Vehicle control device

Abstract

To provide a control device for a vehicle that suppresses effects on drivability.SOLUTION: A control device is for a vehicle mounted with an engine. The control device for a vehicle includes: a first restriction section that executes first restriction processing for restricting output torque of the engine to a first upper limit value or smaller when a temperature of the engine is a first threshold value or higher; and a second restriction section that executes second restriction processing for restricting the output torque to equal to or smaller than a second upper limit value that is larger than the first upper limit value when the temperature of the engine is equal to or higher than a second threshold value that is lower than the first threshold value and is lower than the first threshold value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] When the engine temperature becomes high, the output torque of the engine may be limited to a predetermined upper limit value or less in order to protect the engine components (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2005-083215 Summary of the Invention [Problem to be solved by the invention]

[0004] Such a sudden restriction of the engine output torque may affect drivability.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a vehicle control device that minimizes the impact on drivability. [Means for solving the problem]

[0006] The above object can be achieved by a control device for a vehicle equipped with an engine, the control device comprising: a first limiting unit that executes a first limiting process to limit the output torque of the engine to a first upper limit value or less when the temperature of the engine is equal to or higher than a first threshold; and a second limiting unit that executes a second limiting process to limit the output torque to a second upper limit value or less that is higher than the first upper limit value when the temperature of the engine is equal to or higher than a second threshold value that is lower than the first threshold but is less than the first threshold.

[0007] The vehicle may further include a notification control unit that causes a notification unit to notify the fact that the output torque is being limited when the second limiting process is being executed.

[0008] The notification control unit may cause the notification unit to notify that the output torque is being limited when the second limiting process is executed and the torque required for the engine exceeds the second upper limit value.

[0009] The second limiting unit may gradually change the output torque to equal to or less than the second upper limit value when the second limiting process is executed in a state in which the torque required of the engine is greater than the second upper limit value.

[0010] The second limiting unit may gradually change the output torque to the required torque of the engine when the second limiting process, which has been executed while the required torque of the engine is greater than the second upper limit value, is released. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a vehicle control device that suppresses the influence on drivability. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of the engine. [Figure 2] FIG. 2 is a flowchart showing an example of torque limit control executed by the ECU. [Figure 3] FIG. 3 is a timing chart showing an example of the second restriction process. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Vehicle outline] FIG. 1 is a schematic diagram showing the overall configuration of a vehicle 1. The vehicle 1 is equipped with an engine (ENG) 10, a torque converter (T / C) 12, and a stepped automatic transmission (A / T) 14. The engine 10 is a gasoline engine, but may also be a diesel engine. A torque converter 12 is connected to a crankshaft 11 of the engine 10. A turbine shaft 13 of the torque converter 12 is connected to the input side of the automatic transmission 14, and the driving force of the engine 10 is transmitted to the automatic transmission 14. An output shaft 15 of the automatic transmission 14 is connected to a differential gear 16, which serves as a final reduction gear. Left and right axles 17 are connected to the differential gear 16. The driving force transmitted to the output shaft 15 is transmitted to drive wheels 18 via the axles 17.

[0014] The ECU (Electronic Control Unit) 20 is an electronic control unit that performs control processing related to the engine 10. The ECU 20 is mainly composed of a computer including a CPU (Central Processing Unit) and volatile and non-volatile memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 20 executes programs installed in the memory on the CPU to perform various control processing related to the engine 10. Various sensors are connected to the ECU 20, which will be described in detail later. The ECU 20 is an example of a vehicle control device, and functionally realizes a first limiting unit, a second limiting unit, and a notification control unit, which will be described in detail later.

[0015] A crank angle sensor s1, a water temperature sensor s2, an air flow meter s3, and an accelerator position sensor s4 are connected to the ECU 20, and the output values ​​of these sensors are input. The crank angle sensor s1 detects the rotation speed of the engine 10. The water temperature sensor s2 detects the temperature of the coolant that cools the engine 10 as the temperature of the engine 10. The air flow meter s3 detects the amount of intake air into the engine 10. The accelerator position sensor s4 detects the accelerator position, which is the opening of the accelerator pedal.

[0016] The ECU 20 calculates the required torque for the engine 10 based on the engine speed, intake air amount, and accelerator opening of the engine 10 detected by the above sensors. The ECU 20 controls the fuel injection amount, intake air amount, and ignition timing of the engine 10 so that the output torque of the engine 10 becomes the required torque.

[0017] The torque converter 12 includes a pump impeller on the input shaft side, a turbine runner on the output shaft side, and a stator that performs torque amplification, and transmits power between the pump impeller and the turbine runner via fluid. The torque converter 2 is provided with a lock-up clutch that connects the input side and output side of the torque converter 2 in a direct or slip-engaged state.

[0018] The automatic transmission 14 is a stepped transmission that includes a plurality of hydraulic friction engagement elements and a planetary gear device. In the automatic transmission 14, the plurality of friction engagement elements are selectively engaged, thereby enabling the automatic transmission 14 to selectively establish a plurality of forward gears, a reverse gear, or a neutral gear position.

[0019] The display unit 21 is controlled by the ECU 20 and is provided on the instrument panel of the vehicle. The display unit 21 is an example of a notification unit, which will be described in detail later. Note that the notification unit is not limited to the display unit 21 and may be, for example, a speaker of the vehicle's audio system, navigation system, etc.

[0020] [Torque limit control] 2 is a flowchart showing an example of torque limit control executed by the ECU 20. This control is continuously repeated while the ignition is on. The ECU 20 determines whether the temperature of the coolant is equal to or higher than a first threshold value T1 (step S1). The first threshold value T1 is set as the lower limit of the temperature below which the temperature of the engine 10 should be immediately reduced in order to protect the engine 10 components.

[0021] If the result of step S1 is Yes, the ECU 20 executes a first limiting process (step S2). The first limiting process is a process for limiting the output torque of the engine 10 to a first upper limit value P1 or less. Specifically, the first limiting process is a process for reducing the output torque to a first upper limit value P1 or less when the output torque is higher than the first upper limit value P1 at the time the first limiting process is started. Therefore, if the output torque controlled based on the accelerator opening, etc., is already equal to or lower than the first upper limit value P1 at the time the first limiting process is started, the output torque is not limited. Furthermore, if the torque required of the engine 10 based on the accelerator opening becomes higher than the first upper limit value P1 after the start of the first limiting process, the output torque is limited to the first upper limit value P1. The output torque is limited by adjusting the fuel injection amount or the intake air amount. The first upper limit value P1 is an upper limit value of the output torque that can immediately reduce the temperature of the engine 10 when the temperature of the engine 10 is equal to or higher than the first threshold value T1. By executing the first restriction process, the temperature of the engine 10 is reduced, and it is possible to protect the components of the engine 10 from high heat. Step S2 is an example of a process executed by the first restriction unit.

[0022] Next, the ECU 20 determines whether the coolant temperature is lower than the first threshold value T1 (step S3). If the result in step S3 is No, step S2 is repeated. If the result in step S3 is Yes, the ECU 20 cancels the first restriction process (step S4).

[0023] If the answer is No in step S1, it is determined whether the temperature of the coolant of the ECU 20 is equal to or higher than a second threshold value T2 (step S5). The second threshold value T2 is a value lower than the first threshold value T1. The second threshold value T2 is set to a temperature at which it is not necessary to immediately protect the components of the engine 10 from heat, but at which the temperature of the coolant is expected to rise to or higher than the first threshold value T1 if the operation of the engine 10 continues in this state. If the answer is No in step S5, this control ends.

[0024] If the result of step S5 is Yes, the ECU 20 executes a second limiting process (step S6). The second limiting process is a process for limiting the output torque of the engine 10 to a second upper limit value P2 or less. Similar to the first limiting process, the second limiting process is a process for reducing the output torque to a second upper limit value P2 or less if the output torque is higher than the second upper limit value P2 at the time the second limiting process is started. Therefore, if the output torque is already equal to or lower than the second upper limit value P2 at the time the second limiting process is started, the output torque is not limited. If the required torque becomes higher than the second upper limit value P2 after the start of the second limiting process, the output torque is limited to the second upper limit value P2. The second upper limit value P2 is a value greater than the first upper limit value P1. The second upper limit value P2 is set to an upper limit value of the output torque that can ensure the driving performance of the vehicle 1 while the temperature of the engine 10 is decreasing.

[0025] In this way, if step S1 is No and step S5 is Yes, i.e., if the coolant temperature is equal to or higher than the second threshold T2 but lower than the first threshold T1, the second restriction process is executed. In other words, the second restriction process is executed before the coolant temperature rises to or higher than the first threshold T1 at which the first restriction process is executed. This makes it possible to avoid the first restriction process being executed and the output torque of the engine 10 being suddenly restricted to a large extent. This makes it possible to suppress the impact on drivability. Step S6 is an example of a process executed by the second restriction unit.

[0026] Next, the ECU 20 determines whether the torque required for the engine 10 is equal to or greater than the second upper limit value P2 (step S7). If the result in step S7 is Yes, the ECU 20 causes the display unit 21 to display a message that the output torque is being limited (step S8). This prevents the driver from feeling uncomfortable about the output torque being limited. Furthermore, the driver can be encouraged to avoid driving with a high required torque, thereby suppressing a rise in temperature of the engine 10. Step S8 is an example of processing executed by the notification control unit.

[0027] If the answer is No in step S7 or if the process of step S8 has been executed, the ECU 20 determines whether the coolant temperature is lower than the second threshold T2 (step S9). If the answer is No in step S9, the process of step S6 and subsequent steps is executed again. If the answer is Yes in step S9, the ECU 20 cancels the second restriction process (step S10).

[0028] FIG. 3 is a timing chart showing an example of the second restriction process. FIG. 3 shows the transition of the output torque of the engine 10 and the temperature of the coolant. FIG. 3 shows a case where the required torque is maintained higher than the second upper limit value P2, and the second restriction process is executed and then released. When the required torque is maintained higher than the second upper limit value P2 and the coolant temperature rises to equal to or exceeds the second threshold value T2, the second restriction process is executed (time t1). In the second restriction process, the output torque is gradually changed so as to be equal to or less than the second upper limit value P2 (from time t1 to time t2). This makes it possible to prevent the driver from feeling uncomfortable when the output torque is limited.

[0029] When the output torque is limited to the second upper limit value P2 or less, the coolant temperature starts to gradually decrease (time t2). When the coolant temperature becomes less than the second threshold value T2, the second limiting process is released (time t3). Even when the second limiting process is released, the output torque is gradually changed to the required torque (from time t3 to time t4). This prevents the driver from feeling uncomfortable when the limit on the output torque is released.

[0030] When the second limiting process is started, the display unit 21 may display that fact. This notifies the driver that the output torque may be limited, and prevents the driver from feeling uncomfortable when the output torque limit is started. When the first limiting process is executed, the display unit 21 may also display that fact.

[0031] In the above embodiment, the temperature of the engine 10 is the temperature of the coolant, but this is not limiting, and the temperature of the lubricating oil that lubricates the engine 10 may also be used.

[0032] In the above embodiment, the ECU 20 that controls the engine 10 mounted on a vehicle has been described as an example of a vehicle control device, but the present invention is not limited to this. For example, the contents of the above embodiment can also be applied to a vehicle control device mounted on a motorcycle or the like, or a vehicle control device mounted on something other than a vehicle, such as a ship or construction machinery. Furthermore, a vehicle equipped with such an ECU may be an engine vehicle equipped with only an engine as a power source for running, or may be a hybrid vehicle equipped with an engine and a motor as power sources for running.

[0033] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0034] 1 vehicle 10 Engine 20 ECU (vehicle control device, first limiting unit, second limiting unit, notification control unit)

Claims

[Claim 1] A control device for a vehicle equipped with an engine, a first limiting unit that executes a first limiting process to limit an output torque of the engine to a first upper limit value or less when the temperature of the engine is equal to or higher than a first threshold value; a second limiting unit that executes a second limiting process to limit the output torque to a second upper limit value or less that is greater than the first upper limit value when the temperature of the engine is equal to or greater than a second threshold value that is lower than the first threshold value and is less than the first threshold value, the first threshold value is set to a lower limit value of a temperature at which the temperature of the engine should be immediately reduced in order to protect components of the engine; the first upper limit value is an upper limit value of the output torque of the engine that can immediately reduce the temperature of the engine when the temperature of the engine is equal to or higher than the first threshold value, the second threshold value is set to a temperature at which it is not necessary to immediately protect the engine components from heat, but at which it is expected that the temperature of the engine will rise to or exceed the first threshold value if the engine continues to operate in this state; the second upper limit value is set to an upper limit value of the output torque of the engine that can ensure the running performance of the vehicle while the temperature of the engine is decreasing, The torque required for the engine is calculated based on an accelerator opening degree, a notification control unit that causes the notification unit to notify that the output torque is being limited when the second limiting process is executed and the required torque for the engine is equal to or greater than the second upper limit value; the notification control unit does not issue a notification that the output torque is limited when the second limiting process is being executed but the required torque is less than the second upper limit value, the second limiting unit gradually changes the output torque to equal to or less than the second upper limit value when the second limiting process is executed in a state in which the torque required of the engine is greater than the second upper limit value; The second limiting unit gradually changes the output torque to the required torque of the engine when the second limiting process, which was being executed when the required torque of the engine was greater than the second upper limit value, is released.

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