SE1050761A1 - Energy control system and method for a hybrid vehicle - Google Patents

Description

energy to an electric motor that moves the vehicle. When large quantities of energy are needed, the engine takes energy from both the battery and the generator.

In parallel hybrid vehicles, the internal combustion engine and an electric machine, which are used both as a generator and an engine, are mechanically connected via an engine shaft. An example of a parallel hybrid system is shown in Figure 2. The coupling can be placed between the internal combustion engine and the electric machine, which makes it possible to drive the vehicle only electrically. Since the internal combustion engine and the electric motor rotate at exactly the same speed (when the clutch is switched on), they complement each other and work in parallel.

When hybrid systems are to be implemented for buses, a series hybrid system is often used. A city bus makes many decelerations to stop per day.

An important aspect for saving energy is to make the most of the energy regenerated during deceleration. In order to be able to receive the regenerated energy, there must be room in the energy storage.

This means that the energy level in the energy storage should be reduced in good time before braking begins.

According to the systems used today, you do not know how long / distance it is to the next stop and then it may happen that you discharge the energy storage too slowly, which means that you do not have time to make room for the energy that is expected to enter the energy storage during the next deceleration. . When accelerating according to the driving technique that is often used today, the energy storage is emptied quickly, which results in the internal resistive losses becoming large. One reason for this is that you want to be sure that the energy storage is at a predetermined low level when a future deceleration phase is to begin, ie. so that there is sufficient storage space for the energy generated then.

For buses, so-called supercapacitors for energy storage. The advantage of a capacitor in front of a battery is that it can withstand a large number of repeated discharges in a short time, which is often applicable to buses.

For an energy storage (capacitors, batteries, etc.) generally applies: U = CXQ where U is voltage, C capacitance and Q charge. 10 15 20 25 30 P = U X I where P is the power and I is the current.

Pm = R X 12 where Ploss is the power loss in the energy store and R the internal resistance.

Thus, the power losses of the energy store increase by the square of the current, which means that a large current outlet, e.g. during an acceleration phase, is negative from an energy perspective.

The following patent documents relate to various systems and devices in the field of energy regeneration for hybrid vehicles.

US-6,414,401 relates to a control system for regenerating energy in a hybrid vehicle so that sufficient energy can be stored during regeneration during deceleration of the vehicle.

US-2007/001 8608 relates to a device for controlling the charging of a battery in a hybrid vehicle in order to be able to limit the amount of charge which charges the battery during the regeneration phase. US-7,242,159 also relates to a device for controlling the charging of battery and / or capacitors in a hybrid vehicle.

An object of the present invention is to provide an improved and more optimal energy use for a hybrid vehicle, especially to keep down the internal resistive losses in the capacitors / batteries.

Summary of the Invention The above object is achieved by the invention defined by the independent claims.

Preferred embodiments are defined by the dependent claims.

The invention relates to an energy control system for a hybrid vehicle with at least one electric machine and an internal combustion engine and at least one rechargeable energy storage, the system 10 comprising a control unit and a charge level meter adapted to measure the charge level of the energy storage. The control unit comprises a calculation unit which is adapted to calculate, at a time t0, inter alia based on the current speed and the weight of the vehicle, a time t1 which indicates the start of a deceleration phase during which the vehicle is braked to stop at a predetermined position P, adapted to control the extraction of energy from the energy storage during the time period to to t1 so that the charge level of the energy storage at time t1 is below a predetermined low charge level QL.

The invention also refers to a method in an energy control system for a hybrid vehicle where the system comprises a control unit and a charge level meter adapted to measure the charge level of the energy storage. The method comprises: A) calculating, at a time to, inter alia based on the current speed and the weight of the vehicle, a time t1 indicating the start of a deceleration phase during which the vehicle is braked to stop at a predetermined position P, B) controlling the withdrawal of energy from the energy storage during the time period to11 so that the charge level of the energy storage at time t1 is at a predetermined low charge level QL- According to an important aspect of the invention, the distance to the next stop is calculated or determined, for example from the bodybuilder / operator's exclamation system. a so-called bus PC system or similar system, alternatively the distance is calculated with the help of information from the bus PC about how far it is between the two current bus stops. Information from GPS or similar could also be used.

With the use of the present invention, it will be possible to lower the energy storage level faster or differently than one would otherwise have chosen to do, in front of a bus stop to accommodate the part of the vehicle's kinetic and positional energy which one expects to want to enter. energy stored.

Thus, by knowing the distance to the next planned stop at the stop and the speed of the vehicle, one can calculate when the deceleration phase begins. This also knows when the charge level must be down to a predetermined low level. That a stop at a stop 10 15 20 25 30 5 really happens is only known when someone presses the stop button and it is at this time that the calculations are made.

Brief description of the drawing Figure 1 schematically illustrates a series hybrid system for a vehicle.

Figure 2 schematically illustrates a parallel hybrid system for a vehicle.

Figure 3 is a block diagram illustrating the present invention.

Figure 4 is a fate diagram illustrating the present invention.

Figure 5 is a timing chart illustrating the present invention.

Detailed Description of Preferred Embodiments of the Invention Referring to Figure 3, which shows a block diagram illustrating the present invention, this will now be described in detail.

The invention thus relates to an energy control system for a hybrid vehicle, wherein the hybrid vehicle comprises at least one electric machine, at least one internal combustion engine and at least one rechargeable energy storage.

The hybrid vehicle can be a series or parallel hybrid system or a combination of these.

The energy control system comprises a control unit, and a charge level meter adapted to measure the charge level of the energy storage.

The control unit in turn comprises a calculation unit which is adapted to calculate, at a time to, inter alia based on the current speed and the weight of the vehicle, a time t1 which indicates the start of a deceleration phase during which the vehicle is braked to stop at a predetermined position P ( see Figure 5).

Figure 5 is a timing chart illustrating the present invention. At the top of Figure 5, a vehicle, in this case a bus, is shown, which is located between the stops PA and PB.

Then there are two time diagrams showing how the charge level Q for the energy storage varies for the vehicle along the distance shown at the top of the figure. The top time diagram schematically illustrates how the charge level varies according to a currently common model, while the bottom time diagram illustrates how the charge level varies for the energy storage in a vehicle using the energy control system according to the present invention.

During the deceleration phase (RET.) The charge level is raised from a low level QL, in which the figure is approx. 25% of maximum charge level, using the energy regenerated. This part of the charge curve corresponds to the two cases shown. During the acceleration phase (ACO), the charge level can, for example, be lowered according to what is illustrated in the top time diagram, ie. there is a high energy withdrawal from the energy storage.

In order to reduce the internal losses of the energy storage, the control unit, according to a preferred embodiment, is adapted to control the energy withdrawal from the energy storage during acceleration phases of the vehicle so that the internal losses of the energy storage are minimized. This is illustrated in the bottom diagram in Figure 5 in that the charge level between P A and Al (denoting the end of the acceleration phase) remains at a high level.

At time two, the calculation unit receives an indication that the vehicle is to stop at position PB. The indication can, for example, consist of someone pressing the stop button in the bus and a stop signal is generated which is applied to the control unit.

The calculation unit then calculates, as mentioned above, based on the current speed and the weight of the vehicle, among other things, a time t1 which indicates the start of a deceleration phase during which the vehicle is braked to stop at a predetermined position P and that the control unit is adapted to control energy withdrawal from energy storage. during the time period to to t1 so that the charge level of the energy storage at time t1 is below a predetermined low charge level QL. This is clear from the bottom figure where the charge level drops to a low level QL.

According to one embodiment, the low charge level QL is in the range of 20-35% of the maximum charge level of the energy storage. A preferred level is 25% which is also indicated in Figure 5.

During the time period up to the beginning of the deceleration phase, at position A2, withdrawals from the energy storage are prioritized so that the charge level is lowered to the low charge level QL. This is done primarily by using the electric machine to drive the vehicle, but the energy can also be used for other purposes, for example it may be more advantageous to run auxiliary systems, etc. during that period.

According to a preferred embodiment, the control unit is adapted to control the energy output during acceleration phases of the vehicle so that energy output from the internal combustion engine is prioritized over energy output from the electric machine.

According to a further preferred embodiment, the control unit is adapted to control the energy withdrawal from the energy storage during the acceleration phase of the vehicle so that low energy withdrawal from the energy storage takes place and that the charge level at the end of the acceleration phase is above a predetermined high charge level QH.

According to one embodiment, the predetermined high charge level QH is in the range of 70-100% of the maximum charge level of the energy storage. A preferred level is 80% which is also indicated in Figure 5.

During the deceleration phase, the energy storage is then charged.

The percentages levels for QL and QH are difficult to specify with values because they depend on the current speed, weight, energy storage size of the vehicle and the performance of the hybrid components.

For a vehicle where the energy storage size and performance are constant, the current speed and weight still remain in the determination of QL and QH.

For example. if the vehicle is accelerated up to a speed x, we must ensure that there is room in the energy storage for the kinetic energy that is possible to regenerate when the driver starts his fueling to a stop. If the speed is increased to 2x, the kinetic energy is increased by a factor of 4 and thus more space is needed in the energy storage when the driver starts his braking to a stop. However, it is not a given that there is 4 times as much space we should have in the energy storage because components can be power-limited so that we do not have the opportunity to regenerate all extra kinetic energy.

In a case where the energy stock is rather small, this means that the percentage limits change quickly with e.g. changed speed. Even with a deceleration from 40 km / h, it is required that the energy level 10 15 20 25 30 is about 25% in order for us to be able to take care of all energy that can be regenerated. If the speed "only" is 20 krn / h, which is not an unreasonable cruising speed for a city bus in heavy city traffic, according to the reasoning above the kinetic energy is only a quarter of the kinetic energy at 40 krn / h. In these cases, the limit for QL is rather 80% because there is no more energy that can be regenerated during braking. If the energy storage level would then be 25%, we are far too low and the energy storage level would be about 40% when the vehicle was stationary.

The intervals that have been stated for QL and QH are to be regarded as preferred examples given for illustrative purposes, but in general it applies that QL and QH are calculated on the basis of e.g. vehicle speed resp. the vehicle mass according to the above reasoning.

The control unit comprises, according to a preferred embodiment, a memory unit in which predetermined positions for vehicle stops, e.g. stops, are stored, for example in the form of an electronic map. The position of the vehicle in relation to the stops can then be easily determined since the time and speed of the vehicle are known. Alternatively, different types of positioning systems can be used, e.g. GPS, where the vehicle's current position, obtained via GPS, can be mapped to an electronic map image, and the distance to the next stop can then be calculated.

As mentioned above, the energy storage, preferably of one or more capacitors, is often used so-called supercapacitors.

The invention also comprises a method in a system for a hybrid vehicle with an electric machine, an internal combustion engine and a rechargeable energy storage, the system comprising a control unit, and a charge level meter adapted to measure the charge level of the energy storage.

Referring to Figure 4, the method comprises: A) calculating, at a time to, based inter alia on the current speed and the weight of the vehicle, a time t1 indicating the start of a deceleration phase during which the vehicle is braked to stop at a predetermined position P, B) controlling the withdrawal of energy from the energy storage during the time period to1 to t1 so that the charge level of the energy storage at time t1 is below a predetermined low charge level QL.

According to a variant, step A is performed if a stop signal has been received which indicates a request for the vehicle to stop. The calculation performed in step A is preferably made continuously, ie not as a consequence of, for example, a keystroke and the value of t1 is used, which is present at the keystroke, ie. at time two.

Then the energy storage is charged during the deceleration phase.

Furthermore, preferably, the energy withdrawal from the energy storage is controlled during an acceleration phase of the vehicle so that the internal losses of the energy storage are minimized. This can be done, for example, by, during an acceleration phase, controlling the energy output of the vehicle so that energy output from the internal combustion engine is prioritized over energy output from the electric machine. More specifically, this can be done by controlling the energy withdrawal from the energy storage so that low energy withdrawal from the energy storage takes place during the acceleration phase and that the charge level at the end of the acceleration phase is above a predetermined high charge level QH.

In the following, an example of an application of the present invention is given, inter alia, with reference to Figure 5.

One of the bus stops in Figure 5 is at position PB. Assume that the driver brakes fairly evenly at all decelerations to a stop and that the minimum limit for normal decelerations is given by the A2, ie. at the earliest at that position, the vehicle must start braking in order for the braking to meet the requirements for passenger comfort. There is a maximum permitted deceleration during the deceleration phase which has been determined, among other things, with regard to driver and passenger comfort. This is approximately in the order of 2 m / sz.

With the deceleration limit as above, the minimum expected distance from the start of firing to a stop can be calculated for the current speed, ie. the distance the bus has time between to and t1. The time you have to make room for more energy, ie t1-t0, then the distance that remains is divided by the current speed. 10 15 20 10 The advantage of the solution according to the invention is that in certain driving cases you can save more fuel by cycling more energy out of the energy storage. By knowing how long it is until the braking before a stop starts, you know better how much time you have to make room for the energy. Even if the stop button is not pressed, the calculations are preferably performed so that the extraction of energy takes place in such a way that the charge level is at a predetermined low level when a deceleration may begin, for example when there are people at the stop who are to take the bus.

With a changed driving strategy during the acceleration phase, which means that during the acceleration phase you do not use the energy storage to the maximum but instead let the combustion engine work, the internal power losses in the energy storage (capacitor / battery) will be lower compared to the case when the electric machine is used during the acceleration phase. a more energy efficient system is achieved.

The present invention is not limited to the above-described preferred embodiments.

Various alternatives, modifications and equivalents can be used. The above embodiments are therefore not to be construed as limiting the scope of the invention as defined by the appended claims.

Claims (15)

10 15 20 25 30 ll Claims Energy control system for a hybrid vehicle with at least one electric machine and an internal combustion engine and at least one rechargeable energy storage, the system comprising a control unit, and a charge level meter adapted to measure the charge level of the energy storage, characterized in that the control unit comprises a calculation unit adapted to a time to, inter alia based on the current speed and weight of the vehicle, a time t1 indicating the start of a deceleration phase during which the vehicle is braked to stop at a predetermined position P, the control unit being adapted to control the withdrawal of energy from the energy storage during the period to to t1 so that the charge level of the energy store at time t1 is below a predetermined low charge level QL. Energy control system according to claim 1, wherein the control unit is adapted to receive a stop signal indicating a request that the vehicle should stop and that the calculation of the time t1 takes place when the stop signal has been received. Energy control system according to claim 1 or 2, wherein the control unit is adapted to control the energy withdrawal from the energy storage during an acceleration phase of the vehicle so that the internal losses of the energy storage are minimized. Energy control system according to any one of claims 1-3, wherein the control unit is adapted to control the energy extraction during an acceleration phase of the vehicle so that energy extraction from the internal combustion engine is prioritized over energy extraction from the energy storage. Energy control system according to any one of claims 1-4, wherein the control unit is adapted to control the energy withdrawal from the energy storage during an acceleration phase of the vehicle so that low energy withdrawal from the energy storage takes place and that the charge level at the end of the acceleration phase is above a predetermined high charge level QH. Energy control system according to any one of claims 1-5, wherein the energy storage is charged during the deceleration phase. An energy control system according to any one of claims 1-6, wherein the control unit comprises a memory unit where predetermined positions for vehicle stops are stored, An energy control system according to any one of claims 1-7, wherein said energy storage comprises one or more capacitors. A system according to any one of claims 1-8, wherein said predetermined low charge level QL and high charge level QH are calculated from e.g. vehicle speed and vehicle mass. Method in an energy control system for a hybrid vehicle with an electric machine, an internal combustion engine and a rechargeable energy storage, the system comprising a control unit, and a charge level meter adapted to measure the charge level of the energy storage, characterized by the method comprising calculating, at a time to, based on the current speed and the weight of the vehicle, a time t1 indicating the start of a deceleration phase during which the vehicle is braked to stop at a predetermined position P, B) controlling the withdrawal of energy from the energy storage during the period to to t1 so that the charge level of the energy storage t1 is below a predetermined low charge level QL. The method of claim 10, wherein step A is performed if a stop signal is received indicating a request for the vehicle to stop. A method according to claim 10 or 11, wherein the energy withdrawal from the energy storage during an acceleration phase of the vehicle is controlled so that the internal losses of the energy storage are minimized. Method according to claim one of claims 10-12, wherein the energy extraction during an acceleration phase of the vehicle is controlled so that energy extraction from the internal combustion engine is prioritized over energy extraction from the energy storage. A method according to any one of claims 10-13, wherein the energy withdrawal from the energy storage during an acceleration phase of the vehicle is controlled so that low energy withdrawal from the energy storage takes place 13 and that the charge level at the end of the acceleration phase is above a predetermined high charge level QH. A method according to any one of claims 10-14, wherein the energy storage is charged during the deceleration phase.