Anti-lock brake upper pump assembly

Abstract

The utility model provides an anti-lock brake upper pump assembly. The anti-lock brake upper pump assembly comprises a pump support, an oil cup, a lining, a push rod, a pressure relief hole and the like. When the push rod moves, the auxiliary oil supply hole and the pressure relief hole are communicated or blocked, the multi-time snub effect is achieved, and wheel locking is avoided. By arranging the communicating oil supply hole, the circulating communicating hole, the pressure retaining valve rod and other structures, the oil flowing path is optimized, the braking response speed is increased, and the oil utilization rate is increased. Meanwhile, the design of a first limiting gasket, a reset spring, teeth and the like is adopted, and the stability and reliability of the braking system are enhanced. The assembly is compact in structure, good in braking effect and suitable for various vehicle braking systems.

Description

TECHNICAL FIELD

[0001] The utility model relates specifically to prevent the assembly of brake upper pump. BACKGROUND

[0002] The motorcycle handle is equipped with brake upper pump, which generates pressure through hydraulic system, pushes brake oil flow, and then makes brake pad contact with wheel hub or brake disc, so as to realize the purpose of deceleration or parking. The upper pump is usually composed of handle and an internal piston, when the rider presses the brake handle, the piston pushes brake oil downward, and the pressure is gradually transmitted to brake line, so that brake pad is tightly attached to wheel hub, and the rotation of wheel hub is inhibited.

[0003] The Chinese invention patent application file with the publication number "CN103213571A" discloses a buffer type brake push rod structure of vehicle, which is mainly composed of brake master pump and brake push rod two modules, wherein the brake push rod is composed of push rod cylinder, brake push rod, brake push rod piston, three groups of springs and at least three groups of O-rings (equivalent to sealing ring). The brake push rod is designed as the structure of oil cylinder, and the inside of the brake push rod is provided with first to fourth stage chambers. The first stage chamber accommodates the first spring to provide elastic buffer. The second stage chamber accommodates the brake push rod piston, the end surface of which is adjacent to the first spring, and the oil passage is arranged in the axial direction to allow brake oil to enter. The third stage chamber accommodates the oil valve rod, the end surface of which is adjacent to the brake push rod piston, and the oil valve rod is provided with a flange, and the second spring is arranged between the flange and the brake push rod piston. The fourth stage chamber accommodates the bushing, which is sleeved on the outer edge of the oil valve rod, and the inner edge and the outer edge are respectively provided with first ring groove and second ring groove, and the first O-ring and the second O-ring are embedded to prevent brake oil leakage. When the brake pedal is stepped on, the brake push rod works as an oil cylinder, brake oil is allowed to enter through the oil passage, the oil valve rod generates impedance to brake oil path, and after overcoming the impedance, the brake master pump is pushed to realize the brake function.

[0004] However, the buffer type brake push rod structure has the following technical problems:

[0005] Firstly, when the brake push rod is pushed inward, the oil pressure between the brake master pump and the brake push rod will gradually increase, and once the oil pressure increases to the critical point, the brake push rod cannot move forward. Since the brake push rod is designed as an oil cylinder, and it contains multi-stage chambers and spring structure inside, at this time, the oil will gradually push the first spring, the brake push rod piston, the second spring, the oil valve rod, the bushing and the third spring (according to the attached drawings of the disclosure file) in the brake push rod, so as to increase the cavity between the brake master pump and the brake push rod, and reduce the oil pressure, which is the pressure maintaining function, and only plays a buffering role, so the process of single stepping for braking cannot be point braking. Figure 3

[0006] ​Secondly, the brake push rod pressure maintaining function is also limited, that is, when the first spring, brake push rod piston, second spring, oil valve rod, bushing and third spring move to the situation of being unable to move, there is still a great probability of wheel lock phenomenon, and the safety is poor. Technical problems to be solved by the utility model

[0007] The utility model wants to solve the technical problem in view to the insufficient of prior art, provides anti -lock braking pump assembly, realizes multiple point brake effect through setting up several groups of pressure release hole and auxiliary oil supply hole, avoids wheel lock, promotes the overall safety of vehicle.

[0008] To achieve the above object, the utility model provides the following technical scheme.

[0009] The anti -lock braking pump assembly, including pump support and the oil cup installed above pump support, be equipped with main oil cavity in the pump support, the lateral wall of main oil cavity is equipped with the main oil supply hole that can link up the oil cup with main oil cavity, its characterized in that: be equipped with the bushing of fixed connection with pump support in main oil cavity, the bushing is equipped with the piston cavity of being set along the axial direction and being penetrated in, be equipped with push rod in the piston cavity, the inner end portion of push rod is equipped with the oil return cavity, the lateral wall of push rod is penetrated and is equipped with the auxiliary oil supply hole that links up with oil return cavity, the lateral wall of bushing is penetrated and is equipped with several groups of pressure release hole that are arranged along the axial direction and are spaced apart in sequence, the both ends of bushing and pump support are sealedly connected, and the middle part and pump support are clearance fit;When push rod moves along the axial direction in piston cavity reciprocating, make auxiliary oil supply hole reciprocating along the center point line of several groups of pressure release hole, and then make auxiliary oil supply hole and pressure release hole conduct or block.

[0010] (I) In the technical solution, when the push rod is in an inactive state, the auxiliary oil supply hole is in communication with the set of pressure relief holes at the end, and the oil in the oil cup flows into the oil return cavity through the main oil supply hole, the pressure relief hole at the end, and the auxiliary oil supply hole in sequence, and fills the main oil cavity. During braking, the push rod moves inward, and the oil pressure in the main oil cavity gradually increases. When the push rod moves to the position where the auxiliary oil supply hole is in communication with a set of pressure relief holes, the excessive oil pressure in the main oil cavity and the oil return cavity will squeeze the oil to flow back to the oil cup through the auxiliary oil supply hole, the pressure relief hole, and the main oil supply hole, thereby achieving the effect of point braking. During this period, since the bushing and the pump support are in clearance fit, any set of pressure relief holes is always in communication with the main oil supply hole, but the two ends of the bushing are sealed, and the auxiliary oil supply hole is in communication with the set of pressure relief holes only when it moves to the corresponding position, thereby achieving the effect of point braking. By arranging a plurality of sets of pressure relief holes, the effect of multiple point braking is achieved.

[0011] The anti-lock braking upper pump assembly described above can be further provided with a communication oil supply hole penetrating through the side wall of the bushing corresponding to the main oil supply hole, one end of the communication oil supply hole being in communication with the main oil supply hole, and the inner diameter of the communication oil supply hole being larger than the inner diameter of the pressure relief hole.

[0012] In the technical solution, when the push rod is in an inactive state, the auxiliary oil supply hole is in communication with the communication oil supply hole (this solution does not use the pressure relief hole at the end as an oil inlet channel), and the oil in the oil cup flows into the oil return cavity through the main oil supply hole, the communication oil supply hole, and the auxiliary oil supply hole in sequence, and fills the main oil cavity. The inner diameter of the communication oil supply hole is larger, and the oil inlet amount is larger, which can ensure that the main oil cavity is filled with oil, shorten the braking response time, reduce the vehicle speed faster, and improve the driving safety. Since the oil flows more smoothly, the wear and heat accumulation of the components caused by poor oil flow are reduced. This helps to prolong the service life of the braking system and reduce the decline in braking performance caused by overheating.

[0013] The anti-lock braking upper pump assembly described above can be further provided with a communication oil supply hole penetrating through the side wall of the bushing corresponding to the main oil supply hole, one end of the communication oil supply hole being in communication with the main oil supply hole, and the inner diameter of the communication oil supply hole being larger than the inner diameter of the pressure relief hole.

[0014] The push rod and the bushing are in clearance fit, and the oil in the oil cup flows into the clearance between the push rod and the bushing through the main oil supply hole, the clearance between the bushing and the pump support, the circulation communication hole or the pressure relief hole. Due to the position distribution of the first sealing ring, the second sealing ring and the two groups of third sealing rings, the oil cannot flow into the main oil chamber and the oil return chamber at will. During the reciprocating movement of the push rod, the oil in the main oil chamber and the oil return chamber can only flow back to the oil cup or flow from the oil cup to the main oil chamber and the oil return chamber when the auxiliary oil supply hole is in communication with the communication oil supply hole or the pressure relief hole. At the same time, the circulation communication hole is arranged to enable the oil to circulate in the clearance between the bushing and the pump support and the clearance between the push rod and the bushing, which not only helps to balance the oil pressure of each part, but also enables the excess oil to be discharged or supplemented to the required position in time during the reciprocating movement of the push rod, thereby improving the utilization rate of the oil and the response speed of the braking system.

[0015] The anti-lock braking pump assembly can be further provided with a pressure maintaining valve rod in the oil return chamber, one end of the pressure maintaining valve rod being linked with a pressure maintaining spring, the end of the pressure maintaining spring away from the pressure maintaining valve rod being in abutting connection with the inner end of the oil return chamber, the inner wall of the oil return chamber being provided with a limiting stop ring protruding towards the center line of the oil return chamber, the end of the pressure maintaining valve rod away from the pressure maintaining spring being connected with a pressure maintaining rubber ring in the outer periphery, the outer diameter of the pressure maintaining rubber ring being greater than the inner diameter of the limiting stop ring and the outer diameter of the pressure maintaining rubber ring being smaller than the inner diameter of the oil return chamber, and the auxiliary oil supply hole being distributed on the inner end side wall of the oil return chamber.

[0016] During braking, the push rod moves inward, the oil pressure in the main oil chamber gradually increases, the oil in the main oil chamber presses the pressure maintaining valve rod, the pressure maintaining valve rod presses the pressure maintaining spring, and as long as the pressure maintaining rubber ring does not abut against the limiting stop ring, the oil can still flow along the main oil chamber, the oil return chamber and the auxiliary oil supply hole. Whenever the push rod moves to the point where the auxiliary oil supply hole is in communication with one group of pressure relief holes, the excessive oil pressure in the main oil chamber and the oil return chamber will press the oil to flow back to the oil cup through the auxiliary oil supply hole, the pressure relief hole and the main oil supply hole, thereby achieving the function of point braking. When the oil pressure increases to the point where the pressure maintaining valve rod moves to the point where the pressure maintaining rubber ring abuts against the limiting stop ring, the oil does not flow back. Continue to push the push rod, the pressure maintaining rubber ring will pass through the limiting stop ring under a larger pressure, and at this time the oil can keep flowing. When the braking is stopped, the pressure maintaining spring pushes the pressure maintaining valve rod to reset, and the pressure maintaining rubber ring also passes through the limiting stop ring to return to the initial position following the pressure maintaining valve rod. As can be seen from the above, by designing the pressure maintaining valve rod, the limiting stop ring and the pressure maintaining rubber ring, the necessary oil pressure is maintained while preventing the wheels from being locked due to excessive oil pressure, thereby enhancing the pressure maintaining function of the braking system. The purpose of the outer diameter of the pressure maintaining rubber ring being greater than the inner diameter of the limiting stop ring and the outer diameter of the pressure maintaining rubber ring being smaller than the inner diameter of the oil return chamber is that as long as the pressure maintaining rubber ring does not abut against the limiting stop ring, the oil can flow.

[0017] The anti-lock braking upper pump assembly can be further provided with a first installation ring groove at the opening end of the oil return cavity, and a first limiting washer is fixed in the first installation ring groove.

[0018] When the braking is stopped and the pressure maintaining spring pushes the pressure maintaining valve rod to reset, the limiting block on the first limiting washer limits the pressure maintaining valve rod to avoid excessive resetting, and ensures that the pressure maintaining function is stably realized.

[0019] The anti-lock braking upper pump assembly can be further provided with a reset spring in the main oil cavity, one end of the reset spring is in abutting connection with the pump support, a limiting step is arranged at the outer periphery of the inner end of the push rod, and the other end of the reset spring is in abutting connection with the limiting step.

[0020] When the braking is stopped, the reset spring can help the push rod to reset faster, accelerate the braking speed, and improve the safety performance.

[0021] The anti-lock braking upper pump assembly can be further provided with a gear at the end of the bushing away from the main oil cavity, the gear is arranged to be inclined towards the side away from the main oil cavity, a second installation ring groove is arranged on the pump support corresponding to the end of the bushing, a second limiting washer is fixed in the second installation ring groove, and the inner diameter of the second limiting washer is smaller than the outer diameter of the bushing.

[0022] By adopting the above technical scheme, the gear is arranged to be inclined, so that the bushing is prevented from moving when the push rod resets, and the connection reliability of the bushing and the pump support is improved. The second limiting washer is used for installing and positioning the bushing.

[0023] The utility model will be further explained in detail in connection with the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is an explosion schematic view of the utility model embodiment;

[0025] Figure 2 It is a sectional view of the utility model embodiment;

[0026] Figure 3 It is an explosion schematic view of the push rod and the bushing of the utility model embodiment;

[0027] Figure 4 It is an assembly schematic view of the push rod and the bushing of the utility model embodiment;

[0028] Figure 5 It is a sectional view of the push rod and the bushing after being assembled of the utility model embodiment.

[0029] Label annotations: Pump bracket 1, main oil chamber 1a, main oil supply hole 1b; oil cup 2; bushing 3, piston chamber 3a, pressure relief hole 3b, connecting oil supply hole 3c, circulation connecting hole 3d, tooth 3e; push rod 4, return oil chamber 4a, auxiliary oil supply hole 4b, limit retaining ring 4c, limit step 4d, second limit washer 4f; first sealing ring 5, second sealing ring 6, third sealing ring 7, pressure holding valve stem 8, pressure holding spring 9, pressure holding rubber ring 10, first limit washer 11, stop block 12, return spring 13. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0031] like Figures 1 to 5 The anti-lock braking system (ABS) upper pump assembly shown includes a pump bracket 1 and an oil cup 2 mounted above the pump bracket 1. The pump bracket 1 has a main oil chamber 1a, and the side wall of the main oil chamber 1a has a main oil supply hole 1b that connects the oil cup 2 to the main oil chamber 1a. A bushing 3, fixedly connected to the pump bracket 1, is located within the main oil chamber 1a. An axially oriented piston chamber 3a extends through the bushing 3, and a push rod 4 is located within the piston chamber 3a. The inner end of the push rod 4 has a return oil chamber 4a, and an auxiliary oil supply hole 4b, communicating with the return oil chamber 4a, extends through the side wall of the push rod 4. Four sets of pressure relief holes 3b, arranged axially at intervals, extend through the side wall of the bushing 3. The two ends of the bushing 3 are sealed to the pump bracket 1, while the middle part is clearance-fitted to the pump bracket 1. A connecting oil supply hole 3c extends through the side wall of the bushing 3 corresponding to the main oil supply hole 1b, and one end of the connecting oil supply hole 3c communicates with the main oil supply hole 1b. The inner diameter of the oil supply port 3c is larger than that of the pressure relief port 3b, allowing for a larger oil intake. This ensures that the main oil chamber 1a is filled with oil, shortens the braking response time, and enables the vehicle to decelerate more quickly, thus improving driving safety.

[0032] When push rod 4 is not in operation, auxiliary oil supply port 4b is connected to connecting oil supply port 3c. The oil in oil cup 2 flows sequentially through main oil supply port 1b, connecting oil supply port 3c, and auxiliary oil supply port 4b into return oil chamber 4a, filling the main oil chamber 1a. When push rod 4 moves axially within piston chamber 3a, it causes auxiliary oil supply port 4b to reciprocate along the line connecting the center points of the four sets of pressure relief ports 3b, thereby enabling or blocking auxiliary oil supply port 4b from connecting with pressure relief ports 3b.

[0033] The push rod 4 is in clearance fit with the bushing 3, the outer periphery of the push rod 4 close to the inner end of the piston cavity 3a is connected with the first sealing ring 5, the outer periphery of the push rod 4 close to the outer end of the piston cavity 3a is connected with the second sealing ring 6, two groups of third sealing rings 7 are arranged along the axial direction of the push rod 4 in sequence between the first sealing ring 5 and the second sealing ring 6, the auxiliary oil supply hole 4b is located between the two groups of third sealing rings 7, the side wall of the bushing 3 further penetrates the circulation communication hole 3d, and the circulation communication hole 3d is distributed between the second sealing ring 6 and the third sealing ring 7. The push rod 4 is in clearance fit with the bushing 3, the oil in the oil cup 2 flows into the clearance between the push rod 4 and the bushing 3 along the main oil supply hole 1b, the clearance between the bushing 3 and the pump support 1, the circulation communication hole 3d or the pressure relief hole 3b. Due to the position distribution of the first sealing ring 5, the second sealing ring 6 and the two groups of third sealing rings 7, the oil will not enter the main oil cavity 1a and the oil return cavity 4a at will. During the reciprocating movement of the push rod 4, only when the auxiliary oil supply hole 4b is communicated with the communication oil supply hole 3c or the pressure relief hole 3b, the oil in the main oil cavity 1a and the oil return cavity 4a will flow back to the oil cup 2, or flow from the oil cup 2 to the main oil cavity 1a and the oil return cavity 4a. At the same time, the setting of the circulation communication hole 3d enables the oil to circulate in the clearance between the bushing 3 and the pump support 1 and the clearance between the push rod 4 and the bushing 3, which not only helps to balance the oil pressure of each part, but also timely discharges or supplements the excess oil to the required position during the reciprocating movement of the push rod 4, thereby improving the utilization rate of the oil and the response speed of the brake system.

[0034] The oil return cavity 4a is provided with a pressure maintaining valve rod 8, one end of the pressure maintaining valve rod 8 is linked with a pressure maintaining spring 9, the end of the pressure maintaining spring 9 away from the pressure maintaining valve rod 8 is in abutting connection with the inner end of the oil return cavity 4a, the inner wall of the oil return cavity 4a is provided with a limiting block ring 4c protruding towards the center line of the oil return cavity 4a, the outer periphery of the end of the pressure maintaining valve rod 8 away from the pressure maintaining spring 9 is connected with a pressure maintaining rubber ring 10, the outer diameter of the pressure maintaining rubber ring 10 is greater than the inner diameter of the limiting block ring 4c and the outer diameter of the pressure maintaining rubber ring 10 is smaller than the inner diameter of the oil return cavity 4a, and the auxiliary oil supply hole 4b is distributed on the inner end side wall of the oil return cavity 4a. The opening end of the oil return cavity 4a is provided with a first installation ring groove, a first limiting washer 11 is fixed in the first installation ring groove, and the inner periphery of the first limiting washer 11 is provided with a plurality of groups of limiting blocks 12 arranged at intervals.

[0035] During braking, the push rod 4 moves inward, the oil pressure in the main oil chamber 1a gradually increases, the oil in the main oil chamber 1a presses the pressure maintaining valve rod 8, the pressure maintaining valve rod 8 presses the pressure maintaining spring 9, and as long as the pressure maintaining rubber ring 10 does not push against the limiting stop ring 4c, the oil can still flow along the main oil chamber 1a, the oil return chamber 4a and the auxiliary oil supply hole 4b. Whenever the push rod 4 moves to the auxiliary oil supply hole 4b and a group of pressure relief holes 3b are in communication, the excessive oil pressure in the main oil chamber 1a and the oil return chamber 4a will press the oil to flow back to the oil cup 2 along the auxiliary oil supply hole 4b, the pressure relief hole 3b and the main oil supply hole 1b, thereby playing a role in point braking. When the oil pressure increases to the point that the pressure maintaining valve rod 8 moves to the point that the pressure maintaining rubber ring 10 pushes against the limiting stop ring 4c, the oil no longer flows back. Continue to push the push rod 4, and the pressure maintaining rubber ring 10 will pass through the limiting stop ring 4c under a larger pressure, at which time the oil can maintain flow. When braking is stopped, the pressure maintaining spring 9 pushes the pressure maintaining valve rod 8 back to its original position, and the pressure maintaining rubber ring 10 also passes through the limiting stop ring 4c to return to its original position along with the pressure maintaining valve rod 8. As can be seen from the above, by designing the pressure maintaining valve rod 8, the limiting stop ring 4c and the pressure maintaining rubber ring 10, the necessary oil pressure is maintained while preventing the wheels from being locked due to excessive oil pressure, thereby enhancing the pressure maintaining function of the braking system. The purpose of the pressure maintaining rubber ring 10 having an outer diameter that is greater than the inner diameter of the limiting stop ring 4c and the pressure maintaining rubber ring 10 having an outer diameter that is less than the inner diameter of the oil return chamber 4a is to allow the oil to flow as long as the pressure maintaining rubber ring 10 does not push against the limiting stop ring 4c. When braking is stopped and the pressure maintaining spring 9 pushes the pressure maintaining valve rod 8 back to its original position, the stop block 12 on the first limiting washer 4c limits the pressure maintaining valve rod 8, thereby preventing excessive resetting and ensuring that the pressure maintaining function is stably achieved.

[0036] The main oil chamber 1a is provided with a reset spring 13, one end of the reset spring 13 is in contact with the pump support 1, the inner end of the push rod 4 is provided with a limiting step 4d, and the other end of the reset spring 13 is in contact with the limiting step 4d. When braking is stopped, the reset spring 13 can help the push rod 4 reset more quickly, thereby increasing the braking speed and improving safety performance.

[0037] The outer periphery of the end of the bushing 3 away from the main oil chamber 1a is provided with a tooth 3e, the tooth 3e is inclined towards the side away from the main oil chamber 1a, the pump support 1 is provided with a second installation ring groove corresponding to the end of the bushing 3, the second installation ring groove is fixed with a second limiting washer 4f, and the inner diameter of the second limiting washer 4f is less than the outer diameter of the bushing 3. The tooth 3e is inclined to avoid moving the bushing 3 when the push rod 4 is reset, thereby improving the connection reliability of the bushing 3 and the pump support 1. The second limiting washer 4f is used for installation and positioning of the bushing 3.

[0038] Working principle of the embodiment:

[0039] When the push rod 4 is not working, the auxiliary oil supply hole 4b is communicated with the communication oil supply hole 3c, and the oil in the oil cup 2 flows into the oil return cavity 4a through the main oil supply hole 1b, the communication oil supply hole 3c and the auxiliary oil supply hole 4b in turn, and fills the main oil cavity 1a.

[0040] During braking, the push rod 4 moves inward, the oil pressure in the main oil cavity 1a gradually increases, the oil in the main oil cavity 1a presses the pressure maintaining valve rod 8, the pressure maintaining valve rod 8 presses the pressure maintaining spring 9, and as long as the pressure maintaining rubber ring 10 does not push against the limiting stop ring 4c, the oil can still flow along the main oil cavity 1a, the oil return cavity 4a and the auxiliary oil supply hole 4b.

[0041] When the push rod 4 moves to the position where the auxiliary oil supply hole 4b is communicated with a group of pressure relief holes 3b, the excessive oil pressure in the main oil cavity 1a and the oil return cavity 4a presses the oil to flow back to the oil cup 2 through the auxiliary oil supply hole 4b, the pressure relief hole 3b and the main oil supply hole 1b, thereby achieving the effect of point braking. During this period, the bushing 3 is in clearance fit with the pump bracket 1, so any group of pressure relief holes 3b is always communicated with the main oil supply hole 1b, but the two ends of the bushing 3 are sealed, and the auxiliary oil supply hole 4b is communicated with the corresponding group of pressure relief holes 3b only when it moves to the position corresponding to the group of pressure relief holes 3b, thereby achieving the effect of point braking. By arranging a plurality of groups of pressure relief holes 3b, the effect of multiple point braking is achieved.

[0042] During the movement of the push rod 4, if the oil pressure increases to the position where the pressure maintaining valve rod 8 moves to the position where the pressure maintaining rubber ring 10 pushes against the limiting stop ring 4c, the oil does not flow back. Continue to push the push rod 4, and the pressure maintaining rubber ring 10 will pass through the limiting stop ring 4c under a large pressure, at which time the oil can keep flowing. When the braking is stopped, the pressure maintaining spring 9 pushes the pressure maintaining valve rod 8 to reset, and the pressure maintaining rubber ring 10 also passes through the limiting stop ring 4c to return to the initial position with the pressure maintaining valve rod 8.

[0043] As can be seen from the above, the embodiment not only has the pressure maintaining function, but also can achieve multiple point braking, and has high safety performance.

Claims

1. An anti-lock braking system (ABS) upper pump assembly, comprising a pump bracket and an oil cup mounted above the pump bracket, wherein the pump bracket has a main oil chamber, and the side wall of the main oil chamber has a main oil supply port that connects the oil cup to the main oil chamber, characterized in that: The main oil chamber is equipped with a bushing fixedly connected to the pump bracket. A piston chamber arranged axially runs through the bushing. A push rod is provided in the piston chamber. The inner end of the push rod is provided with a return oil chamber. An auxiliary oil supply hole communicating with the return oil chamber runs through the side wall of the push rod. Several sets of pressure relief holes arranged axially at intervals run through the side wall of the bushing. The two ends of the bushing are sealed to the pump bracket, and the middle part is clearance-fitted to the pump bracket. When the push rod moves axially back and forth in the piston chamber, the auxiliary oil supply hole moves back and forth along the line connecting the center points of the several sets of pressure relief holes, thereby making the auxiliary oil supply hole connect with or block the pressure relief hole.

2. The anti-lock braking system upper pump assembly according to claim 1, characterized in that: The sidewall of the bushing has a connecting oil supply hole that runs through it at the location of the main oil supply hole. One end of the connecting oil supply hole is connected to the main oil supply hole, and the inner diameter of the connecting oil supply hole is larger than the inner diameter of the pressure relief hole.

3. The anti-lock braking system upper pump assembly according to claim 2, characterized in that: The push rod and the bushing are clearance-fitted. A first sealing ring is connected to the outer periphery of the push rod near the inner end of the piston chamber, and a second sealing ring is connected to the outer periphery of the push rod near the outer end of the piston chamber. Two sets of third sealing rings are arranged sequentially along the axial direction of the push rod between the first and second sealing rings. The auxiliary oil supply hole is located between the two sets of third sealing rings. A circulation communication hole is also provided through the side wall of the bushing, and the circulation communication hole is distributed between the second and third sealing rings.

4. The anti-lock braking system upper pump assembly according to any one of claims 1 to 3, characterized in that: The return oil chamber is equipped with a pressure-holding valve stem, one end of which is linked to a pressure-holding spring. The end of the pressure-holding spring away from the pressure-holding valve stem is in contact with the inner end of the return oil chamber. The inner wall of the return oil chamber is provided with a limiting retaining ring protruding towards the center line of the return oil chamber. A pressure-holding rubber ring is connected to the outer periphery of the end of the pressure-holding valve stem away from the pressure-holding spring. The outer diameter of the pressure-holding rubber ring is larger than the inner diameter of the limiting retaining ring and smaller than the inner diameter of the return oil chamber. The auxiliary oil supply holes are distributed on the inner end side wall of the return oil chamber.

5. The anti-lock braking system upper pump assembly according to claim 4, characterized in that: The opening end of the oil return chamber is provided with a first mounting ring groove, and a first limiting washer is fixed in the first mounting ring groove. The inner circumference of the first limiting washer is provided with several sets of spaced blocks.

6. The anti-lock braking system upper pump assembly according to claim 5, characterized in that: A return spring is provided in the main oil chamber. One end of the return spring is in contact with the pump bracket. A limiting step is provided on the outer periphery of the inner end of the push rod. The other end of the return spring is in contact with the limiting step.

7. The anti-lock braking system upper pump assembly according to any one of claims 1 to 3, characterized in that: The bushing has teeth on its outer periphery at the end away from the main oil chamber. The teeth are inclined toward the side away from the main oil chamber. The pump bracket has a second mounting ring groove corresponding to the end of the bushing. A second limiting ring is fixed in the second mounting ring groove. The inner diameter of the second limiting ring is smaller than the outer diameter of the bushing.

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