KR19990067571A - Reciprocating Pump - Google Patents

Abstract

In particular, the reciprocating pump for pumping hydraulic oil for a vehicle brake device includes a differential piston that can be moved axially in the pump chamber 11. In order to reduce manufacturing costs, the differential piston 12 is a cylinder having a constant outer diameter ( 14) and a bush 16 fixed to prevent movement in the axial direction over the cylinder. The bush is usually fitted over the cylinder 14. Elastomer packing fitted over the cylinder portion 141 bounded by the bush 16 seals the cylinder 14 against the wall 111 of the pump chamber 11 and the pump chamber 11 in two different volumes. Divided into two pump chambers (21, 22).

Description

Reciprocating pump

In this type of conventional reciprocating pump (DE 44 07 978 A1), a one-part differential piston is made of rotatable parts, and there are several snap ring grooves in the rotating parts to implement the pump chamber and accept the packing. Plays a role. Such pump plungers are very expensive because of the high processing costs. The differential piston has a larger diameter and a smaller diameter. To ensure the difference between these two diameters, a large amount of fabrication material has to be removed from the differential piston, which entails enormous machining costs. This differential piston is arranged so that even a small diameter part can move axially. Due to this arrangement, the small diameter part of the differential piston must also have good shape and surface finish characteristics. Since the diameter of the differential piston is reduced in this arrangement, machining costs are inevitably increased to meet the requirements for form and surface finish.

Likewise for this type of reciprocating pump (FR 1 218 349 A1), the differential piston is divided into two parts. This differential piston consists of a piston cylinder and a piston rod, of which the piston cylinder is guided to the larger diameter hole portion in the stepped hole, and each one pump chamber by the fronts of the piston cylinders facing each other. Sets the boundary of the. The piston rod, which is guided to the smaller diameter bore part, passes through one of the pump chambers, and the collar at the end face is contoured to fit the recess recessed in front of the piston cylinder. This two-part differential piston is also expensive to manufacture. This is because both the piston cylinder and the piston rod require their respective guide devices for axial movement. The separate guide of the piston cylinder and the piston rod means that the entire minimum length of the device must be extended by extending the minimum guide length required.

The invention relates to a reciprocating pump for delivering hydraulic oil, in particular for a brake device for a vehicle, according to the type defined in the characterizing part of claim 1.

The invention is explained in more detail in the following description through the embodiments drawn in the drawings.

1 is a longitudinal sectional view of a reciprocating pump for a vehicle brake device,

FIG. 2 is an enlarged view of part II of FIG. 1 in a modified reciprocating pump,

3A and 3B are longitudinal cross-sectional views of a cylinder bush inserted into a cylinder to represent the differential piston of the reciprocating pump of FIG. 2 in accordance with second embodiments.

A reciprocating pump for sending hydraulic oil, which is drawn in the longitudinal section in FIG. 1, is a pump for installing in a vehicle brake device, in particular, and is used when adjusting the pressure in a wheel brake cylinder. In such a brake device, abbreviations ABS to ASR to FDR to EHB are used depending on the type of brake device. The pump serves to recycle the brake fluid from the one or several wheel brake cylinders (ABS) in the brake system to the main brake cylinder (ABS), and / or to deliver the brake fluid from the reservoir to the one or several wheel brake cylinders. Role (ASR to FDR to EHB). Pumps are especially needed in brake devices (ABS to ASR) equipped with wheel slip adjusters and / or brake devices (FDR) and / or electro-hydraulic pressure brake devices (EHB) which serve as steering boosters. When the wheel slip adjusters ABS to ARS, for example, apply strong pressure to the brake pedal, the wheels of the vehicle do not move during braking (ABS), and when the accelerator pedal is subjected to strong pressure It is possible to prevent the driving wheel from slipping (ASR). Brake devices that act as steering boosters (FDRs) increase the brake pressure in one or several wheel brake cylinders regardless of the operation of the brake pedal or accelerator pedal, for example, to prevent the vehicle from leaving the track instructed by the driver. can do. The pump can also be used for an electro-hydraulic pressure brake device (EHB). Here, the pump serves to deliver the braking fluid to one or several wheel brake cylinders or to fill the storage container of the brake device when the brake pedal sensor that is electrically operated detects the operation of the brake pedal.

The reciprocating pump has a pump body 10 containing a cylindrical pump chamber 11. Inside the pump chamber 11, the differential piston 12 is guided so as to move in the axial direction, and the differential piston 12 is not shown in the drawing but is the front face 121 of the differential piston 12, which is on the right side in FIG. 1. Is driven to reciprocate up and down against the restoring force of the pump spring 13. As described in DE 44 07 978 A1, a drive mechanism may use a circulating eccentric in which the front face 121 of the differential piston 12 is in close contact with the outer diameter by the pump spring 13.

To reduce manufacturing costs, the differential piston 12 consists of a cylinder 14 and a support ring or bush 16 fixed above the cylinder 14. The cylinder 14 is slightly twisted at the left side in FIG. As a result, a cylinder portion 141 having a small diameter and a cylinder portion 142 having a large diameter are formed, and a shoulder 15 extending radially is formed at the connecting portion. Since the diameter of the small diameter cylinder portion 141 is only slightly smaller than the diameter of the large diameter cylinder portion 142, the shoulder 15 is fixed to the cylinder 14 without almost removing or modifying the fabrication material. The bush 16 is fitted to the cylinder portion 141 having a small diameter and is supported by the shoulder 15. Elastomeric packing 17, likewise fitted over cylinder portion 141, seals differential piston 12 against cylinder wall 111 of pump chamber 11. Between the bush 16 and the elastomer packing 17 a sliding ring 18 made of polytetrafluoroethylene (PTFE) is arranged. The sliding ring 18 is also lightly pushed into the small cylinder portion 141. The sliding ring 18 serves as the first guiding device 32a of the differential piston 12 at the portion of the front face 122 inside the cylinder wall 111 of the pump body 10.

The cylinder wall 111 of the pump body 10 is stepped and has a diameter at one front 121 portion of the differential piston 12 smaller than the diameter at another front 122 portion of the differential piston 12. . The result is a second guide device 32b for guiding the differential piston 12 on the front face 121 part. In the front portion 122, the differential piston 12 is guided to reach the outer diameter of the sliding ring 18. As a result, the working surface of the differential piston 12 becomes stepped, and in particular, when the temperature is low, the advantages resulting from manufacturing the stepped differential piston 12 are exhibited. In order to seal between the pump body 10 and the pump cylinder 14, a nipple may be installed in the circulating key groove although not shown in the second guide device 32b of the pump body 10. Since the bush 16 is installed after processing the surface of the cylinder 14, the cylinder 14 has the largest diameter in the portion of the second guide device 32b. For this reason, the guide apparatus 32b part of the cylinder 14 becomes excellent in a dimension, a form, and a surface treatment surface, without costing a manufacturing cost, As a result, the guide apparatus 32b becomes excellent and the guide apparatus 32b The lifespan of the packing installed in the) part is also long.

The pump spring 13, which is made in the form of a coil compression spring, is supported by a pedestal 20 inserted into the pump chamber 11 on the one hand and on the other hand the differential piston 12 to the cylinder. It is supported by a spring plate 19 abutting the left front 122 of 14. The spring plate 19 is provided at an axial interval from the elastomer packing 17 so that the elastomeric packing 17 is not subjected to an initial stress in the axial direction.

The differential piston 12 divides the pump chamber 11 into two pump chambers 21 and 22 separated from each other. The pump chamber 21 is connected to the pump inlet by the suction passage 23, and the pump chamber 22 is connected to the pump outlet by the pressure passage 24. The pump chamber 21 will be referred to as a low pressure chamber 21, and the pump chamber 22 will be referred to as a high pressure chamber 22. The differential piston 12 has, on the one hand, a pocket hole 25 passing from the front face 122 to the center, and on the other hand, several radial holes 26 traversing this pocket hole 25. These radial holes 26 lead to pocket holes 25. The pocket chamber 25 and the radial hole 26 connect the pump chamber 21 and the pump chamber 22, which can be closed using the first check valve 27. have. In order to implement the check valve 27 a valve seat 28 is placed on the front face 122 of the differential piston 12 which surrounds the pocket hole 25, the valve body 29 being connected to the valve closing spring 30. Is pressed onto the valve seat 28. In this case, the valve closing spring 30, which is similarly manufactured in the form of a coil compression spring, is fixed to the spring plate 19 of the pump spring 13 by the valve body 29 on the one hand and on the other hand. supported by a holder (31). The valve closing spring 30 is much weaker than the pump spring 13.

For a more detailed description, a second check valve 27 ′, which is only symbolically drawn in the figure, is placed between the high pressure chamber 22 and the pressure passage 24. The first check valve 27 functions as a suction valve, and the second check valve 27 'functions as a delivery valve.

In the position of the differential piston 12 shown in FIG. 1, the differential piston 12 has reached the final position of the head. In FIG. 1 the differential piston 12 has moved to this left in this position, with the hydraulic fluid being pumped from the pump chamber 22 to the pump outlet via a second check valve 27 'and a pressure path 24. When the differential piston 12 is subjected to the reverse movement under the influence of the pump spring 13 (to the right in FIG. 1), the check valve 27 is opened, and the hydraulic oil opens the holes 25 and 26 in the pump chamber 21. And flows into the pump chamber 22. In FIG. 1, when the differential piston 12 moves to the left again, the hydraulic oil is pumped from the pump chamber 22 to the pump outlet through the pressure passage 24 when the check valve 27 is closed. At this time, due to the difference between the diameters of the two guide devices 32a and 32b, the working oil flows into the pump chamber 21 through the suction passage 23 at the same time.

The combination of the pump chamber 21 and the pump chamber 22 described by way of example may be achieved in other ways. For example, this coupling may be allowed to penetrate the pump body 10. It is also possible, for example, by edge control to replace a check valve 27 which blocks the flow in the opposite direction while allowing the hydraulic fluid to flow from the pump chamber 21 to the pump chamber 22.

In order to drive-fit the bush 16 to the small diameter cylinder portion 141 of the cylinder 14, the contour must fit precisely. To this end, in the embodiment illustrated in FIG. 1, the dimensions, shape, and surface finish of the small diameter cylinder part 141 should be sufficiently excellent. The dimension, shape and surface finish of the reduced diameter part of the cylindrical body should be excellent, meaning that the processing cost is increased compared to the case where only the largest diameter part of the cylindrical body has the same level of characteristics. do.

In order to slide into the differential piston 12 without damaging the bush 6, in the modified embodiment depicted in FIG. 1, the tapered portion is connected to the connection of the left front 122 and the small diameter cylinder portion 141. chamfer). Placing the tapered portion is particularly advantageous when mass-producing pumps at a low cost.

In the modified embodiment of the reciprocating pump shown in sectional view in FIG. 2 to eliminate such difficulties in manufacturing and to reduce the manufacturing cost of the cylinder 14, the inner hole which is stepped in the bush 16 'when viewed in the axial direction. Puts. In this case, the large diameter cylinder part 142 can be penetrated and cut, and the tolerance of the outer diameter of the larger diameter cylinder part 142 becomes extremely accurate, so that the bush 16 'can be easily and reliably beaten. . Since the large-diameter cylinder portion 142 can be fed through and cut, it is possible to improve the dimensions, shape and surface finish characteristics of the portion in a relatively simple manner. However, improving these characteristics in the small diameter cylinder portion 141 will be costly. Since the reciprocating pump shown in cross-section in FIG. 2 is identical to the reciprocating pump drawn and described in FIG. 1, the same parts are given the same reference numerals, and the description of FIG. 1 with respect to the same parts also applies to FIG. 2.

In order to clarify the shape of the bush 16 ', the longitudinal section of the bush 16' is again shown in FIG. 3A. 3B is a slightly modified bush 16 '. In two variants shown in FIGS. 3A and 3B, the inner diameter of the bush 16 ′ is fabricated in a stepped fashion. The bush 16 'has a smaller bush portion 163' and a larger bush portion 165 ', a shoulder 164' at the portion where these two bush portions 163 ', 165' are connected, There is a taper portion 166 'and an outer diameter 167'.

The diameter of the small diameter bush portion 163 'is such that the cylinder 14 is easily and without resistance until the large bush portion 165' reaches the larger diameter cylinder portion 142. It is adjusted to have a relatively large clearance with the smaller cylinder portion 141 so as to fit in the. When viewed from the axial direction, the bush portion 163 'with a small diameter can be made very short. The inclination of the shoulders 164 'leading to the conical shape and the inclination of the shoulders 15 of the cylinder 14, which are made conical, are adjusted to each other so as not to be damaged even if there is an angle difference. Since the shoulder 164 'is inclined conically, the bush 16' is very easily fitted into the cylinder 14 via the edge at the connection between the left front 122 and the smaller diameter cylinder portion 141. To this end, it is not necessary to have a taper on this edge of the cylinder 14.

The diameter of the large diameter bush portion 165 'is such that the bush 16' is fully inserted into the cylinder 14 and then the large diameter bush portion 165 'is fitted to the large diameter cylinder portion 142. To be fixed, the diameter is adjusted with the diameter of the large cylinder portion 142. Since the large diameter cylinder portion 142 and the large diameter bush portion 165 'can be easily manufactured with high accuracy, the bush 16' can be precisely directed to the cylinder 14 without high cost. .

The outer diameter 167 ′ of the bush 16 ′ is as small as possible with the diameter of the cylinder wall 111 so that the sliding ring 18 enters the gap between the cylinder wall 111 and the outer diameter 167 ′. Not to be adjusted with the diameter of the cylinder wall 111. On the other hand, the size of this gap must be large enough so that the bush 16 'does not rub against the cylinder wall 111. Since the bush 16 'is supported on the cylinder 14 with high accuracy, the clearance between the outer diameter 167' and the cylinder wall 111 can be made very small.

A tapered portion 166 'is placed at the front end of the large diameter bush portion 165' so that the large diameter bush portion 165 'can be easily fitted into the large diameter cylinder portion 142.

Using the same shaped tool, the internal diameter of the bush 16 ', which includes the bush portions 163' and 165 ', the shoulder 164' and the tapered portion 166 ', is highly accurate at low cost. It can be manufactured in a single process. Because of the guiding device 32b, the cylinder portion 142 having a large diameter must be manufactured with high accuracy. In the case of the embodiment depicted in FIG. 2, the bush 16 ′ is placed radially over the cylinder portion 142 fabricated with high accuracy due to the guiding device 32b, thereby securing the cylinder 16 ′ in the radial direction. It is not necessary to process separately in (14).

Modified embodiments of the bush 16 'depicted in FIGS. 3A and 3B have holes 168' on the side facing away from the sliding ring 18 at the outer diameter 167 'for the embodiment depicted in FIG. 3A. The point is different. Between the sliding ring 16 'and the guide device 32b' (FIG. 1), various devices not shown in the figure may be placed, for example filter sieves. Having holes 168 'to provide space for these devices can shorten the overall length.

Bushes 16-16 'are fixed to the cylinder 14 of the differential piston 12. When viewed in the radial direction, the bushes 16, 16 ′ are fixed to the small diameter cylinder portion 141 (FIG. 1) to the large diameter cylinder portion 142 (FIG. 2). When viewed from the axial direction, the bushes 16 and 16 'are fixed to the shoulder 15 facing the high pressure chamber 22 side. If the differential piston 12 moves the hydraulic fluid toward the pressure passage 24 during the original heading rather than recirculation, the pressure in the high pressure chamber 22 becomes much higher than the pressure in the low pressure chamber 21. The difference between these two pressures causes the bushes 16, 16 ′ to strike the shoulder 15. While the original head is made, the pressure in the high pressure chamber 22 is high, while the pressure in the low pressure chamber 21 can be zero. The force acting on the bushes 16, 16 ′ can be easily captured through the shoulder 15 from the cylinder 14 toward the high pressure chamber 22. At this time, it does not matter whether the shoulder 15 extends in the radial direction (FIG. 1) or is inclined in a conical shape (FIG. 2).

A packing 17, usually made of elastomer, seals the high pressure chamber 22 against the low pressure chamber 21. The packing 17 is axially supported by bushes 16 and 16 '. The packing 17 runs all over the height of the double annulus between the cylinder wall 111 and the smaller diameter cylinder portion 141. As a result, the packing 17 causes the hydraulic oil to fill the gap between the outer diameter of the bushes 16, 16 ′ and the cylinder wall 111 and the inner diameter of the bushes 16, 16 ′ and the cylinder 14 from the high pressure chamber 22. Do not reach the low pressure chamber (21). The outer and inner diameters of the bushes 16 and 16 'may be sealed in separate packings, respectively. However, this requires several packings. The embodiment drawn in the drawing has the advantage that it is possible to seal the high pressure chamber 22 with respect to the low pressure chamber 21 with one packing 17.

The reciprocating pump with the features described in claim 1 by the present invention makes it possible to make differential pistons very inexpensively, which is much more expensive than a differential piston consisting of a single part rotating part or two parts of a piston rod and a piston cylinder. It has the advantage of being saved. In the case of the reciprocating pump according to the present invention, since the pump plunger is made in a stepped shape, the pump drainage is much higher than that of the conventional differential piston even at a low temperature. Will help.

The measures described in the other claims may advantageously apply and improve the reciprocating pump described in claim 1.

Claims (14)

The pump chamber includes a differential piston that can move axially, and the differential piston divides the pump chamber into a low pressure chamber 21 and a high pressure chamber 22 having different capacities, and in particular, delivers hydraulic oil in a vehicle brake facility. In the reciprocating pump, The differential piston 12 is fixed to the cylinder 14 and the cylinder 14 with the shoulder 15 facing toward the high pressure chamber 22 and hits the shoulder 15 by the pressure inside the high pressure chamber 22. A reciprocating pump comprising a bush (16, 16 '). The reciprocating pump according to claim 1, characterized in that the bush (16, 16 ') supports a packing (17) which seals the high pressure chamber (22) against the low pressure chamber (21). The reciprocating pump according to claim 1 or 2, characterized in that the bush (16, 16 ') supports a sliding ring (18) for guiding the differential piston (12) in the pump chamber (11). A reciprocating pump as claimed in any one of claims 1 to 3, characterized in that the bush (16; 16 ') is fitted to the cylinder (14) by a spring. 5. The bush (16) according to claim 1, wherein the bush (16; 16 ′) is in contact with the shoulder (15) which circulates around the cylinder (14) in front of the elastomer packing (17). Reciprocating pump characterized in that. 6. The sliding ring 18 according to claim 3, wherein the sliding ring 18 is arranged between the bush 16 and the elastomer packing 17 and is made of plastic, in particular polytetrafluoroethylene (PTFE). Reciprocating pump. 7. A pull-back spring of a piston, made in the form of a coil compression spring, on the one hand to the pedestal 20 in the pump chamber, on the other hand to the differential piston. A reciprocating pump characterized by being supported by (12). 8. A reciprocating pump as claimed in any one of the preceding claims, comprising a coupling between two pump chambers (21, 22) which can be closed by a control mechanism. 9. The method according to claim 8, characterized in that the coupling between the two pump chambers (21, 22) is made in the form of the holes (25, 26) in the differential piston (12) and the control mechanism is in the form of a check valve (27). Reciprocating pump. 10. The cylinder portion 141 of the cylinder 14, bounded by bushes 16; 16 ', has a reduced outer diameter relative to the diameter of the cylinder, 15. A reciprocating pump, characterized in that it forms a connecting portion connecting the smaller diameter cylinder portion (141) and the larger diameter cylinder portion (142). 12. The method according to claim 10, wherein the bush (16) is placed in the smaller diameter cylinder portion (141), and the spring is connected between the inner surface of the bush (16) and the outer surface of the smaller diameter cylinder portion (141). Reciprocating pump characterized in that. 11. The bush 16 'according to claim 10 has a stepped inner diameter of the bush 16', thereby forming a bush portion 163 'having a small inner diameter and a bush portion 165' having a large inner diameter, and having a small inner diameter. The portion 163 ′ has a relatively wide gap with respect to the small diameter cylinder portion 141, and has an annular inner surface of the bush portion 165 ′ with a large inner diameter and an outer surface of the large cylinder portion 142 with a large diameter. Reciprocating pump, characterized in that the connection between the spring. 13. The reciprocating pump according to claim 12, wherein a shoulder (164 ') formed between two bush portions (163', 165 ') is inclined in a conical shape so that the bush (16') can be easily assembled. 14. Reciprocating pump according to claim 12 or 13, characterized in that the large diameter cylinder portion (142) is centerless grinding so that the diameter is accurate.