DE102022207631A1 - Oil supply system and hybrid powertrain - Google Patents

Abstract

The invention relates to an oil supply system (10) for supplying oil to a hybrid drive train (1), wherein the hybrid drive train (1) comprises an internal combustion engine (2), an electric machine (4) and a switching element (6). A drive connection between the internal combustion engine (2) and the electric machine (4) can be separated into a first drive section (3) and a second drive section (5) by means of the switching element (6). The switching element (6) can be actuated hydraulically using the oil supply system (10). The oil supply system (10) comprises a first pump (11) driven by the first drive section (3) and a second pump (12) driven by the second drive section (5). Furthermore, a hybrid drive train (1) with such an oil supply system (10 ) specified.

Description

The present invention relates to an oil supply system for supplying oil to a hybrid drive train, wherein the hybrid drive train comprises an internal combustion engine, an electric machine and a switching element for separating the drive connection between the internal combustion engine and the electric machine. The invention further relates to a hybrid drive train with such an oil supply system.

From the DE 10 2011 112 753 A1 a hybrid drive train with an internal combustion engine and an electric machine is known, which can also be operated at least temporarily as a serial hybrid drive. The hybrid drive train includes an internal combustion engine, an electric machine and a planetary gear arranged in the drive connection between the internal combustion engine and the electric machine. With the help of a braking system, the ring gear of the planetary gear can be braked so that it can be temporarily made into a stationary component of the planetary gear. The braking system can be actuated, for example, by means of hydraulic pressure.

It is the object of the present invention to provide an improved oil supply system for supplying oil to a hybrid drive train and a hybrid drive train with such an oil supply system.

This object is achieved by an oil supply system according to claim 1 and by a hybrid drive train according to claim 7. Advantageous embodiments are specified in the dependent claims.

An oil supply system for supplying oil to a hybrid powertrain is proposed. The hybrid drive train includes an internal combustion engine, an electric machine and a switching element, which is arranged in a drive connection between the internal combustion engine and the electric machine. During normal driving, the drive power of the internal combustion engine is transmitted to the electric machine via the drive connection in order to generate electrical energy in generator operation, which is used to electrically drive the vehicle with one or more electric drive motors. Such a drive arrangement is also called a serial hybrid drive. To start the internal combustion engine, said electric machine can be operated as an electric motor. In addition to the switching element, the drive connection can also include a transmission, in particular a transmission, which brings about a transmission ratio between the speeds of the internal combustion engine and the electric machine. The switching element can be structurally integrated into such a transmission or attached to it.

The switching element enables the drive connection to be disconnected and connected. With the switching element, the drive connection can therefore be separated into a first drive section connected to the internal combustion engine and into a second drive section connected to the electric machine. The switching element can therefore be either closed or open. The switching element can be actuated hydraulically using the oil supply system. The switching element can in particular be designed as a hydraulically actuated brake or clutch.

The oil supply system includes a first pump driven by the first drive section and a second pump driven by the second drive section. The first and second pumps are therefore driven mechanically, preferably via gear connections. Compared to electrically driven pumps, mechanically driven pumps have the advantage that they function reliably even at very low temperatures. Each of the two pumps has such a pump performance that it alone can provide sufficient oil pressure and volume flow to actuate the switching element. This ensures that the switching element can be actuated in any operating state, regardless of whether only the internal combustion engine is operated with the first drive section, only the electric machine with the second drive section or both.

The proposed oil supply system can have a high-pressure area to which a pressure port of the first and second pumps is connected or can be connected. A first pressure connection of the first pump and a second pressure connection of the second pump are therefore connected or can be connected to the high-pressure area. Preferably, it is now provided that the second pressure connection can be separated from the high-pressure area by means of a pump switching valve. The pump switching valve can be arranged in the high pressure area.

The pump changeover valve ensures that the appropriate amount of oil is delivered to a main pressure valve in all operating states. During normal operation, the first and second drive sections, and thus also the first and second pumps, are driven. This means that the pump outputs of the two pumps are added together. Since the required functionality, in particular for actuating the switching element, is already provided with one of the following can be ensured by the pumps, there is excess hydraulic power in normal operation. With the help of the pump switching valve, oil delivery from the second pump into the high-pressure area of the oil supply system can now be stopped. Instead, the volume flow of the second pump can be returned directly, ie with almost no pressure and flow losses, to an oil reservoir, for example an oil sump. This allows the overall efficiency of the hybrid powertrain to be increased. The energy savings due to the separation of the second pump from the high-pressure area can be considerable because the second pump is not required during normal operation, which is predominantly the case over time, and can run with almost zero power in these predominant operating phases.

The pressure can be limited to a predetermined high pressure value in the high pressure area by a first pressure relief valve. A high pressure value suitable for the respective application can be set. In the present case, the high pressure value should be at least so high that it is sufficient to reliably actuate the switching element hydraulically. For example, the first pressure relief valve can be set so that the high pressure value is limited to approximately 20 bar.

The pump switching valve can in particular be controlled using a solenoid valve and actuated depending on a first pressure generated by the first pump.

To regulate the pressure for actuating the switching element, a clutch control valve can be connected in the high pressure area between the pump changeover valve and the first pressure relief valve. With the help of the clutch control valve, the switching element can be specifically controlled and the switching element can be either closed or opened. In particular, if the switching element is designed as a frictional clutch or brake, the behavior of the switching element can also be controlled in a targeted manner using the clutch control valve, for example in order to achieve a certain speed when closing the switching element.

In the high-pressure area between the second pump and the pump switching valve, a second pressure relief valve can be connected, which limits a maximum pressure in this area, the set maximum pressure value being higher than the above-mentioned high pressure value. By using the second pressure relief valve, the second pump can be operated for a limited time with excess hydraulic power or with a very high volume flow in order to avoid an undesirable pressure drop in the high-pressure value system in certain operating states. If the high pressure value is exceeded in the area between the second pump and the pump switching valve, the excess oil can then be drained back into the tank or the oil reservoir via the second pressure relief valve.

Such an operating state can arise, for example, during a so-called generator start. First, the electric machine is ramped up to a target speed for starting the internal combustion engine. The second pump connected to the electric machine generates sufficiently high oil pressure to close the switching element when the clutch control valve is opened. So when the target speed is reached, the clutch control valve is switched so that the switching element is closed. The drive connection between the electric machine and the internal combustion engine is thus closed and the electric machine and the masses already driven by it accelerate the crankshaft of the internal combustion engine and cause it to start. After the switching element is closed, the first pump also begins to deliver oil. As a result, the pump switching valve can be switched to avoid operation with a high hydraulic power surplus. The pump switching valve is switched from a first position, in which the pressure connections of the first and second pumps are connected to one another via the pump switching valve, to a second position, in which the pressure connection of the second pump is connected to the tank or oil reservoir. In the second position of the pump switching valve, only the first pump delivers to the high-pressure area, and the oil flow generated by the second pump flows back into the tank. The pump switching valve can be switched, for example, depending on the speed of the internal combustion engine. For example, switching can occur as soon as the speed of the internal combustion engine exceeds 1000 revolutions per minute.

In order to ensure that the pressure in the high-pressure area does not collapse during the switching process described, an overlap on the pump switching valve can be selected so that the second pump delivers a significantly higher pump output and volume flow for a short time than would be required to maintain the high-pressure value. Due to a very high volume flow, the excessive pump output could not be sufficiently reduced via the first pressure relief valve in a short period of time. In this short time, excess pressure or the excess oil volume can be reduced via the second pressure relief valve. For example The second pressure relief valve can be set so that the pressure between the second pump and the pump switching valve is limited to a maximum pressure value of approximately 30 bar even in this short time.

In addition to the hydraulic actuation of the switching element, the oil supply system can also supply oil to lubrication points in the hybrid drive train. For this purpose, a low-pressure area can be connected downstream of the first pressure relief valve. The pressure in the low-pressure area can be limited to a specific low pressure by a third pressure relief valve, for example to a low pressure value of 2 bar. Such a low pressure value is sufficient to ensure the required lubrication of lubrication points 31 from the low pressure value.

Furthermore, the oil supply system can also provide pressure oil for actuating other switching elements. For example, switchable power take-offs, also known as PTOs, can be hydraulically operated or switched on or off using the oil supply system. For this purpose, suitable switching valves can be connected to the high-pressure area.

The invention and its advantages are explained in more detail below using the exemplary embodiment in the attached figure.

• 1 eine schematische Darstellung eines Hybridantriebsstrang und
• 2 ein schematisches Schaltbild eines Ölversorgungssystems für einen Hybridantriebsstrang gemäß 1.

Show it

• 1 a schematic representation of a hybrid powertrain and
• 2 a schematic circuit diagram of an oil supply system for a hybrid powertrain according to 1 .

The Indian 1 The hybrid drive train 1 shown includes an internal combustion engine 2, an electric machine 4 and a switching element 6 arranged in the drive connection therebetween. The drive connection between the internal combustion engine 2 and the electric machine 4 can be converted into a first drive section 3 and connected to the internal combustion engine 2 by means of the switching element 6 be separated into a second drive section 5 connected to the electric machine 4. In the present case, separate means that no torque can be transferred from the first drive section 3 to the second drive section 5 or vice versa. In the present exemplary embodiment, the switching element 6 is connected to a transmission element of a transmission 7 arranged between the first drive section 3 and the second drive section 5. The switching element 6 can be structurally integrated into the transmission 7, resulting in a very compact design. The transmission 7 is designed as a planetary gear, with the ring gear of the planetary gear being connected to the electric machine 4 and the planet carrier of the planetary gear being connected to the internal combustion engine 2. The switching element 6 is connected to the sun gear of the planetary gear. The switching element 6 is designed as a frictional disk brake, with an outer disk carrier being firmly connected to a stationary housing 20 and an inner disk carrier being connected to the sun gear of the planetary gear.

A first pump 11 is driven by the first drive section 3 via a first pair of gears 8. A second pump 12 is driven by the second drive section 5 via a second pair of gears 9. The two pumps 11 and 12 are part of an oil supply system 10, which is in the 2 shown schematically and described in more detail below.

The switching element 6 is using the in the 2 Oil supply system 10 shown can be operated hydraulically. The oil supply system 10 includes a first pump 11 and a second pump 12, the first pump 11 being driven by the first drive section 3 and the second pump 12 being driven by the second drive section 5. The first and second pumps 11 and 12 are driven mechanically via an assigned pair of gears 8 and 9, respectively. There is a driving gear on a shaft of the assigned drive section 3 or 5 and a driven gear on a pump drive shaft of the respective pump 11 or .12 arranged.

That in the 2 Oil supply system 10 shown includes a high pressure area 15, which is connected to the first pressure connection 13 of the first pump 11. Only when the pump switching valve 16 is in the first position shown is the second pressure connection 14 of the second pump 12 connected to the high-pressure area 15. The Indian 2 The high-pressure area 15 drawn as a rectangle by means of a dotted line therefore corresponds approximately to the high-pressure area 15 when the pump switching valve 16 is in the spring-supported first position.

The second pressure connection 14 can be separated from the high-pressure region 15 by means of a pump switching valve 16 by switching the pump switching valve 16 from a first position, in which the pressure connections 13, 14 of the first and second pumps 11, 12 are connected to one another, to a second position . In the second position, the pressure connection 14 of the second pump 12 is connected to the tank 18. The tank can, for example, include an oil sump of the transmission 7. In the second position of the pumpum switching valve 16 only delivers the first pump 11 into the high-pressure area 15. The oil flow generated by the second pump 12 then flows almost without pressure through a first return line 23 from the pump switching valve 16 into the tank 18.

The pump switching valve 16 is pressure-operated and is controlled using a solenoid valve 17. The pressure for actuating the pump switching valve 16 is generated by the first pump 11. In the unactuated state, the pump switching valve 16 is held in its basic position, the first position described above, by a spring.

The pressure in the high-pressure area 15 is limited to a predetermined high-pressure value by a first pressure relief valve 19. The first pressure relief valve 19 essentially separates the high-pressure area 15 from a low-pressure area, which essentially serves to lubricate and cool elements of the hybrid drive train 1 at various lubrication points 31.

A clutch control valve 25 is provided in the high-pressure area 15 for hydraulic pressure actuation of the switching element 6. The clutch control valve 25 is connected between the pump switching valve 16 and the first pressure relief valve 19. In the same area or pressure branch, two additional pressure connections 27 and 28 are provided in the present exemplary embodiment. These pressure connections 27, 28 can be used, for example, to switch power take-offs 29, so-called PTOs.

A second pressure relief valve 26 is arranged between the second pump 12 and the pump switching valve 16. The second pressure relief valve 26 limits the pressure in this area to a maximum pressure value which is higher than the high pressure value limited by the first pressure relief valve 19. The second pressure relief valve 26 can also be referred to as a safety valve. It ensures that in operating states in which the second pump 12 delivers to the high-pressure area 15 through high drive speeds with excess hydraulic power, the maximum pressure is limited and excess volume flow can flow directly into the tank 18.

A check valve 21 or 22 is arranged in the pressure lines of both pumps 11 and 12 in order to ensure that the required pressure or high pressure is built up in the operating states in which a pump 11 or 12 is stationary and the solenoid valve 17 is not switched can.

The pressure in the low-pressure area can be limited to a specific low-pressure value by a third pressure relief valve 30. A suitable low pressure value is, for example, 2 bar in order to supply the lubrication points 31 in the hybrid drive train 1 with sufficient oil. The third pressure relief valve 30 thus determines the lubricating pressure and can therefore also be called a lubricating pressure valve. The third pressure relief valve 30 directs unnecessary volume flow through a second return line 24 directly in front of a suction area of the first pump 11. This further improves the efficiency and reduces the tendency to cavitation in the first pump 11.

In the present case, a heat exchanger 32 is provided in the low-pressure area. A bypass valve 33 protects the heat exchanger 32 from excessively high volume flows and, especially at low temperatures, from excessively high pressures.

Reference symbols

1

Hybrid powertrain

2

Internal combustion engine

3

first drive section

4

electric machine

5

second drive section

6

Switching element

7

transmission

8th

Gear pair

9

Gear pair

10

Oil supply system

11

first pump

12

second pump

13

first pressure connection

14

second pressure connection

15

High pressure area

16

Pump switching valve

17

magnetic valve

18

tank

19

first pressure relief valve

20

Housing

21

check valve

22

check valve

23

first return line

24

second return line

25

Clutch control valve

26

second pressure relief valve

27

Pressure connection

28

Pressure connection

29

PTO

30

third pressure relief valve

31

Lubrication points

32

Heat exchanger

33

Bypass valve

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was 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

• DE 102011112753 A1 [0002]

Claims (7)

Oil supply system (10) for supplying oil to a hybrid drive train (1), the hybrid drive train (1) comprising an internal combustion engine (2), an electric machine (4) and a switching element (6), wherein a drive connection between the internal combustion engine (2) and the electrical Machine (4) can be separated by means of the switching element (6) into a first drive section (3) connected to the internal combustion engine (2) and into a second drive section (5) connected to the electric machine (4), and wherein the switching element (6) can be actuated hydraulically using the oil supply system (10), characterized in that the oil supply system (10) comprises a first pump (11) driven by the first drive section (3) and a second pump (12) driven by the second drive section (5). Oil supply system (10). Claim 1 , characterized in that the oil supply system (10) has a high-pressure area (15), a first pressure connection (13) of the first pump (11) and a second pressure connection (14) of the second pump (12) are connected to the high-pressure area (15). or can be connected, and that the second pressure connection (14) can be separated from the high-pressure area (15) by means of a pump switching valve (16). Oil supply system (10). Claim 1 or 2 , characterized in that the pump switching valve (16) can be controlled using a solenoid valve (17) and can be actuated depending on a pressure generated by the first pump (11). Oil supply system (10). Claim 2 or 3 , characterized in that the pressure in the high-pressure area (15) is limited to a high-pressure value by a first pressure relief valve (19). Oil supply system (10). Claim 4 , characterized in that a clutch control valve (25) is connected between the pump switching valve (16) and the first pressure relief valve (19). Oil supply system (10). Claim 4 or 5 , characterized in that a second pressure relief valve (26) is arranged in the high pressure area (15) between the second pump (12) and the pump switching valve (16), and that the second pressure relief valve (26) limits the pressure in this area to a maximum pressure value , where the maximum pressure value is higher than the high pressure value. Hybrid drive train (1) with an oil supply system (10) according to one of the preceding claims.

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