JP2014083898A - Vehicle travel control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle travel control device that can enhance both fuel economy and drivability in a vehicle enabling coasting by disconnecting an engine from a wheel during traveling.SOLUTION: When a transmission oil temperature Toilt is relatively low, friction within an automatic transmission increases, so that a coasting distance becomes short. At this time, by performing neutral coasting, stop and restart of an engine 12 are prevented, so as to prevent deterioration of drivability. In contrast, when the transmission oil temperature Toilt increases, friction within the automatic transmission decreases, so that the coasting distance becomes long. Thus, even when free run coasting is performed, start and stop of the engine 12 do not occur frequently. Therefore, performance of free run coasting can enhance fuel economy while preventing deterioration of the drivability.

Description

  The present invention relates to a vehicle travel control device, and more particularly to control during inertial travel.

  In order to contribute to the improvement of fuel consumption by extending the mileage for engine brake travel that travels by applying engine brake by the driven rotation of the engine while the power transmission path between the engine and wheels is connected, Inertia running is considered in which the engine braking force is reduced rather than engine braking. The device described in Patent Document 1 is an example. For example, by performing inertial traveling in a state where the power transmission path between the engine and the wheels is cut off, the engine brake is eliminated, and the traveling distance is extended to improve fuel efficiency. A contributing control device is described. Further, it is described that the engine is idled or stopped during this inertial running.

Japanese Patent Application Laid-Open No. 2002-227885

  By the way, Patent Document 1 completely considers the relationship between the transmission oil temperature in the transmission, the transmission oil temperature related value that can be estimated, and whether the state of the engine during inertia running is idling or stopped. Not. For example, when the oil temperature in the transmission is low, the friction (friction) during inertia traveling is large, and therefore the distance that can be coasted is shorter than when the oil temperature in the transmission is high. At this time, when the state of the engine is stopped, the engine is restarted at a short distance, so that drivability is deteriorated. Also, for example, when the oil temperature in the transmission is high, drivability is improved if the engine is in idle operation. However, when the oil temperature in the transmission is high, the inertial travel distance becomes long, so that frequent engine start / stop does not occur even if the engine is stopped. Therefore, even if the engine is idling when the oil temperature in the transmission is high, there is almost no merit, and it is rather undesirable from the viewpoint of fuel consumption to consume fuel by idling the engine.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is a vehicle capable of achieving both fuel efficiency and drivability in a vehicle capable of coasting by separating the engine and wheels during traveling. It is in providing a traveling control device.

  To achieve the above object, the gist of the first invention is as follows: (a) an engine, a clutch that intermittently connects a power transmission path between the engine and the wheel, and the rotation of the engine is changed to the wheel. (B) a free-run inertia traveling in which the power transmission path between the engine and the wheels is disconnected during traveling and the engine is stopped to perform inertia traveling; and (c) during traveling. In a travel control device for a vehicle that performs neutral inertia traveling by cutting the power transmission path between the engine and the wheels and allowing the engine to operate independently, and (d) a shift that performs the free-run inertia traveling The lower limit value of the transmission oil temperature or the transmission oil temperature related value at which the transmission oil temperature can be estimated is higher than the lower limit value of the transmission oil temperature or the transmission oil temperature related value at which the neutral inertia traveling is performed.

  When the transmission oil temperature or the transmission oil temperature related value is relatively low, the friction (friction) in the transmission is increased and the inertial travel distance is shortened. By performing neutral inertia running at this time, it is possible to prevent the engine from being stopped and restarted and to prevent the drivability from deteriorating. On the other hand, when the transmission oil temperature or the transmission oil temperature related value is increased, the friction in the transmission is reduced and the inertial travel distance is increased. Therefore, even if free-run inertial travel is performed, engine start / stop does not occur frequently. Therefore, by performing free-run inertia running or neutral inertia running, it is possible to improve fuel efficiency while preventing deterioration of drivability.

  Preferably, the gist of the second aspect of the invention is that in the vehicle travel control device of the first aspect of the invention, when the vehicle speed is high, the shift that performs the free-run coasting is performed as compared with a case where the vehicle speed is low. Lower the lower limit value of the machine oil temperature or the lower limit value of the transmission oil temperature related value. When the vehicle speed is high, the inertial traveling distance becomes long even if the friction during inertial traveling is large. That is, even when free-run coasting is performed, the engine is not frequently started or stopped. Therefore, when the vehicle speed increases, the lower limit value of the transmission oil temperature at which the free-run inertia traveling is performed or the lower limit value of the transmission oil temperature-related value can be lowered, so that the travel region for the free-run inertia driving can be expanded, and the fuel efficiency is further increased. Can be improved.

  Preferably, the gist of the third invention is the lower limit value of the transmission oil temperature for performing the free-run coasting on a downhill road compared to an uphill road in the vehicle travel control device of the first invention. Alternatively, the lower limit value of the transmission oil temperature related value is lowered. On the downhill road, the coasting distance becomes long even if the friction during coasting is large. That is, even when free-run coasting is performed, the engine is not frequently started or stopped. Therefore, when it becomes a downhill road, by lowering the lower limit value of the transmission oil temperature or the lower limit value of the transmission oil temperature related value that performs free-run coasting, it is possible to expand the travel region in which free-run coasting is performed, Fuel consumption can be further improved.

  Preferably, the gist of the fourth invention is that in the vehicle travel control device of the first invention, the transmission oil temperature or the transmission oil temperature-related value is higher than a first predetermined temperature set in advance. When the temperature is low, the neutral coasting is performed, and the transmission oil temperature or the transmission oil temperature related value is equal to or higher than the first predetermined temperature and lower than a second predetermined temperature higher than the first predetermined temperature. The free running inertia traveling is performed, and the neutral inertia traveling is performed when the transmission oil temperature or the transmission oil temperature related value is equal to or higher than the second predetermined temperature. If you continue to run free-run coasting with a high transmission oil temperature or transmission oil temperature related value, the engine water pump and oil pump will stop and the flow of cooling water and oil will stop for a long time. The engine may overheat. Therefore, when the transmission oil temperature or the transmission oil temperature related value is equal to or higher than the second predetermined temperature, the neutral inertia traveling is performed, so that the engine runs independently and the cooling water flows through the engine, thereby preventing overheating. it can.

  Preferably, the gist of the fifth aspect of the invention is the vehicle travel control apparatus of the first aspect of the invention, further comprising an electric water pump that circulates cooling water of the engine while the engine is stopped, When the transmission oil temperature or the transmission oil temperature related value is lower than a preset first predetermined temperature, the neutral coasting is performed, and the transmission oil temperature or the transmission oil temperature related value is equal to or higher than the first predetermined temperature. And when the temperature is lower than a second predetermined temperature higher than the first predetermined temperature, the free-run coasting is performed, and the transmission oil temperature or the transmission oil temperature related value is equal to or higher than the second predetermined temperature. When the electric water pump is driven, the free-run coasting is performed. When the transmission oil temperature is high, the engine water temperature is likely to be high. In this state, if the free-run inertia running is continuously performed, the engine water pump and the oil pump are stopped for a long time, and the flow of the cooling water and the oil is stopped. Therefore, the engine may be overheated. Therefore, when the transmission oil temperature or the transmission oil temperature-related value is equal to or higher than the second predetermined temperature, the cooling water circulates in the engine even when the engine is stopped by driving the electric water pump and performing free-run coasting. Thus, overheating can be prevented.

  Preferably, in the second invention, as the vehicle speed increases, the lower limit value of the transmission oil temperature or the lower limit value of the transmission oil temperature related value at which the free-run coasting is performed is lowered. In this way, the lower limit value of the transmission oil temperature or the lower limit value of the transmission oil temperature related value at which the free-run inertia running is performed according to the vehicle speed is set to an optimum value, and fuel consumption can be further improved. .

  Preferably, in the third aspect of the invention, the lower limit value of the transmission oil temperature or the lower limit value of the transmission oil temperature related value at which free-run coasting is performed is lowered as the slope of the downhill road increases. In this way, the lower limit value of the transmission oil temperature or the lower limit value of the transmission oil temperature related value that performs free-run coasting according to the slope of the downhill road is set to an optimum value, and fuel efficiency is further improved. Can do.

  Here, preferably, the transmission oil temperature related value corresponds to a related value that can indirectly estimate the transmission oil temperature, such as an engine water temperature, an engine oil temperature, a radiator temperature, and a case temperature of the transmission. .

It is the schematic block diagram which showed the principal part of the control system together with the skeleton of the vehicle drive device to which this invention is applied suitably. It is a figure explaining three driving modes performed by the vehicle drive device of FIG. It is a figure explaining the difference of the execution area | region with respect to the transmission oil temperature of the free-run inertia driving | running | working and neutral inertia driving which are performed by the vehicle drive device of FIG. The main part of the control operation of the electronic control device of FIG. 1, that is, the control operation that can improve the fuel consumption and the drivability by selecting the optimum inertia traveling mode when switching from normal traveling to inertia traveling. It is a flowchart. It is a time chart which shows the operation state when it switches to inertial driving | running | working by carrying out OFF operation by which depression of the accelerator pedal is released from normal driving | running | working. It is a figure explaining changing the execution area with respect to the transmission oil temperature of free run inertia running and neutral inertia running performed with the vehicle drive device which is other examples of the present invention according to vehicle speed. It is a figure which shows the setting pattern of the 1st predetermined temperature with respect to the vehicle speed of FIG. 6 as an example. It is a figure explaining changing the execution area with respect to the transmission oil temperature of free run inertia running and neutral inertia running performed by the vehicle drive device which is other examples of the present invention according to road gradient. It is a figure which shows the setting pattern of the 1st predetermined temperature with respect to the road gradient of FIG. 8 as an example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a schematic configuration diagram showing a main part of a control system together with a skeleton diagram of a vehicle drive device 10 to which the present invention is preferably applied. The vehicle drive device 10 includes an engine 12 that is an internal combustion engine such as a gasoline engine or a diesel engine that generates power by combustion of fuel as a driving force source, and the output of the engine 12 is differential from the automatic transmission 16. It is transmitted to the left and right wheels 20 via the gear unit 18. A power transmission device such as a damper device or a torque converter is provided between the engine 12 and the automatic transmission 16, but a motor generator that functions as a driving force source may be provided.

  The engine 12 includes an engine control device 30 having various devices necessary for output control of the engine 12, such as an electronic throttle valve and a fuel injection device. The electronic throttle valve controls the amount of intake air, and the fuel injection device controls the amount of fuel supplied. Basically, the amount of operation of the accelerator pedal (accelerator opening) that is the driver's required output It is controlled according to Acc. The fuel injection device 30 can stop the fuel supply (fuel cut F / C) even when the vehicle is traveling, for example, when the accelerator opening Acc is zero and the accelerator is OFF. The engine 12 includes an electric water pump 34. When the engine is stopped, the electric water pump 34 is driven to circulate cooling water in the engine.

  The automatic transmission 16 is a stepped automatic transmission such as a planetary gear type in which a plurality of gear stages having different gear ratios γ are established depending on the disengagement states of a plurality of hydraulic friction engagement devices (clutch and brake). The shift control is performed by an electromagnetic hydraulic control valve, a switching valve or the like provided in the hydraulic control device 32. The clutch C <b> 1 functions as an input clutch of the automatic transmission 16, and is similarly engaged and released by the hydraulic control device 32. The clutch C1 corresponds to an interrupting device (clutch) that connects and disconnects the power transmission path between the engine 12 and the wheel 20, that is, interrupts the power transmission path. Further, as the automatic transmission 16, a continuously variable transmission such as a belt type may be used instead of the stepped transmission.

  The vehicle drive device 10 configured as described above includes an electronic control device 50. The electronic control unit 50 includes a so-called microcomputer having a CPU, a ROM, a RAM, an input / output interface, and the like, and performs signal processing according to a program stored in advance in the ROM while using a temporary storage function of the RAM. Do. The electronic control unit 50 is supplied with a signal indicating the brake operation force Brk from the brake operation amount sensor 60, supplied with a signal indicating the accelerator opening Acc from the accelerator opening sensor 62, and supplied from the engine speed sensor 64 to the engine 12. A signal representing the rotational speed (engine rotational speed) Ne of the automatic transmission 16 corresponding to the vehicle speed V is supplied from the vehicle speed sensor 65, and a signal representing the rotational speed Nout (output shaft rotational speed Nout) of the automatic transmission 16 is supplied. A signal representing the road slope Φ of the road surface is supplied from the road surface gradient sensor 66, a signal representing the engine water temperature Tw is supplied from the engine water temperature sensor 70, and a signal representing the engine oil temperature Toile is supplied from the engine oil temperature sensor 72. A signal representing the transmission oil temperature Toilt, which is the oil temperature of the hydraulic oil in the automatic transmission 16, is supplied from the machine oil temperature sensor 74. In addition, various types of information necessary for various types of control are supplied.

  The electronic control unit 50 functionally includes a normal traveling means 78, a neutral inertia traveling means 80, a free-run inertia traveling means 82, and a traveling mode switching control means 84. The normal traveling means 78, the neutral inertia traveling means 80, and the free-run inertia traveling means 82 are for executing the traveling modes shown in FIG.

  The normal traveling means 78 travels by transmitting the driving force of the engine 12 to the wheels 20. That is, as shown in the correspondence table of the travel modes in FIG. 2, during normal travel, the engine 12 is driven to rotate by being supplied with fuel, and a power transmission path between the engine 12 and the wheels 20 is established. The intermittent clutch C1 is in an engaged state. Accordingly, the torque of the engine 12 is transmitted to the wheel 20 via the clutch C1 and the like.

  The neutral inertia traveling means 80 performs neutral inertia traveling in a traveling state in which inertial traveling with the accelerator opening Acc being equal to or less than a predetermined value and the vehicle speed V being equal to or greater than a predetermined value can be performed. In the neutral inertia running, as shown in the correspondence table of FIG. 2, the clutch C1 is released to cut off the power transmission path between the engine 12 and the wheels 20, while the engine 12 is supplied with fuel to be in the idling operation state. Run coasting in the idling state. In this case, the engine braking force becomes smaller than that of the conventional engine brake traveling. Specifically, since the engine braking force becomes substantially zero because the clutch C1 is released, the traveling resistance is decreased and traveling by inertial traveling is performed. The distance becomes longer and the fuel consumption can be improved. In addition, the fuel consumption is consumed by operating the engine 12 in the idle operation state, but the inertial travel distance is longer than the engine brake travel, so the frequency of re-acceleration is reduced, and the fuel efficiency is improved as a whole. .

  The free-run inertia traveling means 82 performs the free-run inertia travel in a travel state in which the inertia travel with the accelerator opening Acc being equal to or smaller than the predetermined value and the vehicle speed V being equal to or greater than the predetermined value can be performed. In the free-run inertia running, the clutch C1 is released to cut off the power transmission path between the engine 12 and the wheel 20, and the fuel cut F / C for stopping the fuel supply to the engine 12 is performed to rotate the engine 12. Drive with the vehicle stopped. In this case, the engine braking force becomes smaller than that of the engine braking, and more specifically, the engine braking force becomes substantially 0 because the clutch C1 is released. The mileage becomes longer and the fuel consumption can be improved. In the free-run inertia running, the fuel supply to the engine 12 is stopped. Therefore, the fuel efficiency is further improved as compared with the neutral inertia running in which the engine 12 is idling.

  The travel mode switching control means 84 switches between the two neutral travel modes and the free-run coastal travel mode when a command for executing coastal travel is output from the normal travel. Regarding the transmission oil temperature Toilt, Switching is performed according to the case classification (execution condition) shown in any of (a) to (c) of FIG. In this case, it is sufficient that the division is determined including at least the transmission oil temperature Toilt. If the transmission oil temperature is a value other than the transmission temperature Toilt and the transmission oil temperature Toilt can be estimated, the vehicle travels according to other conditions. Mode switching may be performed. For example, the engine water temperature Tw, the engine oil temperature Toile, the radiator temperature, and the case temperature of the automatic transmission 16 are proportional to the transmission oil temperature Toilt. Therefore, the transmission oil temperature Toilt can be estimated from various specifications related to the transmission oil temperature Toilt, and the driving mode may be switched based on these. The engine water temperature Tw, engine oil temperature Toile, radiator temperature, transmission case temperature, and the like correspond to the transmission oil temperature related values of the present invention.

  FIG. 3 (a) shows that neutral inertia traveling is performed when the transmission oil temperature Toilt is lower than the first predetermined temperature α, and is lower than the second predetermined temperature β that is higher than the first predetermined temperature α and higher than the first predetermined temperature α. In some cases, free-run inertia traveling is performed, and in the case where the temperature is equal to or higher than the second predetermined temperature β, neutral coasting or free-run inertia traveling while driving the electric water pump 34 is indicated. The first predetermined temperature α (for example, 60 ° C.) is a lower limit value of the transmission oil temperature Toilt at which free-run inertia traveling is performed, and is a value that is obtained and stored in advance. For example, the first predetermined temperature α is set to a lower limit value of a temperature range in which the engine does not start and stop frequently even when free-run coasting is performed, that is, drivability does not deteriorate. The second predetermined temperature β (for example, 100 ° C.) is a lower limit value for allowing the free coasting coasting while driving the neutral coasting or the electric water pump 34, and is a value obtained and stored in advance. Specifically, when the engine 12 is suddenly stopped at that temperature, the flow of cooling water and oil in the engine is stopped, and the engine water temperature Tw and the engine oil temperature Toile are locally increased to cause overheating. It is set to a threshold value where a possibility arises.

  FIG. 3B is the same as (a) in that the neutral inertia traveling is performed when the transmission oil temperature Toilt is lower than the first predetermined temperature α, but the neutral inertia traveling is equal to or higher than the first predetermined temperature α and the second predetermined temperature α. The difference is that it is executed even when the temperature is lower than β. Referring to FIG. 3B in detail, the lower limit value of the transmission oil temperature Toilt at which the neutral inertia traveling is performed is lower than the lower limit value α of the transmission oil temperature Toilt at which the free-run inertia traveling is performed. In this case, when the transmission oil temperature Toilt is equal to or higher than the first predetermined temperature α and lower than the second predetermined temperature β, free-run inertia traveling and neutral inertia traveling are executed according to predetermined cases. For example, in neutral inertia traveling, power can be generated by an alternator or the like by rotation of the engine 12, so that free-run inertia traveling is limited according to the necessity of electric energy, such as when the remaining amount of the battery is below a predetermined amount, and the first predetermined temperature α To the neutral inertia running in the region of the second predetermined temperature β.

  Although FIG. 3 (c) is substantially the same as (b) above, a third predetermined temperature γ, which is an upper limit value of the transmission oil temperature Toilt at which neutral inertia running is performed, is separately determined, and the first predetermined temperature α And the second predetermined temperature β. Specifically, the upper limit value γ of the transmission oil temperature Toilt at which the neutral inertia traveling is performed is lower than the upper limit value β of the transmission oil temperature Toilt at which the free-run inertia traveling is performed. In this case as well, in the region from the first predetermined temperature α to the third predetermined temperature γ, the free-run inertia running and the neutral inertia running are executed according to predetermined cases. For example, in neutral inertia traveling, power can be generated by an alternator or the like by rotation of the engine 12, so that free-run inertia traveling is limited according to the necessity of electric energy, such as when the remaining amount of the battery is below a predetermined amount, and the first predetermined temperature α To the neutral inertia running in the region of the third predetermined temperature γ.

  Thus, the lower limit value (lower limit value α) of the transmission oil temperature Toilt that performs free-run inertia traveling is higher than the lower limit value of the transmission oil temperature Toilt that performs neutral inertia traveling. For example, since the oil viscosity is high in the region where the transmission oil temperature Toilt is lower than the first predetermined temperature α, the running resistance (friction) due to the oil viscosity in the automatic transmission 16 increases. Therefore, when coasting is performed, the coasting distance that can be coasted is also shortened. Therefore, when the free-run coasting is performed, the engine 12 is frequently started and stopped, and drivability is deteriorated. Furthermore, the start / stop of the engine 12 is frequently repeated, which affects the life of the starter that starts the engine 12. On the other hand, when the transmission oil temperature Toilt is in the region where the temperature is less than the first predetermined temperature α, the neutral inertia running is performed, so that the engine 12 is idled, and the start and stop of the engine 12 is avoided and the deterioration of the drivability is prevented. The Further, when the transmission oil temperature Toilt is equal to or higher than the first predetermined temperature α, the viscosity of the oil in the transmission becomes low, and the running resistance due to the viscosity of the oil in the automatic transmission becomes low. Therefore, even if the free-run inertia traveling is performed, the inertia traveling distance becomes longer as compared with the case where the temperature is lower than the first predetermined temperature α. That is, even if free-run coasting is performed, the drivability does not deteriorate. Therefore, when the temperature is equal to or higher than the first predetermined temperature α, free-run inertia traveling is performed, thereby improving fuel efficiency while preventing deterioration of drivability.

  Further, if the transmission oil temperature Toilt is high and the engine 12 is stopped in this state, the flow of cooling water and oil in the engine stops and the engine water temperature Tw and the engine oil temperature Toilt rise locally. For example, the engine 12 may be overheated. Therefore, when the transmission oil temperature Toilt is equal to or higher than the second predetermined temperature β, the operation mode is switched to the neutral inertia traveling mode or the traveling mode in which the electric water pump 34 is driven and the free run inertia traveling is performed. When neutral coasting is executed, the engine 12 is driven, so that the cooling water and oil in the engine circulate, and the engine water temperature Tw and the engine oil temperature Toilt rise locally, causing the engine 12 to overheat. Is prevented. Similarly, when the electric water pump 34 is driven and the vehicle runs freely, coasting water is circulated even if the engine 12 is stopped, so that overheating is prevented. When the transmission oil temperature Toilt is equal to or higher than the second predetermined temperature β, either neutral coasting or free-run coasting while driving the electric water pump 34 is executed. For example, the electric water pump 34 If the remaining amount of the battery that supplies power to the battery is equal to or greater than a predetermined value, free-run inertia traveling is performed while driving the electric water pump 34, and if it is less than the predetermined value, neutral inertia traveling is performed. The process is divided into cases as appropriate.

  FIG. 4 illustrates a main part of the control operation of the electronic control unit 50, that is, a control operation that can improve fuel consumption and drivability by selecting an optimal inertia traveling mode when switching from normal traveling to inertia traveling. For example, the flowchart is repeatedly executed with an extremely short cycle time of about several milliseconds to several tens of milliseconds. Note that the flow in FIG. 4 is executed on the assumption that a command to switch to inertial traveling is output, for example, by releasing the depression of the accelerator pedal during traveling in normal traveling.

  First, in step S1 (hereinafter, step is omitted) corresponding to the traveling mode switching control means 84, the transmission oil temperature Toilt when switching from normal traveling to inertial traveling is detected, and the oil temperature Toilt is the first predetermined temperature. It is determined whether or not α is greater than or equal to α. If S1 is negative, it is determined that the transmission oil temperature Toilt is low and the coasting distance is short, and in S2 corresponding to the neutral coasting traveling means 80, neutral coasting (N coasting) is performed. Therefore, frequent start / stop of the engine 12 is prevented. Further, since frequent start / stop of the engine 12 is prevented, the number of starters for starting the engine 12 is reduced, and the life of the starter is extended.

  On the other hand, when S1 is affirmed, in S3 corresponding to the travel mode switching control means 84, it is determined whether or not the detected transmission oil temperature Toilt is further equal to or higher than the second predetermined temperature β. That is, it is determined whether or not there is a possibility of overheating when the free-run coasting is performed. If S3 is negative, it is determined that the vehicle will not overheat even if the free-run inertia traveling is performed, and the free-run inertia traveling is performed in S4 corresponding to the free-run inertia traveling means 82. As a result, the fuel consumption is improved because the fuel supply to the engine 12 is stopped.

  On the other hand, when S3 is affirmed, it is determined that there is a possibility of overheating when the free-run inertia traveling is performed. In S5 corresponding to the neutral inertia traveling device 80 or the free-run inertia traveling device 82, the neutral inertia traveling or Inertia traveling is performed in which the electric water pump 34 is driven and free-run inertial traveling is performed. Accordingly, at least the cooling water in the engine 12 is circulated, so that overheating is prevented.

  FIG. 5 is a time chart showing an operating state when the vehicle is switched to coasting by performing an OFF operation for releasing the depression of the accelerator pedal from normal traveling. In FIG. 5, the horizontal axis indicates time, and the vertical axis indicates, in order from the top, vehicle speed, transmission oil temperature, accelerator operation amount, and inertial running at each oil temperature (oil temperature A to C). Oil temperature A to oil temperature C indicate transmission oil temperature Toilt at time t1 when the accelerator pedal is turned OFF.

  As shown in FIG. 5, coasting is started when the accelerator pedal is turned off at time t1 during traveling in normal traveling. The transmission oil temperature Toilt is detected at the time t1, and the coasting mode is switched according to the oil temperature Toil. For example, when the transmission oil temperature Toilt is the oil temperature A at the time t1, the neutral inertia running is started because it is lower than the first predetermined temperature α. Therefore, when the engine 12 is driven in the idle state, the start and stop of the engine 12 is avoided and the deterioration of the drivability is also prevented.

  Further, when the transmission oil temperature Toilt is the oil temperature B at the time t1, the free-run inertia running is started because it is equal to or higher than the first predetermined temperature α and lower than the second predetermined temperature β. Therefore, the fuel consumption is improved by stopping the fuel supply to the engine 12. Further, since the transmission oil temperature Toil is relatively high, the running resistance of the automatic transmission 16 is reduced, the number of start / stop times of the engine 12 is reduced, and the drivability is prevented from deteriorating.

  Further, when the transmission oil temperature Toilt is the oil temperature C at the time point t1, since the temperature is equal to or higher than the second predetermined temperature β, the traveling for driving the electric water pump 34 while the neutral coasting traveling or the free-run coasting traveling is started. The Accordingly, at least the cooling water is lubricated in the engine, so that the transmission oil temperature Toilt is prevented from rising and the engine 12 is prevented from overheating. When free-run coasting is performed in the state of oil temperature C and the circulation of cooling water and oil in the engine is stopped, the temperature rises locally as shown by the broken line, and the temperature of the upper limit value of overheating May be exceeded.

  As described above, according to the present embodiment, when the transmission oil temperature Toilt is relatively low, the friction (friction) in the automatic transmission is increased and the inertia traveling distance is shortened. By performing the neutral inertia running at this time, it is possible to prevent the engine 12 from being stopped and restarted and to prevent the deterioration of the drivability. On the other hand, when the transmission oil temperature Toilt becomes higher, the friction in the automatic transmission becomes smaller and the inertia traveling distance becomes longer. Therefore, even if free-run inertia traveling is performed, the engine 12 does not frequently start and stop. Therefore, by performing free-run coasting, fuel consumption can be improved while preventing deterioration of drivability.

  Further, according to the present embodiment, when the free-run inertia running is continuously executed with the transmission oil temperature Toilt being high, the water pump and oil pump of the engine 12 are stopped and the flow of cooling water and oil is stopped for a long time. As a result, the engine 12 may overheat. Therefore, when the transmission oil temperature Toilt is equal to or higher than the second predetermined temperature β, the coolant in the engine is circulated by performing neutral coasting or free-run coasting while driving the electric water pump 34. Overheating can be prevented.

  Next, another embodiment of the present invention will be described. In the following description, parts common to those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 6 is a map for categorizing the traveling mode when switching from normal traveling to inertial traveling, which is another embodiment of the present invention, and corresponds to FIG. 3A of the above-described embodiment. Although this embodiment can be applied to the patterns shown in FIGS. 3B and 3C, the basic concept is common to FIGS. 3A to 3C, and FIG. b) and (c) are omitted.

  In the present embodiment, the first predetermined temperature α and the second predetermined temperature β are changed according to the vehicle speed V. As shown in FIG. 6, the first predetermined temperature α is set to a low value when the vehicle speed V increases, and is set to a high value when the vehicle speed V decreases. That is, when the vehicle speed V is high, the first predetermined temperature α, which is the lower limit value of the transmission oil temperature Toilt that performs free-run coasting, is made lower than when the vehicle speed V is low. In other words, when the vehicle speed V is high, the region where the free-run coasting is performed is made wider than when the vehicle speed V is low.

  When the vehicle speed V increases, the inertial travel distance becomes longer than when the vehicle speed V is low. That is, even when free-run coasting is performed, the engine is not frequently started or stopped. Therefore, when the vehicle speed increases, the first predetermined temperature α is lowered, that is, the drivability does not deteriorate even if the region where the free-run coasting is performed is expanded. In addition, since the area in which the free-run inertia is run can be further expanded, fuel efficiency can be further improved. Further, when the vehicle speed V is low, the coasting distance is shortened as compared with the case where the vehicle speed V is high, and when the free-run coasting is performed, the number of start / stops of the engine 12 increases and the drivability deteriorates. Therefore, by increasing the first predetermined temperature α, the region in which the neutral inertia traveling is widened, the increase in the number of start / stops of the engine 12 is also avoided, and the deterioration of the drivability is prevented.

  Further, as shown in FIG. 6, the second predetermined temperature β is changed according to the vehicle speed V. As shown in FIG. 6, the second predetermined temperature β is set to a low value when the vehicle speed V increases, and is set to a high value when the vehicle speed V decreases. That is, when the vehicle speed V is high, the second predetermined temperature β is set to a lower value than when the vehicle speed V is low. When the vehicle speed V is high, the coasting distance is longer than when the vehicle speed V is low. Therefore, when free-run coasting is performed, the cooling water and oil in the engine do not circulate for a long time, and the engine 12 overheats. There is a high possibility that Therefore, when the vehicle speed V increases, the second predetermined temperature β is decreased, so that when the transmission oil temperature Toilt is high, it is easy to switch to neutral inertia traveling or traveling that is free-run inertia while driving the electric water pump 34. Further, overheating of the engine 12 is also prevented.

  FIG. 7 shows a setting pattern of the first predetermined temperature α with respect to the vehicle speed V as an example. In FIG. 7, the horizontal axis indicates the vehicle speed V, and the vertical axis indicates the first predetermined temperature α. For example, as indicated by a solid line, the first predetermined temperature α is set so as to change in a step shape according to the vehicle speed V. Alternatively, as indicated by a broken line, the first predetermined temperature α is set so as to continuously change in a straight line. Moreover, although not shown, it may change on a curve. In any of these patterns, the first predetermined temperature α decreases as the vehicle speed V increases. Therefore, the area where the free-run inertia traveling is executed in proportion to the vehicle speed V is expanded, and the fuel consumption is further improved. In addition, the first predetermined temperature α increases as the vehicle speed V decreases. Therefore, as the number of start / stops of the engine 12 increases more easily in free-run coasting, the number of start / stops of the engine 12 can be prevented from increasing and the drivability is prevented from worsening.

  Further, the same pattern is obtained even if the vertical axis in FIG. 7 is replaced with the second predetermined temperature β. That is, as the vehicle speed V increases, the second predetermined temperature β decreases. Accordingly, the higher the vehicle speed V, that is, the longer the time during which the engine 12 is stopped in free-run inertia traveling, the easier it is to switch to neutral inertia traveling or free-run inertia traveling while driving the electric oil pump 34. Overheating is suitably prevented.

  As described above, the present embodiment can provide the same effects as those of the above-described embodiment. Further, when the vehicle speed V is high, the first predetermined temperature α is lowered as compared with the case where the vehicle speed V is low. As a result, fuel consumption can be further improved while preventing deterioration of drivability.

  Further, the first predetermined temperature α and the second predetermined temperature β can be changed not only according to the vehicle speed V but also according to the road gradient Φ. FIG. 8 is a map that divides the traveling mode when switching from normal traveling to inertial traveling, which is still another embodiment of the present invention, and corresponds to FIG. 3A and FIG. 6 of the above-described embodiment. . Although this embodiment can also be applied to the patterns shown in FIGS. 3B and 3C, the basic concept is common to FIGS. 3A to 3C, and FIG. b) and (c) are omitted.

  In the present embodiment, as shown in FIG. 8, the first predetermined temperature α is changed according to whether the road is an uphill road or a downhill road. As shown in FIG. 8, the first predetermined temperature α is set to a high value when going uphill, and the first predetermined temperature α is set to a low value when going downhill. That is, on the downhill road, the first predetermined temperature α that is the lower limit value of the transmission oil temperature Toilt that performs free-run coasting is set to a lower value than the uphill road. In other words, on the downhill road, the area where the free-run coasting is performed is wider than that on the uphill road.

  On downhill roads, the coasting distance is longer than on uphill roads. In other words, the engine 12 does not frequently start and stop even when the free-run coasting is performed. Therefore, the drivability does not deteriorate even if the first predetermined temperature α is lowered when the downhill road is reached, that is, the free running coasting region is expanded. As a result, the range of free-run inertia traveling is further expanded, so that fuel efficiency can be further improved. In addition, the coasting distance of the uphill road is shorter than that of the downhill road, and if the free-run coasting is performed, the number of start / stops of the engine 12 may increase and the drivability may deteriorate. Therefore, by increasing the first predetermined temperature α, the operating range in which the neutral inertia is run is expanded, and the increase in the number of start / stop times of the engine 12 is also avoided, and the deterioration of the drivability is prevented.

  In addition, as shown in FIG. 8, the second predetermined temperature β is changed depending on whether it is an uphill road or a downhill road. As shown in FIG. 8, the second predetermined value β is set to a high value when going uphill, and set to a low value when going downhill. That is, in the case of a downhill road, the second predetermined value β is set to a lower value than that of the uphill road. When going downhill, the coasting distance is longer than uphill. As a result, when the free-run inertia running is executed, the cooling water and oil in the engine do not circulate for a long time, and the possibility that the engine 12 will overheat increases. Therefore, in the case of a downhill road, the second predetermined value β is lowered to switch to neutral inertia traveling or traveling with free-run inertia while driving the electric oil pump 34 when the transmission oil temperature Toilt is high. It becomes easy and overheating of the engine 12 is also prevented.

  FIG. 9 shows an example of a setting pattern of the first predetermined temperature α with respect to the road gradient Φ. In FIG. 9, the horizontal axis indicates the road gradient Φ, and the vertical axis indicates the first predetermined temperature α. In addition, the position where the road gradient Φ is zero corresponds to a flat road surface, and as the road slope Φ of the downhill road increases from the zero position to the right side, the road slope Φ changes from the zero position to the left side. This indicates that the road slope Φ of the uphill road is increased. For example, as shown by the solid line in FIG. 9, the first predetermined temperature α is set to change in a step shape according to the road gradient Φ. Alternatively, as indicated by a broken line, the first predetermined temperature α is set so as to continuously change in a straight line. Moreover, although not shown, it may change on a curve. As can be seen from these patterns, the first predetermined temperature α decreases as the gradient toward the downhill road increases. As the gradient Φ toward the downhill road increases, the coasting distance increases. Therefore, the first predetermined temperature α is set lower as the gradient toward the downhill road increases, and the number of start / stops of the engine 12 does not increase even if the region where the free-run inertia running is performed is expanded. The fuel consumption is further improved by expanding the region where the running is performed. The first predetermined temperature α increases as the road gradient Φ toward the uphill road increases. When the road gradient Φ toward the uphill road increases, the coasting distance is shortened. Therefore, the number of start and stop of the engine 12 is likely to increase in free-run coasting. Therefore, the first predetermined temperature α is increased as the road gradient Φ toward the uphill road increases, and it is easy to switch to neutral coasting, thereby preventing an increase in the number of start / stop times of the engine 12 and preventing deterioration in drivability. The

  Further, the same pattern is obtained even if the vertical axis in FIG. 9 is replaced with the second predetermined value β. That is, the second predetermined temperature β decreases as the road slope Φ of the downhill road increases. As the road gradient Φ of the downhill road increases, the coasting distance becomes longer. Therefore, in free-run coasting, the engine 12 is stopped for a long time and it is easy to overheat. Therefore, the second predetermined temperature β is lowered as the road surface gradient Φ of the downhill road increases, and it is easy to switch to the neutral inertia traveling or the free running inertia driving while driving the electric oil pump 34. Overheating is suitably prevented.

  As described above, the present embodiment can achieve the same effects as those of the above-described embodiment. Further, on the downhill road, the first predetermined temperature α is lowered as compared with the uphill road, thereby reducing the drivability. The fuel consumption can be further improved while preventing the above.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this invention is applied also in another aspect.

  For example, each of the above-described embodiments can be implemented independently, but these embodiments may be combined appropriately.

  Further, in the above-described embodiment, the flowchart shown in FIG. 4 is executed when switching from normal running to inertia running, but it may be applied even during inertia running. For example, if the free-run coasting is continued, there is a possibility that the transmission oil temperature Toilt rises and exceeds the second predetermined temperature β. Therefore, by executing the above flow even in coasting, when the transmission oil temperature Toilt reaches the second predetermined temperature β, the electric oil pump 34 is driven while performing neutral coasting or free-run coasting from free-run coasting. By switching to inertial running, overheating of the engine 12 is suitably prevented.

  Moreover, in the above-mentioned Example, although it switches from normal driving | running | working to coasting based on transmission oil temperature Toilt, it is not limited to transmission oil temperature Toilt. For example, the engine oil temperature Tw, the engine oil temperature Toile, the radiator temperature, and the case temperature of the automatic transmission 16 may be appropriately applied as long as it is a transmission oil temperature related value that can indirectly estimate the transmission oil temperature Toilt. it can. When the transmission oil temperature related value is applied, the specific values of the first predetermined temperature α and the second predetermined temperature β are also changed (corrected) as appropriate according to the applied related values.

  In the above-described embodiment, the clutch C1 that intermittently connects the power transmission path between the engine 12 and the wheels 20 is the clutch C1 that is provided in the automatic transmission 16 that includes a plurality of clutches and brakes and can be switched to neutral. However, the clutch is not limited to the clutch provided in the automatic transmission 16, and is not particularly limited as long as it is a clutch that interrupts the power transmission path between the engine 12 and the wheels 20. Further, the clutch is not limited to a hydraulic friction engagement device, and various intermittent devices such as an electromagnetic clutch can be used.

  Further, in the above-described embodiment, a stepped automatic transmission such as a planetary gear type in which a plurality of gear stages having different gear ratios γ are established depending on the disengagement state of a plurality of hydraulic friction engagement devices (clutch and brake). Although the machine 16 is applied, the specific structure of the transmission is not particularly limited to that of the embodiment. For example, the invention can be applied to different types of transmissions such as a belt-type continuously variable transmission.

  In the above-described embodiment, the first predetermined temperature α and the second predetermined temperature β are set. However, only the first predetermined temperature α may be set.

  Further, in the above-described embodiment, the engine 12 is idling in neutral coasting, but is not limited to idling as long as it is in a range where independent operation is possible.

  In the above-described embodiment, the electric water pump 34 that is driven when the engine 12 is not driven is provided. However, the electric water pump 34 may be omitted. In this case, when the transmission oil temperature Toilt is equal to or higher than the second predetermined temperature β, the transmission is switched to the neutral inertia running.

  In the above-described embodiment, the order of the flowcharts is an example, and the order may be changed as appropriate within a consistent range. For example, step S1 and step S3 can be performed in reverse.

  The above description is only an embodiment, and the present invention can be implemented in variously modified and improved forms based on the knowledge of those skilled in the art.

12: Engine 16: Automatic transmission (transmission)
20: Wheel 34: Electric water pump 50: Electronic control device (travel control device)
C1: Clutch α: First predetermined temperature β: Second predetermined temperature

Claims (5)

An engine, a clutch that interrupts a power transmission path between the engine and the wheel, and a transmission that shifts the rotation of the engine and transmits it to the wheel,
A free-run inertia traveling that travels inertially by cutting off the power transmission path between the engine and the wheel during traveling and stopping the engine;
Neutral inertial traveling that travels inertially by cutting the power transmission path between the engine and the wheel during traveling and allowing the engine to operate independently,
In a vehicle travel control device that performs
The lower limit value of the transmission fluid temperature for performing the free running inertia or the transmission fluid temperature related value for estimating the transmission fluid temperature is higher than the lower limit value of the transmission fluid temperature for performing the neutral inertia traveling or the transmission fluid temperature related value. A travel control device for a vehicle.   The lower limit value of the transmission oil temperature or the lower limit value of the transmission oil temperature related value at which the free-run coasting is performed is lower when the vehicle speed is higher than when the vehicle speed is low. Vehicle travel control device.   2. The vehicle travel control device according to claim 1, wherein a lower limit value of the transmission oil temperature or a lower limit value of the transmission oil temperature related value at which the free-run coasting is performed is lowered on a downhill road than on an uphill road. . When the transmission oil temperature or the transmission oil temperature related value is lower than a preset first predetermined temperature, the neutral inertia traveling is performed,
When the transmission oil temperature or the transmission oil temperature related value is equal to or higher than the first predetermined temperature and lower than a second predetermined temperature higher than the first predetermined temperature, the free-run inertia traveling is performed,
2. The vehicle travel control device according to claim 1, wherein the neutral inertia traveling is performed when the transmission oil temperature or the transmission oil temperature-related value is equal to or higher than the second predetermined temperature. An electric water pump for circulating cooling water of the engine while the engine is stopped;
When the transmission oil temperature or the transmission oil temperature related value is lower than a preset first predetermined temperature, the neutral inertia traveling is performed,
When the transmission oil temperature or the transmission oil temperature related value is equal to or higher than the first predetermined temperature and lower than a second predetermined temperature higher than the first predetermined temperature, the free-run inertia traveling is performed,
2. The vehicle travel control device according to claim 1, wherein when the transmission oil temperature or the transmission oil temperature related value is equal to or higher than the second predetermined temperature, the free-run inertia traveling is performed while driving the electric water pump. .

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