The permissible maximum power protects the electric drive of the electric bicycle from potential damage due to overheating. This enables lower maintenance requirements, a longer service life, and higher performance over the lifetime of the electric drive.

[0011] A further step of the method according to the invention comprises determining a permissible maximum power from the overheating protection map using the status data. Accordingly, a permissible maximum power is determined at least using the temperature and the temperature gradient of the electric drive. By taking the temperature gradient into account, it is possible to predict the temporal rate of change at which the temperature of the electric drive will rise, given the same temperature, and to determine a corresponding limitation of the maximum power that can be delivered by the electric drive from the overheating protection map. In a further step, the electric drive outputs a power that is at most the permissible maximum power of the electric drive. Accordingly, the electric drive can be operated with a different permissible maximum power at the same temperature but with a different temperature gradient.

[0012] The subclaims show preferred developments of the invention.

[0013] In the overheating protection map, the permissible maximum power decreases with increasing temperature and / or increasing temperature gradients of the electric drive. The decreasing permissible maximum power of the electric drive suggests to the driver that the electric drive is at a high temperature and that the electric drive is likely to be shut down for overheating protection reasons.

[0014] Preferably, in the overheating protection map, the permissible maximum power drops from a starting temperature and above. This means that at an electric drive temperature that is greater than or equal to a starting temperature, the permissible maximum power of the electric drive is less than a maximum permissible maximum power of the electric drive. From a final temperature onwards, the permissible maximum power does not drop any further in the overheating protection map, whereby the final temperature is greater than the starting temperature. By setting a starting temperature, the drop in the permissible maximum power is limited to the temperature range above the starting temperature and above. The driver therefore does not experience any restriction of the permissible maximum power of the electric drive in a temperature range below the starting temperature.The limited temperature range between the starting temperature and the final temperature is sufficient to suggest to the driver in good time that the permissible maximum power of the electric drive must be restricted due to the high temperatures.

[0015] Particularly preferably, in the overheating protection map, the permissible maximum power assumes the value zero from the final temperature and above.

[0016] The electric drive is thus switched off at and above the final temperature. This prevents the electric drive from reaching a harmful temperature range. In the overheating protection map, the starting temperature preferably decreases with increasing temperature gradients and the starting temperature increases with decreasing temperature gradients. At the same temperature and different temperature gradients, a higher temperature is reached in the same time in the case of a higher temperature gradient than in the case of a lower temperature gradient. If the permissible maximum power is restricted from the same starting temperature in both cases, a higher temperature is reached in a shorter time in the case of a higher temperature gradient and a corresponding restriction of the permissible maximum power is implemented.At the same temperature but with a different temperature gradient, the driver perceives the restriction of the permissible maximum power as more abrupt at a higher temperature gradient than at a lower temperature gradient. If the starting temperature for restricting the permissible maximum power is already at lower temperatures at a higher temperature gradient than is the case with lower temperature gradients, the restriction of the permissible maximum power is spread over a wider temperature range and thus over a longer duration. Taking the higher temperature gradient into account, the driver perceives such a restriction of the permissible maximum power of the electric drive as comparable to the restriction at a lower temperature gradient and a higher starting temperature.

[0017] In a particularly preferred case, the starting temperatures are selected depending on the temperature gradients such that, at a constant temperature gradient, the limitation of the permissible maximum power occurs over the same period until the final temperature is reached. This means that the user does not notice any difference in the limitation of the permissible maximum power at different temperature gradients.

[0018] Preferably, the starting temperature in the overheating protection map lies between a first starting temperature limit and a second starting temperature limit, with the first starting temperature limit being different from the second starting temperature limit. If a restriction occurs as a result of a very high temperature gradient even at very low temperatures, the driver perceives this as a negative impairment. From a certain temperature gradient, the driver assumes a shorter time to reach the final temperature with a constant temperature gradient. In addition, such very high temperature gradients are used by the driver for short acceleration bursts, as is the case during an overtaking maneuver. Especially in such overtaking maneuvers, a premature restriction of the permissible maximum power at lower temperatures is perceived by the driver as inappropriate.In addition, the aim is to prevent the temperature range between the start temperature and the end temperature from becoming too narrow when the temperature gradient is very low. The driver would find this unpleasant, as at temperatures close to the end temperature the driver is not yet given any indication of a restriction and thus no indication of an approach to the end temperature. If the temperature gradient changes in the high temperature range, the driver would again perceive an abrupt restriction of the permissible maximum power of the electric drive, without this having been suggested to them beforehand by a restriction of the maximum electrical power of the electric drive. To take these two circumstances into account, the start temperature is limited to a temperature range between the first start temperature limit and the second start temperature limit.

[0019] Particularly preferably, the status data includes a battery charge level of an electrical energy storage device of the electric bicycle. This makes it possible to make the permissible maximum power dependent on the battery charge level in the overheating protection map, in addition to the temperature and the temperature gradient. Thus, the overheating protection map can exhibit a higher starting temperature when the battery charge level is high than when the battery charge level is low. Furthermore, the permissible starting temperature can decrease as the battery charge level decreases. This allows unrestricted maximum power to be drawn from the electric drive when the electrical energy storage device is charged until the higher starting temperature is reached. Furthermore, by lowering the starting temperature when the battery charge level of the electrical energy storage device is low, a critical state of the electrical energy storage device is avoided.

[0020] The status data preferably includes a gradient of the path on which the electric bicycle is traveling and / or a GPS position of the electric bicycle. This makes it possible to make the permissible maximum power in the overheating protection map dependent not only on the temperature and the temperature gradient, but also on the gradient of the path on which the electric bicycle is traveling. Thus, the overheating protection map can exhibit a higher starting temperature for a gentle path than for a steep path. Furthermore, the permissible starting temperature can decrease as the gradient of the path decreases. This allows unrestricted maximum power to be drawn from the electric drive over a section of the path with no gradient until the higher starting temperature is reached. Furthermore, by lowering the starting temperature as the gradient of the path increases, a critical state of the electrical energy storage device is avoided.

[0021] The status data preferably includes weather information, in particular an ambient temperature. The ambient temperature can be used to consider a potential cooling capacity of the motor through convection, as well as a potential change in temperature and temperature gradient over time. Taking the ambient temperature into account makes it possible to make the permissible maximum power in the overheating protection map dependent not only on the temperature and the temperature gradient, but also on the ambient temperature. Thus, the overheating protection map can exhibit a lower starting temperature at a high ambient temperature than at a lower ambient temperature. Furthermore, the permissible starting temperature can decrease as the ambient temperature decreases. This allows an unrestricted permissible maximum power to be drawn from the electric drive at a lower ambient temperature until the higher starting temperature is reached.In addition, by reducing the starting temperature at a higher ambient temperature, a critical state of the electrical energy storage system is avoided.

[0022] The invention further encompasses an electric bicycle. The electric bicycle comprises sensors, an electrical energy storage device, an electric drive, and a control unit. The sensors are configured to measure at least one temperature of the electric drive and one temperature gradient of the electric drive. The control unit is connected to the sensors and the electric drive for data exchange. The control unit is configured to carry out a method according to one of the preceding embodiments. This enables the control unit to control the electric drive of the electric bicycle depending on the temperature and the temperature gradient.

[0023] Short description of the drawings

[0024] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0025] Figure 1 shows a schematic representation of an electric bicycle according to an embodiment of the invention, and

[0026] Figure 2 shows a schematic representation of an overheating protection map according to one of the embodiments of the invention.

[0027] Embodiments of the invention

[0028] Figure 1 shows a schematic representation of an electric bicycle 1 according to an exemplary embodiment of the invention. The electric bicycle 1 comprises an electrical energy storage device 3, an electric drive 2, sensors 4, and a control unit. The electric drive 2 comprises an electric motor. The sensors 4 are configured to measure at least a temperature of the electric drive 2 and a temperature gradient of the electric drive 2. Thus, not only the current temperature of the electric drive 2 but also the temporal rate of change of the temperature of the electric drive 2 can be taken into account.

[0029] The control unit is connected at least to the sensors 4 and the electric drive 2 for the exchange of data. Thus, variables measured by the sensors 4, such as the temperature of the electric drive 2 and the temperature gradient of the electric drive 2, can be transmitted to the control unit and / or retrieved by the control unit from the sensors 4. Furthermore, the control unit is able to transmit signals to the electric drive 2 and thereby control the electric drive 2. Preferably, the sensors 4 are configured to detect a battery charge state of the electrical energy storage device 3. Preferably, the sensors 4 can be configured to determine an incline of the path on which the electric bicycle 1 is located. Preferably, the sensors 4 are designed to determine an ambient temperature of the electric bicycle 1.Particularly preferably, the control unit is configured to receive and / or retrieve a GPS position of the electric bicycle 1. Particularly preferably, the control unit is configured to receive and / or retrieve weather information regarding the location of the electric bicycle 1. Thus, when controlling the electric drive 2, the control unit can take into account, in addition to the temperature and the temperature gradient, other important variables for the behavior and changes in the thermal load of the electric drive 2.

[0030] The electrical energy storage device 3 and the electric drive 2 are connected to each other via an electrical connection, so that electrical energy can be exchanged between the electrical energy storage device 3 and the electric drive 2.

[0031] The control unit is preferably configured to carry out a method according to one of the preceding embodiments. The control unit can receive and / or retrieve the temperature measured by the sensors 4 and the temperature gradient of the electric drive 2, and receive and / or read an overheating protection map 5 from a memory. The control unit is configured to determine a permissible maximum power of the electric drive 2 using the overheating protection map 5, the temperature of the electric drive 2, and the temperature gradient, and to transmit this permissible maximum power to the electric drive 2. The temperature gradient allows a temporal rate of change of the temperature of the electric drive 2 to be taken into account when determining the permissible maximum power.

[0032] Particularly preferably, the control unit is configured to receive the variables measured by the sensors 4, as listed above, and additionally to receive weather information at the location of the electric bicycle 1 and a GPS position of the electric bicycle. The control unit is configured to receive and / or read the overheating protection map 5 from the memory. Preferably, the control unit is configured to determine a permissible maximum power of the electric drive 2 using the overheating protection map and the variables previously received and / or read from the sensors and the GPS position of the electric bicycle 1 and the weather information at the location of the electric bicycle 1. The control unit sends the permissible maximum power to the electric drive 2. Thus, further variables that influence the development of the temperature of the electric drive 2 can be taken into account.

[0033] Figure 2 shows a schematic representation of an overheating protection map 5. The Z-axis of the overheating protection map 5 indicates the permissible maximum power of the electric drive 2 as a percentage of a maximum permissible maximum power. The Z-axis is shown in the range from 0 to 100 percent of the maximum permissible maximum power. The X-axis of the overheating protection map 5 represents the temperature scale, with the temperature scale indicating the temperature of the electric drive 2. The end temperature 6 is shown at the left end of the X-axis; temperatures to the right of the end temperature 6 on the X-axis decrease compared to the end temperature 6. Also shown on the X-axis are a first start temperature 7 and a second start temperature 8, with the second start temperature 8 being lower than the first start temperature 7. The Y-axis of the overheating protection map 5 describes the temperature gradient.

[0034] At a constant temperature gradient, the overheating protection map 5 shows no reduction in the maximum permissible maximum power at temperatures below the associated starting temperature 7, 8 for a constant temperature gradient. As the starting temperature 7, 8 associated with a constant temperature gradient is exceeded, the permissible maximum power decreases with increasing temperature. If the temperature reaches the end temperature 6 at a constant temperature gradient, a value of zero is assigned to the permissible maximum power. The electric drive 2 is switched off at a permissible maximum value of zero. This structure of the overheating protection map 5 allows the driver to call up the maximum permissible maximum power of the electric drive 2 both below a starting temperature 7, 8.In addition, before reaching the final temperature 6, the permissible maximum power decreases as the starting temperature 7, 8 is exceeded, suggesting to the driver that the electric drive 2 is approaching the final temperature 6 and the associated shutdown of the electric drive 2.

[0035] In the superheat map 5, the permissible maximum power decreases at constant temperature gradients with a continuous curve down to the final temperature 6. In an alternative exemplary embodiment, the curve of the permissible maximum power between the starting temperature 7, 8 and the final temperature 6 can be arbitrary. Such a curve of the permissible maximum power can be a linear curve, a concave curve, a convex curve, a logarithmic curve, or a step function curve. In one exemplary embodiment, the curve of the permissible maximum power can change at a constant temperature gradient between the corresponding starting temperature 7, 8 and the corresponding final temperature 6 depending on the temperature gradient.

[0036] In a further exemplary embodiment, the negative temperature gradients in the overheating protection characteristic map 5 are assigned the same starting temperatures 7, 8 as the positive temperature gradients, with the same amount of negative temperature gradients. Negative temperature gradients occur when the electric drive 2 cools down and the temperature of the electric drive 2 decreases. The overheating characteristic map also covers the case in which the temperature of the electric drive 2 has previously exceeded the end temperature and, after the electric drive is switched off, the temperature of the electric drive drops and falls below the end temperature. In an alternative exemplary embodiment, different starting temperatures 7, 8 are assigned to the negative temperature gradients in the overheating protection characteristic map 5 compared to the starting temperatures 7, 8 of the positive temperature gradients, with the same amount of negative temperature gradients.In a further exemplary embodiment, the negative temperature gradients in the overheating protection characteristic map 5 are assigned the same curves between the final temperature 6 and the associated starting temperatures 7, 8 as the positive temperature gradients, with the same absolute values ​​of the negative temperature gradients. In an alternative exemplary embodiment, the negative temperature gradients in the overheating protection characteristic map 5 are assigned different curves of the permissible maximum power between the final temperature 6 and the associated starting temperatures 7, 8 compared to the curves of the permissible maximum power between the final temperature 6 and the associated starting temperatures 7, 8 of the positive temperature gradients, with the same absolute values ​​of the negative temperature gradients.In an alternative embodiment, in the overheating protection map 5, the starting temperatures 7, 8 in the area of ​​the negative temperature gradients correspond to the end temperature 6, so that when the temperature falls below the end temperature 6 in the case of negative temperature gradients, the permissible maximum power corresponds to the maximum permissible maximum power. In a further embodiment of the overheating protection map 5, different end temperatures 6 are assigned to the negative temperature gradients than to the positive temperature gradients with the same magnitudes of the negative temperature gradients.

[0037] The overheating protection map 5 has different starting temperatures 7, 8 for different temperature gradients. Preferably, the overheating protection map 5 has the highest starting temperature 7 when no temperature gradient is present. The starting temperature 7, 8 decreases with increasing temperature gradients. With a constant higher temperature gradient, the temperature changes over time in a shorter time than with a lower temperature gradient. If the same starting temperature 7, 8 were provided for each temperature gradient in the overheating protection map 5, the time between the starting temperature 7, 8 and reaching the end temperature 6 would be significantly shorter with a constantly higher temperature gradient than with a constantly lower temperature gradient. The driver perceives such a shortening of the time between the starting temperature 7, 8 and the end temperature 6 with a constant temperature gradient as unpleasant.By reducing the starting temperature 7, 8 at a higher temperature gradient toward a lower temperature, the effect just described is compensated and the driver's perception is improved. In a preferred embodiment, the starting temperature 7, 8 is adapted to the temperature gradient such that the duration between the starting temperature 7, 8 and reaching the final temperature 6 is identical for each temperature gradient at a constant temperature gradient.

[0038] The overheating protection map 5 has the same final temperature at different temperature gradients. In an alternative embodiment, the final temperature 6 can vary depending on the temperature gradient. This allows a certain inertia in the heating of the electric drive 2 and the heating of the point at which the temperature of the electric drive 2 is measured to be taken into account. In an alternative embodiment, the final temperature 6 decreases with increasing temperature gradients. In one embodiment, the overheating protection map 5 comprises additional axes on which the battery charge state and / or the gradient of the path on which the electric bicycle 1 is located and / or the ambient temperature of the surroundings of the electric bicycle 1 are plotted.The starting temperature 7, 8 decreases with increasing ambient temperature and / or increasing gradient of the path on which the electric bicycle is traveling and / or with increasing ambient temperature. This allows for the consideration of other factors influencing the temperature of the electric drive 2 and their temporal changes.

Claims

Claims 1. A method for operating a drive (2) of an electric bicycle (1) with a determination of an overheating protection of the electric drive (2), comprising the steps: Receiving and / or reading out status data, wherein the status data comprises a temperature of the electric drive (2) and a temperature gradient of the electric drive (2); Receiving an overheating protection characteristic map (5) and / or reading the overheating protection characteristic map (5) from a memory, wherein the overheating protection characteristic map (5) indicates a permissible maximum power of the electric drive (2) as a function of the status data; Determining a permissible maximum power from the overheating protection map (5) using the status data, and - Output of a power which is at most the permissible maximum power of the electric drive (2).

2. Method according to claim 1, wherein in the overheating protection map (5) the permissible maximum power decreases with increasing temperature and / or increasing temperature gradient of the electric drive (2).

3. Method according to one of the preceding claims, wherein in the overheating protection characteristic map (5) the permissible maximum power drops from a starting temperature (7, 8) and above and does not drop further from an end temperature (6), wherein the end temperature (6) is greater than the starting temperature (7, 8).

4. Method according to claim 3, wherein in the overheating protection map (5) the permissible maximum power assumes the value zero from the final temperature (6) and above. Method according to claim 3 or 4, wherein in the overheating protection characteristic map (5), the starting temperature (7, 8) decreases with increasing temperature gradients and the starting temperature (7, 8) increases with decreasing temperature gradients. Method according to one of the preceding claims 3 to 5, wherein in the overheating protection characteristic map (5), the starting temperature lies between a first starting temperature limit value (7) and a second starting temperature limit value (8), wherein the first starting temperature limit value (7) is not equal to the second starting temperature limit value (8). Method according to one of the preceding claims, wherein the state data comprise a battery charge state of an electrical energy store (3) of the drive (2) of the electric bicycle (1). Method according to one of the preceding claims, wherein the state data comprise a gradient of the path on which the electric bicycle (1) is located and / or a GPS position of the electric bicycle (2).Method according to one of the preceding claims, wherein the status data comprise weather information, in particular an ambient temperature. Drive of an electric bicycle (1) comprising:. - a control unit, wherein the control unit is configured to carry out a method according to one of the preceding claims. An electric bicycle (1) with a drive according to claim 10.

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