Control system for hybrid vehicles

Abstract

By applying different control mechanisms depending on the amount of water mixed in the oil, the system reduces the impact of water in the oil while suppressing the deterioration of fuel efficiency. [Solution] The controller for controlling the operation of the internal combustion engine in EV driving conditions includes a dilution determination unit (step S1) that determines the amount of water in the lubricating oil, a stirring control unit (step S6) that performs stirring control to rotate the internal combustion engine with the throttle valve open and without supplying fuel when the dilution determination unit determines that the amount of water is greater than or equal to a first threshold, and a dilution reduction control unit (step S5) that performs dilution reduction control to remove water from the lubricating oil when the dilution determination unit determines that the amount of water is greater than or equal to a second threshold, which is greater than the first threshold.

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle having an internal combustion engine and an electric motor as driving power sources, and particularly to a device for controlling the case where moisture is mixed into the lubricating oil of the internal combustion engine.

Background Art

[0002] In an internal combustion engine such as a reciprocating engine (hereinafter referred to as an engine), there are many portions that are in frictional contact at high speeds, and thus it is lubricated with oil. On the other hand, fuel and combustion exhaust gases inevitably contain moisture. The moisture condenses due to a decrease in temperature or the like, and this may be mixed into the oil. When the amount of moisture in the oil increases, there are inconveniences such as hindering lubrication or causing clogging of the strainer when it freezes. Further, when the oil is used as the control hydraulic pressure of a hydraulic device, there is also a possibility that a pressure drop occurs due to an increase in the amount of moisture.

[0003] A technique for reducing the moisture in the oil that causes the above inconveniences and reducing the dilution degree of the oil by moisture has been proposed by Patent Document 1. The control device described in Patent Document 1 is a control device for a hybrid vehicle equipped with an electric motor (hereinafter simply referred to as a motor) as a driving power source in addition to an engine, and is configured to evaporate the moisture in the oil and reduce the dilution degree by raising the temperature of the oil by rotating the engine. More specifically, when the amount of moisture in the oil increases, the engine is operated at a high rotational speed and a low load, thereby raising the temperature of the engine due to fuel combustion, frictional loss, etc. Along with that, the temperature of the oil is raised to evaporate the moisture. Further, the motor is made to function as a generator to perform energy regeneration, thereby suppressing deterioration of fuel consumption.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] The control device described in Patent Document 1 determines the dilution of the oil by water based on factors such as the engine's operating time when cold and the oil pressure. If the determination is successful, the engine is uniformly operated at high speed and low load. Therefore, if the dilution level exceeds the threshold for determination, the oil is heated, and the mixed water can be evaporated, thus avoiding or suppressing the effects of water contamination in the oil. However, considering the case where the oil remains diluted with water for a long period, the engine will be operated even when the dilution level is low. In other words, in the device described in Patent Document 1, even when the dilution level is low and the effects of water contamination are minimal, the engine will be operated and fuel will be consumed in the same way as when the dilution level is high. Thus, in the device described in Patent Document 1, the engine is uniformly operated when the dilution determination is successful, so even if energy regeneration is performed by the motor, the amount of fuel consumed by the engine will increase, which may worsen fuel efficiency.

[0006] This invention has been made in view of the above-mentioned technical problems, and aims to provide a control device for a hybrid vehicle that can reduce the effects of water in the oil while suppressing deterioration of fuel efficiency by performing different control depending on the amount of water mixed in the oil. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a control device for a hybrid vehicle equipped with an internal combustion engine having a throttle valve and lubricated by lubricating oil, and an electric motor as a driving force source for driving, and capable of rotating the internal combustion engine in an EV driving state where the vehicle is driven by the output of the electric motor, wherein the device comprises a controller for controlling the operating state of the internal combustion engine in the EV driving state, the controller comprising: a dilution determination unit for determining the amount of water in the lubricating oil; a stirring control unit that performs stirring control to rotate the internal combustion engine with the throttle valve open and without supplying fuel when the dilution determination unit determines that the amount of water is greater than or equal to a predetermined first threshold and less than a predetermined second threshold greater than the first threshold; and a dilution reduction control unit that performs dilution reduction control to remove the water from the lubricating oil when the dilution determination unit determines that the amount of water is greater than or equal to the second threshold.

[0008] In the present invention, the electric motor may be configured to rotate the internal combustion engine without supplying fuel and with the throttle valve open.

[0009] The present invention may further include another motor that rotates the internal combustion engine without supplying fuel and with the throttle valve open.

[0010] In the present invention, the dilution reduction control may include control for evaporating the water from the lubricating oil.

[0011] In the present invention, the dilution reduction control may be either a control that raises the temperature of the lubricating oil to evaporate the moisture, or a control that lowers the pressure of the lubricating oil atmosphere to evaporate the moisture. [Effects of the Invention]

[0012] According to the present invention, if the amount of water in the lubricating oil is above a first threshold, the internal combustion engine rotates without burning fuel and with reduced intake resistance, agitating the lubricating oil. As a result, the water in the lubricating oil is emulsified and diffused almost uniformly, reducing the effects of a drop in oil pressure. Furthermore, the internal combustion engine not only does not consume fuel, but the throttle valve is open and intake resistance is reduced, thus reducing energy consumption and suppressing the deterioration of the vehicle's overall fuel efficiency. Moreover, if the amount of water exceeds a second threshold, the water is removed from the lubricating oil, thus preventing or suppressing problems such as poor lubrication and water freezing. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram illustrating the configuration of the power source for a hybrid vehicle in one embodiment of the present invention. [Figure 2] This is a block diagram showing the functional configuration of the controller. [Figure 3] This is a flowchart illustrating an example of the control implemented in one embodiment of the present invention. [Modes for carrying out the invention]

[0014] Next, embodiments of the present invention will be described with reference to the attached drawings. Note that the embodiments described below are merely examples of how the present invention can be implemented and do not limit the invention.

[0015] The control device in the embodiment of the present invention is a control device for a hybrid vehicle equipped with an internal combustion engine (hereinafter referred to as "engine") and an electric motor or motor-generator (hereinafter referred to as "motor") as a driving force source for driving. The hybrid vehicle may be a hybrid vehicle equipped with an appropriate hybrid type such as a series hybrid, parallel hybrid, or series-parallel hybrid. Figure 1 schematically shows the drive system of a two-motor hybrid vehicle 1. The driving force source 2 shown here is equipped with an engine 3 and two motors 4 and 5, and is configured to divide the power output by the engine 3 with a power split mechanism 6, output a part to an output member 7, and convert the other power into electricity, then convert it back into mechanical power and transmit it to the output member 7.

[0016] Engine 3 is a conventionally known power engine that burns fuel, such as a gasoline engine, to produce mechanical power, and is equipped with a throttle valve 9 that adjusts the amount of air taken in via an air filter 8. Engine 3 is also equipped with an oil pump 10 that circulates and supplies lubricating oil to friction sliding parts.

[0017] In the example shown in Figure 1, the power split mechanism 6 is composed of a single-pinion type planetary gear mechanism and includes a sun gear S, a ring gear R arranged concentrically with respect to the sun gear S, and a carrier C that holds the pinion P, which meshes with the sun gear S and the ring gear R, so that it can rotate and revolve. The engine 3 is connected to the carrier C, and the carrier C is the input element. The first motor 4 is connected to the sun gear S, and the sun gear S is the reaction element. The output member is connected to the ring gear R, and the ring gear R is the output element. The second motor 5 is connected to this output element or output member 7. The first motor 4 controls the rotational speed of the engine 3 by functioning as a generator. The electricity generated in this case is supplied to the second motor 5 via the energy storage device 11, and torque is output from the second motor 5 to the output member 7.

[0018] Therefore, the hybrid vehicle 1 is powered by the torque output by the second motor 5, supplied with power from the energy storage device 11, and the engine 3 can be kept running in this mode. In other words, it is possible to drive in EV mode. In the configuration shown in Figure 1, in order to stop the rotation of the engine 3 in EV mode, the rotation speed of the first motor 4 must be controlled. Alternatively, for example, by providing a clutch between the ring gear R and the output member 7, and a brake that selectively stops the rotation of the ring gear R, the rotation of the engine 3 can be stopped without any special rotation speed control by releasing the clutch during EV driving. Furthermore, by stopping the rotation of the ring gear R with the brake, the engine 3 can be rotated appropriately by the first motor 4. In other words, it is possible to motorize the engine 3.

[0019] In engine 3, water is released from the fuel or generated by the combustion of the fuel. Some of this water may mix with the lubricating oil, diluting it. A controller 12 is provided to reduce the effects of water mixing with the lubricating oil or to reduce the dilution of the lubricating oil by water. The controller 12 is mainly composed of a microcomputer consisting of computing elements (CPU), memory elements (RAM, ROM), and interfaces. It is configured to perform calculations according to a pre-prepared program using input data and pre-stored data, and to output the result of these calculations as a command signal to control the rotational speed of engine 3 or a command signal to control the operation of engine 3.

[0020] The data input to the controller 12 is, for example, the temperature of the cooling water (water temperature) of the engine 3, the pressure of the lubricating oil (oil pressure) supplied to the friction sliding parts of the engine 3, the oil level in the oil pan of the engine 3, the operating time of the engine 3, and the like. Further, the pre-stored data is, for example, the first threshold value, the second threshold value, etc. for determining the moisture content in the lubricating oil. And the controller 12 determines the dilution of the lubricating oil by the moisture based on these data, and controls the operating state of the engine 3, such as rotating the engine 3 or operating the engine 3, based on the result of the determination. The configuration of the controller 12 for performing such control is shown in FIG. 2 as a block diagram.

[0021] FIG. 2 shows the functional configuration of the controller 12, and the controller 12 includes a dilution determination unit 12a. The dilution determination unit 12a measures or estimates the moisture content in the lubricating oil to determine the degree of dilution. The determination can be performed by, for example, the same means as the dilution determination means for dilution determination described in Patent Document 1 mentioned above. That is, the degree of dilution is determined based on the operating time of the engine 3 in the cold state, the pressure of the lubricating oil, or the oil level in the oil pan. The first threshold value and the second threshold value are prepared in advance according to these measured or estimated data, and the determination of dilution is established when the measured or estimated data becomes equal to or greater than the first threshold value and also becomes equal to or greater than the second threshold value.

[0022] As controls executed by the controller 12, two types of controls are prepared. The first control executed when the moisture content is equal to or greater than the first threshold value and less than the second threshold value, and the second control executed when the moisture content is equal to or greater than the second threshold value. As a control unit for instructing the execution of these controls, the controller 12 includes a stirring control unit 12b and a dilution reduction control unit 12c.

[0023] The control executed by the stirring control unit 12b is so-called stirring control that promotes the stirring of the lubricating oil to emulsify moisture, and this is performed by so-called idling the engine 3. More specifically, the engine 3 is rotated by the motor 4 or the motor 5 in a state where fuel is not supplied, that is, in a fuel cut state, and with the throttle valve 9 open. In that case, sliding occurs between components at each friction sliding location, so the oil pump 10 pumps up the lubricating oil and supplies it to a predetermined location. As a result, stirring of the lubricating oil occurs, the moisture in the lubricating oil is refined, and is uniformly dispersed.

[0024] The control executed by the dilution reduction control unit 12c is so-called dilution reduction control that evaporates moisture from the lubricating oil to reduce its amount, and thus reduces the degree of dilution of the lubricating oil by moisture. The means for evaporating moisture is essentially any means that increases the vapor pressure of the moisture in the lubricating oil. An example of this is control to increase the temperature. This is, for example, control to raise the temperature of the lubricating oil by supplying fuel to the engine 3 and operating the engine 3, due to heat generation in the engine 3 and heat due to frictional losses in the friction sliding parts that have thermally expanded. Therefore, the operation of the engine 3 in that case may be low-load high-speed operation or high-load low-speed operation. Another example is control to reduce the pressure of the atmosphere of the lubricating oil to relatively increase the vapor pressure of the moisture in the lubricating oil. For example, when the engine 3 is rotated by the motor 4 with the throttle valve 9 closed, the pressure on the intake side of the engine 3 greatly decreases, so the pressure in the oil pan connected by the blow-by gas passage decreases. As a result, the moisture in the lubricating oil becomes easier to evaporate, and the dilution degree of the lubricating oil decreases.

[0025] An example of the control performed by the controller 12 described above will be explained with reference to the flowchart shown in Figure 3. The routine shown in Figure 3 is repeatedly executed at predetermined short intervals while the hybrid vehicle 1 is running. First, in step S1, it is determined whether or not there is a request for EV driving (EV request). The hybrid vehicle 1 is equipped with drive control modes such as EV mode, HV mode, and engine mode. When the remaining charge (SOC) of the energy storage device 11 is sufficiently large or when the required driving force is small, power is supplied from the energy storage device 11 to the second motor 5 and the vehicle is driven by the torque output by the motor 5. This is EV mode. Also, in the case of steady-state driving where the required driving force is somewhat large, the engine 3 is operated and its power is distributed to the output member 7 and the first motor 4, and the engine speed is controlled by the motor, and the vehicle is driven by the torque of the engine 3 and the torque of the second motor 5. This is HV mode. If the required driving force is even larger, the torque output by the engine 3 is transmitted to the output member 7 and the vehicle is driven by the engine 3. This is engine mode. In step S1, it is determined that the request for EV driving is fulfilled because the state of the hybrid vehicle 1, such as the requested driving force, is in a state where it can execute EV driving mode.

[0026] If the result of the judgment in step S1 is "no", the routine shown in Figure 3 is terminated without any particular control. Conversely, if the result of the judgment in step S1 is "yes", the process proceeds to step S2 to determine the amount of water in the lubricating oil. As mentioned above, this amount of water can be determined by measuring or estimating known means such as the operating time of the engine 3 when cold, the oil level in the oil pan, or the oil pressure, as described in Patent Document 1, etc.

[0027] Next, in step S3, it is determined whether the calculated amount of moisture is equal to or greater than the first threshold. The first threshold is the amount of moisture that, even if present in the lubricating oil, will not cause any particular problems if dispersed within the lubricating oil. This threshold can be determined and predetermined through experiments or simulations. If the result of the determination in step S3 is "no," it means that there is no moisture present in the lubricating oil, or that the amount of moisture present is not enough to cause problems. In this case, the routine shown in Figure 3 is terminated without any further control. Conversely, if the result of the determination in step S3 is "yes," the process proceeds to step S4, where it is determined whether the amount of moisture calculated in step S2 is equal to or greater than the second threshold. The second threshold is a threshold value greater than the first threshold, and is a threshold determined and predetermined through experiments or simulations as the amount by which the amount of moisture in the lubricating oil needs to be reduced.

[0028] If the result of the judgment in step S4 is "yes", the process proceeds to step S5 to perform dilution reduction control, and then the routine in Figure 3 is temporarily terminated. As described above, dilution reduction control starts the engine 3 or forces it to rotate with the motor 4 while restricting the intake. This control is similar to the control conventionally performed to reduce the amount of dilution of lubricating oil by water. Therefore, in this case, fuel is consumed, or the amount of fuel consumed increases. Also, when rotation is forced, the power consumption of the energy storage device 11 increases.

[0029] Conversely, if the result of the judgment in step S4 is "no", the process proceeds to step S6, where stirring control is performed, and then the routine in Figure 3 is temporarily terminated. That is, stirring control is performed when the amount of water in the lubricating oil is between the first threshold and the second threshold. As mentioned above, stirring control is a control that rotates the engine 3 with the motor 4 while no fuel is supplied, i.e., in a fuel cut state, and with the throttle valve 9 open. In this case, the opening of the throttle valve 9 is preferably fully open or close to it. As the engine 3 operates, the lubricating oil circulates and flows, so the lubricating oil is actively stirred, and the mixed water is finely divided and emulsified. That is, fine water droplets are dispersed in the lubricating oil, and since the amount is small, it does not particularly affect the fluidity of the lubricating oil or the properties of oil film formation, and the lubricating oil functions as intended. Furthermore, in this case, even if engine 3 performs the strokes of air intake, compression, and exhaust, the throttle valve 9 is open and there is little resistance to intake, so engine 3 enters a state of so-called idle rotation, resulting in less energy consumption and no particular deterioration in fuel efficiency.

[0030] As described above, the control device according to the present invention performs two types of control depending on the amount of water in the lubricating oil. Therefore, in the dilution state where the engine 3 was conventionally operated or the intake resistance was increased to force the engine 3 to rotate, the engine 3 can be allowed to rotate idly as described above, thereby reducing energy consumption and avoiding or suppressing problems such as poor lubrication and pressure drop. In other words, according to the present invention, even when performing control to eliminate the problems caused by water mixing with the lubricating oil, it is possible to suppress deterioration of fuel efficiency.

[0031] Furthermore, as previously stated, the present invention can also be applied to control devices for series hybrid vehicles or parallel hybrid vehicles. Therefore, the motor that causes the engine to idle is not limited to the first motor 4 described above; in short, any motor-generator or motor connected to the engine is acceptable. Also, the dilution reduction control in the present invention is not limited to the control described above, as it is a control that can reduce the degree of dilution by removing water from the lubricating oil. [Explanation of symbols]

[0032] 1. Hybrid vehicle 2. Power source 3 Engines 4.5 Motor 6 Power split mechanism 7 Output component 8. Air Filter 9. Throttle valve 10 Oil pump 11. Energy storage device 12 controllers 12a Dilution determination unit 12b Stirring control unit 12c Dilution Reduction Control Unit C Carrier P pinion R Ring Gear S Sangiya

Claims

1. A control device for a hybrid vehicle equipped with an internal combustion engine having a throttle valve and lubricated by lubricating oil, and an electric motor as the driving force sources for driving, and capable of rotating the internal combustion engine in an EV driving state where the vehicle is driven by the output of the electric motor, The system includes a controller that controls the operating state of the internal combustion engine during the EV driving state, The aforementioned controller, A dilution determination unit for determining the amount of water in the lubricating oil, When the dilution determination unit determines that the amount of water is greater than or equal to a predetermined first threshold and less than a predetermined second threshold greater than the first threshold, the stirring control unit performs stirring control to rotate the internal combustion engine without supplying fuel and with the throttle valve open, When the dilution determination unit determines that the amount of moisture is equal to or greater than the second threshold, the dilution reduction control unit executes a dilution reduction control to remove the moisture from the lubricating oil. It is equipped with A control device for a hybrid vehicle characterized by the following features.

2. A control device for a hybrid vehicle according to claim 1, The electric motor is configured to rotate the internal combustion engine without supplying fuel and with the throttle valve open. A control device for a hybrid vehicle characterized by the following features.

3. A control device for a hybrid vehicle according to claim 1, The system further includes another motor that rotates the internal combustion engine without supplying fuel and with the throttle valve open. A control device for a hybrid vehicle characterized by the following features.

4. A control device for a hybrid vehicle according to any one of claims 1 to 3, The dilution reduction control includes control for evaporating the water from the lubricating oil. A control device for a hybrid vehicle characterized by the following features.

5. A control device for a hybrid vehicle according to any one of claims 1 to 3, The aforementioned dilution reduction control is either a control that increases the temperature of the lubricating oil to evaporate the moisture, or a control that decreases the pressure of the lubricating oil atmosphere to evaporate the moisture. A control device for a hybrid vehicle characterized by the following features.

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