JPH0355473Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a brake master cylinder device for operating hydraulic brakes provided on agricultural tractors and other vehicles.

[Prior Art] As a conventional brake master cylinder device of this type, one disclosed in, for example, Japanese Utility Model Application Publication No. 116261/1983 is known.

This master cylinder device takes a long stroke of the piston after closing the tank port in the process of pushing the piston into the cylinder chamber, making it possible to easily obtain various types of braking force from small braking force to large braking force by pedal operation. I'm trying to be able to do that.

The structure is such that the tank port of the hydraulic power source and the brake port of the brake cylinder are connected in a cylinder chamber, and a piston that interlocks with the pedal is movably inserted into the cylinder, and an elastic seal is installed around the outer circumference of the piston. The tank port and cylinder chamber are opened and closed by the cylinder. These members are provided in a pair in the cylinder housing, the pair of cylinder chambers are connected through a communication hole, and a ball that is opened and closed by the end of the piston is movably incorporated in the mouth end of the communication hole.

However, the above structure has the following problems.

First, when the piston is pushed in, the ball is pushed by the end of the piston to open the valve, but as the piston is pushed repeatedly, the surface of the ball gets scratched by the piston, and the sealing properties of the ball deteriorate, resulting in oil leakage. leakage may occur and the desired braking force may not be generated.

Second, the elastic seal ring provided around the outer circumference of the piston moves with the piston, and at that time, it gets caught on the mouth end of the tank port or comes into sliding contact with the inner circumference of the cylinder chamber, and the elastic seal ring becomes flat during long-term use. or become damaged, and thus the desired sealing effect cannot be achieved. Alternatively, if the pressure on the brake cylinder side increases suddenly, this pressure may cause the elastic seal ring to protrude or become misaligned. For this reason, the applicant has developed a brake master cylinder device with improved sealing performance. (Special Application No. 1981-191245).

This master cylinder device has a piston and a valve arranged in series in the cylinder chamber, a passage connecting the hydraulic power source and the brake cylinder in the piston, and the valve head facing the mouth end of this passage so as to be openable and closable. Yes, when the piston is pushed in by pedal operation when braking or turning the vehicle, the passage inside the piston is blocked by the valve head of the valve, and when the piston and valve are pushed further, the oil in the oil chamber at the back of the valve flows into the brake cylinder. The pressure applied to the brake cylinder according to the stroke of the piston acts on the brake cylinder to operate it.

[Problems to be solved by the invention] However, in this master cylinder device, when the pedal operation is stopped, the piston and valve return to their original positions using a spring, but the speed at which the valve returns to its original position is faster than the speed at which the valve returns from the brake cylinder to the oil chamber. Faster than the flow speed, the oil chamber becomes negative pressure and the oil amount becomes insufficient. For this reason, when braking and turning operations are repeated, the position of the pedal corresponding to the braking force changes, making the operation uncomfortable and there is a risk of malfunction.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a brake master cylinder device that improves sealing performance and prevents negative pressure in the oil chamber at the back of the valve.

[Means for Solving the Problems] The present structure for achieving the above object is characterized in that the oil chamber at the back of the valve is opened and closed by a hydraulic power source via a check valve.

[Operation] When the valve returns, oil from the hydraulic power source is sucked into the oil chamber at the back via the check valve.

[Example] Hereinafter, an example of implementation of the present invention will be described based on the accompanying drawings.

In FIG. 1, a master cylinder 4 is provided in the middle of a passage 3 that connects a tank 1, which is a hydraulic pressure source, and a brake cylinder 2.

The master cylinder 4 includes a cylinder body 5, a pair of cylinder chambers 6, 7 provided in the cylinder body 5, pistons 8, 9 slidably inserted into each cylinder chamber 6, 7, and each cylinder 6,
Poppet type valve 1 movably inserted into 7
It consists of 0 and 11.

When a vehicle such as an agricultural tractor has a pair of left and right wheels, a pair of brake cylinders 2, 2 is provided as shown in the figure to brake each wheel, and a piston or the like is provided to operate each brake cylinder 2, 2. Although a pair of brake cylinders 2 and pistons are provided, for example, in a two-wheeled vehicle such as a motorcycle, it is necessary to brake only the rear wheels or the front wheels, so in this case, only one brake cylinder 2 and one piston are required.

Each piston 8, 9 has a radial passage 12, 1 connecting the passage 3 on the tank 1 side and the cylinder chamber 6, 7.
3 and axial passages 14 and 15 are formed, and the passage 1
At the mouth ends of 4 and 15 are Ratsupa-shaped sheets 16 and 17.
is formed.

The outer ends of the pistons 8 and 9 are respectively linked to brake pedals on the vehicle body, and when the brake pedals are depressed with a foot or the like, the pistons 8 and 9 are pushed in simultaneously or selectively.

Seals 1 are provided on the outer peripheries of the pistons 8 and 9, respectively.
A seal member 20 such as a dust seal or an oil seal is provided at the tip of the cylinder body 5, and boots 21 and 21 are installed between the cylinder body 5 and the pistons 8 and 9. ing.

At the rear end of the cylinder body 5 is a cap 2.
2 and 23 are screwed together, and the outer periphery is covered with seals 24 and 2.
It is sealed with 4.

Oil chambers 26 and 27 are provided within the caps 22 and 23.

The oil chamber 26 opens into the cylinder chambers 6, 7 through passages 28, 29 provided at the tips of the caps 22, 23.

A valve 10 is movably inserted into the oil chambers 26 and 27 via piston portions 30 and 31, and the distal end of the valve 10 is movably inserted into the cylinder chambers 6 and 7, and the valve head 32 is movably inserted into the cylinder chambers 6 and 7. , 33 are openably and closably opposed to the lapel-shaped seats 16, 17 of the pistons 8, 9.

The valves 10 and 11 have poppet-shaped valve heads 32 and 3.
3, there are also poppet-shaped valve bodies 34 and 35 on the body.
is formed.

Springs 36, 37 and 38, 39 are provided at the front end and rear end of the valves 10, 11, respectively;
The other valve 11 is held at a neutral position by springs 38 and 39, respectively. In this neutral state, the valve heads 32 and 33 are slightly apart from the seats 16 and 17, opening the passages 14 and 15 into the cylinder chambers 6 and 7, while the valve bodies 34 and
35 are in contact with the seats of the passages 28 and 29, respectively, and the cylinder chambers 6 and 7 are connected to the oil chambers 26 and 2 at the back of the valve.
7 and is blocked.

The valves 10 and 11 are hollow, and have through holes 40 and 41 in their rear bodies, and through holes 42 and 43 in the caps 22 and 23, respectively.
The oil chambers 26 and 27 at the back of the valve communicate with each other through these holes and the passage, and are always maintained at the same pressure. ing.

The passage 44 is connected to the passage 3 on the hydraulic power source 1 side via a low pressure passage 46 provided in the cylinder body 5,
A check valve 45 that allows oil to flow only from the passage 3 to the passage 44 is provided in the middle of the low pressure passage 46 so as to be openable and closable.

The cylinder chambers 6 and 7 are always the brake cylinder 2,
2 are connected to each other.

When a pair of pistons 8, 9 and valves 10, 11 are provided, and the oil chambers 26, 27 are always connected, it is necessary to provide valve bodies 34, 35 for the valves 10, 11. If there is only one valve or if the oil chambers 26 and 27 are not connected, the seats 34 and 35 are not necessarily required.

Next, we will discuss the operation.

In the illustrated state, the tank 1 and the brake cylinders 2, 2 are in communication, so the brake cylinders 2, 2 do not operate at low pressure.

Next, in order to turn the vehicle to the left, the upper brake cylinder 2 in the figure is actuated and the lower brake cylinder 2 is released, as follows.

First, step on the left brake pedal (not shown) with your foot and push the upper piston 8 to the right.

At this time, the seat 16 of the passage 14 comes into contact with the valve head 32, and the passage 14 and the cylinder chamber 6 are cut off.

Next, when the piston 8 is pushed further, the oil in the cylinder chamber 6 and the oil chamber 26 is supplied to the upper brake cylinder 2 via the piston entry volume passage 3, and the piston rod of the brake cylinder 2 moves to move the corresponding wheel. Brake. The pressure at this time corresponds to the amount of movement of the piston 8, and the pressure corresponds to the amount of movement of the piston 8.
The braking force is adjusted from small to large depending on the amount of movement.

When the brake pedal is no longer depressed, the piston 8 and the valve 10 are pushed up by the springs 36 and 37 and return to their original positions. At this time, valve 1
Since the oil chamber 26 provided at the back of the oil pressure source 1 becomes negative pressure, the oil from the hydraulic source 1 opens the check valve 45 from the passage 3, and is further introduced through the low pressure passage 46 and the passage 44, thereby preventing a shortage of oil.

On the other hand, the valve body 35 of the lower valve 11 is connected to the passage 29
2, the oil in the upper cylinder chamber 6 is supplied only to the upper brake cylinder 2, and the lower brake cylinder 2 is still connected to the tank 1, so it does not operate.

When a right turn is desired, the lower brake cylinder 2 is operated in the opposite manner to the above, and the upper brake cylinder 2 is released to the tank 1.

On the other hand, if it is desired to brake both left and right wheels at the same time, both left and right brake pedals are depressed to move the two pistons 8 and 9 to the right at the same time. Therefore, the same amount of oil in each cylinder chamber 6, 7 and each oil chamber 26, 27 is simultaneously supplied to each brake cylinder 2, 2, and each wheel is braked with the same pressure.

At this time, since the oil chambers 26 and 27 are in communication, they have the same pressure, and the pressures in the brake cylinders 2 and 2 have the same pressure and are balanced.

2 and 3 relate to other embodiments of the present invention,
An air bleed device is provided in the low-pressure passage, and other structures, functions, and effects are the same as those of the embodiment shown in FIG. Therefore, the same structures are given the same reference numerals, and the details will be omitted.

The caps 22', 23' are formed short, a sleeve 47 facing the caps 22', 23' is inserted into the valve body 5, and the valve 10 is slidably inserted into the sleeve 47. A seat portion 48 and a through hole 40' are formed at the end of the sleeve 47, and the through hole 40' opens into the oil chamber 26.

A passage 49 consisting of notches, grooves, etc. along the length is formed on the outer periphery of the main body of the valve 10, and a poppet-shaped valve body 34' is formed at the end of the main body. Normally, the outer surface of this valve body 34' is the seat portion 4.
8 and is in contact with valve 10 or spring 37
When pushed against this, the valve body 34' separates from the seat portion 48, and the cylinder chamber 6 opens into the oil chamber 26 via the passage portion 49.

The above structure is the same on the valve 11 side.

The cylinder body 5 has a horizontal hole 12' opening into the radial passage 12 of the piston 8, a low pressure passage 46a communicating with the horizontal hole 12', and a through hole 4 of the sleeve 47.
A low pressure passage 46b that opens at 0' is provided, and these low pressure passages 46a and 46b are interconnected and opened and closed via a check valve 45.

For this reason, stop pressing the pedal and press valve 1.
0, the oil chamber 26 becomes slightly negative pressure and the check valve 45 is opened against the spring, and the oil flows from the hydraulic source 1 to the horizontal hole 12' to the low pressure passages 46a, 46.
b- Guided to the oil chamber 26 through the through hole 40' to prevent the oil chamber 26 from running out of oil.

At the rear end of one of the low pressure passages 46b, an air bleed device 50 that is opened and closed to the atmosphere is provided. For this reason, cylinder body 5 has piston 8 and valve 1.
0, and when assembling the master cylinder 4 to the brake cylinder 2, air flows into the cylinder chamber 6,
Even if air remains in the oil chamber 26 or piping, a slight repeated operation of the pedal will release this air into the low pressure passage 46.
b, and can be further discharged to the outside via the air bleed device 50.

[Effect of the idea] According to the present invention, there are the following effects.

Since the valve head of the valve faces the end of the passageway of the piston so that it can be opened and closed, the valve will not be damaged or buckled even if the piston is slid repeatedly, improving sealing performance and ensuring the desired braking performance at all times. Effects can be obtained.

The sealing effect can be further improved by providing a flap-shaped seat at the mouth end of the passage and abutting the poppet-shaped valve head against this seat.

As the piston moves, the entire amount of oil corresponding to the volume of piston entry is supplied to the brake cylinder, so by adjusting the amount of piston movement, a small to large braking operation can be obtained.

The oil chamber at the back of the valve is connected to the hydraulic power source via a check valve, so when the valve returns, the oil from the hydraulic source opens the check valve and is guided to the oil chamber, preventing a lack of oil due to negative pressure in the oil chamber. can be prevented.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of a master cylinder according to an embodiment of the present invention, FIG. 2 is a partial longitudinal sectional front view of a master cylinder according to another embodiment of the invention, and FIG.
The figure is a longitudinal cross-sectional side view taken along the line N--N in FIG. 2. 1... Hydraulic source, 2... Brake cylinder, 3...
... Passage, 4... Master cylinder, 5... Cylinder body, 6, 7... Cylinder chamber, 8, 9...
Piston, 10, 11...Valve, 12, 13,
14, 15... passage, 26, 27... oil chamber, 32
...Valve head, 45...Check valve, 46, 46a,
46b...Low pressure passage.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A master cylinder is provided in the middle of the passage connecting the hydraulic power source and the brake cylinder, and the master cylinder slides between the cylinder body, the cylinder chamber formed in the cylinder body, and the cylinder chamber. It consists of a piston inserted so that it can move freely, and a valve that is also inserted into the cylinder chamber so that it can move up and down.The piston has a passage that connects the hydraulic power source and the cylinder chamber, and the valve of the valve is installed at the mouth end of this passage. A master cylinder device for brakes, characterized in that the heads are facing each other so as to be openable and closable, and further, an oil chamber provided at the back of the valve is opened and closed by a hydraulic power source via a check valve. (2) The brake master cylinder device according to claim 1 of the utility model claim, wherein a pair of cylinder chambers are provided, and a piston and a valve are respectively inserted into each cylinder chamber. (3) An oil chamber is provided at the back of the valve, and this oil chamber is opened and closed with a valve to the cylinder chamber, and each oil chamber communicates through a passage formed in the cylinder body, and this passage is connected to the hydraulic pressure source side. A brake master cylinder device according to claim 1, which is connected to a low pressure passage leading to a hydraulic pressure source, and is provided with a check valve in the middle of the low pressure passage for allowing oil to flow from a hydraulic power source. (4) The brake master cylinder device according to claim 1 of the utility model, wherein the valve is poppet-shaped and is held in a neutral position by springs on both sides.