Downhill traveling speed control device and vehicle having the downhill traveling speed control device

Abstract

To provide a downhill running speed control device which enables suppression of a deviation between a vehicle speed desired by a driver and an actual vehicle speed.SOLUTION: A downhill running speed control device includes target vehicle speed change means (23) that changes a target vehicle speed (V*) according to acceleration operation or braking operation, while automatic braking is applied to a vehicle during downhill running on the basis of the target vehicle speed (V*). The downhill running speed control device is equipped with road surface gradient detection means (21) detecting a road surface gradient of a downhill road. When the road surface gradient detection means (21) detects a first road surface gradient (θ1) in a state that acceleration operation and braking operation are not performed, the target vehicle speed (V*) is set to be a first vehicle speed (V1) that is a vehicle speed upon detection of the first road surface gradient (θ1) .SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a downhill road speed control device that automatically brakes a vehicle traveling downhill, particularly a vehicle approaching a downhill road, based on a target vehicle speed. [Background technology]

[0002] Patent Document 1 discloses an invention relating to a vehicle speed control method that automatically brakes a vehicle based on a target vehicle speed and adjusts the target vehicle speed in response to operation of the brake pedal or accelerator pedal. [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-1792 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0003] According to the invention described in Patent Document 1, the target vehicle speed is adjusted in response to the operation of the brake pedal or the accelerator pedal, so that the vehicle speed can be controlled in accordance with the driver's intention. However, if the driver starts to travel downhill without operating the brake pedal or accelerator pedal, the target vehicle speed is not adjusted in accordance with the operation of the brake pedal or accelerator pedal, which may cause the driver to feel fearful of speeding. It is also possible to consider a control system that limits the target vehicle speed to a predetermined value (for example, 3 km / h) when the gradient of a downhill road is detected, even if the driver does not operate the brake pedal or accelerator pedal. However, if the vehicle speed is suddenly decelerated to the predetermined target vehicle speed, the driver may feel uncomfortable due to the sudden deceleration of the vehicle immediately after entering a downhill road.

[0004] The present invention has been made in light of the above-mentioned problems, and its object is to provide a downhill road traveling speed control device that can suppress the deviation between the vehicle speed desired by the driver and the actual vehicle speed. [Means for solving the problem]

[0005] In order to achieve the above object, the downhill road traveling speed control device of the present invention is a downhill road traveling speed control device having a target vehicle speed changing means for automatically braking a vehicle traveling on a downhill road based on a target vehicle speed and changing the target speed in response to accelerator operation or brake operation, and further comprising a road surface gradient detection means for detecting the road surface gradient of the downhill road. ,before When the accelerator and brake pedals are not operated, The road surface gradient is calculated from the longitudinal acceleration, and the road surface gradient of the downhill road is When a first road surface gradient is detected, the target vehicle speed is set to a first vehicle speed, which is the vehicle speed when the first road surface gradient is detected; when the brake is operated after the target vehicle speed is set to the first vehicle speed, the target vehicle speed is set to a second vehicle speed, which is the vehicle speed when the brake operation is released; and when the accelerator is operated after the target speed is set to the first vehicle speed, the target speed is set to a third vehicle speed, which is the vehicle speed when the accelerator operation is released. [Effects of the Invention]

[0006] In this invention, even when the vehicle approaches a downhill road without operating the accelerator or brake, if a predetermined road gradient is detected, the target vehicle speed is set to the vehicle speed at the time the predetermined road gradient was detected, thereby realizing deceleration of the vehicle according to the road gradient. Furthermore, compared to when the target vehicle speed is set to a predetermined value when a predetermined road gradient is detected, smoother deceleration of the vehicle can be realized without causing discomfort to the driver. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a control block diagram showing a downhill road traveling speed control device according to a first embodiment. [Figure 2] 4 is a flowchart showing a flow of a target vehicle speed calculation control process executed by a target vehicle speed calculation unit 23 in the first embodiment. [Figure 3] 10 is a time chart showing the vehicle speed when the driver performs braking and accelerator operations in sequence during HDC operation. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, one embodiment of the present invention will be described based on Example 1. [Example]

[0009] 1 is a control block diagram showing a downhill road traveling speed control device of Example 1. In the following description, FL represents the left front wheel, FR represents the right front wheel, RL represents the left rear wheel, and RR represents the right rear wheel. The downhill road traveling speed control device A of the first embodiment performs hill descent control (hereinafter referred to as HDC) that keeps the vehicle at a target vehicle speed on a steep downhill road (for example, 10% or more) without operating the brake or accelerator.

[0010] The downhill road speed control device includes an HDC controller (downhill road speed control means) 1, a brake controller 2, an engine controller 3, a hydraulic control unit (hereinafter referred to as HU) 4, wheel cylinders 5FL, 5FR, 5RL, and 5RR, an engine 6, an acceleration sensor (hereinafter referred to as G sensor) 7, a wheel speed sensor 8, an accelerator opening sensor 9, a brake pedal stroke sensor 10, and a hill descent control switch (hereinafter referred to as HDCSW) 11.

[0011] First, each sensor that sends information to the HDC controller 1 will be described. The G sensor 7 detects the acceleration Gx of the vehicle in the longitudinal direction. Wheel speed sensors 8 are provided on the wheels (not shown) to detect wheel speeds VFL, VFR, VRL, and VRR, which are the rotational speeds of the wheels. The accelerator opening sensor 9 detects the opening of an accelerator pedal (not shown) in, for example, nine stages (0 / 8 to 8 / 8). The brake pedal stroke sensor 10 detects the stroke of a brake pedal (not shown). The HDCSW11 is a switch that allows the driver to activate (ON) or deactivate (OFF) the HDC function at will. When it is ON, it outputs an HDC request signal RQ_HDC=1, and when it is OFF, it outputs an HDC request signal RQ_HDC=0.

[0012] Next, the HDC controller 1 will be described. The HDC controller 1 is a microcomputer or the like, and includes an input processing unit 21, a vehicle state detection unit 22, a target vehicle speed calculation unit (target vehicle speed changing means) 23, and a control amount calculation unit 25 as functions (programs).

[0013] An input processing unit (road surface gradient detection means) 21 calculates a road surface gradient (slope) θ from the longitudinal acceleration Gx detected by the G sensor 7. Also, it calculates a vehicle speed (vehicle body speed) V and a change in vehicle speed V per unit time (amount of speed change) ΔV from wheel speeds VFL, VFR, VRL, and VRR (Vin) from wheel speed sensor 8. In the first embodiment, the vehicle speed V is determined by selecting high for each of the wheel speeds VFL, VFR, VRL, and VRR. Here, the unit time is the minimum time that the input processing unit 21 can process according to the program.

[0014] The vehicle state detection unit 22 receives the road surface gradient θ, the vehicle speed V, and the speed change amount ΔV to determine whether the vehicle is traveling on a downhill road, and outputs a downhill determination flag Slope according to the determination result. If the absolute value of the road surface gradient θ is equal to or greater than a fixed parameter (a downhill road determination angle threshold), the vehicle state detection unit 22 determines that the vehicle is traveling on a downhill road and outputs a downhill determination flag Slope=1. Here, the fixed parameter is typically the road surface gradient at a stage before the driver begins to feel the need to apply the brakes, and is, for example, 2%. If the road surface gradient θ remains equal to or greater than the fixed parameter for a predetermined period of time, the vehicle may be determined to be traveling on a downhill road. When the vehicle state detection unit 22 determines that the vehicle is not traveling on a downhill road, it outputs a downhill determination flag Slope=0.

[0015] The target vehicle speed calculation unit 23 calculates the target vehicle speed V for HDC control based on the accelerator opening APO detected by the accelerator opening sensor 9, the brake pedal stroke amount BLS detected by the brake pedal stroke sensor 10, the vehicle speed V, and a signal from the vehicle state detection unit 22. * Here, the target vehicle speed V * When there are no signals from the accelerator opening sensor and the brake pedal stroke sensor, and when a signal of the downhill judgment flag Slope=1 is received from the vehicle state detection unit 22, the target vehicle speed is set to the vehicle speed at the time of receiving the signal. If the driver subsequently operates the brake and accelerator, the target vehicle speed is changed accordingly.

[0016] For example, if the driver applies the brakes during HDC control, the vehicle decelerates according to the brake operation amount (brake pedal stroke amount), and when the driver releases the brakes (brake pedal stroke amount = 0), the second vehicle speed V2 at the time of release becomes the target vehicle speed V * Alternatively, the target vehicle speed V is set to the vehicle speed when the brake operation is released or the vehicle speed one control cycle before, whichever is smaller. * It may be set to. In addition, when the driver operates the accelerator during HDC control, the vehicle accelerates according to the accelerator operation amount (accelerator opening), and when the driver releases the accelerator (accelerator opening = 0), the third vehicle speed V3 at the time of release is set to the target vehicle speed V * Alternatively, the target vehicle speed V is set to the vehicle speed when the accelerator pedal is released or the vehicle speed one control cycle before, whichever is greater. * It may be set to.

[0017] When the signal received from the HDCSW is RQ_HDC=1, which is a signal for activating the HDC function, the control amount calculation unit 25 calculates the target vehicle speed V set by the target vehicle speed calculation unit 23. *The torque reduction amount of the engine 6 and the pressure increase amount of each wheel cylinder 5FL, 5FR, 5RL, and 5RR are calculated so as to eliminate the deviation between the vehicle speed V and the vehicle speed V, and a braking request (CTR_RQ) is output to the HU 4, and a torque reduction request (TRQ_RQ) is output to the engine controller 3.

[0018] The brake controller 2 outputs a braking command (CTR_INST) corresponding to a braking request to the HU 4 to increase the hydraulic pressure in each of the wheel cylinders 5FL, 5FR, 5RL, and 5RR, thereby applying a braking force to each wheel. The engine controller 3 outputs a torque reduction command (TRQ_INST) corresponding to the torque reduction request to the engine 6, causing the engine 6 to reduce its torque.

[0019] [Target vehicle speed calculation control processing] FIG. 2 is a flowchart showing the flow of the target vehicle speed calculation control process executed by the target vehicle speed calculation unit 23 in the first embodiment, and each step will be described below. This control process is repeatedly executed at a predetermined cycle. The set target vehicle speed is reset when the HDC starts operating. The set target vehicle speed is also reset when the vehicle detects that the road gradient is equal to or less than a predetermined gradient.

[0020] In step S1, it is determined whether the signal received from the HDCSW 11 is RQ_HDC=1. In other words, it is determined whether the HDCSW is ON. If YES, the process proceeds to step S2, and if NO, the process is repeated.

[0021] In step S2, it is determined whether a predetermined value is detected from the brake pedal stroke sensor. In other words, it is determined whether the driver is applying the brakes. If the result is YES, the process proceeds to step S3, and if the result is NO, the process proceeds to step S4.

[0022] In step S3, after the brake operation by the driver is detected in step S2, the second vehicle speed V2 when the brake operation is released (i.e., BLS=0) is detected is set to the target vehicle speed V *After setting the target vehicle speed V * The target vehicle speed V is the smaller of the vehicle speed when BLS=0 is detected and the vehicle speed one control cycle before. * Furthermore, the detection of BLS=0 may be performed when the input signal from the brake pedal stroke sensor 10 disappears, or when BPS>0 is no longer detected after BPS>0 is detected in step S2.

[0023] In step S4, it is determined whether a predetermined value is detected from the accelerator opening sensor. In other words, it is determined whether the driver is operating the accelerator. If the answer is YES, the process proceeds to step S5, and if the answer is NO, the process proceeds to step S6.

[0024] In step S5, after the accelerator operation by the driver is detected in step S4, the third vehicle speed V3 when the accelerator operation is released (i.e., APS=0) is detected is set to the target vehicle speed V * After setting the target vehicle speed V * The target vehicle speed V is the vehicle speed when APS=0 is detected or the vehicle speed one control cycle before, whichever is larger. * Furthermore, ALS=0 may be detected when there is no input signal from the accelerator opening sensor 9, or when APS>0 is no longer detected after BPS>0 is detected in step S4.

[0025] In step S6, it is determined whether the road surface gradient θ is equal to or greater than the first road surface gradient θ1. Here, the first road surface gradient θ1 may be set to a gradient of 3%. If the answer is YES, the process proceeds to S7, and if the answer is NO, the process is restarted from the beginning. That is, if the answers are NO in steps S2, S4, and S6, the determination continues until the answer in any of the steps becomes YES.

[0026] In step S7, the vehicle speed V1 when the first road surface gradient θ1 is detected is set to the target vehicle speed V * After setting it as , the process goes to return. In other words, after the HDC starts operating, if a predetermined first road surface gradient θ1 is detected in a state where the driver's brake operation is not detected in step S2 and the driver's accelerator operation is not detected in step S4, the vehicle speed V1 at the time when the first road surface gradient θ1 is detected is set as the target vehicle speed V * Thereafter, unless the brake or accelerator is operated, the vehicle speed is limited to V1. [Target vehicle speed change effect]

[0027] FIG. 3 is a time chart showing the vehicle speed when a predetermined road gradient is detected after the vehicle enters a downhill road after HDC activation, and the driver then applies the brakes and accelerator pedals in sequence. The following explanation assumes that the HDCSW is ON. For simplicity of explanation, when the driver does not apply the brakes or accelerator pedals, the vehicle speed V is equal to the target vehicle speed V. * shall be deemed to be consistent with

[0028] In the section up to time t0, the driver does not perform braking or accelerating operation, so Step S2 → Step S4 → Step S6 → Step S2 are repeated until the first road surface gradient θ1 is detected. * is not set to a specific value, and the vehicle continues to accelerate due to its own weight until time t0.

[0029] At time t0, a first road surface gradient θ1 (for example, 3%) is detected, so that the target vehicle speed V * is set to the vehicle speed V1 when the first road surface gradient θ1 was detected, and the vehicle speed is maintained at V1. At this time, in the flowchart of FIG. 2, the process proceeds in the order of step S2 → step S4 → step S6 → step S7.

[0030] At time t1, the driver starts to depress the brake pedal, and in the section from time t1 to time t2, the vehicle speed V gradually decreases from V1. At this time, in the flowchart of FIG. 2, the process proceeds from step S2 to step S3.

[0031] At time t2, the driver releases the brake pedal, so in the flowchart of FIG. 2, the process proceeds from step S2 to step S3, and the second vehicle speed V2 at time t2 when the driver releases the brake pedal is set to the target vehicle speed V * In other words, the driver sets the current target vehicle speed V * If you want to drive slower than the target vehicle speed V, you can apply the brakes to * Alternatively, the target vehicle speed V can be set to the smaller of the vehicle speed one control cycle before, that is, the vehicle speed immediately before time t2, or the vehicle speed at time t2 when the driver releases the brake pedal. * It is also possible to do so.

[0032] At time t3, the driver starts to depress the accelerator pedal, and in the section from time t3 to time t4, the vehicle speed V gradually increases from V2. At this time, in the flowchart of FIG. 2, the process proceeds from step S2 to step S4 to step S5.

[0033] At time t4, the driver stops depressing the accelerator pedal, and in the section from time t4 to time t5, the accelerator pedal is released. At this time, in the flowchart of FIG. 2, the flow proceeds from step S4 to step S5, and the third vehicle speed V3 at time t5 when the driver releases the accelerator pedal is set to the target vehicle speed V * Alternatively, the target vehicle speed V is set to the larger of the vehicle speed one control cycle before, i.e., immediately before time t5, and the vehicle speed at time t5 when the driver releases the accelerator pedal. * It is also possible to do so.

[0034] Next, the effects will be described. The downhill road traveling speed control device of the first embodiment provides the following effects.

[0035] The downhill road traveling speed control device has a target vehicle speed changing means that automatically brakes a vehicle traveling downhill based on a target vehicle speed, and changes the target vehicle speed in response to accelerator or brake operation, and is also equipped with a road surface gradient detection means that detects the road surface gradient of a downhill road, and when the road surface gradient detection means detects a first road surface gradient while the accelerator and brake are not being operated, the target vehicle speed is set to a first vehicle speed that is the vehicle speed when the first road surface gradient is detected. Therefore, when the vehicle approaches a downhill road without operating the accelerator or the brake, automatic braking of the vehicle can be performed without giving the driver any discomfort.

[0036] Furthermore, if the brake operation is performed after the target vehicle speed is set to the first vehicle speed, the target vehicle speed is set to the second vehicle speed, which is the vehicle speed when the brake operation is released. Therefore, even after the target vehicle speed has been set to the first vehicle speed, the vehicle can be decelerated to a speed corresponding to the amount of brake operation by the driver and then maintained at the second vehicle speed, which is the vehicle speed when the brake operation is released.

[0037] Furthermore, if the accelerator pedal is operated after the target vehicle speed is set to the first vehicle speed, the target vehicle speed is set to a third vehicle speed, which is the vehicle speed when the accelerator pedal operation is released. Therefore, even after the target vehicle speed is set to the first vehicle speed, the vehicle can accelerate to a speed corresponding to the accelerator pedal operation amount by the driver and then maintain the third vehicle speed, which is the vehicle speed when the accelerator pedal operation is released.

[0038] (Other Examples) The best mode for carrying out the present invention has been described above using Example 1 based on the drawings. However, the specific configuration of the present invention is not limited to that shown in Example 1, and design changes that do not change the gist of the invention are also included in the present invention.

[0039] For example, methods of automatic braking are not limited to engine torque reduction and hydraulic braking, but may also include any one or a combination of hydraulic braking, regenerative braking (if an electric motor is used in the drive system), changing the gear ratio of the drive system, etc.

[0040] In addition, although the example in which the road gradient is detected using a G sensor has been described, this is not limiting, and the road gradient may be corrected by further differentiating the amount of change per unit time of the wheel speed sensor and calculating the acceleration acting on the vehicle. This allows for more accurate detection of the road gradient when traveling downhill. [Explanation of symbols]

[0041] 1 HDC controller, 2 brake controller, 3 engine controller, 5FL to 5RR wheel cylinders, 6 engine, 7 G sensor, 8 wheel speed sensor, 9 accelerator opening sensor, 10 brake pedal stroke sensor, 21 input processing unit, 22 vehicle state detection unit, 23 target vehicle speed calculation unit, 25 control amount calculation unit.

Claims

1. 1. A downhill road traveling speed control device having a target vehicle speed changing means for automatically braking a vehicle traveling on a downhill road based on a target vehicle speed and changing the target speed in response to an accelerator operation or a brake operation, a road surface gradient detection means for detecting a road surface gradient of a downhill road; a road gradient is calculated from a longitudinal acceleration when neither the accelerator pedal nor the brake pedal is operated, and when a first road gradient is detected as the road gradient of the downhill road, the target vehicle speed is set to a first vehicle speed which is the vehicle speed when the first road gradient is detected; When the brake operation is performed after the target vehicle speed is set to the first vehicle speed, the target vehicle speed is set to a second vehicle speed which is the vehicle speed when the brake operation is released, When the accelerator pedal is operated after the target speed is set to the first vehicle speed, the target speed is set to a third vehicle speed, which is the vehicle speed when the accelerator pedal operation is released. A downhill road traveling speed control device characterized by the above.

2. A downhill road traveling speed control device according to claim 1; A hill descent control switch is provided for operating the downhill speed control device. vehicle.

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