JP2005299470A - Warm-up control method of low compression ratio engine in diesel hybrid vehicle - Google Patents

Abstract

There is provided a warm-up control method for a low compression ratio engine in a diesel hybrid vehicle capable of suppressing exhaust of unburned gas and warming up early.
An engine coolant temperature is read (step S10), and if it is determined that the engine is cold (step S11 affirmative), a water temperature correction calculated from the engine coolant temperature, the fuel injection amount, and the engine speed. By adding the supercharging pressure to the target supercharging pressure after warming up, the cold target supercharging pressure is calculated (steps S12 and S13), and the actual supercharging pressure is smaller than the cold target supercharging pressure. Sometimes (Yes in step S14), the nozzle opening of the variable nozzle turbocharger 26 is controlled to the closed side (step S15), and the power generation amount by the motor generator is further increased to increase the engine output (step S16). When the actual supercharging pressure is larger than the cold target supercharging pressure (No at Step S14), the nozzle opening degree is controlled to the open side (Step S17).
[Selection] Figure 1

Description

  The present invention relates to a warm-up control method for a low compression ratio engine in a diesel hybrid vehicle. More specifically, the present invention relates to a low compression in a diesel hybrid vehicle that can suppress unburned gas emission and warm up early. The present invention relates to a ratio engine warm-up control method.

  In recent years, various diesel engines and diesel hybrid vehicles equipped with the same have been provided from the viewpoint of conservation of the global environment and resource saving. For example, a low-compression-ratio and high-supercharged diesel engine equipped with an exhaust turbocharger has been proposed (see, for example, Patent Document 1), and diesel that controls the operation of the diesel engine in an operating region that is as efficient as possible. A hybrid vehicle has been proposed (see, for example, Patent Document 2).

  As a related technique, a variable capacity turbocharger control device has been proposed that increases the throttle amount of the variable nozzle in the cold compared to the warm, thereby improving acceleration and warm-up. (For example, refer to Patent Document 3). Also, a supercharge control device for a mechanical supercharger that operates by heating the supercharger when it is cold, and has a technology for switching the intake air to the intercooler bypass passage side during cold supercharging. It has been proposed (see, for example, Patent Document 4).

JP-A-63-45415 JP 2003-65099 A JP-A-10-77856 JP-A-5-26049

  However, in the above prior art, as the compression of diesel engines progresses, lowering of the combustion temperature is promoted, and emissions of hydrocarbons (HC), carbon monoxide (CO), etc., which are unburned gases, are promoted. Increase has become a problem.

  In particular, during cold start, if the temperature of the combustion chamber wall surface, exhaust manifold, and other surrounding parts is low and the same control as after warm-up is completed, only the vicinity of the wall surface is excessively cooled, and unburned gas There has been a problem that increases.

  The occurrence of such a phenomenon was remarkable in a low compression ratio diesel engine having a compression ratio of less than 17. Therefore, in a hybrid vehicle equipped with such a low compression ratio diesel engine, the control of increasing the engine load by increasing the power generation amount by the engine output increases the amount of unburned gas discharged and increases the engine warming. It took a lot of time to complete the machine.

  The present invention has been made in view of the above, and provides a warm-up control method for a low compression ratio engine in a diesel hybrid vehicle that can suppress the discharge of unburned gas and can be warmed up early. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, a warm-up control method for a low compression ratio engine in a diesel hybrid vehicle according to claim 1 of the present invention is either a low compression ratio diesel engine or a motor using battery power. In a warm-up control method of a low compression ratio engine in a diesel hybrid vehicle configured to be capable of driving a wheel drive shaft by one or both, the diesel hybrid vehicle generates charging by the engine output and charges the battery; The warm-up determination means for determining the warm-up state of the engine, the variable nozzle turbocharger that adjusts the flow rate of the exhaust gas by changing the opening of the variable nozzle and increases the intake amount by using the exhaust gas pressure, and the variable Variable nozzle control means for controlling the opening of the nozzle, When the engine determining means determines that the engine is cold, the variable nozzle control means controls the opening of the variable nozzle to be closed compared to the equivalent fuel injection amount after warming up. The amount of power generated by the charging means is increased to increase the engine output.

  According to a second aspect of the present invention, there is provided a warm-up control method for a low compression ratio engine in a diesel hybrid vehicle according to the first aspect, wherein the diesel hybrid vehicle has a boost pressure of the variable nozzle turbocharger. Supercharging pressure detection means for detecting or estimating is further provided, and when the warm-up determination means determines that the engine is cold, it is calculated from the engine coolant temperature, the fuel injection amount, and the engine speed. By adding the water temperature correction boost pressure to the target boost pressure after warming up, the cold target boost pressure is calculated, and the actual boost pressure obtained by the boost pressure detection means is When the pressure is smaller than the target supercharging pressure, the opening of the variable nozzle is controlled to the closed side.

  According to the warm-up control method for a low compression ratio engine in the diesel hybrid vehicle according to the present invention (Claim 1), when the engine is cold (during cold start), the opening degree of the variable nozzle is low in the low compression ratio diesel engine. By controlling to the closing side, the supercharging pressure increases and the temperature in the combustion chamber is increased. As a result, emission of hydrocarbons (HC), which are unburned gases, can be suppressed, and emissions can be improved. At the same time, the power generation amount is increased by the charging means and the engine output is increased. Therefore, the combustion gas temperature can be further increased in combination with the increase in the temperature in the combustion chamber by the closing side control of the nozzle opening, and the early warm-up Is planned.

  Further, according to the warm-up control method for the low compression ratio engine in the diesel hybrid vehicle according to the present invention (Claim 2), the target boost pressure during the cold state is set to the value after the completion of the warm-up according to the cold state. Since it can be set larger than the target supercharging pressure, it is possible to increase the gas temperature that touches the combustion chamber wall surface during cold, and to suppress the discharge of hydrocarbons (HC) that are unburned gas, Emissions can be improved.

  Embodiments of a warm-up control method for a low compression ratio engine in a diesel hybrid vehicle according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  First, a schematic configuration of a diesel hybrid vehicle will be described with reference to FIGS. 2 and 3. Here, FIG. 2 is a schematic diagram showing a schematic configuration of a diesel hybrid vehicle, and FIG. 3 is a schematic diagram showing a diesel engine equipped with a variable nozzle turbocharger.

  As shown in FIG. 2, the diesel hybrid vehicle 10 is provided with a low compression ratio diesel engine 11 as a travel drive source. This compression ratio is a value of 17 or less, for example. As shown in FIG. 3, the diesel engine 11 includes a common rail fuel injection system 11 a that controls the fuel injection amount, and also includes a variable valve timing mechanism that variably controls a valve opening / closing operation timing (not shown).

  Although not shown, the diesel engine 11 is a water temperature sensor that detects the temperature of engine cooling water, or a supercharging pressure sensor that detects an actual supercharging pressure by a variable nozzle turbocharger 26 (supercharging pressure detection). Means), and a rotational speed sensor for detecting the engine rotational speed. The actual supercharging pressure may be directly detected by the sensor means, or may be estimated from a map or the like created in advance through experiments or the like.

  As shown in FIG. 3, the diesel engine 11 is a variable nozzle that drives the coaxial compressor 26 a by rotating the turbine 26 b using the exhaust gas pressure discharged from the exhaust manifold 30 a to increase the intake air amount. A turbocharger 26 is provided. The intake passage 21 is provided with an air flow meter 22 for detecting the intake air amount, an intercooler 28 for cooling the intake air whose temperature has risen through the compressor 26a, and a throttle valve 24 for adjusting the intake air amount.

  The variable nozzle turbocharger 26 is constituted by known means. That is, in the variable nozzle turbocharger 26, although the internal structure is not shown, an exhaust gas passage is formed along the rotational direction of the turbine 26b so as to surround the outer periphery of the turbine 26b. Is provided with a variable nozzle for making the flow rate of the exhaust gas blown to the turbine 26b variable.

  This variable nozzle includes a plurality of nozzle vanes and an actuator for opening and closing these nozzle vanes. The nozzle vanes are arranged at equal angles around the axis of the turbine 26b, and are opened and closed by an actuator in a state of being synchronized with each other. In addition, this actuator is comprised by the pulse motor etc., and is controlled by ECU mentioned later.

  The flow rate of the exhaust gas blown to the turbine 26b is adjusted by opening and closing each nozzle vane in synchronization and changing the size of the gap between adjacent nozzle vanes. By adjusting the flow rate of the exhaust gas as described above, the rotational speed of the turbine 26b is adjusted, and as a result, the amount of air forcedly fed into the combustion chamber is adjusted.

  In addition, as shown in FIG. 3, in the exhaust passage 30 of the diesel engine 11, in order to purify particulate matter and nitrogen oxide (NOx) in the exhaust gas, a particulate filter carrying a NOx storage reduction catalyst is supported. 33 is provided.

  The diesel engine 11 includes an exhaust gas recirculation device (hereinafter referred to as an EGR device) 35 that recirculates a part of the exhaust gas to the intake system. In the EGR passage 36 of the EGR device 35, an EGR catalyst 39, an EGR cooler 37, and an EGR valve 38 are provided.

  That is, the EGR gas that has passed through the EGR catalyst 39, the EGR cooler 37, and the EGR valve 38 is compressed by the compressor 26a of the variable nozzle turbocharger 26 and is supplied to the combustion chamber from the intake manifold 21a together with the fresh air that has passed through the intercooler 28. It has become so.

  The driving force generated by the diesel engine 11 is driven through a stepped transmission (hereinafter referred to as MMT (multimode manual transmission)) 12, a drive shaft (wheel drive shaft) 14, and a differential gear 15 that can be automatically shifted. 13 is transmitted. The MMT 12 electrically and automatically controls a gear shift operation by an actuator in accordance with a traveling state.

  Between the diesel engine 11 and the MMT 12, there is provided a clutch 12a that performs contact and separation of power transmission, and the contact and separation operation is automatically and electrically controlled by an actuator in accordance with the traveling state.

  Further, the diesel engine 11 is configured such that its fuel injection amount, intake air amount, and the like are controlled in order to output the requested engine torque commanded from the MMT 12. The required fuel injection amount of the diesel engine 11 is determined based on, for example, a map from the engine speed and the accelerator opening, and fuel injection is executed.

  A motor generator (charging means) 17 in which a drive system gear unit (gear train) is integrated is connected to a battery 20 that is a chargeable / dischargeable secondary battery via an inverter 19 and functions as a motor that is a travel drive source. Power running operation mode, and a regenerative operation mode that functions as a generator.

  For example, the motor generator 17 receives power supplied from the battery 20 in the power running operation mode, and generates power for driving the drive shaft 14. In the regenerative operation mode, the motor generator 17 converts the driving force transmitted from the diesel engine 11 or the drive shaft 14 into electric power and charges the battery 20. The diesel hybrid vehicle 10 includes an alternator (not shown) as a charging unit that generates electric power by engine output and charges the battery 20.

  Whether the motor generator 17 is operated in the power running operation mode or the regenerative operation mode is determined in consideration of a charge amount SOC (State of Charge) of the battery 20.

  The diesel hybrid vehicle 10 configured as described above is basically controlled as follows based on output information from various sensors by an electronic control unit (hereinafter referred to as ECU) (not shown), and travels in various states. be able to.

  The ECU also functions as a warm-up determination unit that determines the warm-up state of the diesel engine 11 from the detection value of the water temperature sensor and a variable nozzle control unit that controls the nozzle opening of the variable nozzle turbocharger 26. It is.

  In a relatively low speed state in which the diesel hybrid vehicle 10 has started traveling, the vehicle travels (EV traveling) by powering the motor generator 17 while the diesel engine 11 is stopped. Then, when the diesel hybrid vehicle 10 reaches a predetermined speed or load after the start of traveling, the diesel engine 11 is cranked and started using the motor generator 17 and the operation is shifted to the operation using the diesel engine 11.

  Further, during steady operation, the diesel engine 11 is normally operated so as to generate an output substantially equal to the required power of the drive shaft 14. At this time, almost all of the output of the diesel engine 11 is transmitted to the drive shaft 14.

  On the other hand, when the charge amount SOC of the battery 20 is reduced to a predetermined reference value or less, the diesel engine 11 is operated with an output exceeding the required power of the drive shaft 14, and a part of the surplus power is a motor. It is regenerated as electric power by the generator 17 and used for charging the battery 20.

  When the output torque of the diesel engine 11 is insufficient, the insufficient torque is assisted by the motor generator 17 according to the charge amount SOC of the battery 20, and the necessary torque is ensured.

  The diesel hybrid vehicle 10 is also subjected to so-called eco-run (economy & ecology running) control in order to save fuel and reduce exhaust emissions. For example, when the diesel hybrid vehicle 10 stops due to a signal waiting at an intersection or the like, the diesel engine 11 is automatically stopped under a predetermined stop condition, and then the predetermined restart condition (for example, when the accelerator pedal is depressed). Thus, the diesel engine 11 is also restarted.

  The above is the basic configuration and basic control operation of the diesel hybrid vehicle 10 according to the present invention.

  Next, a warm-up control method for the low compression ratio engine in the diesel hybrid vehicle 10 that is a main part of the present invention will be described with reference to FIGS. 2 and 3 based on FIG. Here, FIG. 1 is a flowchart showing a warm-up control method for the low compression ratio engine in the diesel hybrid vehicle according to the first embodiment of the present invention. The following control is executed by the ECU.

  First, in order to determine the warm-up state of the diesel engine 11, the engine cooling water temperature detected by the water temperature sensor is read (step S10), and whether or not the engine cooling water temperature is less than a predetermined value (for example, 60 ° C.). Is determined (step S11). If it is determined that it is cold, the process proceeds to step S12 to perform warm-up control (Yes in step S11). If it is determined that it is not cold, normal operation after completion of warm-up is performed. Is controlled based on the base map (No in step S11).

  As described above, in a diesel engine equipped with a variable nozzle turbocharger according to the prior art, the target supercharging pressure is set to the same target value before and after the completion of warm-up. It has not been considered that the vicinity of each part of the exhaust manifold and other peripheral parts is excessively cooled and a large amount of hydrocarbon (HC) and carbon monoxide (CO) is generated.

  Therefore, in this embodiment, the temperature of the gas that touches the combustion chamber wall surface during cold (before completion of warm-up) is increased, and the target during cold is set to be approximately the same as the gas temperature after completion of warm-up. Set the supercharging pressure using the following procedure.

  That is, based on the engine coolant temperature read in step S10, the fuel injection amount calculated based on the driver request output, and the engine speed detected by the speed sensor, a predetermined coolant temperature (for example, 0 ° C.). By using a supercharging pressure map as shown in FIG. 4 that has been experimentally determined in advance (every several degrees C in the range of ˜80 ° C.), the target supercharging pressure during cold is corrected according to the cooling water temperature. Therefore, the water temperature correction supercharging pressure is calculated (step S12). Here, FIG. 4 is a map showing the supercharging pressure at a predetermined cooling water temperature.

  Next, the cold-time target supercharging pressure is calculated by adding the water temperature correction supercharging pressure calculated in step S12 to the target supercharging pressure after completion of warm-up (step S13). Then, it is determined whether or not the actual supercharging pressure by the variable nozzle turbocharger 26 detected by the supercharging pressure sensor is smaller than the cold target supercharging pressure calculated in step S13 (step S14).

  If the actual boost pressure is smaller than the cold target boost pressure (Yes at step S14), the nozzle opening of the variable nozzle turbocharger 26 (abbreviated as VNT opening in FIG. 1) is warmed up. Compared to the equivalent fuel injection amount after completion, the boost pressure is increased by correcting to the closed side, and control is performed so that the actual boost pressure becomes the cold target boost pressure (step S15). As a result, the temperature in the combustion chamber and the like can be increased, emission of unburned gas can be suppressed, and emission can be improved.

  Then, the power generation amount by the motor generator 17 is further increased, and the output of the diesel engine 11 is increased (step S16). As a result, the combustion gas temperature can be further increased in combination with the increase in the temperature in the combustion chamber by the closing side control of the nozzle opening in step S15, so that early warm-up can be achieved.

  On the other hand, if the actual supercharging pressure exceeds the cold target supercharging pressure (No at step S14), the nozzle opening of the variable nozzle turbocharger 26 is corrected to the open side to decrease the supercharging pressure, and the actual supercharging is achieved. Control is performed so that the pressure becomes the target boost pressure during cold (step S17).

  As described above, according to the warm-up control method for the low compression ratio engine in the diesel hybrid vehicle according to the first embodiment, it is possible to suppress the discharge of unburned gas and to warm up early.

  In the first embodiment, the present invention is applied to the parallel diesel hybrid vehicle 10, but the present invention is not limited to this and may be applied to a series hybrid vehicle.

  Further, the present invention is applied to the hybrid vehicle including the MMT 12, but the present invention is not limited to this, and the present invention may be applied to a hybrid vehicle including an automatic transmission (AT) or a manual transmission (MT).

  FIG. 5 is a schematic diagram showing a diesel engine provided with means for bypassing an intercooler according to Embodiment 2 of the present invention. In the following description, members that are the same as or correspond to those already described are assigned the same reference numerals, and redundant description is omitted.

  As shown in FIG. 5, the diesel engine 11 according to the second embodiment has an upstream side and a downstream side of the intercooler 28 in the intake passage 21 in the configuration of the diesel engine 11 according to the first embodiment (see FIG. 3). In order to bypass, an intercooler bypass passage 40 and a three-way valve 41 are further provided.

  The three-way valve 41 is controlled by the ECU so that the flow of fresh air passing through the compressor 26a can be changed to the intercooler bypass passage 40 side without passing through the intercooler 28 when necessary.

  The warm-up control of the diesel hybrid vehicle 10 configured as described above is performed in the control method shown in FIG. 1 of the first embodiment when the temperature of the combustion chamber wall surface is low and the temperature of the variable nozzle is low. In addition to the control of the turbocharger 26, the three-way valve 41 is further controlled to change the flow of fresh air passing through the compressor 26a to the intercooler bypass passage 40 side.

  That is, this intercooler bypass control can be executed together with the valve opening side closing correction control of the nozzle opening in step S15 in FIG. If the actual boost pressure reaches the cold target boost pressure by this control, the bypass control may be canceled in step S17.

  As described above, according to the warm-up control method for the low compression ratio engine in the diesel hybrid vehicle according to the second embodiment, the intake air flows into the intake manifold 21a by controlling the intake air not to pass through the intercooler 28 when cold. Thus, the temperature of the gas flowing into the combustion chamber and the temperature of the gas flowing into the combustion chamber can be increased, and the compression top dead center and the high temperature and high pressure can be controlled in the combustion process, so that the generation of unburned gas can be suppressed.

  FIG. 6 is a schematic diagram showing a diesel engine provided with means for bypassing an EGR cooler according to Embodiment 3 of the present invention. As shown in FIG. 6, the diesel engine 11 according to the third embodiment includes an upstream side and a downstream side of the EGR cooler 37 in the EGR passage 36 in the configuration of the diesel engine 11 according to the second embodiment (see FIG. 5). Are further provided with an EGR cooler bypass passage 50 and a three-way valve 51.

  The three-way valve 51 is controlled by the ECU so that the flow of the EGR gas passing through the EGR catalyst 39 can be changed to the EGR cooler bypass passage 50 side without passing through the EGR cooler 37 when necessary.

  The warm-up control of the diesel hybrid vehicle 10 configured as described above is performed in the control method shown in FIG. 1 of the first embodiment when the temperature of the combustion chamber wall surface is low and the temperature of the variable nozzle is low. In addition to controlling the turbocharger 26, the three-way valve 51 is further controlled to change the flow of EGR gas that has passed through the EGR catalyst 39 to the EGR cooler bypass passage 50 side without passing through the EGR cooler 37 when necessary.

  That is, this EGR cooler bypass control can be executed together with the valve closing side correction control of the nozzle opening in step S15 in FIG. If the actual boost pressure reaches the cold target boost pressure by this control, the bypass control may be canceled in step S17.

  As described above, according to the warm-up control method for the low compression ratio engine in the diesel hybrid vehicle according to the third embodiment, the intake manifold 21a is controlled by preventing the EGR gas from passing through the EGR cooler 37 when cold. The temperature of the gas flowing into the combustion chamber and further the temperature of the gas flowing into the combustion chamber can be increased, and the compression top dead center and the high temperature and high pressure can be controlled in the combustion process. it can.

  Since the diesel engine 11 according to the fourth embodiment is the same as the configuration of the diesel engine 11 according to the first embodiment (see FIG. 5), a duplicate description is omitted. In the control method shown in FIG. 1 of the first embodiment, the warm-up control according to the third embodiment is performed when the exhaust valve is in the intake stroke when it is cold and the temperature of the combustion chamber wall surface is low. The high-temperature exhaust gas once discharged from the combustion chamber into the exhaust manifold 30a is re-introduced into the combustion chamber during the intake stroke, thereby promoting the internal EGR.

  That is, the control for promoting the internal EGR can be executed together with the valve closing side correction control of the nozzle opening in step S15 in FIG. If the actual boost pressure reaches the cold target boost pressure by this control, the internal EGR promotion control may be canceled in step S17.

  As described above, according to the warm-up control method for the low compression ratio engine in the diesel hybrid vehicle according to the fourth embodiment, the hot exhaust gas once discharged from the combustion chamber to the exhaust manifold 30a is taken into the intake stroke when cold. By controlling to be taken into the combustion chamber again, the compression top dead center and the high temperature and high pressure can be controlled in the combustion process, so that the generation of unburned gas can be suppressed.

  As described above, the warm-up control method for a low compression ratio engine in a diesel hybrid vehicle according to the present invention is useful for a diesel hybrid vehicle aiming at early warm-up while suppressing the discharge of unburned gas, and in particular, the compression ratio. It is suitable for a hybrid vehicle equipped with a low compression ratio diesel engine of 17 or less.

It is a flowchart which shows the warm-up control method of the low compression ratio engine in the diesel hybrid vehicle which concerns on Example 1 of this invention. It is a mimetic diagram showing a schematic structure of a diesel hybrid vehicle. It is a schematic diagram which shows the diesel engine provided with the variable nozzle turbocharger. It is a flowchart which shows the warm-up control method of the low compression ratio engine in the diesel hybrid vehicle which concerns on Example 2 of this invention. It is a flowchart which shows the warm-up control method of the low compression ratio engine in the diesel hybrid vehicle which concerns on Example 3 of this invention. It is a schematic diagram which shows the diesel engine provided with the means to bypass the EGR cooler which concerns on Example 3 of this invention.

Explanation of symbols

10 Diesel hybrid vehicle 11 Diesel engine 14 Drive shaft (wheel drive shaft)
17 Motor generator (charging means)
20 battery 26 variable nozzle turbocharger

Claims (2)

In a warm-up control method for a low compression ratio engine in a diesel hybrid vehicle configured to be able to drive a wheel drive shaft by either one or both of a low compression ratio diesel engine or a battery-powered motor,
The diesel hybrid vehicle is
Charging means for generating electric power by the engine output and charging the battery;
A warm-up determination means for determining a warm-up state of the engine;
A variable nozzle turbocharger that adjusts the flow rate of the exhaust gas by changing the opening of the variable nozzle and increases the intake amount using the exhaust gas pressure;
Variable nozzle control means for controlling the opening of the variable nozzle;
Further comprising
When the warm-up determining means determines that the engine is cold,
While the opening degree of the variable nozzle is controlled by the variable nozzle control means to be closed compared to the equivalent fuel injection amount after warming up,
A warm-up control method for a low compression ratio engine in a diesel hybrid vehicle, characterized in that the amount of power generated by the charging means is increased to increase the engine output. The diesel hybrid vehicle further includes a supercharging pressure detection means for detecting or estimating a supercharging pressure of the variable nozzle turbocharger,
When the warm-up determining means determines that the engine is cold,
By adding the water temperature correction boost pressure calculated from the engine coolant temperature, fuel injection amount, and engine speed to the target boost pressure after warming up, the cold target boost pressure is calculated,
2. The opening degree of the variable nozzle is controlled to a closed side when an actual supercharging pressure obtained by the supercharging pressure detection means is smaller than the cold target supercharging pressure. A warm-up control method for a low compression ratio engine in a diesel hybrid vehicle.

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