JP2576677Y2 - Backflow prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a backflow prevention device, for example, a booster as a power source of a brake device for a passenger car or a small truck or the like. The present invention relates to a backflow prevention device for preventing backflow to an engine. (Related Art) As a conventional backflow prevention device, there is one shown in FIGS. 4 to 6, for example. In FIG. 4, reference numeral 1 denotes a backflow prevention device. The backflow prevention device 1 is provided on a vacuum hose 5 that connects the engine 2 and the vacuum booster 3. The backflow prevention device 1 comprises a check valve _1A , and the suction negative pressure of the engine 2 is supplied to the vacuum booster 3 via the check valve _1A , and the vacuum booster 3 is connected to the check valve.
The backflow of the negative pressure is prevented by 1 _A , and the predetermined negative pressure is maintained. The vacuum booster 3 is arranged between the brake pedal 6 and the master cylinder 7 of the braking device. When the brake pedal 6 is depressed (brake-on), the vacuum booster 3 boosts in proportion to the depression force of the brake pedal 6, and Acts on a piston not shown. (Problems to be Solved by the Invention) However, the suction negative pressure generated in the engine 2 is generated by rotation in the engine 2 and has a fluctuation of the negative pressure corresponding to the engine speed. For this reason, when the foot is removed from the brake pedal 6 (brake off) and the vacuum booster 3 is charged with a negative pressure, the vacuum hose 5 and the check valve _1A resonate with the negative pressure fluctuation, as shown in FIG. There is a problem that chattering noise is generated at the end A of the negative pressure filling. In particular, in the case of a passenger car or a cab-over type small truck, the vacuum booster 3 is often installed in the vehicle cabin in order to shorten the piping length. Therefore, the vibration noise of the vacuum hose 5 and the check valve _1A is generated in the cabin. There is a problem that it is noisy to the occupants. Conventionally, as a countermeasure, an orifice 8 may be provided in the vacuum hose 5 between the legitimate flow prevention device 1 and the engine 2 as shown in FIG. Can be reduced somewhat. However, on the other hand, when the pedaling force is removed from the brake pedal 6 and the negative pressure of the engine 2 is charged into the vacuum booster 3, it takes time, and the negative pressure charging performance is reduced. For this reason, there is also a problem that the filling negative pressure in the vacuum booster 3 decreases and the depression force of the brake pedal increases. Accordingly, an object of the present invention is to suppress the chattering sound of the vacuum booster that occurs at the end of negative pressure charging after the brake pedal is depressed, without impairing the efficiency of negative pressure charging to the vacuum booster. (Means for Solving the Problems) The check device according to the present invention includes two check valves connected in series between the engine and the vacuum booster to prevent the negative flow of the negative pressure from the vacuum booster to the engine. 2 above
The valve opening pressures of the check valves are made different, and an orifice is provided in parallel with the check valve that is closed earlier at the end of negative pressure filling of the vacuum booster, and the valve opening pressure is:
It is determined by the relationship between the negative pressure of the engine and the negative pressure of the vacuum booster. (Operation) In this invention, when the brake pedal is depressed, the negative pressure of the vacuum booster is lost and the negative pressure between the engine and the vacuum booster expands. At this time, the two check valves reduce the large negative pressure difference. These two are currently open.
The negative pressure can be efficiently supplied from the engine to the vacuum booster through the small flow path resistance of each check valve, thereby achieving the object. On the other hand, as the vacuum booster approaches the end of negative pressure charging, the negative pressure difference decreases, and finally one check valve (the check valve that closes earlier at the end of negative pressure filling of the vacuum booster) closes first. I do. Therefore, the subsequent negative pressure charging is performed through the orifice having a large flow path resistance, and it is possible to suppress the negative pressure fluctuation transmitted from the engine to the vacuum booster, thereby suppressing chatter noise generated at the end of the negative pressure charging. Can achieve the task. Since the ultimate value of the negative pressure filling of the vacuum booster is a value obtained by subtracting the valve opening pressure of the other check valve from the engine negative pressure, the valve closing pressure should of course be as low as possible. (Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1 to 3 are views showing one embodiment of a backflow prevention device according to the present invention. In FIG. 1, reference numeral 11 denotes a backflow prevention device. The backflow prevention device 11 is provided on a vacuum hose 15 that connects between the engine 12 and the vacuum booster 13. The backflow prevention device 11 prevents the suction negative pressure of the engine 12 supplied from the engine 12 to the vacuum booster 13 through the vacuum hose 15 from flowing back to the engine 12. Backflow prevention device
11 is a normal conventional check valve on the vacuum booster 13 side
It consists a check valve 11 _B of the engine 12 side, which is connected in series with 11 _A and the check valve 11 _A. Here, the check valve 11 _A and the check valve 11 _B has two check valves as described in the Summary of the invention,
That is, it corresponds to two check valves that are connected in series between the engine 12 and the vacuum booster 13 and that prevent the negative pressure from flowing back from the vacuum booster 13 to the engine 12. The check valve 11 _B, as shown in FIG. 2, a cylindrical large diameter portion 17 of larger diameter, is connected to both sides of the large diameter portion 17, and small diameter connecting the vacuum hose 15 (not shown) Small cylindrical section
And a housing 19 comprising the same. The large diameter portion 17 and the small diameter portion 18 are formed with a gas flow path 22 that applies the negative suction pressure of the engine 12 to the vacuum booster 13. A rod-shaped valve body 20 is housed in the large-diameter portion 17, the valve body 20 is movable in the axial direction, and is urged by a spring 21 toward the vacuum booster 13, and the flange portion 20 a of the valve body 20 is connected to the step portion 18 a. The gas flow path 22 is closed by contact. Valve opening pressure P _B of the check valve 11 _B is a predetermined pressure only greater than the opening pressure P _A of the check valve 11 _A, and the check valve 11 _A generates a chattering noise, vacuum hose 15 begins to resonate It closes the negative pressure P _T is lower than the negative pressure P _S.
That is, the valve is closed when the negative pressure difference on both sides of the valve is large.
The valve element 20 has an orifice 24 along the axis sensor, and the orifice 24 forms a flow path 20b parallel to the flow path formed by the valve element 20 and the step 18a. Further, the vacuum booster 13 is provided between the brake pedal 26 and the master cylinder 27 of the braking device, boosts in proportion to the depression force of the brake pedal 26, operates on the piston of the master cylinder 27, and facilitates the braking action. When the brake booster 13 is depressed (when the brake is turned on), the vacuum booster 13 operates a boost proportional to the depressing force due to the pressure difference between the negative pressure on both sides of the built-in diaphragm-shaped power piston 28 and the standby pressure. Then, the atmospheric pressure flows into the vacuum booster 13 to reduce the negative pressure. When the depression force of the brake pedal 26 is removed, the backflow prevention device 11 opens to start charging the negative pressure. Next, the operation will be described. Now, except for the depression force of the brake pedal 26 (the braking-off), the check valve 11 _B and the check valve 11 _A of the negative pressure low in the vacuum booster 13 decreases as shown in FIG. 3 is opened It rises to a high negative pressure by high engine 12 intake negative pressure P _E through. At the end of negative pressure filling, check valve 11
_B is closed by negative pressure P _T is lower than the negative pressure P _S of the check valve 11 _A starts to generate the chattering noise. Thereafter, a high engine 12 negative pressure increases the negative pressure as the vacuum booster 13 of the check valve 11 _A which is the orifice 24 and the opening of the check valve 11 _B. The negative pressure fluctuations orifice 24 of the engine 12, is relaxed, the negative pressure of the vacuum booster 13 as shown in FIG. 3, smoothly rises to conventional same predetermined high saturation negative pressure P _U. Further, when the brake-off, the check valve in the valve opening state from the low negative pressure within the vacuum booster 13 11 _B and the check valve 1
The filling performance that increases to a high negative pressure of the engine 12 through 1 _A is maintained at the same level as before. Also, a check valve 11 _B is caused to malfunction, and the check valve 11 _A and the engine 12, the check valve 11 _B in parallel with the orifice
24 communicates with the gas flow path 20b inside the
The suction negative pressure of No. 2 is reliably charged into the vacuum booster 13. (Effects) According to the present invention, since the opening pressures of the two check valves are made different and an orifice is provided in parallel with the check valve having a lower valve opening pressure, the vacuum booster is filled with a negative pressure. A backflow prevention device capable of suppressing chattering noise of the vacuum booster generated at the end of negative pressure charging after the brake pedal is depressed without deteriorating the efficiency of the brake pedal can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 are views showing an embodiment of a backflow prevention device according to the present invention, FIG. 1 is an overall conceptual diagram, FIG. FIG. 3 is a graph showing the operation.
4 to 6 are views showing a conventional backflow prevention device.
FIG. 5 is an overall conceptual diagram of the example, FIG. 5 is an overall conceptual diagram of another example, and FIG. 6 is a graph showing its operation. 11 ... check valve, 11 _A ... check valve (check valve), 1
1 _B ... check valve, 12 ... engine, 13 ... vacuum booster, 15 ... vacuum hose, 19 ... housing, 20
…… Valve element, 21 …… Spring, 22 …… Gas flow path, 24 ……
Orifice.

Claims (1)

(57) [Rules for requesting registration of utility model] Two check valves for preventing backflow of negative pressure from the vacuum booster to the engine are connected in series between the engine and the vacuum booster, and the opening pressures of the two check valves are made different from each other. An orifice is provided in parallel with the check valve that is closed earlier at the end of negative pressure charging to the valve, and the valve opening pressure is determined by the relationship between the negative pressure of the engine and the negative pressure of the vacuum booster. Characteristic backflow prevention device.