JP2012020711A - Braking energy recovering device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively recover braking energy when braking a vehicle related with a braking energy recovering device of a vehicle carrying an internal combustion engine.SOLUTION: A braking energy regeneration device 10 of a vehicle carrying an internal combustion engine 11, includes: an exhaust compressor 15 which takes out and compresses exhaust which flows an exhaust passage 23; a gear shifter 14 which shifts gear and transmits rotation of the internal combustion engine 11 to an exhaust compressor 15; a pressure vessel 18 which stores the exhaust supplied from the exhaust compressor 15 by high pressure; and a controller 60 which controls the gear ratio of the gear shifter 14. The controller 60 is made to set the gear ratio higher when the rotation of the internal combustion engine 11 is lower when controlling the vehicle.

Description

  The present invention relates to a braking energy recovery device for a vehicle equipped with an internal combustion engine.

  Conventionally, high pressure EGR devices and low pressure EGR devices are known as EGR devices. The high-pressure EGR device includes a high-pressure EGR passage that communicates an engine exhaust manifold and an intake manifold, and a high-pressure EGR cooler and a high-pressure EGR valve are provided in the high-pressure EGR passage so that exhaust gas is recirculated from the exhaust manifold to the intake manifold. It is.

  The low-pressure EGR device includes a low-pressure EGR passage that connects an exhaust passage located downstream of the supercharger and an intake passage located upstream of the supercharger, and the low-pressure EGR passage includes a low-pressure EGR cooler and A low pressure EGR valve is provided to recirculate exhaust gas from the exhaust passage to the intake passage.

  The control of the EGR gas amount of these EGR devices is generally a MAF control method. The MAF control method includes, for example, a new air amount map using the engine speed and fuel load as parameters, and controls the EGR gas amount based on the new air amount map and the engine operating state.

JP 2000-8963 A JP 2009-18893 A

  By the way, when the driver suddenly depresses the accelerator to accelerate the vehicle rapidly, the engine enters a transient operation state in which the load increases rapidly. Then, a response delay (turbo lag) of the supercharger occurs during the transient operation of the engine, and the supercharging pressure does not increase to the pressure set during the steady operation of the engine, thereby reducing the supercharging amount. In addition, when the supercharging pressure does not rise above a predetermined value, the input fuel amount is also suppressed in order to suppress the generation of soot. Therefore, when performing the MAF control method, the target EGR amount set under the steady operation condition cannot be added during the transient operation of the engine. Further, since the amount of supercharging and the amount of injected fuel can be suppressed, the acceleration of the vehicle can also be suppressed.

  In order to solve such a problem, for example, the exhaust discharged from the engine is pressurized by an exhaust compressor that is driven from the axle via a gear, and the pressurized exhaust is stored in a pressure vessel so that the engine can be operated transiently. It is conceivable to sometimes compensate for the lack of supercharging due to the turbo lag by discharging exhaust gas from the pressure vessel to the intake passage. In such a configuration, an electromagnetic clutch may be provided between the gear and the exhaust compressor, and the braking energy of the vehicle may be recovered by driving the exhaust compressor with the electromagnetic clutch in contact when the vehicle is braked. .

  However, since the exhaust compressor is driven by the power transmitted from the axle via the gears, for example, if the axle rotational speed decreases during braking of the vehicle, the auxiliary braking force also decreases, effectively reducing the braking energy of the vehicle. There is a possibility that it cannot be recovered.

  The present invention has been made in view of the above points, and an object of the present invention is related to a braking energy recovery device for a vehicle equipped with an internal combustion engine, which effectively recovers braking energy during braking of the vehicle and reduces the braking energy during braking. An object of the present invention is to provide a braking energy recovery device capable of maintaining a high engine braking force in a rotational range.

  To achieve the above object, a braking energy recovery device for a vehicle according to the present invention is a braking energy recovery device for a vehicle equipped with an internal combustion engine, and extracts and compresses exhaust flowing through an exhaust passage of the internal combustion engine. A transmission that shifts the rotation of the internal combustion engine and transmits it to the exhaust compressor, a pressure vessel that stores exhaust gas supplied from the exhaust compressor at a high pressure, and a control that controls a transmission gear ratio of the transmission And the control means sets the gear ratio higher as the rotation of the internal combustion engine is lower during braking of the vehicle.

  The EGR substitute device further includes an EGR device that recirculates the exhaust gas flowing through the exhaust passage to the intake passage of the internal combustion engine, and an EGR substitute device that discharges the exhaust gas stored in the pressure vessel to the intake passage. The exhaust gas stored in the pressure vessel may be discharged to the intake passage during the transient operation of the internal combustion engine.

  The turbocharger further includes a compressor provided in the intake passage and a turbine provided in the exhaust passage, and the EGR device is upstream of the exhaust passage and the compressor positioned downstream of the turbine. You may make it connect the said intake passage located in.

  The turbocharger further includes a compressor provided in the intake passage and a turbine provided in the exhaust passage, and the EGR device includes the exhaust passage located upstream of the turbine and the downstream of the compressor. You may make it connect the said intake passage located in.

  According to the vehicle braking energy recovery device of the present invention, it is possible to effectively recover braking energy during braking of the vehicle and to maintain a high engine braking force in a low rotation range during braking.

It is a schematic diagram of a braking energy recovery device showing one embodiment of the present invention. 1 is an intake / exhaust system diagram of a braking energy recovery apparatus showing an embodiment of the present invention. It is a control flowchart of the braking energy collection | recovery apparatus which shows one Embodiment of this invention. (A) is a graph which shows the relationship between the cylinder volume and cylinder internal pressure of the internal combustion engine which concerns on one Embodiment of this invention. (B) is the graph which expanded (a). It is an intake-exhaust-system figure of the braking energy recovery apparatus which shows other embodiment.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

  1 to 4 illustrate a braking energy recovery device 10 according to an embodiment of the present invention. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, the drive system of the braking energy recovery apparatus 10 according to this embodiment includes a diesel engine (hereinafter referred to as an engine) 11 mounted on a vehicle, and a mechanical automatic transmission ( An axle 12 connected via an unillustrated), left and right drive wheels 13R, 13L connected to the axle 12 via a differential or drive shaft, and a continuously variable transmission ( (Transmission) 14, an exhaust compressor 15 that pressurizes exhaust, an electromagnetic clutch 17 that enables connection and disconnection of the output shaft of the continuously variable transmission 14 and the drive shaft of the exhaust compressor 15, and supply from the exhaust compressor 15 A pressure vessel 18 (see FIG. 2) that stores the exhaust gas to be discharged at a high pressure, and an EGR substitution device 19 that substitutes an air-fuel mixture of the exhaust gas and the atmosphere supplied from the pressure vessel 18 as EGR gas.

  As shown in FIG. 2, an intake passage 20 is connected to the engine 11 via an intake manifold 28. The intake passage 20 is provided with an intake throttle 26 and a compressor 31 constituting a turbocharger 30 in order from the upstream side.

  Further, as shown in FIG. 2, a high pressure exhaust passage 23 that guides high pressure exhaust through an exhaust manifold 22 is connected to the engine 11. The high pressure exhaust passage 23 is provided with a turbine 32 that constitutes a turbocharger 30, and a low pressure exhaust passage 24 is connected to the turbine 32. The low-pressure exhaust passage 24 is provided with a particulate filter (hereinafter referred to as DPF) 33 that collects particulate matter in the exhaust and a NOx catalyst 34 that purifies nitrogen compounds in the exhaust.

  As shown in FIG. 2, the low-pressure exhaust passage 24 between the DPF 33 and the NOx catalyst 34 and the intake passage 20 between the intake throttle 26 and the compressor 31 are part of the exhaust discharged from the engine 11. Are communicated by a low pressure EGR device 40 for recirculating the air.

  As shown in FIG. 2, the low pressure EGR device 40 includes a low pressure EGR passage 41, a low pressure EGR cooler 42, and a low pressure EGR valve 43. Further, an EGR branch passage 44 connected to the exhaust compressor 15 is provided in the low pressure EGR passage 41 between the low pressure EGR cooler 42 and the low pressure EGR valve 43.

  As shown in FIG. 2, a three-way valve 45 is provided in the EGR branch passage 44. The three-way valve 45 functions to selectively switch between exhaust from the engine 11 and fresh air and supply the exhaust to the exhaust compressor 15.

  The exhaust compressor 15 pressurizes exhaust gas supplied from the EGR branch passage 44 via the three-way valve 45, and is driven by power transmitted from the axle 12 via the continuously variable transmission 14 and the electromagnetic clutch 17. . In other words, the exhaust compressor 15 is driven by the power transmitted from the axle 12 via the continuously variable transmission 14 and the pressurized exhaust when the electromagnetic clutch 17 is controlled (ON) by the ECU 60 described later. Is supplied to the pressure vessel 18. The exhaust compressor 15 and the pressure vessel 18 are communicated with each other by a supply passage 46.

  The continuously variable transmission 14 is, for example, a belt-type continuously variable transmission that transmits power with an endless belt that is hung between a primary pulley and a secondary pulley (not shown), and has a winding diameter ratio between these pulleys. Accordingly, the transmission gear ratio is configured to be stepless. The setting of the transmission ratio of the continuously variable transmission 14 is controlled by an ECU 60 described later.

  The pressure vessel 18 is configured to store the exhaust supplied from the exhaust compressor 15 at a high pressure and to send the stored exhaust to the EGR substitute device 19 during the transient operation of the engine 11. As shown in FIG. 2, the pressure vessel 18 is provided with a pressure regulating valve 47 for adjusting the maximum pressure in the vessel. The set pressure of the pressure regulating valve 47 can be set to an arbitrary value. When the pressure in the container exceeds the set value, the valve is opened and the exhaust in the container supplied from the exhaust compressor 15 is turned to the atmosphere. discharge.

  As shown in FIG. 2, the outlet of the pressure vessel 18 is connected to the intake passage 20 between the intake throttle 26 and the compressor 31 by a discharge passage 48. Further, the discharge passage 48 is provided with a regulating valve 50 and a discharge electromagnetic valve 51 that constitute the EGR substitute device 19.

  The braking energy recovery apparatus 10 configured as described above is provided with an ECU 60 that is an electronic control unit for performing various controls of the engine 11. The ECU 60 includes a known CPU, ROM, RAM, input port, output port, and the like.

  In addition, in order to perform various controls of the engine 11, an engine rotation sensor, an engine air amount sensor, an accelerator opening sensor, an in-container pressure sensor, and the like are connected to the ECU 60 through electrical wiring. The output signal is input after A / D conversion.

  Further, the ECU 60 outputs command signals to the electromagnetic clutch 17, the continuously variable transmission 14, the low pressure EGR valve 43, and the release electromagnetic valve 51, so that the electromagnetic clutch 17 is connected and disconnected, the gear ratio of the continuously variable transmission 14, The opening degree of the low pressure EGR valve 43 and the release electromagnetic valve 51 is controlled.

  Since the braking energy recovery apparatus 10 according to an embodiment of the present invention is configured as described above, for example, the following control is performed according to the flowchart shown in FIG.

  In step (hereinafter, step is simply referred to as S) 1, the key switch of the vehicle is turned ON by the driver's operation. By this operation, the power source of the braking energy recovery device 10 is turned on, and control by the ECU 60 is started.

  In S <b> 2, the ECU 60 detects the in-container residual pressure P <b> 0 that is the pressure of the gas currently stored in the pressure container 18.

  In S3, the engine 10 is started by a driver's operation.

  In S <b> 4, the ECU 60 compares the in-container residual pressure P <b> 0 with the in-container target pressure P, which is the pressure of the gas targeted for storage. If the in-container residual pressure P0 has reached the in-container target pressure P (NO), the process proceeds to S14 in order to wait for control during transition. On the other hand, if the in-container residual pressure P0 does not reach the in-container target pressure P (YES), the process proceeds to S5 to fill the exhaust and fresh air up to the in-container target pressure P.

In S5, when the pressure in the pressure vessel 18 becomes the in-container target pressure P by the ECU 60, the in-container target is set so that the ratio indicated by the exhaust gas (EGR gas) in the mixed gas in the pressure vessel 18 becomes the target value. An EGR gas partial pressure Pme is calculated. That is, the target amount of exhaust to be taken in is controlled by the partial pressure of exhaust and the partial pressure of fresh air. Since the ratio of the partial pressure of the exhaust gas in the residual gas and the partial pressure of the fresh air does not change even if the residual pressure P0 in the container changes, the gas pressure in the container
P0 + (P−P0) / P × Pe0
After the exhaust gas is additionally filled in the pressure vessel 18 until the pressure becomes, the fresh gas may be additionally filled until the in-container gas pressure reaches the in-container target pressure P. For example, if the gas pressure in the container is first set to 3.5 kg / cm ² only by exhausting, and then the fresh gas is additionally filled and the gas pressure in the container is set to 7 kg / cm ² , the ratio of the gas in the container is 50% and fresh air become 50%, and an arbitrary ratio can be obtained.

  In S 6, the electromagnetic clutch 17 is controlled to be in contact by the ECU 60, and the drive shaft of the exhaust compressor 15 is driven by the rotation of the axle 12.

  In S7, the three-way valve 45 is controlled to be ON by the ECU 60. The three-way valve 45 is configured to communicate the EGR branch passage 44 and the exhaust compressor 15 when ON, and to communicate the atmosphere and the exhaust compressor 15 when OFF. Therefore, when the three-way valve 45 is controlled to be ON, the EGR branch passage 44 and the exhaust compressor 15 are communicated with each other, and exhaust gas is taken into the exhaust compressor 15.

  In S <b> 8, the ECU 60 detects the in-container pressure Pm <b> 0 currently being filled in the compression container 18.

  In S9, the ECU 60 compares the in-container pressure Pm0 with the in-container target EGR gas partial pressure Pme. When the in-container pressure Pm0 is less than the in-container target EGR gas partial pressure Pme (YES), the process returns to S8 in order to continue the exhaust filling. On the other hand, when the in-container pressure Pm0 has reached the in-container target EGR gas partial pressure Pme (NO), the process proceeds to the patch at the break point B inserted in the flowchart.

  In SB1, the rotational speed of the axle 12 is detected by the ECU 60.

  In SB2, the ECU 60 confirms the brake operating status of the vehicle. When the vehicle is in a brake operating state (YES), the process proceeds to SB4. On the other hand, when the vehicle is in a brake non-operating state (NO), the process proceeds to SB3. Here, the presence or absence of the brake operation may be determined based on whether or not the accelerator opening is zero.

  In SB3, the gear ratio of the continuously variable transmission 14 (the rotational speed of the exhaust compressor 15 drive shaft / the rotational speed of the axle 12) is adjusted by the ECU 60. Here, the gear ratio may be a fixed value or an arbitrary variable. Thereafter, when the gear ratio of the continuously variable transmission 14 is adjusted to a fixed value or an arbitrary variable, the process proceeds to S10.

In SB4, the gear ratio of the continuously variable transmission 14 is adjusted by the ECU 60 so that the rotational speed of the drive shaft of the exhaust compressor 15 relative to the rotational speed of the axle 12 becomes a predetermined value N _c rpm. Here, the transmission ratio of the continuously variable transmission 14 is adjusted such that the predetermined value N _c rpm increases as the rotational speed of the axle 12 decreases. Thereafter, when the adjustment of the gear ratio is completed, the process returns to SB2, and this loop is repeated until the brake inoperative state is confirmed.

  In S10, the three-way valve 45 is controlled to be OFF by the ECU 60. By controlling the three-way valve 45 to be OFF, the atmosphere communicates with the exhaust compressor 15, and fresh air is taken into the exhaust compressor 15.

  In S <b> 11, the ECU 60 detects the container pressure Pm <b> 0 that is currently filling the compression container 18.

  In S12, the in-container pressure Pm0 and the in-container target pressure P are compared by the ECU 60. When the in-container pressure Pm0 is less than the in-container target pressure P (YES), the patch returns to the patch at the break point B to continue the exhaust filling. On the other hand, if the in-container pressure Pm0 has reached the in-container target pressure P (NO), the process proceeds to S13 to end the filling.

  In S13, the ECU 60 controls the electromagnetic clutch 17 to be disengaged (OFF), and the drive shaft of the exhaust compressor 15 and the axle 12 are disconnected.

  In S14, the accelerator opening is detected by the ECU 60 in order to determine the operating state of the engine 11.

  In S15, the ECU 60 confirms whether or not the engine 11 is in a transient operation state based on the accelerator depression speed dα / dt. When the stepping speed dα / dt is equal to or less than the threshold value A (NO), the process returns to S4 because it is not a transient operation state. On the other hand, when the stepping speed dα / dt exceeds the threshold value A (YES), the process proceeds to S16 because it is a transient operation state.

  In S16, the low pressure EGR valve 43 and the intake throttle 26 are controlled to be fully closed by the ECU 60, and the adjustment valve 50 and the discharge electromagnetic valve 51 of the EGR substitute device 19 are controlled to be fully opened. By such control, the high-pressure mixed gas stored in the pressure vessel 18 is discharged into the intake passage 20 and the EGR gas is substituted. Note that the time t for controlling the low pressure EGR valve 43 and the intake throttle 26 to be fully closed and the control valve 50 and the release electromagnetic valve 51 of the EGR substitute device 19 to be fully open can be set to an optimum value by experiment. Since about 1 second is sufficient, the time t is set to 1 second in this embodiment.

  In S17, the control of the low pressure EGR valve 43 and the intake throttle 26 is returned to the normal control by the ECU 60, and the regulating valve 50 and the release electromagnetic valve 51 are controlled to be fully closed, and this control is returned to S4. That is, the EGR substitution is executed by the control during the transient operation, and the mixed gas in the pressure vessel 18 is consumed, so that the filling is executed again.

  The braking energy recovery apparatus 10 according to the present embodiment achieves energy regeneration by applying the braking force to the axle 12 while compressing the exhaust gas by obtaining the driving force of the exhaust compressor 15 from the axle 12 by the control procedure. It is configured. Therefore, the vehicle braking energy recovery device 10 according to the embodiment of the present invention has the following operations and effects.

  When the ECU 60 confirms that the vehicle is in a brake operating state, the speed ratio of the continuously variable transmission 14 is such that the rotational speed of the exhaust compressor 15 drive shaft increases as the rotational speed of the axle 12 decreases. Adjusted.

  Therefore, even when the rotational speed of the axle 12 is in the low speed range during braking of the vehicle, the rotational speed of the drive shaft of the exhaust compressor 15 is maintained high, so that the replenishment time of exhaust to the pressure vessel 18 can be shortened. It is possible to effectively recover the braking energy of the vehicle. Naturally, a decrease in engine braking force in the low speed region of the axle 12 rotational speed can also be effectively suppressed.

  The rotational driving force of the axle 12 is transmitted to the driving shaft of the exhaust compressor 15 via the continuously variable transmission 14 that is adjusted to a predetermined gear ratio by the ECU 60.

  Therefore, even when the rotational speed of the axle 12 is in the low speed range, the rotational speed of the exhaust compressor 15 drive shaft can be kept high by adjusting the gear ratio of the continuously variable transmission 14, and the rotational speed of the axle 12 can be maintained. The braking energy of the vehicle can be efficiently recovered without being affected by the change of the vehicle.

  Further, when the engine 11 is in a transient operation state, the mixed gas of the exhaust gas and the atmosphere stored in the pressure vessel 18 is sent to the EGR substitute device 19 and is discharged to the intake passage 20 by the EGR substitute device 19.

  Therefore, the shortage of EGR gas caused by the turbo lag during the transient operation of the engine 11 can be solved, the NOx emission amount during the transient operation can be reduced, the acceleration performance of the vehicle can be improved, and the recovered braking Energy can be effectively regenerated in the engine 11.

  Here, in FIGS. 4A and 4B, in the transient operation of the engine 11, in the braking energy recovery apparatus 10 according to the present embodiment, an air-fuel mixture stored in the pressure vessel 18 is substituted for EGR. Comparison example (performance test result) between the case where the device 19 discharges to the intake passage 20 (solid line A) and the case where the mixture of the exhaust gas and the atmosphere stored in the pressure vessel 18 is not discharged to the intake passage 20 (dashed line B) Indicates. As shown by the solid line A, the pumping work in the intake / exhaust stroke is reduced because the intake pressure rises momentarily due to the instantaneous release of the air-fuel mixture (see FIG. 4B). That is, the decrease in the pumping work is a part where the braking energy is recovered and regenerated in the engine 11, and further, the thermal efficiency of the engine 11 is rapidly increased by the release of the air-fuel mixture (FIG. 4 (a )), The effect of the present invention can be understood.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  In the present embodiment, the low-pressure EGR device 40 has been described. However, for example, the present invention can be applied to a high-pressure EGR device 70 as shown in FIG. The braking energy recovery device 10 a shown in FIG. 5 is configured to connect an exhaust branch passage 81 to the low pressure exhaust pipe 24 downstream of the NOx catalyst 34 and extract exhaust to the exhaust compressor 15 via a cooler 82. The high-pressure EGR device 70 includes a high-pressure EGR passage 71 that connects the high-pressure exhaust passage 23 located upstream of the turbine 32 and the intake passage 20, a high-pressure EGR cooler 72 provided in the high-pressure EGR passage 71, And an EGR valve 73. In this case, the same effects as those of the above-described embodiment can be obtained.

  In the present embodiment, the continuously variable transmission 14 has been described. However, for example, a stepped transmission can be applied instead of the continuously variable transmission 14.

  Further, the continuously variable transmission 14 does not need to be interposed on the axle 12, and may be provided so as to extract power from a crankshaft (not shown) of the engine 11, for example.

  Further, when the continuously variable transmission 14 or the stepped transmission is provided with a coupling mechanism, the electromagnetic clutch 17 need not be provided.

10 Braking energy recovery device 11 Diesel engine (internal combustion engine)
14 continuously variable transmission (transmission means)
DESCRIPTION OF SYMBOLS 15 Exhaust compressor 18 Pressure vessel 19 EGR substitute apparatus 20 Intake passage 23 High-pressure exhaust passage (exhaust passage)
30 Turbocharger 31 Compressor 32 Turbine 40 Low pressure EGR device (EGR device)
60 ECU (control means)

Claims (4)

A braking energy recovery device for a vehicle equipped with an internal combustion engine,
An exhaust compressor that extracts and compresses exhaust flowing through the exhaust passage of the internal combustion engine;
A transmission for shifting the rotation of the internal combustion engine and transmitting it to the exhaust compressor;
A pressure vessel for storing the exhaust gas supplied from the exhaust compressor at a high pressure;
Control means for controlling the gear ratio of the transmission,
The braking energy recovery device for a vehicle, wherein the control means sets the speed ratio higher as the rotation of the internal combustion engine is lower during braking of the vehicle. An EGR device that recirculates exhaust flowing through the exhaust passage to the intake passage of the internal combustion engine;
An EGR substitute device that discharges exhaust gas stored in the pressure vessel to the intake passage;
The braking energy recovery device for a vehicle according to claim 1, wherein the EGR substitute device discharges exhaust gas stored in the pressure vessel to the intake passage during transient operation of the internal combustion engine. A turbocharger further comprising a compressor provided in the intake passage and a turbine provided in the exhaust passage;
The braking energy recovery device for a vehicle according to claim 2, wherein the EGR device communicates the exhaust passage located downstream from the turbine and the intake passage located upstream from the compressor. A turbocharger further comprising a compressor provided in the intake passage and a turbine provided in the exhaust passage;
The braking energy recovery device for a vehicle according to claim 2, wherein the EGR device communicates the exhaust passage located upstream from the turbine and the intake passage located downstream from the compressor.

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