JP2024058419A - Vehicle control device - Google Patents

Abstract

An object of the present invention is to provide a vehicle control device that suppresses effects on drivability.
[Solution] 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 value; and a second limiting unit that executes a second limiting process to limit the output torque to a second upper limit value or less than the first upper limit value when the temperature of the engine is equal to or higher than a second threshold value lower than the first threshold value and less than the first threshold value.
[Selected figure] Figure 2

Description

The present invention relates to a vehicle control device.

When the engine becomes too hot, the engine output torque may be limited to a predetermined upper limit in order to protect the engine components (see, for example, Patent Document 1).

JP 2005-083215 A

If the engine's output torque is suddenly restricted in this way, it may affect drivability.

The present invention aims to provide a vehicle control device that reduces the impact on drivability.

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

The device may also include a notification control unit that notifies the notification unit that the output torque is limited when the second limiting process is being executed.

The notification control unit may cause the notification unit to notify the fact 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.

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

The second limiting unit may gradually change the output torque to the torque required for the engine when the second limiting process, which has been performed while the torque required for the engine is greater than the second upper limit, is released.

The present invention provides a vehicle control device that reduces the impact on drivability.

FIG. 1 is a schematic diagram of an engine. FIG. 2 is a flowchart showing an example of the torque limiting control executed by the ECU. FIG. 3 is a timing chart showing an example of the second restriction process.

[General configuration of the vehicle]
FIG. 1 is a schematic diagram showing a general configuration of a vehicle 1. The vehicle 1 includes 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 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 an 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 is 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 driving wheels 18 via the axles 17.

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 memory such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The ECU 20 executes various control processes related to the engine 10 on the CPU by executing programs installed in the memory. 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 restriction unit, a second restriction unit, and a notification control unit, which will be described in detail later.

The ECU 20 is connected to a crank angle sensor s1, a water temperature sensor s2, an air flow meter s3, and an accelerator opening sensor s4, and receives the output values of these sensors. 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 of the engine 10. The accelerator opening sensor s4 detects the accelerator opening, which is the opening of the accelerator pedal.

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

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 directly or in a slip-engaged state.

The automatic transmission 14 is a stepped transmission that includes multiple hydraulic friction engagement elements and a planetary gear device. In the automatic transmission 14, the multiple friction engagement elements are selectively engaged, so that multiple forward gears, reverse gears, or neutral gear positions can be selectively established.

The display unit 21 is controlled by the ECU 20 and is provided on the vehicle's instrument panel. 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 or navigation system.

[Torque limit control]
2 is a flow chart showing an example of the torque limiting control executed by the ECU 20. This control is continuously repeated while the ignition is on. The ECU 20 judges 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 a lower limit value of the temperature at which the temperature of the engine 10 should be immediately lowered from the viewpoint of protecting the components of the engine 10.

If the answer is Yes in step S1, the ECU 20 executes the 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. In detail, the first limiting process is a process for lowering 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 when the first limiting process is started. Therefore, if the output torque controlled based on the accelerator opening, etc. is already equal to or less than the first upper limit value P1 at the time when the first limiting process is started, the output torque is not limited. Also, if the torque required for 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 lower 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 the components of the engine 10 can be protected from high heat. Step S2 is an example of a process executed by the first restriction unit.

Next, the ECU 20 determines whether the coolant temperature is less than the first threshold T1 (step S3). If the answer is No in step S3, step S2 is continued again. If the answer is Yes in step S3, the ECU 20 releases the first restriction process (step S4).

If the answer is No in step S1, it is determined whether the temperature of the coolant in the ECU 20 is equal to or higher than the 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 engine 10 components from heat, but at which it is expected that the temperature of the coolant will rise to or higher than the first threshold value T1 if the engine 10 continues to operate in this state. If the answer is No in step S5, this control ends.

If the answer is Yes in step S5, the ECU 20 executes the 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. Like 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 when 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 second limiting process is started, 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.

In this way, when step S1 is No and step S5 is Yes, i.e., when the coolant temperature is equal to or higher than the second threshold T2 and 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 equal 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 significantly. This makes it possible to suppress the impact on drivability. Step S6 is an example of a process executed by the second restriction unit.

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 answer is Yes in step S7, the ECU 20 causes the display unit 21 to display that the output torque is limited (step S8). This makes it possible to avoid giving the driver a sense of discomfort due to the output torque being limited. In addition, the driver can be encouraged to avoid driving with a high required torque, and the temperature rise of the engine 10 can be suppressed. Step S8 is an example of a process executed by the notification control unit.

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 less than the second threshold T2 (step S9). If the answer is No in step S9, the process of steps S6 and onward is executed again. If the answer is Yes in step S9, the ECU 20 releases the second restriction process (step S10).

Figure 3 is a timing chart showing an example of the second restriction process. Figure 3 shows the transition of the output torque of the engine 10 and the temperature of the cooling water. Figure 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 released. When the required torque is maintained at a value higher than the second upper limit value P2 and the temperature of the cooling water rises to be equal to or higher than the second threshold value T2, the second restriction process is executed (time t1). In the second restriction process, the output torque is gradually changed (from time t1 to time t2) so as to be equal to or lower than the second upper limit value P2. This makes it possible to avoid the driver feeling uncomfortable about the output torque being restricted.

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 falls below 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 about the release of the output torque limit.

When the second limiting process is started, the display unit 21 may display that fact. This makes it possible to notify the driver that the output torque may be limited, and to avoid the driver 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.

In the above embodiment, the temperature of the coolant is used as the temperature of the engine 10, but this is not limited to this, and the temperature of the lubricating oil that lubricates the engine 10 may also be used.

In the above embodiment, the ECU 20 that controls the engine 10 mounted on the vehicle has been described as an example of a vehicle control device, but this is not limiting. For example, the contents of the above embodiment can also be applied to vehicle control devices mounted on motorcycles, etc., and vehicle control devices mounted on things other than vehicles, such as ships and 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 a hybrid vehicle equipped with an engine and a motor as power sources for running.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

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

Claims (5)

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 a 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 greater than the first upper limit value when the temperature of the engine is equal to or greater than a second threshold value lower than the first threshold value and less than the first threshold value. The vehicle control device of claim 1, further comprising a notification control unit that causes a notification unit to notify the driver that the output torque is being limited when the second limiting process is being executed. The vehicle control device of claim 2, wherein the notification control unit causes the notification unit to notify the fact 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. A control device for a vehicle according to any one of claims 1 to 3, wherein the second limiting unit gradually changes the output torque to equal to or less than the second upper limit when the second limiting process is executed in a state in which the torque required for the engine is greater than the second upper limit. A control device for a vehicle according to any one of claims 1 to 3, wherein the second limiting unit gradually changes the output torque to the required torque for the engine when the second limiting process, which has been executed while the required torque for the engine is greater than the second upper limit, is released.

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