Vehicle control devices

Abstract

To provide a vehicle control device that can suppress uneven distribution of brake load on the drive wheels. [Solution] When braking the vehicle 10, if the VSC is in operation and the difference between the left rear brake Brl and the right rear brake Brr that brake the rear wheels 18 (=|Ll-Lr|) of the brake load values ​​Ll and Lr, which indicate the magnitude of the load state, is greater than or equal to a predetermined value LA, and the vehicle is driving straight, the differential limiting clutch C is engaged, and the braking force of the brake with the larger brake load value Ll and Lr is made smaller than the braking force of the brake with the smaller brake load value. As a result, the load on the brake with a large load state is reduced, and the load on the brake with a small load state is increased, and the vehicle 10 is braked, thus suppressing the load imbalance of the rear brakes Br.

Description

Technical Field

[0001] The present invention relates to a vehicle control device that performs skid suppression control for suppressing skidding of a vehicle during turning.

Background Art

[0002] In a vehicle including a drive source and a plurality of brakes that brake wheels for each wheel, there is known a vehicle control device that performs skid suppression control (hereinafter referred to as VSC: Vehicle Stability Control) for suppressing skidding of the vehicle during turning by controlling the drive source and the brakes. For example, the vehicle control device described in Patent Document 1 is an example thereof.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the above-described VSC is operated, in a situation where turning in a specific direction such as circuit running is repeated, the braking opportunity of the brake that brakes the drive wheel on the outer side with respect to the turning direction increases, and a high load is applied. For this reason, there is a bias in the load on the brakes, and there is a risk that brake uneven wear, fade phenomenon, heat sag, etc. may occur on the high load side.

[0005] The present invention has been made based on the above circumstances, and an object thereof is to provide a vehicle control device that can suppress the bias in the load on the brakes of the drive wheels.

Means for Solving the Problems

[0006] The gist of the present invention is a vehicle control device that performs the following actions in a vehicle equipped with (a) a plurality of brakes for braking each wheel, a differential gear device for distributing drive torque transmitted from a drive source to the left and right drive wheels while allowing for their rotational differences, and a differential limiting clutch for limiting the differential between the drive wheels, the control device for a vehicle that controls the brakes and the drive source to suppress skidding of the vehicle during turning, and differential limiting control for engaging the differential limiting clutch when one of the drive wheels slips, (b) When braking the vehicle, if the skid suppression control is in operation, and the difference in brake load values ​​between the left and right drive wheel brakes that brake the drive wheels is greater than or equal to a predetermined value, and the vehicle is traveling in a straight line, the differential limiting clutch is engaged, and the braking force of the drive wheel brake with the larger brake load value is made less than the braking force of the drive wheel brake with the smaller brake load value. [Effects of the Invention]

[0007] According to the present invention, when braking the vehicle, if the skid suppression control is in operation, and the difference in brake load values ​​between the left and right drive wheel brakes that brake the drive wheels is greater than or equal to a predetermined value, and the vehicle is traveling in a straight line, the vehicle control device engages the differential limiting clutch and reduces the braking force of the drive wheel brake with the larger brake load value to less than the braking force of the drive wheel brake with the smaller brake load value. As a result, the load on the drive wheel brake with a large load is reduced, and the load on the drive wheel brake with a small load is increased, thereby braking the vehicle and suppressing the load imbalance of the drive wheel brakes. Consequently, uneven brake wear, fade, and heat-induced performance degradation are prevented, and vehicle swaying during deceleration is also prevented.

[0008] Preferably, the vehicle control device stops the operation of the differential limiting control while the vehicle is being braked by the skid suppression control. This avoids functional interference with the skid suppression control, which would reduce the driving force on the side that is not being braked. [Brief explanation of the drawing]

[0009] [Figure 1] This figure illustrates the main components of a vehicle, including a vehicle control device according to one embodiment of the present invention. [Figure 2] Figure 1 is a flowchart illustrating the key aspects of the control operation of the vehicle control device. [Figure 3] Figure 2 is a schematic diagram illustrating the operating state of the drive wheels during control operation in the flowchart. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Examples]

[0011] Figure 1 is a diagram illustrating the main components of a vehicle 10 to which the present invention is applied, as well as a diagram illustrating the main components of a control system provided in the vehicle 10. The vehicle 10 is a rear-wheel drive vehicle.

[0012] Vehicle 10 comprises a prime mover 12 such as an engine or electric motor, a transmission 14 that changes the rotation speed of the prime mover 12, a pair of left and right front wheels 16 (left front wheel 16L, right front wheel 16R), a pair of left and right front drive shafts 20, a pair of left and right rear wheels 18 (left rear wheel 18L, right rear wheel 18R) which are drive wheels, a pair of left and right rear drive shafts 22, and a differential gear unit 30 connected to the rear wheels 18 via the rear drive shafts 22. In addition, the front wheels 16 and rear wheels 18 of vehicle 10 are provided with multiple brakes B (front wheel brake Bf (left front wheel brake Bfl, right front wheel brake Bfr), rear wheel brake Br (left rear wheel brake Brl, right rear wheel brake Brr)) that brake each wheel. The prime mover 12 corresponds to the "drive source" of the present invention, and the rear wheel brakes Br correspond to the "drive wheel brakes" of the present invention.

[0013] The differential gear unit 30 distributes the drive torque transmitted from the transmission 14 via the propeller shaft 24 to the left rear wheel 18L and the right rear wheel 18R, which are connected via the rear drive shaft 22, while allowing for a difference in rotation between them. The differential gear unit 30 is also equipped with a differential limiting clutch C. The differential gear unit 30 is an electronically controlled so-called LSD (limited slip differential).

[0014] The differential limiting clutch C, by engaging, limits the differential rotation between the rear drive shafts 22 and the drive wheels connected to them, i.e., between the left rear wheel 18L and the right rear wheel 18R. The differential limiting clutch C is configured such that, for example, a plurality of fixed friction plates 34, which are not rotatable, and rotating friction plates 36, which rotate with the drive shafts 22, are stacked alternately on top of each other. Engagement is achieved by applying a pressing load that presses the fixed friction plates 34 and rotating friction plates 36 against each other using an electric actuator or hydraulic actuator (not shown).

[0015] Vehicle 10 is equipped with an electronic control device 60, which includes a so-called microcomputer, as a vehicle control device for controlling various parts of vehicle 10.

[0016] The electronic control device 60 is supplied with various signals (for example, the vehicle speed V of the vehicle 10, the wheel speeds Nwfl and Nwfr of the front wheels 16 (16L, 16R), the wheel speeds Nwrl and Nwrr of the rear wheels 18 (18L, 18R), the brake temperatures Twfl, Twfr, Twrl, Twrr of the brakes B (Bfl, Bfr, Brl, Brr), the steering angle θsw of the steering wheel, the brake operation amount Bop of the brake pedal, the yaw acceleration RyawR which is the rotational angular velocity around the vertical axis of the vehicle 10, the VSC operation setting signal VSCon, etc.) based on the detection values by various sensors etc. (for example, the vehicle speed sensor 70, the wheel speed sensor 72, the brake temperature sensor 74, the steering sensor 76, the brake operation amount sensor 78, the yaw acceleration sensor 80, the VSC setting switch 82, etc.) provided in the vehicle 10.

[0017] From the electronic control device 60, various command signals (for example, the engine control command signal Se for controlling the engine 12, the clutch control command signal Sc for controlling the engagement or release of the differential limiting clutch C, the brake control command signals Sfl, Sfr, Srl, Sr for controlling the braking forces of the left front wheel brake Bfl, the right front wheel brake Bfr, the left rear wheel brake Brl, and the right rear wheel brake Brr, etc.) are respectively output to various devices (for example, the engine 12, the differential limiting clutch C, the brake B, etc.) provided in the vehicle 10.

[0018] The electronic control device 60 functionally includes a VSC control unit 62, a differential limit control unit 64, and a brake control unit 66.

[0019] The VSC control unit 62 performs a skid suppression control (hereinafter referred to as VSC) during turning of the vehicle 10. When the VSC operation setting signal VSCon is supplied according to the setting of the VSC setting switch 82, it enters the VSC operation mode in which VSC operates.

[0020] When the yaw acceleration deviation ΔRyaw (= |RyawT - RyawR|), which is the difference between the target yaw acceleration RyawT obtained from the vehicle speed V and the steering angle θsw and the yaw acceleration RyawR detected by the yaw acceleration sensor 80, is greater than a predetermined deviation Ayaw set in advance, the VSC control unit 62 determines that the vehicle 10 has a tendency to skid.

[0021] When the vehicle 10 has a tendency to skid and the yaw acceleration RyawR > the target yaw acceleration RyawT, the VSC control unit 62 determines that the rear wheels 18 have a tendency to skid, and outputs a braking request to the front and rear wheels on the outside with respect to the turning direction to the brake control unit 66 described later. Also, when the yaw acceleration RyawR < the target yaw acceleration RyawT, the VSC control unit 62 determines that the front wheels 16 have a tendency to skid, outputs a braking request to the rear wheels 18 (left rear wheel 18L and right rear wheel 18R) and the front wheels on the outside with respect to the turning direction to the brake control unit 66, and outputs a prime mover control command signal Se for suppressing the driving force to the prime mover 12. Based on the above-described braking request and the prime mover control command signal Se, the target wheels are braked by the brake control unit 66, and the driving force of the prime mover 12 is suppressed, thereby suppressing the skid of the rear wheels 18 or the front wheels 16.

[0022] When one of the rear wheels 18 spins during the vehicle 10 traveling on an icy road or a muddy road or the like, the differential limit control unit 64 performs differential limit control for engaging the differential limit clutch C to limit the differential rotation of the rear wheels 18 in order to prevent the driving force of the rear wheels 18, which are the driving wheels, from decreasing. The determination of wheel spin is made, for example, by determining whether the difference (= |Nwrl - Nwrr|) between the wheel speed Nwrl of the left rear wheel 18L and the wheel speed Nwrr of the right rear wheel 18R is greater than or equal to a predetermined value ANW set in advance.

[0023] The brake control unit 66 controls the braking force of brake B based on braking requests commanded by other control units (not shown) provided by the VSC control unit 62 and the electronic control unit 60 (such as a braking control unit that responds to the driver's brake operation and an anti-lock braking system). For example, if the brake control unit 66 is commanded to apply a braking request to the left rear wheel 18L, which is a left rear wheel braking force Btl, and a braking request to the right rear wheel 18R, which is a right rear wheel braking force Btr, the brake control unit 66 outputs a brake control command signal Srl to the left rear wheel brake Brl so that the left rear wheel 18L is braked with the left rear wheel braking force Btl, and a brake control command signal Srr to the right rear wheel brake Brr so that the right rear wheel 18R is braked with the right rear wheel braking force Btr.

[0024] Incidentally, when the aforementioned VSC is activated, in situations such as circuit driving where turns in a specific direction are repeated, the braking opportunities for the brake that applies to the outer rear wheel 18 relative to the direction of the turn increase, resulting in a high load. As a result, an imbalance in the load on the rear wheel brake Br may occur, potentially leading to uneven brake wear, brake fade, and heat-related performance degradation on the high-load side.

[0025] Therefore, the electronic control device 60 of this embodiment suppresses the load imbalance of the rear wheel brake Br by the control operation described in Figure 2. Figure 2 is a flowchart illustrating the main part of the control operation of the electronic control device 60, and is a diagram illustrating the operation of braking control to the rear wheel brake Br by the brake control unit 66. This flowchart is executed repeatedly when braking is performed on the vehicle 10, that is, when a braking request command is issued to the brake control unit 66. Figure 3 is a schematic diagram illustrating the operating state of the rear wheels 18 corresponding to the control operation in the flowchart of Figure 2. In Figure 3, for the left rear wheel 18L and the right rear wheel 18R respectively, the black arrows represent the transmitted torques TL and TR transmitted from the differential gear unit 30 via the propeller shaft, the white arrows represent the left rear wheel braking force Btl and the right rear wheel braking force Btr output from the left rear wheel brake Brl and the right rear wheel brake Brr, and the dashed arrows represent the actual driving torques WL and WR that are actually applied to the left rear wheel 18L and the right rear wheel 18R by the aforementioned transmitted torques and braking forces. Hereafter, the control operation of the brake control unit 66 will be explained in accordance with the processing steps in Figure 2, with reference to Figure 3.

[0026] In Figure 2, step S10 (the step will be omitted hereafter) determines whether or not the VSC is in operation mode. If the determination in S10 is negative, differential limit control by the differential limit control unit 64 is permitted in S20. If differential limit control is already permitted, the permitted state continues. Next, in S30, based on the braking request commanded to the brake control unit 66, the left rear brake force Btl and the right rear brake force Btr are output to the left rear brake Brl and right rear brake Brr, respectively, and this routine is terminated.

[0027] Figure 3(a) is a schematic diagram illustrating the operating state of the rear wheels 18 when control operation S30 is executed. The actual drive torques WL and WR are obtained by subtracting the left rear wheel braking force Btl and the right rear wheel braking force Btr from the transmitted torques TL and TR, respectively: WL = TL - Btl and WR = TR - Btr. Braking in this operating state is referred to as normal braking.

[0028] Returning to FIG. 2, if the determination in S10 is affirmative, then next in S40, it is determined whether the braking request is a braking request for the turning of the vehicle 10. This determination is made, for example, by determining whether at least one of (A) the braking request is for implementing VSC and (B) one of the rear wheels 18 is stacked and the driving torque is transferred to the other for stack escape (refer to the text in the box).

[0029] If the determination in S40 is negative, then in S50, it is determined whether there is a bias in the brake load values Ll and Lr indicating the magnitudes of the load states of the left rear wheel brake Brl and the right rear wheel brake Brr, respectively. This determination is made, for example, by determining whether the absolute value of the difference between the brake load values Ll and Lr is greater than or equal to a predetermined value LA (|Ll - Lr| ≥ LA). The brake load values Ll and Lr are calculated by a suitable method based on, for example, the brake temperatures Twrl and Twrr of the left rear wheel brake Brl and the right rear wheel brake Brr, the integration of the braking performance over a predetermined period, or both. Also, a suitable value for the predetermined value LA is set in advance by design or experiment.

[0030] If the determination in S50 is affirmative, that is, if there is a bias in the load on the rear wheel brake Br, then in S60, it is determined whether it is a braking request during straight - ahead driving and whether it is a driving state in which the load on the brake on the high - load side can be reduced. If the determination in S50 or S60 is negative, the process transitions to S20 described above, normal braking is performed, and this routine ends.

[0031] If the determination in S60 is affirmative, then in S70, the distribution calculation of the braking forces (left rear wheel braking force Btl and right rear wheel braking force Btr) of the left rear wheel brake Brl and the right rear wheel brake Brr is performed. This distribution calculation is performed, for example, as follows. Since the braking request commanded to the brake control unit 66 is a braking request during straight - ahead driving, the braking requests for the left rear wheel 18L and the right rear wheel 18R are braking forces Btw of the same magnitude. That is, since the braking request for the entire rear wheel 18 is 2×Btw, the distribution calculation is performed for this braking request for the entire rear wheel 18 (2×Btw) according to the following formula. · When the brake load value Ll < Lr Left rear wheel braking force Btl = (1 - α) × (2 × Btw) ···(1) Right rear wheel braking force Btr = α × (2 × Btw) ···(2) · When the brake load value Ll > Lr Left rear wheel braking force Btl = α × (2 × Btw) Right rear wheel braking force Btr = (1 - α) × (2 × Btw) Here, α is a negative addition reduction coefficient given within the range of 0 ≦ α < 0.5 (50%), which is the braking force of the brake on the side with a larger load value, that is, a coefficient set to reduce the load of the brake. The load reduction coefficient α is calculated, for example, based on the brake load values Ll, Lr, the braking requirement 2 × Btw for the entire rear wheel 18, the vehicle speed V, etc., by a calculation formula or a map that has been appropriately obtained in advance by design or experiment.

[0032] Then, at S80, the differential limit clutch C is engaged, and based on the distribution calculation result at S70, the left rear wheel braking force Btl and the right rear wheel braking force Btr are output to the left rear wheel brake Brl and the right rear wheel brake Brr respectively, and this routine is terminated.

[0033] Figure 3(b) is a schematic diagram for explaining the operating state of the rear wheel 18 when the control operation of S80 is executed and the brake load value Ll < Lr, that is, when the brake load value of the right rear wheel brake Brr (right rear wheel 18R side) is large. The differential limit clutch C is in an engaged state, and the transmission torque and braking force acting on the rear wheel 18 are evenly distributed between the left rear wheel 18L and the right rear wheel 18R. The actual driving torques WL and WR from the transmission torque (let TL = TR = TW) and the left rear wheel braking force Btl and the right rear wheel braking force Btr calculated by equations (1) and (2) are WL = WR = TW - Btw. That is, the braking force on the high-load side (right rear wheel brake Brr), that is, the load is reduced, so the bias of the load of the rear wheel brake Br is suppressed.

[0034] Returning to Figure 2, if the judgment in S40 is affirmed, the differential limit control by the differential limit control unit 64 is stopped in S90, meaning the differential limit clutch C is released. Then, in S100, based on the braking request commanded to the brake control unit 66, the left rear brake force Btl and the right rear brake force Btr are output to the left rear brake Brl and right rear brake Brr, respectively, and this routine is terminated.

[0035] Figure 3(c) is a schematic diagram illustrating the operating state of the rear wheels 18 when control operation S100 is performed and lateral slip suppression of the rear wheels 18 during left turns is performed by VSC. Due to VSC, the braking force of the right rear brake Brr (right rear braking force Btr) is output to the right rear wheel 18R, and the actual driving torque WR of the right rear wheel 18R becomes WR = TR - Btr. On the other hand, the actual driving torque WR of the left rear wheel 18L is shifted by the amount of transmission torque that was braked by the action of the differential gear 30, and becomes WR = TR + Btr. In this way, lateral slip suppression of the rear wheels 18 is performed by VSC.

[0036] Furthermore, Figure 3(d) shows an example where differential limiting control is activated simultaneously with the operation shown in Figure 3(c). In this case, the transmission torque and braking force acting on the rear wheels 18 are equally distributed between the left rear wheel 18L and the right rear wheel 18R. Therefore, similar to the transmission torque (let's assume TL=TR=TW), the braking force of the right rear brake Brr (right rear braking force Btr) is also equally distributed, and the actual driving torques WL and WR become WL=WR=TW-Btr / 2. Consequently, functional interference with VSC occurs, as the driving force of the left rear wheel 18L, which is not the target of braking, is reduced. In this embodiment, functional interference is avoided by stopping the differential limiting control at S90.

[0037] As described above, according to the electronic control device 60 of this embodiment, when braking the vehicle 10, if the VSC is in operation and the difference between the left and right brake load values ​​Ll and Lr (=|Ll-Lr|) indicating the magnitude of the load state is greater than or equal to a predetermined value LA, and furthermore, when driving straight, the differential limiting clutch C is engaged and the braking force of the brake with the larger brake load value Ll and Lr is made smaller than the braking force of the brake with the smaller brake load value. As a result, the load on the brake with a large load state is reduced and the load on the brake with a small load state is increased, and the vehicle 10 is braked, so that the load imbalance of the rear brakes Br is suppressed. Consequently, uneven brake wear, fade, and heat fade are prevented, and the vehicle 10 does not wobble during deceleration.

[0038] Furthermore, according to the electronic control device 60 of this embodiment, the differential limiting control is deactivated during braking by the VSC. This reduces the driving force on the side not being braked, thus avoiding functional interference with the VSC.

[0039] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0040] For example, in the above-described embodiment, the vehicle 10 was a rear-wheel drive vehicle, but the present invention is equally applicable to a front-wheel drive vehicle or a four-wheel drive vehicle.

[0041] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of Symbols]

[0042] 10: Vehicle 12: Engine (Drive source) 18: Rear wheels (Drive wheels) 30: Differential gear system B: Brake Br: Rear wheel brake (Drive wheel brake) 60: Electronic control device (Vehicle control device) Btl: Left rear wheel braking force (Braking force) Btr: Right rear wheel braking force (Braking force) C: Differential limiting clutch LA: Predetermined value Ll, Lr: Brake load value

Claims

[Claim 1] A vehicle control device that controls the brakes and the drive source to suppress skidding of the vehicle during turns, and engages the differential limiting clutch when one of the drive wheels slips, in a vehicle equipped with multiple brakes that brake each wheel individually, a differential gear system that distributes drive torque transmitted from a drive source to the left and right drive wheels while allowing for their rotational differences, and a differential limiting clutch that limits the differential between the drive wheels, wherein the vehicle control device controls the brakes and the drive source to suppress skidding of the vehicle during turns, and engages the differential limiting clutch when one of the drive wheels slips. When braking the vehicle, if the skid suppression control is in operation, and the difference in brake load values ​​between the left and right drive wheel brakes that brake the drive wheels is greater than or equal to a predetermined value, and the vehicle is traveling in a straight line, the differential limiting clutch is engaged, and the braking force of the drive wheel brake with the larger brake load value is reduced to be less than the braking force of the drive wheel brake with the smaller brake load value. A vehicle control device characterized by the following features.

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