Control device for a hybrid vehicle

Abstract

A control device of a hybrid vehicle. The present invention aims to suppress deterioration of fuel economy and reduce the influence of water in oil by performing different controls depending on the amount of water mixed into the oil. A control device that controls the operation of an internal combustion engine in an EV running state includes: a dilution determination section that calculates the amount of water in lubricating oil; a stirring control section that performs stirring control that rotates the internal combustion engine in a state in which fuel is not supplied and a throttle valve is open, in the case where the dilution determination section determines that the amount of water is equal to or greater than a first threshold value; and a dilution reduction control section that performs dilution reduction control that removes water from the lubricating oil, in the case where the dilution determination section determines that the amount of water is equal to or greater than a second threshold value that is greater than the first threshold value.

Description

Technical Field

[0001] This invention relates to a control device for a hybrid vehicle equipped with an internal combustion engine and an electric motor as driving power sources, and more particularly to a device for controlling the vehicle when water is mixed into the lubricating oil of the internal combustion engine. Background Technology

[0002] Internal combustion engines (hereinafter referred to as engines), such as piston engines, have multiple parts that come into contact with each other at high speeds, and therefore are lubricated with oil. On the other hand, fuel or combustion exhaust gases inevitably contain moisture. This moisture sometimes condenses due to temperature drops, and this can sometimes mix into the oil. If the amount of water in the oil increases, it can hinder lubrication or cause filter clogging in the event of freezing. Furthermore, when oil is used as the control hydraulic pressure in hydraulic equipment, an increase in the amount of water can also cause a pressure drop.

[0003] Patent Document 1 discloses a technique for reducing the water content in oil, which is a cause of the aforementioned adverse conditions, thereby reducing the oil's dilution caused by water. The control device described in Patent Document 1 is designed for hybrid vehicles that use an electric motor (hereinafter referred to as a motor) as a drive source in addition to an engine. It is configured to reduce dilution by increasing the oil temperature through engine rotation, causing water in the oil to evaporate. More specifically, when the water content in the oil increases, the engine temperature rises due to fuel combustion or friction losses by operating the engine at high speed and low load. This, in turn, increases the oil temperature, causing water to evaporate. Simultaneously, the motor functions as a generator to regenerate energy, suppressing the deterioration of fuel economy.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-168379 Summary of the Invention

[0005] The control device described in Patent Document 1 determines the dilution of oil caused by water based on factors such as engine running time during cold starts or oil pressure. If this determination is met, the engine is always operated at high speed and low load. Therefore, if the dilution exceeds the determined threshold, the oil is heated, causing the mixed water to evaporate, thus avoiding or suppressing the effects of water mixed in the oil. However, if the oil remains diluted with water for an extended period, the engine is operated even when the dilution is low. That is, in the device described in Patent Document 1, even when the dilution is low and the effects of water mixing are minimal, the engine is operated and fuel is consumed in the same way as when the dilution is high. Thus, in the device described in Patent Document 1, the engine is always operated when the dilution determination is met, therefore even with energy regeneration via the motor, the fuel consumption caused by the engine increases, potentially worsening fuel economy.

[0006] This invention addresses the aforementioned technical challenges and aims to provide a control device for hybrid vehicles that, by adjusting the control based on the amount of water mixed into the oil, can suppress the deterioration of fuel economy and reduce the impact of water in the oil.

[0007] To achieve the above objectives, the control device for a hybrid vehicle of the present invention is equipped with an internal combustion engine having a throttle valve and being lubricated by lubricating oil and an electric motor as driving power sources for driving. In an EV driving state where the electric motor is used for driving, the internal combustion engine can be rotated. The device is characterized by comprising: a controller that controls the operating state of the internal combustion engine in the EV driving state; the controller comprising: a dilution determination unit that determines the water content in the lubricating oil; a stirring control unit that, when the dilution determination unit determines that the water content is greater than or equal to a predetermined first threshold and less than a predetermined second threshold greater than the first threshold, performs stirring control to rotate the internal combustion engine while no fuel is supplied and the throttle valve is open; and a dilution reduction control unit that, when the dilution determination unit determines that the water content is greater than or equal to the second threshold, performs dilution reduction control to remove the water from the lubricating oil.

[0008] In this invention, the electric motor can be configured to rotate the internal combustion engine when no fuel is supplied and the throttle valve is open.

[0009] In this invention, there may also be other motors that rotate the internal combustion engine when no fuel is supplied and the throttle valve is open.

[0010] In this invention, the dilution reduction control may include control that causes the moisture to evaporate from the lubricating oil.

[0011] In this invention, the dilution reduction control can be either a control that raises the temperature of the lubricating oil to cause the moisture to evaporate, or a control that lowers the pressure of the atmosphere of the lubricating oil to cause the moisture to evaporate.

[0012] Invention Effects

[0013] According to the present invention, if the water content in the lubricating oil is at or above a first threshold, the internal combustion engine rotates and agitates the lubricating oil while not burning fuel and reducing intake resistance. Therefore, the water in the lubricating oil is emulsified and diffused almost uniformly, reducing the effects of hydraulic pressure drop. Furthermore, the internal combustion engine not only does not consume fuel, but the throttle valve opens, reducing intake resistance, thus reducing energy consumption and suppressing the deterioration of the vehicle's overall fuel economy. Moreover, if the water content is at or above a second threshold, the water is removed from the lubricating oil, thus preventing or suppressing conditions such as poor lubrication or water freezing. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the structure of the driving force source of a hybrid vehicle according to one embodiment of the present invention.

[0015] Figure 2 This is a block diagram representing the functional structure of the controller.

[0016] Figure 3 This is a flowchart illustrating an example of control implemented in one embodiment of the present invention. Detailed Implementation

[0017] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the embodiments described below are merely examples of how the present invention is implemented and do not limit the scope of the invention.

[0018] The control device in the embodiments of the present invention is a control device for a hybrid vehicle that uses an internal combustion engine (hereinafter referred to as an engine) and an electric motor or motor / generator (hereinafter referred to as a motor) as a driving force source for driving. This hybrid vehicle can be a hybrid vehicle having a suitable form of hybrid power, such as series hybrid, parallel hybrid, or series-parallel hybrid. Figure 1 The diagram schematically illustrates the drive system in a two-motor hybrid vehicle 1. The drive source 2 shown here includes an engine 3 and two motors 4 and 5, configured to distribute the power output from the engine 3 via a power distribution mechanism 6, outputting a portion to an output component 7, and temporarily converting the remaining power into electricity, then inverting it into mechanical power and transmitting it to the output component 7.

[0019] The engine 3 is a known power machine that outputs mechanical power by burning fuel such as gasoline, and it is equipped with a throttle valve 9 that adjusts the amount of air drawn in through the air filter 8. Furthermore, the engine 3 is equipped with an oil pump 10 that supplies lubricating oil by circulating it in the friction sliding parts.

[0020] exist Figure 1 In the example shown, the power distribution mechanism 6 is composed of a single-pinion planetary gear mechanism, comprising: a sun gear S; a ring gear R disposed concentrically with the sun gear S; and a planet carrier C, which holds the pinion P meshing with the sun gear S and the ring gear R, enabling it to rotate and revolve. An engine 3 is connected to the planet carrier C, which serves as the input element. A first motor 4 is connected to the sun gear S, which serves as the reaction force element. An output component is connected to the ring gear R, which serves as the output element. A second motor 5 is connected to this output element or output component 7. The first motor 4 controls the rotational speed of the engine 3 by functioning as a generator. In this case, the generated electricity is supplied to the second motor 5 via an energy storage device 11, and torque is output from the second motor 5 to the output component 7.

[0021] Therefore, the hybrid vehicle 1 supplies electricity from the battery storage device 11 to the second motor 5, and drives using the torque output by the second motor 5. In this case, the rotation of the engine 3 can be stopped. That is, EV driving is possible. Furthermore, in order to stop the rotation of the engine 3 in EV driving mode, Figure 1 In the structure shown, the rotational speed of the first motor 4 is controlled. Alternatively, for example, by providing a clutch between the ring gear R and the output component 7, and by providing a brake that selectively stops the rotation of the ring gear R, the rotation of the engine 3 can be stopped without special speed control by releasing the clutch during EV driving. Furthermore, by stopping the rotation of the ring gear R using the brake, the engine 3 can be properly rotated by the first motor 4. That is, the engine 3 can be driven by the motor.

[0022] In engine 3, moisture is released from the fuel or generated through fuel combustion. Some of this moisture sometimes mixes into the lubricating oil, thereby diluting the lubricating oil. A controller 12 is provided to control the effects caused by moisture mixing into the lubricating oil or to reduce the dilution of the lubricating oil caused by moisture. The controller 12 is mainly composed of a microcomputer consisting of an arithmetic unit (CPU), storage units (RAM, ROM), and an interface, and is configured to perform calculations according to a pre-prepared program using input data or pre-stored data, and output the result of the calculation as a command signal to control the speed of engine 3 or a command signal to control the operation of engine 3.

[0023] The data input to the controller 12 includes, for example, the temperature of the coolant in the engine 3 (water temperature), the pressure of the lubricating oil supplied to the friction and sliding parts of the engine 3 (hydraulic pressure), the oil level in the oil pan of the engine 3, and the running time of the engine 3. Furthermore, pre-stored data includes a first threshold or a second threshold for determining the water content in the lubricating oil. Based on this data, the controller 12 determines the dilution of the lubricating oil caused by water, and based on the result of this determination, controls the engine 3's operating state, such as rotating the engine 3 or running the engine 3. The structure of the controller 12 used for this control is illustrated in a block diagram. Figure 2 .

[0024] Figure 2 The functional structure of controller 12 is described, and controller 12 includes a dilution determination unit 12a. The dilution determination unit 12a measures or estimates the water content in the lubricating oil to determine the degree of dilution. This determination can be performed, for example, by a mechanism similar to the dilution determination mechanism described in the aforementioned Patent Document 1. That is, the degree of dilution is determined based on the running time of engine 3 in a cold state, the pressure of lubricating oil, or the oil level in the oil pan, etc. Based on these measured or estimated data, a first threshold and a second threshold are prepared in advance. If the measured or estimated data exceeds the first threshold and also exceeds the second threshold, the dilution determination is established.

[0025] Two types of control are prepared for the control executed by the controller 12. A first control and a second control are provided, wherein the first control is executed when the water content is above a first threshold and below a second threshold, and the second control is executed when the water content is above the second threshold. The controller 12 includes a stirring control unit 12b and a dilution reduction control unit 12c as the control unit that issues instructions to execute these controls.

[0026] The control performed by the stirring control unit 12b is so-called stirring control, which promotes the stirring of lubricating oil and emulsifies the water. This is achieved by idling the engine 3. More specifically, the engine 3 is rotated by the motor 4 or motor 5 when no fuel is supplied, i.e., the fuel is cut off, and the throttle valve 9 is open. In this case, sliding occurs between the parts at the friction sliding points, so the oil pump 10 draws lubricating oil and supplies it to the designated locations. As a result, the lubricating oil is stirred, and the water in the lubricating oil is refined and evenly dispersed.

[0027] The control performed by the dilution reduction control unit 12c is a so-called dilution reduction control that reduces the amount of water in the lubricating oil by causing it to evaporate. The mechanism for evaporating water can simply be a mechanism that increases the vapor pressure of the water in the lubricating oil; one example is temperature control. This is, for example, a control that raises the temperature of the lubricating oil by supplying fuel to the engine 3, causing the engine 3 to run, and by generating heat from the engine 3 and the heat caused by frictional losses from the frictional sliding parts due to thermal expansion. Therefore, the engine 3 can operate at low load and high speed, or at high load and low speed. Another example is a control that lowers the atmospheric pressure of the lubricating oil, thus relatively increasing the vapor pressure of the water in the lubricating oil. For example, if 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 drops significantly, thus lowering the pressure in the oil pan connected through the blow-by passage. As a result, the water in the lubricating oil evaporates easily, and the dilution degree of the lubricating oil decreases.

[0028] refer to Figure 3 The flowchart shown illustrates an example of control performed by the controller 12 described above. Figure 3 The illustrated routine is repeatedly executed for a predetermined period of time while the hybrid vehicle 1 is in operation. First, in step S1, it is determined whether there is an EV driving request (EV request). The hybrid vehicle 1 has drive control modes such as EV mode, HV mode, and engine mode. When the remaining charge (SOC) of the battery storage device 11 is sufficiently high or the required driving force is low, power is supplied from the battery storage device 11 to the second motor 5, and the vehicle is driven using the torque output by the motor 5. This is the EV mode. Furthermore, when stable driving requires a certain level of driving force, the engine 3 is run, and the power is distributed to the output component 7 and the first motor 4. The engine speed is controlled by the motor, and the vehicle is driven using the torque of the engine 3 and the torque of the second motor 5. This is the HV mode. When a further high driving force is required, the torque output by the engine 3 is transmitted to the output component 7, and the vehicle is driven using the engine 3. This is the engine mode. In step S1, the EV driving request is determined to be valid when the state of the hybrid vehicle 1, such as the required driving force, becomes the state of executing the EV driving mode.

[0029] If the result of step S1 is "no", the process will temporarily end without any special control measures. Figure 3 The routine shown. Conversely, if the judgment result in step S1 is "yes", proceed to step S2 to determine the water content in the lubricating oil. As described above, this water content can be determined by measuring or estimating using known mechanisms described in Patent Document 1, such as the engine 3 running time when the engine is cold, the oil level in the oil pan, or the hydraulic pressure.

[0030] Next, in step S3, it is determined whether the calculated water content is above the first threshold. The first threshold is the amount of water that, even if mixed with lubricating oil, will not cause any particular problem as long as it is dispersed in the lubricating oil. This threshold can be determined and preset through experiments or simulations. If the result of step S3 is "no," then no water is mixed with the lubricating oil, or the amount of water mixed in is not enough to cause a problem. Therefore, no special control is required, and the process is temporarily terminated. Figure 3 The routine. Conversely, if the judgment result in step S3 is "yes", proceed to step S4 to determine whether the water content calculated in step S2 is above the second threshold. The second threshold is a threshold value that is larger than the first threshold mentioned above. It is a threshold value that needs to be reduced in terms of the amount of water in the lubricating oil and is determined and preset through experiments or simulations.

[0031] If the judgment result in step S4 is "yes", proceed to step S5 to implement dilution reduction control, and then temporarily end. Figure 3 The routine is as described above. The dilution reduction control is performed by starting the engine 3 or by forcibly rotating the motor 4 while the intake air is throttled. This control is the same as conventional control performed to reduce the dilution of lubricating oil caused by moisture. Therefore, fuel consumption increases in this case. Furthermore, under forced rotation, the power consumption of the energy storage device 11 increases.

[0032] Conversely, if the result of the judgment in step S4 is "no", proceed to step S6, implement stirring control, and then temporarily end. Figure 3 The routine involves implementing stirring control when the water content in the lubricating oil is between a first threshold and a second threshold. As described above, stirring control involves controlling the engine 3 to rotate by the motor 4 while the engine is not supplied with fuel (i.e., fuel is cut off) and the throttle valve 9 is open. In this case, the opening degree of the throttle valve 9 is preferably fully open or nearly fully open. Through the operation of the engine 3, the lubricating oil circulates, thus the lubricating oil is actively stirred, and the mixed water is atomized and emulsified. That is, it becomes a state where fine water droplets are dispersed in the lubricating oil, and its amount is small, so it has no particular effect on the fluidity of the lubricating oil or the characteristics of forming an oil film, and the lubricating oil functions as desired. Furthermore, in this case, even when the engine 3 is performing the intake, compression, and exhaust strokes of air, the throttle valve 9 is open and the resistance to intake air is small, so the engine 3 is in a so-called idling state, with low energy consumption and no significant deterioration in fuel economy.

[0033] As described above, in the control device according to the present invention, two controls are performed based on the amount of water in the lubricating oil. Therefore, in the diluted state where the engine 3 is conventionally operated or forced to rotate by increasing intake resistance, the engine 3 can simply be idled as described above. Thus, energy consumption can be reduced and poor lubrication or pressure drop can be avoided or suppressed. That is, according to the present invention, even when controls are performed to eliminate adverse conditions caused by water mixing into the lubricating oil, the deterioration of fuel economy can be suppressed.

[0034] Furthermore, as described above, the present invention can also be applied to control devices for vehicles of series hybrid or parallel hybrid types. Therefore, the motor that enables the engine to idle is not limited to the first motor 4 described above; the key is any motor / generator or motor connected to the engine. Moreover, the dilution reduction control in the present invention is not limited to any control capable of removing water from the lubricating oil and reducing the degree of dilution.

[0035] Symbol Explanation

[0036] 1-Hybrid vehicle, 2-Drive power source, 3-Engine, 4, 5-Motor, 6-Power distribution mechanism, 7-Output component, 8-Air filter, 9-Throttle valve, 10-Oil pump, 11-Electric storage device, 12-Controller, 12a-Dilution determination unit, 12b-Stirring control unit, 12c-Dilution reduction control unit, C-Planetary carrier, P-Pinary gear, R-Ring gear, S-Sun gear.

Claims

1. A control device for a hybrid vehicle, comprising an internal combustion engine having a throttle valve and lubricated by lubricating oil and an electric motor as driving power sources for driving, wherein the internal combustion engine can be rotated in EV driving mode where the electric motor drives at its output, characterized in that, have: The controller controls the operating state of the internal combustion engine during the EV driving state. The controller has: The dilution determination unit determines the water content in the lubricating oil. A stirring control unit, which, when the dilution determination unit determines that the water content is above a preset first threshold and below a preset second threshold that is greater than the first threshold, performs stirring control to rotate the internal combustion engine while no fuel is supplied and the throttle valve is open; and The dilution reduction control unit performs dilution reduction control to remove water from the lubricating oil when the dilution determination unit determines that the water content is above the second threshold.

2. The control device for a hybrid vehicle according to claim 1, characterized in that, The electric motor is configured to rotate the internal combustion engine when no fuel is supplied and the throttle valve is open.

3. The control device for a hybrid vehicle according to claim 1, characterized in that, It also includes other motors that can rotate the internal combustion engine when no fuel is supplied and the throttle valve is open.

4. The control device for a hybrid vehicle according to any one of claims 1 to 3, characterized in that, The dilution reduction control includes controlling the evaporation of the moisture from the lubricating oil.

5. The control device for a hybrid vehicle according to any one of claims 1 to 3, characterized in that, The dilution reduction control is either a control that causes the moisture to evaporate by increasing the temperature of the lubricating oil, or a control that causes the moisture to evaporate by decreasing the pressure of the atmosphere of the lubricating oil.

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