DE102016115330A1 - Hydraulic hybrid drive for a motor vehicle and method for operating such a hybrid drive - Google Patents

Abstract

The invention relates to a hydraulic hybrid drive for a motor vehicle having an internal combustion engine and a hydraulic drive motor, as well as to an energy store in which an operating fluid of the hydraulic drive motor can be stored under an operating pressure. It is envisaged that a heat transfer unit is provided on the energy storage, with which the energy storage can be heated in a first operating state of the hydraulic drive motor to increase the gas pressure of a stored in the energy storage working gas and thus to increase the energy density in the energy storage, and in one second operating state of the hydraulic drive motor can be cooled in order to accelerate cooling of the working gas before re-flow of the hydraulic working medium into the energy storage.

Description

The invention relates to a hybrid drive for a motor vehicle and a method for operating such a hybrid drive.

Under a hybrid drive is generally understood a drive concept in which at least two different drive techniques are used. A motor vehicle with hybrid drive is a motor vehicle in which at least two different drive motors or energy converters are provided. For this purpose, usually two separate, independent energy storage are provided, each supplying one of the drive motors or energy converters. The individual drive motors or energy converters can either be used in parallel, then the different energy converters act simultaneously to drive the motor vehicle or serially, then only one of the drive motors or energy converter to drive, while the other energy converter or drive motor only provides power, which then converted directly to drive acting drive motor or energy converter is supplied.

Legislators are calling for a reduction in fuel consumption and thus the carbon dioxide (CO2) emissions of motor vehicles. In this case, hybrid drives are mainly used in passenger cars, which combine an internal combustion engine and an electric motor. As energy storage, a fuel tank for the internal combustion engine and a battery for the electric motor are provided for this purpose.

Alternatively, known from the prior art passenger cars, trucks, buses and construction machinery, in which a combination of a hydraulic drive and an internal combustion engine are used.

From the US 2009/0205892 A1 For example, a motor vehicle with a hybrid drive is known which combines an internal combustion engine with a hydraulic machine. In this case, the hydraulic machine can be used both as a drive motor and as a pump to recover energy from the kinetic energy of the motor vehicle and to buffer them in an energy store. In this case, two chambers are formed on the energy storage, which are separated by a piston. In this case, the one chamber is provided for the storage of nitrogen, while the other chamber is provided for receiving the hydraulic fluid. In this case, the nitrogen is compressed in the energy storage when hydraulic fluid flows into the other chamber of the energy storage and thus shifts the piston in the energy storage. In this case, a heat exchanger is provided on the energy storage, via which the energy storage can be heated by means of the exhaust gas of the internal combustion engine in order to increase the gas pressure in the energy storage and thus the energy density on.

The invention is based on the object to enable the most efficient heat and cold coupling in the energy storage of the hydraulic machine, without causing damage to the fluids used in the energy storage.

The object is achieved by a hybrid drive for a motor vehicle, comprising a primary drive and a secondary drive, which includes a hydraulic machine and an energy storage in which a first fluid and a second fluid can be stored, solved, the energy storage means of a heat transfer unit at least can be heated in sections, wherein the heat transfer unit is adapted to heat the energy storage in a first operating state of the hydraulic machine and to cool in a second operating state of the hydraulic machine. By heating the energy store, the pressure in the energy store can be increased beyond a pressure applied by the hydraulic machine, since the first, gaseous fluid expands further as a result of the heating and thus increases the pressure in the hydraulic store. In a low-pressure phase, it is favorable to cool the energy store in order to facilitate an inflow of the second, liquid fluid and to further reduce the gas pressure of the first fluid.

By the features listed in the dependent claims, advantageous developments and improvements of the method according to the invention specified in the independent claim are possible.

In a preferred embodiment of the invention, it is provided that the primary drive is an internal combustion engine. Although, in principle, other drive motors, such as electric motors generate waste heat, so the combination of a hydraulic machine with an internal combustion engine is advantageous because the hydraulic machine provides a high drive torque especially in the operating areas in which the engine has its weaknesses by design. In addition, a recuperation of energy in a braking operation of a motor vehicle is possible by the hydraulic machine, so that the energy efficiency of a drive train according to the invention can be increased if the prime mover is an internal combustion engine and the secondary drive is a hydraulic drive motor.

According to a preferred embodiment of the invention, an insulation panel is provided in the energy store, which separates a first storage section of the energy store from a second storage section of the energy store. As a result, the different subareas of the energy store are thermally substantially decoupled from one another, so that one subarea can be specifically heated and another subarea can be specifically cooled. In this case, the heating of one subarea and the cooling of the other subarea of the energy store can take place simultaneously. Alternatively, depending on an operating state of the hydraulic machine, either one partial area can be heated or another partial area can be cooled. By means of an insulation panel in the energy store, the region of the energy store in which the first gaseous fluid, in particular nitrogen, is located, can be heated in a targeted manner in order to support an expansion of the first fluid. Due to the insulation panel, not all areas of the energy storage need to be heated, which in total requires less energy for heating the high-pressure accumulator.

In an advantageous further development of the invention, it is provided that a first opening and a second opening are provided in the insulation panel, wherein a conveying means for one of the fluids in the energy store is provided in the first opening. The conveying means may in particular be designed as a gas circulating device for a gaseous fluid, which conveys an operating gas, preferably nitrogen, from the first subregion of the energy store into the second subregion of the energy store. This is preferably done when the energy storage is substantially discharged and has a low pressure level. As a result, a circulation of the first fluid in the energy store can take place, with a separating means, in particular a piston or a membrane for separating the first fluid and the second fluid in the energy store, being located at a distance from the insulation panel. By the circulation device, the cooling of the first fluid can be improved in the energy storage.

It is particularly preferred that the second opening can be opened and closed by a switchable shut-off or is closed by a check valve, which allows a flow of fluid from the second storage section into the first storage section and prevents in the opposite direction. This allows a targeted circulation of the operating gas can be achieved in the energy storage, whereby the cooling of the first fluid is further improved.

In a preferred embodiment of the invention it is provided that the heat transfer unit comprises a heat exchanger, which is connected to an exhaust passage of the internal combustion engine, wherein the heat exchanger can be flowed through by an exhaust gas of the internal combustion engine to heat the energy storage. By a heat exchanger, the waste heat of the engine can be used to heat the energy storage of the hydraulic machine. As a result, the efficiency of the hybrid system is increased, since the waste heat of the internal combustion engine does not leave the exhaust tract unused, but outputs energy to the first fluid in the energy store via the heat exchanger, which can be stored in the form of an increased pressure of the first fluid.

In a further, preferred embodiment of the invention it is provided that the heat transfer unit comprises a heat exchanger which is connected to a cooling air duct or a coolant line of a motor vehicle, wherein the heat exchanger is flowed through by the air or the coolant in order to cool the energy storage. By connecting a heat exchanger to a cooling air duct or a coolant line, the efficiency of the cooling can be further improved, thereby further improving the overall efficiency of the hydraulic hybrid drive.

According to an advantageous further development of the invention, it is provided that the same heat exchanger is used for cooling the energy store and for heating the energy store, wherein between the exhaust passage and the cooling air passage, a control is provided with which can be switched between an exhaust gas flow and a cooling air flow through the heat exchanger , This allows a compact and cost-effective design of the hybrid drive can be achieved, since only one heat exchanger is necessary, which can be used as needed either for cooling or for heating the energy storage.

According to an alternative embodiment of the invention, it is provided that the heat transfer unit has two separate heat exchangers, which are arranged on the energy store, wherein a first heat exchanger for heating and a second heat exchanger for cooling the energy storage are arranged at different areas of the energy store. Alternatively, it is possible that two separate heat exchangers are provided, one of which can preferably be traversed by an exhaust gas of the internal combustion engine and the other of a coolant, in particular of air, flows through. In this case, the two heat exchangers can preferably be thermally coupled or disconnected independently of one another to the energy store, in order to allow the best possible heating and / or cooling of the energy store.

The invention further relates to a method for operating a motor vehicle with a hybrid drive with a primary drive and a secondary drive, which comprises a hydraulic machine and an energy storage in which a first fluid and a second fluid are stored, wherein the energy storage means of a heat transfer unit in a first operating state of the hydraulic machine is at least partially heated and cooled in a second operating state at least partially, wherein the energy storage in the first operating state has a higher pressure level than in the second operating state of the hydraulic machine. It is provided that the heating of the energy storage is then switched on or coupled when the first fluid has reached its final pressure in the energy storage by the mechanical compression by the pumped by the hydraulic machine in the energy storage medium second. In this case, the region of the energy store can be cooled during the inflow of the second fluid, so that the best possible filling of the energy store is achieved.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 a drive train of a motor vehicle with a hydraulic hybrid drive;

2 a first embodiment of an arrangement for heating and cooling the energy storage according to the invention (top right: operation at high pressure, bottom right: operation at low pressure); and

3 an alternative embodiment of an arrangement for heating and cooling according to the invention of the energy storage of the hydraulic machine (above: heating operation, below: cooling operation).

1 shows a drive train of a motor vehicle with a hydraulic hybrid drive 10 , which as a primary drive 12 an internal combustion engine 30 and as a secondary drive 14 a hydraulic machine 16 having. The hydraulic machine 16 becomes from an energy storage 18 supplied with a hydraulic operating fluid, wherein at the energy storage 18 a heat transfer unit 20 for heating and cooling the energy storage 18 is provided. The internal combustion engine 30 has an exhaust duct 44 on, with which the exhaust gas of the internal combustion engine 30 is emitted into the environment.

In 2 is a first embodiment of an energy storage 18 a hydraulic hybrid drive according to the invention 10 shown. The energy storage 18 is in a first storage section 28 for storing a first fluid 22 , preferably a gaseous fluid, in particular nitrogen, and in a second storage section 32 for storing a second, different from the first fluid 24 , preferably a liquid fluid, in particular a hydraulic oil, divided. Between the first storage section 28 and the second storage section 32 is an insulation panel 26 provided a heat exchange between the two storage sections 28 and 32 to reduce. In the insulation panel 26 are a first opening 34 and a second opening 36 intended. In the first opening 34 is a grant 38 , in particular a circulation pump provided. The second opening 36 is by a switchable shut-off 40 closable. At the energy storage 18 is a heat transfer unit 20 arranged, which a first heat exchanger 42 for heating the first memory section 28 of the energy store 18 and a second heat exchanger 46 for cooling the second storage section 32 of the energy store 18 having. The first heat exchanger 42 points to his the energy storage 18 side facing a connection with the exhaust duct 44 of the internal combustion engine 30 on. The second heat exchanger 46 points to his the energy storage 18 side facing away from a connection with a coolant circuit, not shown.

The energy storage 18 can through the hydraulic machine 16 in a braking operation of the motor vehicle or by a mechanical drive of the hydraulic machine 16 through the internal combustion engine 30 be filled. For this purpose, a hydraulic working fluid in the second storage section 32 of the energy store 18 promoted. The hydraulic working fluid compresses the first fluid 22 in the first storage section 28 of the energy store 18 up to a maximum delivery pressure of the hydraulic machine 16 , By a flow through the first heat exchanger 42 through the hot exhaust gas of the internal combustion engine 30 becomes the first fluid 22 heated, causing the pressure in the first storage section 28 of the energy store 18 continues to rise (see 2 top right). This pressure can in an operating phase in which the motor vehicle by the hydraulic machine 16 is used to the hydraulic working fluid from the second storage section 32 through the hydraulic machine 16 to promote. In extension of a flow path of the hydraulic working medium from the energy storage 18 through the hydraulic machine 16 is a surge tank 56 provided for receiving the hydraulic working fluid.

In a second phase of operation of the hydraulic machine 16 is the energy storage 18 essentially emptied, with the first heat exchanger 42 is deactivated and the second memory section 32 of the energy store 18 through the second heat exchanger 46 is cooled (see 2 bottom right). For the best possible cooling of the first fluid 22 to achieve, is the switchable shut-off 40 , In particular a switchable flap or a switchable valve, open and the conveyor 38 activated to a circulation of the first fluid 22 in the energy storage and thus a uniform cooling of the first fluid 22 to reach.

In 3 is another embodiment of an energy storage 18 for a hybrid drive according to the invention 10 shown. At the energy storage 18 is in a first storage section 28 for storing the first fluid 22 , and a second memory section 32 for storing the second, different from the first fluid 24 divided. Between the first storage section 28 and the second storage section 32 is an insulation panel 26 provided a heat exchange between the two storage sections 28 and 32 to reduce. In the insulation panel 26 are a first opening 34 and a second opening 36 intended. In the first opening 34 is a grant 38 , in particular a circulation pump provided. The second opening 36 is by a switchable shut-off 40 closable. At the energy storage 18 is a heat transfer unit 20 arranged, which a first heat exchanger 42 for heating and cooling the first storage section 28 of the energy store 18 having. The first heat exchanger 42 can by switching controls 52 optionally for cooling the first storage section 28 with cooling medium, in particular air, from a cooling air duct 48 or for heating the first storage section 28 with exhaust gas from the exhaust duct 44 be flowed through. This is in the exhaust duct 44 an exhaust flap 54 provided with which the exhaust passage 44 can be blocked to a larger volume flow of exhaust gas through the heat exchanger 42 respectively.

In a heating phase of the energy storage 18 is the exhaust flap 54 closed and it will exhaust from the exhaust duct 44 through the heat exchanger 42 guided ( 3 above). Where are the controls 52 switched so that they in the heating phase, the cooling air duct 48 obstruct and a flow through the heat exchanger 42 allow through the exhaust.

In a cooling phase is the exhaust flap 54 opened and the controls 52 are placed so that they flow through the heat exchanger with exhaust gas from the exhaust duct 54 lock and a flow through the heat exchanger with cooling air from the cooling air duct 48 enable ( 3 below).

LIST OF REFERENCE NUMBERS

10

hybrid drive

12

primary drive

14

secondary drive

16

hydraulic machine

18

energy storage

20

Heat transfer unit

22

first fluid

24

second fluid

26

insulation panel

28

first storage section

30

internal combustion engine

32

second memory section

34

first opening

36

second opening

38

funding

40

shutoff

42

heat exchangers

44

exhaust duct

46

heat exchangers

48

Cooling air duct

50

Coolant line

52

control

54

exhaust flap

56

surge tank

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2009/0205892 A1 [0005]

Claims (10)

Hybrid drive ( 10 ) for a motor vehicle, comprising a primary drive ( 12 ) and a secondary drive ( 14 ), which is a hydraulic machine ( 16 ) and an energy store ( 18 ), in which a first fluid ( 22 ) and a second fluid ( 24 ) can be stored, the energy storage ( 18 ) by means of a heat transfer unit ( 20 ) is heated at least in sections, characterized in that the heat transfer unit ( 20 ) is adapted to the energy storage ( 18 ) in a first operating state of the hydraulic machine ( 16 ) and to cool in a second operating state of the hydraulic machine. Hybrid drive ( 10 ) according to claim 1, characterized in that the primary drive ( 12 ) an internal combustion engine ( 30 ). Hybrid drive ( 10 ) according to claim 1 or 2, characterized in that in the energy store ( 18 ) an insulation panel ( 26 ) is provided, which a first memory section ( 28 ) of the energy store ( 18 ) from a second memory section ( 32 ) of the energy store ( 18 ) separates. Hybrid drive ( 10 ) according to claim 3, characterized in that in the insulation panel a first opening ( 34 ) and a second opening ( 36 ) are provided, wherein in the first opening ( 34 ) a grant ( 38 ) for one of the fluids ( 22 . 24 ) is provided. Hybrid drive ( 10 ) according to claim 4, characterized in that the second opening ( 36 ) by a switchable shut-off means ( 40 ) can be opened and closed. Hybrid drive ( 10 ) according to one of claims 2 to 5, characterized in that the heat transfer unit ( 20 ) a heat exchanger ( 42 ), which with an exhaust duct ( 44 ) of the internal combustion engine ( 30 ) connected is. Hybrid drive ( 10 ) according to one of claims 1 to 6, characterized in that the heat transfer unit ( 20 ) a heat exchanger ( 46 ), which is connected to a cooling air channel ( 48 ) or a coolant line ( 50 ) connected is Hybrid drive ( 10 ) according to claim 6 and 7, characterized in that for cooling the energy store ( 18 ) and for heating the energy store ( 18 ) the same heat exchanger ( 42 . 46 ) is used, wherein between the exhaust duct ( 44 ) and the cooling air channel ( 48 ) a control ( 52 ) is provided, with which between an exhaust gas flow and a cooling air flow through the heat exchanger ( 42 . 46 ) can be switched. Hybrid drive ( 10 ) according to claims 6 and 7, characterized in that two separate heat exchangers ( 42 . 46 ) on the energy store ( 18 ) are provided, wherein a first heat exchanger ( 42 ) for heating and a second heat exchanger ( 46 ) for cooling the energy store ( 18 ) are provided, which at different areas of the energy storage ( 18 ) are arranged. Method for operating a motor vehicle with a hybrid drive ( 10 ) with a primary drive ( 12 ) and a secondary drive ( 14 ), which is a hydraulic machine ( 16 ) and an energy store ( 18 ), in which a first fluid ( 22 ) and a second fluid ( 24 ), whereby the energy store ( 18 ) by means of a heat transfer unit ( 20 ) in a first operating state of the hydraulic machine ( 16 ) is heated at least partially and in a second operating state of the hydraulic machine ( 16 ) is cooled at least partially, wherein the energy storage ( 18 ) in the first operating state, a higher pressure level than in the second operating state of the hydraulic machine ( 16 ) having.

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