JPH0347961Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an improvement of a master cylinder in an automobile brake system.

(Prior Art) Generally, a brake system for an automobile is equipped with a master cylinder that generates braking hydraulic pressure. It is structured like this. That is, as shown in FIG. 1, a piston C having a sealing piston cup B attached to the end thereof is fitted into a cylinder body A, and a hydraulic oil chamber D is defined by the piston C and the cylinder bore. A relief hole F and an oil supply hole G are provided in the upper circumferential wall of the main body A to communicate the inside of the cylinder bore with a reservoir tank E provided above. Here, the rear oil supply hole G has a large diameter and communicates with the chamber H at the rear of the piston C, and the front relief hole has a small diameter so that when the piston C is located at the rear as shown in the figure, It is provided so as to communicate with the hydraulic oil chamber D. Then, when the brake pedal is depressed, the piston C moves forward (in the direction of arrow I) from the state shown in the figure, and braking oil pressure is generated in the hydraulic oil chamber D, which is transferred to the wheel cylinder ( (not shown). At this time, the piston cup B moves forward together with the piston C, and the hydraulic oil chamber D
and the relief hole F to prevent the hydraulic fluid chamber from flowing back toward the reservoir tank E. However, since the relief hole F has a small diameter, the second
As shown by a curve I in the graph, the oil pressure in the hydraulic oil chamber D rises before the position S where the piston cup B passes through the relief hole F.

On the other hand, in recent years, there has been a tendency to reduce play in brakes, and as a result, in the master cylinder, the oil pressure in the hydraulic fluid chamber D rises after the piston C starts moving forward from its initial position. The initial stroke amount until it goes up is smaller than before. In other words, as shown in Figure 2,
The rising position of the hydraulic pressure moves from S ₀ to S ₀ ′, and as a result, as shown by the curve, the piston cup B
The oil pressure in the hydraulic oil chamber D at the position S where the pressure passes through the relief hole F increases from _P0 to _P1 .

However, if the oil pressure in the hydraulic oil chamber D is high when the piston cup B passes through the relief hole F, the lip portion B' on the periphery of the cup B deforms so as to be pushed into the relief hole F, and this state Since the cup B moves together with the piston C, there is a risk that the lip portion B' may be eaten away or damaged. In particular, this problem occurs when the rear wheel cylinder is connected to the front hydraulic fluid chamber of the cylinder body due to brake pipe piping issues in tandem master cylinders that have two hydraulic fluid chambers inside the cylinder body. It is more likely to occur when In other words. In the front hydraulic oil chamber, when the brake pedal is depressed, the hydraulic pressure rises faster than in the rear hydraulic oil chamber, and since the capacity of the rear brake is small, the hydraulic pressure rises even more quickly.
This is because the oil pressure in the chamber becomes higher when the piston cup passes through the relief hole.

Note that in order to keep the hydraulic pressure in the hydraulic oil chamber low when the piston cup passes through the relief hole, the diameter of the relief hole can be made large, but in that case, the lip of the piston cup is close to the opening edge of the relief hole. If it gets caught, the lip becomes more susceptible to damage.

(Purpose of the invention) The present invention was made in view of the above-mentioned problems. Even when the play of the brake is small and therefore the hydraulic pressure in the hydraulic oil chamber of the master cylinder rises quickly, the piston cup does not close to the relief hole. The purpose of this invention is to suppress the hydraulic pressure to a low level when the piston passes through the piston, thereby reliably preventing the lip portion of the piston cup from being damaged by the relief hole when the piston moves.

(Structure of the invention) In order to achieve the above object, the master cylinder according to the invention is structured as follows.

That is, in a master cylinder in which a piston press-operated by a pedal is fitted into a cylinder bore of a cylinder body and supplies hydraulic oil to a brake member in each wheel, the master cylinder communicates with a hydraulic oil chamber defined by the cylinder bore and the piston. A pressure absorbing chamber is provided, which is composed of an auxiliary bore and an elastically deformable pressure receiving member provided within the auxiliary bore, and whose volume changes in response to the working pressure in the working hydraulic pressure chamber. The cylindrical portion is fitted into the inner circumferential surface of the cylindrical portion, and an elastically deformable pressure receiving portion is formed integrally with the end face of the cylindrical portion to partition the auxiliary bore and the working oil chamber. The pressure absorption chamber changes in volume to absorb the oil pressure when the oil pressure in the hydraulic oil chamber rises. That is, the pressure-receiving member that constitutes the pressure-absorbing chamber is elastically deformed to increase the volume inside the hydraulic oil chamber when the hydraulic pressure rises, and as a result,
The rise of the hydraulic oil chamber relative to the piston stroke becomes gradual, and the hydraulic pressure when the piston cup passes through the relief hole is reduced by that much, thereby preventing damage to the cup.

In addition, as the pressure receiving part is elastically deformed due to the pressure increase in the hydraulic oil chamber, the cylindrical part is strongly pressed against the inner peripheral surface of the auxiliary bore, and the sealing performance between the auxiliary bore and the hydraulic oil chamber is deteriorated. This reliably prevents the hydraulic oil from flowing into the auxiliary bore side from the hydraulic oil chamber side, and the function of the pressure absorption chamber does not deteriorate.

Furthermore, even if the pressure-receiving member is damaged, there is no risk that the braking function itself will deteriorate as the oil pressure rises rapidly.

In addition, due to the elastic deformation of the pressure-receiving part, the hydraulic pressure in the hydraulic oil chamber rises in conjunction with the depression of the brake within a range that does not cause damage to the piston cup, thereby reducing the response delay during braking. I'm never invited.

Note that the pressure absorption chamber may be provided in the middle of the brake pipe between the hydraulic oil chamber of the master cylinder and the wheel cylinder.

(Example) The present invention will be described below based on an example shown in the drawings.

First, as shown in FIG. 3, the overall system configuration of the brake device will be explained.
A master cylinder 5 receives the pedal force applied to the brake pedal 2 via an operating rod 3 and a master back 4 and generates hydraulic pressure corresponding to the pedal force, and a master cylinder 5 that generates hydraulic pressure corresponding to the pedal force, and a master cylinder 5 that receives the pedal force applied to the brake pedal 2 via an operating rod 3 and a master back 4, and a master cylinder 5 that generates hydraulic pressure corresponding to the pedal force. It has front wheel cylinders 8, 8 and rear wheel cylinders 9, 9, which are supplied via pipes 6, 7, respectively. Further, a reservoir tank 10 is provided above the master cylinder 5.
is provided, the tank 10 and the inside of the master cylinder 5 are communicated with each other, and hydraulic oil is supplied and discharged between the tank 10 and the inside of the master cylinder 5. In this embodiment, the master cylinder 5 is of a tandem type, in which two pistons 11 and 12, a first and a second, are fitted in series, and a first piston that generates the hydraulic pressure is installed inside the master cylinder 5. The hydraulic fluid chamber 13 is located between the first and second pistons 11 and 12, and the second hydraulic fluid chamber 14 is located between the second piston 12.
are formed in front of each other. Since the proportioning valve 15 is disposed on the first and second brake pipes 6 and 7, the first hydraulic fluid chamber 13 on the rear side is connected to the wheel cylinders 8 and 8 on the front side, and The brake pipes 6 and 7 are connected so that the second hydraulic oil chamber 14 communicates with the rear wheel cylinders 9 and 9, respectively.

Next, the internal structure of the front portion X of the master cylinder 5 will be explained in more detail based on FIG. 4.

As mentioned above, the bore 16a in the cylinder body 16 of this master cylinder 5 has a (second)
A (second) hydraulic oil chamber 14 for generating oil pressure is formed in front of the piston 12 fitted therein. The hydraulic oil chamber 14 is connected to a hydraulic oil outlet 16b provided in the peripheral wall of the cylinder body 16. It communicates with the rear wheel cylinders 9 through a (second) brake pipe 7.
Further, a hollow cylindrical mounting part 16c for mounting the reservoir tank 10 is provided on the upper part of the peripheral wall of the cylinder body 16, and a small diameter relief hole 16 is provided in front of the bottom position of the mounting part 16c.
d and a large-diameter oil supply hole 16e are provided at the rear, respectively, and the reservoir tank 10 and the inside of the cylinder bore 16a are communicated through these holes 16d and 16e.

On the other hand, in front of the piston 12 there is a large diameter section 12.
a is provided, and the hydraulic oil chamber 14 and the piston back chamber 17 behind it are partitioned by the large diameter portion 12a, and a rubber seal is provided in front of the large diameter portion 12a. When the piston cup 18 is installed and the pressure inside the hydraulic oil chamber 14 increases, the lip portion 18a of the cup 18 is pressed against the circumferential surface of the cylinder bore 16a, thereby maintaining the oil tightness of the hydraulic oil chamber 14. It is becoming more and more common.
When the piston 12 is in the retracted position, the relief hole 16d communicates with the hydraulic oil chamber 14, and the oil supply hole 16e communicates with the piston back chamber 17. Further, both chambers 14, 1 are provided in the large diameter portion 12a.
Communication holes 12b...12b are provided to communicate with each other. The piston 12 is always moved rearward, that is, to the right in the drawing, by a return spring 21 installed between the front end surface of the piston 12 and the inner end surface of the cylinder body 16 via spring receiving members 19 and 20, respectively. In addition to being biased, the retracted position is regulated by a stopper 22 attached to the peripheral wall of the cylinder body 16.

However, this master cylinder 5 is provided with a pressure absorption chamber 23 at the front end of the hydraulic fluid chamber 14 . The chamber 23 is connected to the cylinder body 1
6, an auxiliary bore 24 is formed at the front end of the cylinder bore 16a so as to be continuous with the cylinder bore 16a, and a pressure receiving member 25 is installed in the bore 24 to partition the bore 24 and the hydraulic oil chamber 14. Further, the pressure receiving member 25 is made of elastically displaceable rubber or the like, and includes a cylindrical portion 25a that fits into the inner peripheral surface of the auxiliary bore 24, and a pressure receiving portion 25b that closes the end surface on the cylinder bore 16a side. It is composed of. When the oil pressure in the hydraulic oil chamber 14 rises, the pressure receiving portion 25b bends as shown by the chain line in response to the oil pressure. At this time, the cylindrical portion 25a attempts to expand outward and comes into pressure contact with the inner circumferential surface of the auxiliary bore 24, thereby preventing hydraulic oil from entering the pressure absorption chamber 23 from the cylinder bore 16a side. If necessary, the inner circumferential surface of the auxiliary bore 24 and the outer circumferential surface of the inner cylindrical portion 25a of the pressure receiving member 25 may be bonded with an adhesive or the like to more reliably seal the space between the two bores.

Next, the operation of the above embodiment will be explained.

Assuming that the brake pedal 2 is depressed to control the automobile, the pedal force is input to the master cylinder 5 via the operating rod 3, master back 4, etc. Therefore, the cylinder 5
, the first piston 11 shown in FIG. 3 is moved to the left in the drawing, and the first hydraulic oil chamber 13
The second piston 12 is also moved to the left via the hydraulic oil therein, and braking oil pressure is generated in both the hydraulic oil chambers 13 and 14, respectively. These hydraulic pressures are then pressure-fed to the front and rear wheel cylinders 8, 8 and 9, 9 through the hydraulic oil delivery ports 16b, 16b and the first and second brake pipes 6, 7, respectively. , the front and rear brakes are activated.

However, when both the pistons 11 and 12 move, the hydraulic pressure rises in the second hydraulic oil chamber 14 on the front side of the cylinder body 16 before the first hydraulic oil chamber 13, and the pressure rises in the second hydraulic oil chamber 14. Since the connected rear brake has a small capacity, the second hydraulic oil chamber 1 is
After the second piston 12 starts moving, the oil pressure inside the piston 4 immediately and rapidly tries to rise after a small initial stroke Y. At this time, the second piston 12
At the beginning of the movement, the piston cup 18 has not passed through the relief hole 16d as shown in FIG.
6d is in communication with the reservoir tank 10, but since the relief hole 16d has a small diameter, the oil pressure in the hydraulic oil chamber 14 tends to rise rapidly as described above. However, the second hydraulic oil chamber 14
A pressure absorption chamber 23 is provided at the front end of the hydraulic fluid chamber 14. When the hydraulic pressure in the hydraulic oil chamber 14 rises, the pressure receiving portion 25b of the pressure receiving member 25 of the pressure absorption chamber 23 receives the hydraulic pressure, and the fourth As shown by the chain line in the figure, the second hydraulic fluid chamber 14 is elastically deformed to increase its volume. Therefore, the hydraulic pressure in the hydraulic oil chamber 14 is weakened in accordance with this amount of deformation. As a result, as shown by the curve in FIG.
At the position S where the lip portion 18a of No. 8 passes through the relief hole 16d, the oil pressure in the second hydraulic oil chamber 14 decreases from _P1 , which is the conventional value, to _P2 . This prevents the lip portion 18a from becoming stuck in the relief hole 16d, and prevents damage to the lip portion 18a that would otherwise occur if the lip portion 18a were moved while being dug into the relief hole 16d.

When the second piston 12 is returned after the brake is released, the piston passes through the communication holes 12b...12b in the large diameter portion 12a of the piston 12 and the outside of the lip portion 18a of the piston cup 18, as shown in FIG. From the back chamber 17 to the second hydraulic oil chamber 14
By introducing hydraulic oil into the piston 1
2 is quickly returned to its original position. In this embodiment, the cylindrical portion 25a is strongly pressed against the inner circumferential surface of the auxiliary bore 24 as the pressure receiving portion 25b is elastically deformed due to the pressure increase in the second hydraulic oil chamber 14. The sealing performance between the auxiliary bore 24 and the second hydraulic oil chamber 14 is improved, and thereby,
The flow of hydraulic oil from the hydraulic oil chamber 14 side to the auxiliary bore 24 side is reliably prevented, and the function of the pressure absorption chamber 23 is not deteriorated.

Furthermore, even if the pressure-receiving member 25 is damaged, the brake function itself will not deteriorate, only because the oil pressure will rise suddenly.

In addition, due to the elastic deformation of the pressure receiving portion 25b, the piston cup 1 is moved in conjunction with the depression of the brake.
8 within the range that does not cause damage to the second hydraulic fluid chamber 1.
A delay in response during braking does not occur due to an increase in the oil pressure within the brake system.

(Effects of the invention) As described above, according to the invention, when the brake pedal is depressed, the rise of the hydraulic pressure in the hydraulic oil chamber of the master cylinder becomes gradual, and when the piston cup passes through the relief hole, the hydraulic pressure rises slowly in the hydraulic oil chamber of the master cylinder. This means that the oil pressure will be suppressed to a lower level than before. This prevents the lip of the piston cup from digging into the relief hole when the piston cup passes through the relief hole, and prevents damage to the lip that would occur if the piston cup were moved with the lip biting into the relief hole. This will be prevented. In addition, as the pressure receiving part is elastically deformed due to the pressure increase in the hydraulic oil chamber, the cylindrical part
It is strongly pressed against the inner peripheral surface of the auxiliary bore, improving the sealing performance between the auxiliary bore and the hydraulic oil chamber, and as a result, the hydraulic oil flows from the hydraulic oil chamber side to the auxiliary bore side. This is reliably prevented, and the function of the pressure absorption chamber does not deteriorate.

Furthermore, even if the pressure-receiving member is damaged, the brake function itself will not be degraded, only because the oil pressure will rise suddenly.

In addition, due to the elastic deformation of the pressure-receiving part, the hydraulic pressure in the hydraulic oil chamber rises in conjunction with depression of the brake within a range that does not cause damage to the piston cup, thereby preventing a delay in response during braking. .

Note that the present invention is not limited to the dandem-type master cylinder shown in the embodiment, but is also applicable to a single-type master cylinder in which only one hydraulic oil chamber is provided.

[Brief explanation of the drawing]

Figures 1 and 2 show a conventional example. Figure 1 is a partially cutaway sectional view of the master cylinder, Figure 2 is a graph showing changes in oil pressure in the hydraulic oil chamber with respect to piston stroke, and Figures 3, 4, and 5. 3 shows a system diagram of a brake device to which the master cylinder of the present invention is applied, FIG. 4 is an enlarged vertical cross-sectional view of the main part of the master cylinder, and FIG. 5 shows an example of the piston stroke. It is a graph showing changes in oil pressure in a hydraulic oil chamber in comparison with a conventional example. 1... Brake device, 2... Brake pedal,
5... Master cylinder, 8, 9... Wheel cylinder (brake member), 11, 12... First and second pistons, 13, 14... First and second hydraulic oil chambers, 16... Cylinder body, 16a...Cylinder bore, 23...Pressure absorption chamber, 24...Auxiliary bore, 25...Pressure receiving member, 25a...Cylindrical portion, 2
5b...Pressure receiving part.

Claims (1)

[Scope of utility model registration request] A master cylinder in which a piston that is pressed by a pedal is fitted into the cylinder bore of the cylinder body and supplies hydraulic oil to the brake members of each wheel, and communicates with a hydraulic oil chamber defined by the cylinder bore and the piston. A pressure-absorbing chamber is provided, which is composed of an auxiliary bore and an elastically deformable pressure-receiving member provided within the auxiliary bore, and whose volume changes in response to the hydraulic pressure in the hydraulic pressure chamber, and the pressure-receiving member comprises: The auxiliary bore has a cylindrical portion that fits into the inner circumferential surface of the auxiliary bore, and an elastically deformable pressure receiving portion that is integrally formed on the end surface of the cylindrical portion and partitions the auxiliary bore and the working oil chamber. Master cylinder of brake equipment.