Drive force control device

Abstract

A drive force control device according to the present invention is to be installed on a vehicle at which drive force from an engine is transmitted to a drive wheel via a dog-type transmission. A control unit of the drive force control device controls a throttle opening angle in accordance with the rotational speed of the engine and the transmission ratio being selected by the transmission during deceleration of the vehicle by inter-vehicle distance control or relative vehicle speed control such that the throttle opening angle is a target throttle opening angle. The present invention thereby makes it possible to achieve a travel feel that does not make a driver uneasy during deceleration control by inter-vehicle distance control or relative vehicle speed control.

Description

Driving force control device

[0001] The present invention relates to a driving force control device.

[0002] As a driving force control device mounted on a vehicle (for example, a straddle-type vehicle) that transmits the driving force of an engine to driving wheels via a dog-type transmission, there is a device that decelerates the vehicle by setting the throttle opening of the engine to fully closed (idle opening) during deceleration control in inter-vehicle distance control (see, for example, Patent Document 1).

[0003] Japanese Patent No. 6961031

[0004] In the above-described conventional driving force control device, when the gear ratio selected by the transmission is large, the deceleration becomes large, and when the gear ratio selected by the transmission is small, the deceleration becomes small. That is, since the deceleration varies greatly depending on the gear position selected during deceleration control in inter-vehicle distance control, a sense of discomfort may occur in the driver's driving feeling.

[0005] It is an object of the present invention to provide a driving force control device that solves the above-described problems and can provide a driving feeling without discomfort for the driver during deceleration control in inter-vehicle distance control.

[0006] In order to solve the above problems, a first invention is a driving force control device mounted on a vehicle that transmits the driving force of an engine to driving wheels via a dog-type transmission. The driving force control device includes a control unit that controls a throttle opening of the engine, and a storage unit in which a relationship between the rotational speed of the engine and a target throttle opening is stored according to the magnitude of a gear ratio of the transmission. When a deceleration command is output by inter-vehicle distance control or relative vehicle speed control, the control unit refers to the storage unit, and sets the throttle opening to the target throttle opening in accordance with the rotational speed of the engine at any time point from when the deceleration command is output to a time point before the own vehicle starts decelerating, and the gear ratio selected by the transmission, to control the throttle opening.

[0007] To solve the aforementioned problems, the second invention is a drive force control device mounted on a vehicle that transmits engine drive force to drive wheels via a dog-type transmission. The drive force control device comprises a control unit that controls the throttle opening of the engine, and a storage unit that stores the relationship between the engine speed and the target throttle opening according to the magnitude of the gear ratio of the transmission. When the vehicle is decelerating due to inter-vehicle distance control or relative vehicle speed control, the control unit refers to the storage unit and controls the throttle opening to achieve the target throttle opening according to the engine speed during deceleration and the gear ratio selected by the transmission.

[0008] The drive force control device of the present invention can suppress large fluctuations in deceleration for each gear position during deceleration control in inter-vehicle distance control or relative vehicle speed control, thereby providing a driving feel that is natural and comfortable for the driver.

[0009] This is a configuration diagram showing a drive force control device according to an embodiment of the present invention. This is a graph showing the relationship between the target throttle opening and engine speed for each gear ratio in the drive force control device according to an embodiment of the present invention. This is a time chart showing the inter-vehicle distance control by the drive force control device according to an embodiment of the present invention. This is a time chart showing the state of the dog clutch in inter-vehicle distance control by the drive force control device according to an embodiment of the present invention. This is a graph showing the relationship between engine speed and the first, second, and third states in the drive force control device according to an embodiment of the present invention. This is a flowchart showing the inter-vehicle distance control by the drive force control device according to an embodiment of the present invention.

[0010] Embodiments of the present invention will be described in detail with reference to the drawings as appropriate. The drive force control device 1 shown in Figure 1 is mounted on a vehicle that transmits engine drive force to the drive wheels via a dog-type transmission.

[0011] In this embodiment, a drive force control device 1 mounted on a saddle-type vehicle such as a motorcycle or a three-wheeled vehicle will be described as an example. Note that the drive force control device 1 of this embodiment is also applicable to various other vehicles, such as four-wheeled vehicles.

[0012] Vehicles equipped with a dog-type transmission have three states: a first state in which the engine drives the drive wheels via the transmission; a second state in which the drive wheels drive the engine via the transmission; and a third state other than the first and second states (a state between the first and second states, i.e., a state in which the engagement between the dog claw and the dog hole is released).

[0013] The first state, as shown in Figure 4, is when the engine's driving force is transmitted to the drive wheels via the transmission. That is, the dog holes of the drive gear are engaged with the dog pawls of the dog clutch in the direction of rotation of the drive gear.

[0014] The second state is when the drive wheels are driving the engine via the transmission, and engine braking is occurring. In other words, the dog holes of the drive gear are engaged with the dog pawls of the dog clutch in the opposite direction to the rotation of the drive gear.

[0015] The third state is an intermediate state between the first and second states (i.e., the dog pawl and dog hole are disengaged). In the third state, the dog hole of the drive gear is not engaged with the dog pawl of the dog clutch, which is a neutral state, and the engine's driving force is not transmitted to the drive wheels via the transmission, nor does engine braking occur.

[0016] The drive force control device 1 shown in Figure 1 is an electronic control unit such as an ECU (Electronic Control Unit) that performs adaptive cruise control, which automatically controls the vehicle's speed. Adaptive cruise control includes vehicle speed control, which maintains the vehicle speed at a predetermined speed, and distance control, which adjusts the distance to the preceding vehicle. The drive force control device 1 consists of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and the CPU executes programs stored in the storage unit 20, such as the ROM, to perform the work of each part.

[0017] The drive force control device 1 comprises a control unit 10 that controls the throttle opening of the engine (the airflow rate at the throttle valve) and a storage unit 20 that stores various data.

[0018] The memory unit 20 stores data or relational formulas that show the relationship between the target throttle opening and the engine speed. Figure 2 is a graph showing the relationship between the target throttle opening and the engine speed. Multiple relationships between the target throttle opening and the engine speed are stored depending on the gear ratio of the transmission. In Figure 2, the target throttle opening increases as you move upwards on the vertical axis, and the engine speed increases as you move to the right on the horizontal axis.

[0019] In this embodiment, multiple gear ratios (multiple gear positions) are divided into three groups (low gear ratio, medium gear ratio, and high gear ratio), and the relationship between the target throttle opening and engine speed is stored in the memory unit 20 for each of the low, medium, and high gear ratios. The number of selectable gear ratios (number of gears) in a transmission varies, but for example, if there are six stages (six gears), the 1st and 2nd gears can be divided into "low gear ratios," the 3rd and 4th gears into "medium gear ratios," and the 5th and 6th gears into "high gear ratios." Alternatively, multiple gear ratios (multiple gear positions) may be divided into two groups (high gear ratio and low gear ratio), or into four or more groups. Or, without grouping, the relationship between the target throttle opening and engine speed may be defined for each of the multiple gear ratios (gear positions).

[0020] The target throttle opening is defined to change according to the engine speed. In this embodiment, the target throttle opening is defined to include the throttle opening for the first state (the state in which the drive wheels are driven via the transmission), the throttle opening for the second state (the state in which the drive wheels drive the engine via the transmission), and the throttle opening for the third state (a state between the first and second states). Referring to the graph in Figure 2, the third state can be represented by a function that increases as the engine speed increases (hereinafter referred to as the "no-load line"). When the throttle opening is adjusted to a value on the no-load line, the transmission enters the third state. When the throttle opening is adjusted to exceed the throttle opening for the third state (no-load line), it transitions to the first state, and when the throttle opening is adjusted to fall below the throttle opening for the third state (no-load line), it transitions to the second state.

[0021] The engine speed may be divided into three ranges, from the highest to the lowest, and the transmission state should be selected for each range.

[0022] The first rotation range is the engine speed when the vehicle is traveling at high speed. When the vehicle is traveling at high speed, it is expected that the actual distance to the preceding vehicle will reach the target distance early. Therefore, it is desirable to have the drive wheels drive the engine via the transmission and decelerate the vehicle using engine braking. Accordingly, the target throttle opening in the first rotation range should be the throttle opening that results in the second state.

[0023] The second RPM range is the engine speed when the vehicle is traveling at a medium speed. When the vehicle is traveling at a medium speed, it is assumed that the rate at which the actual distance between the vehicle and the vehicle in front decreases will also be gradual. Therefore, it is desirable to drive the drive wheels via the transmission, put the dog clutch in neutral, and decelerate the vehicle by coasting. Accordingly, the target throttle opening in the second RPM range should be the throttle opening that results in the third state.

[0024] The third RPM range represents the engine speed when the vehicle is traveling at low speed. When the vehicle is traveling at low speed, the engine speed is low and engine stalling is expected. Therefore, it is desirable to decelerate the vehicle while driving the drive wheels through the transmission. Accordingly, the target throttle opening in the third RPM range should be the throttle opening that corresponds to the first state.

[0025] The engine speeds that mark the boundaries between the first, second, and third rotational speed ranges may be the same or different for all gear position groups (in this embodiment, high gear ratio, medium gear ratio, and low gear ratio) and gear positions.

[0026] Referring to the graph in Figure 2, an example of engine speeds that mark the boundaries between rotational speed ranges can be explained. When the gear group is set to a "high gear ratio," the target throttle opening is defined as follows: the engine speed at the boundary between the first and second rotational speed ranges is NE1, and the engine speed at the boundary between the second and third rotational speed ranges is NE2, which is lower than NE1. In other words, when the gear ratio is high, the target throttle opening is the "throttle opening for the second state" when the engine speed exceeds NE1, the "throttle opening for the first state" when the engine speed falls below NE2, and the "throttle opening for the third state" when the engine speed is between NE2 and NE1.

[0027] When the gear group is set to a "medium gear ratio," the target throttle opening is defined as the engine speed at the boundary between the first and second rotational speed ranges as NE1, and the engine speed at the boundary between the second and third rotational speed ranges as NE3, which is lower than NE2. In other words, when the gear group is set to a "medium gear ratio," the target throttle opening is the "throttle opening for the second state" when the engine speed exceeds NE1, the "throttle opening for the first state" when the engine speed falls below NE3, and the "throttle opening for the third state" when the engine speed is between NE3 and NE1.

[0028] When the gear group is in a "low gear ratio" configuration, the target throttle opening is defined as the engine speed at the boundary between the first and second rotational speed ranges as NE2, and the engine speed at the boundary between the second and third rotational speed ranges as NE3. In other words, when the gear ratio is low, the target throttle opening is the "throttle opening for the second state" when the engine speed exceeds NE2, the "throttle opening for the first state" when the engine speed falls below NE3, and the "throttle opening for the third state" when the engine speed is between NE3 and NE2.

[0029] The memory unit 20 shown in Figure 1 stores information about the third state (no-load line) and information for setting the target throttle opening based on the third state, as data that defines the relationship between the target throttle opening and the engine speed. The information about the third state is, for example, NLL opening information (information corresponding to the "third state" in Figure 2) that defines the relationship between the engine speed and the throttle opening that constitutes the third state. The information for setting the target throttle opening is, for example, difference information (information corresponding to the difference between the throttle opening of the third state and the throttle opening of each gear ratio in Figure 2) that defines the difference between the third state and the target throttle opening. The NLL opening information and difference information are stored in the memory unit 20 as data (map) with the engine speed as a parameter, for example.

[0030] When a deceleration command is output by the inter-vehicle distance control, the control unit 10 sets a target throttle opening according to the engine speed range and the gear ratio selected by the transmission at any point between the time the deceleration command is output and the time before the vehicle starts to decelerate, and controls the throttle opening to achieve that target throttle opening. Furthermore, when the vehicle is decelerating due to the inter-vehicle distance control, the control unit 10 sets a target throttle opening according to the engine speed range and the gear ratio selected by the transmission acquired during deceleration, and controls the throttle opening to achieve that target throttle opening.

[0031] The control unit 10 receives the engine speed from the rotation speed meter 2. The control unit 10 also receives information regarding the gear ratio selected by the transmission (e.g., gear position) from the gear position sensor 3. The control unit 10 is connected to the throttle drive unit 4, which varies the throttle opening.

[0032] The control unit 10 detects the actual engine speed and information regarding the gear ratio selected by the transmission at a predetermined timing, and calculates the target throttle opening from the data in the storage unit 20 based on the detection results. For example, if the gear ratio selected by the transmission is 1st or 2nd gear, the control unit 10 calculates the target throttle opening corresponding to the "low gear ratio" based on the actual engine speed. Similarly, if the gear ratio is 3rd or 4th gear, the control unit 10 calculates the target throttle opening corresponding to the "medium gear ratio" based on the actual engine speed, and if the gear ratio is 5th or 6th gear, it calculates the target throttle opening corresponding to the "high gear ratio" based on the actual engine speed.

[0033] In this embodiment, the control unit 10, based on the engine speed input from the rotation speed meter 2, refers to information regarding the third state (no-load line) stored in the memory unit 20 (for example, a map showing NLL opening information) and calculates the throttle opening that corresponds to the third state (the throttle opening that becomes the no-load line) corresponding to the engine speed. The control unit 10 also selects a group (high gear ratio, medium gear ratio, and low gear ratio) to which the gear ratio belongs, based on the gear ratio input from the gear position sensor 3, based on the engine speed input from the rotation speed meter 2. Furthermore, the control unit 10 calculates a difference value corresponding to the selected group and the engine speed based on the difference information stored in the memory unit 20 (a map showing the difference between the no-load line and the target throttle opening), and adds the calculated difference value to the "throttle opening that corresponds to the third state corresponding to the engine speed" to calculate the target throttle opening.

[0034] The control unit 10 adjusts the throttle opening to achieve the target throttle opening for the second state when the engine speed is in the first rotation range (see Figure 5). The control unit 10 also adjusts the throttle opening to achieve the target throttle opening for the third state when the engine speed is in the second rotation range (see Figure 5). The control unit 10 also adjusts the throttle opening to achieve the target throttle opening for the first state when the engine speed is in the third rotation range (see Figure 5). The control for adjusting the throttle opening can be either feedback control or feedforward control, but when the engine speed is in the first and second rotation ranges, it is desirable to adjust the throttle opening using feedforward control because it is desirable to quickly decelerate the vehicle so that the distance to the preceding vehicle does not fall below the target distance.

[0035] Next, the deceleration control of the drive force control device 1 during inter-vehicle distance control will be described. In the following description, the timetables in Figures 3 and 4 and the flowchart in Figure 6 will be referred to as appropriate. In the process of step S1, the control unit 10 determines whether or not deceleration control is performed in inter-vehicle distance control. If it is determined that deceleration control is performed (YES in step S1), the process proceeds to step S2.

[0036] In step S2, the control unit 10 acquires the actual engine speed detected by the rotation speed measuring instrument 2. When a deceleration command is output for the first time by the inter-vehicle distance control, the control unit 10 acquires the engine speed at any point between the time the deceleration command is output and the time before the vehicle starts to decelerate. Also, when the vehicle is decelerating due to the inter-vehicle distance control, the control unit 10 acquires the engine speed during deceleration.

[0037] In step S3, the control unit 10 acquires the gear position detected by the gear position sensor 3 and determines the gear ratio selected by the transmission. Based on the determined gear ratio, the control unit 10 selects the group to which that gear ratio belongs (high gear ratio, medium gear ratio, and low gear ratio). When a deceleration command is first output by the inter-vehicle distance control, the control unit 10 acquires gear ratio information (such as gear position) at any point between the time the deceleration command is output and the time before the vehicle begins to decelerate. Furthermore, when the vehicle is decelerating due to the inter-vehicle distance control, the control unit 10 acquires gear ratio information during deceleration.

[0038] In step S4, the control unit 10 calculates the throttle opening degree that results in the third state (throttle opening degree on the no-load line) based on the NLL opening degree information stored in the storage unit 20, according to the actual engine speed.

[0039] Next, in the process of step S5, the control unit 10 calculates a difference value corresponding to the gear ratio (in this embodiment, the group of gear ratios) and the engine speed based on the difference information (a map showing the difference value between the third state and the target throttle opening) corresponding to the group to which the gear ratio belongs (high gear ratio, medium gear ratio, and low gear ratio).

[0040] Furthermore, in the process of step S6, the control unit 10 adds the difference value calculated in step S5 to the throttle opening of the third state calculated in step S4 to calculate the target throttle opening.

[0041] Subsequently, in the process of step S7, the control unit 10 obtains the actual throttle opening and calculates the difference between the target throttle opening calculated in step S6 and the actual throttle opening. If the value obtained by subtracting the target throttle opening from the actual throttle opening is less than a predetermined threshold (for example, 1 degree) (Yes in step S7), the process proceeds to step S8; otherwise, it is greater than or equal to the threshold (No in step S7), the process proceeds to step S9.

[0042] When the process proceeds to step S8, the control unit 10 sets the target throttle opening calculated in step S6 as the final target throttle opening, and executes control on the throttle. When the process proceeds to step S9, the control unit 10 sets the throttle opening obtained by subtracting a predetermined value (e.g., 1 deg) from the actual throttle opening as the final target throttle opening, and executes control on the throttle.

[0043] Next, an example of the operation of the driving force control apparatus 1 during inter-vehicle distance control will be described with reference to Figs. 3 and 5. In Fig. 5, the target throttle opening increases toward the upper side of the vertical axis, and the engine speed increases toward the right side of the horizontal axis. When a preceding vehicle is recognized in front of the host vehicle during vehicle speed control (control for maintaining the vehicle speed at a constant speed) in adaptive cruise control, the control unit 10 shifts to inter-vehicle distance control. Here, a case is assumed where, at time t1, the control shifts to inter-vehicle distance control from a state where the vehicle is traveling at a constant high speed (state "A" in Fig. 5) with the engine speed in a high rotation range (first rotation range).

[0044] Then, the control unit 10 calculates the target throttle opening according to the flow of Fig. 6, and controls the throttle to reach the target throttle opening. When a deceleration command is output for the first time by inter-vehicle distance control, a map corresponding to the "high reduction ratio" is selected, and for example, the target throttle opening corresponding to the engine speed at the time when the deceleration command is output is set (state "B" in Fig. 5). Here, the target throttle opening that brings about the second state is set, and the throttle driving unit 4 is driven to control the throttle opening so that the throttle opening reaches the target throttle opening. Accordingly, engine braking is generated to decelerate the vehicle, and since the throttle opening is adjusted according to the gear ratio selected by the transmission, variation in deceleration is less likely to occur compared with control that uniformly reduces the throttle opening without considering the gear ratio (e.g., control that sets the throttle opening to an idle opening without considering the gear ratio).

[0045] The control unit 10 continues to calculate the target throttle opening according to the flow in Figure 6 and controls the throttle to reach the target throttle opening. However, since the vehicle is decelerating, it acquires information on the engine speed and gear ratio during deceleration and calculates the target throttle opening each time. In Figures 5 "B" to "C", the target throttle opening is also calculated based on the map corresponding to "high reduction ratio". When the vehicle decelerates due to engine braking and the engine speed drops to the second rotation range (t2 in Figure 2), the target throttle opening for the third state is calculated. When the throttle drive unit 4 is driven at the target throttle opening for the third state and the throttle opening is controlled, the vehicle decelerates slightly while coasting (t2 to t3 in Figure 3, and "C" to "D" in Figure 5). By setting the target throttle opening for the third state, it is possible to reach the target inter-vehicle distance with the actual inter-vehicle distance while suppressing vehicle behavior associated with the switching of the dog clutch engagement state.

[0046] As the vehicle further decelerates due to coasting and the engine speed drops to the third RPM range, the target throttle opening for the first state is calculated. By driving the throttle drive unit 4 at the target throttle opening for the first state and controlling the throttle opening, the vehicle decelerates gradually (from "D" to "E" in Figure 5). Furthermore, by setting the target throttle opening for the third state so that the engine drive torque < driving load, deceleration can be achieved while suppressing engine stalling.

[0047] Subsequently, the control unit 10 executes a control to increase the throttle opening (a control to increase the engine speed), and when the vehicle's speed reaches the speed required for follow control in the inter-vehicle distance control ("F" in Figure 5), the control unit 10 terminates the deceleration control and switches to follow control.

[0048] In the driving force control apparatus 1 configured as described above, since the target throttle opening degree is set for each gear ratio of the transmission during deceleration control in inter-vehicle distance control, it is possible to suppress significant fluctuations in deceleration for each gear position. This stabilizes the vehicle and enables deceleration at an accurate distance. Furthermore, when switching the dog clutch from the second state where engine braking is generated to the first state where the vehicle is accelerated, interposing the neutral third state of the dog clutch between the two states can mitigate the shock generated when switching the dog clutch. Therefore, in the driving force control apparatus 1 according to the present embodiment, during deceleration control in inter-vehicle distance control, it is possible to suppress disturbance of the driver's riding posture and obtain a driving feeling that does not give a sense of discomfort to the driver.

[0049] The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and can be appropriately modified without departing from the spirit of the present invention. In the present embodiment, the vehicle is decelerated to the follow-up control speed by one cycle of the first state, the second state, and the third state. However, when there is a large difference between the vehicle speed at the time of starting deceleration control and the follow-up control speed, the speed may be gradually decreased by repeating the cycle of the first state, the second state, and the third state.

[0050] In the present embodiment, the control of the throttle opening degree by the driving force control apparatus 1 when a deceleration command is output through inter-vehicle distance control is described. However, the driving force control apparatus of the present invention can also be applied to control of the throttle opening degree when a deceleration command is output through relative vehicle speed control.

[0051] 1 Driving force control apparatus 2 Rotation speed measuring device 3 Gear position sensor 4 Throttle drive unit 10 Control unit 20 Storage unit

Claims

1. A drive force control device mounted on a vehicle that transmits engine driving force to drive wheels via a dog-type transmission, comprising: a control unit that controls the throttle opening of the engine; and a storage unit that stores the relationship between the engine speed and the target throttle opening according to the magnitude of the gear ratio of the transmission, wherein when a deceleration command is output by inter-vehicle distance control or relative vehicle speed control, the control unit refers to the storage unit and controls the throttle opening to the target throttle opening according to the engine speed at any point from the time the deceleration command is output to the time before the vehicle starts to decelerate, and the gear ratio selected by the transmission.

2. A drive force control device mounted on a vehicle that transmits engine drive force to drive wheels via a dog-type transmission, comprising: a control unit that controls the throttle opening of the engine; and a storage unit that stores the relationship between the engine speed and the target throttle opening according to the magnitude of the gear ratio of the transmission, wherein when the vehicle is decelerating due to inter-vehicle distance control or relative vehicle speed control, the control unit refers to the storage unit and controls the throttle opening to achieve the target throttle opening according to the engine speed during deceleration and the gear ratio selected by the transmission.

3. A drive force control device according to claim 1 or claim 2, characterized in that the target throttle opening is defined to include a throttle opening that results in a first state in which the drive wheels are driven via the transmission, a throttle opening that results in a second state in which the drive wheels are driven by the engine's drive unit via the transmission, and a throttle opening that results in a third state between the first state and the second state.

4. A drive force control device according to claim 3, wherein the control unit controls the throttle opening when the engine speed is in a preset first rotation range, with the throttle opening that results in the second state set as the target throttle opening.

5. A drive force control device according to claim 3, wherein the control unit controls the throttle opening when the engine speed is in a preset second rotation range, using the throttle opening that results in the third state as the target throttle opening.

6. A drive force control device according to claim 3, wherein the control unit controls the throttle opening when the engine speed is in a preset third rotation range, using the throttle opening that results in the first state as the target throttle opening.

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