JPH11321621A - Brake pedal stroke simulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a secular change caused by wear and adjust a hysteresis characteristic independently from other characteristics, regarding a brake stroke simulator realizing the hysteresis characteristic. SOLUTION: A liquid chamber 50 is demarcated between a piston 42 and a damper 48 which are provided so as to be slidable within a cylinder 40. Pedal working force is transmitted to the piston 42. The liquid chamber 50 is partitioned into a first liquid chamber 60 on the side of the piston 42 and a second liquid chamber 62 on the side of the damper 48 by a valve mechanism 53 and a cup seal 58. The cup seal 58 allows flow of hydraulic fluid from the first liquid chamber 60 to the second liquid chamber 62 when the first liquid chamber 60 has higher pressure than that of the second liquid chamber 62. The valve mechanism 53 is constituted of a valve body 70 and a valve spring 72 and allows flow of hydraulic fluid from the second liquid chamber 62 to the first liquid chamber 60 when the differential pressure reaches prescribed valve opening pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a brake pedal stroke simulator, and more particularly to a brake pedal stroke simulator capable of realizing hysteresis characteristics.

[0002]

2. Description of the Related Art As a vehicle brake control device, there is known an electronically controlled brake device which electrically detects an operation amount of a brake pedal and controls a hydraulic pressure supplied to a wheel cylinder based on the detected value. . In the electronically controlled brake device, the master cylinder and the wheel cylinder are normally shut off from each other, so that even when the brake operation is performed, the hydraulic oil does not flow from the master cylinder to the wheel cylinder. Therefore, in order to obtain a pedal stroke corresponding to the pedal depression force, the electronically controlled brake device must
A brake pedal stroke simulator is provided.

In a brake control device having a brake booster and supplying a hydraulic pressure generated in the brake booster in response to a brake operation to a wheel cylinder, the relationship between the pedaling force and the braking force is determined by the characteristics of the brake booster. Is accompanied by hysteresis. That is, when the pedal effort is reduced from the state in which the brake pedal is depressed, the brake force decreases with a delay with respect to the decrease in the pedal effort. According to such hysteresis characteristics, after the brake pedal is depressed, the braking force is maintained even when the pedaling force is reduced,
Good brake feeling can be obtained. Therefore, also in the electronically controlled brake device, it is desirable to simulate the above-mentioned hysteresis characteristics using a brake pedal stroke simulator.

[0004] As a brake pedal stroke simulator capable of simulating such a hysteresis characteristic, a configuration disclosed in, for example, Japanese Patent Application Laid-Open No. 6-211124 is known. The brake pedal stroke simulator includes a piston slidably provided in a housing, a liquid chamber defined by the piston and communicating with the master cylinder, and a spring member for urging the piston in a direction to reduce the liquid chamber. It has. When the master cylinder pressure rises with the brake operation, an amount of hydraulic oil corresponding to the pedal stroke flows into the liquid chamber. The piston is displaced while contracting the spring member according to the inflow amount of the hydraulic oil. At this time, the liquid pressure in the liquid chamber increases due to the elastic force generated due to the contraction deformation of the spring member. Then, the hydraulic pressure generated in the liquid chamber is transmitted to the brake pedal via the master cylinder, so that a pedal depressing force corresponding to the hydraulic pressure is generated.

[0005] In the above-mentioned conventional stroke simulator, the spring member is formed by stacking a plurality of disc springs. In the process of expanding and contracting the spring members, the respective disc springs slide against each other, thereby generating sliding resistance. When the spring member is restored from the contracted deformation state, that is, when the depression of the brake pedal is released, the restoring deformation of the spring member is hindered by the sliding resistance between the disc springs. Under the influence of the sliding resistance, the relationship between the pedal depression force and the pedal stroke changes between when the brake pedal is depressed and when the depression is released, whereby a hysteresis characteristic is generated in the relationship between the pedal stroke and the pedal depression force. You. Therefore, for example, by generating a braking force according to the pedal stroke,
A relationship between the pedal effort and the braking force with hysteresis characteristics can be realized. The hysteresis characteristic changes according to the sliding resistance between the disc springs. Therefore,
The hysteresis characteristic can be adjusted by changing the number of disc springs constituting the spring member and changing the sliding resistance of the entire spring member.

[0006]

As described above, in the conventional brake pedal stroke simulator,
Hysteresis characteristics are realized by the sliding resistance between the disc springs. For this reason, the disc spring may be worn due to the sliding, and the hysteresis characteristic may change with time.

In the conventional brake pedal stroke simulator, the gradient of the relationship between the pedal depression force and the pedal stroke is determined by the spring constant of the spring member.
Therefore, when the number of disc springs is changed to adjust the hysteresis characteristics, the gradient of the relationship between the pedal depression force and the pedal stroke changes because the spring constant of the spring member changes. That is, it is difficult to independently adjust only the hysteresis characteristic in the conventional brake pedal stroke simulator.

[0008] The present invention has been made in view of the above points, and a brake pedal stroke capable of preventing a temporal change due to wear and the like and capable of independently adjusting a hysteresis characteristic. The purpose is to provide a simulator.

[0009]

The above object is achieved by the present invention.
As described in the above, a piston member for transmitting pedal depression force in a predetermined direction, and a damper provided separately from the piston member in the predetermined direction and urged in a direction opposite to the predetermined direction A brake pedal stroke simulator comprising a member, a liquid chamber defined between the piston member and the damper member, and filled with hydraulic oil, wherein the liquid chamber includes a liquid chamber adjacent to the piston member. A first fluid chamber and a second fluid chamber adjacent to the damper member, the first fluid chamber having a first valve opening pressure, and hydraulic fluid from the first fluid chamber to the second fluid chamber. A first one-way valve that allows only the flow of fluid and a second valve that has a second valve opening pressure and allows only the flow of hydraulic oil from the second liquid chamber to the first liquid chamber. A one-way valve, and the first valve opening pressure and the second valve opening pressure The sum of al is achieved by the brake pedal stroke simulator set the to be a predetermined positive value.

In the present invention, when the pedal depression force is transmitted to the piston member, the hydraulic pressure in the first liquid chamber (hereinafter, referred to as the first hydraulic pressure) increases. When the first hydraulic pressure exceeds the first valve opening pressure, the first one-way valve allows a flow of hydraulic oil from the first hydraulic chamber to the second hydraulic chamber. For this reason, when the first hydraulic pressure rises beyond the first valve opening pressure, the hydraulic pressure of the second hydraulic chamber (hereinafter, referred to as the hydraulic pressure of the second hydraulic chamber)
The second hydraulic pressure is increased in a state where the first hydraulic pressure is lower by the first valve opening pressure than the first hydraulic pressure. When the pedal depression force decreases after the second fluid chamber rises, the first fluid pressure decreases. In this case, when the pressure difference between the first liquid chamber and the second liquid chamber is lower than the first valve opening pressure, the first one-way valve moves from the first liquid chamber to the second liquid chamber. Block the flow of hydraulic oil to the Meanwhile, the first
Until the hydraulic pressure becomes lower by the second valve opening pressure than the second hydraulic pressure, the second one-way valve controls the flow of the hydraulic oil from the second hydraulic chamber to the first hydraulic chamber. Not allowed. For this reason, after the pedal depression force decreases, the flow of the hydraulic oil between the first liquid chamber and the second liquid chamber is prohibited, so that the second hydraulic pressure is kept constant.

When the pedal depression force decreases until the first hydraulic pressure becomes lower than the second hydraulic pressure by the second valve opening pressure, the second one-way valve thereafter moves from the second hydraulic chamber to the first hydraulic pressure. To allow the flow of hydraulic oil to the liquid chamber. Therefore, when the first hydraulic pressure further decreases, the second hydraulic pressure decreases in a state where the second hydraulic pressure is higher than the first hydraulic pressure by the second valve opening pressure. As described above, when the pedal depression force decreases, the first hydraulic pressure is changed from the state in which the first hydraulic pressure is higher by the first valve opening pressure than the second hydraulic pressure to the first hydraulic pressure is higher than the second hydraulic pressure. Until the second valve opening pressure reaches a low pressure state,
The second hydraulic pressure is kept constant. That is, after the brake depression force starts to decrease, the second hydraulic pressure is kept constant until the first hydraulic pressure decreases by a pressure corresponding to the sum of the first valve opening pressure and the second valve opening pressure. The first valve opening pressure and the second valve opening pressure are set such that their sum becomes a positive predetermined value. Therefore, the relationship between the first hydraulic pressure and the second hydraulic pressure has a hysteresis characteristic in which the above-mentioned predetermined value is a hysteresis amount.

The damper member is provided in the predetermined direction (that is,
(The direction in which the pedaling force is transmitted). For this reason, when the second hydraulic pressure increases, the damper member is displaced in a direction opposite to the predetermined direction, while when the second hydraulic pressure decreases, the damper member is displaced in the predetermined direction. When the damper member is displaced, the piston member is also displaced in the same direction. Therefore, the second
A pedal stroke occurs according to the change in the hydraulic pressure. Further, as described above, the first hydraulic pressure has a value corresponding to the pedaling force. Therefore, since the relationship between the first hydraulic pressure and the second hydraulic pressure has a hysteresis characteristic, the relationship between the pedal depression force and the pedal stroke also has the hysteresis characteristic.

As described above, in the present invention, the hysteresis characteristic is generated by the opening pressure of the first one-way valve and the second one-way valve. Generally, the valve opening pressure of a one-way valve is set by the elastic force of a spring. Therefore, according to the present invention, the hysteresis characteristic can be realized without causing a sliding portion. Further, the opening pressures of the first one-way valve and the second one-way valve are not related to characteristics of the brake pedal stroke simulator other than the hysteresis characteristics. Therefore, according to the present invention, only the hysteresis characteristic can be adjusted independently and arbitrarily.

[0014] The above object is also achieved by a brake pedal stroke simulator as set forth in claim 1, wherein an operation amount detecting means for detecting a brake operation amount and a brake operation amount based on the brake operation amount. A hydraulic control unit for controlling a wheel cylinder pressure using a predetermined high pressure source as a hydraulic pressure source, the brake control device being provided in a brake control device, for connecting the first liquid chamber or the second liquid chamber to the wheel cylinder; This is further effectively achieved by a brake pedal stroke simulator including a passage, a shutoff valve provided in the communication passage, and a valve opening means for opening the shutoff valve when a system fails.

In the present invention, the brake pedal stroke simulator includes a communication passage connecting the first liquid chamber or the second liquid chamber to the wheel cylinder, and a shutoff valve provided in the communication passage. The failure opening means opens the shut-off valve when the system fails. When the shutoff valve is opened, the first
Hydraulic pressure or a second hydraulic pressure is supplied to the wheel cylinder. Therefore, if a system failure occurs, the wheel cylinder pressure will increase to the first
The pressure is increased by using the liquid chamber or the second liquid chamber as a liquid pressure source. That is, in the present invention, the brake pedal stroke simulator also has a function as a master cylinder.

[0016]

FIG. 1 is a system configuration diagram of a brake control device to which a brake pedal stroke simulator 10 (hereinafter, abbreviated as stroke simulator 10) according to an embodiment of the present invention is applied. The brake control device is controlled by an electronic control unit 12 (hereinafter, referred to as ECU 12).

As shown in FIG. 1, a brake pedal 16 is connected to the stroke simulator 10 via a push rod 14. Stroke simulator 10
Generates a hydraulic pressure in accordance with the pedal depression force applied to the brake pedal 14 (hereinafter, referred to as a pedal depression force F). The configuration and operation of the stroke simulator 10 will be described later in detail.

The brake control system, hydraulic (hereinafter referred to as a stroke simulator pressure P _ST) to the stroke simulator 10 generates hydraulic pressure sensor 18 for detecting the, and, the pedal stroke of the brake pedal 16 (hereinafter, the pedal stroke S ) Is provided. Hydraulic pressure sensor 18 and stroke sensor 20
Are supplied to the ECU 12. ECU12
Detects a stroke simulator pressure _PST and a pedal stroke S based on output signals supplied from the hydraulic pressure sensor 18 and the stroke sensor 20.

The brake control device also includes a hydraulic actuator 22. A hydraulic pump 24 and a wheel cylinder 26 provided for each wheel are connected to the hydraulic actuator 22. The hydraulic actuator 22 incorporates a hydraulic circuit including an electromagnetic valve (not shown). Each solenoid valve provided in the hydraulic actuator 22 is driven according to a control signal supplied from the ECU 12. The hydraulic actuator 22 controls the hydraulic pressure of the wheel cylinder 26 (hereinafter referred to as the wheel cylinder pressure P _{W / C} ) by using the hydraulic pump 24 as a hydraulic pressure source by appropriately driving each electromagnetic valve.

Each stroke simulator 10 includes
A hydraulic passage 28 leading to the cylinder 26 communicates with the hydraulic cylinder 28. liquid
An electromagnetic on-off valve 30 is provided in the pressure passage 28. electromagnetic
The on-off valve 30 is normally closed, and is turned off by the ECU 12.
The two positions of the valve that will open when supplied with the
It is a solenoid valve. In this embodiment, normally, the ECU
12 is the stroke simulator pressure P _STHydraulic pressure according to
The hydraulic actuator is supplied to the wheel cylinder 26.
The control signal is output to each solenoid valve of the eta 22. Up
As described above, the stroke simulator 10 has the pedaling force F
Stroke simulator pressure P according to_STOccurs. Obedience
Therefore, according to the control described above, the wheel corresponding to the pedaling force F
Cylinder pressure P_{W / C}With normal braking equipment
Function is realized. Hereinafter, the brake control device
To achieve the function of a normal brake device
Is referred to as normal brake control.

In the brake control device of this embodiment, in addition to the normal brake control, the ECU 12 controls the hydraulic actuator 22 based on various information on the slip state of the wheels, the deceleration of the vehicle, the yaw rate, etc. Anti-lock brake control (ABS) to prevent wheel lock, traction control (TRC) to prevent wheel slippage due to excessive driving torque, and vehicle stabilization control to prevent unstable vehicle behavior ( V
SC), etc., can be realized.

In a conventional brake device having a brake booster (hereinafter referred to as a booster type brake device), a hydraulic pressure generated in the brake booster in accordance with a pedal depression force is supplied to a wheel cylinder, and the hydraulic pressure is applied to the hydraulic cylinder. A corresponding braking force is generated. According to such a booster type brake device, the relationship between the pedal depression force and the braking force (hereinafter, referred to as the depression force-braking force relationship) has a hysteresis characteristic due to the characteristics of the brake booster. FIG. 2 shows an example of a pedaling force-braking force relationship with a hysteresis characteristic.

According to the relationship between the pedaling force and the braking force shown in FIG. 2, when the pedaling force is reduced after the brake pedal is depressed, the braking force decreases after the pedaling force decreases by a certain amount of hysteresis F _HYS. To start. Therefore, for example, when the driver depresses the brake pedal and then depresses the pedal depression force, the braking force is maintained, so that the sense of application of the brake is increased and a good brake feeling can be obtained.

In general, when a driver intends to obtain a desired brake force, it is considered that the brake force is often adjusted by depressing a brake pedal by an appropriate amount and then relaxing the pedal force. In this case, according to the pedaling force-braking force relationship shown in FIG. 2, the braking force does not change sensitively with the decrease in the pedaling force, so that the driver can easily adjust the braking force.

It is desirable that the hysteresis amount F _HYS in the above-described pedal force-brake relationship can be adjusted so as to realize an optimum brake feeling. In the booster type brake device, the amount of hysteresis F _HYS can be adjusted by the hardness of the reaction disk provided in the brake booster, the shape of the control valve, and the like.

The brake control apparatus according to the present embodiment simulates the pedaling force-braking force relationship with the hysteresis characteristic as described above by using the brake simulator 10.
It is characterized in that good brake feeling similar to that of the booster type brake device can be obtained, and that the amount of hysteresis can be adjusted independently without affecting other characteristics of the stroke simulator 10. doing. Hereinafter, the configuration and operation of the stroke simulator 10 will be described.

FIG. 3 is a configuration diagram of the stroke simulator 10. As shown in FIG. 3, the stroke simulator 10 includes a cylinder 40. A piston 42 is provided inside the cylinder 40. A cup seal 46 is mounted around the piston 42. The cup seal 46 allows the piston 42 to slide inside the cylinder 40 in a liquid-tight state. The piston 42 has
The above-mentioned push rod 14 is connected. When a pedaling force F is applied to the brake pedal 16, the force is increased at a predetermined lever ratio and transmitted to the piston 42 via the push rod 14, whereby the piston 42 is displaced rightward in FIG. . Hereinafter, the direction in which the pedal effort F is transmitted to the piston 42 (ie, the rightward direction in FIG. 3) is referred to as a stepping direction, and the opposite direction is referred to as a stepping release direction. In the following description,
For simplicity, ignoring the lever ratio, the pedal depression force F corresponds to the force transmitted from the brake pedal 16 to the piston 42, and the pedal stroke S corresponds to the displacement amount of the piston 42 in the depression direction. It shall be.

A damper 48 is disposed inside the cylinder 40 to the right of the piston 42 in FIG. 3 in a liquid-tight and slidable manner. A liquid chamber 50 is defined between the piston 42 and the damper 48. Hydraulic oil is sealed in the liquid chamber 50. The damper 48 is urged by a damper spring 52 in a stepping release direction, that is, in a direction to reduce the liquid chamber 50.

A valve mechanism 53 is provided inside the liquid chamber 50. The valve mechanism 53 includes the valve housing 5
4 is provided. The valve housing 54 includes the cylinder 4
The cylinder 56 is fixed to the cylinder 40 so that a passage 56 is defined between the cylinder 40 and the inner wall of the cylinder 40. A cup seal 58 is provided in the passage 56. The valve mechanism 53 and the cup seal 58 partition the inside of the liquid chamber 50 into a first liquid chamber 60 adjacent to the piston 42 and a second liquid chamber 62 adjacent to the damper 48. The cup seal 58 allows the flow of the fluid from the first liquid chamber 60 to the second liquid chamber 62 when the liquid pressure in the first liquid chamber 60 is higher than the liquid pressure in the second liquid chamber 62. However, it functions as a one-way valve that always blocks the flow in the opposite direction. The liquid pressure of the second fluid chamber 62 is equivalent to the stroke simulator pressure P _ST described above. In addition, the above-described hydraulic passage 28 is connected to the second liquid chamber 62, and the valve housing 54 has a valve chamber 63 therein. The valve housing 54 also includes a port 64 for communicating the valve chamber 63 with the first liquid chamber 60, and a port 66 for communicating the valve chamber 63 with the second liquid chamber 62. A guide rod 68 is connected to the piston 42 described above. The guide rod 68 penetrates the port 64 and enters the valve chamber 63. A valve body 70 is disposed inside the valve chamber 63. The valve body 70 is held around the guide rod 68 in a liquid-tight and slidable manner. An inner wall surface around the port 66 of the valve housing 54 forms a valve seat 71 for the valve body 70.

The guide rod 68 has a projection 73 formed thereon. The projection 73 engages with the valve body 70 in a state where the depression of the brake pedal 16 is released, thereby displacing the valve body 70 to the left in FIG. 3 and in a state where the brake pedal 16 is depressed. , Are disposed so as to be separated from the valve body 70 to the right in the figure. For this reason, when the depression of the brake pedal 16 is released, the valve body 70 is separated from the valve seat 71, while when the brake pedal 16 is depressed, the valve body 70 is subjected to a predetermined load by the valve spring 72. (hereinafter, referred to as the valve load f _v) is pressed toward the valve seat 71. Therefore, when the brake pedal 16 is depressed, the port 66 is normally closed by the valve body 70 sitting on the valve seat 71.

A set spring 76 is provided between the valve housing 54 and the piston 42. Set spring 76 in a state where the brake pedal 16 is not depressed, the piston 42, a predetermined load on the depression release direction (hereinafter, referred to as set load f _s) is configured to exert a. Above the cylinder 40, a reservoir tank 78 for storing hydraulic oil is installed. The reservoir tank 78 communicates with a reservoir port 80 provided in the cylinder 40. The reservoir port 80 is arranged so as to be located slightly to the right in FIG. 3 with respect to the cup seal 46 when the brake pedal 16 is not depressed. Therefore, the reservoir tank 78
The first fluid chamber 60 communicates with the first fluid chamber 60 when the brake pedal 16 is not depressed, and when the piston 42 starts displacing with the depression of the brake pedal 16.
Be cut off from.

Next, the operation of the stroke simulator 10 will be described with reference to FIGS. FIG.
FIG. 7 is a diagram illustrating an example of a relationship between a pedal depression force F and a hydraulic pressure of a second liquid chamber 62, that is, a stroke simulator pressure _PST . FIGS. 5 to 7 show a process in which the brake pedal 16 is depressed (process indicated by an arrow shown in FIG. 4), and a process after the brake pedal 16 is depressed until the pedal depression force is reduced by a predetermined amount, respectively. FIG. 4 shows the state of the stroke simulator 10 in the process of releasing the depression of the brake pedal 16 and reducing the stroke simulator pressure _PST (the process shown by the arrow in FIG. 4).

[0033] As described above, when the brake pedal 16 is not depressed, the piston 42, the set spring 76, the set load f _s is acting on the depression releasing direction. For this reason, the pedal depression force F becomes equal to the set load f _s.
Does not occur, and the stroke simulator pressure _PST does not increase as indicated by the arrow in FIG.

The pedal force F is exceeds f _s, the piston 42 starts displacement in the direction of depression against the biasing force of the set spring 76. When the cup seal 46 exceeds the reservoir port 80 due to the displacement of the piston 42, the first liquid chamber 60 is shut off from the reservoir tank 78. With the first liquid chamber 60 is cut off from the reservoir tank 78, when the pedal force F is increased, the first fluid chamber 60 fluid pressure accordingly (hereinafter, referred to as a first fluid pressure P ₁₎ is increased I do. The first liquid chamber P ₁ is expressed by the following equation based on the balance of the force acting on the piston 42.

[0035] _{P 1 = (F-f s} ) / A p (1) where, A _p is the cross-sectional area of the piston 42. Incidentally, the set load f _s, strictly speaking, it varies according to the displacement amount of the piston 42. However, it can be regarded as a by setting a sufficiently small value the spring constant of the set spring 72, set load f _s is maintained constant regardless of the displacement of the piston 42.

As described above, the cup seal 58 provided in the passage 56 functions as a one-way valve that allows only the flow of the fluid from the first liquid chamber 60 to the second liquid chamber 62. Further, in a situation where the first hydraulic pressure P ₁ increases, a state in which the valve body 70 is seated on the valve seat 71 is maintained.
Accordingly, when the first hydraulic pressure P ₁ increases with an increase in the pedaling force F, the hydraulic oil in the first hydraulic chamber 60 flows into the second hydraulic chamber 62 via the passage 56 as shown in FIG. it is, the stroke simulator pressure P _ST rises to equal fluid pressure to the first hydraulic pressure P _1. That is, in the process of the pedal depression force F is increased, the stroke simulator pressure P _ST is generated equal to the first hydraulic pressure P _1. Therefore, as shown by the arrows in FIG. 4, in the region where the pedal force F exceeds the f _s is
According to the relationship expressed by the equation (1), the stroke simulator pressure P _ST increases linearly with an increase in the pedal effort F. Note that, as described above, the hydraulic pressure passage 28 is normally shut off by the solenoid valve 30, so that when the stroke simulator pressure _Pst increases, the hydraulic oil flows out of the second liquid chamber 62 to the hydraulic pressure passage 28. I will not do it.

When the increase in the pedal effort F is stopped and kept constant, the first hydraulic pressure P ₁ and the stroke simulator pressure P _ST are also kept constant. From this state, the pedal effort F
There Once reduced, according to equation (1), first fluid pressure P ₁ is reduced. When the first hydraulic pressure P ₁ becomes lower than the stroke simulator pressure P _ST due to the decrease of the first hydraulic pressure P ₁ , the passage 56 is blocked by the cup seal 58. On the other hand, the valve body 70, the differential pressure ΔP (= P _ST -P ₁₎ the force F _v corresponding to the first liquid chamber P ₁ and the stroke simulator pressure P _ST is, in the opposite direction to the valve load f _v Works. Here, when the cross-sectional area of the valve body 70 and A _v, the force F _v
Is represented by the following equation.

The _{F v = (P ST -P 1} ) · A v (2) if this force F _v is smaller than the valve load f _v, the valve body 70 is seated on the valve seat 71, the port 66
Is kept closed. On the other hand, when a force F _v exceeds the valve load f _v, the valve body 70 is unseated from the valve seat 71, the port 66 is conductive. That is,
Valve mechanism 53 functions as a one-way valve having a valve opening pressure f _v / A _v.

Therefore, after the pedal effort F is reduced, the difference
The pressure ΔP is the valve opening pressure f of the valve mechanism 53. _v/ A_VUntil it reaches
Then, as shown in FIG.
And the port 66 is closed by the valve body 70
Is closed by For this reason, the second liquid chamber 62 is the first liquid chamber.
60, the first hydraulic pressure P₁Decreases
Also the stroke simulator pressure P_STDoes not change.
Therefore, as shown by the arrow in FIG.
Until the hysteresis amount HYS exceeds
Emulator pressure P_STIs kept constant.

As the pedaling force F decreases, the first hydraulic pressure P
_{If 1} continues to decrease, the differential pressure ΔP (= P _ST −
P ₁ ) increases. Then, the differential pressure ΔP is equal to the valve opening pressure f _v / A
_{When the} pedal depression force F decreases until the pressure exceeds _v , as shown in FIG. 7, the valve body 70 separates from the valve seat 71, and the second liquid chamber 62 becomes the port 66, the valve chamber 63,
And the first liquid chamber 60 via the port 64. Second
When the liquid chamber 62 communicates with the first liquid chamber 60, the hydraulic fluid flows from the second liquid chamber 62 to the first liquid chamber 60, and the stroke simulator pressure _PST decreases. As the stroke simulator pressure P _ST decreases, the differential pressure ΔP increases as the valve opening pressure f _v / A _v
When the pressure falls below the threshold, the second liquid chamber 62 is shut off from the first liquid chamber 60 again by the valve body 70 sitting on the valve seat 71.

Thereafter, when the differential pressure ΔP exceeds the valve opening pressure f _v / A _v , the second liquid chamber 62 is electrically connected to the first liquid chamber 60, and the differential pressure ΔP
Is lower than the valve opening pressure f _v / A _v , the operation of shutting off the second liquid chamber 62 from the first liquid chamber 60 is repeated, so that the differential pressure ΔP is opened as shown by the arrow in FIG. Pressure f _v /
A _v equal status, i.e., while the stroke simulator pressure P _ST is maintained the state is high only opening pressure f _v / A _v than the first fluid pressure P _1, the stroke simulator pressure P _ST decreases It will be.

As described above, the stroke simulator pressure P
_ST starts to decrease when the differential pressure ΔP (= P _ST −P ₁ ) reaches the valve opening pressure f _v / A _v , that is, the first hydraulic pressure P
_This is the point in time when ₁ decreases by f _v / A _v . On the other hand, the first hydraulic P ₁ is expressed by equation (1) _{(P 1 = (F-f} s) / A p). Therefore, the amount of decrease in the pedaling force F until the stroke simulator pressure P _ST starts lowering, i.e., the hysteresis amount HYS becomes that represented by the following formula.

[0043] _{HYS = f v · A p /} A v (3) reduction of the pedal force F is stopped and starts to increase again,
(1) according to Formula first hydraulic P ₁ increases. For this reason, the differential pressure ΔP decreases, and the valve opening pressure f _v /
By below A _v, the valve body 70 is seated on the valve seat 71. Under such circumstances, during the first hydraulic P ₁ is a low pressure compared to the stroke simulator pressure P _ST is passage 56 because it is blocked by the cup seal 58, the stroke simulator pressure P _ST does not change. When the pedal depression force F is increased until the first hydraulic pressure P ₁ exceeds the stroke simulator pressure P _ST , the hydraulic oil flows from the first hydraulic chamber 60 through the passage 56 to the second hydraulic pressure P as shown in FIG.
The liquid flows into the liquid chamber 62. Thus, the stroke simulator pressure P _ST becomes first hydraulic P ₁ and isobaric, thereafter, as shown by the arrows in FIG. 4, the stroke simulator pressure P _ST is first
Increases with the increase of the pedal force F while dripping maintained at isobaric and hydraulic P _1.

When the depression of the brake pedal 16 is released as described above, the projection 73 formed on the guide rod 68 separates the valve body 70 from the valve seat 71. When the valve body 70 is separated from the valve seat 71, the first liquid chamber 60 and the second liquid chamber 62 communicate with each other via the port 66. Further, as described above, when the depression of the brake pedal 16 is released, the reservoir tank 78 and the first fluid chamber 60 communicate with each other through the reservoir port 80, so that the first fluid pressure P ₁ becomes the atmospheric pressure. The hydraulic pressures are equal. Therefore, is released the brake pedal 16, the pedal force F is reduced to equal to or less than the set load f _s, as shown by the arrows in FIG. 4, so that even the stroke simulator pressure P _ST drops to the atmospheric pressure . That is, since the projection 73 is provided on the guide rod 68, when the depression of the brake pedal 16 is released, the differential pressure ΔP (= f
_v / A _v) equal to the stroke simulator pressure P _ST may remain is prevented.

As described above, the stroke simulator 10
According to the above, the pedal depression force F and the stroke simulator pressure P
_A relationship with a hysteresis characteristic as shown in FIG. 4 is generated with the _ST . On the other hand, as described above, in the brake control device of the present embodiment, the braking force is controlled to a value corresponding to the stroke simulator pressure _PST . Therefore, according to this embodiment, similarly to the conventional booster type brake device, it is possible to realize a pedaling force-braking force relationship with a hysteresis characteristic as shown in FIG.

As described above, the hysteresis characteristic of the stroke simulator 10 is obtained by the urging force of the valve spring 72. That is, the stroke simulator 10 has a configuration in which the hysteresis characteristic can be obtained without providing a sliding portion, unlike the configuration of the related art in which the hysteresis characteristic is obtained by a disc spring. Therefore, according to the stroke simulator 10 of the present embodiment, it is possible to prevent the hysteresis characteristic from changing over time due to wear or the like due to sliding.

Further, the hysteresis amount HYS in the hysteresis characteristics, as represented by the equation (3), are dependent on the valve load f _v. The valve load f _v is a parameter that is completely unrelated to other characteristics of the stroke simulator 10 (for example, the gradient of the stroke simulator pressure P _{ST with} respect to the pedal effort F). Therefore, according to the stroke simulator 10, by appropriately setting the set load f _v of the valve spring 72, only the hysteresis amount HYS can be independently adjusted without affecting other characteristics of the stroke simulator 10. .

By the way, the stroke simulator pressure P _ST
Rises, a force corresponding to the hydraulic pressure acts on the damper 48, so that the damper spring 52 contracts and deforms. The sectional area of the damper 48 is represented by A _d , and the damper spring 52
Is assumed to be k _d , the contraction deformation amount x _d of the damper spring 52 is expressed by the following equation. x _d = P _ST · A _d / k _d (4) Since the volume of the liquid chamber 50 can be regarded as not changing, the amount of contraction deformation x _d of the damper spring 52 is equal to the amount of displacement of the piston 42 in the stepping direction. That is, it corresponds to the pedal stroke S. Therefore, the pedal stroke S is expressed by the following equation.

S = P _ST · A _d / k _d (5) From the equation (5), when a linear spring is used as the damper spring 52, the pedal stroke S changes in proportion to the stroke simulator pressure P _ST. You can see that When a non-linear spring is used as the damper spring 52, the spring constant k _d changes according to the amount of contraction deformation x _d . In this case, assuming that the relationship between the deformation amount x of the damper spring 52 and the spring force T is represented by a nonlinear function T = g (x), the pedal stroke S is represented by the following equation.

S = g ⁻¹ (P _ST · A _d / A _p ) (6) Accordingly, by appropriately selecting the non-linear characteristic of the damper spring 52, the relationship between the pedal depression force F and the pedal stroke S can be changed to a desired value. Can be set to characteristics. As the non-linear spring, for example, a coil spring or a disc spring having an uneven winding pitch can be used. Alternatively, the above-described non-linear characteristic can be realized by using a linear spring as the damper spring 52 and providing another elastic body which comes into contact with the damper 48 at a position where the damper 48 is displaced by a predetermined amount.

By the way, in the brake control apparatus of the present embodiment, as described above, ECU 12 is based on the stroke simulator pressure P _ST, by controlling the hydraulic actuator 22, the wheel cylinder pressure P _{W / C} is pedal depressing force F Is controlled to a value corresponding to. However, when a failure occurs in the hydraulic actuator 22 or the hydraulic pump 24, the wheel cylinder pressure P _{W / C} cannot be increased by the hydraulic actuator 22.

On the other hand, in the brake control device of this embodiment, when a system failure such as a failure of the hydraulic actuator 22 or the hydraulic pump 24 is detected, the EC
U12 supplies an ON signal to the solenoid valve 30,
The solenoid valve 30 is opened. When the solenoid valve 30 is opened,
Each of the wheel cylinders 26 communicates with the second fluid chamber 62 of the stroke simulator 10 through the fluid pressure passage 28,
The stroke simulator pressure _PST is supplied to the wheel cylinder 26. Therefore, according to the brake control device of the present embodiment, even when a system failure occurs, the wheel cylinder pressure P _{W / C} can be increased by using the second fluid chamber 62 of the stroke simulator 10 as a fluid pressure source. . In this sense, the brake control device according to the present embodiment is one in which fail-safe measures against a system failure are sufficiently taken.

As described above, in the present embodiment, the stroke simulator 10 also functions as a master cylinder by using the stroke simulator 10 as a hydraulic pressure source when the system fails. That is, according to the present embodiment, it is not necessary to separately provide the stroke simulator and the master cylinder.
The cost of the system can be reduced.

In the above embodiment, the hydraulic passage 28 is connected to the second liquid chamber 62, and the second liquid chamber 62
Is used as the hydraulic pressure source, but the hydraulic passage 28 may be connected to the first hydraulic chamber 60 and the first hydraulic chamber 60 may be used as the hydraulic pressure source. Further, in the above embodiment, the cup seal 58 is used as a one-way valve that allows the flow of the hydraulic oil from the first liquid chamber 60 to the second liquid chamber 62, and the valve opening pressure is set to zero, while the second valve is closed. As a one-way valve that allows the flow of hydraulic oil from the liquid chamber 62 to the first liquid chamber 60, the valve opening pressure f _v /
It decided to use the valve mechanism 53 having the A _v. However, the present invention is not limited to this, and uses a one-way valve having a constant valve opening pressure as a one-way valve that allows the flow of hydraulic oil from the first liquid chamber 60 to the second liquid chamber 62. As the one-way valve that allows the flow of the hydraulic oil from the second liquid chamber 62 to the first liquid chamber 60, a one-way valve such as a cup seal having a zero valve opening pressure may be used. That is, it is sufficient that at least one of the two one-way valves has a positive (ie, non-zero) valve opening pressure.

In the above embodiment, the cup seal 58 is connected to the first one-way valve according to the first aspect, and the valve mechanism 53 is connected to the second one-way valve according to the first aspect. 28 corresponds to the communication path described in claim 2, and the solenoid valve 30 corresponds to the shut-off valve described in claim 2, and the ECU 12 opens the solenoid valve 30 in the event of a system failure. The described fail-open valve means is realized.

[0056]

As described above, according to the first aspect of the invention, the hysteresis characteristic can be realized without providing a sliding portion in the brake pedal stroke simulator, and the opening pressure of each one-way valve can be reduced. By appropriately setting, the amount of hysteresis can be adjusted. Therefore,
ADVANTAGE OF THE INVENTION According to this invention, while being able to suppress the time-dependent change resulting from wear, it is possible to independently and arbitrarily adjust only the hysteresis characteristic without affecting other characteristics of the brake pedal stroke simulator.

According to the second aspect of the present invention, the brake stroke simulator can function as a master cylinder when the system fails. Therefore, according to the present invention, it is not necessary to separately provide the brake pedal stroke simulator and the master cylinder, so that the apparatus cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a brake control device to which a brake pedal stroke simulator according to an embodiment of the present invention is applied.

FIG. 2 is a view showing an example of a pedaling force-braking force relationship in a conventional booster type brake device.

FIG. 3 is a configuration diagram of a brake pedal stroke simulator of the present embodiment.

4 is a diagram showing an example of the relationship between the pedal depressing force F and the stroke simulator pressure P _ST realized by the brake pedal stroke simulator of this embodiment.

FIG. 5 is a view showing a brake pedal stroke simulator in the process of depressing a brake pedal.

FIG. 6 is a view showing a brake pedal stroke simulator in a process from when a brake pedal is depressed to when a pedal depression force is reduced by a predetermined amount.

FIG. 7 is a view showing a brake pedal stroke simulator in a process where the depression of the brake pedal is released and the stroke simulator pressure _PST is reduced.

[Explanation of symbols]

 Reference Signs List 10 brake pedal stroke simulator 12 ECU 16 brake pedal 42 piston 50 liquid chamber 53 valve mechanism 58 cup seal 60 first liquid chamber 62 second liquid chamber

Claims (2)

[Claims] A piston member to which a pedaling force is transmitted in a predetermined direction; and a damper provided apart from the piston member in the predetermined direction and urged in a direction opposite to the predetermined direction. A brake pedal stroke simulator comprising a member, a liquid chamber defined between the piston member and the damper member, and filled with hydraulic oil, wherein the liquid chamber includes a liquid chamber adjacent to the piston member. A first fluid chamber and a second fluid chamber adjacent to the damper member, and having a first valve opening pressure, and hydraulic fluid from the first fluid chamber to the second fluid chamber. A first one-way valve that permits only the flow of fluid, and a second one that has a second valve opening pressure and permits only the flow of hydraulic oil from the second fluid chamber to the first fluid chamber. A one-way valve, and the first valve opening pressure and the second valve opening pressure A brake pedal stroke simulator, characterized in that the sum of al was set to be a predetermined positive value. 2. A brake pedal stroke simulator according to claim 1, wherein an operation amount detecting means for detecting a brake operation amount, and a wheel cylinder pressure based on a predetermined high pressure source as a hydraulic pressure source based on the brake operation amount. A communication path connecting the first liquid chamber or the second liquid chamber to the wheel cylinder, and a shutoff valve provided in the communication path. A brake pedal stroke simulator, comprising: a failure opening means for opening the shut-off valve when the hydraulic pressure control means fails.