DE102015201904A1 - Method for operating a hybrid vehicle - Google Patents

Abstract

In a method of operating a hybrid vehicle in which an actual operating strategy is exited from sailing the hybrid vehicle, controlled by operation of a brake pedal, and closing a powertrain of the hybrid vehicle, it is provided to check whether by a driveline closure reduction required time can be improved by the use of electrical support an energy value to be achieved by the recuperation and if this is the case to use the electrical support.

Description

The invention relates to a method for operating a hybrid vehicle, in which a current operating strategy controlled by the operation of a hybrid brake pedal, left and closing a drive train of the hybrid vehicle, and wherein after closing the drive train kinetic energy of the hybrid vehicle used for recuperation becomes. Furthermore, the present invention relates to a computer program which is set up to carry out each step of the method according to the invention and to a machine-readable storage medium on which the computer program according to the invention is stored. In addition, the invention relates to an electronic control unit which is set up to operate a hybrid vehicle by means of the method according to the invention.

State of the art

Electronic clutch systems automate the drive train of a vehicle with manual transmission and dry friction clutch. The detection of the pedal travel of the clutch pedal is realized in these systems via a sensor which generates an electronic control signal which is transmitted to the engine control unit. The engine control unit calculates a desired position of the clutch from this control signal and communicates with the actuator, for example via a CAN bus installed in the vehicle.

Boost and Rekuperationssysteme for electrification of the drive train of a conventional vehicle, for example, operate on a voltage basis of 48 volts. Such a system includes an air-cooled electric machine, also referred to as e-machine with integrated electronics (BRM Boost recuperation machine), which have outputs up to 10 kW and a lithium-ion battery. Furthermore, such systems are equipped with so-called DC / DC converters for power transmission to the conventional 14 volt electrical system. These systems enable recuperation and traction as well as the supply of potential high-power electrical consumers through the 48-volt on-board electrical system.

In hybrid vehicles, in which the electric motor is installed, for example, instead of an alternator and directly coupled to the engine by means of a belt, the propulsion can only take place electrically, if the injection is hidden in the engine and the electric motor, the drag torque of the engine overcomes. Since these electric motors coupled directly to the internal combustion engine usually have only low powers, this operation can only be carried out at low speeds, for example when starting up.

If the driver leaves all the accelerator pedals while driving, usually the injection of fuel into the internal combustion engine is hidden and the vehicle is decelerated by the air resistance, rolling resistance and dragging of the internal combustion engine. To reduce the delaying resistances of the vehicle and thus to prolong the rolling phase of the vehicle, opening of the drive train in the case of manual transmissions by opening the clutch is provided by means of an operating strategy "sailing". In this operating strategy, the rolling distance of the vehicle is significantly increased and thus ultimately saved fuel. Since the powertrain is open during the sailing phase, the internal combustion engine can either be idled or shut down.

In a brake pedal operation during sailing, a so-called Schubeinkuppeln is realized in which the internal combustion engine is brought to a target speed only by closing the electronic clutch. Subsequently, the slip is removed until the coupling can be completely closed afterwards. During the entire process, no fuel is injected and the engine is spin-accelerated only by the kinetic energy of the vehicle and brought to the target speed.

In order to maintain the comfort for the driver in this context, the transmitted torque of the clutch must be kept relatively low, otherwise an excessive deceleration of the vehicle would be the result. Depending on the transmission input speed and depending on the strength of the brake pedal operation, this process takes several seconds.

For a vehicle without the ability to recover energy, the time until the powertrain closes is a matter of comfort and does not entail any energy disadvantages. However, if the vehicle has an electric motor in the drive train directly coupled to the internal combustion engine, with which the energy can be partially recovered by recuperation when the brake pedal is actuated, a conflict between comfort and possible recuperation occurs during thrust coupling.

If there is the possibility of energy recovery, the removal of the energy for hauling the engine out of the vehicle is basically negative, as this energy can not be recovered. The process also takes for comfort reasons For a long time, the air resistance of the vehicle loses additional energy during this time, which can no longer be recuperated. Nevertheless, the Schubeinkuppeln should run without the use of the internal combustion engine or without fuel consumption, since the driver only operates the brake.

Disclosure of the invention

The inventive method is used to operate a hybrid vehicle, in which a current operating strategy sailing the hybrid vehicle is left controlled by an operation of a brake pedal and closing a drive train of the hybrid vehicle and wherein after closing the drive train kinetic energy of the hybrid vehicle is used for recuperation. It uses the electric motor coupled directly to the combustion engine as well as an electronic clutch system, which is already required for standard push-coupling without an electric motor.

In the event that it is determined as a result of a test that a reduction of a time required to close the drive train by using an electrical support can be improved by the recuperation energy value can be improved according to the invention, the use of electrical assistance. The essence of the invention is based on the fact that the conflict between recuperation and comfort during the Schubeinkuppelns is solved, that for each Schubeinkuppelvorgang a balance from a required energy use for a procedure accelerated Schubeinkuppeln and then expected energy gain is calculated and by means of this balance a decision about the use of accelerated Schubeinkuppelns done. This is the best compromise between comfort and efficiency.

Due to the recuperation process, which starts earlier, it is generally possible to recover more energy than without the use of electrical assistance. But since this use consumes energy, a test is provided so that the energy use is compared to the energy gain. Only in the event that this test has a positive balance, the electrical assistance in the phase of Schubeinkuppelns is switched on. Otherwise, the thrust coupling takes place as usual in the prior art only by the use of the clutch.

It is advantageous to perform the closing of the drive train of the hybrid vehicle by means of an electronic clutch. Thus, the present method can provide an electrical signal by means of which the clutch can be controlled.

It is also advantageous if the electrical support is effected by means of an electric motor of the hybrid vehicle. The e-machine is already part of the hybrid concept of the vehicle and coupled for example by means of a belt directly to the internal combustion engine. Thus, the electric motor can adjust the speed of the internal combustion engine, if this injection is hidden. Task of the electric motor is to raise the speed of the engine in a short time to the transmission input speed such that a closing of the drive train by closing the electronic clutch is possible. This accelerated closing of the drivetrain allows the process of recuperation to begin sooner without any loss of comfort.

It is also advantageous if, in the test, whether the energy value to be achieved by the recuperation can be improved, a comparison of an energy value required for the electrical support, ie. H. an energy consumption, with an energy value to be expected from the earlier recuperation, d. H. an energy gain, takes place. In the event that the expected energy value is greater, the use of electrical support will take place.

It is advantageous to carry out the electrical assistance only in the case of a deflection of the brake pedal in a range equal to or less than a threshold value of, for example, 20 percent of the maximum deflection. If the brake pedal is pressed harder, the kinetic energy of the hybrid vehicle is reduced too much by the friction brake and is no longer available for recuperation. Thus, an energy balance determined by the method would be inaccurate.

It is also advantageous to provide information about the expected energy value and information about the energy value required for the electrical support in the form of digital characteristic data. These can easily be called up in the course of the procedure and used for comparison in a digital processing unit.

The computer program according to the invention is set up to carry out each step of the method according to the invention, in particular if it runs on a computing device or an electronic control device. It allows the implementation of the method according to the invention on a conventional electronic control unit, without having to make any structural changes thereto. For this purpose, it is on the machine-readable storage medium according to the invention saved. By loading the computer program according to the invention on a conventional electronic control unit, the electronic control unit according to the invention is obtained. This is set up to operate a hybrid vehicle by means of the method according to the invention.

Brief description of the drawings

Embodiments of the invention are explained in more detail in the following description.

It shows

1 a representation of an exemplary embodiment of a hybrid drive for a motor vehicle,

2 a representation of the algorithm according to the invention for slip control in a Schubeinkupplung with electrical assistance by the electric motor,

3 a representation of a comparison between measurements of the Schubeinkupplungsvorgangs with and without electrical assistance,

4 a graphical representation of the required energy E as a function of transmission input speed for assisting thrust engagement;

5 a representation of the recuperated energy E as a function of the speed difference between the starting and transmission input speed with a brake pedal actuation of 20 percent up to a speed of n _Veh = 1100 min ^-1 ,

6 a representation of the speed _losses n _loss as a function of the speed difference between the start and transmission input speed from the engine start to the closing of the drive train,

7 a representation of the total energy balance E as a function of the speed difference between the start and transmission input speed at an electrically assisted thrust clutch with a brake pedal actuation of 20 percent up to a speed of nVeh = 1100 min-1 and

8th a representation of the algorithm of the invention for the decision on the use of electrical support by the electric motor.

Embodiments of the invention

At the in 1 illustrated direct coupling between e-machine 2 and internal combustion engine 1 and automated powertrain of a hybrid vehicle, there is the possibility of the internal combustion engine 1 by means of the electric motor 2 To drive purely electrically and thus to realize a speed control with the drive train open, without providing the energy through combustion. This possibility is used to control the speed of the internal combustion engine 1 to the transmission input speed not with the clutch 3 and thus to perform the kinetic energy of the vehicle, but with the electric motor 2 and electrical energy.

In one embodiment of the method according to the invention energy is invested for a faster speed adjustment and thus a faster closing of the drive train to subsequently recover more energy than was used for it. For this purpose, a control must first make the speed adaptation as dynamic as possible and nevertheless not reduce the ride comfort. In this regulation, the various control components must be divided between the two torque drivers in the drive train (electric motor and clutch) so that the optimum compromise between comfort and dynamics is achieved.

It must be noted that the electrical support is provided by the electric motor 2 does not adversely affect the overall energy balance of the braking event to which the thrust engaging operation pertains. So it consumes energy in electrical form, the speeds of internal combustion engine 1 and gear 4 approach much faster and recuperate sooner.

The present method calculates with the help of provided electronic data in the form of characteristics, whether it makes sense at the current operating point of the hybrid vehicle to perform this support or not. Such characteristic data are determined for example by tests and stored, for example, in a central control unit such as the engine control. Nevertheless, it is important for the driving feel to carry out part of the regulation of the transmission input speed with the electronic clutch in order to achieve a deceleration of the vehicle, since this corresponds to the driver's request when the brake pedal is actuated.

In addition to the energetic advantage of the process, the dynamics of the Schubeinkuppelvorgangs by the support of the electric motor 2 improves, as the clutch and thus the drive train is closed faster and thus so-called "change of mind" cases can be better avoided. In these cases comes in a period of time in which the internal combustion engine 1 with regular overrunning clutch for two to four seconds from the clutch to transmission speed is a request for further operation or start of the internal combustion engine 1 , Since the drag time is much shorter with electrical assistance, this case occurs much less frequently.

The 1 shows an exemplary embodiment of a hybrid drive in a motor vehicle. The hybrid drive includes an internal combustion engine 1 and an electric machine 2 , which are directly connected to each other in the example by means of a belt. Between the combustion engine 1 and a gearbox 4 becomes a clutch 3 an electronic coupling system whose components are not in the 1 are shown shown. At the output of the transmission 4 is a drive axle 5 arranged, which with the drive wheels 6 connected is.

The 2 shows an embodiment of the method according to the invention for operating a hybrid vehicle. Here, a slip control and a torque distribution in the phase of Schubeinkuppelns with electrical assistance by the electric motor 2 performed.

A speed and slip control that implements this regulation and distribution 7 consists of a PI controller with pilot control, in which the P component 8th and the I share 9 is calculated separately. The rough speed adjustment is planned with a regulator for the P component 8th and the speed synchronization with a controller for the I component 9 make. The regulation becomes with the engine drag torque 13 and the moment of inertia of the internal combustion engine 1 piloted as this from the clutch 3 must be overcome permanently.

To form the desired clutch torque 15 is next to the engine drag torque 13 another differential speed 19 as well as an I-factor 21 K _iSchub needed to get the I share 9 by means of an integrator 38 to build.

The calculation of the setpoint torque 18 for the electric machine 2 uses to form a gradient 11 a differential speed 19 and an associated characteristic field 39 , In addition, a portion of the moment of inertia goes 41 J _{engine on} . In the determination of the P-share 8th becomes the gradient 11 and a power factor 40 P-factor K _RSchub used.

In the formation of the gradient 16 for the clutch, in addition to the exemplarily given fixed values for a torque and two power specification values, the clutch torque is included 14 respected.

The gradient 17 opening for the clutch is set, for example, by the predetermined fixed value of 300 Nm per second.

Subsequently, these calculated shares 8th and 9 on the electric machine 2 and / or the electronic clutch 3 relocated. This ensures that the control in sum always provides the same torque, but with different torque drivers in the drive train. In the case of a Schubeinkuppelns without electrical assistance is the same speed and slip control 7 only uses all the moments on the electronic clutch 3 be relocated.

For the speed and slip control 7 the input variables become transmission input speed 10 , the gradient of the differential speed 11 , the engine speed 12 , the engine drag torque 13 as well as the clutch torque 14 provided. These are required in the control for calculating the current differential speed. The differential speed corresponds to the difference between the transmission input speed and the engine speed. The speed and slip control 7 provides as output variables a clutch desired torque 15 , a gradient 16 close to the clutch and a gradient 17 to open the clutch and a desired torque 18 ready for the electric machine.

The speed and slip control 7 realized that at least the drag torque of the internal combustion engine 1 is transferred so that the vehicle is delayed for the driver as in the case of an engine braking operation.

This relieves the electric motor, which receives the P-component and the inertia component from a pilot control. Thus, the delay for the driver remains constant. Only the integrated component, which ensures residual slip reduction in the range of small speed differences, is still being transferred to the clutch. This prevents that the torque of the electric motor must be changed again at the end of the control.

The 3 shows a comparison between Schubeinkuppelvorgängen without and with electrical assistance by the electric motor 2 as well as the conflict potential. In a speed (n) time (t) or torque (M) time (t) diagram, the time course of several parameters are shown. Shown are the progressions of the transmission input speed 10 which is related to a vehicle speed, the engine speed 12 , the clutch torque 14 as well as the moment 22 the electric machine 2 , To the speeds n of the parameters 10 and 12 belongs the ordinate on the left with the unit min ^-1 . The ordinate shown on the right represents the scale for the moments M of the parameters 14 and 22 in Nm. In the case of electrical assistance, the characteristic curves of the parameters are shown by means of a continuous characteristic line and in the case without electrical support with dash-and-dash lines.

The representation begins at time zero zero, in which the vehicle is in the operating strategy sailing. At this stage are the electronic clutch 3 and thus the drive train is opened and the internal combustion engine 1 is switched off. Therefore, the values for the engine speed are 12 , the clutch torque 14 and the torque 22 the electric machine 2 at zero. The transmission input speed 10 in the example has a value of approx. 2600 min ^-1 . As the vehicle continues to roll in the Sailing operating strategy, the rotational speed at the output of the gearbox is determined by the speed of the wheels. This speed is in a, dependent on the gear engaged and the gear ratio, transmission input speed 10 implemented.

At a time 23 , which is marked by a vertical line, the process of the Schubeinkupplung, for example, by a driver request that operates the brake pedal starts.

In the case of push-coupling with electric assistance, the electric machine becomes 2 switched on, indicating the course of the rise of the moment 22 the electric machine 2 can be seen. Through the use of the electric motor 2 becomes a steep increase in engine speed 12 achieved, represented with the continuous line of engine speed 12 , Another moment to accelerate the engine is through the clutch 3 generated. The clutch torque 14 rises and is kept at the level achieved. After adjusting the engine speed 12 to the transmission input speed 10 will the clutch 3 closed and the clutch torque 14 rises steeply. In this case, the clutch 3 and thus the drive train 1.9 seconds after the start at the start time 23 closed. From this point on, the kinetic energy of the vehicle can be used for recuperation. With the start of regenerative operation of the electric motor 2 the illustrated moment passes 22 the electric machine 2 in a negative range because energy is generated and not consumed.

The alternative process without electrical support by the electric motor 2 is represented by the dashed lines for the same parameters. It can be seen that the recuperation process in this case only 4.1 seconds after the start time 23 2.2 seconds later.

The 3 shows in the block 24 the described time comparison between the two Schubeinkupplungsvorgängen and in the block 25 the resulting difference in transmission input speed 10 to the respective starting points of the recuperation. It can be seen that the speed loss with electrical assistance with a value of -110 min ^{-1 is} significantly lower in magnitude. Without electrical assistance, the speed loss is -390 min ^-1 .

The possibility of earlier recuperation is only by the block 26 To achieve marked energy use and only an advantage if the recuperation more energy is gained than in the block 26 for the electric machine 2 must be used. In order to always make this mission efficient, the present method, in an upstream step, provides an energy balance of effort and benefits, and can thus make a decision as to whether a thrust clutch is more effective with or without electrical assistance.

The electrical support pays off energetically in comparison to the conventional thrust coupling whenever the measure allows additional energy to be recovered in addition to the energy required for the process. In the energetic consideration of the process, two different calculation steps must be performed.

First, it must be at least estimated whether the supported variant with electric motor 2 opposite the push-in coupling without electric machine 2 have no energy disadvantages or these are offset by the gain in momentum.

Secondly, it must be checked whether recuperation following the thrust coupling process can at least regain the energy needed for startup assistance.

The first calculation step is to show that support by the electric motor 2 is energetically justifiable. For this, it must be known how much energy has to be spent on this. In the 4 is the required energy E in Wh above the transmission input speed 10 shown in min ^-1 . The illustrated graph has been determined by interpolation from the measurement data represented by means of small crosses. The average recuperation rate following these overrunning applications was determined to be P _BRM = 5.4 kW.

With the time savings of 1.9 s from the in the 3 shown example with electrical support results in the example selected transmission input speed of 2500 m ^-1 an energy of E = 5400 · 2.85 / 3600 = 1.5 Wh.

This energy can also be recuperated by faster closing of the powertrain. Considering for feeds and Withdrawing the energy the battery efficiency η _battery = 0.9, then with 2.13 Wh still more energy is recovered, as for the support according to 4 with 2.1 Wh is needed.

Not only the time loss due to shear engagement without electrical assistance can be considered in this calculation, but also the loss of kinetic energy in the form of speed _losses n _loss . To quantify this loss, look at the energy of the port recuperation.

This is in the 5 the recuperated energy E in Wh above the transmission input speed 10 n _Veh started in the recuperation was started. The graphs for second gear 35 , third gear 36 and fourth gear 37 were determined by interpolation from the scattered measured values shown by small crosses in the diagram. In the measurements, with a brake pedal actuation of approximately BrkPed_ratio = 20% up to a transmission input speed 10 of n _Veh = 1100 min ^-1 recuperated.

In the diagram of 5 can be read, how much energy can not be recuperated by an additional loss n _{excess loss} = -245 min ^-1 . Also, this energy can be the electrical support with the electric motor 2 to be counted on. The gradient in the third gear, in which the comparison measurements were carried out in each case, is almost constant and is -1.4 Wh / 100 min ^-1 .

Thus, through push-in engagement with electrical assistance, 3.42 Wh of energy can be recuperated. Taking into account the efficiency results in 2.78 Wh more energy. In sum, this results in a real advantage of 5.09 Wh in the example process, but the electrical support by the electric motor costs only 2.1 Wh. The decision for a Schubeinkuppeln with an electrical support against the without is energetically useful in this case , The method subsequently controls the electric machine 2 as well as the electronic clutch 3 accordingly.

In a second calculation step, it should be determined, based on which at least the electrical energy for starting and closing the drive train could be recovered. For that are used in the 4 represented energy and in the 5 shown recuperated energy needed.

When thrust coupling with electrical support of the electric motor 2 is also lost kinetic energy of the vehicle. In addition, therefore, a speed _loss n _loss is still required for the calculation. This speed loss in min ^-1 is in the 6 for the gears two 35 , three 36 and four 37 above the transmission input speed 10 shown. The scattering of the measured data, which are entered by means of crosses in the diagram, can not be eliminated due to the influence of the friction brake and operating errors by the driver. The illustrated lines 35 . 36 and 37 arise by interpolation from the associated scattering measurement data. With the knowledge of these measurements, a recuperation potential for the thrust engagement with electrical assistance can be calculated.

First, the transmission input speed n _{Veh is} detected upon request of the override clutch operation by the driver, resulting in the required energy until the powertrain is closed. The lost kinetic energy is expressed as the speed _loss n _loss and subtracted from the transmission input speed. From this speed, the Rekuperationspotenzial is known and it can thus be contrasted, whether the electrical support by the electric motor 2 worth it from an energetic point of view.

The potential after previous calculation is in 7 applied at different gears depending on the starting transmission input speed. The illustration shows an energy value E in Wh as a function of the transmission _input speed n _Veh . Shown are the graphs 35 for second gear, 36 for the third and 37 for the fourth gear.

In this illustration you can see that the function worthwhile in fourth gear at each transmission input speed. In third gear = 1400 is achieved a positive overall energy balance min ^-1 until a start transmission input speed of n _Veh, in second gear will cost the support of the shoe leg coupling process by the electric motor 2 to n _Veh = 1700 min ^-1 more energy than can be recovered.

Based on the findings of the energy consideration in the process a decision must be made based on the current vehicle condition, whether the Schubeinkuppelvorgang electrically supported or not, as this is not always energetically useful. In the process flow, before the selection of a Schubeinkuppelvorgangs now a query for 8th performed.

Basically, a support only makes sense if the friction brake of the hybrid vehicle is not too strong, since in this case less energy can be recuperated. Depending on the transmission input speed 10 and the gear engaged 28 can with weakly actuated brake according to the findings in 8th be decided whether a support is worthwhile or not. The characteristic curve of the algorithm was after 7 applied with an additional reserve.

For decision making in the block 27 are input variables as the transmission input speed 10 , an information about the currently engaged gear 28 and information about the brake pedal position 20 needed.

A first test 29 then supplies a positive output signal when the position of the brake pedal 20 At the time the process starts, it is in a range less than or equal to 20 percent of the total pedal travel. For example, a default value of 20 percent is in the block 34 provided. This value varies mainly depending on whether a so-called "Leerweg" is provided for recuperation in the brake pedal in which the friction brake is not actuated and how much the friction brake responds in the case of actuation. This varies in vehicles depending on the model and manufacturer.

Based on the information about the engaged gear 28 a selection of a characteristic from the stored characteristic field takes place 32 which is in the 7 was shown. A second exam 30 then provides a positive output when the transmission input speed 10 located in the range of the selected characteristic.

In the link 31 become the output signals of the first test 29 and the second exam 30 linked together. In the event that both exams 29 and 30 each had generated a positive output signal, the output of the link 31 also be positive. If this is the case, as a result 33 the decision 27 a signal to use the electrical assistance of the Schubeinkuppelvorgangs by the electric motor 2 generated. Is the output of the link 31 negative, as will result 33 the decision 27 generates and outputs a signal for performing the push-in engagement without electrical assistance.

The advantage of the described embodiment of the method according to the invention lies in the optimal utilization of the Rekuperationsenergie at a braking during a sailing phase in a vehicle with electronic clutch system and an electric motor 2 with direct coupling to the combustion engine 1 , The optimal utilization takes comfort aspects into consideration and thus recovers as much energy as possible without impairing comfort or even improving comfort and dynamics.

Claims (10)

A method for operating a hybrid vehicle, in which a current operating strategy leaving the hybrid vehicle controlled by an operation of a brake pedal and closing a drive train of the hybrid vehicle takes place and wherein after closing the drive train kinetic energy of the hybrid vehicle is used for recuperation, characterized in the event that it is determined as a result of a test that by reducing the time taken to close the powertrain (or by reducing the loss of kinetic energy) by using electrical assistance, an energy value to be achieved by the recuperation can be improved , the use of electrical support is done. A method according to claim 1, characterized in that the closing of the drive train of the hybrid vehicle by means of an electronic clutch ( 3 ) he follows. A method according to claim 1 or 2, characterized in that the electrical support by means of an electric motor ( 2 ) of the hybrid vehicle. Method according to one of claims 1 to 3, characterized in that the reduction of the time required for closing the drive train is achieved in that the engine speed ( 12 ) of an internal combustion engine ( 1 ) of the hybrid vehicle by the use of the internal combustion engine ( 1 ) directly coupled electric machine ( 2 ) is increased. Method according to one of claims 1 to 4, characterized in that when testing whether the energy value to be achieved by the recuperation can be improved, a comparison of an energy value required for the electrical support with an energy value to be expected by the earlier commencing recuperation takes place, and that, in the event that the expected energy value is greater, the use of the electrical support takes place. Method according to one of claims 1 to 5, characterized in that the use of the electrical assistance only takes place when a deflection of the brake pedal is in a range equal to or less than a threshold during the test. Method according to one of claims 1 to 6, characterized in that information about the expected energy value and information be provided to the energy value required in the electrical support in the form of digital characteristic data. A computer program adapted to perform each step of the method of any one of claims 1 to 7. A machine-readable storage medium on which a computer program according to claim 8 is stored. Electronic control unit which is set up to operate a hybrid vehicle by means of a method according to one of Claims 1 to 7.

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