EP1971766A2

EP1971766A2 - Method for determining a speed signal of an electric machine

Info

Publication number: EP1971766A2
Application number: EP06827961A
Authority: EP
Inventors: Carsten Kaup; Thomas Pels
Original assignee: AVL List GmbH
Current assignee: AVL List GmbH
Priority date: 2006-01-10
Filing date: 2006-12-21
Publication date: 2008-09-24
Also published as: WO2007079511A3; WO2007079511A2

Abstract

The invention relates to a method for determining a speed signal (8) of an electric machine (1) which is mechanically connected to an internal combustion engine (2). The speed signal (8) is determined by means of an incremental speed sensor (4) and the speed is determined from the time measured when the speed sensor passes over a reference angle (a) of a rotating part, the reference angle being preferably defined by at least two flanks of a gearwheel (5). In order to avoid oscillating torques, the reference angle (a) is modified depending on at least one operating or engine parameter.

Description

Method for determining a speed signal of an electrical machine

The invention relates to a method for determining a speed signal of an electrical machine which is mechanically connected to an internal combustion engine, wherein the speed signal is determined by means of an incremental speed sensor and the speed is determined from the measured when sweeping a reference angle of a rotating part, wherein preferably the reference angle is defined by at least two flanks of a gear. Furthermore, the invention relates to a method for performing test stand-bound, vehicle cycle-consistent vehicle tests, wherein the vehicle is operated within an allowable speed and / or speed bandwidth of a drive cycle. Furthermore, the invention relates to a serial hybrid drive system for a vehicle, with an internal combustion engine, at least one associated with this first electric machine, which is connected to a storage unit, and at least one connected to the storage unit second electric machine, which at least on a drive wheel of the vehicle acts.

The rotational speed characteristic of internal combustion engines, due to the rotational nonuniformity of the internal combustion engine, contains harmonics, for example, second and fourth order in a 4-cylinder engine. If a highly dynamic input signal is used for the speed control of an electrical machine, high-frequency alternating torques occur when the target value is reached, which can cause disturbing vibrations, noises and hum.

For driving legally prescribed consumption and emission cycles, a test stand driver or bench-top robot is usually used, which follow predetermined driving cycles within a predetermined tolerance band.

The measured consumption and emission values are to a considerable extent influenced by the transient behavior of the internal combustion engine, especially during load changes with relatively steep gradients. As a result, on the one hand, different permissible measurements within the tolerance band deviate greatly from each other and, on the other hand, the measurement result is only sub-optimal even with 100% follow-up of the given speed and speed characteristics. Serial drive systems usually have an internal combustion engine whose crankshaft is connected to a first electric machine. Power is generated by the first electric machine and stored temporarily in a memory unit. The drive of the vehicle via a second electric machine, which obtains the drive energy from the storage unit. Since the internal combustion engine is operated intermittently, a separate drive of the ancillaries is required. The ancillary units are driven by further electrical machines, which draw power from the storage unit. In this case, an electric machine is usually provided per accessory. By the electric drive of the ancillaries they can be operated even when the internal combustion engine. The disadvantage is that due to the many individual components of the effort for the hybrid drive system is relatively high. In addition, a relatively large volume of construction is claimed. The number of items also adversely affects the weight of the building. Another disadvantage is that due to conversion losses the overall efficiency is relatively poor.

The object of the invention is to avoid these disadvantages and to reduce high-frequency alternating torques. Another object of the invention is to improve fuel economy and emissions during the driving cycles. It is another object of the invention is to reduce the design effort in a serial hybrid drive system. Furthermore, the volume and weight should be reduced and the overall efficiency improved.

According to the invention, this is achieved by changing the reference angle as a function of at least one operating or engine parameter.

Preferably, it is provided that a larger reference angle is selected in operating areas with high Drehun- uniformities, as in operating areas with lower rotational nonuniformities. Another parameter for the selection of the reference angle can be the required dynamics of the speed control. In the steady state, a larger reference angle is selected than in transient processes. Based on decision logic, the rotational angle used for the calculation is increased. The calculated speed corresponds to the mean value above the reference angle.

To improve the fuel consumption and emission values during the driving cycles, it is provided that within the tolerance band the consumption and / or emission-optimal speed and / or engine speed range is determined and the vehicle is operated in this optimum speed and / or engine speed range. The gradients during load changes are essential reduced. The vehicle can be operated by a test stand driver or a driving robot.

It is particularly advantageous if the driver is visually, acoustically and / or tactually displayed a deviation of the actual speed and / or the actual speed from the optimum speed and / or speed range. In this case, for example, the ideal line for the speed and / or the speed, and the actual value of the speed and / or the speed can be displayed on a display device, so that the test stand driver can easily drive the consumption or emission-optimal operating range within the tolerance band of the drive cycle ,

A low design effort can be achieved if the first electric machine is connected to at least one auxiliary unit. The electric machine thus drives the accessory directly mechanically. This has the advantage that a high overall efficiency can be achieved by the mechanical drive.

It is preferably provided that a separating means, preferably a clutch or a freewheel device, is arranged between the internal combustion engine and the first electric machine. As a result, the ancillaries can be driven even when the internal combustion engine.

As ancillaries pumps or compressors for power steering equipment, air conditioning or vacuum pumps can be used.

In this case, several auxiliary units can be driven by the single first electric machine.

During operation of the internal combustion engine, the first electric machine is driven via the crankshaft and generates electrical energy. At the same time, the auxiliary units are driven by the first electric machine towed by the internal combustion engine. If the internal combustion engine is turned off, the separating means is used to interrupt the drive train between the internal combustion engine and the first electric machine. The first electric machine is operated by a motor, wherein it receives the drive energy from the storage unit. Thus, an undisturbed operation of the ancillaries is guaranteed even when the engine is switched off. Since the ancillaries can always be driven at a constant speed, they can always work at the optimum design point. The adjustment of the sometimes different optimal speeds via the belt ratios, or spur gears between the electric machine and the ancillaries. _ A _

The invention will be explained in more detail below with reference to FIGS. Show it:

1 shows the method according to the invention in a schematic representation;

Fig. 2 is a speed-time diagram;

3 is a speed-time diagram of a drive cycle;

4 shows an optical display for the optimum line; and

Fig.5 is a serial hybrid propulsion system for a vehicle.

As shown in FIG. 1, an electric machine 1 is mechanically fixedly connected to an engine 2. The rotational speed measurement of the crankshaft 3 takes place via an incremental rotational speed sensor 4 and a measuring gearwheel 5. The rotational speed sensor 4 delivers a TTL signal 6 to a rotational speed calculation unit 7 which has an edge counter 7a, a timer 7b and a summer 7c. By the speed calculation unit 7, a speed signal 8 is generated, which serves as an actual value for the speed control.

The speed controller 9 forms due to the difference between the desired value 10 and the actual value forming a speed signal 8, a control value 11, which is supplied by a pulse width modulator 12 of the electric machine 1 as a pulse width modulated signal.

In the speed calculation with the aid of incremental sensors 4, the instantaneous speed actual value results from the measured time between two flanks and the gear geometry of the gear 5. Thus results, for example, in a donor wheel geometry with 60 teeth (120 flanks) and a measured time of 0.625 ms, an engine speed of 800 min ^'1. as a basis for the speed calculation. serves a rotation angle of 3 ° (360 ° / 120) the speed profile versus time, in internal combustion engines, significant rotational irregularities, called harmonics, as shown in Fig. 2 For example, in a 4-cylinder engine, 2nd and 4th order harmonics result, and the smaller the reference angle α, or the higher the number of teeth of the measuring gear 5, the higher the resolution of the calculated rotational speed n.

If a highly dynamic input signal is used for the speed control of an electrical machine, high-frequency alternating torques occur when the target value is reached, which are generally in antiphase to the rotational irregularities. The calculated speed is indicated in Fig. 2 by the step line rti. High frequency alternating moments are perceived as vibration or acoustically. - -

By increasing the measuring interval, in particular the reference angle α of the measuring gear 5, it can be avoided that the actual value 8 follows for the rotational speed, the irregularities of the rotational speed. For the calculation, therefore, the base reference angle α is increased.

For this purpose, the measured times are summed up to a reference angle α, which corresponds to a nonuniformity period p of the harmonics or the nonuniformities. In a 4-cylinder engine, the period p corresponds to a reference angle α of about 180 °, ie half a crankshaft revolution. In other internal combustion engines, different reference angles result.

In the concrete example with a measuring gear 5 with 60 teeth, the reference angle α extends over a range of 30 teeth (60 flanks). With each new edge, a new time value is added and the oldest one is subtracted. The speed n calculated in this way corresponds to the mean value of half a revolution and contains no second or fourth order torsional vibration components.

The decision as to which speed signal 8 is supplied to the controller 9 as the actual value may depend on various parameters, such as the operating mode (engine start, shift, acceleration, etc.), the engine load or the desired dynamics.

A deliberately increased reference angle α as the basis for the speed calculation offers the advantage that the harmonics are eliminated. A speed control on the basis of this reference signal does not contain any harmonics caused by harmonics.

In Fig. 3, the speed v over the time t of a typical driving cycle for collecting the consumption and the emissions of a vehicle is shown schematically. The test stand driver has the task of following the driving cycle 101 within a tolerance band indicated by reference numeral 102. Within this tolerance band 102, however, there is an operating line 103 at which consumption and / or emissions become minimal. Depending on how far the vehicle is operated away from this optimum line 103, lower or higher fuel consumption and / or emission values result. If the test stand driver or the driving robot operates the vehicle as close as possible to the optimum line 103, the best fuel consumption and / or emission values can be achieved.

In order to improve the repeatability of the driven driving cycle and to facilitate the test stand driver to follow the optimal line 103, a display device 104 shown in FIG. 4 is provided, which is a section of the Drive cycle 101, including tolerance band 102 and the optimal line 103 displays. Furthermore, the instantaneous operating point 104 is displayed, so that the test bench driver can immediately recognize whether an acceleration or deceleration of the vehicle is required.

FIG. 5 shows an internal combustion engine 201, which is connected to a first electric machine 203 via a crankshaft 202. Between the internal combustion engine 201 and the electric machine 203, a separating means in the form of a switchable coupling 204 is arranged. Instead of the switchable coupling 204 may also be provided a freewheel device and / or a centrifugal clutch. The first electric machine 203 is electrically connected to a storage unit 205, for example an electrochemical storage.

The hybrid serial drive system further includes at least a second electric machine 206, which is also connected to the storage unit 205. The second electric machine 206 is connected directly or via a transmission with at least one drive wheel 207.

The first electric machine 203 is mechanically connected to one or more accessories 208.

During operation of the internal combustion engine 201, this drives the first electric machine 203 via the crankshaft 202 and the closed clutch 204. The first electric machine 203 generates electricity and supplies it to the storage unit 205. In addition, the ancillaries 208 are driven by the internal combustion engine 201 via the generator-operated first electric machine 203.

If the engine 201 is turned off and an unrestricted drive of the ancillaries 208 is required, the clutch 204 is disconnected and the first electric machine 203 is switched to motor operation. In this case, the first electric machine 203 withdraws power from the storage unit 205 and now drives the ancillaries 208 as a motor. The drive of the ancillaries 208 can be done for example via a traction means, such as a V-ribbed belt, or gears.

By driving the ancillaries 208 via the first electric machine, the system costs can be significantly reduced, since only a single electric machine is required to drive the ancillaries 208, which is already part of the drive system (dual use). Furthermore, there are energetic advantages in terms of consumption reduction, since the translations of the ancillaries (belt ratios) in the serial hybrid can be tuned very well for optimum efficiency. The burning In this case, the engine 201 is essentially operated at a single rotational speed. Further advantages are that the construction volume and the construction weight can be considerably reduced.

Claims

- PATENT APPLICATIONS

1. A method for determining a speed signal (8) of an electric machine (1), which is mechanically connected to an internal combustion engine (2), wherein the speed signal (8) by means of an incremental speed sensor (4) and determines the speed of the when sweeping a Reference angle (α) of a rotating part is determined, wherein preferably the reference angle is defined by at least two flanks of a gear (5), characterized in that the reference angle (α) is changed in dependence on at least one operating or engine parameter.

2. The method according to claim 1, characterized in that in operating areas with high rotational irregularities, a larger reference angle (α) is selected, as in operating areas with lower rotational irregularities.

3. The method according to claim 1 or 2, characterized in that in operating areas with steady state, a larger reference angle (α) is selected, as in operating areas with transient processes.

4. A method for performing test stand-bound, vehicle cycle-consistent vehicle tests, wherein a vehicle within an allowable speed and / or speed range of a driving cycle (101) is operated, characterized in that within the tolerance width (102) of the consumption and / or emission-optimal Speed and / or speed range is determined and the vehicle is operated in this optimal speed and / or speed range.

5. The method according to claim 4, characterized in that the vehicle is operated by a driving robot.

6. The method according to claim 4, characterized in that the vehicle is operated by a test stand driver.

7. The method according to claim 6, characterized in that the test stand driver is displayed visually, acoustically and / or tactually a deviation of the actual speed and / or the actual speed from the optimum speed and / or speed range.

8. The method according to claim 7, characterized in that on a display device (104), the ideal line (103) for the speed and / or Speed, as well as the actual value of the speed and / or the speed is displayed.

9. A hybrid serial drive system for a vehicle, comprising an internal combustion engine (201), at least one first electric machine (203) connected thereto, which is connected to a memory unit (205) and at least one to the memory unit (205 ) connected second electric machine (206), which acts on at least one drive wheel (207) of the vehicle, characterized in that the first electric machine (203) with at least one auxiliary unit (208) is connected.

10. hybrid drive system according to claim 9, characterized in that between the internal combustion engine (201) and the first electric machine (203) a release agent, preferably a clutch (204) or a freewheel device is arranged.

11. Hybrid drive system according to claim 9 or 10, characterized in that the IMebenaggregat (208) is a pump or a compressor for a power steering system, an air conditioning device or a vacuum pump.