JP7598234B2 - Engine Control Unit - Google Patents

Description

The present invention relates to an engine control method and an engine control device.

In order to improve engine fuel efficiency and reduce exhaust gas emissions, it is necessary to control the engine coolant temperature to an appropriate temperature. Cited Document 1 describes how the target value for the coolant temperature is determined based on a signal from a navigation system.

Special Publication No. 2003-513191

In the above-mentioned conventional technology, the engine coolant temperature was controlled based on a signal from the navigation system to minimize fuel consumption and optimize exhaust gas emissions. As a result, the coolant temperature could not always be controlled appropriately in response to the engine load.

The present invention was made in consideration of these problems, and aims to provide a technology that can appropriately control the engine coolant temperature by predicting high engine loads in advance.

One embodiment of the present invention is applied to a control device for an engine mounted on a vehicle. The control device includes an electric water pump that supplies cooling water to the engine, a first cooling water passage that cools the cooling water discharged from the engine in a radiator and circulates the cooling water to the water pump, a second cooling water passage that circulates the cooling water discharged from the engine to the water pump via a heater that warms the interior of the vehicle, a switching valve that switches the destination of the cooling water discharged from the engine between the first cooling water passage and the second cooling water passage, and a control unit that controls the switching valve. The control unit is configured to predict an increase in engine load based on information about a route on which the vehicle travels, set a target water temperature of the engine cooling water when the load increases, obtain an actual water temperature of the cooling water, calculate a required flow rate of the cooling water to achieve the target water temperature based on a deviation between the target water temperature and the actual water temperature, switch the switching valve so that the cooling water flows through the first cooling water passage, and increase the discharge amount of the water pump to ensure the required flow rate, thereby lowering the temperature of the cooling water to the target water temperature before the load increases .

According to the present invention, when the engine load is low, the cooling water temperature is set to a higher temperature (low load water temperature) that can reduce engine friction loss and cooling loss, and when it is predicted that the engine load will increase, the water temperature is lowered to the high load water temperature in advance, thereby appropriately controlling the engine cooling state under high load and improving the engine fuel efficiency.

FIG. 1 is a block diagram of an engine control device according to an embodiment of the present invention. FIG. 2 is a flowchart of the cooling water temperature control. FIG. 3 is a time chart of the cooling water temperature control. FIG. 4 is a flowchart showing a modified example of learning the load increase timing. FIG. 5 is a time chart of a modified embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 is an explanatory diagram of an engine control device 1 centered around an engine 10 according to an embodiment of the present invention.

The engine control device 1 is composed of an internal combustion engine (engine) 10, a cooling water circuit 20, and an engine control unit (ECU) 50 that controls these. The engine control device 1 is mounted on a vehicle and controls the running state of the vehicle.

The engine 10 is composed of a cylinder head 11 and a cylinder block 12. The cylinder head 11 and the cylinder block 12 each have a flow path through which coolant flows. The temperature of the engine 10 is controlled by the coolant flowing through these flow paths. The engine 10 is equipped with a water temperature sensor 81 that detects the coolant temperature, and a knocking sensor 82 that detects knocking of the engine 10.

The cooling water circuit 20 has multiple cooling water flow paths, and is configured so that the cooling water flowing out of the water pump 41 passes through these cooling water flow paths and returns to the water pump 41.

The cooling water circuit 20 includes a first cooling water flow path 21, a second cooling water flow path 22, a head side cooling water flow path 23, a cylinder side cooling water flow path 24, a radiator 31, a heater 32, a water pump 41, a switching valve 42, and an electric water pump 43.

The water pump 41 is mechanically connected to the engine 10 and rotates with the engine 10 to circulate the cooling water in the cooling water circuit 20.

The cooling water discharged from the water pump 41 flows through the cylinder-side cooling water passage 24 and the head-side cooling water passage 23 provided in the engine 10 to cool the engine. The cooling water flowing out of the engine 10 flows through the switching valve 42 to the first cooling water passage 21 and the second cooling water passage 22.

The switching valve 42 is a one-input, two-output switching valve that allows the cooling water discharged from the engine 10 to flow to at least one of the first cooling water flow path 21 and the second cooling water flow path 22. The switching valve 42 switches its flow path under the control of the ECU 50.

The first cooling water flow path 21 is provided with a radiator 31. The radiator 31 lowers the cooling water temperature by performing heat exchange between the cooling water and the atmosphere.

The second coolant flow path 22 is equipped with a heater 32 and an electric water pump 43. The heater 32 is a component of an air conditioning system that warms the vehicle interior. The electric water pump 43 runs on power from a battery or the like, and circulates the coolant even when the engine 10 is stopped.

The ECU 50 controls the operating state of the engine 10. The ECU 50 is configured with, for example, a microcomputer and storage devices such as ROM and RAM, and executes a program stored in the storage device to control the switching valve 42, thereby achieving the cooling water temperature control described below.

The engine control device 1 is equipped with a vehicle control module (VCM) 51. The VCM 51 is configured as, for example, a car navigation system, and prestores information about roads on a map, information about road gradients, etc. The VCM 51 acquires information about the vehicle's speed, direction, time, etc., and manages the vehicle's driving route and destination on the map.

The VCM 51 is equipped with a GPS module 52 as a position information acquisition unit. The GPS module 52 acquires information about the current position (latitude, longitude, and altitude) of the vehicle. The VCM 51 manages the current position of the vehicle on a map based on the current position acquired by the GPS module 52.

Next, we will explain how to control the engine 10 coolant temperature.

The torque required by the engine 10 varies depending on the driver's instructions and the condition of the road surface on which the vehicle is traveling (e.g., the gradient of the road surface).

However, the demand for fuel efficiency of the engine 10 has increased in recent years, and there is a demand to meet the required torque with as little fuel consumption as possible.

One solution to improve fuel economy is to control the coolant temperature. For example, by controlling the temperature to an appropriate level according to the load on the engine 10, it is possible to reduce friction loss and cooling loss in the engine 10, thereby improving fuel economy.

On the other hand, when the load on the engine 10 is high, it is necessary to control the coolant temperature so that the temperature of the engine 10 does not become higher than the allowable temperature. Since the load on the engine 10 varies depending on the gradient of the driving route, it has been common in the past to keep the coolant temperature low so that the temperature of the engine 10 does not rise excessively even if the load on the engine 10 suddenly becomes high, while still taking fuel efficiency into consideration (as shown by the dotted line in the coolant temperature time chart in Figure 3).

Because of this, in the past, the cooling water temperature was not always set to the optimum level.

Therefore, in this embodiment, the engine 10 coolant temperature is controlled according to the load on the engine 10, as described below.

Figure 2 is a flowchart of the cooling water temperature control executed by the ECU 50 as the control unit. This control is realized by a program executed in the ECU 50, and is executed at a predetermined interval (e.g., every 10 ms).

In step S10, the ECU 50 acquires vehicle position information from the VCM 51.

The ECU 50 obtains the current position of the vehicle from the map information stored in the VCM 51 based on the latitude and longitude information obtained by the GPS module 52.

As described below, instead of absolute location information consisting of latitude and longitude, relative location information based on integrated values of time from the vehicle's starting position, vehicle speed, direction, etc. may be obtained.

Next, in step S20, the ECU 50 acquires information on the route along which the vehicle will travel from the VCM 51. The VCM 51 acquires information on the route along which the vehicle is currently traveling from a destination previously set by the driver or the like and the current position of the vehicle.

Next, in step S30, the ECU 50 calculates a vehicle driving load profile based on the acquired driving route information.

A vehicle road load profile is stored information that associates gradient information at all points on a driving route with the vehicle road load corresponding to that gradient. In other words, a vehicle road load profile contains information about the vehicle road load, i.e., the load on the engine 10, that will be imposed by the gradient at that point when the vehicle is traveling along a certain driving route.

Next, in step S40, the ECU 50 calculates how much the road load will change after a predetermined time t1 seconds based on the calculated vehicle road load profile. In step S50, the ECU 50 calculates the output required of the engine 10 in response to this change in road load. The ECU 50 predicts the gradient at the point on the road path that will be reached after the predetermined time t1 seconds, and calculates the change in load corresponding to this gradient from the vehicle road load profile.

In this embodiment, t1 seconds is the period during which the cooling water temperature can be controlled to the target water temperature Tw1 in response to an increase in the driving load, and is set to, for example, several seconds to several tens of seconds.

Next, in step S60, the ECU 50 calculates the target coolant temperature Tw1 for the engine 10, which corresponds to the calculated engine output after t1 seconds.

When the load on the engine 10 is low, i.e. during steady operation, the target water temperature Tw1 is set to a cooling water temperature (low load water temperature) so that the fuel efficiency of the engine 10 is prioritized.

When the load on the engine 10 is low, this refers to a case where the vehicle is not traveling on a sloped road (e.g., an uphill road with a slope of 3 percent or more) and a load that is smaller than the load (predetermined load) required when traveling on such a sloped road is required.

On the other hand, when the load on the engine 10 is high, i.e. when traveling on a slope (uphill road), the cooling water temperature (high load water temperature) is set lower than during steady-state driving according to the load (predetermined load) required of the engine 10.

The low-load water temperature in this embodiment is set to a coolant temperature that is several degrees Celsius to 10 degrees Celsius higher than the coolant temperature during steady-state driving in a conventional engine. This is because, as explained in this flowchart, the coolant temperature can be controlled while predicting an increase in the load on the engine 10, so there is no need to maintain a low coolant temperature in preparation for an increase in the engine load, as with the conventional engine described above.

More specifically, in order to prioritize the fuel economy of the engine 10, it is desirable for the coolant temperature to be high, taking into consideration the reduction of friction loss and cooling loss of the engine 10. On the other hand, as the coolant temperature increases, the knock performance of the engine 10 decreases, and other controls such as retarding the ignition timing are required to address this issue, so it is not necessarily the case that simply increasing the coolant temperature is the answer. In other words, the coolant temperature at which fuel economy during steady driving is most improved while simultaneously achieving both reduced friction loss and cooling loss and knock performance is determined by the structure of the engine 10, etc. The coolant temperature at this time is set as the low-load water temperature.

The high-load water temperature is set appropriately in accordance with the load on the engine 10 according to the gradient of the travel route so that the temperature of the engine 10 does not exceed the allowable temperature and become high. Alternatively, it is set to a temperature at which the knock performance of the engine 10 does not decrease.

Next, the ECU 50 acquires the actual coolant temperature Tw0 from the water temperature sensor 81 of the engine 10 (step S70). Then, it calculates the deviation ΔTw between the acquired actual coolant temperature Tw0 and the calculated target water temperature Tw1 (step S80).

Next, the ECU 50 calculates the amount of coolant required to flow through the radiator 31 so as to satisfy the calculated deviation ΔTw. If the amount of coolant flowing through the radiator 31 is large, the coolant temperature will decrease, and if the amount of coolant flowing through the radiator 31 is small, the coolant temperature will increase. The amount of coolant required is calculated based on the cooling capacity of the radiator 31, the vehicle speed, time t1, and the deviation ΔTw calculated in step S60 (step S90).

Next, based on the calculated required amount of cooling water, the ECU 50 controls the switching valve 42 to determine whether to circulate the cooling water through the first cooling water flow path 21 and pass through the radiator 31, or to stop the flow through the first cooling water flow path 21 and pass only through the second cooling water flow path 22, bypassing the radiator 31 (step S100).

By controlling step S100, the ECU 50 can control the flow rate of the cooling water circulating through the radiator 31 in accordance with the calculated required amount of cooling water, thereby controlling the cooling water temperature.

Figure 3 is a time chart of the cooling water temperature control in this embodiment.

In Figure 3, from the top, the vehicle's running load, the rotation speed of the engine 10, the actual coolant temperature, the state of the switching valve 42, and the coolant flow rate passing through the radiator 31 are shown, with the horizontal axis representing time.

Between timing T0 and timing T01, the vehicle is traveling on a flat road and the rotation speed of the engine 10 is almost constant. In other words, the vehicle is traveling at a steady state.

In this case, the ECU 50 sets the target water temperature Tw1 of the engine 10 after t1 seconds to the low-load water temperature.

Then, as explained in steps S70 to S100 of the above-mentioned flowchart, the ECU 50 calculates the amount of engine cooling water required based on the deviation ΔTw between the actual cooling water temperature Tw0 and the target water temperature Tw1, and controls the switching valve 42 based on the amount of engine cooling water required.

At timing T0 shown in FIG. 3, the switching valve 42 is closed, i.e., the coolant discharged from the engine 10 flows only through the second coolant flow path 22, bypassing the radiator 31 of the first coolant flow path 21. As a result, the coolant is not cooled by the radiator 31, and the coolant temperature is controlled to a relatively high temperature (low load water temperature).

In addition, the ECU 50 may not only control the opening and closing of the switching valve 42, but also control the opening degree of the switching valve 42 based on the deviation ΔTw due to changes in the cooling water temperature, and appropriately control the flow rate of the cooling water flowing through the radiator 31 so that the cooling water temperature is maintained at the target water temperature Tw1.

Next, at timing T01, the ECU 50 predicts that the vehicle will approach an uphill section of the travel route t1 seconds later (timing T02). The ECU 50 sets the target water temperature Tw1, which corresponds to the load on the engine 10 according to the gradient of the uphill section, to the high-load water temperature. Similarly, as explained in steps S70 to S100 of the flowchart above, the ECU 50 calculates the amount of engine cooling water required based on the deviation ΔTw between the actual cooling water temperature Tw0 and the target water temperature Tw1, and controls the switching valve 42 based on the amount of engine cooling water required.

This control controls the switching valve 42 to a predetermined opening amount, so that the cooling water discharged from the engine 10 flows into the radiator 31 of the first cooling water flow path 21.

As a result, the flow rate of the cooling water passing through the radiator 31 increases, and the cooling water temperature gradually decreases, and by timing T02, t1 seconds after timing T01, the cooling water temperature is decreased to the target water temperature Tw1, which is the high-load water temperature.

Between timings T01 and T02, the road is not yet on an incline (steady driving), so the rotation speed of the engine 10 is almost constant. Therefore, the discharge flow rate of the water pump 41 is almost constant, so the flow rate of the cooling water passing through the radiator 31 is maximum (peaks) at timing T11.

Next, at timing T02, the vehicle approaches an uphill road and the gradient of the driving route increases. At this time, the ECU 50 predicts that the gradient of the driving route will increase and that the load on the engine 10 will increase, and has already lowered the cooling water temperature to the high-load water temperature, so that the cooling water temperature can be set to a value that corresponds to the load on the engine 10.

After that, when the vehicle travels uphill, the load on the engine 10 increases and the rotation speed of the engine 10 also increases. The increase in the load on the engine 10 causes the temperature of the cooling water passing through the engine 10 to increase. In addition, as the rotation speed of the engine 10 increases, the discharge flow rate of the water pump 41 also increases, so the cooling water temperature does not rise above the allowable temperature.

In the embodiment of the present invention configured as described above, the engine 10 mounted on the vehicle is controlled by the ECU 50, which is an engine control device. The ECU 50 has a procedure for setting the engine 10 cooling water temperature to a low-load water temperature when the load on the engine 10 is smaller than a predetermined load (the load on the engine 10 required to travel on a sloped road), and a procedure for lowering the cooling water temperature to a high-load water temperature, which is lower than the low-load water temperature, before the load increases when the ECU 50 predicts that the load on the engine 10 will be larger than the predetermined load based on the state of the driving route on which the vehicle is traveling.

By this control, when the load on the engine 10 is low, the cooling water temperature is set to a higher value (low load water temperature) that can reduce friction loss and cooling loss of the engine 10. On the other hand, when it is predicted that the load on the engine 10 will increase, the water temperature is lowered to the high load water temperature in advance, so that the cooling state of the engine 10 at high load can be appropriately controlled, thereby improving the fuel efficiency of the engine 10.

In addition, in this embodiment, a GPS module 52 is provided as a position information acquisition unit that acquires the position information of the vehicle, and the state of the driving route along which the vehicle will travel is predicted from the position information acquired by the GPS module 52, and based on the predicted state of the driving route, it is predicted that the load on the engine 10 will be greater than a predetermined load.

This type of control allows the condition of the driving route to be predicted based on the vehicle position information acquired by the GPS module 52.

In addition, in this embodiment, if it is predicted that the vehicle will travel uphill with a predetermined gradient or more, it is predicted that the load on the engine 10 will be greater than the predetermined load.

This type of control makes it possible to predict in advance when the vehicle will be traveling on a slope and control the engine 10 cooling water temperature.

In this embodiment, the engine 10 is provided with a first coolant flow path 21 having a radiator 31, a second coolant flow path 22 that bypasses the first coolant flow path 21, and a switching valve 42 that switches the flow of coolant to the first coolant flow path 21 and the second coolant flow path 22. The ECU 50 controls the coolant temperature by opening and closing the switching valve 42 to control the flow rate.

By using this type of control, the coolant temperature can be controlled by controlling the switching valve 42 based on the predicted load of the engine 10.

In this embodiment, when changing the cooling water temperature from the low load water temperature to the high load water temperature, the ECU 50 may operate the electric water pump 43 in addition to switching the switching valve 42 to further increase the amount of cooling water passing through the radiator 31. By controlling in this manner, the cooling water temperature can be changed to the high load water temperature more quickly.

In this embodiment, information regarding the vehicle's travel route is obtained based on the destination set by the VCM 51 and the current position acquired by the GPS module 52, but this is not limited to the above.

For example, when a vehicle repeatedly travels the same route from a starting point to a destination, the ECU 50 constantly records the time-dependent changes in the load (torque) of the engine 10 during that time. Then, by learning the recorded torque changes, the ECU 50 becomes able to predict the point at which the load of the engine 10 will rise above a predetermined load, for example, based on the elapsed time from the starting point.

Figure 4 is a flowchart showing how the load of the engine 10 is learned in a modified version of this embodiment. This control is realized by a program executed in the ECU 50, and is executed at a predetermined interval (e.g., every 10 ms).

First, when the vehicle starts to move (step S110), the ECU 50 records the change in the load on the engine 10 over time (step S120).

Then, when the vehicle reaches the destination (step S130), the ECU 50 learns the recorded changes in the load on the engine 10 over time (step S140).

Learning the load change over time can be done, for example, by obtaining the same pattern of load change over time from already recorded information, accumulating and recording these, and learning the timing at which the load increases on the route that the vehicle repeatedly travels.

By performing this type of learning, the ECU 50 can predict that the learned timing is the timing when the load on the engine 10 will increase, and can control the cooling water temperature as described above t1 seconds before this timing.

In this manner, in a modified embodiment of the present invention, the ECU 50 further includes a procedure for learning and storing the driving route that the vehicle repeatedly travels, and a procedure for predicting that the load on the engine 10 will be greater than a predetermined load based on the results of the learning.

By using this type of control, even in a vehicle that does not have a device such as a GPS that acquires the vehicle's current position, when the load on the engine 10 is low, the low-load water temperature can be set to reduce friction loss and cooling loss in the engine 10. When it is predicted that the load on the engine 10 will increase, the high-load water temperature is set according to the load on the engine 10, thereby improving the fuel efficiency of the engine.

Note that the above-mentioned learning method is just one example, and learning may be performed using other methods.

Next, we will explain a variation of this embodiment.

In Figures 1 to 3, an example is described in which the coolant temperature of the engine 10 is controlled by the switching valve 42. In contrast, in a modified example, the water pump 41 is configured as an electric pump, and the discharge volume of the water pump 41 can be changed by control of the ECU 50. As a result, the discharge volume of the water pump 41 does not depend on the rotation speed of the engine 10, and the discharge volume is controlled by the ECU 50. Note that when the water pump 41 is configured as an electric pump, the coolant can flow regardless of whether the engine 10 is running, so the electric water pump 43 can be omitted.

Figure 5 is a time chart for a modified version of this embodiment, and corresponds to Figure 3.

In this modified example, at timing T0, as described in FIG. 3, the ECU 50 closes the switching valve 42 to bypass the radiator 31 so that the cooling water temperature becomes the low-load water temperature.

After that, at timing T21, ECU 50 predicts that the vehicle will approach a slope on the travel route after t2 seconds (timing T02). This t2 seconds is the time required for the cooling water temperature to drop to the high-load water temperature by the control corresponding to step S100 in FIG. 2, and is shorter than t1 seconds described in FIG. 3. Timing T21 is later than timing T01 described in FIG. 3 (closer to timing T02).

In this modified example, when the coolant temperature is changed (step S100), the ECU 50 controls the switching valve 42 to an open state to allow the coolant to flow through the radiator 31 of the first coolant flow path 21, and controls the water pump 41 to increase its discharge rate to increase the amount of coolant passing through the radiator 31.

As shown in FIG. 5, the flow rate of the cooling water passing through the radiator 31 changes from minimum to maximum between timing T21 and timing T22. As a result, the cooling water temperature changes from the low load water temperature to the high load water temperature between timing T21 and timing T02.

Therefore, compared to the control of only the switching valve 42 described in FIG. 3, the cooling water temperature can be changed more quickly, and the low-load water temperature can be changed to the high-load water temperature more quickly. Therefore, the timing for predicting a slope and changing to the high-load water temperature can be delayed, and the period of low-load water temperature during steady driving can be extended.

In the example shown in Figure 5, the time when control to a high-load water temperature begins (t2 seconds before T02, timing T21) is later than the time in Figure 3 (t1 second before T02, timing T01). During this period, i.e., between T21 and T01, the vehicle can be driven at a low-load water temperature. This improves fuel efficiency during this period compared to the example shown in Figure 3.

The ECU 50 may also vary only the discharge volume of the water pump 41 without controlling the switching valve 42, thereby changing the amount of cooling water passing through the radiator 31.

The above describes the embodiments of the present invention and their variations. However, the above embodiments and variations merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

In the above-described embodiment, an example was shown in which the increase in the load on the engine 10 was predicted based on the gradient of the travel route, but this is not limited to this. For example, the points where a general road merges into an expressway, or where a narrow road changes into a wide road, may be predicted as points where the vehicle's travel load will increase.

In addition, in the flowchart of Figure 2 described above, if it is predicted that the road will turn from an uphill slope to a flat road in t1 seconds and the driving load is predicted to decrease, the timing for setting the target water temperature Tw1 to the low-load water temperature may be set immediately, rather than after t1 seconds.

In addition, in this embodiment, the vehicle is described as being driven by the engine 10, but this is not limited to the above. The present invention can be applied to a vehicle that is driven by both the engine 10 and the motor, or a vehicle that is driven by generating electricity from a generator using the engine 10 to drive a motor.

Reference Signs List 1: Engine control device 10: Engine 20: Cooling water circuit 21: First cooling water flow path 22: Second cooling water flow path 23: Head side cooling water flow path 24: Cylinder side cooling water flow path 31: Radiator 41: Water pump 42: Switching valve 43: Electric water pump 50: ECU (control unit)
51 VCM
52 GPS module (location information acquisition unit)
81 Water temperature sensor

Claims (3)

A control device for an engine mounted on a vehicle,
an electric water pump for supplying cooling water to the engine;
a first cooling water passage for cooling the cooling water discharged from the engine in a radiator and circulating the cooling water to the water pump;
a second cooling water passage for circulating the cooling water discharged from the engine to the water pump via a heater for warming an interior of the vehicle;
a switching valve that switches a destination of the cooling water discharged from the engine between the first cooling water passage and the second cooling water passage; and a control unit that controls the switching valve,
The control unit is
predicting an increase in the load of the engine based on information on a route along which the vehicle is traveling;
setting a target water temperature of the engine cooling water when the load increases ;
Acquire an actual temperature of the cooling water;
Calculating a required flow rate of the cooling water to achieve the target water temperature based on a deviation between the target water temperature and the actual water temperature;
The switching valve is switched so that the cooling water flows through the first cooling water passage , and the discharge amount of the water pump is increased to secure the required flow rate, and the temperature of the cooling water is lowered to the target water temperature prior to an increase in the load .
Engine control device. 2. The engine control device according to claim 1, wherein the control unit is configured to predict an increase in the load when a gradient of a slope road predicted for the travel route is equal to or greater than a predetermined gradient. 2. The engine control device according to claim 1, wherein the control unit is configured to set the target water temperature to a temperature lower than that during steady running of the vehicle when the load increases.

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