阅读说明：本技术 通气塞和变速箱 (Breather plug and gearbox ) 是由 陈功 凤均军 王新博 黄欢 刘平 于 2020-05-28 设计创作，主要内容包括：本发明提供一种变速箱和通气塞,通气塞包括形成阀腔的阀体以及阀芯,阀腔包括大腔和小腔,阀芯包括大端、小端；所述大端、所述小端分别与大腔、小腔滑动配合,且端壁均与阀腔的腔端壁之间设有预压缩的弹簧；小端、大端分隔所述阀腔为第一腔、中间腔、第二腔；小腔、大腔对应的阀体部分,还分别设有贯通内外的第一通气口、第二通气口,中间腔压力与外部相等时,第一、第二通气口与中间腔不连通,中间腔与外部存在压差时,能够推动阀芯轴向移动,使中间腔连通第一或第二通气口。本方案中通气塞可实现双向通气,变速箱内气压较低或较高均可以实现通气,从而保护油封等密封件,保证变速箱的可靠性。(The invention provides a gearbox and a vent plug, wherein the vent plug comprises a valve body and a valve core, the valve body and the valve core form a valve cavity, the valve cavity comprises a large cavity and a small cavity, and the valve core comprises a large end and a small end; the large end and the small end are respectively in sliding fit with the large cavity and the small cavity, and pre-compressed springs are arranged between the end walls and the cavity end wall of the valve cavity; the small end and the large end separate the valve cavity into a first cavity, a middle cavity and a second cavity; the valve body parts corresponding to the small cavity and the large cavity are also respectively provided with a first vent hole and a second vent hole which are communicated with the inside and the outside, when the pressure of the middle cavity is equal to the outside, the first vent hole and the second vent hole are not communicated with the middle cavity, and when the pressure difference exists between the middle cavity and the outside, the valve core can be pushed to move axially, so that the middle cavity is communicated with the first vent hole or the second vent hole. Two-way ventilation can be realized to the stopper of ventilating in this scheme, and the gearbox internal gas pressure is lower or higher all can realize ventilating to sealing members such as protection oil blanket guarantee the reliability of gearbox.)

1. The vent plug is characterized by comprising a valve body (10) formed with a valve cavity and a valve core arranged in the valve cavity, wherein the valve cavity comprises a large cavity and a small cavity, and the valve core comprises a large end (202) and a small end (201); the peripheral wall of the large end (202) and the peripheral wall of the small end (201) are respectively in sliding fit with the peripheral wall of the large cavity and the peripheral wall of the small cavity, and pre-compressed springs are arranged between the end walls and the cavity end wall of the valve cavity; the small end (201) and the large end (202) divide the valve cavity into a first cavity (101), an intermediate cavity (103) and a second cavity (102), and the intermediate cavity (103) is used for communicating with a gearbox;

the valve body part that the loculus, the loculus corresponds still is equipped with respectively and link up inside and outside first air vent (10c), second air vent (10a), middle chamber (103) pressure is equal with the outside, first air vent (10c), second air vent (10a) with middle chamber (103) do not communicate, when middle chamber (103) and outside have pressure differential, can promote case axial displacement, so that middle chamber (103) intercommunication first air vent (10c) or second air vent (10 a).

2. The vent plug according to claim 1, wherein the valve body portions of the first chamber (101) and the second chamber (102) are provided with a first normal port (10d) and a second normal port (10b) for communicating the inside and the outside, respectively.

3. The vent plug according to claim 2, wherein the first vent opening (10d), the second vent opening (10b), the first vent opening (10c), and the second vent opening (10a) are provided at a bottom of the valve body (10).

4. A vent plug according to any of claims 1 to 3, wherein the small end (201) and the large end (202) are each provided with a stud facing the chamber end wall of the respective valve chamber, said studs being inserted in the respective springs.

5. A vent plug according to any of claims 1 to 3, wherein the peripheral walls of the large end (202) and the small end (201) of the valve element are provided with annular pressure equalization grooves.

6. A vent plug according to any of claims 1 to 3, wherein the valve chamber is a cylindrical valve chamber and/or the valve body (10) is a square valve body.

7. The vent plug of claim 6, wherein the valve body (10) includes a major segment and a minor segment forming the major and minor cavities, respectively.

8. A vent plug according to any of claims 1 to 3, wherein the valve body portion associated with the intermediate chamber (103) is provided with a socket, the vent plug further comprising a connector (50), one end of the connector (50) being sealingly engageable with the socket and the other end being adapted to communicate with a transmission case.

9. The vent plug of claim 8, wherein a seal (40) is provided at the location where the connector (50) and the valve body (10) meet to achieve a sealed plug-in connection.

10. Gearbox comprising a housing provided with a vent hole, characterised in that the vent hole is fitted with a vent plug according to any of claims 1-9.

Technical Field

The invention relates to the technical field of valve bodies, in particular to a temperature regulating valve.

Background

When the automobile gearbox works, the temperature in the gearbox is high, and the gas is thermally expanded; high temperatures also cause transmission oil to produce vapor that fills the tank space, causing the pressure in the tank to rise further. In winter or night, the air pressure in the gearbox is reduced after the temperature is reduced. When the pressure in the gearbox is greatly different from the external pressure, the pressure can impact the sealing element of the gearbox, and the sealing element is worn out and fails prematurely, so that oil leakage and other fault phenomena occur repeatedly.

In order to solve the problems, a vent plug is arranged on an automobile gearbox at present, so that the inside of the automobile gearbox can be communicated with the outside atmosphere, and the inside of the gearbox is balanced with the outside air pressure.

The existing vent plug mainly comprises a normally open type vent plug and a normally closed type vent plug.

Normally open breather plug can not effectively prevent impurity such as outside water, dust from getting into inside the gearbox, for example common labyrinth breather plug. And the normally open vent plugs are made of high-molecular materials, so that oil and water cannot permeate through the vent plugs, and gas can permeate through the vent plugs normally. However, after the air permeable film is splashed with oil and water, micropores in the air permeable film are blocked, so that the air permeability is reduced, and even the air permeable film fails.

The normally closed vent plug is opened in a single direction, and when the pressure in the gearbox rises, the vent plug is opened, and the internal air pressure and the external air pressure are communicated. However, when the temperature of the gearbox is reduced, the air pressure in the gearbox is reduced, and the outside air cannot be supplemented into the gearbox, so that the oil seal is abraded, and the reliability of the gearbox is reduced.

Disclosure of Invention

The invention provides a vent plug, which comprises a valve body and a valve core, wherein the valve body is provided with a valve cavity, the valve core is arranged in the valve cavity, the valve cavity comprises a large cavity and a small cavity, and the valve core comprises a large end and a small end; the peripheral wall of the large end and the peripheral wall of the small end are respectively in sliding fit with the peripheral wall of the cavity of the large cavity and the peripheral wall of the cavity of the small cavity, and pre-compressed springs are arranged between the end walls and the cavity end wall of the valve cavity; the small end and the large end separate the valve cavity into a first cavity, a middle cavity and a second cavity, and the middle cavity is used for communicating with a gearbox;

the valve body part that the loculus, the loculus corresponds still is equipped with first blow vent, the second blow vent inside and outside lining up respectively, when middle chamber pressure is equal with the outside, first blow vent, the second blow vent with middle chamber does not communicate, when middle chamber has pressure differential with the outside, can promote case axial displacement, so that middle chamber intercommunication first blow vent or the second blow vent.

Optionally, the valve body portion corresponding to the first cavity and the second cavity is respectively provided with a first normal opening and a second normal opening which communicate the inside and the outside.

Optionally, the first normal opening, the second normal opening, the first vent, and the second vent are all disposed at the bottom of the valve body.

Optionally, the small end and the large end are respectively provided with a protrusion facing the cavity end wall of the corresponding valve cavity, and the protrusion is inserted into the corresponding spring.

Optionally, the peripheral walls of the large end and the small end of the valve core are provided with annular pressure equalizing grooves.

Optionally, the valve cavity is a cylindrical valve cavity, and/or the valve body is a square valve body.

Optionally, the valve body comprises a large section and a small section, forming the large chamber and the small chamber, respectively.

Optionally, a plug hole is formed in a valve body portion corresponding to the middle cavity, the vent plug further comprises a connector, one end of the connector is inserted into the plug hole in a sealing mode, and the other end of the connector is used for being communicated with a gearbox.

Optionally, a sealing element is arranged at a position where the joint and the valve body are connected to realize sealed insertion.

The invention also provides a gearbox, which comprises a box body, wherein the box body is provided with a vent hole, and the vent hole is provided with any one of the vent plugs.

The gearbox and the breather plug that this scheme provided, the breather plug sets up through the ladder cavity structure in big chamber, loculus to and the big end of case, tip setting form the cross-section long-pending poor, the pressure change in middle chamber like this, when being less than or being greater than external pressure, the case can receive the pressure differential effect, thereby it moves left or moves right to push away the case, so that be located the first blow vent or the second blow vent and the middle chamber intercommunication of the left and right sides, thereby open the breather plug and realize ventilating of gearbox. Therefore, the ventilation plug in the scheme can realize bidirectional ventilation, and ventilation can be realized at lower or higher air pressure in the gearbox, so that sealing elements such as oil seals are protected, and the reliability of the gearbox is ensured. Moreover, compare in the plug of ventilating of unidirectional normal close formula, the plug of ventilating that this scheme provided can two-way ventilation, compare in the plug of ventilating of open in usual, the plug of ventilating that this scheme provided can obviously block into the gearbox better, impurity etc. and compare in the ventilative membrane material of polymer among the prior art, the plug of ventilating of this scheme is low to the sensitivity of fluid, the gearbox is at the operation in-process, if the plug of ventilating is infected with fluid, can not block the plug of ventilating, still accessible case removes, discharges fluid from the blow vent.

Drawings

FIG. 1 is a schematic diagram of a vent plug according to one embodiment of the present invention;

FIG. 2 is a schematic view of the valve spool of FIG. 1 moving to the right to a critical open state of the second vent;

FIG. 3 is a schematic diagram of the valve core of FIG. 1 moving to the left with the first vent port in a critical open state;

FIG. 4 is a schematic perspective view of the vent plug of FIG. 1;

fig. 5 is a schematic structural view of the valve core in fig. 1.

The reference numerals in fig. 1-5 are illustrated as follows:

10-a valve body; 101-a first cavity; 102-a second cavity; 103-an intermediate cavity;

10 a-a second vent; 10 b-a second normal opening; 10 c-a first vent; 10 d-a first normal opening;

201-small end; 201 a-a first stud; 201 b-a pressure equalizing groove; 202-big end; 202 a-a second stud; 202 b-a voltage-equalizing groove; 203-middle section;

31-a first spring; 32-a second spring;

40-a seal; 50-a linker.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of a vent plug according to the present invention, which shows a state when the transmission case pressure is equal to the external atmospheric pressure.

The vent plug provided by the embodiment comprises a valve body 10 and a valve core, wherein a valve cavity is formed in the valve body 10, and the valve core is arranged in the valve cavity and can move back and forth along the axial direction of the valve cavity. Specifically, as shown in fig. 1, the valve cavity includes a small cavity and a large cavity which are connected in sequence, and the term "large" and "small" as used herein means that the sectional areas are different in size. The radial dimension of the small cavity is smaller than that of the large cavity in terms of size, when the valve cavity is cylindrical, the radial direction is circular and radial, and when the valve cavity is non-circular, the radial direction refers to the direction radiating around along the central axis. The valve cavity of the embodiment is cylindrical, and the valve core is correspondingly cylindrical, so that the sliding fit between the valve core and the cavity peripheral wall of the valve cavity is facilitated.

Continuing looking at fig. 1, the valve core is adapted to the valve cavity, and comprises a small end 201, a middle section 203 and a large end 202 which are connected in sequence from left to right, wherein the large and small also represent the sectional areas, and the sectional area relationship of the three is as follows: middle section 203< small end 201< large end 202. The peripheral wall of the large end 202 and the peripheral wall of the small end 201 are in sliding fit with the peripheral wall of the large cavity and the peripheral wall of the small cavity respectively, the middle section 203 is distant from the peripheral wall of the valve cavity, at the moment, the small end 201 and the large end 202 divide the valve cavity into a first cavity 101, a middle cavity 103 and a second cavity 102 along the axial direction, the middle cavity 103 is composed of a part of small cavities and a part of large cavities, and the three cavities are not communicated with each other in the valve cavity. When the vent plug is mounted to the transmission, the intermediate chamber 103 of the valve chamber is used to communicate with the transmission so that the pressure in the intermediate chamber 103 will be the same as the pressure in the transmission.

Pre-compressed springs are arranged between the end walls of the large end 202 and the small end 201 and the cavity end wall of the valve cavity, as shown in fig. 1, the end wall of the small end 201 is the left end wall of the valve core, a first spring 31 is arranged between the end wall of the large end 201 and the left end cavity wall of the valve cavity, the end wall of the large end 202 is the right end wall of the valve core, a second spring 32 is arranged between the end wall of the right end cavity of the valve cavity and the end wall of the valve core, the two springs are always kept in a compressed state, and in order to stably install the springs, protruding columns are respectively arranged on the end walls, facing the corresponding cavities, of the large end 202 and the small end 201 so as to insert the corresponding springs. In fig. 1, a left end wall of the small end 201 is provided with a first stud 201a, a first spring 31 is sleeved on the first stud 201a, a right end wall of the large end 202 is provided with a second stud 202a, and a second spring 32 is sleeved on the second stud 202a, but the springs may be directly abutted or connected to the corresponding large end 202 or the small end 201 by means of bonding or the like.

The valve body 10 corresponding to the large chamber and the small chamber is provided with a first vent hole 10c and a second vent hole 10a penetrating inside and outside, respectively. And is arranged to: when the pressure of the middle cavity 103 is equal to the external pressure, the first vent 10c and the second vent 10a are not communicated with the middle cavity 103, and when the pressure difference exists between the middle cavity 103 and the outside, the valve core can be pushed to move axially, so that the middle cavity 103 is communicated with the first vent 10c or the second vent 10 a. Namely, when the air pressure in the gearbox is low, the external air pressure can be supplemented, when the air pressure is high, the external air pressure can be exhausted outwards through the vent hole, and therefore the vent plug can realize bidirectional ventilation. The external pressure referred to herein refers to the atmospheric pressure of the external environment.

Specifically, as shown in fig. 1, the valve body 10 corresponding to the first chamber 101 and the second chamber 102 is further provided with a first normal-air port 10d and a second normal-air port 10b for communicating the inside and the outside, respectively, that is, the first chamber 101 and the second chamber 102 are always communicated with the outside through the first normal-air port 10d and the second normal-air port 10b, and the pressure of the first chamber 101 and the pressure of the second chamber 102 are also the external atmospheric pressure. Assuming that the pressures of the first and second chambers 101 and 102 are P2, the pressure of the middle chamber 103 is P1 (the transmission pressure is P1), the diameters of the large end 202 of the spool and the large chamber 102 of the valve chamber are R2, the diameters of the small end 201 of the spool and the small chamber 101 of the valve chamber are R1, the diameter of the middle section of the spool is R, and the rigidities of the first and second springs 31 and 32 are K1 and K2, respectively, the resultant forces on the left and right sides of the spool are:

when the internal pressure of the transmission case is equal to the external atmospheric pressure, i.e., when P1 is equal to P2, the internal pressure and the external pressure of the transmission case are required to be not communicated, and the vent plug needs to be closed. In fig. 1, both the communication ports are not communicated with the intermediate chamber 103, and the valve body is in a balanced state at this time, that is, F is 0.

Then

When P1 is equal to P2, it is found that:

K₁X₁＝K₂X₂

that is, at the time of design, the relation K can be satisfied₁X₁＝K₂X₂The initial position is the equilibrium state shown in fig. 1, which is obtained when the transmission and the external atmospheric pressure are the same, and in this position, the vent plug remains closed and the transmission is not vented from the inside to the outside.

Referring to fig. 2, fig. 2 is a schematic diagram illustrating the valve core in fig. 1 moving to the right to a critical opening state of the second vent 10 a.

When outside atmospheric pressure is less than the inside atmospheric pressure of gearbox, satisfy P1> P2, because case main aspects 202 sectional area is great, the lifting surface area is great, and the case can right shift under the pressure differential effect, removes behind the certain distance, and the case can reach the equilibrium again, and the volume of right shifting is X when supposing to reach the equilibrium, then the force balance relation as follows:

the above formula yields:

the opening pressure of the vent plug can be controlled by setting the displacement X, the diameters R2 and R1 of the two ends of the valve core and the spring stiffness K1 and K2, and the parameters can be reasonably selected according to the opening pressure.

When the valve core moves to the point A from the point C, the valve core is located at the critical point where the second vent hole 10a is to be opened when the valve core moves to the point X, the valve core continues to move rightwards as shown in FIG. 3, the second vent hole 10a is opened, and the internal air pressure and the external air pressure are communicated; when P1 is equal to P2, the valve core moves leftwards under the action of spring force and returns to the initial position.

Referring to fig. 3, fig. 3 is a schematic diagram illustrating the valve core of fig. 1 moving to the left to the first vent 10c in the critical opening state.

When outside atmospheric pressure is greater than the inside atmospheric pressure of gearbox, satisfy P1< P2, because case main aspects 202 sectional area is great, the lifting surface area is great, and the case can shift to the left under the pressure differential effect, removes behind the certain distance, and the case can reach the equilibrium again, and the volume of shifting to the left when assuming to reach the equilibrium is X, then the force balance relation as follows:

the above formula yields:

similarly, by selecting the displacement X, the diameters R2, R1, and the spring rates K1, K2, the pressure at which the vent plug opens when the pressure in the intermediate chamber 103 is low can be controlled, and these parameters can be selected appropriately according to the magnitude requirements of the low and high opening pressures.

At the critical point shown in fig. 3, the first vent 10c is about to open, the valve core moves to the left, the first vent 10c opens, the external air pressure enters the middle cavity 103 and then enters the transmission, the internal air pressure and the external air pressure are communicated, and when P1 is P2, the valve core moves to the right under the action of the spring force and returns to the initial position.

In the above embodiment, the small chamber 101 and the large chamber 102 on both sides are adjusted by providing the first normal port 10d and the second normal port 10b in the valve body 10, introducing external air pressure into the first chamber 101 and the second chamber 102, and generating a differential pressure by the forces acting on the end walls of the large end 202 and the small end 201 of the valve body and the intermediate chamber 103. Of course, the normal opening may not be provided, the small chamber 101 and the large chamber 102 may have no air pressure, for example, may be vacuum, and the resultant force F received by the valve element at the initial position satisfies the following relation:

it can be set that when P1 is equal to P2, the above relation is equal to 0, when P1 increases, the valve core also moves to the right, when P1 decreases, the valve core moves to the left, after moving to the right or left for a certain distance, the second vent port 10a or the first vent port 10c is opened, P1 is finally equal to P2, and then it returns to the initial position. In addition, the widths of the first vent 10c, the second vent 10a, the large end 202 and the small end 201 are adjusted to ensure that the vacuum of the small cavity 101 and the large cavity 102 is maintained during the left movement or the right movement.

Of course, in this arrangement, the initial position is set depending on the value of P2, and compared with the above-mentioned solution in which the external pressure P2 is introduced into the first chamber 101 and the second chamber 102, the opening pressure of the vent plug is set without considering the value of P2, and only the displacement X, the diameters R2 and R1, and the spring stiffnesses K1 and K2 are selected, so that the vent plug can be applied to any air pressure environment, the setting method is simpler, the versatility is stronger, the pressure control is more reliable, the shape and the size of the intermediate section 203 are not limited, as long as the intermediate chamber 103 is formed, and the vent port can be ensured to be communicated with the intermediate chamber 103 during movement, and the first normal port 10d and the second normal port 10b can also play a role of draining and exhausting water.

It can be understood that, in this embodiment, the stepped cavity structure arrangement of the large cavity and the small cavity, and the large end 202 and the small end 201 of the valve core are arranged to form a cross-sectional area difference, so that when the pressure of the middle cavity 103 changes, the pressure change acting on the two ends of the valve core is different, and the valve core can be acted by the pressure difference force, thereby pushing the valve core to move left or right, so that the first vent hole 10c or the second vent hole 10a positioned at the left and right sides is communicated with the middle cavity 103, thereby opening the vent plug to realize the ventilation of the gearbox. Therefore, the ventilation plug in the scheme can realize bidirectional ventilation, and ventilation can be realized at lower or higher air pressure in the gearbox, so that sealing elements such as oil seals are protected, and the reliability of the gearbox is ensured. Moreover, compare in the plug of ventilating of unidirectional normal close formula, the plug of ventilating that this scheme provided can two-way ventilation, compare in the plug of ventilating of open in usual, the plug of ventilating that this scheme provided can obviously block into the gearbox better, impurity etc. and compare in the ventilative membrane material of polymer among the prior art, the plug of ventilating of this scheme is low to the sensitivity of fluid, the gearbox is at the operation in-process, if the plug of ventilating is infected with fluid, can not block the plug of ventilating, still accessible case removes, discharges fluid from the blow vent.

Referring to fig. 4 in conjunction with fig. 1-3, fig. 4 is a schematic perspective view of the vent plug of fig. 1.

Further, the first normal opening 10d, the second normal opening 10b, the first vent 10c, and the second vent 10a mentioned above can all be disposed at the bottom of the valve body 10, so that when the vent plug is mounted on the transmission case, the vent and the normal opening are both disposed at the bottom and arranged downward, and the external impurities can be reduced or prevented from entering the transmission case through the vent and the normal opening. The bottom is defined by the position of the vent plug after installation to ensure that the vent holes and the normal openings are arranged downwards, and the valve body 10 after installation is horizontally arranged with the view angle of fig. 4, so the vent holes and the normal openings are easily arranged at the bottom, of course, the valve body 10 is not limited to be horizontally arranged, and the vent holes and the normal openings are not limited to be arranged at the bottom, for example, the normal openings can be arranged at the end parts, and the vent holes can be arranged at the periphery parts.

In addition, two ends of the cavity peripheral wall of the valve cavity are respectively matched and limited with the second protruding column 202a of the large end 202 and the first protruding column 201a of the small end 201, the maximum axial displacement of the valve core can be limited by adjusting the lengths of the two protruding columns, and the valve core is prevented from excessively moving to the right or excessively moving to the left, so that the first spring 31 and the second spring 32 are protected, and the system is more stable.

Referring to fig. 5, fig. 5 is a schematic structural diagram of the valve core in fig. 1.

In the above embodiment, the circumferential walls of the large end 202 and the small end 201 of the valve core may further be provided with annular pressure equalizing grooves 201b, 202b, respectively, so as to ensure the movement reliability of the valve core and avoid the clamping stagnation of the valve core and the chamber circumferential wall of the valve chamber.

As shown in fig. 4, the valve body 10 of the vent plug is a square valve body 10, which is easy to process and install. The square valve body 10 specifically comprises a large section and a small section which are connected along the axial direction, and the large cavity and the small cavity are respectively formed by the large section and the small section, the design is simple, the processing is easy, of course, the valve body 10 can be in other shapes, and only the valve cavity is the large cavity and the small cavity.

As shown in fig. 1-4, the portion of the valve body 10 corresponding to the middle cavity 103 may be provided with a jack, the vent plug further includes a connector 50, the connector 50 has an axial through hole, one end of the connector 50 is inserted into the jack, the other end is used for communicating with the transmission case, the middle cavity 103 and the transmission case can be communicated, and one end of the connector 50 inserted into the jack can penetrate out of the jack, so as to further ensure the sealing performance of the insertion, and reduce the possibility of impurities entering. The connector 50 can be screwed in the jack, and the other end can also be screwed in the gearbox, so that the installation is convenient, the disassembly is easy, and the cleaning and maintenance of the interior are convenient. The joint 50 and the vent plug may also be an integral structure, or the vent plug may also be provided without the joint 50, and the middle cavity 103 thereof is provided with a through hole which is directly butted with a vent hole on the gearbox and is sealed at the periphery of the butt joint, which is also a feasible scheme.

As shown in fig. 1-3, the joint 50 and the valve body 10 may be provided with a sealing member 40, and the sealing member 40 may be, for example, a sealing ring, to further ensure the sealing between the vent plug and the outside and prevent impurities or gas from entering the transmission case.

This scheme still provides a gearbox, including the box, the box is equipped with the air vent, and the air vent is installed any above-mentioned embodiment the breather plug, have the same technological effect with above-mentioned embodiment, do not redundantly describe.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that it is obvious to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and these modifications and improvements should also be considered as the protection scope of the present invention.