EP2024196A1

EP2024196A1 - Drive with braking energy recovery

Info

Publication number: EP2024196A1
Application number: EP07725763A
Authority: EP
Inventors: Matthias Müller; Steffen Mutschler
Original assignee: Bosch Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 2006-06-02
Filing date: 2007-06-01
Publication date: 2009-02-18
Also published as: DE102006046965A1; WO2007140944A1

Abstract

The invention relates to a drive for braking energy recovery. The drive comprises a drive motor (2) which is connected to a transmission (3). The transmission has a transmission output shaft (5) and at least one coupling shaft (6). A hydrostatic piston machine (12) is connected to the coupling shaft. The drive also comprises a storage device (13, 14) which can be connected to the hydrostatic piston machine. The hydrostatic piston machine is connected to the coupling shaft.

Description

Drive with brake energy recovery

The invention relates to a drive with a storage device for the recovery of braking energy.

From AT 395 960 B it is known to use a hydrostatic motor in the sliding or braking operation of a driven vehicle to store the released kinetic energy in the form of pressure energy in a memory. In a subsequent acceleration, the pressure accumulator discharges via the hydraulic motor and thus contributes to the drive of the vehicle. In this way, the kinetic energy can be cached and reduces the fuel consumption of a primary engine.

For this purpose, the system proposed in AT 395 960 B uses a hydrostatic drive in which a hydraulic pump is coupled to the hydraulic motor. The hydraulic circuit is connected to a first pressure accumulator and a second pressure accumulator. One of the two accumulators is a high-pressure accumulator. The described system has the disadvantage that the application is limited to those travel drives which use a hydraulic circuit to generate the output torque.

The invention has for its object to enable the storage of kinetic energy by means of a pressure accumulator for mechanically driven vehicles.

The object is achieved by the drive according to the invention with the features of claim 1.

According to the invention, the drive comprises a drive motor and a transmission connected thereto. The transmission has a transmission output shaft and at least one coupling shaft. For storing kinetic energy during a deceleration process, a hydrostatic piston engine is provided, which over the Coupling shaft is coupled to the drive. The coupling shaft may be a PTO shaft or integrated into the transmission. In addition, a memory is provided, which is used to store the released kinetic energy.

By connecting the hydrostatic piston engine to the transmission charging of the memory is possible in the overrun mode, since the hydrostatic piston engine is driven by the inertia of the vehicle via the transmission. The power flow goes from the transmission output shaft, which is usually connected to a rear axle, to the coupling shaft, which is connected to the hydrostatic piston engine. By the hydrostatic piston engine is

Pressure medium promoted under pressure increase in the storage device.

Conversely, during a subsequent acceleration process, the pressure accumulator can be expanded via the hydrostatic piston engine, whereby a torque, which is generated by the hydrostatic piston engine, is introduced into the transmission via the coupling shaft. The introduced torque is thus available for driving via the transmission output shaft. Further, it is possible to bridge, for example, during a switching operation in which the power flow is interrupted by the drive motor to the transmission output shaft. This avoids unwanted traction interruptions during shifting.

In the dependent claims advantageous refinements of the drive according to the invention are carried out.

In particular, it is advantageous to connect the hydrostatic piston engine by means of a first coupling with the coupling shaft. Such detachable connection of the hydrostatic piston engine to the transmission has the advantage that a towing the hydrostatic piston engine in pure driving is not required. This splashing losses are avoided in the hydrostatic piston engine. For example, in a constant travel can be further reduced by uncoupling the fuel consumption of the drive according to the invention.

Furthermore, it is advantageous to couple the drive motor via a clutch with the transmission input shaft, so that the connection between the transmission input and the drive motor can be interrupted. Thus, the connection between the coupling shaft and the drive motor is interrupted, so that in the hydrostatic braking released kinetic energy is completely supplied to the storage device. A recording of kinetic energy by the mostly as

Internal combustion engine running drive motor is avoided.

According to a further preferred embodiment, a transmission input shaft of the transmission forms the coupling shaft. Further, a second clutch for separating the transmission input shaft is arranged. By means of the second clutch, it is also possible without a clutch to disengage the drive motor from the coupling shaft and thus to provide improved condition during storage of the released kinetic energy.

The second clutch is preferably arranged between a first gear pair for the highest gear ratio and a second gear pair of the second highest gear stage. If the hydrostatic piston engine is driven by the inertia of the moving vehicle, this results in a suitable reduction, which makes it possible to operate the hydrostatic piston engine in an economically advantageous speed range. In particular, also for the engagement of the hydrostatic piston engine to the coupling shaft large Speed differences avoided. An increase in the life of the clutch is the result.

Preferably, the transmission is designed as a so-called two-stage transmission, which has a transmission input shaft, a transmission output shaft and an intermediate shaft. The intermediate shaft is connected to both the coupling shaft and the transmission output shaft via a respective gear stage. Thus, the transmission output shaft is mechanically coupled to the coupling shaft via these two gear stages. The drive with the two-stage transmission has the advantage that a decoupling of the drive motor is also possible by an idle position of the transmission, in which there is no connection between the transmission input shaft and the intermediate shaft.

Alternatively, the transmission may have a transmission input shaft, a transmission output shaft and an intermediate shaft, wherein the intermediate shaft forms the coupling shaft. Again, by inserting an idle the transmission input shaft can be disengaged from the intermediate shaft, so that a direct torque transmission from the transmission output shaft to the intermediate shaft and thus the coupling shaft. Preferably, the intermediate shaft, which forms the coupling shaft, with the transmission output shaft via at least a first gear stage and a second gear stage alternately connectable. The possibility of switching between two gear ratios allows a further improved speed adjustment during the braking process with regard to the efficiency of the hydrostatic piston engine.

Preferred embodiments of the drive according to the invention are shown in the drawing and are explained in more detail in the following description. Show it:

Fig. 1 is a schematic representation of a drive according to the invention; Fig. 2 is a simplified representation of a first

Force flow during energy recovery by means of a transmission of a first design;

Fig. 3 is a simplified representation of a power flow of energy recovery by means of a transmission of a second design and

Fig. 4 is a simplified representation of a third

Power flow during energy recovery by means of a transmission of a third design.

Before discussing the power flow with reference to three examples of different transmission variants, the basic principle will first be explained with reference to the schematic representation of FIG. In Fig. 1, an inventive drive 1 is shown. The drive 1 according to the invention generally comprises a drive motor 2. If the drive 1 according to the invention is, for example, the travel drive of a vehicle frequently moved in stop-and-go operation, the drive motor 2 is generally designed as a diesel internal combustion engine. Such vehicles, in which frequently start-up and braking cycles occur alternately, may be, for example, refuse collection vehicles, wheel loaders in construction site operation or delivery vehicles. By the drive motor 2, a transmission 3 is driven, which is connected to a rear axle 4. The transmission 3 is connected via a transmission output shaft 5 with a rear differential 7. The

Hinterachsdifferential 7 is connected via a first half-shaft 8 and a second half-shaft 9 with a first driven wheel 10 and a second driven wheel 11.

To recover the kinetic energy released during a braking operation, a hydrostatic piston machine 12 is provided. The hydrostatic piston engine 12 is both as a hydraulic pump and as Hydromotor can be used. The hydrostatic piston machine 12 is preferably designed to be adjustable in its delivery or displacement volume and provided for delivery in two directions. The hydrostatic piston engine 12 is also connected to the transmission 3 via a coupling shaft, which in the illustrated embodiment is a power take-off shaft 6. During coasting of the vehicle, a force flow between the rear axle 4 and the PTO shaft 6 is thus generated due to the inertia, through which the hydrostatic piston engine 12 is driven.

During the deceleration of a vehicle, pressure medium is conveyed from a first accumulator 13 into a second accumulator 14 by the hydrostatic piston machine 12, which in this case acts as a pump. In this case, the ^" first storage 13 serves as a pressure medium reservoir and is designed as a tank or low-pressure accumulator." On the other hand, the second accumulator 14 is designed as a high-pressure accumulator

Pressure medium increases the pressure and the kinetic energy of the vehicle stored in the form of pressure energy. The first accumulator 13 is connected to a connection of the hydrostatic piston machine 12 via a first accumulator line 15. The second memory 14 is connected via a second storage line 16 to a second connection of the hydrostatic piston machine 12.

Preferably, a check valve 17 is arranged in the second storage line 16. By means of the check valve 17, the flow between the second memory 14 and the hydrostatic piston machine 12 can be interrupted. Thus, a lossless storage of pressure energy in the second memory 14 is made possible, for example, if a withdrawal of stored pressure energy is not required during a longer connection journey.

If the vehicle is then accelerated again when the second memory 14 is filled, then this acts hydrostatic piston machine 12 as a hydraulic motor. The pressurized pressure medium of the second accumulator 14 is expanded via the hydrostatic piston engine 12 and flows into the first accumulator 13. The two accumulators 13, 14 thus form together with the hydrostatic

Piston engine 12 a hydraulic cradle. When the pressure medium is released from the second reservoir 14, a torque is generated by the hydrostatic piston engine 12, which torque is supplied to the transmission 3 via the auxiliary output shaft 6. The torque supplied to the transmission 3 can either be used in addition to the torque of the drive motor 2 to accelerate the vehicle or to bridge the switching pause, while for example the drive motor 2 is separated from the transmission 3 by a clutch.

In order to be able to set the generated torque or the generated braking force during the braking process or the recovery of the stored energy, the hydrostatic piston machine 12 is designed to be adjustable. To adjust the delivery or intake of the hydrostatic piston engine 12, an adjusting device 18 is provided. Adjusting device 18 includes a hydraulic cylinder in which an actuating piston 19 is arranged. The actuating piston 19 divides the hydraulic cylinder into a first actuating pressure chamber 20 and a second actuating pressure chamber 21. A suitable pressure ratio can be set in the actuating pressure chambers 20, 21 by means of a control valve 23. Due to the adjusting adjusting pressure in the first actuating pressure chamber 20 and the second actuating pressure chamber 21, a resultant force in the axial direction is exerted on the actuating piston 19, by means of which the actuating piston 19 is displaced. The adjusting movement of the adjusting piston 19 is transmitted via a linkage 22 to an adjusting mechanism of the hydrostatic piston machine 12. The control valve 23 is connected via a first control pressure line 24 and a second control pressure line 25 to the first control pressure chamber 20 and the second control pressure chamber 21. In a first position, a flow-through connection between a pressure line 26, in which a pressure generated, for example, by a feed pump, and the second control pressure line 25 is generated by the control valve 23. At the same time, the first actuating pressure line 24 is connected to a tank volume 28 via an expansion line 27. In this first position of the control valve 23, which corresponds to the rest position of the control valve 23, the control valve 23 is held by a compression spring 29. In the opposite direction, the control valve 23 can be brought by an actuator, which is formed in the illustrated embodiment by a proportional solenoid 30.

For controlling the proportional magnet 30, a control unit 31 is provided. The control unit 31 preferably also interacts with an injection pump 32 of the drive motor 2. The control of the control valve 23 and the injection pump 32 is performed by the control unit 31 in response to, for example, signals of an accelerator pedal and a brake pedal, which are supplied to the control unit 31 via a signal line 35. The control unit 31 is connected to the

Proportional magnet 30 via a first control line 33 and connected to the injection pump 32 via a second control line 34.

By the appropriate control of the

Proportional magnet 30 and the injection pump 32, it is not only possible to store braking energy and then by generating an additional torque to the PTO shaft 6 through the hydrostatic

Recirculating piston-free machine 12, but it is also a traction interruption-free acceleration of the vehicle possible, although in the mechanical transmission 3, a gear change is performed. The possible power flows within the transmission 3 will be explained in more detail below with reference to FIGS. 2 to 4.

1, the preferred embodiment using a first memory 13 and a second memory 14 is shown. However, it is also possible to provide only a high-pressure accumulator. The use of the first memory as a low-pressure accumulator has the advantage that there is always a defined inlet pressure on the suction side of the hydrostatic piston engine 12.

In a manner not shown, for example, the check valve 17 can be controlled electromagnetically. For this purpose, preferably also a control signal can be predetermined by the control unit 31, which is e.g. upon reaching a certain speed, which is selected primarily to a connecting drive, the check valve 17 is triggered and thus causes an interruption of the second storage line 16.

2, a first embodiment of a transmission 3 is shown in a greatly simplified manner. The transmission 3 is designed as a single-stage transmission, so that only two transmission shafts are arranged in the transmission 3.

The transmission 3 comprises a transmission input shaft 37 and a transmission output shaft 5. With the

Transmission input shaft 37 is connected via a first clutch 38, a drive shaft 39 of the hydrostatic piston engine 12 connectable. While the hydrostatic piston engine 12 is connected via its drive shaft 39 and the first clutch 38 to the transmission input shaft 37 which forms the PTO shaft 6 in the first embodiment, the drive input shaft 2 is connected to the shaft end of the transmission input shaft 37 shown on the left in FIG. Around To be able to produce an interruption in the connection between the drive motor 2 and the hydrostatic piston machine 12, a second clutch 40 is provided, which is connected to the drive motor 2 end of the transmission input shaft 37 of the with

Drive shaft 39 connectable end of the transmission input shaft 37 separates.

The transmission input shaft 37 cooperates over a total of three gear pairs 41, 42 and 43 with the transmission output shaft 5, which, however, form a gear stage. These are fixed-gear idler pairs, in each of which a rotationally fixed connection is generated by a sliding sleeve between a loose wheel and the transmission input shaft 37 and the transmission output shaft 5. To achieve a low driving speed, the first gear pair 41 is provided. When a higher speed is achieved with the first gear pair 41, the shift sleeve is shifted so that the idler gear of the gears of the first gear pair 41 can rotate freely and simultaneously both gears of the second gear stage 42 rotatably with the

Transmission input shaft 37 and the transmission output shaft 5 are connected. Accordingly, the rotationally fixed connection of the idler gear of the second gear pair 42 is separated and the idler gear of the third gear pair 43 connected to engage the highest gear to the transmission input shaft 37 and the transmission output shaft 5.

In the described embodiment, the second clutch 40 is disposed between the second gear pair 42 and the third gear pair 43. If the vehicle is in the push mode, the second clutch 40 is opened in a non-separable connection of the drive motor 2 with the end of the transmission input shaft 37, so that the power flow between the drive motor 2 and the hydrostatic piston machine 12 is interrupted. Due to the inertia of the vehicle is at the drive wheels 10, 11 generates a drive torque which is transmitted via the transmission output shaft 5 and the third gear pair 43 to the transmission input shaft 37 at its piston machine side shaft end. The hydrostatic piston engine 12 is thus in

Sliding operation via the transmission output shaft 5 and the power take-off shaft 6 forming the transmission input shaft 37 is driven. This is indicated schematically in FIG. 2 by the arrows. For this purpose, the first clutch 38 is closed. During a subsequent acceleration, a torque is transmitted due to the pressure in the second reservoir 14 through the hydrostatic piston engine 12, which is transmitted through the drive shaft 39 and the closed clutch 38 to the piston machine side end of the transmission input shaft 37. By the meshing gears of the third gear pair 43, the torque generated by the hydrostatic piston engine 12 is forwarded to the rear axle 4. During the acceleration, the second clutch 40 can also be closed and additionally a drive torque can be generated by the drive motor 2.

The second clutch 40 is dispensable when a clutch is provided on the input side of the transmission 3, with the drive motor 2 can be completely uncoupled from the transmission input shaft 37, for example, during a switching operation. In the illustrated embodiment of FIG. 2, the transmission input shaft 37 simultaneously forms the power take-off shaft 6.

In contrast, the transmission 3 ', as shown schematically in FIG. 3, is designed as a two-stage transmission. The connection between the

Transmission input shaft 37 'and the transmission output shaft 5 takes place via an intermediate shaft 45. As in the embodiment of FIG. 2, a first, a second and a third gear pair 41', 42 'and 43' provided to different translation stages for reducing the input speed of the transmission input shaft

37 to be able to select. In addition, a further gear 46 is provided, via which the power take-off shaft 6 and in the simplified representation, the first clutch

38 is connected to the third gear pair 43 '. The additional gear 46 is connected via the first clutch 38 to the drive shaft 39. The gear pairs 41 ', 42' and 43 'in turn each have a loose wheel which is rotatably connected to the transmission input shaft 37, the intermediate shaft 45 and the transmission output shaft 5, for example by a shift sleeve.

During kinetic energy by driving the hydrostatic piston machine 12 in the sliding or

Braking operation is stored, the separation between the hydrostatic piston engine 12 and the drive motor 2 is therefore possible by appropriate disengagement of the shift sleeve. With respect to the transmission input shaft 37, the transmission 3 is then idling.

Another embodiment is shown in FIG. 4. Like the embodiment of FIG. 3, the transmission 3 '' of FIG. 4 is designed as a two-stage transmission and therefore includes in addition to the

Transmission input shaft 37 'and the transmission output shaft 5, an intermediate shaft 45'. In contrast to the exemplary embodiment of FIG. 3, in this case the intermediate shaft 45 'also forms the auxiliary output shaft 6.

The hydrostatic piston engine 12 can be connected via a first clutch 38 as in the embodiment of FIG. About the first clutch 38, the PTO shaft 6 is rotatably connected to the drive shaft 39. Between the intermediate shaft 45 'and the

Transmission output shaft 5 is the power transmission via the third gear pair 43 'or a fourth gear pair 44. The two gear pairs 43' and 44 each have in turn a loose wheel, so that alternately between the gear ratio of the third gear pair 43 'and the gear ratio of the fourth gear pair 44 can be switched. During the storage of kinetic energy, however, are the shift sleeves of the gear pairs 41 'and 42' in their idle position. By appropriately switching between the gear ratios of the third gear pair 43 'and the fourth gear pair 44, the speed of the PTO shaft 6 can be adjusted so that the hydrostatic piston engine 12 operates in an optimized efficiency range. This means that, for example, at higher driving speeds, the third gear stage 43 'is used for power transmission. If, however, the vehicle slows down and thus drops the speed of the hydrostatic piston engine 12, so by moving the

Shift sleeve switched to the fourth gear pair 44, so that now the hydrostatic piston engine 12 operates again in a higher speed range. This can further increase the efficiency of energy recovery.

The simplified transmission illustrated in the embodiments, for example, be a synchronized transmission, a power shift transmission or a dog clutch transmission. The power take-off shaft 6 can either be an already existing power take-off shaft of an inserted transmission, or else an additional power take-off shaft can be provided as a supplement to other power take-off shafts. The solution according to the invention has the particular advantage that existing travel drives in which the transmission is equipped with a power take-off shaft can be retrofitted for regenerative braking operation.

In the illustrated and described in detail embodiments, the coupling shaft is designed as a power take-off shaft 6. On the other hand, a higher degree of integration is achieved if within the transmission also the hydrostatic piston engine is arranged. In this case, the coupling shaft is directly connected to or formed by the pump shaft of the hydrostatic piston engine.

The invention is not limited to the illustrated embodiments. Rather, the features of the individual embodiments can be combined with each other in a modified form.

Claims

claims

1. drive with a drive motor (2) with a hydrostatic piston machine (12) and at least one memory associated therewith (14), characterized in that with the drive motor (2) connected to the transmission (3, 3 ', 3' ') a transmission output shaft (5) and at least one coupling shaft (6) is provided and that the hydrostatic piston machine (12) is connected to the coupling shaft (6).

2. Drive according to claim 1, characterized in that the hydrostatic piston engine (12) via a first coupling (38) with the coupling shaft (6) is connected.

3. Drive according to claim 1 or 2, characterized in that the drive motor (2) via a clutch from a Getriebeeinganswelle (37) is uncoupled.

4. Drive according to one of claims 1 to 3, characterized in that a Getriebeeinganswelle (37) forms the coupling shaft (6) and a second clutch (40) in the transmission input shaft (37) is arranged.

5. Drive according to claim 4, characterized in that the second clutch (40) between a gear stage (43) of the highest gear ratio and a Gear stage (42) of the second highest gear ratio is arranged.

6. Drive according to one of claims 1 to 3, characterized in that the transmission (3 ') has a transmission input shaft (37), a transmission output shaft (5) and an intermediate shaft (45), wherein the intermediate shaft (45) via a respective gear stage with the coupling shaft (6) and with the transmission output shaft (5) is connected.

7. Drive according to one of claims 1 to 3, characterized in that the transmission (3 ') has a transmission input shaft (37), a transmission output shaft (5) and an intermediate shaft (45), wherein the intermediate shaft (45'), the coupling shaft ( 6).

8. Drive according to claim 7, characterized in that the intermediate shaft (45 ') and the transmission output shaft (5) via at least a first gear stage and a second gear stage is alternately connectable.

9. Drive according to one of claims 1 to 8, characterized in that the coupling shaft is a power take-off shaft (6).

10. Drive according to one of claims 1 to 8, characterized in that the hydrostatic piston engine (12) in the transmission (3, 3 ', 3 ") is arranged.

11. Drive according to one of claims 1 to 10, characterized in that a speed of the hydrostatic piston engine (12) via at least two gear ratios of the transmission (3, 3 ', 3'') is adaptable to a vehicle speed.