JP2007112157A - Control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the comfortableness of a vehicle equipped with a braking system including a hydraulically controlled driving system. <P>SOLUTION: ECU 100 of this vehicle 10 starts the vehicle speed maintaining control using a brake actuator 200 when the prescribed executing conditions are met. During the vehicle speed maintaining control, an incremental/decremental control is made for the target differential pressure Pt of a differential valve 205 in the brake actuator 200 on the basis of the result from comparing the vehicle speed with its target value. The target differential pressure Pt corresponds to the braking pressure for applying brakes to the vehicle 10, as a result, taking a value in accordance with the gradient of the slope on which the vehicle 10 is going to run down. Accordingly if the condition continues in which the target differential pressure Pt lies below the reference differential pressure Pend, the ECU 100 ends the vehicle speed maintaining control upon judging that the vehicle speed maintaining control can be ended safety, as the slope not having the degree such as to require the vehicle speed maintaining control. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technical field of a vehicle control apparatus that controls a vehicle including braking means.

  As this type of device, a device that maintains the vehicle speed below the target vehicle speed has been proposed (see, for example, Patent Document 1). According to the wheel vehicle disclosed in Patent Document 1 (hereinafter referred to as “conventional technology”), the electronic control unit increases the braking force according to the value at which the detected vehicle speed exceeds or falls below the threshold value, respectively. Alternatively, since the hydraulic braking control device is controlled so as to decrease, the detected vehicle speed can be maintained below a threshold value.

Japanese National Patent Publication No. 10-507145

  Such control for maintaining the vehicle speed ends when the vehicle speed reaches a determination value that is sufficiently smaller than the target vehicle speed. However, as the control ends, the hydraulic pressure of the brake fluid in the braking means is suddenly released. The vehicle may re-accelerate depending on the slope of the slope. On the other hand, if such a determination value is not set appropriately, control may be continued even at a gentle gradient that does not require control for maintaining the vehicle speed, and the braking means may be overused. That is, the conventional technique has a technical problem that it is difficult to end the control for maintaining the vehicle speed efficiently and effectively.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a vehicle control device capable of effectively and effectively ending the control for maintaining the vehicle speed.

  In order to solve the above-described problems, a vehicle control apparatus according to the present invention is a vehicle control apparatus that controls a vehicle including a braking unit that applies a braking force according to a hydraulic pressure of a brake fluid to wheels. A first control means for executing vehicle speed maintenance control for controlling the braking means so that a speed when the vehicle descends the slope is maintained below a predetermined value in response to a predetermined input; and the braking means And a second control means for ending the vehicle speed maintenance control based on the specified hydraulic pressure. The specifying means for specifying the hydraulic pressure corresponding to the braking force is provided.

  The “braking means” in the present invention refers to a mechanism, device, system, or the like configured to brake a vehicle by applying a braking force corresponding to the hydraulic pressure of the braking fluid to each wheel to be braked. It is a comprehensive concept. Therefore, the braking means preferably includes a hydraulic pressure control drive system. The hydraulic pressure control drive system is a concept that encompasses a mechanism, a device, or a system that transmits hydraulic pressure and that is driven to variably control the hydraulic pressure by a control unit that will be described later, and is called, for example, a brake actuator. Take the form. However, the mode of the braking means according to the present invention is not limited to the presence or absence of such a hydraulic pressure control drive system, and the braking means determines the braking fluid pressure that defines the braking force by the control means based on the driver's braking intention. There is no limitation as long as it can be controlled independently of (for example, depression of a brake pedal).

  The hydraulic pressure control drive system is preferably applied to each wheel for the purpose of independently controlling the hydraulic pressure of the brake fluid corresponding to each wheel (hereinafter referred to as “braking pressure” as appropriate). In many cases, the corresponding hydraulic pressure transmission path includes a pressure increase path and a pressure reduction path, and each path includes an electromagnetic on-off valve (for example, a solenoid valve). In this case, the braking pressure corresponding to each wheel is appropriately controlled by controlling the driving mode such as the open / close state of the electromagnetic on-off valve and the output of a circulation means (for example, a pump) for supplying the brake fluid to the hydraulic pressure transmission path. Are controlled independently of each other.

  According to the vehicle control apparatus of the present invention, during the operation, the vehicle speed maintenance control is executed by the first control means. Vehicle speed maintenance control refers to control performed on the braking means to maintain the speed at which the vehicle descends the slope (hereinafter referred to as “vehicle speed” as appropriate) below a predetermined value. Note that the “slope” is a concept that includes a road surface having a slope that allows the vehicle to start or continue downhill when at least no braking force is applied to the wheels. In other words, it refers to a road surface that can maintain a non-zero vehicle speed by controlling the braking force applied to each wheel.

  The vehicle speed maintenance control is executed according to a predetermined input. Here, the “predetermined input” may be generated in accordance with, for example, operation of an operation button, an operation lever, or an operation dial by an occupant. Such an operation may be defined as a combination of a plurality of operations. For example, there is a shift position corresponding to a relatively large gear ratio (for example, “L” or “R” in an automatic transmission, etc.) when the operation button is operated by the occupant and the gear ratio of the transmission is selected. May be generated in the case of a position corresponding to Further, such an input may be generated without an operation of a passenger or the like from a controller, another device, or the like when a certain condition defined as maintaining the vehicle speed is satisfied.

  By executing the vehicle speed maintenance control, the vehicle speed is generally maintained below a predetermined value (that is, the target vehicle speed) during the macroscopic period. Such control takes, for example, a mode in which the braking pressure is increased when the vehicle speed exceeds a predetermined value, and the braking pressure is reduced when the vehicle speed becomes less than the predetermined value. That is, preferably, the vehicle speed is maintained below a predetermined value by feedback control of the braking pressure or the hydraulic pressure corresponding to the braking pressure based on the vehicle speed.

  On the other hand, such vehicle speed maintenance control tends to apply a large load to the braking means or particularly to the hydraulic pressure control drive system when the braking means includes the hydraulic pressure control drive system. Therefore, even during a period when the vehicle speed maintenance control is required, it is less necessary to control the hydraulic pressure that defines the braking force (for example, the vehicle speed does not increase without applying any braking force). It is desirable to end the vehicle speed maintenance control on a slope.

  However, from this point of view, when the vehicle speed maintenance control is terminated when the vehicle speed is less than a predetermined value (target vehicle speed) that is sufficiently smaller than the predetermined value (target vehicle speed), such a determination is made only on a gentle slope slope. Since it does not fall below the value (for example, it is possible to reduce the vehicle speed by increasing the braking force), the vehicle may be reaccelerated with the end of the vehicle speed maintenance control, and comfort may be impaired. In order to solve such a problem, if the determination value is set to a very small value, it is extremely difficult to reach within the range of realistic braking control, and the vehicle speed maintenance control can be ended even if the vehicle speed maintenance control may be ended after all. Inconveniences such as being continued.

  Therefore, the vehicle control apparatus according to the present invention is configured to be able to end the vehicle speed maintenance control efficiently and effectively as follows.

  That is, according to the vehicle control apparatus of the present invention, the hydraulic pressure corresponding to the braking force is specified by the specifying means during the operation. Here, the “specific” in the present invention is not only directly detected by, for example, physical, electrical, mechanical, mechanical, or chemical detection means, but also the detected result as an electrical signal. It is a concept that includes indirectly acquiring and further deriving from these detected or acquired values based on a predetermined algorithm or calculation formula. Therefore, the specifying means according to the present invention may be a detecting means such as a pressure sensor arranged at a predetermined position of the braking means, and the temperature detected by these detecting means can be acquired as an electric signal. It may be a processing unit such as an ECU (Electronic Control Unit) configured as described above. The position of the detection means for directly detecting the hydraulic pressure may be determined in advance as a position having a relatively high correlation with the braking force, for example, experimentally, empirically, or based on simulation. . Moreover, the quantity of a detection means is not limited at all. When a plurality of detection means are provided, a numerical value defining the hydraulic pressure may be derived by numerical calculation processing based on a plurality of pressure detection results (pressure values).

  The “hydraulic pressure corresponding to the braking force” is the hydraulic pressure in the braking means, and has some correspondence with the braking force, and the correspondence is known at least qualitatively in advance. It is a concept that encompasses That is, it indicates a hydraulic pressure that has been found to increase or decrease at least as the braking force increases. Of course, the brake pressure (for example, wheel cylinder pressure etc.) mentioned above may be sufficient. Alternatively, in the case where the braking means includes a hydraulic pressure control drive system as described above, and the hydraulic pressure control drive system includes a differential pressure valve that centrally controls the braking pressure corresponding to each wheel, the differential pressure valve The target differential pressure may be used as the “hydraulic pressure corresponding to the braking force” according to the present invention.

  The second control means ends the vehicle speed maintenance control based on the hydraulic pressure specified in this way. Here, only when the vehicle descends the slope, the vehicle descends mainly due to the influence of the gravity component, so the necessary braking force is inevitably proportional to the gravity component acting in the downward direction. Relationship. The gravity component is, of course, proportional to the slope of the slope, and as a result, the braking force required to maintain the vehicle speed has a corresponding relationship with the slope of the slope at least in the long term. That is, unlike the vehicle speed, the hydraulic pressure corresponding to the braking force can be correlated with the slope of the slope.

  Therefore, when the vehicle speed maintenance control is terminated based on the hydraulic pressure corresponding to the braking force, the vehicle speed maintenance control termination control according to the gradient is possible without specifying the slope of the slope. If the slope is gentle, even if the vehicle speed maintenance control is terminated, the vehicle does not accelerate rapidly, and even if the vehicle speed is maintained at a sufficiently low value, the braking force (or hydraulic pressure) is low. If it is high, the vehicle is only braked by applying a large braking force on a steep slope, and the vehicle speed maintenance control is obviously not a condition to end.

  As described above, according to the vehicle control device of the present invention, the vehicle speed maintenance control is terminated based on the hydraulic pressure of the brake fluid corresponding to the braking force. The vehicle speed maintenance control can be ended. That is, it becomes possible to end the vehicle speed maintenance control efficiently and effectively, which is clearly advantageous compared to the case where the vehicle speed maintenance control is not necessarily ended based on a vehicle speed that is not uniquely defined by the slope of the slope. Configured.

  The first control means and the second control means according to the present invention are means for executing and ending the vehicle speed maintenance control, respectively, so that at least some of them may have a common hardware configuration.

  In one aspect of the vehicle control apparatus according to the present invention, the second control means ends the vehicle speed maintenance control when the hydraulic pressure is equal to or lower than a predetermined value.

  According to this aspect, since the second control means ends the vehicle speed maintenance control when the specified hydraulic pressure is equal to or lower than the predetermined value, the determination as to whether or not to perform the vehicle speed maintenance control is performed relatively simply. It is possible and preferable. The predetermined value may be set in advance experimentally, empirically, or based on a simulation or the like as a value that can suitably terminate the vehicle speed maintenance control.

  In another aspect of the vehicle control apparatus according to the present invention, the second control means ends the vehicle speed maintenance control when the state where the hydraulic pressure is equal to or lower than a predetermined value continues for a predetermined time or longer.

  In this case, since the vehicle speed maintenance control ends when the state where the hydraulic pressure is below the predetermined value continues for a predetermined time or more, the hydraulic pressure corresponding to the braking force decreases in a situation where the slope of the slope is not sufficiently gentle for some reason. In addition, it is possible to reduce the possibility that an erroneous determination occurs when the value becomes a predetermined value or less. The predetermined time may be determined in advance experimentally, empirically, or based on simulation or the like, for example, as a time that can accurately determine that the slope is a gentle slope.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment>
Preferred embodiments of the present invention will be described below with reference to the drawings as appropriate.

<Configuration of Embodiment>
First, with reference to FIG. 1, the structure of the vehicle 10 which concerns on one Embodiment of this invention is demonstrated. Here, FIG. 1 is a schematic view of the vehicle 10.

  In FIG. 1, a vehicle 10 is an example of a “vehicle” according to the present invention, and is a four-wheel drive vehicle. The vehicle 10 includes an engine 11 that is a power source. The engine 11 is, for example, a gasoline engine. The engine 11 transmits a rotational driving force output from the engine 11 to a driving shaft 14F and a driving shaft 14R, which will be described later, and a transmission 12 and a transfer (sub-motor) for decelerating (shifting) the rotation of the rotational driving force. A transmission 13 is connected.

  The transmission 12 is configured such that the driver can select one gear from among a plurality of gears having mutually different gear ratios by operating a shift lever (not shown). Is an automatic transmission (AT) configured to be able to automatically execute.

  The transfer 13 is an auxiliary transmission that distributes the driving force transmitted from the transmission 12 to the front wheel side drive shaft 14F and the rear wheel side drive shaft 14R. The transfer 13 includes a differential device (center differential) therein, and absorbs a rotation difference generated between the front wheels and the rear wheels when the vehicle 10 turns.

  The front wheel side drive shaft 14F is connected to the left and right drive shafts 16FL and 16FR via a front differential 15F, and the drive shafts 16FL and 16FR are connected to wheels FL (left front wheel) and FR (right front wheel), respectively. Yes. The rear wheel side drive shaft 14R is connected to the left and right drive shafts 16RL and 16RR via a rear differential 15R. The drive shafts 16RL and 16RR include a wheel RL (left rear wheel) and a wheel RR (right rear wheel), respectively. ) Are connected. In the vehicle 10, the driving torque of the engine 11 is transmitted to each wheel through these mechanisms.

  The wheels FL, FR, RL and RR are provided with braking devices 17FL, 17FR, 17RL and 17RR, respectively. Each brake device is provided with wheel cylinders 18FL, 18FR, 18RL and 18RR, respectively, and a mechanism for braking the vehicle 10 by driving a brake member (not shown) according to the hydraulic pressure of the brake fluid. Yes. Each aspect of the braking device may have any aspect as long as the vehicle 10 can be braked, and preferably adopts an aspect such as a disc brake or a drum brake.

  The wheels FL, FR, RL and RR are provided with wheel speed sensors 19FL, 19FR, 19RL and 19RR, respectively. Each wheel speed sensor is configured to be able to detect the wheel speed and rotation direction of each wheel.

  Each wheel cylinder is normally configured so that the hydraulic pressure of the brake fluid is transmitted via the master cylinder 20, and the hydraulic pressure in the master cylinder 20 depends on the amount of depression of the brake pedal 21 by the driver. It is configured to increase or decrease. Therefore, normally, the braking force of each braking device is controlled by the driver's brake pedal operation.

  On the other hand, a brake actuator 200 is interposed between each wheel cylinder and the master cylinder 20. The brake actuator 200 is electrically connected to the ECU 100, which will be described later, and the hydraulic pressure of each wheel cylinder is increased or decreased under the control of the ECU 100 regardless of the braking operation (for example, the operation of the brake pedal 21) by the driver. Is configured to be possible. The brake actuator 200, the master cylinder 20, each braking device, and each wheel cylinder are configured to function as an example of the “braking system” according to the present invention. The brake actuator 200 is configured to function as an example of the “hydraulic pressure control drive system” according to the present invention.

  The start switch 22 is disposed at a predetermined position of the vehicle 10 such as a console panel so that the driver can operate it. When the activation switch 22 is pressed, an activation signal that prompts execution of vehicle speed maintenance control described later is output. The start switch 22 is electrically connected to the ECU 100, which will be described later, and the depression of the start switch by the driver or the like is always monitored by the ECU 100 through the input of the start signal.

  The shift position sensor 23 is a sensor that detects the position (ie, shift position) of a shift lever (not shown) for selecting the gear ratio of the transmission 12. The shift position sensor 23 is electrically connected to the ECU 100 described later, and the shift position detected by the shift position sensor 23 is output to the ECU 100 as an electric signal representing the shift position. .

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like and is configured to be able to control the entire operation of the vehicle 10. This is an example of a “vehicle control device”. The ECU 100 is configured to be able to execute vehicle speed maintenance control, which will be described later, by executing a control program stored in the ROM.

  Further, the ECU 100 is electrically connected to the brake actuator 200, and controls the brake actuator 200 to the upper level so that the braking force applied to each wheel via the brake actuator 200 is irrelevant to the driver's braking operation. It is configured to be able to be controlled.

<Configuration of brake actuator>
Next, a part of the configuration of the brake actuator 200 will be described with reference to FIG. FIG. 2 is a schematic diagram of the brake actuator 200. In FIG. 2, the same portions as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted as appropriate. FIG. 2 also shows a brake fluid transmission path to the wheel FR as the right front wheel and the wheel RL as the left rear wheel for the sake of simplicity.

  In FIG. 2, the brake actuator 200 includes a motor 201. The motor 201 is a drive source for driving the pump 202, and the pump 202 supplied with the driving force from the motor 201 pumps the brake fluid from the reservoir 203 and supplies it to the pipe line 217 via the check valve 204. It is configured to be possible.

  A differential pressure valve 205 is disposed in a pipe line 211 connected to the master cylinder 20. The differential pressure valve 205 is an open valve that allows the brake fluid to pass in both directions when not energized, and more specifically, the downstream side (what is the master cylinder) so that the differential pressure at both ends is maintained at the target differential pressure when energized. This is a valve that functions as a pressure regulating valve that opens and closes so that the pressure on the different side is higher than the upstream side by the target differential pressure. The target differential pressure is set by the ECU 100 electrically connected to the brake actuator 200. Further, a check valve 206 is disposed in a pipe line that bypasses the differential pressure valve 205 in the pipe line 211.

  The pipe 211 is branched into pipes 213 and 214 corresponding to the wheels FR and RL, respectively, on the downstream side of the differential pressure valve 205. The pipe line 217 described above is disposed so as to join the position where the pipe line 211 branches into the pipe lines 213 and 214. Incidentally, at the upstream position of the differential pressure valve 205, the pipe line 212 is connected to the reservoir 203, and braking fluid is supplied from the reservoir 203.

  A pressure increasing valve 209 is disposed in the pipe line 213. The pressure increasing valve 209 is an electromagnetic valve whose open / close state is switched under the control of the ECU 100. Further, the pressure increasing valve 209 is configured to open when not energized. Further, the pipe line 213 further branches into the pipe line 215 at the downstream position of the pressure increasing valve 209. A pressure reducing valve 210 is disposed in the pipe line 215. The pressure reducing valve 210 is an electromagnetic valve whose open / closed state is switched under the control of the ECU 100. Further, the pressure reducing valve 210 is configured to close when not energized. On the other hand, the pipe line 214 has the same configuration as the pipe line 213, a pressure increasing valve 207 is installed on the pipe line 214, and a pressure reducing valve 208 is provided on the pressure reducing path 216 branched from the pipe line 214. The pipe lines 214 and 215 are connected to the downstream positions of the pump 202, respectively.

<Operation of Embodiment>
<Details of braking mode>
In the vehicle 10, a plurality of braking modes for braking the vehicle 10 are realized by the ECU 100 controlling the brake actuator 200. The details of a plurality of braking modes provided in the vehicle 10 will be described with reference to FIG.

<Normal braking mode>
The normal braking mode is a mode in which a braking force corresponding to the depression amount of the brake pedal 21 is applied to each wheel, in other words, a braking mode that directly reflects the driver's braking intention. When executing the normal braking mode (in this embodiment, the normal braking mode is selected by default), the ECU 100 deenergizes the differential pressure valve 205 and stops the operation of the motor 201 and the pump 202. Accordingly, the differential pressure valve 205 is simply opened, and the master cylinder pressure of the master cylinder 20 is transmitted to each wheel cylinder via the differential pressure valve 205, the pressure increasing valve 207, and the pressure increasing valve 209.

<Pressure increase mode>
When executing the pressure increasing mode, the ECU 100 energizes the differential pressure valve 205 and further operates the motor 201 and the pump 202. At this time, the pump 202 is driven such that a hydraulic pressure higher than the target differential pressure set by the ECU 100 is applied to the differential pressure valve 205. On the other hand, since the differential pressure valve 205 opens and closes so as to maintain the differential pressure between the upstream end and the downstream end at the target differential pressure, the valve opens when the hydraulic pressure applied to the downstream side is equal to or higher than the target differential pressure. Then, the brake fluid is passed through the upstream side, which is the low pressure side. On the other hand, when the hydraulic pressure applied to the downstream side is less than the target differential pressure, the differential pressure valve 205 is closed, so that the hydraulic pressure downstream of the differential pressure valve 205 eventually becomes the target difference by repeatedly opening and closing the differential pressure valve 205. Maintained at pressure.

  In this state, the ECU 100 opens the pressure increasing valves 207 and 209 and closes the pressure reducing valves 208 and 210 while the hydraulic pressure downstream of the differential pressure valve 205 is maintained at the target differential pressure. As described above, since each pressure increasing valve is an electromagnetic valve that opens when not energized, and each pressure reducing valve is an electromagnetic valve that closes when not energized, the ECU 100 eventually energizes them in the pressure increasing mode. Not performed. The target differential pressure, which is the hydraulic pressure downstream of the differential pressure valve 205, is transmitted to each braking device via each pressure increasing valve, and the braking force applied to each wheel increases and decreases as the target differential pressure increases and decreases, respectively. Centrally controlled by differential pressure. That is, the target differential pressure is an example of the “hydraulic pressure corresponding to the braking force” according to the present invention.

<Pressure reduction mode>
In the pressure reducing mode, the ECU 100 closes the pressure increasing valve 207 or the pressure increasing valve 209 and opens the pressure reducing valve 208 or the pressure reducing valve 210. In a state where the open / close state of the downstream valve is controlled in this way, the ECU 100 further drives the motor 201 and the pump 202, and causes the brake fluid in the pipe 213 or the pipe 214 to pass through the pipe 215 or the pipe 216. Suctioning up, the wheel cylinder pressure in one wheel cylinder is reduced. That is, in the decompression mode, it is possible to reduce only the braking force applied to one of the wheels.

<Retention mode>
In the holding mode, the ECU 100 closes the pressure increasing valve 207 and the pressure reducing valve 208 or the pressure increasing valve 209 and the pressure reducing valve 210. In this state, the hydraulic pressure applied to each wheel cylinder at the present time is maintained. The holding mode is selected, for example, to hold the reduced pressure state for a certain period after the reduced pressure mode is executed.

<Vehicle control>
The ECU 100 is configured to be able to execute vehicle speed maintenance control by controlling the brake actuator 200. Here, with reference to FIG. 3, one control of the vehicle 10 including the vehicle speed maintenance control will be described. FIG. 3 is a flowchart of such a control.

  In FIG. 3, after starting the vehicle 10, the ECU 100 determines whether or not an execution condition for vehicle speed maintenance control is satisfied (step A <b> 10). Here, the execution condition is when the above-described start signal is input from the start switch 22 and the shift position of the transmission 12 is in the “L” or “R” position where the gear ratio can be maximized in each of the forward and backward travels. Point to. The shift position is acquired as a sensor output of the shift position sensor 23.

  When the execution condition of the vehicle speed maintenance control is not satisfied (step A10: NO), the ECU 100 repeats step A10 until the execution condition is satisfied, and waits for the execution of the vehicle speed maintenance control. On the other hand, when the execution condition of the vehicle speed maintenance control is satisfied (step A10: YES), the ECU 100 starts the vehicle speed maintenance control (step A11).

  When starting the vehicle speed maintenance control, the ECU 100 shifts the above-described braking mode from the default normal braking mode to the pressure increasing mode. That is, the ECU 100 operates the motor 201 and the pump 202 in the brake actuator 200, sets an initial value of the target differential pressure Pt of the differential pressure valve 205, and energizes the differential pressure valve 205. The initial value of the target differential pressure Pt is stored in advance in the ROM, and the ECU 100 reads the initial value from the ROM and sets it as the initial value of the target differential pressure Pt. Along with this, the hydraulic pressure of the braking fluid transmitted via the brake actuator 200 is maintained at the target differential pressure Pt. That is, in this case, the target differential pressure Pt acts as an example of the “hydraulic pressure corresponding to the braking force” according to the present invention. In the present embodiment, the initial value of the target differential pressure Pt is set to about several Mpa (for example, about 5 Mpa).

  When the vehicle speed maintenance control is started, the ECU 100 calculates the vehicle speed of the vehicle 10 based on the output of each wheel speed sensor and determines whether the vehicle speed is higher than the target vehicle speed Vt (step A12). In the present embodiment, the target vehicle speed Vt is set to 5 km / h. The target vehicle speed Vt may be given as a constant or indefinite speed range. In this case, in the process according to step A12, a comparison between the upper limit value that defines the speed range and the vehicle speed may be performed.

  When the vehicle speed is higher than the target vehicle speed Vt, the ECU 100 adds the increase constant A to the target differential pressure Pt by assuming that the braking force is insufficient with the target differential pressure Pt set at the present time. Is updated (step A13). The value of the increase constant A is not particularly limited, but is given as a value that can avoid an excessive increase or decrease in braking force and can quickly maintain the vehicle speed at the target vehicle speed. In this embodiment, the increase constant A is set to a value of about 1 Mpa.

  When the process related to step A13 is executed or the vehicle speed is equal to or lower than the target vehicle speed Vt (step A12: NO), the ECU 100 determines whether or not the vehicle speed is less than the target vehicle speed Vt (step A14). When the vehicle speed is less than the target vehicle speed Vt (step A14: YES), the ECU 100 determines that the braking force is excessive at the target differential pressure Pt, and subtracts the decrease constant B (B <A) from the target differential pressure Pt. Then, the target differential pressure Pt is updated (step A15). Here, the decrease constant B is defined as a value less than the increase constant A in this embodiment, but may be a value equal to the increase constant A or a value greater than the increase constant A.

  When the processing according to step A15 is executed or the vehicle speed is the target vehicle speed Vt (step A14: NO), the ECU 100 determines whether the target differential pressure Pt at that time is less than a preset reference differential pressure Pend It is determined whether or not (step A16). When the target differential pressure Pt is not less than the reference differential pressure Pend (step A16: NO), the ECU 100 returns the process to step A12 and continues the vehicle speed maintenance control. On the other hand, when the target differential pressure Pt is less than the reference differential pressure Pend (step A16: YES), the ECU 100 has an elapsed time after the target differential pressure Pt becomes less than the reference differential pressure Pend is equal to or greater than a predetermined threshold Tth. (Step A17). If the predetermined elapsed time has not elapsed (step A17: NO), the ECU 100 returns the process to step A12 and continues the vehicle speed maintenance control.

  On the other hand, when the elapsed time after the target differential pressure Pt becomes less than the reference differential pressure Pend is equal to or greater than the threshold Tth (step A17: YES), the ECU 100 is in a state where the target differential pressure Pt is stabilized at a sufficiently small value. That is, assuming that the slope of the slope on which the vehicle 10 descends has become sufficiently small, the vehicle speed maintenance control is terminated (step A18). Ending the vehicle speed maintenance control means stopping the operation of the motor 201 and the pump 202, stopping the energization of the differential pressure valve 205, and shifting the braking mode to the normal braking mode. When the vehicle speed maintenance control is finished, the process is returned to step A10 again to determine whether or not the execution condition of the vehicle speed maintenance control is satisfied, and the above-described series of processing is repeated.

  As described above, in the vehicle 10 according to the present embodiment, the ECU 100 determines whether or not to end the vehicle speed maintenance control based on the braking pressure in the brake actuator 200 (that is, the target differential pressure of the differential pressure valve). Thus, the vehicle speed maintenance control is terminated when the braking pressure has become sufficiently small. Since the target differential pressure Pt correlates with the slope of the slope in the long term, the vehicle speed maintenance control is eventually controlled while taking the slope of the slope into consideration. Therefore, a situation in which the vehicle 10 is accelerated again at the moment when the vehicle speed maintenance control is finished and the braking mode is shifted to the normal braking mode is prevented. That is, a decrease in the comfort of the vehicle 10 due to the end of the vehicle speed maintenance control is prevented.

  On the other hand, if the vehicle speed maintenance control end criterion is whether or not the vehicle speed is sufficiently lower than the target vehicle speed, the vehicle speed does not necessarily decrease to such a small value, so the vehicle speed maintenance control becomes redundant. It may continue. According to this embodiment, the situation where the vehicle speed maintenance control is continued redundantly is effectively prevented. That is, the operation opportunity of the brake actuator 200 can be optimized, and the brake actuator 200 can be used efficiently. That is, according to the present embodiment, it is possible to efficiently and effectively prevent control for maintaining the vehicle speed.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Is also included in the technical scope of the present invention.

It is a mimetic diagram of a vehicle concerning one embodiment of the present invention. It is a schematic diagram of the brake actuator with which the vehicle of FIG. 1 is equipped. 2 is a flowchart of one control including a vehicle speed maintenance control executed by an ECU in the vehicle of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 11 ... Engine, 22 ... Start switch, 23 ... Shift position sensor, 100 ... ECU, 200 ... Brake actuator.

Claims (3)

A vehicle control device that controls a vehicle including a braking unit that applies a braking force according to a hydraulic pressure of a braking fluid to a wheel,
First control means for executing vehicle speed maintenance control for controlling the braking means so that the speed when the vehicle descends the slope is maintained below a predetermined value in response to a predetermined input;
Specifying means for specifying a hydraulic pressure corresponding to the braking force in the braking means;
And a second control means for ending the vehicle speed maintenance control based on the specified hydraulic pressure. The vehicle control device according to claim 1, wherein the second control means ends the vehicle speed maintenance control when the hydraulic pressure is equal to or lower than a predetermined value. The vehicle control device according to claim 2, wherein the second control means ends the vehicle speed maintenance control when the state where the hydraulic pressure is equal to or lower than a predetermined value continues for a predetermined time or longer.

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