KR100497266B1 - Piston pump - Google Patents

Abstract

In particular, a piston pump for pumping hydraulic fluid for a brake device for a vehicle includes a stepped piston that can move axially in the pump chamber 11. In order to reduce manufacturing costs, the stepped piston 12 has an almost outer diameter. It is composed of a constant solid cylinder 14 and a bush 16 fixed to prevent movement in the axial direction over the solid cylinder. The bush is usually fitted over the solid cylinder 14. An elastomeric seal fitted over the cylinder portion 141 bounded by the bush 16 seals the solid cylinder 14 against the wall 111 of the pump chamber 11, and the pump chamber 11 for variable volume. Divided into two pump chambers (21, 22).

Description

Piston pump

The invention relates to a piston pump for delivering hydraulic fluid, in particular for a brake device for a vehicle, according to the preamble of claim 1.

In the case of this type of conventional piston pump (DE 44 07 978 A1), the stepped piston is made of an integral rotating part, and there are several ring grooves in the rotating part to realize the pump chamber and to receive the seal. . Such pump pistons are very expensive because of the high processing costs. Stepped pistons have a larger diameter and a smaller diameter. To achieve a clear difference between these two diameters, a large amount of material must be removed from the stepped piston, which entails enormous machining costs. This stepped piston is arranged so that even a small diameter part can move axially. Due to this arrangement, even small diameter parts of stepped pistons must have good shape and surface quality. Since the diameter of the stepped piston is reduced in this arrangement, machining costs are inevitably increased to meet the requirements for form and surface quality.

Likewise known piston pumps of this type FR 1 218 349 A1 have stepped pistons formed in two parts. This stepped piston consists of a piston cylinder and a piston rod, of which the piston cylinder is guided to the larger diameter hole part in the stepped hole and faces each other by the fronts of the piston cylinders facing away from each other. Set the boundary. The piston rod, which is guided to the smaller diameter bore part, penetrates one of the pump chambers, and the collar on the end face is contoured to fit the recess formed in the front of the piston cylinder. This two-part staircase 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. In addition, the separate guide of the piston cylinder and the piston rod means that the entire length of the device has to be long due to the minimum guide length required.

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 piston pump for a vehicle brake device,

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

3A and 3B are longitudinal cross-sectional views of a bush fitted into a cylinder to represent the stepped piston of the piston pump of FIG. 2 in accordance with two embodiments.

The piston pump for delivering hydraulic fluid, which is drawn in 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 the 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 brake devices (EHB) serving as steering aides. 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 rotating (ASR). The brake device acting as a steering aid (FDR) increases the brake pressure in one or several wheel brake cylinders independently of the operation of the brake pedal or accelerator pedal, for example to prevent the vehicle from leaving the track desired by the driver. Can be. The pump can also be used for the electro-hydraulic brake system (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 piston pump has a pump body 10 containing a cylindrical pump chamber 11. The stepped piston 12 is guided in the pump chamber 11 so as to be able to move in the axial direction, and the stepped piston 12 is not shown in the drawing, but is shown on the right side in FIG. 1 of the stepped piston 12. The drive member engaged with the front face 121 is driven to reciprocate against the restoring force of the pump spring 13. As described in DE 44 07 978 A1 it is possible to use a cam with an outer circumference in which the front face 121 of the stepped piston 12 is pressed by the pump spring 13 as a drive member.

In order to reduce manufacturing costs, the stepped piston 12 is composed of a solid cylinder 14 and a supporting disk or bush 16 fixed on the solid cylinder 14. The solid 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 formed in the solid cylinder 14 with little or no material removal. The bush 16 is fitted to the cylinder portion 141 having a small diameter and is supported by the shoulder 15. Likewise, an elastomeric seal 17 fitted over the cylinder portion 141 seals the stepped piston 12 against the cylinder wall 111 of the pump chamber 11. Between the bush 16 and the elastomeric seal 17 a sliding ring 18 made of polytetrafluoroethylene (PTFE) is arranged. The sliding ring 18 is also fitted to the small diameter cylinder portion 141 by slight pressure. A sliding ring 18 is provided for the first guide device 32a of the stepped 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 stepped piston 12 that is larger than the diameter of the other front 122 portion of the stepped piston 12. small. As a result, a second guide device 32b for guiding the stepped piston 12 is formed in the front portion 121. In the frontal 122 portion, the stepped piston 12 is guided at the outer diameter of the sliding ring 18. As a result, the action surface of the stepped piston 12 becomes stepped, and the advantages resulting from manufacturing the stepped piston 12 stepped especially when the temperature is low appear. In order to seal between the pump body 10 and the solid cylinder 14, a sealing ring may be installed in the groove not shown in the drawing in the second guide device 32b of the pump body 10. Since the bush 16 is installed after processing the surface of the solid cylinder 14, the solid cylinder 14 has a second diameter of the second guide device 32b. For this reason, the guide apparatus 32b part of the solid cylinder 14 becomes excellent in a dimension, a form, and a surface quality, without making manufacturing cost a lot, As a result, the guide apparatus 32b becomes excellent and the guide apparatus ( The life of the seal attached to the part 32b) becomes long.

The pump spring 13, which is manufactured in the form of a coil compression spring, is supported on one hand by a pedestal 20 inserted into the pump chamber 11, and on the other hand, a stepped piston 12 to solid It is supported by a spring plate 19 in contact with the left front side 122 of the cylinder 14. The spring plate 19 is provided at an axial distance from the elastomeric seal 17 such that no initial stress is applied to the elastomeric seal 17 in the axial direction.

The stepped 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 through the suction pipe 23, and the pump chamber 22 is connected to the pump outlet through the pressure pipe 24. Hereinafter, the pump chamber 21 is called a low pressure chamber 21 and the pump chamber 22 is called a high pressure chamber 22. The stepped piston 12 has a central pocket hole 25 from the front face 122 on the one hand and several radial holes 26 across the pocket hole 25 on the other hand. These radial holes 26 lead to pocket holes 25. The pump chamber 21 and the pump chamber 22 are connected through the pocket hole 25 and the radial hole 26, which connection part can be closed by the first check valve 27. In order to implement the check valve 27, a valve seat 28 is formed on the front face 122 of the stepped piston 12, which surrounds the pocket hole 25, and the valve ball 29 is a valve closing spring 30. Is pressed against the valve seat 28. A valve closing spring 30, likewise made in the form of a coil compression spring, is fixed to a valve ball 29 on the one hand and to a spring plate 19 of the pump spring 13 on the other hand. 31 is supported. The valve closing spring 30 is much weaker than the pump spring 13.

For convenience, a second check valve 27 ′ drawn only symbolically in the figure lies between the high pressure chamber 22 and the pressure tube 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 stepped piston 12 shown in FIG. 1, the stepped piston 12 has reached one stroke end position. In this position, the stepped piston 12 moves farthest to the left in FIG. 1, where hydraulic fluid is pumped from the pump chamber 22 to the pump outlet via a second check valve 27 ′ and a pressure tube 24. When the stepped piston 12 makes a return movement under the influence of the pump spring 13 (to the right in FIG. 1), the check valve 27 is opened, and the hydraulic fluid passes through the holes 25 and 26 from the pump chamber 21. Flows into the pump chamber (22). When the stepped piston 12 again moves to the left side of FIG. 1, when the check valve 27 is closed, hydraulic fluid is discharged from the pump chamber 22 to the pump outlet via the pressure pipe 24. At this time, the hydraulic fluid flows into the pump chamber 21 through the suction pipe 23 at the same time due to the difference between the diameters of the two guide devices 32a and 32b.

The connection of the pump chamber 21 and the pump chamber 22 described by way of example may be made in other ways. For example, the connection can be made to penetrate the pump body 10. It is also possible to replace, for example, edge control means with a check valve 27 which allows hydraulic fluid to flow from the pump chamber 21 to the pump chamber 22 and blocks the flow in the opposite direction.

In order to press-fit the bush 16 to the small cylinder portion 141 of the solid cylinder 14, accurate fitting is necessary. To this end, in the embodiment depicted in FIG. 1, the dimensions, shape and surface quality of the small diameter cylinder portion 141 should be sufficiently good. The fact that the dimensions, shape and surface quality of the reduced diameter part of the cylindrical body should be excellent means that the machining cost is increased compared to the case where only the largest diameter part of the cylindrical body should be processed to have the same characteristics.

In order to slide into the stepped piston 12 without damaging the bush 16, 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. It is desirable to have a chamfer. The manufacture of the tapered portion is not expensive or complicated, but plays a significant role as a whole because the pump is mass produced.

In the modified embodiment of the piston pump shown in cross-section in FIG. 2 to eliminate this difficulty in manufacturing and to lower the manufacturing cost of the solid cylinder 14, the inner hole is stepped in the bush 16 'when viewed in the axial direction. Puts. In this case, the cylinder portion 142 having a larger diameter can be penetrated and the tolerance of the outer diameter of the cylinder portion 142 having a larger diameter is extremely accurate, so that a good and reliable pressure fit of the bush 16 'is achieved. Since the large diameter cylinder portion 142 can be ground through, it is possible to improve the dimensions, shape and surface quality of the portion in a relatively simple manner. However, it would be costly to manufacture the small diameter cylinder portion 141 of the same quality. Since the remainder of the piston pump, shown in cross section in FIG. 2, is consistent with the piston 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.

To illustrate the embodiment of the bush 16 'more clearly, a longitudinal cross-sectional view of the bush 16' is shown in FIG. 3A. 3b shows 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 'includes a smaller bush portion 163' and a larger bush portion 165 ', and a shoulder 164' at a portion where the two bush portions 163 'and 165' are connected. There is a taper portion 166 'and an outer diameter 167'.

The diameter of the small diameter bush portion 163 'allows the bush 16' to be easily and without resistance until the large diameter 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. When viewed from the axial direction, the bush portion 163 'with a small diameter can be made very short. The inclination of the conical shoulder 164 'and the inclination of the conical shoulder 15 of the solid cylinder 14 are adjusted to each other so as not to affect the angle difference. Since the shoulder 164 'is inclined conically, the bush 16' is very easily passed through the edge at the connection between the left front 122 and the smaller diameter cylinder portion 141 to the solid cylinder 14 It is possible to fit, and it is not necessary to put a taper on this edge of the solid cylinder 14 for this purpose.

The diameter of the large diameter bush portion 165 'is such that the bush 16' is fully inserted into the solid cylinder 14, and the large diameter bush portion 165 'is press-fitted to the large diameter cylinder portion 142. The diameter is adjusted to each other with the diameter of the large cylinder portion 142 to be fixed by. 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 accurately placed in the solid cylinder 14 without much effort. .

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 does not enter the gap between the cylinder wall 111 and the outer diameter 167 '. , The diameter of the cylinder wall 111 is adjusted. 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 fixed to the solid 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.

With a suitably formed tool, a single process with high accuracy and low cost at the lower diameter of the bush 16 ', including bush portions 163', 165 ', shoulders 164' and tapered portions 166 ' Can be produced at Because of the guiding device 32b, the large cylinder portion 142 must be manufactured with high accuracy. In the embodiment depicted in FIG. 2, the bush 16 ′ is radially placed over the cylinder portion 142 fabricated with high accuracy because of the guide device 32 b, thereby securing the cylinder 16 for radial fixation of the bush 16 ′. It is not necessary to process separately in (14).

The modified embodiments of the bush 16 ′ depicted in FIGS. 3A and 3B differ in that the embodiment depicted in FIG. 3A places a recess 168 ′ on the side opposite the sliding ring 18 at the outer diameter 167 ′. 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 a recess 168 'to make room for these devices can shorten the overall length.

Bushes 16-16 'are fixed to the solid cylinder 14 of the stepped 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. When the stepped piston 12 moves the hydraulic fluid toward the pressure tube 24 during the one-way stroke, 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 and 16 'to press the shoulder 15. While the pressure in the high pressure chamber 22 is high during the one-way stroke, the pressure in the low pressure chamber 21 may be zero. By the shoulder 15 facing the high pressure chamber 22 from the solid cylinder 14, it is not difficult to block the force acting on the bushes 16 and 16 '. 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 seal 17, usually made of elastomer, seals the high pressure chamber 22 against the low pressure chamber 21. The seal 17 is fixed axially by the bushes 16, 16 ′. The seal 17 runs through the entire height of the annular annulus between the cylinder wall 111 and the smaller diameter cylinder portion 141. As a result, the seal 17 has a hydraulic fluid 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 solid cylinder 14 from the high pressure chamber 22. Do not pass through the gap to the low pressure chamber (21). The outer diameter and inner diameter of the bushes 16 and 16 'may be sealed with separate seals, respectively. However, this requires several seals. The embodiment drawn in the drawing has the advantage that the high pressure chamber 22 can be sealed with respect to the low pressure chamber 21 with one seal 17.

Piston pump according to the invention with the features of claim 1 can be manufactured at a very low cost, so that the cost is much lower than the stepped piston consisting of an integral rotating part or two parts of the piston rod and the piston cylinder. have. In the case of the piston pump according to the present invention, because the pump piston is made in a stepped shape, the pumping force is higher than a conventional stepped piston even at a low temperature. Will help.

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

Claims (14)

A stepped piston that is axially movable in the pump chamber, the stepped piston being a piston portion that divides the pump chamber into a low pressure chamber 21 and a high pressure chamber 22 of variable volume, in particular in a hydraulic brake device for a vehicle. In the piston pump for delivering the fluid, The stepped piston 12 is fixed to the solid cylinder 14 with a shoulder 15 facing the high pressure chamber 22, and fixed to the solid cylinder 14, and the pressure inside the high pressure chamber 22. And a bush (16, 16 ') for pressing the shoulder (15) by means of the piston pump. The piston pump according to claim 1, characterized in that the bush (16, 16 ') supports a seal (17) for sealing the high pressure chamber (22) against the low pressure chamber (21). 3. Piston pump according to claim 1 or 2, characterized in that the bush (16, 16 ') supports a sliding ring (18) for guiding the stepped piston (12) in the pump chamber (11). The piston pump (1) according to claim 1, characterized in that the bush (16: 16 ') is pressed against the solid cylinder (14) in a locking engagement manner by force. 5. The piston pump according to claim 4, wherein the bush (16: 16 ′) is in contact with a shoulder (15) which circulates around the solid cylinder (14) in front of the elastomeric seal (17). 4. The piston pump according to claim 3, wherein the sliding ring (18) is arranged between the bush (16) and the elastomeric seal (17) and is made of plastic, in particular of polytetrafluoroethylene (PTFE). . 3. The piston pump according to claim 1, wherein the piston pump comprises a piston restoring spring made in the form of a coil compression spring supported on one hand to a pedestal 20 in the pump chamber and on the other to a stepped piston 12. A piston pump, characterized in that. 3. Piston pump according to claim 1 or 2, characterized in that a connection is provided between the two pump chambers (21, 22) that can be closed by a control member. 9. The connection according to claim 8, characterized in that the connection between the two pump chambers (21, 22) is made in the form of holes (25, 26) in the stepped piston (12), and in the form of a check valve (27). Piston pump. 6. The cylinder portion 141 of the solid cylinder 14, as defined by the bush 16: 16 ', has a reduced outer diameter relative to the cylinder diameter, and the shoulder 15 has a smaller diameter. Piston pump, characterized in that for forming a connecting portion connecting the portion 141 and the outer surface of the large diameter cylinder portion (142). 11. The method according to claim 10, wherein the bush (16) is placed in the small diameter cylinder portion (141), and the inner surface of the bush (16) and the outer surface of the small diameter cylinder portion (141) are locked by force. Piston pump characterized by. 11. The method of claim 10, wherein the inner diameter of the bush 16 'is formed stepwise so that the bush portion 16 ' has a small inner diameter bush portion 163' and a large inner diameter bush portion 165 ', and has a small inner diameter. The bush portion 163 'is mounted with a relatively large clearance on the small diameter cylinder portion 141, and the annular inner surface of the large bush portion 165' and the outside of the large diameter cylinder portion 142 are mounted. A piston pump, characterized in that the surface is locked by force. 13. The piston pump according to claim 12, wherein the shoulder (164 ') formed between the two bush portions (163', 165 ') is inclined in a conical shape so that the bush (16') can be easily assembled. 14. Piston pump according to claim 12 or 13, characterized in that the large diameter cylinder portion (142) is ground to the correct diameter without sharp edges.