JP2008155792A - Negative pressure booster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative pressure booster capable of completely returning a valve seat member and a valve body to a usual position when a brake pedal is returned. <P>SOLUTION: In the negative pressure booster, when the valve seat member movably provided between a first position where it is positioned at an output area of a predetermined output or less and a second position where it is positioned at an output area larger than the predetermined output is moved to the predetermined position, a vacuum valve is opened. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention belongs to a technical field of a negative pressure booster used for a brake booster or the like, and particularly in a vehicle in which deceleration during normal brake operation such as a vehicle having a large vehicle weight is obtained according to a pedal stroke amount. The present invention belongs to the technical field of a negative pressure booster used in a brake booster of a brake system.

  2. Description of the Related Art Conventionally, in a brake system for an automobile such as a passenger car, a negative pressure booster using negative pressure is used as a brake booster. In such a conventional general negative pressure booster, the power piston is divided into a constant pressure chamber into which a normal negative pressure is introduced and a variable pressure chamber in which the pressure changes. Then, during normal brake operation by normal depression of the brake pedal, the control valve is switched by the advance of the input shaft, and the atmosphere is introduced into the variable pressure chamber. As a result, a differential pressure is generated between the variable pressure chamber and the constant pressure chamber, and the power piston moves forward, so the negative pressure booster boosts the input of the input shaft (that is, pedal effort) by a predetermined servo ratio and outputs it. To do. The master cylinder generates a master cylinder pressure by the output of the negative pressure booster, and the wheel cylinder is operated by the master cylinder pressure to operate the normal brake.

  By the way, in vehicles such as 1BOX vehicles and RV vehicles, vehicle weight and loading load tend to increase in recent years. For this reason, in such vehicles, the amount of brake operation (the amount of pedal stroke) required during normal brake operation increases with the increase in the weight and load capacity of these vehicles. Thus, since the amount of brake operation by the driver increases during normal braking operation, it cannot be said that the brake feeling is good.

  Therefore, a negative pressure booster has been proposed that can obtain a large output even with a small pedal depression force, that is, a small input, and can perform a brake assist operation in an emergency (see Patent Document 1).

  It can be considered that the negative pressure booster disclosed in Patent Document 1 is applied to a vehicle that requires a higher deceleration than that during normal braking operation to obtain a large deceleration with a small pedal effort. At this time, since the pedal stroke is shortened, the brake feeling is improved.

  However, in the negative pressure booster disclosed in Patent Document 1, the BA operation is performed and the function of shortening the pedal stroke is exhibited only when the pedal depression speed is faster than that during normal braking (fast depression). For this reason, since the pedal stroke is not shortened except when the pedal depression speed is high, it is difficult to obtain a good brake feeling. In addition, a problem of generation of operation noise due to engagement / disengagement of the engagement portion of the BA mechanism is expected.

  In addition, it has been proposed to reduce the servo ratio in the early stage of braking of the brake booster and increase the servo ratio in the later stage of braking (see Patent Document 2).

  The negative pressure booster disclosed in Patent Document 2 reduces the servo ratio at the initial stage of braking within the normal brake operation region and increases the servo ratio at the later stage of braking. Therefore, this negative pressure booster is not considered for vehicle brake systems that require higher deceleration than during normal braking operation. Moreover, in this negative pressure booster, although the brake feeling is improved by hysteresis when the brake pedal is depressed and released, the brake feeling is poor due to an increase in the pedal stroke during high deceleration operation. Is not considered.

  Therefore, the present applicant solves these problems, shortens the stroke of the input member in the output region larger than the predetermined output, improves the operational feeling, and has a simpler structure and easier assembly. In addition, an inexpensive negative pressure booster has been proposed (see Patent Document 3).

In the present invention, during normal braking in the reduced speed region, the force due to the pressure difference between the pressure in the variable pressure chamber and the pressure in the constant pressure chamber, which is applied to the vacuum valve seat member, Therefore, the vacuum valve seat member does not move, the normal brake operation is performed with a small servo ratio, and during the normal brake operation in the middle / high deceleration region, the force due to the pressure difference is the aforementioned spring. When the vacuum valve seat member moves rearward while pushing the valve body, the brake operation for medium to high deceleration is performed while the pedal stroke is shortened.
JP 2001-341632 A JP 11-278245 A International Publication No. 2004/101340

  However, in the invention described in Patent Document 3, the load caused by the spring 104 is affected by the sliding resistance of the seal member 103 between the vacuum valve seat member 101 and the valve body 102 as shown in the schematic diagram of FIG. When the brake pedal is returned and the plunger 105 is returned, the vacuum valve seat member 101 may not completely return to the normal position. In such a case, the vacuum valve 107 composed of the vacuum valve seat member 101 and the valve body 106 cannot be opened before the valve body 102 returns to the normal position, and the variable pressure chamber pressure cannot be exhausted. The body 102 cannot return and becomes brake dragging in a state where the brake is applied.

  The present invention has been made in view of such circumstances, and an object of the present invention is to shorten the stroke of the input member in an output region larger than a predetermined output, improve the operation feeling, and simplify the structure. In a negative pressure booster that is easy and inexpensive to assemble and that operates smoothly, the valve seat opens by allowing the vacuum valve to open and exhaust the pressure in the transformer chamber when the brake pedal is returned. And a negative pressure booster capable of returning the valve body to the normal position.

  In order to solve the above-described problems, a negative pressure booster according to a first aspect of the present invention includes a valve body that is disposed so as to be movable forward and backward with respect to the inside of the shell, and is provided in the valve body so as to pass through the inside of the shell. A power piston partitioned into a constant pressure chamber into which negative pressure is introduced and a variable pressure chamber into which air is introduced during operation; a valve plunger connected to an input shaft and slidably disposed in the valve body; A vacuum valve for controlling communication or blocking between the constant pressure chamber and the variable pressure chamber by operation of a valve plunger, and an atmospheric valve for controlling blocking or communication between the variable pressure chamber and at least the atmosphere. The valve includes a valve body and a vacuum valve seat on which the valve body can be seated / separated, and the atmospheric valve includes the valve body and an atmospheric valve seat on which the valve body can be seated / separated, and the vacuum valve The valve seat member provided with the seat is the valve body. The valve seat member is movably provided between a first position located in an output region below a predetermined output and a second position located in an output region larger than the predetermined output. The negative pressure booster controlled by the pressure of the chamber is characterized by comprising vacuum valve opening means for opening the vacuum valve when the valve seat member moves to a predetermined position.

  The negative pressure booster of the invention of claim 2 is characterized in that the movement of the valve seat member is controlled by a pressure difference between the pressure in the variable pressure chamber and the pressure in the constant pressure chamber.

  Further, in the negative pressure booster according to the invention of claim 3, the vacuum valve opening means has a shell latching portion latched on the shell when the valve seat member moves to the predetermined position. And

  According to a fourth aspect of the present invention, the vacuum valve opening means includes a leg portion of the valve seat member.

  Further, in the negative pressure booster of the invention of claim 5, the vacuum valve opening means has a leg portion of the valve seat member and the shell hooking portion hooked on the shell at one end, It is characterized by comprising a key member having a leg hooking portion hooked on the leg portion of the valve seat member on the side.

  According to the present invention, the valve seat member and the valve body can be returned to the normal positions by opening the vacuum valve when the brake pedal is returned and exhausting the pressure in the variable pressure chamber. Moreover, since the existing member is used, it can be provided at a low cost without increasing the number of parts.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example in which the negative pressure booster according to the present invention is applied to a brake booster in a non-operating state, and FIG. 2 is an enlarged view of a vacuum valve and an atmospheric valve in FIG. FIG. 3 is a partially enlarged sectional view in an operating state. In the following description, “front” and “rear” indicate “left” and “right” in each figure, respectively.

  First, in the negative pressure booster of this example, the same components as those of a conventional general negative pressure booster will be briefly described. 1 and 2, 1 is a negative pressure booster, 2 is a front shell, 3 is a rear shell, 4 is a valve body, 5 is a power piston member 6 attached to the valve body 4, the valve body 4, and both shells 2. , 3 is a power piston composed of a diaphragm 7 provided between the two shells 2 and 3, one of two chambers partitioned by the power piston 5, and a constant pressure chamber into which negative pressure is normally introduced , 9 is the other of the aforementioned two chambers, a variable pressure chamber into which atmospheric pressure is introduced when the negative pressure booster 1 is operated, 10 is a valve plunger, 11 is connected to a brake pedal (not shown), and the valve plunger 10 is An input shaft for controlling the operation, 12 is a valve body provided on the valve body 4, 13 is an annular vacuum valve seat, 14 is an annular atmospheric valve seat formed on the valve plunger 10, and 15 is a valve body 12 and a vacuum valve seat. 13 and according The vacuum valve 16 is constituted by an atmospheric valve constituted by a valve body 12 and an atmospheric valve seat 14, and 17 is constituted by a vacuum valve 15 and an atmospheric valve 16, and the variable pressure chamber 9 is selectively used as a constant pressure chamber 8 and the atmospheric air. A control valve for switching control to 18, a valve spring that constantly urges the valve body 12 in the direction in which the valve body 12 is seated on the vacuum valve seat 13, 19 an atmosphere introduction passage, 20 a vacuum passage, 21 a shell latching portion 21 a at one end, A leg hooking portion 21b on the other side is inserted into a key groove 4a formed in the valve body 4, and the relative movement of the valve plunger 10 with respect to the valve body 4 is defined by the axial width of the key groove 4a. A key member as an example of a vacuum valve opening means that regulates the retreat limit of the valve body 4 and the valve plunger 10, 22 is a spacing member, 23 is a reaction disk, 24 is an output shaft, and 25 is Return sp A ring 26 is a negative pressure introduction passage connected to a negative pressure source (not shown).

  As in the case of a conventional general negative pressure booster, the output shaft 24 penetrates the front shell 2 so as to be movable, and the constant pressure chamber 8 is connected to the atmosphere by an appropriate sealing means (not shown) in this penetration portion. Airtightly shut off. Although not shown, the output shaft 24 operates the piston of the master cylinder. As in the prior art, the valve body 4 penetrates the rear shell 3 in a movable manner, and the variable pressure chamber 9 is airtight from the atmosphere with a cup seal (not shown in the figure) shown in the penetration portion. Blocked.

  Furthermore, the valve body 12 includes an atmospheric valve portion 12a that can be seated on the atmospheric valve seat 14, and a vacuum valve portion 12b that can be seated on the vacuum valve seat 13, and these atmospheric valve portion 12a and vacuum valve portion 12b are They are connected by a connector 12c and are moved together. The vacuum valve portion 12b and the vacuum valve seat 13 constitute a vacuum valve 15, and the atmospheric valve portion 12a and the atmospheric valve seat 14 constitute an atmospheric valve 16.

  Next, the structure of the characteristic part different from the past of the negative pressure booster 1 of this example is demonstrated. As shown in FIG. 2, in the negative pressure booster 1 of this example, a vacuum valve seat member (corresponding to the valve seat member of the present invention) 27 is slidably fitted into the axial inner hole 4 b of the valve body 4. The rear end portion 27a of the vacuum valve seat member 27 is slidably connected to the valve body 4 via a spring 31, and the aforementioned vacuum valve seat 13 is connected to the intermediate portion 27b of the vacuum valve seat member 27. Is formed. Therefore, the vacuum valve seat 13 can also be moved relative to the valve body 4. Further, the front end of the vacuum valve seat member 27 is formed with a leg portion 27 c having a latching portion 27 d that is hooked on the key member 21.

  A seal member 28 such as a cup seal provided on the outer peripheral surface of the vacuum valve seat member 27 is at least a vacuum valve between the inner peripheral surface of the inner hole 4b of the valve body 4 and the outer peripheral surface of the vacuum valve seat member 27. The seat member 27 is kept airtight so as to prevent the flow of air from the front end toward the rear end.

  Further, as shown in the partially enlarged view of FIG. 3, in a state where the vacuum valve portion 12 b of the valve body 12 is seated on the vacuum valve seat 13, the vacuum valve seat member 27 has an annular shape on the outer peripheral side from the seating position of the vacuum valve portion 12 b. The outer surface 27e communicates with the constant pressure chamber 8 at all times, and the pressure of the constant pressure chamber 8 always acts on the outer surface 27e. Further, the inner side surface 27f of the vacuum valve seat 13 of the vacuum valve seat member 27 is always in communication with the variable pressure chamber 9, and the pressure of the variable pressure chamber 9 is always applied to these inner side surfaces 27f. Therefore, when a pressure difference is generated between the pressure in the variable pressure chamber 9 and the pressure in the constant pressure chamber 8 during the operation of the negative pressure booster 1, the force due to the pressure difference is applied to the vacuum valve seat member 27 backward. become.

  As shown in FIG. 2, a cylindrical holder portion 30 is formed integrally with the valve body 4 at the center of the front end portion of the valve body 4. An annular flange 30 a that encloses the reaction disk 23 and the output shaft 24 is formed at the front end portion of the holder portion 30.

  A spacing member 22 is slidably provided in the holder portion 30. When the negative pressure booster 1 is not in operation, a predetermined gap C in the axial direction is set between the front end face of the spacing member 22 and the rear end face of the reaction disk 23 facing the front end face of the spacing member 22. Has been.

  Next, the actual operation of the negative pressure booster 1 of this example will be described with reference to FIGS. 4 to 8 are conceptual diagrams of each operating state of the negative pressure booster 1. FIG.

  First, the non-operation of the negative pressure booster will be described. A negative pressure is always introduced into the constant pressure chamber 8 of the negative pressure booster 1 through the negative pressure introduction passage 26. Further, in the non-operating state of the negative pressure booster 1 shown in FIG. 4, the shell hooking portion 21 a of the key member 21 is in contact with the rear shell 3 and is in a backward limit. Accordingly, the valve member 4 and the valve plunger 10 are set to the backward limit by the key member 21, and the power piston 5, the input shaft 11 and the output shaft 24 in FIG. 1 are also set to the backward limit. In this non-operating state, the atmospheric valve portion 12a of the valve body 12 is seated on the atmospheric valve seat 14 and the atmospheric valve 16 is closed, and the vacuum valve portion 12b of the valve body 12 is separated from the vacuum valve seat 13 and is vacuum valved. 15 is open. Therefore, the variable pressure chamber 9 is cut off from the atmosphere and communicates with the constant pressure chamber 8 so that a negative pressure is introduced into the variable pressure chamber 9, so that substantially no differential pressure is generated between the variable pressure chamber 9 and the constant pressure chamber 8. .

For this reason, the force due to the pressure difference is not applied to the vacuum valve seat member 27 backward, the vacuum valve seat member 27 is the spring force of the spring 31, and a part of the intermediate portion 27 b is part of the valve body 4. It is positioned at a position in contact with the bottom 4b ₁ of the inner hole 4b.

  Next, the normal brake operation in the reduced speed region of the negative pressure booster will be described. When the brake pedal is stepped on at the stepping speed at the time of normal braking operation to perform normal braking, the input shaft 11 moves forward and the valve plunger 10 moves forward. Then, as shown in FIG. 5, as the valve plunger 10 advances, the vacuum valve portion 12 b of the valve body 12 is seated on the vacuum valve seat 13, the vacuum valve 15 is closed, and the atmospheric valve seat 14 is the atmospheric valve of the valve body 12. Apart from the part 12a, the atmospheric valve 16 opens. That is, the variable pressure chamber 9 is disconnected from the constant pressure chamber 8 and communicated with the atmosphere. Therefore, the atmosphere is introduced into the variable pressure chamber 9 through the atmosphere introduction passage 19 and the open atmosphere valve 16. As a result, a differential pressure is generated between the variable pressure chamber 9 and the constant pressure chamber 8, the power piston 5 moves forward, the output shaft 24 moves forward via the valve body 4, and the piston of the master cylinder (not shown) moves forward.

  Further, although the spacing member 22 is also moved forward by the advancement of the valve plunger 10, the spacing member 22 has not yet reached the reaction disk 23 by the gap C. Therefore, since the reaction force is not transmitted from the reaction disk 23 to the spacing member 22 from the output shaft 24, this reaction force is not transmitted to the brake pedal via the valve plunger 10 and the input shaft 11. When the input shaft 11 further advances, the power piston 5 further advances, and the piston of the master cylinder further advances through the valve body 4 and the output shaft 24.

  When the loss stroke of the brake system after the master cylinder disappears, the negative pressure booster 1 substantially generates an output, and the master cylinder generates a master cylinder pressure (hydraulic pressure) with this output. The wheel cylinder is activated to generate braking force.

  At this time, due to the reaction force applied from the master cylinder to the output shaft 24, the reaction disk 23 bulges back as shown in FIG. 6, the gap C disappears, and the reaction disk 23 comes into contact with the spacing member 22. As a result, the reaction force from the output shaft 24 is transmitted from the reaction disk 23 to the spacing member 22 and further transmitted to the brake pedal via the valve plunger 10 and the input shaft 11 to be sensed by the driver. That is, the negative pressure booster 1 exhibits a jumping characteristic during normal braking operation. This jumping characteristic is almost the same as the jumping characteristic of a conventional general negative pressure booster.

  When the normal brake is operated in the reduction speed (low G) region, the input (that is, the pedal effort) of the negative pressure booster 1 is relatively small. In this reduction speed (low G) region, the output is an output region that is equal to or lower than a predetermined output. For this reason, the vacuum valve seat member 27 does not move, and the servo ratio becomes a relatively small servo ratio SR1 which is substantially the same as that in the conventional normal brake operation. Therefore, when the output of the negative pressure booster 1 becomes a magnitude obtained by boosting the input of the input shaft 11 by the pedal depression force by this servo ratio SR1, the atmospheric valve portion 12a is seated on the atmospheric valve seat 14 and the atmospheric valve 16 is also It closes and it will be in the balance state of intermediate load (the vacuum valve 15 has already closed with the vacuum valve part 12b sitting on the vacuum valve seat 13). Thus, as shown in FIG. 6, in the reduced speed (low G) region, the normal brake is operated with a brake force obtained by boosting the pedal depression force during normal brake operation by the servo ratio SR1.

  When the brake pedal is released in order to release the normal brake from the state where both the atmospheric valve 16 and the vacuum valve 15 of the negative pressure booster 1 in the normal pressure operation shown in FIG. 6 are closed, the input shaft 11 and Although both the valve plungers 10 retreat, the valve body 4 and the vacuum valve seat member 27 do not retreat immediately because air (atmosphere) is introduced into the variable pressure chamber 9. Thereby, since the atmospheric valve seat 14 of the valve plunger 10 presses the atmospheric valve portion 12a of the valve body 12 backward, the vacuum valve portion 12b is separated from the vacuum valve seat 13, and the vacuum valve 15 is opened. Then, the pressure introduced into the variable pressure chamber 9 is released to the vacuum source side through the opened vacuum valve 15, vacuum passage 20, constant pressure chamber 8, and negative pressure introduction passage 26.

  As a result, the pressure in the variable pressure chamber 9 is reduced and the differential pressure between the variable pressure chamber 9 and the constant pressure chamber 8 is reduced, so that the power piston 5, the valve body 4 and the output shaft 24 are retracted by the spring force of the return spring 25. . As the valve body 4 is retracted, the piston of the master cylinder and the output shaft 24 are also retracted by the spring force of the return spring of the piston of the master cylinder, and the normal brake starts to be released.

When the shell hooking portion 21a of the key member 21 comes into contact with the rear shell 3, the key member 21 stops and does not retract further. However, the valve body 4, the valve plunger 10, the vacuum valve seat member 27, and the input shaft 11 are further retracted. Then, the valve plunger 10 abuts against the key member 21 as shown in FIG. 2 and does not move any further, and the front end 4a ₁ of the key groove 4a of the valve body 4 contacts the key member 21 as shown in FIG. In contact with it, the valve body 4 does not retract further. Thus, the negative pressure booster 1 is in the initial inoperative state shown in FIG. Therefore, the master cylinder is deactivated and the master cylinder pressure disappears, and the wheel cylinder is deactivated and the braking force disappears, so that the normal brake is released.

  Next, a description will be given of the normal brake operation in the medium / high deceleration region of the negative pressure booster. When normal braking is performed in a medium to high deceleration range where the deceleration is greater than the reduction speed (low G) during normal braking operation, the input of the negative pressure booster 1 (that is, the pedal effort) is reduced (low G). ) Set larger than normal brake operation in the area. As the input increases, the pressure Pb of the variable pressure chamber 9 also increases. However, as shown in FIG. 9, when the pressure Pb of the variable pressure chamber 9 exceeds the set pressure Pbm, the input / output characteristics of the negative pressure booster 1 are medium to high deceleration. (Medium-high G) region, and the booster output Fvb is an output region of the servo ratio SR2 that is larger than the predetermined output.

  In this medium / high deceleration (medium / high G) region, when the pressure Pb of the variable pressure chamber 9 becomes equal to or higher than the set pressure Pbm, the reaction disk 23 is further moved backward as shown in FIG. 7 by the reaction force applied to the output shaft 24 from the master cylinder. Swells and presses the spacing member 22. Then, as shown in FIG. 10, the balance between the pressure Pb of the inner surface 27 f communicated with the variable pressure chamber 9, the pressure Pv of the outer surface 27 e communicated with the constant pressure chamber 8, and the load Fxr that deflects the spring 31. As a result, the vacuum valve seat member 27 moves backward by a movement amount Xr that is substantially the same as the length of the reaction disk 23 bulging while pushing the valve body 12. At this time, the movement amount Xr of the vacuum valve seat member 27 is obtained by Xr = Fxr / Ksr obtained by dividing the load Fxr for bending the spring 31 by the spring constant Ksr of the spring 31. Therefore, as shown in FIG. 9, in the middle and high G region, the servo ratio becomes a servo ratio SR2 larger than that in the conventional normal brake operation as described above. That is, when the booster output Fvb of the negative pressure booster 1 has a magnitude obtained by boosting the input Fi of the input shaft 11 by the servo ratio SR2, the atmospheric valve portion 12a is seated on the atmospheric valve seat 14 as described above. The atmospheric valve 16 is also closed and the intermediate load is balanced (the vacuum valve 15 is already closed with the vacuum valve portion 12b seated on the vacuum valve seat 13). Thus, in the middle / high deceleration (medium / high G) region, the brake is operated with a booster output Fvb larger than that in the normal braking operation in the reduced velocity (low G) region in which the pedal depression force is boosted by the servo ratio SR2. In this case, the negative pressure booster 1 has a large pedal depression force, that is, the input Fi of the negative pressure booster 1 in this medium / high deceleration (medium / high G) region, but the servo ratio SR1 is input during normal brake operation. With the same input as Fi, a booster output Fvb larger than that at the time of normal brake operation can be obtained.

  Further, when operating in the medium / high deceleration (medium / high G) region, the vacuum valve seat member 27 moves backward by the input shaft stroke Si corresponding to the movement amount Xr, compared to when operating in the reduced speed (low G) region. The output stroke increases in accordance with the input shaft stroke Si. In other words, when the same booster output Fvb is obtained as shown in FIG. 11, the input shaft stroke Si at the time when the variable pressure chamber 9 in the medium / high deceleration (medium / high G) region indicated by the solid line reaches the atmospheric pressure Pa is indicated by the dotted line. The servo ratio SR1 in the reduction speed (low G) region is substantially smaller than the input shaft stroke Si during normal operation by the stroke amount Xre, and the stroke of the input shaft 11, that is, the stroke of the brake pedal is shortened.

  When the vacuum valve seat member 27 shown in FIG. 7 is in operation, when the atmospheric pressure valve 16 and the vacuum valve 15 of the negative pressure booster 1 are both closed, the brake pedal is released to release the normal brake. In the same manner as described above, the vacuum valve 15 is opened, and the pressure introduced into the variable pressure chamber 9 is released to the vacuum source side through the opened vacuum valve 15, vacuum passage 20, constant pressure chamber 8, and negative pressure introduction passage 26. The

  As a result, the pressure in the variable pressure chamber 9 decreases as described above, and the power piston 5, the valve body 4, and the output shaft 24 are retracted by the spring force of the return spring 25. As the valve body 4 is retracted, the piston of the master cylinder and the output shaft 24 are also retracted by the spring force of the return spring of the piston of the master cylinder, and the release of the brake is started.

  When the pressure Pb in the variable pressure chamber 9 does not satisfy the set pressure Pbm, the vacuum valve seat member 27 is moved relatively forward with respect to the valve body 4 by the spring load of the spring 31, and the vacuum valve seat member 27 is The inoperative position shown in FIG. As a result, the vacuum valve portion 12b is greatly separated from the vacuum valve seat 13 and the vacuum valve 15 is opened widely, so that a large amount of air in the variable pressure chamber 9 is discharged, and normal braking operation is performed in the reduced speed (low G) region. It becomes a state. Thereafter, the same as in the case of the normal brake operation in the above-described reduction speed (low G) region, all the moved members of the negative pressure booster 1 are finally in the non-operation position shown in FIG. The brake by the input larger than the normal brake operation in the speed (low G) region is released.

  Next, due to the sliding resistance of the seal member 28 between the vacuum valve seat member 27 and the valve body 4, the load by the spring 31 is insufficient, the brake pedal is returned, and the vacuum valve seat member 27 is returned when the plunger 10 returns. A case will be described where cannot return to the normal position.

  In the present embodiment, a key member 21 that is inserted into a key groove 4 a formed in the valve body 4 and can be hooked on the rear shell 3 at one end and on the valve plunger 10 at the other end is provided. The vacuum valve seat member 27 is hooked to the leg hooking portion 21b of the key member 21 at a hooking portion 27d formed on the leg portion 27c. The key member 21 is a U-shaped member, and the leg portion 27c of the vacuum valve seat member 27 is inserted therethrough, and the latching portion 27d at the tip divided into two branches is latched to the leg latching portion 21b of the key member 21. Is done.

  When the brake pedal is released, the valve plunger 10 moves backward. However, the vacuum valve seat member 27 remains without returning to the normal position due to the sliding resistance of the seal member 28 with the valve body 4. From this state, when the valve plunger 10 is retracted to a predetermined position, the key member 21 comes into contact, and the key member 21 is also retracted. When the key member 21 moves backward and comes into contact with the rear shell 3 at one end, the key member 21 stops so as to be sandwiched between the rear shell 3 and the valve plunger 10. In this state, as shown in FIG. 8, the vacuum valve seat member 27 is not further retracted when the latching portion 27 d comes into contact with the leg latching portion 21 b of the key member 21, and the vacuum valve of the valve body 12 It sets so that a clearance gap may be made between the part 12b and the vacuum valve seat 13 of the vacuum valve seat member 27. Then, the vacuum valve 15 is opened, and the pressure introduced into the variable pressure chamber 9 is released to the vacuum source side through the opened vacuum valve 15, vacuum passage 20, constant pressure chamber 8, and negative pressure introduction passage 26.

  As a result, the pressure in the variable pressure chamber 9 is reduced, and the power piston 5, the valve body 4, and the output shaft 24 are retracted by the spring force of the return spring 25. As the valve body 4 is retracted, the piston of the master cylinder and the output shaft 24 are also retracted by the spring force of the return spring of the piston of the master cylinder, and the release of the brake is started.

According to the negative pressure booster 1 of this example applied to the brake system in this way,
When the brake pedal is returned, the vacuum valve 15 is opened so that the pressure in the variable pressure chamber can be exhausted, whereby the vacuum valve seat member 27 and the valve body 4 can be returned to the normal positions.

  In the present embodiment, the vacuum valve opening means is configured by hooking the leg portion 27c of the vacuum valve seat member 27 to the key member 21, but the present invention is not limited thereto, and other members may be used. For example, the key member 21 is a U-shaped bifurcated member, the leg portion 27 c of the vacuum valve seat member 27 is extended, passes through the U-shape of the key member 21, and extends until it is hooked on the rear shell 3. You may comprise by forming in L shape.

  Further, the predetermined position at which the vacuum valve 15 is opened by the vacuum valve opening means comprising the leg portion 27d of the vacuum valve seat member 27 and the key member 21 may be set anywhere, but in particular, the pressure in the variable pressure chamber 9 is substantially high. The position where the atmospheric pressure Pa is achieved is efficient.

It is sectional drawing which shows the example applied to the brake booster of embodiment of the negative pressure booster which concerns on this invention in a non-operation state. It is a partial expanded sectional view which expands and shows the part of the vacuum valve and atmospheric valve in FIG. It is the elements on larger scale in the state where the vacuum valve part sat down on the vacuum valve seat. It is the schematic which shows the non-operation state of the negative pressure booster of the example shown in FIG. It is the schematic which shows the state at the time of the normal brake action start of the negative pressure booster of the example shown in FIG. It is the schematic which shows the state of the reaction force start of the negative pressure booster of the example shown in FIG. It is the schematic which shows the state at the time of medium and high deceleration of the negative pressure booster of the example shown in FIG. It is the schematic which shows the state of the vacuum valve opening at the time of medium-high deceleration of the negative pressure booster of the example shown in FIG. It is a figure which shows the input-output characteristic of the negative pressure booster of the example shown in FIG. It is a figure which shows the pressure of the variable pressure chamber of the negative pressure booster of the example shown in FIG. 1, and the moving distance of a vacuum valve seat member. It is a figure which shows the booster output with respect to the input stroke of the negative pressure booster of the example shown in FIG. It is the schematic of the conventional negative pressure booster.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Negative pressure booster, 2 ... Front shell, 3 ... Rear shell, 4 ... Valve body, 5 ... Power piston, 8 ... Constant pressure chamber, 9 ... Variable pressure chamber, 10 ... Valve plunger, 11 ... Input shaft, 12 ... Valve Body, 12a ... atmospheric valve part, 12b ... vacuum valve part, 13 ... vacuum valve seat, 14 ... atmospheric valve seat, 15 ... vacuum valve, 16 ... atmospheric valve, 17 ... control valve, 18 ... valve spring, 19 ... atmospheric introduction 20 ... Vacuum passage, 21 ... Key member (vacuum valve opening means), 22 ... Spacing member, 23 ... Reaction disk, 24 ... Output shaft, 25 ... Return spring, 26 ... Negative pressure introduction passage, 27 ... Vacuum valve seat 27d ... leg (vacuum valve opening means) 28 ... sealing member 29 ... cylindrical member 30 ... holder 31 ... spring

Claims (5)

  A valve body arranged to be movable forward and backward with respect to the inside of the shell, and provided in the valve body, the inside of the shell is partitioned into a constant pressure chamber into which negative pressure is introduced and a variable pressure chamber into which air is introduced during operation. A power piston, a valve plunger connected to the input shaft and slidably disposed in the valve body, and the operation of the valve plunger controls communication or blocking between the constant pressure chamber and the variable pressure chamber. At least a vacuum valve and an atmospheric valve that controls or communicates between the variable pressure chamber and at least the atmosphere, and the vacuum valve includes a valve body and a vacuum valve seat on which the valve body can be seated and separated, The atmospheric valve includes the valve body and an atmospheric valve seat on which the valve body can be seated / separated, and a valve seat member provided with the vacuum valve seat is located in the valve body in an output region of a predetermined output or less. The first position and the predetermined output In the negative pressure booster device, the movement of the valve seat member is controlled by the pressure of the variable pressure chamber, and the valve seat member is provided so as to be movable between a second position located in a larger output region. A negative pressure booster comprising vacuum valve opening means for opening the vacuum valve when moved to a predetermined position.   The negative pressure booster according to claim 1, wherein the movement of the valve seat member is controlled by a pressure difference between the pressure in the variable pressure chamber and the pressure in the constant pressure chamber.   3. The negative pressure multiplier according to claim 1, wherein the vacuum valve opening means includes a shell hooking portion that is hooked on the shell when the valve seat member moves to the predetermined position. Force device. The negative pressure booster according to claim 3, wherein the vacuum valve opening means includes a leg portion of the valve seat member. The vacuum valve opening means includes a leg portion of the valve seat member, the shell hooking portion hooked to the shell at one end, and a leg hooked to the leg portion of the valve seat member on the other side. The negative pressure booster according to claim 3, comprising a key member having a portion latching portion.

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