Vehicle Brake Systems

Abstract

To provide a vehicular brake system that can secure an operation feeling fitting to a human sensation, while adopting a mechanical configuration equipped with a brake booster.SOLUTION: A brake system 1 is equipped with a brake pedal 10, a brake booster 11, a master cylinder 12, and disc brakes 15 and 16. The brake booster 11 has a property that a jump-up point at which the booster starts outputting first pressure as output-starting pressure to the master cylinder 12 after pedal-stepping force reaches predetermined stepping force. The brakes 15 and 16 have properties that friction force is started to be generated between brake rotors 151 and 161 and a pad after liquid pressure of hydraulic liquid reaches second pressure. The master cylinder 12 has a cylinder diameter set so that the first pressure of the brake booster 11 is nearly equal to the second pressure of the brakes 15 and 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle brake system, and more particularly to a mechanical brake system equipped with a brake booster. [Background technology]

[0002] Brake systems for vehicles include mechanical systems that use a brake booster, and by-wire systems that convert the stroke input into an electrical signal to activate the brakes.

[0003] However, in conventional vehicle brake systems, there was a problem that the driver could not get an operation feeling that matched the human senses due to a mismatch between the break point in the force-stroke characteristics and the rise point of deceleration G. Specifically, as shown in the force-stroke characteristics in Figure 9(a), when the driver depresses the brake pedal, the brake pedal reaches a predetermined stroke ST C The gap between the brake rotor and brake pads only narrows until the stroke ST C Once this is exceeded, the frictional force of the brake pads actually acts on the brake rotor, causing deceleration G (arrow E1).

[0004] On the other hand, as shown in FIG. 9(b), the output hydraulic pressure of the brake booster is P This point is called the jump-up point P JU In the conventional braking system, the break point P C The hydraulic pressure P91 at the jump-up point P in Fig. 9(b) JU This difference resulted in a difference between the hydraulic pressure P92 at the brake pedal and the pressure at the jump-up point (arrow E2). This difference could cause the driver to suddenly experience deceleration G when the pedal pressure reached the jump-up point, requiring a correction. For this reason, it was difficult with conventional brake systems to ensure an operating feel that matched human senses.

[0005] In Patent Document 1, in a by-wire brake system, the break point P C This patent discloses a configuration that matches the timing at which deceleration G begins to occur when the brake pedal is depressed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6573220 Summary of the Invention [Problem to be solved by the invention]

[0007] By-wire brake systems require additional compensation measures in the event of an electrical failure, hydraulic generators to replace brake boosters, and other factors that increase manufacturing costs, so many vehicles are now using mechanical brake systems with brake boosters.However, even for these mechanical brake systems, it is necessary to ensure that the operating feel matches the human senses.

[0008] The present invention has been made to solve the above-mentioned problems, and aims to provide a vehicle brake system that employs a mechanical configuration equipped with a brake booster while ensuring an operating feel that matches human senses. [Means for solving the problem]

[0009] A vehicle brake system according to one aspect of the present invention includes a brake pedal, a brake booster, a master cylinder, and a brake. The brake pedal is supported by a pivotal support and configured to rotate about the pivotal support. The brake booster is connected to the brake pedal and multiplies a pedal force input to the brake pedal and outputs the result. The master cylinder is connected to the brake booster and increases the pressure of hydraulic fluid in accordance with the output of the brake booster. The brake includes a brake piston connected to the master cylinder and operated by the increased pressure of the hydraulic fluid, a brake rotor that rotates together with the vehicle wheels, and a pad that is pressed against the brake rotor by the operation of the brake piston to generate friction between the brake rotor and the brake piston.

[0010] In this aspect, the brake booster has a characteristic that there is a jump-up point at which it starts to output a first pressure, which is a predetermined pressure, to the master cylinder as an output start pressure after the pedal force reaches a predetermined pressure. Also, the brake has a characteristic that frictional force starts to be generated between the brake rotor and the pad after the hydraulic fluid pressure reaches a second pressure, which is a predetermined pressure. The master cylinder has a cylinder diameter set so that the first pressure in the brake booster at the jump-up point and the second pressure at which the frictional force in the brake starts to be generated are approximately equal.

[0011] The vehicle brake system according to the above aspect employs a master cylinder having a cylinder diameter set so that the first pressure at the jump-up point of the brake booster and the second pressure at which frictional force in the brakes begins to be generated are approximately equal, thereby realizing an operation feeling that matches the driver's sense in a mechanical brake system. That is, in the vehicle brake system according to the above aspect, the cylinder diameter of the master cylinder is set so that the first pressure and the second pressure are approximately equal, so that even when the driver depresses the brake pedal and reaches the jump-up point, a sudden deceleration G is not applied as in the conventional system, and corrective operation is not required. Therefore, the vehicle brake system according to the above aspect can provide the driver with an operation feeling that matches the driver's sense of depressing the brake pedal.

[0012] In the vehicle brake system according to the above aspect, the master cylinder may have a cylinder diameter set within a range of 26.5 mm or more and 32.0 mm or less.

[0013] In the vehicle brake system according to the above aspect, a master cylinder with a cylinder diameter of 26.5 mm or more is used, so that the output (hydraulic pressure) from the master cylinder at the jump-up point can be kept smaller than conventionally, which is effective in roughly matching the first pressure and the second pressure.

[0014] In addition, the vehicle brake system according to the above embodiment uses a master cylinder with a cylinder diameter of 32.0 mm or less, which makes it possible to avoid situations where the required output (hydraulic pressure) is not obtained, and is therefore suitable for providing the driver with a high level of operating feeling.

[0015] In the vehicle brake system according to the above aspect, the master cylinder may have a piston that reciprocates within the cylinder in the axial direction, and the brake booster may have a plunger connected to the brake pedal and that operates along the axis as the brake pedal rotates, a push rod connected to the piston of the master cylinder, and a reaction disc joined to the end of the push rod opposite to the end to which the piston is connected, and the plunger and the reaction disc may be spaced apart from each other until the pedal force reaches a predetermined force, and the jump-up point may be the point at which the plunger and the reaction disc come into contact when the pedal force reaches the predetermined force.

[0016] In the vehicle brake system according to the above aspect, the jump-up point is the point where there is no gap between the plunger and the reaction disc in the brake booster. As described above, a master cylinder having a cylinder diameter set so that the first pressure and the second pressure are approximately equal is used, so that the driver can be assured of a high level of operating feeling that is in line with human senses.

[0017] In the vehicle brake system according to the above aspect, the brake pedal may further have a rod connection portion which is a connection portion with the brake booster, and a tread portion which is depressed by the driver, and in the longitudinal direction of the brake pedal, the distance from the pivot support portion to the tread portion may be set within a range of 3.5 to 4.7 times the distance from the pivot support portion to the rod connection portion.

[0018] In the vehicle brake system according to the above aspect, the ratio of the distance from the journal to the rod connection to the distance from the tread (pedal ratio) of the brake pedal is set to 3.5 or more and 4.7 or less, so even if a master cylinder with a larger cylinder diameter than conventional master cylinders is used, the driver does not need to apply excessively large force to the brake pedal, thereby providing an operation feeling that suits the driver's senses.

[0019] In the vehicle brake system according to the above aspect, the second pressure may be approximately 0.2 MPa.

[0020] As a result of extensive research, the inventors of the present application have determined that the second pressure at the point when the pads come into contact with the brake rotor and frictional force begins to be generated is approximately 0.2 MPa. Based on these findings, by employing a master cylinder whose cylinder diameter is set so that the first pressure is approximately equal to the second pressure, it is possible to provide an operation feeling that matches human senses, as described above.

[0021] In the vehicle brake system according to the above aspect, the vehicle may be a passenger car.

[0022] The vehicle brake system according to the above aspect is a brake system adopted in a passenger car, which strongly demands an operation feeling that matches the driver's sense, and the vehicle brake system according to the above aspect can achieve this. [Effects of the Invention]

[0023] The vehicle brake system according to each of the above aspects can ensure an operational feeling that matches human senses while employing a mechanical configuration including a brake booster. [Brief explanation of the drawings]

[0024] [Figure 1]1 is a schematic diagram showing a configuration of a brake system according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a part of the configuration of the brake booster. [Figure 3] FIG. 2 is a cross-sectional view showing the configuration of a master cylinder. [Figure 4] FIG. 2 is a cross-sectional view showing the configuration of a disc brake. [Figure 5] This is a characteristic diagram showing the relationship between pedal stroke and hydraulic pressure. [Figure 6] FIG. 10 is a diagram for explaining a method for determining a master cylinder diameter. [Figure 7] FIG. 4 is a characteristic diagram showing the relationship between pedal pressure and brake fluid pressure. [Figure 8] FIG. 4 is a characteristic diagram showing the relationship between the diameter of the master cylinder and the jump-up hydraulic pressure. [Figure 9] (a) is a characteristic diagram showing the force-stroke characteristics of the brake, and (b) is a characteristic diagram showing the relationship between pedal force and brake fluid pressure in a conventional brake system. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example of the present invention, and the present invention is not limited to the following embodiment except for its essential configuration.

[0026] 1. Schematic configuration of brake system 1 A schematic configuration of a brake system 1 according to this embodiment will be described with reference to Fig. 1. The brake system 1 according to this embodiment is, as an example, a brake system applied to a passenger car.

[0027] As shown in Fig. 1, the brake system 1 includes a brake pedal 10, a brake booster 11, a master cylinder 12, hydraulic lines 13 and 14, disc brakes 15 and 16, and a reservoir tank 17. The brake pedal 10 has a pivotal support portion 101, which is a portion pivotally supported on the vehicle body, at one end of a pedal body 100, and is configured to be rotatable around the pivotal support portion 101. The brake pedal 10 also has a tread portion 102, which is the portion where the driver presses down, at a location on the pedal body 100 away from the pivotal support portion 101. Furthermore, the pedal body 100 of the brake pedal 10 has a rod connecting portion 103 to which an operating rod 110 of the brake booster 11 is connected.

[0028] Here, in the brake system 1 according to this embodiment, in the longitudinal direction of the pedal body 100, the ratio (pedal ratio) of the distance L0 from the pivot support portion 101 to the tread portion 102 to the distance L1 from the pivot support portion 101 to the rod connection portion 103 is set to 4.0.

[0029] The brake booster 11 is a device that multiplies the pedal force input via an operating rod 110 and outputs the multiplied force to the master cylinder 12. The master cylinder 12 is connected to the brake booster 11 and is a device that increases the pressure of the hydraulic fluid (brake oil) in accordance with the output of the brake booster 11.

[0030] The first hydraulic line 13 is connected to a caliper 150 of a disc brake 15 attached to a front wheel of the vehicle. The second hydraulic line 14 is connected to a caliper 160 of a disc brake 16 attached to a rear wheel of the vehicle.

[0031] The disc brakes 15, 16 have calipers 150, 160 with brake pistons that are actuated by hydraulic fluid pressurized by the master cylinder 12, and brake rotors 151, 161 that rotate together with the wheels. In this embodiment, floating type disc brakes 15, 16 are used as an example.

[0032] 2. Brake Booster 11 Configuration The configuration of the brake booster 11 will be described with reference to Fig. 2. Note that Fig. 2 shows only a part of the configuration of the brake booster 11.

[0033] 2, the brake booster 11 has a plunger 111, a reaction disc 112, and a push rod 113 in addition to the operating rod 110. The plunger 111 is joined to the end of the operating rod 110 opposite to the end connected to the rod connecting portion 103 of the brake pedal 10.

[0034] The push rod 113 is provided to extend toward the mounting side of the master cylinder 12 in the brake booster 11. The reaction disc 112 is a disk-shaped member between the plunger 111 and the push rod 113, and is made of rubber, for example.

[0035] As shown in the enlarged portion of Figure 2, when the driver is not depressing the brake pedal 10 or when the depressing force is less than a predetermined value, a gap G1 is left between the front end face 111a of the plunger 111 and the receiving surface 112a of the reaction disc 112. The gap G1 narrows as the driver increases the depressing force, and when a predetermined depressing force is applied, the front end face 111a of the plunger 111 and the receiving surface 112a of the reaction disc 112 come into contact with each other. In the brake booster 11, the point at which the gap G1 disappears is the jump-up point, and the pressure output from the push rod 113 to the master cylinder 12 at that time is the jump-up amount (first pressure).

[0036] In the brake booster 11, the gap G1 cannot be eliminated due to structural variations in the components, and a jump-up point always exists.

[0037] 3. Master Cylinder 12 Configuration The configuration of the master cylinder 12 will be described with reference to Fig. 3. Note that Fig. 3 shows the configuration of the master cylinder 12 in a schematic manner, with some components omitted.

[0038] As shown in FIG. 3, the master cylinder 12 is a tandem-type master cylinder and includes a cylinder body 120 and a piston 121. The cylinder body 120 has pressure chambers 120a and 120b defined by the piston 121. The cylinder body 120 also has four connection portions 120c to 120f. The connection portions 120c and 120e are connected to the pressure chamber 120a. The connection portion 120c connects the pressure chamber 120a to the reservoir tank 17 (arrow A2). The connection portion 120e is connected to the first hydraulic path 13 and connects the pressure chamber 120a to the caliper 150 (arrow A4).

[0039] The connection portion 120d and the connection portion 120f are connected to the pressure chamber 120b. The connection portion 120d connects the pressure chamber 120b to the reservoir tank 17 (arrow A3). The connection portion 120f is connected to the second hydraulic path 14 and connects the pressure chamber 120b to the caliper 160 (arrow A5).

[0040] Piston 121 has a first piston portion 121a and a second piston portion 121b that are spaced apart from each other in the axial direction of cylinder body 120. Piston 121 is capable of reciprocating in the axial direction of cylinder body 120 (arrow A1).

[0041] In this embodiment, the cylinder diameter D of the master cylinder 12 MC For example, the diameter is φ28.57mm.

[0042] 4. Configuration of the calipers 150, 160 of the disc brakes 15, 16 The internal configuration of the calipers 150, 160 of the disc brakes 15, 16 will be described with reference to Fig. 4. Note that Fig. 4 illustrates the internal configuration of the caliper 150 of the disc brake 15, but the internal configuration of the caliper 160 of the disc brake 160 is the same.

[0043] 4, pads 152 and 153, a brake piston 154, and a piston seal 155 are arranged inside the caliper 150. The pads 152 and 153 are arranged opposite each other with the rotor 151 in between. The brake piston 154 is arranged so as to be able to press the pad 153. The piston seal 155 is arranged so as to provide a liquid-tight seal between the outer periphery of the brake piston 154 and the inner wall surface of the caliper 150.

[0044] When hydraulic pressure is applied to the brake piston 154 via the first hydraulic path 13 (arrow B1), the brake piston 154 moves toward the rotor 151 as shown by arrow B2. As the brake piston 154 moves, the pad 153 also moves as shown by arrow B3. Before the brake piston 154 moves, a gap G3 is left between the main surface 151b of the rotor 151 and the pad 153, but as the hydraulic pressure to the brake piston 154 increases, the pad 153 comes into contact with the main surface 151b of the rotor 151 (gap G3 = 0).

[0045] If the hydraulic pressure continues to rise while pad 153 is in contact with main surface 151b of rotor 151, caliper 150 moves as shown by arrow B4, and pad 152 moves accordingly as shown by arrow B5. When the hydraulic pressure to brake piston 154 reaches a predetermined value, pad 152 comes into contact with main surface 151a of rotor 151 (gap G2=0), and pad 153 comes into contact with main surface 151b of rotor 151, generating a frictional force. The hydraulic pressure of the working fluid at which pad 152 and pad 153 come into contact with rotor 151 and frictional force begins to be generated corresponds to the second hydraulic pressure.

[0046] When the oil pressure drops, the brake piston 154 moves back due to the restoring force of the piston seal 155 made of rubber, and the pads 152 and 153 are released from contact with the rotor 151.

[0047] 5. Relationship between pedal stroke and hydraulic pressure The relationship between the pedal stroke by the driver and the hydraulic pressure (hydraulic pressure) applied to the brake piston 154 in the disc brakes 15, 16 will be described with reference to FIG.

[0048] As shown in Figure 5, when the driver depresses the brake pedal 10, the hydraulic pressure gradually increases. The relationship between the pedal stroke and the hydraulic pressure is expressed by an exponential curve L FS The curve L FS Then, at the point where the pedal stroke is "0", the tangent line L L Draw the tangent line L at the point where the liquid pressure is "1.0MPa". U When drawing, the tangent L L and the tangent L U Intersection point P C is disposed near a hydraulic pressure of 0.2 MPa. That is, in the disc brakes 15, 16, when the hydraulic pressure becomes 0.2 MPa or higher (arrow C), the gaps G2, G3 between the rotors 151, 161 and the pads 152, 153 disappear, generating a frictional force.

[0049] In addition, the intersection point P in Figure 5 C This corresponds to the "break point" in the force-stroke characteristic diagram.

[0050] 6. Master cylinder diameter D MC Settings Master cylinder 12 cylinder diameter D MC The setting of will be explained with reference to Fig. 6. In Fig. 6, the first quadrant shows the relationship between the pedal force and the input to the brake booster 11, the second quadrant shows the relationship between the input and output in the brake booster 11, the third quadrant shows the relationship between the input and output in the master cylinder 12, and the fourth quadrant shows the relationship between the output (hydraulic pressure) of the master cylinder 12 and the deceleration G in the disc brakes 15, 16. In Fig. 6, the thick dashed line indicates the characteristics of a comparative example.

[0051] Master cylinder 12 cylinder diameter D MC The setting of (1) is premised on realizing the deceleration G required when the driver depresses the brake pedal 10 with a predetermined depression force.

[0052] As shown in Figure 6, a perpendicular line is drawn from point P0, where the required deceleration G can be achieved, to the characteristic line L1 of the fourth quadrant (a characteristic line showing the relationship between the hydraulic pressure in the disc brakes 15, 16 and the deceleration G), and an intersection point P1 between the perpendicular line and the characteristic line L1 is obtained. When trying to achieve the required deceleration G in this embodiment, it can be seen that the output (hydraulic pressure) of the master cylinder 12 required is F1.

[0053] Cylinder diameter D MC In the case of a comparative example employing a master cylinder having a diameter of 22.22 mm, the intersection of the characteristic line L12 of the master cylinder according to the comparative example and the hydraulic pressure F1 is P12.

[0054] On the other hand, cylinder diameter D MC In the present embodiment, in which the master cylinder 12 has a diameter of 28.57 mm, the intersection point P2 is between the characteristic line L2 of the master cylinder 12 and the hydraulic pressure F1. The input value to the master cylinder 12 (the output value of the brake booster 11) at the intersection point P2 is larger than that at the intersection point P12.

[0055] As shown in the second quadrant of Figure 6, the brake booster 11 has a jump-up amount F2 where the output does not change with respect to the input. This jump-up amount F2 is due to the gap G1 described above. Furthermore, on the characteristic line L3 showing the relationship between the input and output of the brake booster 11, the input and output have a substantially linearly proportional relationship after the jump-up point P5.

[0056] Here, when a perpendicular line L5 is drawn from the jump-up point P5 to the third quadrant, the intersection with the characteristic line L12 is P16, and the intersection with the characteristic line L2 is P6. The output (hydraulic pressure) of the master cylinder 12 at the intersection P16 is 0.4 MPa, whereas the output (hydraulic pressure) of the master cylinder 12 at the intersection P6 is 0.2 MPa. That is, in the comparative example, the jump-up point P5 is at the break point P C In this embodiment, the hydraulic pressure (oil pressure) does not match at the jump-up point P5.C The hydraulic pressure is approximately the same at 0.2 MPa.

[0057] Next, when a perpendicular line is drawn from the intersection point P12 to the characteristic line L3, an intersection point P13 is obtained on the characteristic line L3. On the other hand, when a perpendicular line is drawn from the intersection point P2 to the characteristic line L3, an intersection point P3 is obtained on the characteristic line L3. As shown in Fig. 6, the input of the brake booster 11 at the intersection point P3 is higher than that at the intersection point P13 in the comparative example.

[0058] In the comparative example, the pedal ratio R P By adopting a brake pedal with a pedal ratio of 2.7 (a brake pedal having the characteristic line L14), the input to the brake booster corresponding to the intersection point P13 (the pedal force at the intersection point P14) is realized with the above-mentioned predetermined pedal force. P By adopting a brake pedal 10 (brake pedal having characteristic line L4) with a value of "4.0", the input to the brake booster corresponding to the intersection P13 (the depression force at intersection P4) is realized with the above-mentioned specified depression force.

[0059] 7. Jump-up point As described above, the hydraulic pressure is 0.2 MPa at the break point in the force-stroke characteristic, and the relationship between this hydraulic pressure and the jump-up amount (hydraulic pressure at the jump-up point) will be explained using Figure 7. In the graph of Figure 7, the characteristic line L16 shown by the dashed line is a comparative example, and the characteristic line L6 shown by the solid line is for the brake system 1 according to this embodiment.

[0060] As shown by the dashed line in Fig. 7, in the characteristic line L16 according to the comparative example, the hydraulic pressure rises suddenly to 0.4 MPa (jump-up amount) when the pedal depression force reaches a predetermined value. The hydraulic pressure value of 0.4 MPa at the jump-up point P17 in the comparative example is the value of 0.4 MPa at the break point P C The fluid pressure is higher than 0.2MPa and is not consistent.

[0061] On the other hand, in the characteristic line L6 of the brake system 1 according to this embodiment, the jump-up amount (hydraulic pressure) at the point where the pedal depression force reaches the predetermined value is 0.2 MPa. The value of the hydraulic pressure of 0.2 MPa at the jump-up point P7 is the value at the break point P C This value coincides with the hydraulic pressure of 0.2 MPa at the cylinder diameter D MC By adopting a master cylinder 12 with a larger diameter of φ28.57mm compared to conventional models, the break point P C Therefore, it is possible to make the hydraulic pressure at jump-up point P1 equal or substantially equal to the hydraulic pressure at jump-up point P7.

[0062] 8. Master cylinder diameter D MC Range In the brake system 1 according to this embodiment, the cylinder diameter D MC The master cylinder 12 has a diameter of 28.57 mm, but the break point P C The cylinder diameter D that allows the hydraulic pressure at the jump-up point P7 to be approximately equal to the hydraulic pressure at the jump-up point P8. MC The range will be explained with reference to FIG.

[0063] First, the inventors of the present application conducted extensive research into the range of the jump-up amount (hydraulic pressure at jump-up point P7) that would provide an operating feeling that matches the human senses. As a result, the inventors of the present application conducted extensive research into the range of the jump-up amount (hydraulic pressure at jump-up point P7) that would provide an operating feeling that matches the human senses. C Within ±0.05 MPa of the hydraulic pressure (0.2 MPa) at the time of the force stroke characteristic (in other words, the break point P C It was found that it would be sufficient if the pressure was within ±25% of the actual pressure. In other words, in this specification, "approximately the same" means within ±25%.

[0064] As shown in Figure 8, the horizontal axis represents the cylinder diameter D of the master cylinder 12. MC The vertical axis is the jump-up amount, and the vertical axis is the cylinder diameter D of the master cylinder 12. MCThe larger the value, the more the jump-up amount (hydraulic pressure) gradually decreases. To keep the jump-up amount within the range of 0.2MPa ± 0.05MPa (the range of arrow D1), the cylinder diameter D MC It is necessary to set the diameter to a range of φ26.5 mm or more (range of arrow D2).

[0065] In addition, the cylinder diameter D MC The upper limit of the cylinder diameter D is determined based on the hydraulic pressure required to achieve the desired deceleration G required to stop the vehicle. MC It is necessary to make the diameter 32.0 mm or less.

[0066] Furthermore, if an existing master cylinder is to be used, the diameter must be set within the range of φ26.99 mm or more and φ31.75 mm or less. In this case, there is no need to use a custom-made master cylinder, which helps to prevent increases in vehicle manufacturing costs.

[0067] 9.Effects In the brake system 1 according to this embodiment, the cylinder diameter D is set so that the hydraulic pressure (first pressure) at the jump-up point P7 in the brake booster 11 is approximately equal to the hydraulic pressure (second pressure) at which frictional force begins to be generated in the disc brakes 15 and 16. MC Since the master cylinder 12 having the cylinder diameter D MC By setting the first pressure and the second pressure, the hydraulic pressure at jump-up point P7 and the hydraulic pressure at which frictional force begins to be generated in disc brakes 15, 16 are approximately equal to each other, so that even when the driver depresses brake pedal 10 and reaches jump-up point P7, there is no sudden deceleration G as in the past, and no corrective operation is required. Therefore, brake system 1 can provide the driver with an operating feeling that matches the sensation of the driver's depressing action of brake pedal 10.

[0068] In the brake system 1 according to this embodiment, the cylinder diameter D MC Since the master cylinder 12 having a jump-up point P7 of 26.5 mm or more is used, the output (hydraulic pressure) from the master cylinder 12 at the jump-up point P7 can be kept smaller than before, which is effective in roughly matching the hydraulic pressure (first pressure) at the jump-up point P7 in the brake booster 11 with the hydraulic pressure (second pressure) at which frictional force begins to occur in the disc brakes 15, 16.

[0069] In addition, in brake system 1, the cylinder diameter D MC Since a master cylinder 12 having a clearance of 32.0 mm or less is used, it is possible to avoid a situation where the required output (hydraulic pressure) is not obtained, which is suitable for providing the driver with a high level of operating feeling.

[0070] In the brake system 1 according to this embodiment, the jump-up point P7 is determined by the gap G1 between the plunger 111 and the reaction disc 112 in the brake booster 12. The cylinder diameter D is set so that the hydraulic pressure (first hydraulic pressure) at the jump-up point P7 is approximately equal to the hydraulic pressure (second hydraulic pressure) at which the frictional force in the disc brakes 15 and 16 begins to be generated. MC Since the master cylinder 12 having the above structure is employed, it is possible to ensure that the driver has a high level of operational feeling that is in line with the human senses.

[0071] In addition, in the brake system 1 according to this embodiment, the pedal ratio of the brake pedal 10 is set to 3.5 or more and 4.7 or less (for example, 4.0), so that the cylinder diameter D is larger than that of the conventional brake system. MC Even if the master cylinder 12 having the above-mentioned structure is used, the driver does not need to apply excessively large force to the brake pedal 10. This also makes it possible to provide an operation feeling that matches the driver's senses.

[0072] As a result of extensive research, the inventors of the present application have determined that the hydraulic pressure at the time when the pads 152, 153 come into contact with the brake rotors 151, 161 and frictional force begins to be generated is approximately 0.2 MPa (0.2 MPa ± 0.05 MPa). MC By setting the cylinder diameter D so that the hydraulic pressure at the jump-up point P7 is approximately equal to the hydraulic pressure at which frictional force begins to occur in the disc brakes 15 and 16. MC By adopting the master cylinder 12 having the set torque, it is possible to provide an operation feeling that matches the human senses.

[0073] The brake system 1 according to this embodiment is a brake system used in a passenger car. In a passenger car, an operation feeling that matches the driver's sense is highly desired, and the brake system 1 can achieve this.

[0074] As described above, the brake system 1 according to this embodiment employs a mechanical configuration including the brake booster 11, while still ensuring an operational feeling that matches human sensibilities.

[0075] [Variations] In the above embodiment, the cylinder diameter D MC In the present invention, the master cylinder 12 is used, but the diameter of which is set in the range of φ26.5 mm to φ32.0 mm. However, the present invention is not limited to this. In other words, it is sufficient to use a master cylinder whose cylinder diameter is set so that the hydraulic pressure at the jump-up point (first pressure) and the hydraulic pressure at which frictional force in the disc brake begins to occur (second pressure) are approximately equal.

[0076] In the above embodiment, the jump-up amount is caused by the gap G1 between the plunger 111 and the reaction disc 112 in the brake booster 11. However, in the present invention, the jump-up amount may also be caused by variations in other components of the brake booster.

[0077] Furthermore, in the above embodiment, the pedal ratio of the brake pedal 10 is set to 3.5 or more and 4.7 or less. However, in the present invention, when a master cylinder is used in which the cylinder diameter is set so that the hydraulic pressure at the jump-up point and the hydraulic pressure at which frictional force begins to be generated in the disc brake are approximately equal, it is possible to adopt a pedal ratio that allows the driver to input the necessary force to the brake booster.

[0078] In addition, in the above embodiment, the master cylinder 12 is used in which the cylinder diameter DMC is set so that the hydraulic pressure at the jump-up point and the hydraulic pressure at which frictional force begins to occur in the disc brake are approximately equal. In this case, "approximately equal" can be defined as, for example, an allowable range of about ±25% of the reference hydraulic pressure.

[0079] Furthermore, the brake system 1 according to the above embodiment is intended for application to passenger cars that are primarily used for transporting people and have a small passenger capacity (for example, 10 people or less), but the present invention is not limited to this and can also be used in vehicles for transporting cargo. [Explanation of symbols]

[0080] 1. Brake system 10. Brake pedal 11 Brake booster 12 Master cylinder 15,16 Disc brake 111 Plunger 112 Reaction Disc 113 Push rod 150,160 caliper 151,161 rotors 152,153 Pad 154 Brake piston D MC Master cylinder diameter P7 Jump Up Point P C Break point

Claims

1. A braking system for a vehicle, comprising: a brake pedal that is pivotally supported by a pivotal support portion and is configured to be rotatable around the pivotal support portion; a brake booster connected to the brake pedal, multiplying a pedal depression force input to the brake pedal and outputting the result; a master cylinder connected to the brake booster and increasing the pressure of hydraulic fluid in accordance with the output of the brake booster; a brake having a brake piston connected to the master cylinder and actuated by the pressurized hydraulic fluid, a brake rotor that rotates together with a wheel of the vehicle, and a pad that is pressed against the brake rotor by actuation of the brake piston to generate a frictional force between the brake rotor and the pad; Equipped with the brake booster has a characteristic that there is a jump-up point at which it starts to output a first pressure, which is a predetermined pressure, to the master cylinder as an output start pressure after the pedal depression force reaches a predetermined depression force, the brake has a characteristic that a frictional force begins to be generated between the brake rotor and the pad when the hydraulic fluid pressure reaches a second pressure, which is a predetermined pressure; The master cylinder has a cylinder diameter set so that the first pressure at the jump-up point in the brake booster and the second pressure at which the frictional force in the brake begins to be generated are substantially equal to each other. Vehicle brake system.

2. 2. The vehicle brake system according to claim 1, The master cylinder has a cylinder diameter set within a range of 26.5 mm or more and 32.0 mm or less. Vehicle brake system.

3. 3. The vehicle brake system according to claim 1, The master cylinder has a piston that reciprocates in the cylinder in the axial direction, The brake booster is a plunger connected to the brake pedal and adapted to move along an axis in accordance with rotation of the brake pedal; a push rod connected to the piston of the master cylinder; a reaction disk joined to an end of the push rod opposite to the end to which the piston is connected; and The plunger and the reaction disc are spaced apart from each other until the pedal force reaches a predetermined value. The jump-up point is a point at which the pedal depression force reaches the predetermined depression force and the plunger and the reaction disc come into contact with each other. Vehicle brake system.

4. 3. The vehicle brake system according to claim 1, The brake pedal further includes a rod connecting portion that is a connecting portion with the brake booster, and a tread portion that is depressed by a driver, In the longitudinal direction of the brake pedal, the distance from the pivot support portion to the tread portion is set within a range of 3.5 to 4.7 times the distance from the pivot support portion to the rod connecting portion. Vehicle brake system.

5. 3. The vehicle brake system according to claim 1, The second pressure is approximately 0.2 MPa. Vehicle brake system.

6. 3. The vehicle brake system according to claim 1, The vehicle is a passenger car. Vehicle brake system.

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