Ball screw structure, servo voltage buildup unit and integrated intelligent braking system

Abstract

The invention relates to a ball screw structure, a servo voltage buildup unit and an integrated intelligent braking system, the ball screw structure comprises a screw, a nut and an anti-rotation piece, the nut coaxially sleeves one end of the screw, and the nut is in relative rotation connection with the screw through a plurality of steel balls; the anti-rotation piece is arranged outside the lead screw in a sleeving mode, and the nut is located between the lead screw and the anti-rotation piece. And the anti-rotation piece is clamped and matched with the nut. The ball screw structure has the beneficial effects that the T-shaped boss of the anti-rotation piece in the ball screw structure is directly clamped in the T-shaped groove of the nut, the T-shaped clamping groove penetrates through the outer side of the whole nut, the structure is more stable, parts are easy to machine, and assembly of a production line is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of ball screws, and specifically relates to a ball screw structure, a servo pressure building unit and an integrated intelligent braking system. Background Art

[0002] In recent years, with the accelerating development of automotive electrification and intelligence, more requirements have been put forward for the by-wire chassis. With the increasing penetration rate of new energy vehicles, shorter development cycles, faster product iteration speeds, better supporting and response capabilities, and cost gene advantages in the chassis system have become new trends in the development of the chassis system. The application of ball screws in the by-wire braking system can greatly save structural space, and has fast response and high efficiency.

[0003] The braking system integrated with ball screws can efficiently convert the rotational speed and torque output by the servo motor into linear motion; due to the unique characteristics of ball screws, their application in the by-wire braking system can greatly save structural space, have fast response, high efficiency, and the ball screws have less noise, so they are increasingly favored by major automobile manufacturers.

[0004] The traditional servo pressure building unit of the braking system has a transmission mechanism including a ball screw mechanism and a gear mechanism, with defects such as complex structure, high noise, low efficiency, and high requirements for production line processes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a ball screw structure, a servo pressure building unit and an integrated intelligent braking system, aiming to solve the problems in the prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A ball screw structure includes a screw rod, a nut and an anti-rotation member. The nut is coaxially sleeved outside one end of the screw rod, and is rotatably connected to the screw rod through a plurality of steel balls; the anti-rotation member is sleeved outside the screw rod, and the nut is located between the screw rod and the anti-rotation member; the anti-rotation member is in clamping fit with the nut.

[0008] The beneficial effect of the present invention is that during operation, the screw rod is fixedly connected to the hollow shaft of the servo motor. When the servo motor works, the screw rod rotates together with the hollow shaft, driving the steel balls to roll in the screw rod raceway. The movement trajectory of the steel balls advances spirally along the axial direction of the screw rod, and the movement direction has a circumferential direction and an axial direction, driving the nut to move. Since the freedom degree of the nut in the circumferential direction is restricted by the anti-rotation member, it can only move axially.

[0009] In the ball screw structure provided by the present invention, the anti-rotation member is directly clamped on the nut, the structure is more stable, the processing of parts is simple, and it is convenient for assembly on the production line.

[0010] On the basis of the above technical solutions, the present invention can be further improved as follows.

[0011] Further, a card slot group is provided on the lead nut, a boss group is provided on the anti-rotation member, and the boss group extends into the card slot group.

[0012] The beneficial effect of adopting the above further solution is that the boss group on the anti-rotation member is directly stuck in the card slot group on the lead nut, the structure is more stable, the parts are simple to process, and it is convenient for production line assembly. The structure is simple and the design is reasonable.

[0013] Further, the card slot group includes at least one card slot, the boss group includes at least one boss corresponding to the card slot one by one, and each boss extends into the corresponding card slot.

[0014] The beneficial effect of adopting the above further solution is that the boss on the anti-rotation member is directly stuck in the card slot on the lead nut, the structure is more stable, the parts are simple to process, and it is convenient for production line assembly. The structure is simple and the design is reasonable.

[0015] Further, the card slot group includes a plurality of the card slots, and the plurality of card slots are evenly spaced along the circumferential direction of the lead nut; the boss group includes a plurality of the bosses, and the plurality of bosses are evenly spaced in a circular shape on the anti-rotation member and respectively extend into the plurality of card slots.

[0016] The beneficial effect of adopting the above further solution is that the number of the card slots and the bosses is reasonably designed, further ensuring the stability of the whole structure.

[0017] Further, the cross section of each card slot is in a T-shaped groove structure, and the cross section of each boss is in a T-shaped structure and its size matches that of the card slot.

[0018] The beneficial effect of adopting the above further solution is that the shapes of the card slots and the bosses are reasonably designed, the clamping is more stable, and the stability of the whole structure is further ensured.

[0019] Further, it further includes a piston, the piston is sleeved on the other end of the lead screw, and one end of the piston is fixedly connected to one end of the lead nut; the anti-rotation member is located outside the piston.

[0020] The beneficial effect of adopting the above further solution is that during operation, the lead screw is fixedly connected to the hollow shaft of the servo motor. When the servo motor works, the lead screw rotates together with the hollow shaft, driving the steel balls to roll in the lead screw raceway. The movement trajectory of the steel balls advances spirally along the axial direction of the lead screw, and the movement direction has a circumferential direction and an axial direction, driving the lead nut to move. Since the circumferential degree of freedom of the lead nut is restricted by the anti-rotation member, it can only move axially;

[0021] Meanwhile, the torque of the servo motor is transmitted to the lead screw. The lead screw raceway pushes the steel balls, the steel balls push the nut, and the nut pushes the piston, ultimately converting the torque of the hollow shaft of the servo motor into the axial force of the piston.

[0022] Since the piston is connected to the nut, the axial movement of the nut drives the axial movement of the piston, ultimately converting the rotation of the hollow shaft of the servo motor into the linear movement of the piston.

[0023] Furthermore, the other end of the piston is connected to the other end of the lead screw through a limit screw, and a buffer rubber pad and a buffer gasket are respectively sleeved on one end of the limit screw, and the buffer gasket is located between the other end of the lead screw and the buffer rubber pad.

[0024] The beneficial effect of adopting the above further scheme is that on the one hand, the limit screw is used to limit the position of the lead screw in the piston, and on the other hand, when the piston retracts to contact the other end of the lead screw, the buffer rubber pad and the buffer gasket can play a buffering role, avoiding large impacts on the mechanical structure of the system and extending the service life.

[0025] Furthermore, one end of the lead screw is provided with a fixing screw for fixedly connecting it to the motor housing.

[0026] The beneficial effect of adopting the above further scheme is that the structure is simple and reasonable, and the lead screw and the motor housing can be connected by the fixing screw.

[0027] The present invention also relates to a servo pressure building unit, including the ball screw structure as described above.

[0028] The beneficial effect of adopting the above further scheme is that the present invention also relates to a servo pressure building unit, and this servo pressure building unit has a powerful structure, is compact in structure, saves the space of the servo pressure building unit, and optimizes the natural frequency.

[0029] The present invention also relates to an integrated intelligent braking system, including the servo pressure building unit as described above.

[0030] The beneficial effect of adopting the above further scheme is that the present invention also relates to an integrated intelligent braking system, and this integrated intelligent braking system has a powerful structure, is compact in structure, saves the space, and optimizes the natural frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is the overall structural schematic diagram of the present invention;

[0032] Figure 2 is Figure 1 the sectional view taken along the line A-A in

[0033] Figure 3 is Figure 1 the sectional view taken along the line B-B in

[0034] Figure 4 is the top view of the present invention;

[0035] Figure 5 is the schematic structural view of the lead nut in the present invention;

[0036] Figure 6 is the schematic structural view of the anti-rotation member in the present invention.

[0037] In the attached drawings, the list of components represented by each reference numeral is as follows:

[0038] 1. Lead screw; 2. Lead nut; 3. Anti-rotation member; 4. Steel ball; 5. Card slot; 6. Boss; 7. Piston; 8. Limit screw; 9. Buffer rubber pad; 10. Buffer gasket; 11. Fixing screw. Detailed embodiments

[0039] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the attached drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0041] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0042] The present invention will be described in detail below with reference to the attached drawings and in combination with embodiments.

[0043] Embodiment 1

[0044] As Figures 1 to 6 shown, this embodiment provides a ball screw structure, including a lead screw 1, a nut 2 and an anti-rotation member 3. The nut 2 is coaxially sleeved outside one end of the lead screw 1 and is relatively rotatably connected to the lead screw 1 through a plurality of steel balls 4. The anti-rotation member 3 is sleeved outside the lead screw 1, and the nut 2 is located between the lead screw 1 and the anti-rotation member 3. The anti-rotation member 3 is in snap-fit with the nut 2.

[0045] During operation, the lead screw 1 is fixedly connected to the hollow shaft of the servo motor. When the servo motor works, the lead screw 1 rotates together with the hollow shaft, driving the steel balls 4 to roll in the raceway of the lead screw 1. The movement trajectory of the steel balls 4 advances spirally along the axial direction of the lead screw 1. The movement directions are the circumferential direction and the axial direction, driving the nut 2 to move. Since the freedom degree of the nut 2 in the circumferential direction is restricted by the anti-rotation member 3, it can only move axially.

[0046] At the same time, the torque of the servo motor is transmitted to the lead screw 1. The raceway of the lead screw 1 pushes the steel balls 4, the steel balls 4 push the nut 2, and the nut 2 pushes the piston, finally realizing the conversion of the torque of the hollow shaft of the servo motor into the axial force of the piston.

[0047] Preferably, in this embodiment, the above anti-rotation member 3 is preferably a cylindrical structure, and a channel with both ends open is provided therein. The nut 2 and the lead screw 1 are located in the channel, and both ends of the lead screw 1 respectively extend outside both ends of the anti-rotation member 3.

[0048] In addition, the anti-rotation member also serves as the carrier of the system and can bear the weight and load of the ball screw.

[0049] Preferably, in this embodiment, the lead screw 1 is a rotating component of the ball screw system. It is fixedly connected to the hollow shaft of the servo motor, and the rotational kinetic energy is transmitted to the steel balls 4 through the raceway of the lead screw. The steel balls 4 further transmit it to the nut 2 to achieve the transmission of kinetic energy.

[0050] In addition, the nut 2, as an execution component for transmitting axial movement and axial force in the ball screw system, is a key component of the system and has high requirements for structural strength and precision.

[0051] Preferably, in this embodiment, the design of the above steel balls 4 directly affects the rated dynamic load and rated static load of the ball screw system. Therefore, the design and selection of the steel balls 4 are quite critical. The function of the steel balls 4 is that the rotational kinetic energy of the lead screw 1 is transmitted to the steel balls 4 through the raceway, and the steel balls 4 further transmit it to the nut 2. It is a transitional component for kinetic energy transmission.

[0052] In the ball screw structure provided by this embodiment, the anti-rotation member 3 is directly stuck on the nut 2, the structure is more stable, the parts processing is simple, and it is convenient for production line assembly.

[0053] Embodiment 2

[0054] Based on Embodiment 1, in this embodiment, a card slot group is provided on the lead screw nut 2, a boss group is provided on the anti-rotation member, and the boss group extends into the card slot group.

[0055] The boss group on the anti-rotation member 3 is directly stuck in the card slot group on the lead screw nut 2, with a more stable structure, simple processing of components, and convenient assembly on the production line. The structure is simple and reasonably designed.

[0056] Embodiment 3

[0057] Based on Embodiment 2, in this embodiment, the card slot group includes at least one card slot 5, the boss group includes at least one boss 6 corresponding to the card slot 5 one by one, and each boss 6 extends into the corresponding card slot 5.

[0058] The boss 6 on the anti-rotation member 3 is directly stuck in the card slot 5 on the lead screw nut 2, with a more stable structure, simple processing of components, and convenient assembly on the production line. The structure is simple and reasonably designed.

[0059] Embodiment 4

[0060] Based on Embodiment 3, in this embodiment, the card slot group includes a plurality of the card slots 5, and the plurality of card slots 5 are evenly spaced along the circumferential direction of the lead screw nut 2; the boss group includes a plurality of the bosses 6, and the plurality of bosses 6 are evenly spaced in a circular pattern on the anti-rotation member 3 and respectively extend into the plurality of card slots 5.

[0061] The number of the card slots 5 and the bosses 6 is reasonably designed to further ensure the stability of the whole structure.

[0062] Preferably, in this embodiment, preferably two of the above-mentioned card slots 5 are relatively installed on the lead screw nut 2, and preferably two of the bosses 6 are relatively arranged on the inner wall of the anti-rotation member 3 and respectively correspond to the two card slots 5 one by one.

[0063] In addition, both ends of each card slot 5 are open.

[0064] Embodiment 5

[0065] Based on any one of Embodiments 3 to 4, in this embodiment, the cross-section of each card slot 5 is in a T-shaped groove structure, and the cross-section of each boss 6 is in a T-shaped structure, and its size matches that of the card slot 5.

[0066] The shapes of the card slots 5 and the bosses 6 are reasonably designed, and the clamping is more stable, further ensuring the stability of the whole structure.

[0067] Alternatively, each of the above card slots 5 may also be a long strip-shaped rectangular groove body, and each boss 6 may also be a long strip-shaped structure matching the shape of the card slot 5.

[0068] Embodiment 6

[0069] Based on the above embodiments, this embodiment further includes a piston 7. The piston 7 is sleeved on the other end of the lead screw 1, and one end of the piston 7 is fixedly connected to one end of the nut 2; the anti-rotation member 3 is located outside the piston 7.

[0070] During operation, the lead screw 1 is fixedly connected to the hollow shaft of the servo motor. When the servo motor works, the lead screw 1 rotates together with the hollow shaft, driving the steel balls 4 to roll in the raceway of the lead screw 1. The movement trajectory of the steel balls 4 advances spirally along the axial direction of the lead screw 1, and the movement direction has a circumferential direction and an axial direction, driving the nut 2 to move. Since the freedom degree of the nut 2 in the circumferential direction is restricted by the anti-rotation member 3, it can only move axially;

[0071] At the same time, the torque of the servo motor is transmitted to the lead screw 1. The lead screw raceway pushes the steel balls, the steel balls 4 push the nut 2, and the nut 2 pushes the piston 7, finally realizing the conversion of the torque of the servo motor hollow shaft into the axial force of the piston 7;

[0072] Since the piston 7 is connected to the nut 2, the axial movement of the nut 2 drives the axial movement of the piston 7, finally realizing the conversion of the rotation of the servo motor hollow shaft into the linear movement of the piston 7.

[0073] Based on the above scheme, the above piston 7 has a cylindrical structure, with one end open and the other end closed.

[0074] Preferably, in this embodiment, the above piston 7 realizes the sealing of the cylinder block and compresses the liquid to build pressure.

[0075] Embodiment 7

[0076] Based on Embodiment 6, in this embodiment, the other end of the piston 7 is connected to the other end of the lead screw 1 through a limit screw 8, and a buffer rubber pad 9 and a buffer gasket 10 are respectively sleeved on one end of the limit screw 8, and the buffer gasket 10 is located between the other end of the lead screw 1 and the buffer rubber pad 9.

[0077] On the one hand, the limit screw 8 is used to limit the position of the lead screw 1 in the piston 7. On the other hand, when the piston 7 retracts to contact the other end of the lead screw 1, the buffer rubber pad 9 and the buffer gasket 10 can play a buffering role, avoiding large impacts on the system mechanical mechanism and prolonging the service life.

[0078] Based on the above scheme, the other end of the above lead screw 1 is provided with a thread connection with the limit screw 8.

[0079] Example 8

[0080] Based on the above embodiments, in this embodiment, a fixing screw 11 for fixedly connecting the lead screw 1 to the motor housing is installed at one end of the lead screw 1.

[0081] This solution has a simple structure and reasonable design, and the fixing screw 11 can be used to connect the lead screw 1 and the motor housing.

[0082] Based on the above solution, the fixing screw 11 is threadedly connected to one end of the lead screw 1, and a threaded hole for threadedly connecting with the fixing screw 11 is provided at one end of the lead screw 1.

[0083] Example 9

[0084] Based on the above embodiments, this embodiment further provides a servo pressure building unit, including the ball screw structure as described above.

[0085] This embodiment also relates to a servo pressure building unit, which has a powerful structure, is compact, saves the space of the servo pressure building unit, and optimizes the natural frequency.

[0086] Example 10

[0087] Based on the above embodiments, this embodiment further provides an integrated intelligent braking system, including the servo pressure building unit as described above.

[0088] This embodiment also relates to an integrated intelligent braking system, which has a powerful structure, is compact, saves the space, and optimizes the natural frequency.

[0089] The working principle of the present invention is as follows:

[0090] During operation, the lead screw 1 is fixedly connected to the hollow shaft of the servo motor. When the servo motor works, the lead screw 1 rotates together with the hollow shaft, driving the steel balls 4 to roll in the raceway of the lead screw 1. The movement trajectory of the steel balls 4 advances spirally along the axial direction of the lead screw 1, and the movement directions are the circumferential direction and the axial direction, driving the nut 2 to move. Since the degree of freedom of the nut 2 in the circumferential direction is restricted by the anti-rotation member 3, it can only move axially;

[0091] At the same time, the torque of the servo motor is transmitted to the lead screw 1. The lead screw raceway pushes the steel balls, the steel balls 4 push the nut 2, and the nut 2 pushes the piston 7, finally realizing the conversion of the torque of the servo motor hollow shaft into the axial force of the piston 7;

[0092] Since the piston 7 is connected to the nut 2, the axial movement of the nut 2 drives the axial movement of the piston 7, finally realizing the conversion of the rotation of the servo motor hollow shaft into the linear movement of the piston 7.

[0093] The advantages of each structure of the present invention are as follows:

[0094] 1. Unique anti-rotation connection structure: The anti-rotation part is fixed to the nut. The anti-rotation part is designed with a through T-shaped boss, and the nut is designed with a through T-shaped groove, which are in clearance fit. The anti-rotation part is directly fixed to the motor housing. Advantages: High structural stiffness, reduced vibration, and thus reduced noise;

[0095] 2. Unique anti-rotation part design: The flange end of the anti-rotation part is embedded in the groove at the mouth of the motor housing, and also serves as the carrier of the ball screw, capable of bearing the weight and load of the ball screw; The middle of the flange surface is hollowed out to avoid the male head of the motor and the male head of the motor position sensor; Advantages: Strong structure, compact structure, saving space for the servo pressure building unit, and optimizing the natural frequency;

[0096] 3. Unique fourth rod connection method: The tail end is fixedly connected to the motor hollow shaft through standard bolts, avoiding the press-fit connection of other designs; Advantages: Small moment of inertia, improved response time and energy efficiency; Simple processing technology and easier assembly;

[0097] 4. Unique buffer structure: The screw buffer rubber pad (part 06) is installed at the top of the screw, fixed by bolts and buffer washers, and becomes a component with the screw; Advantages: Simple and reliable assembly process in the production line;

[0098] 5. Unique ball screw parameter design: Lead 3mm, ball diameter 2mm, effective number of turns 6; Advantages: Increased effective number of turns, large rated static and dynamic loads, and strong load-bearing capacity; Small-diameter balls, more uniform layout, and low noise.

[0099] The ball screw system of the present invention:

[0100] 1. Realize the conversion of the rotation of the servo motor hollow shaft / screw into the linear motion of the piston;

[0101] 2. Realize the conversion of the torque of the servo motor hollow shaft / screw into the axial force of the piston;

[0102] 3. Realize the anti-rotation of the nut;

[0103] 4. Realize the piston compressing the liquid to build liquid pressure.

[0104] The present invention makes the servo pressure building unit integrated with an intelligent braking system more compact, lighter in weight, and higher in manufacturing feasibility.

[0105] In addition, in the ball screw structure of the present invention, the T-shaped boss of the anti-rotation part directly fits into the T-shaped groove of the nut, as shown in Figures 2 - 4 , and the T-shaped card slot runs through the entire outer side of the nut, with a more stable structure, simple processing of parts, and convenient assembly in the production line.

[0106] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0107] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0108] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A ball screw structure, characterized in that: It includes a lead screw (1), a nut (2) and an anti-rotation part (3). The nut (2) is coaxially sleeved outside one end of the lead screw (1), and is relatively rotationally connected to the lead screw (1) through a plurality of steel balls (4); the anti-rotation part (3) is sleeved outside the lead screw (1), and the nut (2) is located between the lead screw (1) and the anti-rotation part (3); the anti-rotation part (3) is snap-fitted with the nut (2).

2. The ball screw structure according to claim 1, wherein: The nut (2) is provided with a card slot group, and the anti-rotation part (3) is provided with a boss group, and the boss group extends into the card slot group.

3. The ball screw structure according to claim 2, characterized in that: The card slot group includes at least one card slot (5), the boss group includes at least one boss (6) corresponding to the card slot (5) one by one, and each boss (6) extends into the corresponding card slot (5).

4. The ball screw structure according to claim 3, wherein: The card slot group includes a plurality of the card slots (5), and the plurality of card slots (5) are evenly spaced along the circumferential direction of the nut (2); the boss group includes a plurality of bosses (6), and the plurality of bosses (6) are evenly spaced in a circular shape on the anti-rotation part (3) and respectively extend into the plurality of card slots (5).

5. The ball screw structure according to claim 3, wherein: The cross section of each card slot (5) is in a T-shaped groove structure, and the cross section of each boss (6) is in a T-shaped structure, and its size matches that of the card slot (5).

6. The ball screw structure according to any one of claims 1-5, characterized in that: It further includes a piston (7), the piston (7) is sleeved on the other end of the lead screw (1), and one end of it is fixedly connected to one end of the nut (2); the anti-rotation part (3) is located outside the piston (7).

7. The ball screw structure according to claim 6, characterized in that: The other end of the piston (7) is connected to the other end of the lead screw (1) through a limit screw (8), and a buffer rubber pad (9) and a buffer gasket (10) are respectively sleeved on one end of the limit screw (8), and the buffer gasket (10) is located between the other end of the lead screw (1) and the buffer rubber pad (9).

8. The ball screw structure according to any one of claims 1-5, characterized in that: One end of the lead screw (1) is installed with a fixing screw (11) for fixedly connecting it to the motor housing.

9. A servo pressure building unit, characterized in that: It includes the ball screw structure according to any one of claims 1-8.

10. An integrated intelligent braking system, characterized in that: It includes the servo pressure building unit according to claim 9.

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