JP5189462B2 - Booster device and hydraulic brake device - Google Patents

Description

  The present invention relates to a booster device including a vacuum booster and a hydraulic brake device including the booster device.

Patent Document 1 describes a hydraulic brake device including a vacuum booster and a brake hydraulic pressure control device that controls the brake cylinder pressure so that the characteristics are the same before and after the assist limit after the assist limit of the vacuum booster. Has been. In the brake device described in Patent Literature 1, it is assumed that the assist limit is reached when the master cylinder pressure becomes larger than a set value.
Patent Document 2 describes a hydraulic brake device including a vacuum booster and a brake hydraulic pressure control device that controls the brake cylinder pressure so that the characteristics are the same before and after the assist limit after the assist limit of the vacuum booster. Has been. In this hydraulic brake device, it is assumed that the assist limit has been reached when a set time has elapsed since the increase gradient of the master cylinder pressure has decreased. Based on the decrease in the increase gradient of the master cylinder pressure, it is possible to detect that the assist limit has been reached even if a gain abnormality occurs in the master cylinder pressure sensor.
Patent Document 3 describes a brake device including a vacuum booster and a vacuum pump that is connected to a negative pressure chamber of the vacuum booster and is operated in accordance with rotation of a rotating shaft provided in the vehicle. Since the vacuum pump is not operated by the engine, it is possible to suppress a decrease in the negative pressure in the negative pressure chamber of the vacuum booster even in an electric vehicle that does not include the engine or a hybrid vehicle that does not operate frequently. .
JP 2001-334927 A JP 2000-168543 A JP 2007-223449 A

  The object of the present invention is to accurately detect that the vacuum booster has reached the assist limit.

Means and effects for solving the problem

The booster device according to claim 1 includes: (1) a brake operating member; (2) (a) a power piston linked to a pressurizing piston of a master cylinder; and (b) a negative pressure in front of the power piston. And a rear variable chamber, and (c) a control valve that selectively communicates the variable pressure chamber with the negative pressure chamber and the atmosphere as the power piston and the brake operation member move relative to each other. A vacuum booster, and (3) at least the pressure in the negative pressure chamber is a pressure in a standard state from a pressure in a standard state in which the vacuum booster is in a predetermined state before the operation of the brake operating member is started. An assisting limit detecting device for detecting that the vacuum booster has reached the assisting limit when approaching the atmospheric pressure for a set change amount determined or more is included.
In a vacuum booster (hereinafter, simply referred to as a booster), when the brake operation member is operated and the power piston is advanced, the volume of the negative pressure chamber decreases, so the pressure in the negative pressure chamber approaches atmospheric pressure. It is known that the pressure in the negative pressure chamber approaches the atmospheric pressure by a set change amount or more from the standard state of the booster until the assist limit is reached. Therefore, when the pressure in the negative pressure chamber approaches the atmospheric pressure by a set change amount or more from the pressure in the standard state, it can be assumed that the booster has reached the assist limit.
On the other hand, the increasing gradient of the hydraulic pressure of the master cylinder may be reduced due to the driver's operation. Therefore, when based on the change in the increasing gradient of the master cylinder pressure as in the brake device described in Patent Document 3, it may not be possible to accurately detect that the booster has reached the assist limit. On the other hand, as described in claim 1, when it is based on the amount of change in the pressure in the negative pressure chamber, it is possible to more accurately detect that the booster has reached the assisting limit. Moreover, since it is not detected based on the operation stroke of a brake operation member, a stroke sensor becomes unnecessary and the cost of a booster apparatus can be reduced by that much.
The standard state is a predetermined state before the booster reaches the assist limit, for example, the non-operation state of the brake operation member (the state before the brake operation is started, and the change in the pressure of the negative pressure chamber is small. For example, a steady state), a state when the brake operation is started, a state when a set time has elapsed after the operation of the brake operation member is started, and the like.
The set change amount can be a predetermined fixed value or a variable value. It is known that the amount of change in the pressure of the negative pressure chamber from the standard state until reaching the assist limit is larger when the pressure of the negative pressure chamber in the standard state is close to vacuum than when it is close to atmospheric pressure (FIG. 8). , 9). Therefore, it is desirable that the set change amount be a variable value determined by the pressure of the negative pressure chamber in the standard state (Claim 3).
Hereinafter, the pressure in the negative pressure chamber of the booster is a value (negative pressure) between atmospheric pressure and vacuum, and hence may be referred to as booster negative pressure hereinafter. In addition, when the booster negative pressure is close to vacuum, the negative pressure is high, and when it is close to atmospheric pressure, the negative pressure is sometimes low. The decrease in the booster negative pressure means that the pressure approaches the atmospheric pressure, and the decrease in the decrease gradient means that the gradient approaching the atmospheric pressure becomes gentle. Note that the gradient of decrease when the booster negative pressure approaches atmospheric pressure is a positive value, and when the gradient of decrease is large, the absolute value of the positive value is large.
3. The booster device according to claim 2, wherein the assist limit detecting device comprises: (a) a booster negative pressure sensor that detects a booster negative pressure that is a pressure of the negative pressure chamber; and (b) a hydraulic pressure of the master cylinder. and the master cylinder pressure sensor, has become (c) (i) of the booster negative pressure detected by the booster negative pressure sensor, the amount of decrease in the pressure in the standard state of said vacuum booster has the setting change amount or more In addition, (ii) (x) a decrease gradient with respect to time of the booster negative pressure detected by the booster negative pressure sensor has become smaller than a first set value, and (y) detected by the master cylinder hydraulic pressure sensor. The vacuum booster has reached the assisting limit when at least one of the increase gradient with respect to the time of the hydraulic pressure of the master cylinder is reduced by the second set value or more is satisfied. It is assumed that a multi-condition correspondence detection unit for detection is included.
About (x) After the booster reaches the assisting limit, the boosting effect cannot be obtained, so that the brake operation with respect to time is performed in the normal operation state of the driver (for example, the state where the increasing gradient of the pedaling force with respect to time is constant). The increasing gradient of the member stroke decreases rapidly, and the increasing gradient of the power piston stroke decreases rapidly. For this reason, the decreasing gradient of the negative pressure chamber volume with respect to time decreases rapidly, and the decreasing gradient of the booster negative pressure decreases rapidly (the gradient approaching atmospheric pressure decreases rapidly). Therefore, it can be assumed that the booster has reached the assisting limit when the decreasing gradient with respect to the time of the booster negative pressure becomes smaller than the first set value.
Regarding (y) Similarly, when the booster reaches the assist limit, the boosting effect cannot be obtained, and therefore, in the master cylinder, the increasing gradient of the pressurizing piston stroke with respect to time decreases, and the pressurizing chamber of the master cylinder increases. The pressure gradient becomes gentle. Therefore, when the increase gradient with respect to time of the master cylinder pressure becomes smaller than the second set value, it can be assumed that the booster has reached the assist limit.
The first set value and the second set value can be set in advance (fixed values). For example, when the driver operates the brake operation member in a standard state, the change in the negative pressure decrease gradient and the increase in the master cylinder pressure increase caused by the booster reaching the assist limit are tested. They can be obtained by simulation or the like, and can be determined based on the obtained changes.
Further, the booster negative pressure in the standard state may be a value estimated based on the operating state of the engine or the like, or a value detected by a booster negative pressure sensor. When the standard state is a steady state, the statistically processed value such as the average value of the detected values of multiple times is adopted as the “booster negative pressure in the standard state” or the detected value immediately before the operation is adopted. be able to.
In the booster device according to claim 2, (i) the booster negative pressure decrease amount is equal to or greater than the set change amount, and (x) the booster negative pressure decrease gradient is decreased by the first set value or more. It is detected that the assist limit has been reached when two conditions are satisfied, (i) condition, and (y) the increase gradient of the master cylinder pressure has become smaller than the second set value. When it is satisfied, it can be detected that the assist limit has been reached, or when all the three conditions (i), (x) and (y) are satisfied, it can be detected that the assist limit has been reached. . Thus, since it is based on two or more conditions, it can detect more accurately that the booster has reached the assist limit. Furthermore, when the three conditions (i), (x), and (y) are used, it is possible to detect that the assist limit has been reached more accurately.
According to a fourth aspect of the present invention, there is provided a hydraulic brake device comprising: (1) a booster device according to any one of the first to third aspects; (2) a brake cylinder connected to the master cylinder; (4) After the vacuum booster reaches the assisting limit, an increasing gradient of the hydraulic pressure of the brake cylinder with respect to the operating force applied to the brake operating member is before and after the vacuum booster reaches the assisting limit. A brake hydraulic pressure control device for controlling the hydraulic pressure of the brake cylinder using the hydraulic pressure of the power hydraulic pressure source so as to be the same, wherein the pressure of the negative pressure chamber in the standard state of the vacuum booster And a storage unit for storing the relationship between the hydraulic pressure of the master cylinder when the vacuum booster reaches the assist limit and the hydraulic pressure at the assist limit, and the actually acquired standard state The hydraulic pressure at the assisting limit is obtained from the pressure in the negative pressure chamber and the relationship, and the hydraulic pressure control of the brake cylinder is performed when the actual hydraulic pressure of the master cylinder reaches the hydraulic pressure at the assisting limit. The brake hydraulic pressure control device includes a brake hydraulic pressure control device that starts the operation, wherein the brake hydraulic pressure control device stores the pressure of the negative pressure chamber in the standard state actually acquired in the storage unit, and A relationship storage unit for storing an actual relationship acquired based on at least one set of the actual hydraulic pressure of the master cylinder when it is detected by the assist limit detection device that the vacuum booster has reached the assist limit; It is supposed to be.
In the hydraulic brake device, the relationship between the booster negative pressure in the standard state and the master cylinder hydraulic pressure (hydraulic pressure at the assisting limit) when the booster reaches the assisting limit is stored in advance and actually acquired. Based on the booster negative pressure in the standard state and the relationship stored in the storage unit, the hydraulic pressure at the assist limit is obtained, and when the actual master cylinder pressure reaches the assist limit hydraulic pressure, the booster reaches the assist limit. As a result, the hydraulic pressure control of the brake cylinder is started. Therefore, even if the booster negative pressure in the standard state changes, it is possible to accurately detect that the assist limit has been reached.
On the other hand, the storage unit normally stores the same relationship (relationship between the booster negative pressure in the standard state and the hydraulic pressure at the assist limit) for a large number of vehicles. Not all are the same, but may vary from vehicle to vehicle. For example, due to mechanical variations in booster and master cylinder characteristics, variations in booster negative pressure sensor, master cylinder hydraulic pressure sensor characteristics, A / D conversion errors in computers, etc. is there. In addition, the characteristics of the booster negative pressure sensor and the master cylinder hydraulic pressure sensor may change over time due to changes in the electronic circuit due to temperature, heat, etc., and the relationship may change over time. In any case, if the relationship stored in advance is different from the actual relationship, it is impossible to accurately detect that the booster has reached the assistance limit, and the assistance limit has not actually been reached. However, the hydraulic pressure control of the brake cylinder may be started (before reaching the assist limit), or may be started after the assist limit is actually reached, resulting in a decrease in the driver's brake feeling. was there.
Therefore, in the brake device according to the fourth aspect, the relationship is actually acquired and stored. Based on the actual relationship, it is possible to accurately detect that the booster has reached the assistance limit. Moreover, it becomes possible to start the hydraulic pressure control of the brake cylinder when the booster actually reaches the assist limit, and it is possible to suppress a decrease in the brake feeling of the driver.
The actual relationship is acquired when one or more sets of the actually acquired booster negative pressure in the standard state and the actual master cylinder hydraulic pressure when the assist limit is reached are acquired. For example, when the relationship is represented by a straight line, if the slope, intercept, etc. of the straight line are determined in advance, an actual straight line can be obtained based on one point (one set). Moreover, one approximate straight line (actual relationship) can be acquired based on a plurality of sets.
“The actual relationship is stored in the storage unit” means that the actual relationship is acquired before shipment of the vehicle and stored in the storage unit, and the actual relationship is acquired and stored after shipment. To be stored on behalf of If the actual relationship is acquired and stored at least once after shipment, the difference in relationship due to individual variations in the vehicle can be corrected. If the actual relationship is periodically acquired and stored, changes in the relationship over time can be corrected.
In addition, when the acquired actual relationship is in an area determined by a pre-stored common relationship, it is not corrected, and may be corrected when it is out of the area.
Also, in brake cylinder hydraulic pressure control, (a) the brake cylinder hydraulic pressure is controlled directly using the hydraulic pressure of the power hydraulic pressure source. The hydraulic pressure of the brake cylinder may be controlled by controlling using the hydraulic pressure of the hydraulic pressure source.

Hereinafter, a hydraulic brake system including a booster device according to an embodiment of the present invention will be described in detail with reference to the drawings.
In this hydraulic brake system, as shown in FIG. 1, the depressing force of the brake pedal 10 is boosted by the vacuum booster 12, and the hydraulic pressure corresponding to the boosted depressing force is generated in the master cylinder 14. This hydraulic pressure is supplied to the brake cylinder 18 of the brake 16 provided on the wheel, and the brake cylinder 18 is actuated by the hydraulic pressure to suppress the rotation of the wheel. A hydraulic pressure control unit 20 that is an actuator that controls the hydraulic pressure of the brake cylinder 18 is provided between the brake cylinder 18 and the master cylinder 14. The hydraulic pressure control unit 20 is controlled by an electronic control unit 24 (hereinafter referred to as a brake ECU 24).

A vacuum booster (hereinafter simply referred to as a booster) 12 is connected to an intake manifold 32 of the engine 30 in a negative pressure chamber to be described later, and is supplied with negative pressure. Intake manifold 32 is on the intake side of the engine and communicates with the atmosphere via electronically controlled throttle valve 34.
A check valve 36 is provided between the booster 12 and the intake manifold 32. The check valve 36 allows supply of negative pressure from the intake manifold 32 to the booster 12 (air of the booster 12 is sucked to the intake manifold 32 side), but outflow of negative pressure from the booster 12 to the intake manifold 32. (Air in intake manifold 32 is sucked into booster 12). Therefore, the negative pressure on the booster 12 side is lower than the negative pressure on the intake manifold 32 side by the valve opening pressure of the check valve 36, that is, close to atmospheric pressure. A tank 38 is provided between the check valve 36 and the booster 12 to store a negative pressure. The tank 38 has a small capacity.
In the engine 30, the opening degree of the electronically controlled throttle valve 34, the fuel injection amount of the injector, the timing, and the like are controlled by an electronic control unit 40 (hereinafter referred to as EFI-ECU 40). The EFI-ECU 40 includes an intake manifold negative pressure sensor 42 that detects the negative pressure of the intake manifold 32, a throttle position sensor 44 that detects the opening of the electronically controlled throttle valve 34, an engine speed sensor 46 that detects the rotational speed, and the like. Are connected, the operating state of the engine 30 is detected based on the detected values, and the electronically controlled throttle valve 34, the injector and the like are controlled.

As shown in FIG. 2, the master cylinder 14 includes two pressure pistons 60a and 60b slidably fitted in series with the housing. Two pressurizing chambers 61a and 61b are formed in front of the pressurizing pistons 60a and 60b, respectively.
The booster 12 includes a hollow housing 64 and a power piston 66 provided in the housing 64, and the power piston 66 causes a negative pressure chamber 68 on the master cylinder 14 side and a variable pressure chamber 70 on the brake pedal 10 side. Partitioned.
The power piston 66 is linked to the brake pedal 10 via the valve operating rod 71 on the brake pedal 10 side, and linked to the booster piston rod 74 via the rubber reaction disk 72 on the master cylinder 14 side. It has been. The booster piston rod 74 is linked to the pressurizing piston 60a of the master cylinder 14, and transmits the operating force of the power piston 66 to the pressurizing piston 60a.

  A valve mechanism 76 is provided between the negative pressure chamber 68 and the variable pressure chamber 70. The valve mechanism 76 operates based on the relative movement between the valve operating rod 71 and the power piston 66, and includes a control valve 76a, an air valve 76b, a vacuum valve 76c, and a control valve spring 76d. The air valve 76b selectively performs communication / blocking with respect to the atmosphere of the variable pressure chamber 70 in cooperation with the control valve 76a, and is provided movably integrally with the valve operating rod 71. The control valve 76a is attached to the valve operating rod 71 in a state of being urged by the control valve spring 76d so as to be seated on the air valve 76b. The vacuum valve 76c selectively performs communication / blocking of the variable pressure chamber 70 with respect to the negative pressure chamber 68 in cooperation with the control valve 76a, and is provided so as to be movable integrally with the power piston 66.

In the booster 12 configured as described above, in a non-operating state, the control valve 76a is seated on the air valve 76b while being separated from the vacuum valve 76c, whereby the variable pressure chamber 70 is cut off from the atmosphere and the negative pressure chamber. 68. Therefore, in this state, both the negative pressure chamber 68 and the variable pressure chamber 70 are set to the same level of pressure (pressure below atmospheric pressure). On the other hand, in the operating state, the valve operating rod 71 approaches relatively to the power piston 66 and eventually the control valve 76a is seated on the vacuum valve 76c, so that the variable pressure chamber 70 is removed from the negative pressure chamber 68. Blocked. Thereafter, when the valve operating rod 71 comes closer to the power piston 66, the air valve 76b is separated from the control valve 76a, and thereby the variable pressure chamber 70 is communicated with the atmosphere. In this state, the pressure in the variable pressure chamber 70 approaches atmospheric pressure, a differential pressure is generated between the negative pressure chamber 68 and the variable pressure chamber 70, the power piston 66 is advanced by the differential pressure, and the booster 12 boosts the pressure. A hydraulic pressure corresponding to the applied brake operating force is generated in the master cylinder 14.
The pressure in the negative pressure chamber 68 (hereinafter sometimes abbreviated as a booster negative pressure) is detected by a booster negative pressure sensor 78, and the hydraulic pressure in the pressurizing chamber 61 b of the master cylinder 14 is detected by a master cylinder pressure sensor 79. The
As the volume of the negative pressure chamber 68 decreases as the power piston 66 advances, the booster negative pressure that is the negative pressure of the negative pressure chamber 68 decreases (approaches atmospheric pressure).

A hydraulic brake circuit of the hydraulic brake system will be described with reference to FIG.
The hydraulic brake circuit in this embodiment is an X pipe, and a first brake system for the right front wheel FR and the left rear wheel RL is connected to one pressurizing chamber 61b of the master cylinder 14, and the other pressurizing chamber 61b is pressurized. A second brake system for the left front wheel FL and the right rear wheel RR is connected to the chamber 61a. Since these brake systems have the same configuration, only the first brake system will be representatively described below, and description of the second brake system will be omitted.

  In the first brake system, the pressurizing chamber 61b, the brake cylinder 18 of the right front wheel FR, and the brake cylinder 18 of the left rear wheel RL are connected via a main passage 80, respectively. The main passage 80 includes a main passage 84 and an individual passage 86, and the brake cylinder 18 is connected to each of the individual passages 86. In the middle of each individual passage 86, a pressure increasing valve 90 that is a normally open electromagnetic on-off valve is provided, and a check valve 94 for returning the hydraulic fluid is provided in parallel with each pressure increasing valve 90. Each brake cylinder 18 is connected to a reservoir 98 via a reservoir passage 96, and a pressure reducing valve 100 that is a normally closed electromagnetic on-off valve is provided in the middle of the reservoir passage 96.

A pump passage 104 is connected to the reservoir 98 and is connected to the upstream side of the pressure increasing valve 90 in the main passage 80. The pump passage 104 is provided with a pump 106, a suction valve 108, a discharge valve 110, an orifice 114, and a fixed damper 116.
The reservoir 98 includes a hydraulic fluid storage part 118a and a replenishment valve 118b. The hydraulic fluid storage portion 118a is provided on the housing, a movable member 118d provided slidably on the housing, a spring 118e provided on one side of the movable member 118d, and the other side of the movable member 118d. The replenishing valve 118b includes a valve element 119a and a valve seat 119b, and a valve driving member 119c provided on the movable member 118a. The master cylinder 14 is connected to the supply valve 118b through a supply passage 119d.
The replenishment valve 118b is in a closed state when the hydraulic fluid is sufficiently stored in the storage chamber 118f. When the amount of hydraulic fluid stored in the storage chamber 118f falls below the set amount, the movable member 118d is moved, and the replenishing valve 118b is switched to the open state by the valve drive member 119c. As a result, the working fluid is supplied from the master cylinder 14 to the storage chamber 118f via the replenishment passage 119c, and the reservoir 98 is prevented from being short of working fluid.

  A pressure control valve 120 is provided between the connection portion of the pump passage 104 of the main passage 80 and the master cylinder 14 (connection portion of the replenishment passage 119c). The pressure control valve 120 controls the differential pressure between the hydraulic pressure on the brake cylinder 18 side and the hydraulic pressure on the master cylinder 14 side, and the differential pressure between the hydraulic pressure in the brake cylinder 18 and the hydraulic pressure in the master cylinder 14 is controlled. Just make it higher. The brake ECU 24 activates the pump 106 and the pressure control valve 120 when the brake is being operated by the driver and it is necessary to cause the brake cylinder 18 to generate a hydraulic pressure higher than the hydraulic pressure of the master cylinder 14. To control.

As shown in FIG. 4, the pressure control valve 120 includes a housing (not shown), a valve element 130 and a valve seat 132, and a solenoid 134 that generates a magnetic force for controlling the relative movement of the valve element 130 and the valve seat 132, A normally open valve that includes a spring 136 that urges the valve element 130 away from the valve seat 132, and is connected to the main passage 84 of the main passage 80, to the valve element 130, and from the hydraulic pressure of the brake cylinder 18 to the master cylinder 14. It is provided in a posture in which a differential pressure of a magnitude obtained by subtracting the hydraulic pressure is applied.
The pressure control valve 120 is open when the solenoid 134 is not excited (OFF state). In the main passage 80, bidirectional flow of hydraulic fluid between the master cylinder side and the brake cylinder side is allowed. As a result, when a brake operation is performed, the brake cylinder pressure becomes the same as the master cylinder pressure. Increased with increasing pressure.
On the other hand, in the action state (ON state) in which the solenoid 134 is excited, the sum of the force F ₂ based on the difference between the brake cylinder pressure and the master cylinder pressure and the elastic force F ₃ of the spring 136 is applied to the valve element 130. The attractive force F ₁ based on the magnetic force of the solenoid 134 acts in the opposite direction. The differential pressure F ₂ between the brake cylinder pressure and the master cylinder pressure is larger when the elastic force F ₃ is the same and when the suction force F ₁ is large than when the suction force F ₁ is small. These differential pressures are controlled.
As shown in FIG. 3, a check valve 144 and a relief valve 146 are provided in parallel with the pressure control valve 120. The check valve 144 prevents the flow of hydraulic fluid from the brake cylinder 18 to the master cylinder 14, but allows reverse flow, and even if the pressure control valve 120 is abnormal, The flow of hydraulic fluid toward the brake cylinder 18 is allowed. The relief valve 146 allows the flow of hydraulic fluid from the brake cylinder side to the master cylinder side when the hydraulic pressure on the brake cylinder side becomes higher than the relief pressure on the master cylinder side. Can be avoided.
In the present embodiment, the pressure control valve 120, the reservoir 98, the pump 106, and the like constitute the hydraulic pressure control unit 20.

As shown in FIG. 5, the brake ECU 24 is mainly configured by a computer including a PU (processing unit), a ROM, a RAM, an I / O circuit, and a bus connecting them. In addition to the booster negative pressure sensor 78 and the master cylinder pressure sensor 79, a brake switch 156, a wheel speed sensor 158, and the like are connected to the input side of the brake ECU 24. The wheel speed sensor 158 is provided for each wheel, and outputs a wheel speed signal that defines the wheel speed of each wheel.
A pump motor 160 that drives the pump 106 is connected to the output side of the brake ECU 24 via a drive circuit 162. Further, the drive circuit 164 of the solenoid 134 of the pressure control valve 120, the drive circuits 168 of the solenoids 166 of the pressure increasing valve 90 and the pressure reducing valve 100 (a plurality of solenoids 166 and the drive circuit 168 are shown together in the figure. Is also connected. A current control signal for linearly controlling the magnetic force of the solenoid 134 is output to the drive circuit 164 of the solenoid 134, while each drive circuit 168 of each solenoid 166 such as the pressure increasing valve 90 is connected to the solenoid 166. An ON / OFF drive signal for ON / OFF drive is output. In FIG. 5, the connection on the output side of the brake ECU 24 is also representatively shown for the first brake system, and the illustration for the second brake system is omitted.
The brake ECU 24 and the EFI-ECU 40 are connected via a CAN (Car Area Network) 170, and various information is communicated.

A plurality of programs, tables, and the like are stored in the ROM of the brake ECU 24, and booster effect characteristic control (hereinafter simply referred to as effect characteristic control), antilock control, and the like are executed in accordance with these programs.
The pressure increasing valve 90 and the pressure reducing valve 100 are controlled to open and close in accordance with an antilock control routine, but the description of the antilock control is omitted.
The effect characteristic control means that the booster 12 has an assist limit, and the hydraulic pressure of the brake cylinder 18 is such that the vehicle body deceleration increases with substantially the same gradient regardless of before and after the assist limit of the booster 12. Refers to control.
When the booster 12 increases the brake operation force to a certain value, the pressure in the variable pressure chamber 70 is fully increased to the atmospheric pressure and reaches the assist limit. After the assist limit, the booster 12 cannot boost the brake operation force, so if no measures are taken, the braking effect, that is, the same brake, as shown in the graph of FIG. The height of the brake cylinder pressure P _W corresponding to the operating force F is lower than the height of the brake cylinder pressure P _W when it is assumed that there is no assist limit. The effect characteristic control is performed by paying attention to such a fact. Specifically, as shown in the graph of FIG. 6B, the pump 106 is operated after the booster 12 reaches the assisting limit. Thus, a hydraulic pressure higher than the master cylinder pressure P _M by a differential pressure ΔPa is generated in the brake cylinder 18, thereby stabilizing the braking effectiveness regardless of the assisting limit of the booster 12. Here, the relationship between the differential pressure ΔPa (target differential pressure) and the master cylinder pressure P _M is stored in advance in the ROM, and is represented, for example, by the graph in FIG.
6D shows the relationship between the current supplied to the solenoid 134 of the pressure control valve 120 and the target differential pressure ΔPa, and this relationship is also stored in the ROM in advance.

In this embodiment, as shown in FIG. 7 (a), the brake pedal 10 is in a non-operating state (including a state immediately before the operation. The non-operating state of the brake pedal 10 is one of the standard states described in the claims. Therefore, the booster negative pressure in the non-operating state of the brake pedal 10 can also be referred to as a steady state, and the pressure P of the master cylinder when the booster 12 reaches the assisting limit. The relationship with _MB (hereinafter referred to as hydraulic pressure at the assistance limit) is stored in advance. These relationships are set in common for many vehicles. As shown in FIG. 7 (b), when the booster negative pressure in the standard state approaches the atmospheric pressure, the hydraulic pressure at the assisting limit when the booster 12 reaches the assisting limit is reduced. There is a relationship expressed as a model.
The booster negative pressure in the standard state (non-operating state of the brake pedal 10) is detected, and based on the booster negative pressure and the relationship shown in FIG. 7 (a), the assist limit hydraulic pressure _PMB is acquired, and the master cylinder pressure sensor When the actual master cylinder pressure P _M detected by 79 reaches the assist limit hydraulic pressure P _MB , the booster 12 reaches the assist limit, the pump 106 is activated, and the pressure control valve 120 is (Effective characteristic control is started).

Further, the relationship shown in FIG. 7A is corrected by learning.
The relationship shown in FIG. 7 (a) is the same for a number of vehicles, but may actually differ for each vehicle. For example, there may be differences due to mechanical variations in the characteristics of the booster 12 and the master cylinder 14, variations in characteristics of the booster negative pressure sensor 78 and the master cylinder pressure sensor 79, A / D conversion errors in the brake ECU 24, and the like. It is. In addition, the characteristics of the booster negative pressure sensor 78 and the master cylinder hydraulic pressure sensor 79 may change over time, and the relationship may change over time.
In any case, when the relationship stored in advance is different from the actual relationship, it cannot be accurately detected that the booster 12 has reached the assistance limit, and before the assistance limit is actually reached, There is a problem that the brake feeling of the driver is lowered because the effect characteristic control is started or may be started after the assist limit is actually reached.
Therefore, in the present embodiment, an actual relationship (hereinafter sometimes referred to as an actual relationship) is acquired, and a previously stored relationship (hereinafter also referred to as a common relationship) is corrected.

In this embodiment, (i) the booster negative pressure has decreased from the standard state by a set change amount (hereinafter referred to as a set decrease amount) or more, and (x) the booster negative pressure decrease gradient has become smaller than the first set value. (Y) The booster 12 has reached the assisting limit when the three conditions that the increase gradient of the master cylinder hydraulic pressure has become smaller than the second set value are satisfied.
Then, the actual hydraulic pressure of the master cylinder 14 is detected when it is detected that the booster 12 has reached the assisting limit, and a plurality of pairs with the actually detected booster negative pressure in the standard state are acquired. Based on the set, the actual relationship is acquired, and the pre-stored common relationship is corrected. For example, a regression coefficient is obtained based on a plurality of these sets, an approximate straight line is obtained, and the approximate straight line can be a real relationship.

Regarding (i) When the brake pedal 10 is operated and the power piston 66 is moved forward, the volume of the negative pressure chamber 68 decreases, and the booster negative pressure approaches atmospheric pressure (PV = from a constant relationship). Further, as shown in FIG. 9, the amount of decrease in the booster negative pressure until the booster 12 reaches the assist limit may increase as the booster negative pressure in the non-operating state (steady state) of the brake pedal 10 is closer to vacuum. Are known. Therefore, in this embodiment, as shown in FIG. 8, the relationship between the booster negative pressure in the standard state (steady state) and the amount of decrease in the booster negative pressure until the assist limit is reached is obtained in advance by experiments or the like. It is remembered. Accordingly, when the booster negative pressure decrease amount ΔP _B becomes _{equal to} or greater than the set decrease amount ΔP _Bth determined by the standard booster negative pressure <P _B0 > and the relationship shown in FIG. 8, the booster 12 reaches the assisting limit. Can be reached.
When the brake pedal 10 is not operated, the booster negative pressure P _B is detected at predetermined time intervals, and the average value of the booster negative pressure P _B is acquired. When the start of the operation of the brake pedal 10 is detected, the average value acquired immediately before is set as the booster negative pressure <P _B0 > in the standard state.
About (x) As shown in FIG. 9, when the booster 12 reaches the assisting limit, the boosting effect is lost. Therefore, when the assisting limit is reached in the normal operating state of the driver, the increasing speed of the stroke of the brake pedal 10 is increased. It decreases rapidly. The increasing speed of the strokes of the brake pedal 10 and the power piston 66 is reduced, and the decreasing gradient of the booster negative pressure is reduced. Therefore, it can be assumed that the booster 12 reaches the assisting limit when the decreasing gradient (dP _B / dt) of the booster negative pressure becomes smaller than the first setting gradient (B _th ).
(y) For the same reason, in the master cylinder 14, the increasing gradient of the stroke of the pressurizing piston 66 becomes small, so the increasing gradient of the hydraulic pressure in the pressurizing chamber 61 becomes abruptly small. Therefore,
It can be assumed that the booster 12 reaches the assisting limit when the increase gradient (dP _B / dt) of the master cylinder hydraulic pressure becomes smaller than the second set value (M _th ).
Note that the first set value B _th and the second set value M _th are predetermined fixed values in this embodiment, and the brake pedal 10 is operated in a normal state by a standard driver. As a result, it was determined based on values obtained in advance through experiments and simulations.

The hydraulic pressure of the brake cylinder is controlled according to the execution of the brake hydraulic pressure control program represented by the flowchart of FIG.
In step 1 (hereinafter abbreviated as S1. The same applies to other steps), it is determined whether or not the brake switch 156 is in the ON state. When the brake pedal 10 is not depressed, the booster negative pressure is detected by the booster negative pressure sensor 78 in S2-5, the average value is acquired, and the booster negative pressure <P _B0 > in the standard state is obtained. . Then, according to the relationship shown in FIG. 7, the assist limit hydraulic pressure _PMB is determined. Further, the pressure control valve 120 is turned off, and the pump 106 is stopped. In non-operated state of the brake pedal 10, S1～5 are repeated, always been acquired latest boosting limit at pressure P _MB, become stored as it.
While S1~5 is repeatedly executed, the brake pedal 10 is depressed, the brake switch 156 is turned ON, in S6, the master cylinder pressure P _M is detected by the master cylinder pressure sensor 79, at S7, assisting whether it is above the limit at pressure P _MB is determined. Boosting when the limit time of pressure P _MB smaller, in S5, the pressure control valve 120 is set to the OFF, the pump 106 is stopped. If the actual master cylinder pressure P _M becomes equal to or greater than the assist limit hydraulic pressure P _MB while S1, 6, 7, and 5 are repeatedly executed, the determination in S7 becomes YES, and in S8, the actual master cylinder pressure P _{Based on M} and the relationship shown in FIG. 6C, the target differential pressure ΔPa is acquired. In S9, the supply current amount IP _M to the pressure control valve 120 is acquired according to the relationship shown in FIG. In S10, the pressure control valve 120 is controlled accordingly, and the pump 106 is operated.
Thereby, the brake cylinder hydraulic pressure, that is, the deceleration can be increased after the boost limit of the booster 12 with the same gradient as before the boost limit.

Next, relationship learning will be described.
By executing the relationship learning program represented by the flowchart of FIG. 11, the actual relationship is acquired once. Once acquired, it is possible to correct the difference caused by the variation of individual vehicles.
In S21, it is detected that the booster 12 has reached the assist limit. Then, the master cylinder pressure in that case is detected, and a set of the master cylinder pressure P _M and the standard booster negative pressure <P _B0 > is stored.
Specifically, as shown in the flowchart of FIG. 12, it is determined in S51 whether or not the brake switch 156 is in an ON state. If the brake switch 156 is in an OFF state, the booster negative pressure sensor 78 causes a booster in S52. The negative pressure P _B is detected, and in S53, the average value is acquired and set to the booster negative pressure <P _B0 > in the standard state. In S54, the set decrease amount ΔP _Bth is acquired according to FIG. While the brake switch 156 is in the OFF state, S51 to S54 are repeatedly executed, and the latest standard state negative pressure <P _B0 > and the set decrease amount ΔP _Bth are acquired and stored. In S55, flags 1 to 3 are reset.
If the brake switch 156 is switched to the ON state during the repeated execution of S51 to S55, the determination in S51 is YES, and in S56, the booster negative pressure P _B is acquired, and the negative pressure in the standard state <P _B0 > A decrease amount ΔP _B is acquired, a decrease gradient dP _B / dt with respect to time is acquired, and a decrease gradient change amount ΔdP _B is acquired.
ΔP _B = <P _B0 > −P _B
dP _B / dt = {P _{B (n−1)} −P _{B (n)} } / Δt
In the above equation, Δt is the cycle time of this program.
ΔdP _B = (dP _B / dt) _n − (dP _B / dt) _n−1
When S56 is first executed, the decrease gradient dP _B / dt and the decrease gradient change amount ΔdP _B are not acquired.

Next, in S57, the master cylinder pressure P _M is detected, the increasing gradient dP _M / dt _(n) with respect to time is acquired, and the change amount ΔdP _M of the increasing gradient is acquired.
dP _M / dt = {P _{M (n−1)} −P _{M (n)} } / Δt
ΔdP _M = (dP _M / dt) _n − (dP _M / dt) _n−1
In S58, it is determined whether or not the booster negative pressure decrease amount ΔP _B is larger than the set decrease amount ΔP _Bth acquired in S54.
ΔP _B > ΔP _Bth
When the decrease amount ΔP _B is larger than the set decrease amount ΔP _Bth, it is determined that the condition (i) is satisfied, and the flag 1 is set in S59. If the condition (i) is not satisfied, S59 is not executed.
In S60, it is determined whether or not the booster negative pressure decreasing gradient dP _B / dt has become smaller than the first set value B _th .
ΔdP _B > B _th
When it becomes smaller than the first set value, it is assumed that the condition (x) is satisfied, and the flag 2 is set in S61. If it is not smaller than the first set value, the flag 2 is not set and S62 is executed.
In S62, it is determined whether or not the increase gradient dP _M / dt of the master cylinder pressure has become smaller than the second set value M _th .
ΔdP _M > M _th
When it becomes smaller than the second set value, it is assumed that the condition (y) is satisfied, and the flag 3 is set in S63.

In S64, it is determined whether or not all the flags 1 to 3 are set. If all are set, conditions (i), (x), (y) are met and the assistance limit is reached. In S65, a set of the negative pressure <P _B0 > in the standard state and the master cylinder hydraulic pressure P _M (the value detected in S57 when the determination in S62 is YES) is stored, and flags 1 to 3 are stored. Reset.
Conditions (i), (x), and (y) are not always satisfied at the same time. In addition, after reaching the assisting limit, the change in the change gradient of the booster negative pressure PB and the master cylinder pressure PM becomes small. Therefore, when the determination of S60, 62 becomes “YES” once, it is executed for the second and subsequent times. Is “NO”. Therefore, flags 1 to 3 are provided so that it is possible to detect that the assist limit has been reached even if all of the conditions (i), (x), and (y) are not satisfied at the same time. In addition, since flag 1-3 is reset when S65 is performed, after reaching the assistance limit, the determination of S64 will not be YES again.

In S22, it is determined whether or not the number of sets (P _M , <P _B0 >) acquired in this way has reached a predetermined number. If the number is smaller than the set number, the relationship is not corrected and S21 and S22 are repeatedly executed. If more than the set number of such sets are acquired, the determination in S22 is YES, and in S23, an approximate line is acquired based on a plurality of points, and an actual relationship is established. In S24, the common relationship is corrected to the actual relationship. For example, as shown in FIG. 7C, the common relationship (solid line) is corrected to the real relationship (dashed line).
Based on the actual relationship after the modification, it is possible to accurately obtain the boosting limit at pressure P _MB, it is possible to booster 12 is accurately obtain that you have reached the boosting limit. As a result, the effect characteristic control can be started at an appropriate time, and a decrease in the brake feeling of the driver can be suppressed.

  As described above, in the present embodiment, the brake hydraulic pressure control device is configured by the hydraulic pressure control unit 20, the part that stores the brake hydraulic pressure control program represented by the flowchart of FIG. Is done. Further, a relationship learning unit is configured by a portion that stores the relationship learning program represented by the flowchart of FIG. The assistance limit detection device is configured by a part that stores S21 and a part that executes S21 in the relation learning unit. The assistance limit detection device is also a multiple condition detection unit. Further, the ROM of the brake ECU 24 constitutes a storage unit that stores the relationship.

In the above embodiment, the booster 12 has reached the assisting limit when the three conditions (i), (x), and (y) are satisfied. However, the conditions (i) and ( It is also possible to reach the assist limit when both x) and (y) are satisfied, or reach the assist limit when condition (i) is satisfied.
The actual relationship can also be acquired based on one set. For example, a straight line that passes through the origin and one actually acquired point is an actual relationship, or a straight line that passes through the actually acquired point and has the same inclination as a straight line that represents a common relationship (a parallel straight line) is the actual relationship. You can also.
Furthermore, the actual relationship can be acquired periodically. For example, when a real relationship acquisition condition such as every several days, every few months, every few years, or the like is satisfied, the execution of the relationship learning program is started and the actual relationship is acquired. In the present embodiment, the relationship stored in advance at that time is appropriately corrected to the newly acquired actual relationship.
In addition, the actual relationship can be acquired before the vehicle is shipped. In that case, the actual relationship is stored in advance in the storage unit.
Further, when the newly acquired actual relationship is within a predetermined setting range with respect to the relationship already stored at that time, the relationship can be prevented from being changed.
Moreover, the estimated value estimated based on the operating state of the engine 30 can also be employ | adopted for the booster negative pressure of a standard state.
In addition to the above-described embodiments, the present invention can be carried out in various modifications and improvements based on the knowledge of those skilled in the art.

1 is a view schematically showing a hydraulic brake system including a brake operation device according to an embodiment of the present invention together with an engine system. FIG. It is side surface sectional drawing which shows the booster and master cylinder which comprise the said hydraulic brake system. It is a circuit diagram which shows the said hydraulic brake system. It is a figure for demonstrating the structure and action | operation of a pressure control valve which comprise the said hydraulic brake system. It is a block diagram which shows the electric constitution of the said hydraulic brake system. (a) It is a graph which shows the relationship between the brake operation force and brake cylinder pressure in the said hydraulic brake system. (b) It is a graph for demonstrating brake effect characteristic control. (c) is a graph showing the relationship between the master cylinder pressure and the hydraulic pressure difference between the master cylinder and the brake cylinder in the brake effect characteristic control, and is stored in the ROM of the computer of the brake ECU constituting the hydraulic brake system. ing. (d) is a graph showing the relationship between the master cylinder pressure and the amount of current supplied to the solenoid of the pressure control valve, and is stored in the ROM. (a) It is a figure showing the relationship between the booster negative pressure of the normal state memorize | stored in the said ROM, and the hydraulic pressure at the time of assistance limit. (b) It is a figure which shows the relationship between a pedal effort and a master cylinder pressure in the said hydraulic brake system. (c) It is a figure which shows the relationship (common relationship) memorize | stored previously, and the relationship (actual relationship) after correction | amendment. It is a figure which shows the relationship between the booster negative pressure of the normal state memorize | stored in the said ROM, and the fall amount of the booster negative pressure until it reaches the assistance limit. It is a figure which shows the change state of a booster negative pressure, and the change of a master cylinder pressure. It is a flowchart which shows the brake fluid pressure control routine memorize | stored in the said ROM. It is a flowchart which shows the relationship learning routine memorize | stored in the said ROM. It is a flowchart which shows execution of a part (S21) of the said relationship learning routine.

Explanation of symbols

  10: Brake pedal 12: Booster 14: Master cylinder 24: Brake ECU 68: Negative pressure chamber 78: Master cylinder pressure sensor 79: Booster negative pressure sensor 120: Pressure control valve

Claims (4)

A brake operating member;
(a) a power piston linked to the pressurizing piston of the master cylinder, (b) a negative pressure chamber in front of the power piston and a variable pressure chamber in the rear, and (c) the variable pressure chamber, the power piston and the A vacuum booster comprising a control valve that selectively communicates with the negative pressure chamber and the atmosphere in association with relative movement with the brake operation member;
At least the pressure in the negative pressure chamber is equal to or greater than the set change amount determined by the pressure in the standard state from the pressure in the standard state where the vacuum booster is in a predetermined state before the operation of the brake operation member is started. And a boost limit detecting device for detecting that the vacuum booster has reached the support limit when approaching to. The assist limit detecting device includes: (a) a booster negative pressure sensor that detects a booster negative pressure that is a pressure in the negative pressure chamber; and (b) a master cylinder hydraulic pressure sensor that detects a hydraulic pressure of the master cylinder; of the detected booster negative pressure by c) (i) the booster negative pressure sensor, in addition to lowering the amount from the value in the standard state of the vacuum booster is equal to or greater than the set variation, (ii) (x ) A decrease gradient with respect to time of the booster negative pressure detected by the booster negative pressure sensor has become smaller than a first set value; and (y) a time of hydraulic pressure of the master cylinder detected by the master cylinder hydraulic pressure sensor. A multi-condition detection unit that detects that the vacuum booster has reached the assisting limit when at least one of the increase gradient with respect to the current value is smaller than a second set value is satisfied. Item 4. The booster device according to Item 1.   The assisting limit detection device includes a setting change amount determining unit that determines the set change amount to a smaller value when the pressure of the negative pressure chamber in the standard state is close to atmospheric pressure than when it is close to vacuum. 3. The booster device according to 1 or 2. A booster device according to any one of claims 1 to 3,
A brake cylinder connected to the master cylinder;
Power hydraulic pressure source,
After the vacuum booster reaches the assist limit, the power fluid is adjusted so that the increasing gradient of the hydraulic pressure of the brake cylinder with respect to the operating force applied to the brake operating member is the same before and after the vacuum booster reaches the assist limit. A brake hydraulic pressure control device that controls the hydraulic pressure of the brake cylinder by using the hydraulic pressure of a pressure source, wherein the vacuum booster reaches a pressure limit and the pressure of the negative pressure chamber in the standard state of the vacuum booster. A storage unit for storing the relationship with the hydraulic pressure at the assisting limit, which is the hydraulic pressure of the master cylinder when it has reached, the pressure of the negative pressure chamber in the standard state actually acquired, and the relationship When the hydraulic pressure at the assist limit is acquired and the actual hydraulic pressure of the master cylinder reaches the hydraulic pressure at the assist limit, the hydraulic pressure control of the brake cylinder is performed. A hydraulic brake system including a brake fluid pressure control device for start,
The brake fluid pressure control device detects that the vacuum booster has reached the assist limit by the assist limit detection device and the pressure of the negative pressure chamber in the standard state actually acquired in the storage unit. A hydraulic brake device comprising: a relationship storage unit for storing an actual relationship acquired based on at least one set of the actual hydraulic pressure of the master cylinder.

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