Fuel saving control device and fuel saving control method

Abstract

The fuel economy control device (100) includes: a margin driving force calculation section (101) that calculates a margin driving force; a fuel economy control section (102) that, when the margin driving force is equal to or greater than a predetermined threshold value, performs fuel economy control that uses a reduction correction value corresponding to the margin driving force to reduce an indicated fuel injection amount corresponding to an accelerator opening degree, and that, when the margin driving force becomes less than the predetermined threshold value, stops the fuel economy control; a vehicle position detection section (107) that detects a vehicle position; a map information storage section (108) that stores map information; a front curvature radius determination section (109) that determines a front curvature radius based on the vehicle position and the map information; and the fuel economy control section (102) does not cause the reduction correction value to vary by more than a predetermined variation rate when the front curvature radius is less than a predetermined threshold value.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a fuel economy control device and a fuel economy control method. BACKGROUND

[0002] A fuel economy control is widely known in which, in a case where a vehicle is running at an indicated fuel injection amount corresponding to an accelerator opening degree, when a margin driving force becomes equal to or greater than a threshold value, the indicated fuel injection amount is intentionally corrected downward using a correction value for downward correction corresponding to the margin driving force, to reduce an actual fuel consumption amount of the engine (for example, refer to Patent Literature 1). Although the acceleration force of the vehicle is limited by executing the fuel economy control, the fuel economy control is stopped when the margin driving force is less than the threshold value or a kickdown operation is detected. Therefore, the driver is less likely to be affected by the acceleration force limitation of the vehicle, and the convenience of the driver is not significantly impaired by executing the fuel economy control.

[0003] Examples of related art of the fuel economy control device are disclosed in Patent Literature 1, Patent Literature 2, and Patent Literature 3, in addition to Patent Literature 1.

[0004] Prior Art Documents

[0005] Patent Literature

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2016-061177

[0007] Patent Literature 2: Japanese Patent Application Publication No. 2004-168154

[0008] Patent Literature 3: Japanese Patent Application Publication No. 2012-076700 SUMMARY

[0009] Problems to be Solved by the Invention

[0010] As described above, when the fuel economy control is executed, the fuel economy performance of the vehicle is maximized by using the correction value for downward correction corresponding to the margin driving force. Specifically, the actual fuel consumption amount is reduced as much as possible by making the correction value for downward correction increase as the margin driving force becomes greater. However, because the margin driving force frequently changes, for example, in a case where a mountain road (a meandering road) in which a plurality of uphill roads are connected by flat curves or flat straight roads, respectively, is traveled, the correction value for downward correction also frequently changes. Therefore, because the acceleration force of the vehicle frequently changes so that the state of the vehicle becomes unstable, there is a risk of impairing the convenience and safety of the driver.

[0011] Therefore, an object of the present disclosure is to provide a fuel economy control device and a fuel economy control method that can suppress frequent changes in vehicle behavior and ensure the convenience and safety of the driver by executing fuel economy control even in a situation in which the margin driving force frequently changes.

[0012] Means for solving the problem

[0013] In the first technical solution of the present disclosure, a fuel economy control device is provided, which includes a margin driving force calculation unit configured to calculate a margin driving force, and a fuel economy control unit configured to execute fuel economy control that uses a reduction correction value corresponding to the margin driving force to reduce an indicated fuel injection amount corresponding to an accelerator opening degree when the margin driving force is equal to or greater than a first threshold value, and to stop the fuel economy control when the margin driving force is less than the first threshold value. The fuel economy control device further includes a vehicle position detection unit configured to detect a vehicle position, a map information storage unit configured to store map information, and a front curvature radius determination unit configured to determine a front curvature radius based on the vehicle position and the map information. The fuel economy control unit is configured not to change the reduction correction value by a predetermined change rate or more when the front curvature radius is less than a second threshold value.

[0014] The fuel economy control unit can be further configured not to change the reduction correction value by the predetermined change rate or more even when the margin driving force crosses the first threshold value when the front curvature radius is less than the second threshold value.

[0015] In the second technical solution of the present disclosure, a fuel economy control device is provided, which includes a margin driving force calculation unit configured to calculate a margin driving force, and a fuel economy control unit configured to execute fuel economy control that uses a reduction correction value corresponding to the margin driving force to reduce an indicated fuel injection amount corresponding to an accelerator opening degree when the margin driving force is equal to or greater than a first threshold value, and to stop the fuel economy control when the margin driving force is less than the first threshold value. The fuel economy control device further includes a vehicle position detection unit configured to detect a vehicle position, a map information storage unit configured to store map information, and a front curvature radius determination unit configured to determine a front curvature radius based on the vehicle position and the map information. The fuel economy control unit is configured not to change the reduction correction value by a predetermined change rate or more when the front curvature radius is less than a second threshold value.

[0016] The fuel economy control unit can be further configured not to change the reduction correction value by the predetermined change rate or more even when the margin driving force crosses the first threshold value when the front curvature radius is less than the second threshold value.

[0017] In the third aspect of the present disclosure, there is provided a fuel economy control method including: a margin driving force calculation step of calculating a margin driving force; a fuel economy control execution step of executing, when the margin driving force is equal to or greater than a first threshold value, fuel economy control of correcting an indicated fuel injection amount corresponding to an accelerator opening degree using a correction value corresponding to the margin driving force; and a fuel economy control stop step of stopping the fuel economy control when the margin driving force is less than the first threshold value. The fuel economy control method further includes a vehicle position detection step of detecting a vehicle position and a front curvature radius determination step of determining a front curvature radius based on the vehicle position and map information. In the fuel economy control execution step and the fuel economy control stop step, the correction value is not changed by more than a predetermined change rate when the front curvature radius is less than a second threshold value.

[0018] Also, in the fuel economy control execution step and the fuel economy control stop step, the correction value is not changed by more than the predetermined change rate even when the margin driving force crosses the first threshold value when the front curvature radius is less than the second threshold value.

[0019] In the fourth aspect of the present disclosure, there is provided a fuel economy control method including: a margin driving force calculation step of calculating a margin driving force; a fuel economy control execution step of executing, when the margin driving force is equal to or greater than a first threshold value, fuel economy control of correcting an indicated fuel injection amount corresponding to an accelerator opening degree using a correction value corresponding to the margin driving force; and a fuel economy control stop step of stopping the fuel economy control when the margin driving force is less than the first threshold value. The fuel economy control method further includes a vehicle position detection step of detecting a vehicle position and a front curvature radius determination step of determining a front curvature radius based on the vehicle position and map information. In the fuel economy control execution step and the fuel economy control stop step, the correction value is not changed by more than a predetermined change rate when the front curvature radius is less than a second threshold value.

[0020] Also, in the fuel economy control execution step and the fuel economy control stop step, the correction value is not changed by more than the predetermined change rate even when the margin driving force crosses the first threshold value when the front curvature radius is less than the second threshold value.

[0021] Effects of Invention

[0022] According to the present disclosure, it is possible to provide a fuel economy control device and a fuel economy control method capable of suppressing frequent changes in a vehicle state by executing fuel economy control and ensuring convenience and safety for a driver even in a situation in which a margin driving force frequently changes.

[0023] BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a configuration diagram of a fuel economy control device of an embodiment of the present disclosure.

[0025] Figure 2 is a flowchart of a basic fuel economy control method of a fuel economy control method of an embodiment of the present disclosure.

[0026] Figure 3 is a flowchart of an extended fuel economy control method of a fuel economy control method of an embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0028] First, a fuel economy control device will be described.

[0029] The fuel economy control device is installed on an automobile (a manual transmission vehicle or an automatic transmission vehicle) that travels by transmitting a driving force of an engine to driving wheels of the automobile via a transmission.

[0030] As shown in Figure 1 , the fuel economy control device 100 of the embodiment of the present disclosure includes a margin driving force calculation section 101 for calculating a margin driving force, and a fuel economy control section 102 for stopping fuel economy control when the margin driving force is less than a first threshold value.

[0031] Generally, although the vehicle travels in accordance with an indicated fuel injection amount corresponding to an accelerator opening degree, when the margin driving force becomes equal to or greater than the first threshold value, fuel economy control is executed that uses a drop correction value corresponding to the margin driving force to drop correct the indicated fuel injection amount.

[0032] The margin driving force is defined by a difference between a driving force of the driving wheels and a travel resistance of the vehicle. Further, by the stopping of the fuel economy control, it means that the drop correction of the indicated fuel injection amount corresponding to the accelerator opening degree is stopped by setting the drop correction value to zero regardless of the margin driving force, and it is returned to the normal control.

[0033] The margin driving force calculation section 101 is configured to calculate the margin driving force by calculating the difference between the driving force of the drive wheels and the running resistance of the vehicle. The fuel economy control section 102 is configured to limit the acceleration force of the vehicle by intentionally reducing the indicated fuel injection amount corresponding to the accelerator opening of the driver by using a reduction correction value corresponding to the margin driving force when the margin driving force is equal to or greater than the first threshold value, thereby reducing the actual fuel consumption of the engine. The limit of the acceleration force of the vehicle (the force for acceleration) means the limit of the torque of the engine, the output of the engine, and / or the acceleration of the vehicle (the rate of change with respect to the speed before acceleration). Further, the fuel economy control section 102 can be further configured to stop the fuel economy control even when the margin driving force is not less than the first threshold value when the driver's deep accelerator operation is detected. This is because, even when the driver needs the acceleration force of the vehicle and presses the deep accelerator switch or deeply depresses the accelerator pedal, the fuel economy performance of the vehicle does not need to be prioritized, and the convenience and safety of the driver should be ensured first. The controller 103 grasps all variables for controlling the engine using various measuring instruments. For example, the controller 103 grasps the accelerator opening using the accelerator position sensor 104. Further, the controller 103 is provided with an indicated fuel injection amount calculation section 105 for calculating the indicated fuel injection amount corresponding to the accelerator opening, and controls a fuel injector 106 for injecting fuel into the cylinder of the engine. The fuel injector 106 is configured to inject fuel into the cylinder of the engine at the indicated fuel injection amount corresponding to the accelerator opening.

[0034] As described above, when the fuel economy control is performed, the fuel economy performance of the vehicle is maximized by using the reduction correction value corresponding to the margin driving force. Specifically, the actual fuel consumption is reduced as much as possible by increasing the reduction correction value as the margin driving force becomes larger. However, in the case where, for example, the vehicle travels on a mountain road (a winding road) in which a plurality of uphill roads are connected by flat curves or flat straight roads, the margin driving force frequently changes, and thus the reduction correction value also frequently changes. Therefore, there is a risk that the convenience and safety of the driver are impaired because the acceleration force of the vehicle frequently changes and the state of the vehicle becomes unstable.

[0035] Therefore, the fuel economy control device 100 further includes a vehicle position detection unit 107 for detecting a vehicle position, a map information storage unit 108 for storing map information, and a front curvature radius determination unit 109 for determining a front curvature radius based on the vehicle position and the map information. The front curvature radius is a radius of curvature of a road between two points predicted to be traveled by the vehicle in the near future. The vehicle position detection unit 107 is constituted by, for example, a global positioning system receiver. The map information storage unit 108 is constituted by, for example, a storage medium independent of the controller 103.

[0036] In the fuel economy control device 100, the fuel economy control unit 102 is configured to not allow the decrease correction value to vary by more than a predetermined variation rate, or in other words, to limit the decrease correction value to be less than the predetermined variation rate, when the front curvature radius is less than the second threshold value. The reason for this is that because the margin driving force is predicted to frequently vary when the front curvature radius is less than the second threshold value, the behavior of the vehicle is prevented from frequently varying in conjunction with the execution of the fuel economy control, and the convenience and safety of the driver are ensured, by not allowing the decrease correction value to vary by more than the predetermined variation rate.

[0037] Further, the fuel economy control unit 102 can be further configured to not allow the decrease correction value to vary by more than the predetermined variation rate even when the margin driving force crosses the first threshold value when the front curvature radius is less than the second threshold value. Here, the state in which the margin driving force crosses the first threshold value refers to a state in which the margin driving force exceeds the first threshold value and a state in which the margin driving force is less than the first threshold value repeatedly occur within a predetermined time. The reason for this is that although the fuel economy control is stopped when the margin driving force becomes less than the first threshold value during the execution of the fuel economy control, the decrease correction value becomes unlikely to maintain its value (for example, becomes 0 when the decrease correction value is an addition value, and becomes 1 when the decrease correction value is a multiplication value) because the fuel economy control is stopped, so there is a possibility that the decrease correction value will greatly vary when the execution and the stop of the fuel economy control are switched. Further, the reason for this is that although the fuel economy control is executed when the margin driving force becomes the first threshold value or more during the stop of the fuel economy control, the decrease correction value maintains its value because the fuel economy control is executed, so there is a concern that the decrease correction value will greatly vary when the stop and the execution of the fuel economy control are switched. When the decrease correction value greatly varies, the acceleration of the vehicle also greatly varies, so the state of the vehicle becomes unstable. In addition, the predetermined variation rate can be a constant value, and can also be a variable value. As a method of not allowing the decrease correction value to vary by more than the predetermined variation rate, for example, a method of using an average filter to make the variation range of the decrease correction value small is considered. By appropriately adjusting the filter coefficient of the average filter, the variation of the acceleration of the vehicle can be suppressed to a minimum.

[0038] Furthermore, although the fuel-saving control unit 102 is configured to prevent the decrease correction value from changing by a predetermined rate or more when the radius of curvature in front is less than the second threshold, it is also possible for the fuel-saving control unit 102 to completely prevent the decrease correction value from changing when the radius of curvature in front is less than the second threshold; in other words, the decrease correction value is fixed. Compared to the case where the decrease correction value is not changed by a predetermined rate or more, the fuel-saving performance of the vehicle may be slightly reduced when the decrease correction value is not changed at all. However, because the vehicle's acceleration force is not changed at all when the radius of curvature in front is less than the second threshold, maximum safety can be provided to the driver in situations that could potentially pose a danger. Therefore, by appropriately selecting between control that prevents the decrease correction value from changing by a predetermined rate or more, and control that prevents the decrease correction value from changing at all, the fuel-saving performance of the vehicle can be improved, and driver convenience and safety can be ensured.

[0039] Next, the methods for controlling fuel costs will be explained.

[0040] like Figure 2 As shown, the fuel-saving control method of this disclosure includes a basic fuel-saving control method M100 executed by the fuel-saving control device 100 after the ignition switch is turned on. The basic fuel-saving control method M100 includes a margin driving force calculation step S101, a margin driving force determination step S102, a fuel-saving control execution step S103, and a fuel-saving control stop step S104.

[0041] In the margin driving force calculation step S101, the margin driving force is calculated using the margin driving force calculation unit 101. In the margin driving force determination step S102, the fuel-saving control unit 102 determines whether the margin driving force has become above the first threshold. If the margin driving force becomes above the first threshold, the process proceeds to the fuel-saving control execution step S103; if the margin driving force is less than the first threshold, the process proceeds to the fuel-saving control stop step S104. In the fuel-saving control execution step S103, the fuel-saving control unit 102 executes fuel-saving control, which uses a reduction correction value corresponding to the margin driving force to reduce the indicated fuel injection quantity corresponding to the throttle opening. In the fuel-saving control stop step S104, the fuel-saving control unit 102 stops the fuel-saving control.

[0042] In addition, such as Figure 3As shown, the fuel saving control method of the embodiment of the present disclosure includes an extended fuel saving control method M200 executed by the fuel saving control device 100 after the ignition switch is turned on. The extended fuel saving control method M200 includes a vehicle position detecting step S201, a front curvature radius determining step S202, a front curvature radius determining step S203, and a low variation rate step S204 of the lowering correction value.

[0043] In the vehicle position detecting step S201, the vehicle position is detected by the vehicle position detecting section 107. In the front curvature radius determining step S202, the front curvature radius is determined based on the vehicle position and the map information by the front curvature radius determining section 109. In the front curvature radius determining step S203, it is determined by the fuel saving control section 102 whether the front curvature radius is smaller than the second threshold value, and when the front curvature radius is smaller than the second threshold value, the process proceeds to the low variation rate step S204 of the lowering correction value, and when the front curvature radius is not smaller than the second threshold value, the process returns to the vehicle position detecting step S201. In the low variation rate step S204 of the lowering correction value, the lowering correction value is made to be low variation rate by the fuel saving control section 102. Therefore, in the aforementioned fuel saving control executing step S103, when the front curvature radius is smaller than the second threshold value, it is possible to make the lowering correction value not to be varied by more than a predetermined variation rate. Further, when the front curvature radius is smaller than the second threshold value, it is possible to make the lowering correction value not to be varied by more than a predetermined variation rate even if the margin driving force crosses the first threshold value. For example, a numerical value has no meaning, and when the state in which the fuel saving control is executed with the lowering correction value set to -10% is changed to the state in which the fuel saving control is stopped with the lowering correction value set to 0%, it is not sudden to make the lowering correction value 0%, but it is gradually made to approach 0% such as -8%, -6%,.... Further, conversely, when the state in which the fuel saving control is stopped with the lowering correction value set to 0% is changed to the state in which the fuel saving control is executed with the lowering correction value set to -10%, it is not sudden to make the lowering correction value -10%, but it is gradually made to approach -10% such as -2%, -4%,.... In addition, when the vehicle position detecting step S201 is returned from the front curvature radius determining step S203 and the lowering correction value is made to be low variation rate by the last control cycle, the low variation rate of the lowering correction value is released.

[0044] Further, instead of performing the lowering correction value low variation rate step S204, a lowering correction value fixation step can also be performed. In the lowering correction value fixation step, the lowering correction value is fixed by the fuel saving control section 102. For example, the lowering correction value before the lowering correction value fixation step is performed is used as a fixed value. For example, the value is meaningless, and when the state in which the lowering correction value is set to -10% to perform the fuel saving control is changed to the state in which the lowering correction value is set to 0% to stop the fuel saving control, the lowering correction value is not made to be 0%, but is maintained at -10%. Therefore, in the aforementioned fuel saving control performing step S103 and fuel saving control stopping step S104, when the front curvature radius is smaller than the second threshold value, it is possible to make the lowering correction value not vary at all. Further, when the front curvature radius is smaller than the second threshold value, even if the margin driving force crosses the first threshold value, it is possible to make the lowering correction value not vary at all.

[0045] As described above, in the present disclosure, in a case where there is a possibility that the margin driving force frequently varies because the front curvature radius is smaller than the second threshold value, it is set so that the lowering correction value does not vary by a predetermined variation rate or more or does not vary at all. Therefore, even in a situation where the margin driving force frequently varies, it is possible to suppress the frequent variation of the vehicle state by performing the fuel saving control and to ensure the convenience and safety of the driver. In particular, because in the case of a manual transmission vehicle, it is possible to urge the driver to perform upshift in advance by limiting the acceleration force of the vehicle, it is possible to greatly improve the fuel saving performance of the vehicle by performing the fuel saving control.

[0046] The present application is based on Japanese Patent Application (JP 2016-200899) filed on October 12, 2016, and the content thereof is incorporated herein by reference.

[0047] Industrial applicability

[0048] In the present disclosure, even in a situation where the margin driving force frequently varies, it is possible to suppress the frequent variation of the vehicle state by performing the fuel saving control, and to ensure the convenience and safety of the driver, and is useful for a fuel saving control device and a fuel saving control method, and the like.

[0049] Explanation of reference signs

[0050] 100 fuel saving control device

[0051] 101 margin driving force calculation section

[0052] 102 fuel saving control section

[0053] 103 controller

[0054] 104 throttle position sensor

[0055] 105 fuel injection amount calculation section

[0056] 106 fuel injector

[0057] 107 vehicle position detection section

[0058] 108 map information storage section

[0059] 109 front curvature radius determination section

[0060] M100 basic fuel economy control method

[0061] S101 excess drive force calculation step

[0062] S102 excess drive force determination step

[0063] S103 fuel economy control execution step

[0064] S104 fuel economy control stop step

[0065] M200 extended fuel economy control method

[0066] S201 vehicle position detection step

[0067] S202 front curvature radius determination step

[0068] S203 front curvature radius determination step

[0069] S204 descent correction value low variation rate step

Claims

1. A fuel economy control device characterized by comprising: comprises: a margin driving force calculation section for calculating a margin driving force defined by a difference between a driving force of a drive wheel and a running resistance of a vehicle, and a fuel economy control section for executing, when the margin driving force is equal to or greater than a first threshold value, fuel economy control for decreasing an indicated fuel injection amount corresponding to an accelerator opening degree using a decrease correction value corresponding to the margin driving force, and for stopping the fuel economy control when the margin driving force is less than the first threshold value; the fuel economy control device further comprises: a vehicle position detection section for detecting a vehicle position, a map information storage section for storing map information, and a front curvature radius determination section for determining a front curvature radius based on the vehicle position and the map information; the fuel economy control section is configured to, in a case where a plurality of uphill roads are connected by flat curves or flat straight roads on a mountain road, not cause the decrease correction value to change by more than a predetermined change rate when the front curvature radius is less than a second threshold value during execution of the fuel economy control, even if the margin driving force crosses the first threshold value, that is, a state where the margin driving force exceeds the first threshold value and a state where the margin driving force is less than the first threshold value repeatedly occur within a predetermined time.

2. A fuel economy control method characterized by, comprises: a margin driving force calculation step for calculating a margin driving force defined by a difference between a driving force of a drive wheel and a running resistance of a vehicle; a fuel economy control execution step for executing, when the margin driving force is equal to or greater than a first threshold value, fuel economy control for decreasing an indicated fuel injection amount corresponding to an accelerator opening degree using a decrease correction value corresponding to the margin driving force; and a fuel economy control stop step for stopping the fuel economy control when the margin driving force is less than the first threshold value; the fuel economy control method further comprises: a vehicle position detection step for detecting a vehicle position; and a front curvature radius determination step for determining a front curvature radius based on the vehicle position and map information; in the fuel economy control execution step and the fuel economy control stop step, in a case where a plurality of uphill roads are connected by flat curves or flat straight roads on a mountain road, the decrease correction value is not caused to change by more than a predetermined change rate when the front curvature radius is less than a second threshold value during execution of the fuel economy control, even if the margin driving force crosses the first threshold value, that is, a state where the margin driving force exceeds the first threshold value and a state where the margin driving force is less than the first threshold value repeatedly occur within a predetermined time.

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