Vehicle driving device

Abstract

To provide a highly practical vehicle driving device.SOLUTION: In a vehicle driving device having an engine 10, a turbocharger 12, a waste gate valve 14, a water cooling type cooling device 16 and a controller 18, a high water temperature mode of maintaining a temperature of cooling water at a relatively high temperature and a low water temperature mode of maintaining the temperature at a relatively low temperature are switched selectively, and a normal open mode of opening the waste gate valve in a normal region and a normal close mode of closing the waste gate valve in the normal region are switched corresponding to the switching between the high water temperature mode and the low water temperature mode. Appropriate switching of the modes enables preferable fuel economy, reliability and supercharging response.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle drive system equipped with an engine. [Background technology]

[0002] A vehicle drive system equipped with an engine may be equipped with, for example, a turbocharger, and it is common for a wastegate valve to be installed in addition to the turbocharger. The following patent documents describe techniques for opening and closing the wastegate valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2009-228486 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology described in the above patent document employs a mode in which the wastegate valve is open in a normal range in order to reduce exhaust gas emissions. The wastegate valve can be closed when the turbocharger is to be used and open when it is not to be used. As a result of consideration, the inventors of the present application have obtained new knowledge regarding the opening and closing of the wastegate valve that can improve the practicality of the vehicle drive system. The present invention is based on this knowledge and aims to provide a highly practical vehicle drive system. [Means for solving the problem]

[0005] In order to solve the above problems, the vehicle drive device of the present invention comprises: A vehicle drive system including an engine, a turbocharger, a wastegate valve provided in a bypass passage for diverting exhaust gas from the engine away from the turbocharger when the wastegate valve is open, a cooling device for cooling the engine with cooling water, and a controller for controlling the opening and closing of the wastegate valve and the temperature of the cooling water in the cooling device, The controller: The system is configured to selectively switch between a high water temperature mode, which keeps the coolant temperature relatively high, and a low water temperature mode, which keeps the coolant temperature relatively low, and to switch between a normally open mode, which keeps the wastegate valve open in the normal range, and a normally closed mode, which keeps the wastegate valve closed in the normal range, in response to switching between the high water temperature mode and the low water temperature mode. [Effects of the Invention]

[0006] In this vehicle drive system, when the turbo is activated in the normal range, the wastegate valve is closed, and when the turbo is not activated, the wastegate valve is open. On the other hand, the "high temperature water mode" related to the temperature of the coolant in the cooling device can be considered a mode in which fuel economy is prioritized over engine power, and the "low temperature water mode" can be considered a mode in which engine power is prioritized over fuel economy. In other words, according to the present invention, the turbocharger is enabled / disabled in synchronization with the change in coolant temperature, thereby enabling appropriate control of a vehicle drive system equipped with a turbocharger. Specifically, an optimal balance of fuel economy, reliability, and supercharging response is achieved. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle drive device according to an embodiment; [Figure 2] 10 is a graph for explaining a normally closed mode regarding a wastegate valve. [Figure 3] 10 is a flowchart of a mode switching program executed in the controller. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a vehicle drive device according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition to the embodiment described below, the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Example]

[0009] [A] Vehicle drive system configuration As shown schematically in FIG. 1, the vehicle drive system of the embodiment includes an engine 10, a turbocharger 12, a wastegate valve 14, a cooling device 16 for cooling the engine 10 with cooling water, and a drive electronic control unit (hereinafter sometimes referred to as a "drive ECU") 18 which is a controller for controlling the opening and closing of the wastegate valve 14 and the temperature of the cooling water in the cooling device 16.

[0010] The turbocharger 12 has a typical structure and includes a compressor wheel 20 and a turbine wheel 22. The compressor wheel 20 and turbine wheel 22 are connected by a shaft 24 and rotate integrally. The compressor wheel 20 is disposed in a compressor housing 28 that constitutes part of an intake passage 26, and the turbine wheel 22 is disposed in a turbine housing 32 that constitutes part of an exhaust passage 30. An intercooler 34 and a throttle valve 36 are provided in the intake passage 26 downstream of the compressor housing 28, and an exhaust gas purification catalyst 38 is provided in the exhaust passage 30 downstream of the turbine housing 32. In FIG. 1, the flow of intake air and exhaust gas is indicated by solid arrows.

[0011] A bypass passage 40 is provided in the exhaust passage 30 to divert exhaust gas away from the turbocharger 12. A wastegate valve 14 is provided in this bypass passage 40. The wastegate valve 14 is a typical electromagnetic on-off valve that functions to allow exhaust gas to pass through the turbocharger 12 when in a closed state and to allow exhaust gas to bypass the turbocharger 12 when in an open state.

[0012] When the wastegate valve 14 is closed, the exhaust gas rotates the turbine wheel 22, which also rotates the compressor wheel 20, thereby supercharging the intake air in the intake passage 26. In other words, the function of the turbocharger 12 is enabled, in other words, the effect of the turbocharger 12 is exerted (a so-called "turbo-effective" state). On the other hand, when the wastegate valve 14 is open, the exhaust gas passes through the bypass passage 40, which prevents the turbine wheel 22 from rotating, and prevents the compressor wheel 20 from rotating either. In other words, the function of the turbocharger 12 is disabled, in other words, the effect of the turbocharger 12 is not exerted (a so-called "turbo-ineffective" state).

[0013] The cooling system 16 includes a coolant circuit 50, which includes an internal passage formed inside the engine 10 as a water jacket and an external passage formed outside the engine 10, a water pump 52, a radiator 54, and a coolant flow control valve 56. The coolant circuit 50 has two circulation paths, as indicated by the dashed arrows in FIG. 1 . One of the circulation paths is a radiator circulation path that circulates the coolant discharged from the water pump 52 through the engine 10, the radiator 54, the coolant flow control valve 56, and the water pump 52 in this order. The other is a bypass circulation path that circulates the coolant discharged from the water pump 52 through the engine 10, a bypass passage 58, the coolant flow control valve 56, and the water pump 52 in this order. While the water pump 52 may be electrically driven, the vehicle drive system of this embodiment employs a water pump driven by the rotation of the crankshaft 60 of the engine 10 as an engine accessory.

[0014] Although a detailed description of the structure of the coolant flow control valve 56 will be omitted, it is possible to employ, for example, a coolant flow control valve such as that described in Japanese Patent Application Laid-Open No. 2006-29113. The coolant flow control valve 56 has a controllable actuator, and has the function of changing the ratio between the flow rate of coolant flowing through the radiator circulation path and the flow rate of coolant flowing through the bypass circulation path by operating the actuator. The operation of the actuator is controlled to control the ratio in order to maintain the temperature of the engine 10 (specifically, for example, the temperature of the coolant discharged from the engine 10) at a target temperature. Simply put, the coolant flow control valve 56 is controlled so that the flow rate of coolant flowing through the radiator circulation path is increased when it is desired to maintain a relatively low temperature of the engine 10, and conversely, the flow rate of coolant flowing through the bypass circulation path is increased when it is desired to maintain a relatively high temperature of the engine 10.

[0015] The drive ECU 18, which serves as a controller, is primarily a computer, and in addition to controlling the engine 10 by controlling the throttle valve 36, it also controls the wastegate valve 14 and the coolant flow control valve 56 in order to enable / disable the function of the turbocharger 12 and control the temperature of the coolant in the cooling device 16. For this reason, the drive ECU 18 also has drive circuits (drivers) for the throttle valve 36, wastegate valve 14, and coolant flow control valve 56.

[0016] For the above-mentioned control, the vehicle drive system is provided with an accelerator position sensor 72 that detects an accelerator position β, which is the amount of operation of an accelerator pedal 70 serving as an accelerator operating member, a throttle position sensor 74 that detects a throttle position α, which is the opening of the throttle valve 36, a shaft rotation angle sensor 76 that detects a shaft rotation angle δ, which is the rotation angle (rotation phase) of the crankshaft 60, and a coolant outlet temperature sensor 78 that detects a coolant outlet temperature T, which is the temperature of the coolant at the outlet from the engine 10. Detection signals from these sensors 72, 74, 76, 78 are sent to the drive ECU 18.

[0017] [B] Vehicle drive control The controls performed by the drive ECU 18, specifically the basic engine control, the coolant temperature control, the wastegate valve opening / closing control, etc. will be described below.

[0018] i) Basic engine control The engine basic control is a common control, and a known control method can be used. Briefly, the drive ECU 18 determines the throttle opening α based on the accelerator opening β and other parameters, and controls the throttle valve 36 to achieve the throttle opening α. The engine basic control also controls the ignition timing of the engine 10, i.e., the so-called retard amount θ. The retard amount θ is defined as a retard from the MBT (Minimum Advanced for Best Torque), which is the ignition timing at which torque is maximized. The retard amount θ can be determined using a common method. Briefly, the drive ECU 18 determines the retard amount θ based on the engine speed NE, which is the engine speed determined based on the shaft rotation angle δ, and the intake load factor (engine load factor) KL. The intake load factor KL is a parameter that generally indicates the load on the engine 10 and is determined based on the engine speed NE and the throttle opening α.

[0019] ii) Cooling water temperature control Cooling water temperature control sets the cooling water outlet temperature T to the target temperature T. * The drive ECU 18 controls the coolant outlet temperature T to be equal to the target temperature T * The operation of the cooling water flow control valve 56 is controlled so as to satisfy the following.

[0020] If the coolant temperature is lowered, it is possible to advance the ignition timing while preventing knocking, that is, to reduce the retard amount θ (advance the timing). Therefore, when the load on the engine 10 is large, the coolant temperature is lowered. On the other hand, if the coolant temperature is raised, fuel economy improves. In view of these points, in the present vehicle drive system, the coolant outlet temperature T is set to a high target temperature T H * (e.g., 97°C) and a low target temperature T L * A low water temperature mode in which the engine coolant temperature is maintained at a low temperature (for example, 82°C) is set, and the drive ECU 18 switches between these modes.

[0021] The high water temperature mode and the low water temperature mode are switched as follows: In this vehicle drive system, the amount of retardation θ is used as an index of the load on the engine 10. - This retardation amount θ - For example, the retard amount θ is smoothed with a time constant of 30 seconds, in other words, it can be considered that the high frequency components in the fluctuation of the retard amount θ are omitted (it can also be considered as an average over 30 seconds). - Specifically, when it is estimated that the load on the engine 10 is relatively low, the drive ECU 18 determines the amount of retardation θ - is the threshold θ TH or when the intake load rate KL is in a relatively small range (for example, 20 to 60%) and the engine speed NE is equal to or lower than the threshold speed NE TH When the engine speed is below 1,000 rpm (for example, 1,000 rpm) for a set time t1 (for example, 10 seconds) or more, the basic conditions for transition to the high water temperature mode are determined to be satisfied, and the engine is transitioned to the high water temperature mode. On the other hand, when the load on the engine 10 is estimated to be relatively high, the drive ECU 18 adjusts the amount of smoothing retardation θ - is the threshold θ TH In the above cases, the basic conditions for transitioning to the low water temperature mode are deemed to be met, and the system transitions to the low water temperature mode. The transition based on these basic conditions is made on the premise that the previous mode has continued for a set transition allowable time t0 (e.g., 30 seconds) or longer. However, even if the previous mode has not continued for the set transition allowable time t0 or longer, the drive ECU 18 transitions from the high water temperature mode to the low water temperature mode on the assumption that special conditions have been met if the vehicle is in a rapid acceleration state, specifically, if the retard amount θ is equal to or greater than the set value θ0 for a set time t2 (e.g., 4 seconds) or longer, or if the WOT state (a state in which the accelerator pedal is fully open) has continued for a set time t3 (e.g., 0.5 seconds) or longer.

[0022] iii) Wastegate valve opening / closing control The wastegate valve opening / closing control is a control for opening and closing the wastegate valve 14, and the drive ECU 18 controls the operation of the valve 14.

[0023] As explained above, the effect of the turbocharger 12 is exerted by closing the wastegate valve 14. Generally, when the load on the engine 10 increases to a certain extent, the wastegate valve 14 is opened in consideration of the load. Specifically, as shown in FIG. 2 , the wastegate valve 14 is opened in a region where the engine speed NE is relatively high and the intake load rate KL is relatively high. Conversely, when the load on the engine 10 is relatively low, that is, in a normal state (which can also be called the "normal range"), the wastegate valve 14 is closed. This control mode is called a normally closed mode. In this mode, the turbocharger 12 is enabled in the normal state, and the power of the engine 10 is fully exerted.

[0024] On the other hand, disabling the turbocharger 12 reduces the power of the engine 10 but improves fuel economy. Taking this into consideration, the vehicle drive system of the present invention is set to a normally open mode in which the wastegate valve 14 is kept open even in normal conditions.

[0025] In this vehicle drive system, switching between the normally open mode and the normally closed mode is not performed based on a specific condition, but is performed in response to switching between the high water temperature mode and the low water temperature mode, i.e., triggered by this switching. Specifically, when the high water temperature mode is selected, the normally open mode is selected, and when the low water temperature mode is selected, the normally closed mode is selected. Furthermore, the switching between the two modes is synchronized. Therefore, in this vehicle drive system, switching between the normally open mode and the normally closed mode is performed appropriately without any special processing, making it possible to achieve both fuel efficiency, reliability, and supercharging response.

[0026] iv) Mode switching flow Switching between high water temperature mode and low water temperature mode, and between normally open mode and normally closed mode is performed by the drive ECU 18 repeatedly executing a mode switching program shown in the flowchart of Figure 3 at short intervals (for example, several to several tens of microseconds). Below, the flow of processing according to this program will be briefly explained with reference to the flowchart.

[0027] In the process according to the mode switching program, first, in step 1 (hereinafter abbreviated as "S1", the same applies to the other steps), the current smoothed retard amount θ - In the next step S2, it is determined whether the state in which the retard amount θ is equal to or greater than the set value θ0 continues for a set time t2 or more. If this state has not continued, it is determined in the next step S3 whether the WOT state has continued for a set time t3 or more. If it is determined in step S2 that the above state has continued for the set time t2 or more, or if it is determined in step S3 that the WOT state is continuing, the process proceeds to step S9, where the low water temperature mode is selected, and then in step S10 the normally closed mode is selected.

[0028] If it is determined in S3 that the WOT state is not continuing, then in S4 it is determined whether the current mode (whether low water temperature mode or high water temperature mode) has continued for the set transition allowable time t0 or more. If it has not continued for the set transition allowable time t0 or more, no mode transition is performed and one execution of this program ends.

[0029] In S4, the current mode is set to the preset transition time t TH If it is determined that the delay time has continued for more than 10 seconds, the current amount of retardation θ - is the threshold θ TH It is determined whether the smoothed retard amount θ is smaller than - is the threshold θ TH If it is determined that the intake load factor KL is in a relatively small range and the engine speed NE is equal to or greater than the threshold speed NE THIt is determined whether or not the state in which the value is equal to or less than the set time t1 continues.

[0030] In S5, the amount of retardation θ - is the threshold θ TH If it is determined that the difference is smaller than t1 or if it is determined in S6 that the above-mentioned state has continued for the set time t1 or more, the system goes to high water temperature mode in S7 and to normally open mode in S8. On the other hand, if it is determined in S6 that the above-mentioned state has not continued for the set time t1 or more, the system goes to low water temperature mode in S9 and to normally closed mode in S10. [Explanation of symbols]

[0031] 10: Engine 12: Turbocharger 14: Wastegate valve 16: Cooling system 18: Drive electronic control unit (drive ECU) [controller] 26: Intake passage 30: Exhaust passage 36: Throttle valve 40: Bypass passage 50: Cooling water circuit 52: Water pump 54: Radiator 56: Cooling water flow control valve 58: Bypass passage

Claims

[Claim 1] A vehicle drive system including an engine, a turbocharger, a wastegate valve provided in a bypass passage for diverting exhaust gas from the engine away from the turbocharger when the wastegate valve is open, a cooling device for cooling the engine with cooling water, and a controller for controlling the opening and closing of the wastegate valve and the temperature of the cooling water in the cooling device, The controller: A vehicle drive device configured to selectively switch between a high water temperature mode in which the temperature of the cooling water is kept relatively high and a low water temperature mode in which the temperature is kept relatively low, and to switch between a normally open mode in which the wastegate valve is opened in a normal range and a normally closed mode in which the wastegate valve is closed in a normal range, in response to switching between the high water temperature mode and the low water temperature mode.

Images