CN219673234U - Transmission middle shell and transmission assembly - Google Patents

Abstract

The utility model belongs to the technical field of heavy-duty transmissions, and discloses a transmission middle shell and a transmission assembly. The transmission middle shell comprises a middle shell body, an intermediate plate is arranged in a containing cavity of the middle shell body, and a bearing hole is formed in the intermediate plate; four main ribs and a plurality of connecting ribs are arranged on the peripheral surface of the middle shell body in a protruding mode, the two main ribs and the reverse gear idler wheel holes on the middle shell body are arranged coaxially, and the other two main ribs are arranged between the two reverse gear idler wheel holes; the connecting ribs are mutually intersected to form a grid shape, and an included angle B is formed between the connecting ribs and the main rib. According to the utility model, only four main ribs are required to be arranged, and the plurality of connecting ribs are crossed to form a grid shape, so that the torsional strength of the middle shell body is increased, the number of the main ribs and the connecting ribs is greatly reduced while the enough axial reinforcing strength of the middle shell body is ensured, and the weight reduction of the middle shell body of the transmission is realized.

Description

Transmission middle shell and transmission assembly

Technical Field

The utility model relates to the technical field of heavy-duty transmissions, in particular to a transmission middle shell and a transmission assembly.

Background

The automobile transmission is an important part of an automobile transmission system, directly affects the important performances of an automobile such as the dynamic performance, the fuel economy, the comfort, the operability and the reliability of the automobile, and is one of important factors for determining the quality of the automobile. According to the published data, the carbon emission of the traffic industry is improved year by year in recent years, and the ratio of the carbon emission of the passenger car to the carbon emission of the freight car in the whole carbon emission of the traffic industry is 75%, so that the energy structure of the traffic industry needs to be improved, and the carbon reduction and the decarburization of the automobile industry are not delayed. For the weight reduction of the whole vehicle, the weight reduction of a transmission housing with a large weight is of great importance.

The weight reduction of the transmission shell is carried out while the reduction of the quality of the shell material is carried out, meanwhile, the strength, the rigidity, the modal and other static and dynamic performances of the transmission shell are required to be concerned, and if the quality is reduced blindly, the situations of shell fracture, abnormal shaft tooth engagement, bearing failure, excessive vibration noise and the like can be caused, so that the performance and the service life of the transmission assembly are seriously affected.

In order to ensure the static and dynamic performance of the transmission shell, a plurality of mutually parallel axial reinforcing ribs along the axial direction of a transmission gear shaft are additionally arranged outside most of the existing heavy-duty transmission shells, and a plurality of mutually parallel annular reinforcing ribs along the circumferential direction are also arranged at the same time, and the axial reinforcing ribs are vertically intersected with the annular reinforcing ribs. The accommodating cavity of most heavy-duty transmission shells is also internally provided with a middle plate, and a plurality of crossed annular reinforcing ribs and radial reinforcing ribs are additionally arranged around the bearing holes on the middle plate. Most of the ribs, whether the ribs are external to the housing or on the intermediate plate, are grouped to be of equal thickness, equal height, equally spaced and evenly distributed, while improving the reliability, durability and NVH performance of the transmission housing, but also resulting in a significant increase in the weight of the housing.

Disclosure of Invention

The utility model aims to provide a shell and a transmission assembly in a transmission, which are used for solving the problem of heavy weight caused by the influence of a reinforcing rib design on the shell of the transmission assembly.

To achieve the purpose, the utility model adopts the following technical scheme:

a transmission middle housing comprising:

the middle shell body is provided with a containing cavity, an intermediate plate is arranged in the containing cavity, and a bearing hole is formed in the intermediate plate;

four main ribs are arranged on the outer peripheral surface of the middle shell body in a protruding mode, the four main ribs are arranged along the axial direction of the bearing hole and are arranged at intervals around the circumference of the middle shell body, two main ribs are coaxially arranged with the reverse gear idler wheel hole on the middle shell body, and the other two main ribs are arranged between the two reverse gear idler wheel holes;

the outer peripheral surface of the middle shell body is convexly provided with a plurality of connecting ribs, a plurality of connecting ribs are arranged between any two main ribs, a plurality of connecting ribs are mutually intersected to form a grid shape, an included angle B is formed between the connecting ribs and the main ribs, and the included angle B is larger than 0 degrees and smaller than 90 degrees.

Optionally, the protruding height of the main rib is higher than the protruding height of the connecting rib.

Optionally, the plurality of connecting ribs form a plurality of grid units, the plurality of grid units form a first grid density area and a second grid density area, the density of the first grid density area is greater than that of the second grid density area, and the position of the first grid density area is correspondingly arranged with the positions of the middle shafts of the two main boxes in the middle shell body.

Optionally, the thickness of the connecting ribs in the first grid density region is greater than the thickness of the connecting ribs in the second grid density region.

Optionally, the size of each of the plurality of grid cells is between 20mm and 60 mm.

Optionally, the both ends of well casing body divide and are equipped with the flange, the flange is protruding to be located the outer peripheral face of well casing body, the outer peripheral face of flange is protruding to be equipped with annular muscle and bolt hole, the bolt hole runs through well casing body the flange with annular muscle sets up, a plurality of in the connecting rod with the position that the bolt hole is just right is equipped with the assembly and dodges the district.

Optionally, the long axis direction of the bolt hole has a first outer diameter section and a second outer diameter section, the first outer diameter section deviates from the front end setting of well casing body, the external diameter of first outer diameter section is greater than the external diameter of second outer diameter section.

Optionally, the intermediate plate includes the intermediate plate body, follow on the intermediate plate body the preceding terminal surface of the axis direction of bearing hole is equipped with the boss, the boss is around the circumference setting of bearing hole.

Optionally, the bearing hole comprises a main shaft bearing hole and a main box intermediate shaft bearing hole, radial ribs are arranged between the boss of the main shaft bearing hole and the main box intermediate shaft bearing hole and the inner wall of the middle shell body, and the radial ribs are convexly arranged on the front end face of the intermediate plate body.

The transmission assembly comprises the transmission middle shell, and two ends of the transmission middle shell are respectively connected with the transmission front shell and the transmission rear shell to form a box body.

The utility model has the beneficial effects that:

the transmission middle shell has the advantages that the number of the main ribs is four, two main ribs are coaxially arranged with the reverse gear idler wheel holes, and compared with a plurality of main ribs uniformly distributed in the prior art, the transmission middle shell has enough axial enhancement strength, meanwhile, the number of the main ribs is greatly reduced, and the weight reduction of the transmission middle shell is facilitated; the connecting ribs between the main ribs and the main ribs form an included angle B, and the plurality of connecting ribs are crossed to form a grid shape, so that the torsional strength of the middle shell body is increased, and the overall strength of the middle shell of the transmission is improved. According to the transmission middle shell, the number and arrangement form of the main ribs and the connecting ribs on the outer peripheral surface of the middle shell body are optimized according to the topological optimization design method, and the weight reduction is realized on the premise of ensuring enough strength.

The transmission assembly comprises a transmission middle shell body which is in topological optimization design, and two ends of the transmission middle shell body are respectively connected with a transmission front shell body and a transmission rear shell body to form a box body, so that the box body is light in weight, and further the light weight of the transmission assembly is facilitated.

Drawings

FIG. 1 is a schematic structural view of a housing in a transmission of the present utility model;

FIG. 2 is an enlarged schematic view of the area A in FIG. 1;

FIG. 3 is a schematic view of the rear end face of the housing in the transmission of the present utility model;

fig. 4 is a schematic view of the structure of the front end face of the case in the transmission of the present utility model.

In the figure:

1. a middle housing body; 11. reverse idler wheel holes; 12. a main rib; 13. a connecting rib; 131. assembling an avoidance area; 14. a flange; 15. annular ribs; 16. bolt holes; 161. a first outer diameter section; 162. a second outer diameter section;

2. an intermediate plate; 20. an intermediate plate body; 21. a bearing hole; 211. a spindle bearing hole; 212. a main box intermediate shaft bearing hole; 22. a boss; 23. radial ribs.

Detailed Description

The utility model is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the utility model and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present utility model are shown in the drawings.

In the description of the present utility model, unless explicitly stated and limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present utility model will be understood in specific cases by those of ordinary skill in the art.

In the present utility model, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "left", "right", and the like are orientation or positional relationships based on those shown in the drawings, merely for convenience of description and simplicity of operation, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the utility model. Furthermore, the terms "first," "second," and the like, are used merely for distinguishing between descriptions and not for distinguishing between them.

The utility model provides a transmission middle shell which is suitable for a heavy double-intermediate shaft type transmission, wherein two ends of the transmission middle shell are respectively connected with a transmission front shell and a transmission rear shell to form a box body, and the box body is used for forming a transmission assembly.

As shown in fig. 1-4, the transmission middle shell comprises a middle shell body 1, wherein the middle shell body 1 is provided with a containing cavity, an intermediate plate 2 is arranged in the containing cavity, and a bearing hole 21 is formed in the intermediate plate 2; four main ribs 12 are arranged on the outer peripheral surface of the middle shell body 1 in a protruding mode, the four main ribs 12 are arranged along the axial direction of the bearing hole 21 and are arranged at intervals around the circumference of the middle shell body 1, two main ribs 12 are arranged coaxially with the reverse gear idler wheel hole 11 on the middle shell body 1, and the other two main ribs 12 are arranged between the two reverse gear idler wheel holes 11; the outer peripheral surface of the middle shell body 1 is convexly provided with a plurality of connecting ribs 13, the plurality of connecting ribs 13 are arranged between any two main ribs 12, the plurality of connecting ribs 13 are mutually crossed to form a grid shape, an included angle B is formed between the connecting ribs 13 and the main ribs 12, and the included angle B is larger than 0 degree and smaller than 90 degrees.

In the transmission middle shell, four main ribs 12 are arranged, two main ribs 12 are coaxially arranged with a reverse gear idler wheel hole 11, and compared with a plurality of main ribs 12 uniformly distributed in the prior art, the transmission middle shell has the advantages that the number of the main ribs 12 is greatly reduced while the enough axial enhancement strength of the middle shell body 1 is ensured, and the weight reduction of the transmission middle shell is facilitated; the connecting ribs 13 between the main ribs 12 and the main ribs 12 form an included angle B, and the plurality of connecting ribs 13 are crossed to form a grid shape, so that the torsional strength of the middle shell body 1 is increased, and the overall strength of the shell in the transmission is improved. According to the transmission middle shell, the number and arrangement forms of the main ribs 12 and the connecting ribs 13 on the outer peripheral surface of the middle shell body 1 are optimized according to the topological optimization design method, the main ribs 12 are reduced, the connecting ribs 13 are added, the surface torsion deformation resistance of the middle shell body 1 can be fully improved, the torsion rigidity of the transmission middle shell is effectively improved, and the weight is reduced on the premise that enough strength and rigidity are ensured.

In this embodiment, the two main ribs 12 are disposed coaxially with the reverse gear idler hole 11, which means that the projection of the axis of the reverse gear idler hole 11 and the projection of the axis of the protruding height of the main rib 12 coincide in the axial direction along the bearing hole 21. One end of the main rib 12 is connected to the outer wall of the reverse gear idler wheel hole 11, and the main rib 12 is arranged near the reverse gear shaft, so that the rigidity and strength of the structure near the larger opening on the upper surface of the middle shell body 1 can be improved through the main rib 12, and meanwhile the strength and rigidity of the middle shell body 1 under the reverse gear working condition can be guaranteed.

Alternatively, the protruding height of the main rib 12 is higher than the protruding height of the connecting rib 13.

As shown in fig. 1, the grid-shaped connecting ribs 13 are arranged between the main ribs 12, the connecting ribs 13 are distributed in an X-cross manner and have a certain included angle B with the main ribs 12, and the protruding height of the connecting ribs 13 is lower than that of the main ribs 12, so that the material consumption of the connecting ribs 13 is reduced, and the overall weight is reduced. The connecting ribs 13 can play a role in enhancing the torsion resistance of the root of the main rib 12 and the surface of the middle shell body 1, so that the main rib 12 and the connecting ribs 13 jointly act to improve the static and dynamic performances such as strength, rigidity, mode and the like of the middle shell body 1.

In this embodiment, the number, height, arrangement position and direction of the main ribs 12 and the connecting ribs 13 are all set according to the material optimal distribution result obtained by topology optimization. The specific method comprises the following steps: according to the density cloud chart of the topology optimization result, the distribution trend and rule of the high-density area are analyzed, the main ribs 12 and the connecting ribs 13 are arranged along the high-density area, the influence of the distribution rule of the main ribs 12 and the connecting ribs 13 on the casting, machining and assembly of the shell in the transmission is mainly considered when the main ribs 12 and the connecting ribs 13 are arranged, and enough spanner space is reserved for bolt assembly. By reasonably arranging materials, the effect of meeting the requirements of reliable durability and NVH performance with minimum mass is achieved, and the weight reduction of the shell in the transmission is realized.

Optionally, the plurality of connection ribs 13 form a plurality of grid cells, the plurality of grid cells form a first grid density region and a second grid density region, the density of the first grid density region is greater than that of the second grid density region, and the position of the first grid density region is correspondingly arranged with the positions of the intermediate shafts of the two main boxes in the middle shell body 1.

Referring to fig. 3, in this embodiment, the intermediate plate 2 includes an intermediate plate body 20, and five bearing holes 21 are formed in the intermediate plate body 20, which is suitable for a heavy-duty dual intermediate shaft type transmission. The two main box intermediate shafts are symmetrically arranged on two sides of the main shaft, the main box intermediate shaft is closer to the middle shell body 1, in order to ensure the meshing reliability of the main box gears, the rigidity of the middle shell body 1 near the main box intermediate shaft is required to be ensured, therefore, connecting ribs 13 with higher density are additionally arranged on the outer peripheral surface of the middle shell body 1 corresponding to the main box intermediate shaft, the density of the connecting ribs 13 at other positions is relatively sparse, and the arrangement form can enable the middle shell body 1 to resist bending torsion deformation to the greatest extent, so that the requirements of reliability, durability and NVH performance are met under the condition that the weight of the middle shell body of the transmission is lightest.

Further, the thickness of the connecting ribs 13 in the first grid density region is greater than the thickness of the connecting ribs 13 in the second grid density region.

As shown in fig. 1, the connecting ribs 13 at different positions on the surface of the middle housing body 1 are designed in a sparse and dense manner, and compared with the arrangement form of the connecting ribs 13 which are uniform and uniform in the prior art, the embodiment is favorable for obtaining the light design requirement by optimizing the arrangement mode by adopting a smaller number of connecting ribs 13. In order to ensure the optimal casting quality, the specific spacing and thickness of the plurality of connecting ribs 13 are designed according to the transmission position and direction of each gear of the intermediate shaft of the main gearbox. The spacing between the connection ribs 13, i.e. the size of the plurality of grid cells, is between 20mm and 60mm, while the thickness of the connection ribs 13 is designed to be distributed between 6 and 6.5 mm.

Optionally, flanges 14 are respectively arranged at two ends of the middle shell body 1, the flanges 14 are convexly arranged on the outer peripheral surface of the middle shell body 1, annular ribs 15 and bolt holes 16 are convexly arranged on the outer peripheral surface of the flanges 14, the bolt holes 16 penetrate through the middle shell body 1, the flanges 14 and the annular ribs 15, and an assembly avoidance area 131 is arranged at a position, which is opposite to the bolt holes 16, of the plurality of connecting ribs 13.

As shown in fig. 1 and 2, flanges 14 are provided at both ends of the middle case body 1 for connecting the transmission front case and the transmission rear case, respectively, in such a manner that detachable connection is achieved by connecting bolts on the bolt holes 16. The provision of the flange 14 is advantageous in increasing the connection strength of the two ends of the middle housing body 1. The annular ribs 15 are arranged on the outer peripheral surface of the flange 14 in a protruding manner, so that the connection strength of the two ends of the middle housing body 1 is further improved, and the connection tightness of the middle housing body 1 with the front housing and the rear housing of the transmission is improved. The external diameter of bolt hole 16 runs through in the radial direction casing body 1, flange 14 and cyclic annular muscle 15 setting, do benefit to the joint strength that increases bolt hole 16 department, and be located near bolt hole 16 in connecting muscle 13, for the needs of machining and assembly, the protruding height of connecting muscle 13 is less than other positions, specifically, in the regional in the direction of leading end from casing body 1, the protruding height of connecting muscle 13 reduces, be convenient for bolt hole 16 department assembly bolt, assembly dodges district 131 and is the spanner space.

Alternatively, the bolt hole 16 has a first outer diameter section 161 and a second outer diameter section 162 in the long axis direction, the first outer diameter section 161 being disposed away from the front end of the middle housing body 1, the first outer diameter section 161 having an outer diameter larger than that of the second outer diameter section 162.

As shown in fig. 1 and 2, the bolt hole 16 on the flange 14 at the front end of the middle housing body 1 is provided with a sectional outer diameter, wherein the bolt hole 16 at the side away from the front end surface has a first outer diameter section 161 with a larger outer diameter, and the end surface of the first outer diameter section 161 can have more contact area with the end surface of the bolt, and meanwhile, the weight of the middle housing body 1 can be reduced on the premise of meeting the length requirement of the bolt. As shown in fig. 2, the outer walls of the first outer diameter section 161 and the second outer diameter section 162 are respectively connected to two annular ribs 15 on the flange 14, so that the strength and rigidity of the bolt hole 16 are enhanced by the annular ribs 15.

Alternatively, the intermediate plate 2 includes an intermediate plate body 20, and a boss 22 is provided on the intermediate plate body 20 along the front end face in the axial direction of the bearing hole 21, the boss 22 being provided around the circumference of the bearing hole 21.

As shown in fig. 3 and 4, bosses 22 are provided around the five bearing holes 21 of the rear end face, and no boss 22 is provided on the front end face. According to the radial force and the axial force transmitted to the bearing hole 21 by meshing the internal gear of the accommodating cavity of the middle shell body 1, a topology optimization method is adopted, and the boss 22 is coaxially arranged on one side of the bearing hole 21, so that the structural strength and the rigidity of the middle plate body 20 can be ensured, and the reliability of bearing and gear transmission is further ensured. The boss 22 is only arranged on the rear end face of the middle plate body 20, so that the arrangement of the boss 22 on the front end face is saved, the total weight of the middle plate 2 is reduced as a whole, and the light weight is facilitated.

Alternatively, the bearing hole 21 includes a main shaft bearing hole 211 and a main casing intermediate shaft bearing hole 212, and radial ribs 23 are provided between the bosses 22 of the main shaft bearing hole 211 and the main casing intermediate shaft bearing hole 212 and the inner wall of the middle casing body 1, the radial ribs 23 being provided protruding from the front end surface of the intermediate plate body 20.

As shown in fig. 3 and 4, the front end surface of the intermediate plate body 20 is provided with radial ribs 23, and the rear end surface is not provided with radial ribs 23, so that compared with the prior art, the use of radial ribs 23 is reduced, and the weight reduction is facilitated. Meanwhile, in order to ensure the reinforcing effect of the radial rib 23, the radial rib 23 is convexly arranged on the front end surface of the middle plate body 20, two ends of the radial rib 23 are respectively connected with the boss 22 and the middle housing body 1, and as shown in fig. 1, the radial rib 23 extends to the edge of the inner wall of the middle housing body 1 towards the rear end on the inner wall of the middle housing body 1 so as to increase the contact with the inner wall of the middle housing body 1, thereby being beneficial to enhancing the structural strength and rigidity of the middle plate body 20 and further ensuring the transmission reliability of the transmission.

The transmission assembly provided by the embodiment of the utility model comprises the transmission middle shell which is in topological optimization design, wherein the two ends of the transmission middle shell are respectively connected with the transmission front shell and the transmission rear shell to form the box body, and the box body is light-weighted through the light-weighted design of the transmission middle shell, so that the light-weighted transmission assembly is facilitated.

It is to be understood that the above examples of the present utility model are provided for clarity of illustration only and are not limiting of the embodiments of the present utility model. Various obvious changes, rearrangements and substitutions can be made by those skilled in the art without departing from the scope of the utility model. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the utility model are desired to be protected by the following claims.

Claims (10)

1. A transmission middle housing, comprising:

the middle shell comprises a middle shell body (1), wherein the middle shell body (1) is provided with a containing cavity, a middle plate (2) is arranged in the containing cavity, and a bearing hole (21) is formed in the middle plate (2);

four main ribs (12) are convexly arranged on the outer peripheral surface of the middle shell body (1), the four main ribs (12) are arranged along the axial direction of the bearing hole (21) and are arranged around the circumference of the middle shell body (1) at intervals, two main ribs (12) are coaxially arranged with a reverse gear idler wheel hole (11) on the middle shell body (1), and the other two main ribs (12) are arranged between the two reverse gear idler wheel holes (11);

the outer peripheral surface of the middle shell body (1) is convexly provided with a plurality of connecting ribs (13), the connecting ribs (13) are arranged between any two main ribs (12), the connecting ribs (13) are mutually intersected to form a grid shape, an included angle B is formed between the connecting ribs (13) and the main ribs (12), and the included angle B is larger than 0 degree and smaller than 90 degrees.

2. A transmission casing according to claim 1, wherein the protruding height of the main rib (12) is higher than the protruding height of the connecting rib (13).

3. The transmission middle housing according to claim 1, wherein a plurality of the connection ribs (13) form a plurality of grid cells, a plurality of the grid cells form a first grid density region and a second grid density region, the density of the first grid density region is greater than that of the second grid density region, and the position of the first grid density region is arranged corresponding to the position of the intermediate shafts of the two main tanks in the middle housing body (1).

4. A transmission casing according to claim 3, wherein the thickness of the connection ribs (13) in the first grid density zone is greater than the thickness of the connection ribs (13) in the second grid density zone.

5. A transmission casing according to claim 3 wherein each of a plurality of said grid cells is between 20mm and 60mm in size.

6. The transmission middle housing according to claim 1, wherein flanges (14) are respectively arranged at two ends of the middle housing body (1), the flanges (14) are convexly arranged on the outer circumferential surface of the middle housing body (1), annular ribs (15) and bolt holes (16) are convexly arranged on the outer circumferential surface of the flanges (14), the bolt holes (16) penetrate through the middle housing body (1), the flanges (14) and the annular ribs (15), and assembly avoidance areas (131) are arranged at positions, opposite to the bolt holes (16), of the connecting ribs (13).

7. The transmission middle housing according to claim 6, wherein the bolt hole (16) has a first outer diameter section (161) and a second outer diameter section (162) in a long axis direction, the first outer diameter section (161) is disposed away from a front end of the middle housing body (1), and an outer diameter of the first outer diameter section (161) is larger than an outer diameter of the second outer diameter section (162).

8. A transmission intermediate housing as claimed in any one of claims 1 to 7, wherein the intermediate plate (2) comprises an intermediate plate body (20), a boss (22) being provided on the intermediate plate body (20) along a front end face in an axial direction of the bearing hole (21), the boss (22) being provided around a circumference of the bearing hole (21).

9. The transmission middle housing according to claim 8, wherein the bearing hole (21) comprises a main shaft bearing hole (211) and a main box intermediate shaft bearing hole (212), radial ribs (23) are arranged between the boss (22) of the main shaft bearing hole (211) and the main box intermediate shaft bearing hole (212) and the inner wall of the middle housing body (1), and the radial ribs (23) are convexly arranged on the front end face of the intermediate plate body (20).

10. A transmission assembly comprising a transmission intermediate housing as claimed in any one of claims 1 to 9, wherein the transmission intermediate housing is connected at both ends to a transmission front housing and a transmission rear housing respectively to form a case.