JP2008239014A - Control device for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a hybrid vehicle improving fuel economy. <P>SOLUTION: This control device for the hybrid vehicle has an optimum flow rate learning means and an output correction means. The optimum flow rate learning means controls an electric water pump to learn an optimum flow rate of cooling water. The output correction means controls constant output of an internal combustion engine corresponding to a request torque until the optimum flow rate learning means completes the learning of the optimum flow rate after the start of the learning, and compensates for a fluctuation amount of the output of the internal combustion engine corresponding to a fluctuation amount of the request torque by controlling a rotation speed of a motor when the request torque fluctuates. Thereby, the optimum flow rate learning means can learn the optimum flow rate of the cooling water. Thereby, the optimum flow rate learning means can learn the optimum flow rate of the cooling water even if an operation state or environment changes, so that the fuel economy can be improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technical field of a control device for controlling, for example, a hybrid vehicle.

  Conventionally, a technique using an electric water pump (hereinafter referred to as “electric WP”) that circulates cooling water for cooling an engine has been proposed. For example, Patent Document 1 describes an electric WP that can sufficiently circulate cooling water even when the pressure loss of the cooling system increases. Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for detecting the in-cylinder pressure, obtaining the in-cylinder cooling loss based on the in-cylinder pressure, and controlling the cooling state of the internal combustion engine based on the cooling loss. .

JP 2002-129958 A JP 2004-169634 A

  By the way, the optimum flow rate of the cooling water may actually vary due to causes such as pressure loss of the cooling system, individual differences of the electric water pump, and aging deterioration. For this reason, when the flow rate of the cooling water is controlled with the matching map, the flow rate of the cooling water is actually controlled to be larger than the optimum flow rate obtained through experiments or the like. However, if the flow rate of the cooling water is increased, the power consumption increases, which may deteriorate the fuel efficiency. Patent Documents 1 and 2 do not discuss this point at all.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for a hybrid vehicle that can improve fuel efficiency.

  In one aspect of the present invention, a hybrid comprising an internal combustion engine, an electric motor capable of supplying power to a drive shaft connected to an axle, and an electric water pump for circulating cooling water in the internal combustion engine. The control device for the hybrid vehicle that controls the vehicle controls the electric water pump to complete the learning from the optimum flow rate learning unit that learns the optimum flow rate of the cooling water, and the optimum flow rate learning unit starts learning the optimum flow rate. In the meantime, the output of the internal combustion engine corresponding to the required torque is controlled to be constant, and when the required torque fluctuates, the number of fluctuations in the required torque is controlled by controlling the rotation speed of the motor. Output correction means for compensating for the corresponding fluctuation in the output of the internal combustion engine.

  The control apparatus for a hybrid vehicle includes an internal combustion engine, an electric motor capable of supplying power to a drive shaft connected to an axle, and an electric water pump for circulating cooling water in the internal combustion engine. . The control device for a hybrid vehicle includes an optimum flow rate learning unit and an output correction unit. These are, for example, ECUs (Electronic Control Units).

  The optimum flow rate learning means learns the optimum flow rate of the cooling water by controlling the electric water pump. Here, the optimum flow rate of the cooling water is, for example, a flow rate that can improve fuel efficiency. Further, “learning” here refers to adjustment by increasing or decreasing the flow rate of the cooling water to obtain the optimum flow rate, and after obtaining the optimum flow rate, the flow rate of the cooling water is set to the optimum flow rate. It means that.

  The output correction means controls the output of the internal combustion engine corresponding to the required torque to be constant during a period from when the optimum flow rate learning means starts learning the optimum flow rate of the cooling water to when it is completed. When it fluctuates, the fluctuation of the output of the internal combustion engine corresponding to the fluctuation of the required torque is compensated by controlling the rotation speed of the electric motor. Here, the output of the internal combustion engine is, for example, the rotational speed of the internal combustion engine. This is because even if the cooling water flow rate is changed, the wall temperature of the head block of the internal combustion engine and the water temperature of the cooling water do not change immediately in response, but after several seconds to several tens of seconds. Because it changes. Thereby, the said optimal flow volume learning means can complete the learning of the optimal flow volume of the said cooling water. In other words, the optimum flow rate learning means can learn the optimum flow rate of the cooling water even if the driving situation or environment changes, so that the fuel consumption can be improved.

  In another aspect of the hybrid vehicle control device, the optimum flow rate learning means increases the flow rate of the cooling water by controlling the electric water pump when knocking occurs in the internal combustion engine. In the case where the knocking is suppressed and thereby the fuel efficiency is improved, the flow rate of the cooling water when the knocking is suppressed is set as the optimum flow rate. As a result, fuel consumption can be improved by suppressing knocking, and the driver's uncomfortable feeling with respect to knocking sound and vibration can be suppressed.

  In another aspect of the hybrid vehicle control device, the optimum flow rate learning means adjusts the flow rate of the cooling water by controlling the electric water pump so that the cooling water temperature becomes a predetermined water temperature. The adjusted flow rate of the cooling water is set as the optimum flow rate. The predetermined water temperature here is a temperature at which troubles such as overheating and knocking of the internal combustion engine, and heat damage to the components constituting the cooling system do not occur, and are previously obtained by experiments or the like. . In this way, even if the operating condition or environment changes, the temperature of the cooling water can be set to an appropriate temperature that does not cause overheating or knocking of the internal combustion engine or cause heat damage to the parts. .

  In another aspect of the hybrid vehicle control device, the optimum flow rate learning unit controls the electric water pump so that a water temperature difference at an inlet / outlet of the cooling water of the internal combustion engine becomes a predetermined water temperature difference. The flow rate of the cooling water is adjusted, and the adjusted flow rate of the cooling water is set as the optimum flow rate. By doing so, even if the operating condition or environment changes, the water temperature difference at the inlet / outlet of the cooling water of the internal combustion engine may be displaced due to temperature distortion between the head block gasket of the internal combustion engine. In addition, it is possible to obtain an appropriate water temperature difference that does not increase the difference in combustion evaporation and combustion state between the cylinders of the internal combustion engine.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Vehicle configuration]
First, a hybrid vehicle according to each embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a diagram showing a schematic configuration of the hybrid vehicle 100. Hybrid vehicle 100 mainly includes an engine (internal combustion engine) 1, an axle 2, wheels 3, motors (motor generators) MG1 and MG2, planetary gear 4, inverter 5, battery 6, and SOC sensor 6a. , ECU (Electronic Control Unit) 20.

  The axle 2 is a part of a power transmission system that transmits the power of the engine 1 and the motor MG2 to the wheels 3. The wheels 3 are wheels of the hybrid vehicle 100, and only the left and right front wheels are particularly shown in FIG. The engine (internal combustion engine) 1 is a device that generates power by burning a mixture of supplied fuel and air. For example, the engine 1 is configured by a gasoline engine, a diesel engine, or the like. The engine 1 functions as a power source that outputs the main driving force of the hybrid vehicle 100. The engine 1 is controlled variously by the ECU 20. Specifically, the ECU 20 controls the engine speed, and controls the opening (throttle opening) of a throttle valve (not shown).

  The motor MG1 is configured to function mainly as a generator for charging the battery 6 or a generator for supplying electric power to the motor MG2. The motor MG2 is mainly configured to function as an electric motor that assists (assists) the output of the engine 1, and is configured to be able to transmit power to the axle 2. The number of revolutions of motor MG2 is controlled by ECU 20.

  These motors MG1 and MG2 are configured as, for example, synchronous motor generators, and include a rotor having a plurality of permanent magnets on the outer peripheral surface, and a stator wound with a three-phase coil that forms a rotating magnetic field. The planetary gear (planetary gear mechanism) 4 is configured to be able to distribute the output of the engine 1 to the motor MG1 and the axle 2 and functions as a power split mechanism.

  The inverter 5 is a DC / AC converter that controls power input / output between the battery 6 and the motors MG1 and MG2. For example, the inverter 5 converts the DC power taken out from the battery 6 into AC power, or supplies AC power generated by the motor MG1 to the motor MG2 and converts the AC power generated by the motor MG1 into DC power. It can be converted to and supplied to the battery 6.

  The battery 6 is a rechargeable storage battery configured to be able to function as a power source for driving the motors MG1 and MG2 and an electric water pump described later.

[Configuration of cooling system]
FIG. 2 is a diagram showing a schematic configuration of the cooling system 50 according to each embodiment of the present invention. In FIG. 2, solid arrows indicate the flow of cooling water, and broken arrows indicate input / output of signals. A solid line indicated by a bold line indicates a passage (cooling water passage) through which the cooling water flows.

  The cooling system 50 according to each embodiment cools the engine 1 using cooling water, collects exhaust heat by exchanging heat between the cooling water and the exhaust gas, and warms the engine 1. It is a system used for the machine. In this case, the cooling water cools and warms up the engine 1 by passing through the cooling water passages 17a, 17b, and 17c. Specifically, the cooling water passes through a water jacket provided around the cylinder inside the engine 1 to cool and warm up the block head of the engine 1.

  The exhaust heat recovery device 12 is provided on the cooling water passage 17a, the radiator 13 is provided on the cooling water passage 17b, and the electric pump 15 is provided on the cooling water passage 17c. In the following description, when the cooling water passages 17a to 17c are not distinguished, they are simply used as the cooling water passage 7.

  The exhaust heat recovery device 12 is provided on an exhaust passage (not shown) through which exhaust gas from the engine 1 passes. The exhaust heat recovery unit 12 recovers exhaust heat by allowing cooling water to pass through and exchanging heat between the cooling water and the exhaust gas.

  In the radiator 13, the cooling water passing through the inside thereof is cooled by outside air. In this case, cooling of the cooling water in the radiator 13 is promoted by the wind introduced by the rotation of the electric fan (not shown). The electric pump (hereinafter referred to as “electric WP”) 15 includes an electric motor, and the cooling water is circulated in the cooling water passage 17 by driving the motor. Specifically, the electric WP 15 is supplied with electric power from a battery, and the rotation speed and the like are controlled by a control signal S 15 supplied from the ECU 20.

  The thermostat 14 is configured by a valve that opens and closes according to the coolant temperature. Basically, the thermostat 14 opens when the coolant temperature becomes high. In this case, the cooling water passage 17 b and the cooling water passage 17 c are connected via the thermostat 14, and the cooling water passes through the radiator 13. Thereby, a cooling water is cooled and the overheating of the engine 1 is suppressed. On the other hand, when the coolant temperature is relatively low, the thermostat 14 is closed. In this case, the cooling water does not pass through the radiator 13. Thereby, since the water temperature fall of a cooling water is suppressed, the overcool of the engine 1 is suppressed.

  The ECU (Engine Control Unit) 20 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). As described above, ECU 20 controls the number of revolutions of engine 1 and the number of revolutions of motor MG2. As will be described in detail later, the ECU 20 controls the electric WP 15 based on detection signals supplied from various sensors so that the flow rate of the cooling water becomes the optimum flow rate. Therefore, the ECU 20 functions as an optimum flow rate learning unit and an output correction unit in the present invention.

[Control method of hybrid vehicle]
Next, a hybrid vehicle control method will be described with reference to FIG. FIG. 3 is a graph showing the relationship between the required torque from the driver and the engine speed. A graph 60 shown in FIG. 3 is a fuel efficiency optimal line (also referred to as “operation line”) at which the fuel efficiency is optimal. The fuel efficiency optimal line is obtained from the fuel efficiency map. When the engine 1 is driven, the ECU 20 controls the engine 1 at an engine speed corresponding to the torque requested by the driver on the fuel efficiency optimum line of the graph 60 shown in FIG.

  In the hybrid vehicle according to each embodiment of the present invention, the ECU 20 controls the electric WP 15 to learn the optimum flow rate of the cooling water. The “optimal flow rate” of the cooling water is a flow rate that can improve fuel efficiency, as will be specifically described later. “Learning” means that the optimum flow rate is obtained by adjusting the flow rate of the cooling water to increase / decrease, and after obtaining the optimum flow rate, the flow rate of the cooling water is set to the optimum flow rate. is there. The ECU 20 controls the output of the engine 1 corresponding to the required torque to be constant from the start to the completion of learning of the optimum flow rate of the cooling water. For example, the ECU 20 controls the rotation speed of the engine 1 corresponding to the required torque to be constant, in other words, controls the engine operating range to be constant.

  In the example shown in FIG. 3, the ECU 20 controls the engine 1 so that the engine speed corresponding to the required torque satisfies the point 61 on the fuel efficiency optimum line. Specifically, when the torque requested by the driver fluctuates, the ECU 20 controls the number of rotations of the motor 1 by controlling the number of rotations of the motor MG2. We will make up for it.

  The reason for this is as follows. That is, when learning the optimum flow rate of the cooling water, the ECU 20 changes the flow rate of the cooling water to change the wall temperature of the head block of the engine 1 or the temperature of the cooling water, thereby changing the optimum flow rate of the cooling water. learn. Here, when the ECU 20 learns the optimum flow rate of the cooling water, the engine operating range needs to be fixed. However, even if the flow rate of the cooling water is changed, the wall temperature of the head block of the engine 1 and the water temperature of the cooling water do not change immediately in response, but change after several seconds to several tens of seconds. There is a possibility that the required torque fluctuates.

  Therefore, when the required torque fluctuates between the start and completion of learning of the optimum flow rate of the cooling water, the ECU 20 controls the rotation speed of the motor MG2 to deal with the fluctuation amount of the required torque. The fluctuation of the output of the engine 1, that is, the fluctuation of the rotation speed of the engine 1 is compensated here. Thereby, ECU20 can complete learning of the optimal flow volume of cooling water. In other words, the ECU 20 can learn the optimum flow rate of the cooling water even when the driving situation or environment changes, so that the fuel consumption can be improved.

  In the first to third embodiments described below, a specific learning method of the optimum flow rate of the cooling water will be described.

[First Embodiment]
In the control apparatus for a hybrid vehicle according to the first embodiment of the present invention, the ECU 20 learns the optimum flow rate of cooling water that enables suppression of knocking. This method will be described in detail with reference to FIG.

  In this case, as shown in FIG. 4, in the cooling system 50a according to the first embodiment, the knocking sensor 22 is attached to the wall surface of the engine block, for example. The knocking sensor 22 detects vibration generated in the cylinder of the engine 1. The knocking sensor 22 supplies the ECU 20 with a detection signal S22 corresponding to the detected vibration. The ECU 20 detects whether knocking has occurred in the cylinder of the engine 1 based on the detection signal S22.

  When the ECU 20 detects that knocking has occurred, the ECU 20 controls the electric WP 15 to increase the flow rate of the cooling water until the knocking is suppressed. This is because it is necessary to cool the engine 1 in order to suppress knocking. When the ECU 20 detects that the knocking has been suppressed, the ECU 20 calculates how much the fuel consumption has been improved by suppressing the knocking. Further, since the electric power consumption of the electric WP 15 increases by increasing the flow rate of the cooling water, the ECU 20 also calculates an increase in fuel consumption corresponding to the increase in electric power consumption of the electric WP 15. This is because when the power of the electric WP 15 is large, even if the fuel efficiency is improved by suppressing knocking, the fuel consumption may be deteriorated by the electric power consumption of the electric WP 15 more than the fuel efficiency improvement.

  The ECU 20 suppresses the knocking when the fuel consumption is improved even if the fuel consumption improvement corresponding to the increase in the power consumption of the electric WP 15 is subtracted from the fuel consumption improvement due to the suppression of the knocking. The flow rate of the cooling water is learned as the optimum flow rate. By doing in this way, in the hybrid vehicle control device according to the first embodiment, it is possible to improve fuel efficiency by suppressing knocking, and to suppress a driver's uncomfortable feeling with respect to knocking sound and vibration.

[Second Embodiment]
In the control apparatus for a hybrid vehicle according to the second embodiment of the present invention, the ECU 20 learns the optimum flow rate of the cooling water that brings the cooling water temperature to an appropriate temperature. This method will be described in detail with reference to FIG.

  In this case, as shown in FIG. 5, in the cooling system 50 b according to the second embodiment, a water temperature sensor 16 a that measures the temperature of the cooling water is attached to the cooling water outlet of the engine 1. The water temperature sensor 16a supplies the ECU 20 with a detection signal S16a corresponding to the measured water temperature. Instead of the water temperature sensor 16a, a water temperature sensor 16b attached to the cooling water inlet of the engine 1 may be used. Also in this case, the water temperature sensor 16b supplies the ECU 20 with a detection signal S16b corresponding to the measured water temperature.

  In order to improve fuel efficiency, it is necessary to improve the thermal efficiency in the cylinder of the engine 1, so that the heat generated in the engine 1 is not released to the cooling water passing through the engine 1, that is, the cooling loss is reduced. It is considered better to reduce. Accordingly, it may be desirable that the coolant temperature is higher. However, if the coolant temperature is too high, various problems such as overheating of the engine 1 and knocking, and heat damage to the engine 1 and other components constituting the cooling system 50 occur.

  Therefore, in the cooling system 50b according to the second embodiment, an appropriate predetermined temperature of the cooling water that does not cause the above-described various obstacles is obtained in advance through experiments and the like. The predetermined temperature is recorded in the ROM of the ECU 20 or the like.

  The ECU 20 obtains the coolant temperature based on the detection signal S16a. When the obtained coolant temperature is different from the predetermined temperature, the ECU 20 controls the electric WP 15 until the coolant temperature matches the predetermined temperature. Adjust. The ECU 20 learns the flow rate of the cooling water when the coolant temperature matches the predetermined temperature as the optimum flow rate. Thereby, in the control apparatus of the hybrid vehicle which concerns on 2nd Embodiment, even if a driving | running condition and an environment change, the water temperature of cooling water can be made to correspond with the said predetermined temperature. That is, even if the operating condition or environment changes, the coolant temperature can be set to an appropriate temperature that does not cause overheating or knocking of the engine 1 or cause heat damage to parts.

[Third Embodiment]
In the control apparatus for a hybrid vehicle according to the third embodiment of the present invention, the ECU 20 learns the optimum flow rate of the cooling water that makes the temperature difference of the cooling water at the inlet / outlet of the engine an appropriate temperature. This method will be described in detail with reference to FIG.

  In this case, as shown in FIG. 6, in the cooling system 50 c according to the third embodiment, the water temperature sensor 16 a is attached to the cooling water outlet of the engine 1, and the water temperature sensor 16 b is attached to the cooling water inlet of the engine 1. It is done. That is, water temperature sensors are attached to both the inlet and outlet of the cooling water of the engine 1.

  If the water temperature difference at the inlet / outlet of the cooling water of the engine 1 becomes too large, a deviation due to temperature distortion occurs between the head, block, and gasket of the engine 1 or the difference in combustion evaporation / combustion state between the cylinders of the engine 1 increases. There is a harmful effect of.

  Therefore, in the cooling system 50c according to the third embodiment, an appropriate predetermined water temperature difference at the inlet / outlet of the cooling water of the engine 1 that does not cause the above-described adverse effects is obtained in advance through experiments or the like. The determined predetermined water temperature difference is recorded in the ROM of the ECU 20 or the like.

  ECU20 calculates | requires the water temperature difference in the inlet / outlet of the cooling water of the engine 1 based on detection signal 16a, 16b. Then, the ECU 20 controls the electric WP 15 when the calculated water temperature difference at the entrance / exit of the engine 1 is different from the predetermined water temperature difference, so that the water temperature difference at the entrance / exit of the cooling water of the engine 1 is the predetermined temperature difference. Adjust the cooling water flow rate until it matches the water temperature difference. The ECU 20 learns the flow rate of the cooling water when the water temperature difference at the entrance / exit of the engine 1 coincides with the predetermined water temperature difference as the optimum flow rate. Thereby, in the control apparatus of the hybrid vehicle which concerns on 3rd Embodiment, even if a driving | running condition and an environment change, the water temperature difference in the inlet / outlet of the cooling water of the engine 1 can be made to correspond with the said predetermined water temperature difference. In other words, even if the operating condition or environment changes, the temperature difference between the cooling water inlet and outlet of the engine 1 does not occur due to temperature distortion between the head block gasket of the engine 1, and the engine 1 It is possible to achieve an appropriate water temperature difference that does not increase the difference in combustion evaporation and combustion state between the cylinders.

It is a figure showing the schematic structure of the hybrid vehicle concerning each embodiment. It is a figure which shows schematic structure of the cooling system which concerns on each embodiment. It is a graph which shows the relationship between the request torque from a driver | operator, and an engine speed. It is a figure which shows schematic structure of the cooling system which concerns on 1st Embodiment. It is a figure which shows schematic structure of the cooling system which concerns on 2nd Embodiment. It is a figure which shows schematic structure of the cooling system which concerns on 3rd Embodiment.

Explanation of symbols

1 engine (internal combustion engine)
15 Electric water pump (electric WP)
17 Cooling water passage 20 ECU
50 Cooling system 100 Hybrid vehicle

Claims (4)

Control of a hybrid vehicle for controlling a hybrid vehicle comprising an internal combustion engine, an electric motor capable of supplying power to a drive shaft connected to an axle, and an electric water pump for circulating cooling water in the internal combustion engine A device,
Optimal flow rate learning means for learning the optimal flow rate of the cooling water by controlling the electric water pump;
During the period from when the optimal flow rate learning means starts learning the optimal flow rate to when it completes, the output of the internal combustion engine corresponding to the required torque is controlled to be constant, and when the required torque fluctuates, A control apparatus for a hybrid vehicle, comprising: output correction means that compensates for a fluctuation in the output of the internal combustion engine corresponding to a fluctuation in the required torque by controlling the rotational speed.   The optimal flow rate learning means controls the electric water pump to increase the flow rate of the cooling water when knocking occurs in the internal combustion engine, thereby suppressing the knocking, thereby improving fuel efficiency. In such a case, the flow rate of the cooling water when the knocking is suppressed is set to the optimum flow rate.   The optimum flow rate learning means adjusts the flow rate of the cooling water by controlling the electric water pump so that the coolant temperature becomes a predetermined water temperature, and the adjusted flow rate of the coolant is used as the optimum flow rate. The hybrid vehicle control device according to claim 1, wherein the control device is a hybrid vehicle control device.   The optimum flow rate learning means adjusts the flow rate of the cooling water by controlling the electric water pump so that the water temperature difference at the inlet / outlet of the cooling water of the internal combustion engine becomes a predetermined water temperature difference. The control apparatus for a hybrid vehicle according to any one of claims 1 to 3, wherein a flow rate of cooling water is set to the optimum flow rate.

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