CN115698508A

CN115698508A - Rotary compressor

Info

Publication number: CN115698508A
Application number: CN202080102123.XA
Authority: CN
Inventors: 山田博之
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2020-06-22
Filing date: 2020-06-22
Publication date: 2023-02-03
Anticipated expiration: 2040-06-22
Also published as: CN115698508B; WO2021260759A1; JPWO2021260759A1; JP7313560B2

Abstract

The rotary compressor of the present disclosure includes: a cylinder block formed with a cylinder chamber; a rotary piston that performs eccentric rotary motion in the cylinder chamber; a vane having a first end portion contacting an outer circumferential surface of the rotary piston to partition the cylinder chamber; and a spring that is housed in a spring housing chamber and presses a second end portion that is an end portion of the vane opposite to the first end portion toward the rotary piston, wherein the cylinder block is formed with a vane groove that communicates with the cylinder chamber and the spring housing chamber and slidably holds the vane, wherein at least one of a surface of the vane that faces the vane groove and a surface of the vane groove that faces the vane is formed with a first groove in which an internal pressure increases when the vane advances to protrude into the cylinder chamber, and wherein the cylinder block is formed with a second groove in which one end communicates with the first groove and the other end communicates with the spring housing chamber.

Description

Rotary compressor

Technical Field

The present disclosure relates to a rotary compressor in which a cylinder chamber formed in a cylinder block is partitioned into a suction chamber and a compression chamber by a vane.

Background

One of refrigerant compressors mounted in air conditioners, refrigeration equipment, and the like is a rotary compressor. A compression mechanism of a rotary compressor includes a cylinder, a rotary piston, a vane, and a spring. The cylinder block is formed with a substantially cylindrical cylinder chamber. Further, the cylinder block is formed with a vane groove having one end communicating with the cylinder chamber and the other end communicating with a spring housing chamber housing a spring. The rotary piston is housed in a cylinder chamber of the cylinder block. The rotary piston is attached to an eccentric portion of the drive shaft. Thus, when the drive shaft rotates, the rotary piston performs an eccentric rotary motion in the cylinder chamber.

The vane is slidably held in a vane groove of the cylinder. Further, the first end of the vane is in contact with the outer peripheral surface of the rotary piston. The vane slides in the vane groove following the rotary piston that eccentrically rotates in the cylinder chamber, and the second end portion, which is the end portion on the opposite side of the first end portion, of the vane is pressed toward the rotary piston by a spring in order to suppress the first end portion of the vane from separating from the outer peripheral surface of the rotary piston. Thereby, the cylinder chamber is partitioned into a suction chamber and a compression chamber by the vane. In other words, a space surrounded by the inner peripheral surface of the cylinder chamber and the outer peripheral surface of the rotary piston is partitioned into a suction chamber and a compression chamber by the vane. Further, since the rotary piston eccentrically moves in the cylinder chamber by the rotation of the drive shaft, the rotary compressor simultaneously sucks the refrigerant into the suction chamber and compresses the refrigerant in the compression chamber.

Here, when the rotary piston approaches the vane groove, the vane is pushed by the rotary piston, slides in the vane groove, and is accommodated in the vane groove. Therefore, when the vane is retracted into the cylinder chamber, the first end of the vane does not move away from the outer peripheral surface of the rotary piston.

On the other hand, when the rotary piston is separated from the vane groove, the vane is pushed out into the cylinder chamber while sliding in the vane groove by a force that is pushed toward the rotary piston side by the spring. Thus, when the vane advances to protrude into the cylinder chamber, the first end of the vane can be prevented from separating from the outer peripheral surface of the rotary piston. Therefore, if the frictional force between the vane and the vane groove is large, the vane cannot follow the rotary piston when the vane moves forward, and the first end portion of the vane may be separated from the vane distant from the outer peripheral surface of the rotary piston. When the vane separation occurs, noise occurs when the first end of the vane comes into contact with the outer peripheral surface of the rotary piston again, and the performance of the rotary compressor is reduced due to communication between the suction chamber and the compression chamber.

Therefore, among conventional rotary compressors, a rotary compressor that reduces the frictional force between the vane and the vane groove has been proposed (see patent document 1). Specifically, in the rotary compressor described in patent document 1, a fine concave portion is formed on a sliding surface between the vane and the vane groove or a sliding surface between the vane groove and the vane, and a friction force between the vane and the vane groove is reduced.

Prior art documents

Patent literature

Patent document 1: international publication No. 2013-005394

Disclosure of Invention

Problems to be solved by the invention

When the rotary compressor is used, metal powder is generated due to friction between the vane and the vane groove. In the rotary compressor, a sliding portion is also present at a portion other than between the vane and the vane groove. When the rotary compressor is used, metal powder is generated from sliding portions other than between the vane and the vane groove. In the rotary compressor, a product generated by a reaction between the refrigerant and the refrigerating machine oil is also generated. Therefore, in the conventional rotary compressor in which the frictional force between the vane and the vane groove is reduced, if the rotary compressor is used for a long period of time, the metal powder and the product intrude between the vane and the vane groove and are deposited in the fine concave portion formed in the vane or the vane groove. As a result, in the conventional rotary compressor in which the reduction of the frictional force between the blades and the blade grooves is achieved, there is a problem that the reduction effect of the frictional force between the blades and the blade grooves is reduced and the blades are separated when the rotary compressor is used for a long period of time.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a rotary compressor capable of suppressing blade separation for a longer period of time than in the related art.

Means for solving the problems

The rotary compressor of the present disclosure includes: a cylinder block formed with a cylinder chamber; a rotary piston that is housed in the cylinder chamber and performs eccentric rotary motion in the cylinder chamber; a vane having a first end portion contacting an outer circumferential surface of the rotary piston, the vane dividing the cylinder chamber into a suction chamber and a compression chamber; and a spring that is housed in a spring housing chamber and presses a second end portion that is an end portion of the vane opposite to the first end portion toward the rotary piston, wherein the cylinder is formed with a vane groove having one end that communicates with the cylinder chamber and the other end that communicates with the spring housing chamber, and the vane is slidably held in the vane groove, wherein at least one first groove in which an internal pressure increases when the vane advances to protrude into the cylinder chamber is formed in at least one of a surface of the vane that faces the vane groove and a surface of the vane groove that faces the vane, and at least one second groove having one end that communicates with the first groove and the other end that communicates with the spring housing chamber is formed.

Effects of the invention

In the rotary compressor of the present disclosure, when the vane moves forward, the pressure increased in the first groove can suppress contact between the vane and the vane groove, and the frictional force between the vane and the vane groove can be reduced. In the rotary compressor of the present disclosure, the second groove can discharge the metal powder and the product that have entered between the vane and the vane groove from between the vane and the vane groove. Therefore, in the rotary compressor of the present disclosure, the deposition of metal powder and products that have intruded between the vane and the vane groove in the first groove can be suppressed. Therefore, the rotary compressor of the present disclosure can suppress the blade separation for a longer period of time than in the related art.

Drawings

Fig. 1 is a longitudinal sectional view showing a rotary compressor according to embodiment 1.

Fig. 2 is a plan view for explaining a compression mechanism of the rotary compressor according to embodiment 1.

Fig. 3 is a first side view of the vane of the rotary compressor according to embodiment 1.

Fig. 4 isbase:Sub>A sectional viewbase:Sub>A-base:Sub>A of fig. 3.

Fig. 5 is a diagram for explaining an operation when the vane of the rotary compressor according to embodiment 1 moves forward.

Fig. 6 is a diagram for explaining the operation of the rotary compressor according to embodiment 1 when the blades retract.

Fig. 7 is a plan view for explaining a compression mechanism of the rotary compressor according to embodiment 2.

Fig. 8 is a plan view for explaining a compression mechanism of the rotary compressor according to embodiment 2.

Fig. 9 is a first side view of the vane of the rotary compressor according to embodiment 2.

Fig. 10 is a view of the vane of the rotary compressor according to embodiment 2 as viewed from the second side.

Fig. 11 is a plan view showing an example of a vane of the rotary compressor according to embodiment 2.

Fig. 12 is a view of the vane of the rotary compressor according to embodiment 3 as viewed from the first side.

Fig. 13 is a sectional view taken along line B-B of fig. 12.

Fig. 14 is a first side view of an example of the vane of the rotary compressor according to embodiment 4.

Fig. 15 is a view of an example of the vane of the rotary compressor according to embodiment 4 as viewed from the first side.

Fig. 16 is a first side view of an example of the vane of the rotary compressor according to embodiment 4.

Fig. 17 is a view of an example of the vane of the rotary compressor according to embodiment 4 as viewed from the first side.

Fig. 18 is a view of an example of the vane of the rotary compressor according to embodiment 4 as viewed from the first side.

Fig. 19 is a view of an example of the vane of the rotary compressor according to embodiment 4 as viewed from the first side.

Fig. 20 is a view of the vane of the rotary compressor according to embodiment 5 as viewed from the first side.

Fig. 21 is a cross-sectional view C-C of fig. 20.

Fig. 22 is a first side view of another example of the vane of the rotary compressor according to embodiment 5.

Detailed Description

Embodiment 1.

Fig. 1 is a longitudinal sectional view showing a rotary compressor according to embodiment 1. Fig. 2 is a plan view for explaining a compression mechanism of the rotary compressor according to embodiment 1. Fig. 2 is a view of the compression mechanism 20 with the upper bearing 31, described later, removed from the top to facilitate the internal structure of the decompression mechanism 20.

The rotary compressor 100 according to embodiment 1 includes a motor 10, a compression mechanism 20, and a drive shaft 60. The drive shaft 60 connects the motor 10 and the compression mechanism 20. The rotary compressor 100 according to embodiment 1 includes a sealed container 1. The motor 10, the compression mechanism 20, and the drive shaft 60 are housed in the closed casing 1. Further, refrigerating machine oil for lubricating sliding portions of the compression mechanism 20 and the like is stored in a lower portion of the closed casing 1.

The motor 10 includes a stator 11 fixed to the sealed container 1 and a rotor 12 rotated by a magnetic force generated by the stator 11.

The drive shaft 60 is connected to the rotor 12 of the motor 10 and the compression mechanism 20, and transmits the driving force of the motor 10 to the compression mechanism 20. The drive shaft 60 includes a main shaft portion 61 and an eccentric portion 62 provided at a middle portion of the main shaft portion 61. The main shaft portion 61 and the eccentric portion 62 are each cylindrical. The central axis of the eccentric portion 62 is eccentric with respect to the central axis of the main shaft portion 61. That is, when the main shaft portion 61 rotates, the eccentric portion 62 eccentrically rotates. The main shaft portion 61 is fixed to the rotor 12 of the motor 10. A cylindrical rotary piston 30 is slidably attached to an outer peripheral portion of the eccentric portion 62. The rotary piston 30 is a component of the compression mechanism 20.

The compression mechanism 20 compresses the low-pressure refrigerant sucked into the compression mechanism 20 by the driving force of the motor 10 transmitted from the drive shaft 60, and discharges the high-pressure refrigerant into the sealed container 1. The compression mechanism 20 includes a cylinder 21, a rotary piston 30, a vane 40, an upper bearing 31, a lower bearing 32, and a spring 34.

The cylinder block 21 has a cylindrical cylinder chamber 22 formed therein. The cylinder chamber 22 is partitioned into a suction chamber 23 and a compression chamber 24 by a vane 40. The central axis of the cylinder chamber 22 is arranged on the same axis as the central axis of the main shaft portion 61 of the drive shaft 60. In addition, a rotary piston 30 is housed in the cylinder chamber 22. Therefore, by rotating the drive shaft 60, the eccentric portion 62 and the rotary piston 30 are eccentrically rotated with respect to the central axis of the cylinder chamber 22 in the cylinder chamber 22. Further, an upper opening portion of the cylinder chamber 22 is closed by the upper bearing portion 31. The lower opening of the cylinder chamber 22 is closed by the lower bearing portion 32. The upper bearing 31 and the lower bearing 32 rotatably support the main shaft 61 of the drive shaft 60.

The cylinder 21 has a vane groove 27 formed along a radial direction of the cylinder 21. One end of the vane groove 27 communicates with the cylinder chamber 22. The other end of the vane groove 27 communicates with a spring housing chamber 33 housing a spring 34. The vane 40 is slidably held in the vane groove 27. In embodiment 1, the spring housing chamber 33 is formed in the cylinder 21. However, the spring housing chamber 33 may be formed outside the cylinder 21, such as between the cylinder 21 and the sealed container 1.

The spring 34 accommodated in the spring accommodating chamber 33 urges the second end 42 of the vane 40 toward the rotary piston 30. Thus, even if the eccentric portion 62 and the rotary piston 30 perform eccentric rotary motion in the cylinder chamber 22, the first end portion 41, which is the end portion of the vane 40 opposite to the second end portion 42, can be brought into contact with the outer peripheral surface of the rotary piston 30. That is, even if the eccentric portion 62 and the rotary piston 30 perform eccentric rotary motion in the cylinder chamber 22, the cylinder chamber 22 can be divided into the suction chamber 23 and the compression chamber 24 by the vane 40. In other words, even if the eccentric portion 62 and the rotary piston 30 perform eccentric rotational motion in the cylinder chamber 22, the space surrounded by the inner peripheral surface of the cylinder chamber 22 and the outer peripheral surface of the rotary piston can be partitioned into the suction chamber 23 and the compression chamber 24 by the vane 40.

In the following, an opposing surface of the vane 40 that faces the vane groove 27 and is on the compression chamber 24 side is referred to as a first side surface 43. Of the surfaces of the vane 40 facing the vane groove 27, the surface facing the suction chamber 23 is the second side surface 44. That is, the first side surface 43 and the second side surface 44 are surfaces of the blade 40 facing the blade groove 27. Of the surfaces of the vane groove 27 facing the vanes 40, the surface facing the compression chamber 24 is the first wall surface 28. Of the surfaces of the vane groove 27 facing the vane 40, the surface facing the suction chamber 23 is the second wall surface 29. That is, the first wall surface 28 and the second wall surface 29 are surfaces of the vane groove 27 facing the vane 40.

Further, the cylinder 21 is formed with a suction port 25 communicating with the suction chamber 23. One end of the suction pipe 2 is connected to the suction port 25. The other end of the suction pipe 2 is connected to a suction muffler 101. Further, the cylinder 21 is formed with a discharge port 26 communicating with the compression chamber 24. The discharge port 26 also communicates with the inside of the sealed container 1 through a discharge port, not shown, formed in the upper bearing portion 31.

When the rotor 12 of the motor 10 rotates, the drive shaft 60 connected to the rotor 12 also rotates. As a result, the eccentric portion 62 of the drive shaft 60 and the rotary piston 30 attached to the eccentric portion 62 perform eccentric rotational motion with respect to the central axis of the cylinder chamber 22 in the cylinder chamber 22. When the rotary piston 30 performs eccentric rotary motion in the cylinder 21, the volume of the suction chamber 23 is expanded. As a result, the low-pressure refrigerant flows from the outside of rotary compressor 100 into suction chamber 23 through suction muffler 101, suction pipe 2, and suction port 25. When the rotary piston 30 further performs eccentric rotational movement in the cylinder 21, the suction chamber 23 and the suction port 25 no longer communicate. At this time, the space originally in the suction chamber 23 becomes the compression chamber 24.

On the other hand, when the rotary piston 30 performs eccentric rotary motion in the cylinder 21, the volume of the compression chamber 24 is reduced. Thereby, the refrigerant in the compression chamber 24 is compressed into a high-pressure refrigerant, and is discharged into the sealed container 1 through the discharge port 26 and the discharge port, not shown, of the upper bearing 31. The high-pressure refrigerant discharged into the sealed container 1 flows out of the rotary compressor 100 through the discharge pipe 3 communicating with the inside of the sealed container 1. When the rotary piston 30 further performs eccentric rotary motion in the cylinder 21, the compression chamber 24 and the discharge port 26 are no longer communicated. At this time, the space originally in the compression chamber 24 becomes the suction chamber 23.

During driving of the rotary compressor 100, the vane 40 repeats a forward movement of projecting into the cylinder chamber 22 while sliding in the vane groove 27 and a backward movement of housing in the vane groove 27 while sliding in the vane groove 27. Specifically, when the rotary piston 30 is separated from the vane groove 27, the vane 40 moves forward by the force of the spring 34 pressing the rotary piston 30. When the rotary piston 30 approaches the vane groove 27, the vane 40 is pushed by the rotary piston 30 and retreats. During driving of the rotary compressor 100, the refrigerating machine oil stored in the lower portion of the sealed container 1 is supplied between the vane 40 and the vane groove 27 through an oil supply path not shown.

In a conventional general rotary compressor, the surface of the vane facing the vane groove is a flat surface. In addition, in a conventional general rotary compressor, the surface of the vane groove facing the vane is also a flat surface. In such a conventional general rotary compressor, when the rotary compressor 100 is driven, the frictional force between the vane and the vane groove increases due to the contact between the vane and the vane groove, and the vane having the first end portion of the vane separated from the outer peripheral surface of the rotary piston may be separated. Specifically, when the vane retreats, the vane is pressed by the rotary piston 30, and therefore, the vane separation does not occur. On the other hand, when the vane moves forward due to the pressing pressure of the spring, if the frictional force between the vane and the vane groove is large, the vane cannot follow the rotary piston, and the vane is separated.

Therefore, in the rotary compressor 100 according to embodiment 1, the blades 40 are configured as follows in order to suppress the occurrence of blade separation when the blades 40 advance.

Fig. 3 is a view of the vane of the rotary compressor according to embodiment 1 as viewed from the first side.

Fig. 4 isbase:Sub>A sectional viewbase:Sub>A-base:Sub>A of fig. 3.

In the blade 40 of embodiment 1, the first side surface 43 and the second side surface 44 which are surfaces facing the blade groove 27 are substantially flat surfaces. However, unlike the conventional general rotary compressor blade, the blade 40 of embodiment 1 has at least one first groove 51 and at least one second groove 52 formed in the first side surface 43. In addition, similarly to the first side surface 43, at least one first groove 51 and at least one second groove 52 are formed in the second side surface 44 of the blade 40 according to embodiment 1. That is, the first and

second grooves

51 and 52 are not formed in the first and second side surfaces 43 and 44 of the blade 40 at the flat portion 53. In the vane groove 27 of embodiment 1, the first wall surface 28 and the second wall surface 29, which are opposed surfaces to the vane 40, are flat surfaces, as in the vane groove of a conventional general rotary compressor.

Specifically, the first groove 51 is a groove in which the internal pressure increases when the blade 40 advances. The first groove 51 includes a convex portion 51a protruding from the first end 41 toward the second end 42. In embodiment 1, the convex portion 51a has a shape in which two linear grooves communicate with each other at the apex portion 51 b. Further, a plurality of first grooves 51 may be formed in the first side surface 43 and the second side surface 44. In this case, the pitch P between the first grooves 51 may be equal or unequal. Here, as will be described later, in the present embodiment, the frictional force between the vane 40 and the vane groove 27 can be reduced by the increase in the pressure in the first groove 51 when the vane 40 moves forward. Therefore, when a plurality of first grooves 51 are formed, it is preferable that the first grooves 51 be arranged as close as possible. Therefore, in embodiment 1, the groove width ratio, which is a value obtained by dividing the width W of the first groove 51 by the pitch P, is set to be greater than 0 and smaller than 1.

The end 52a of the second groove 52 communicates with the first groove 51. The end 52b of the second groove 52 opens at the second end 42 of the vane 40 disposed in the spring housing chamber 33. That is, the end 52b of the second groove 52 communicates with the spring accommodating chamber 33. Further, a plurality of second grooves 52 may be formed in the first side surface 43 and the second side surface 44.

Next, the operation of the blade 40 of embodiment 1 will be described.

Fig. 5 is a diagram for explaining an operation when the vane of the rotary compressor according to embodiment 1 moves forward. Fig. 6 is a diagram for explaining the operation of the rotary compressor according to embodiment 1 when the blades retract. The blank arrows in fig. 5 and 6 show the traveling direction of the blade 40. The arrows with black ends shown in fig. 5 and 6 show the flow of the refrigerating machine oil in the first tank 51 and the second tank 52.

As described above, during driving of the rotary compressor 100, the refrigerating machine oil is supplied between the vane 40 and the vane groove 27. The refrigerating machine oil supplied between the vane 40 and the vane groove 27 moves together with the vane 40 due to the viscosity of the refrigerating machine oil. Therefore, as shown in fig. 5, when the vane 40 moves forward, the refrigerating machine oil flows from the end 51c toward the top 51b in the convex portion 51a of the first groove 51. As a result, the refrigerating machine oil flowing through the two grooves forming the convex portion 51a merges at the top portion 51b, and the pressure at the position of the top portion 51b increases. Since the oil film pressure at the flat portion 53 around the apex portion 51b is ensured by the pressure of the apex portion 51b, the first side surface 43 of the vane 40 floats from the first wall surface 28 of the vane groove 27, and the contact with the first wall surface 28 can be suppressed. Similarly, since the oil film pressure at the flat portion 53 around the apex portion 51b is ensured by the pressure of the apex portion 51b, the second side surface 44 of the vane 40 floats from the second wall surface 29 of the vane groove 27, and contact with the second wall surface 29 can be suppressed. Therefore, in the rotary compressor 100 according to embodiment 1, when the vane 40 moves forward, the frictional force between the vane 40 and the vane groove 27 can be reduced as compared with a conventional general rotary compressor, and the occurrence of vane separation can be suppressed.

Here, among conventional rotary compressors, there has been proposed a rotary compressor in which fine recessed portions are formed on sliding surfaces of blades and blade grooves or sliding surfaces of blade grooves and blades, thereby reducing frictional force between the blades and the blade grooves. However, in the conventional rotary compressor in which the frictional force between the vane and the vane groove is reduced, when the rotary compressor is used for a long period of time, the effect of reducing the frictional force between the vane and the vane groove is reduced, and the vane separation occurs.

Specifically, when the rotary compressor is used, metal powder is generated due to friction between the vane and the vane groove. In the rotary compressor, a sliding portion is also present at a portion other than between the vane and the vane groove. When the rotary compressor is used, metal powder is generated from sliding portions other than between the vane and the vane groove. In the rotary compressor, a product generated by a reaction between the refrigerant and the refrigerating machine oil is also generated. Therefore, in the conventional rotary compressor in which the frictional force between the vane and the vane groove is reduced, if the rotary compressor is used for a long period of time, the metal powder and the product intrude between the vane and the vane groove and are deposited in the fine concave portion formed in the vane or the vane groove. As a result, in the conventional rotary compressor in which the reduction of the frictional force between the blades and the blade grooves is achieved, if the rotary compressor is used for a long period of time, the effect of reducing the frictional force between the blades and the blade grooves is reduced, and the blades are separated.

On the other hand, in the rotary compressor 100 according to embodiment 1, as shown in fig. 6, when the vane 40 moves backward, the refrigerating machine oil flows from the top portion 51b toward the end portion 51c in the convex portion 51a of the first groove 51. The refrigerating machine oil in the first tank 51 flows into the second tank 52. In the rotary compressor 100 according to embodiment 1, when the vane 40 moves backward, the refrigerating machine oil flows from the end 52a toward the end 52b in the second groove 52. The refrigerating machine oil in the second groove 52 flows out from the end portion 52b to the spring housing chamber 33. Therefore, in the rotary compressor 100 according to embodiment 1, the second groove 52 can discharge the metal powder and the product that have entered between the vane 40 and the vane groove 27 from between the vane 40 and the vane groove 27. Therefore, in the rotary compressor 100 according to embodiment 1, the first groove 51 can be prevented from being filled with the metal powder and the product that have entered between the vane 40 and the vane groove 27. Therefore, the rotary compressor 100 according to embodiment 1 can suppress the blade separation for a long period of time as compared with a conventional rotary compressor in which the friction between the blades and the blade grooves is reduced.

In embodiment 1, the first groove 51 and the second groove 52 are formed in the first side surface 43 and the second side surface 44 which are the surfaces of the blade 40 facing the blade groove 27. The present invention is not limited to this, and the first groove 51 and the second groove 52 may be formed in the first wall surface 28 and the second wall surface 29, which are the surfaces of the vane groove 27 facing the vane 40. Here, as described above, the refrigerating machine oil supplied between the vane 40 and the vane groove 27 moves together with the vane 40. Therefore, when the first groove 51 is formed in the first wall surface 28 and the second wall surface 29, the convex portion 51a is formed so as to protrude from the second end 42 toward the first end 41 in order to increase the pressure inside the first groove 51 when the blade 40 moves forward. As a result, when the vane 40 moves forward, the refrigerating machine oil flows from the end 51c toward the top 51b in the convex portion 51a of the first groove 51, and the pressure at the position of the top 51b can be increased. Further, the first groove 51 and the second groove 52 may be formed on both the surface of the blade 40 facing the blade groove 27 and the surface of the blade groove 27 facing the blade 40. That is, if the first groove 51 and the second groove 52 are formed in at least one of the surface of the blade 40 facing the blade groove 27 and the surface of the blade groove 27 facing the blade 40, the blade separation can be suppressed for a long period of time.

As described above, the rotary compressor 100 according to embodiment 1 includes the cylinder 21, the rotary piston 30, the vane 40, and the spring 34. A cylinder chamber 22 is formed in the cylinder block 21. The rotary piston 30 is housed in the cylinder chamber 22 and eccentrically rotates in the cylinder chamber 22. First end 41 of vane 40 contacts the outer peripheral surface of rotary piston 30, and divides cylinder chamber 22 into suction chamber 23 and compression chamber 24. The spring 34 is housed in the spring housing chamber 33, and presses the second end 42, which is the end of the vane 40 opposite to the first end 41, toward the rotary piston 30. The cylinder 21 has a vane groove 27 formed therein, one end of which communicates with the cylinder chamber 22 and the other end of which communicates with the spring accommodating chamber 33. The vane 40 is slidably held in the vane groove 27. At least one first groove 51, in which the internal pressure increases when the vane 40 advances to protrude into the cylinder chamber 22, and at least one second groove 52, in which one end communicates with the first groove 51 and the other end communicates with the spring accommodating chamber 33, are formed in at least one of the surface of the vane 40 facing the vane groove 27 and the surface of the vane groove 27 facing the vane 40.

In the rotary compressor 100 configured as described above, the blade separation can be suppressed for a longer period of time than in the conventional art.

Embodiment 2.

By making the position of the first groove 51 formed on the surface on the compression chamber 24 side different from the position of the first groove 51 formed on the surface on the suction chamber 23 side as in embodiment 2, the vane separation can be further suppressed. Note that, in embodiment 2, items not described in particular are the same as those in embodiment 1, and the same functions and configurations as those in embodiment 1 are described using the same reference numerals as those in embodiment 1.

Fig. 7 and 8 are plan views for explaining a compression mechanism of the rotary compressor according to embodiment 2. Fig. 7 and 8 are views of the compression mechanism 20 with the upper bearing 31 removed from the top. In addition, fig. 7 shows a state where the blade 40 advances to the forefront. Fig. 8 shows a state in which the blade 40 is retracted to the rearmost position.

As shown in fig. 7, in the state where the vane 40 protrudes into the cylinder chamber 22, the vane 40 is inclined with respect to the vane groove 27 in a plan view by a difference between the pressure applied to the first side surface 43 from the compression chamber 24 and the pressure applied to the second side surface 44 from the suction chamber 23. Therefore, the vane 40 slides in the vane groove 27 in a posture in which the first end 41 is inclined toward the suction chamber 23 side.

Therefore, the gap between the first side surface 43 of the vane 40 and the first wall surface 28 of the vane groove 27 becomes smaller on the spring housing chamber 33 side and larger on the cylinder chamber 22 side. In other words, the gap between the first side surface 43 of the vane 40 and the first wall surface 28 of the vane groove 27 becomes smaller on the second end 42 side and larger on the first end 41 side. Therefore, the first side surface 43 of the vane 40 is easily brought into contact with the end 28a of the first wall surface 28 of the vane groove 27 on the spring accommodating chamber 33 side. Further, the gap between the second side surface 44 of the vane 40 and the second wall surface 29 of the vane groove 27 becomes smaller on the cylinder chamber 22 side and larger on the spring housing chamber 33 side. In other words, the gap between the second side surface 44 of the vane 40 and the second wall surface 29 of the vane groove 27 is smaller on the first end 41 side and larger on the second end 42 side. Therefore, the second side surface 44 of the vane 40 easily comes into contact with the end 29a of the second wall surface 29 of the vane groove 27 on the cylinder chamber 22 side.

Here, the magnitude of the oil film pressure generated in the gap to which the refrigerating machine oil is supplied is proportional to the third power of the reciprocal of the dimension of the gap. Therefore, in the region where the clearance is small, the effect of the floating of the vane 40 due to the increase in pressure in the first groove 51 can be expected. On the other hand, in the region where the clearance is large, the apparent size of the clearance is increased by the first groove 51, resulting in a decrease in oil film pressure. Therefore, by disposing the first groove 51 in the region where the clearance is small, the contact between the vane 40 and the vane groove 27 can be more effectively suppressed, and the frictional force between the vane 40 and the vane groove 27 can be more effectively reduced. Therefore, in embodiment 2, the blade 40 is configured as shown in fig. 9 and 10 below.

As described above, the gap between the first side surface 43 of the blade 40 and the first wall surface 28 of the blade groove 27 is smaller on the second end 42 side than the gap between the second side surface 44 of the blade 40 and the second wall surface 29 of the blade groove 27. In other words, the gap between the second side surface 44 of the blade 40 and the second wall surface 29 of the blade groove 27 is smaller on the first end 41 side than the gap between the first side surface 43 of the blade 40 and the first wall surface 28 of the blade groove 27. Therefore, the formation range of the first groove 51 of the first side surface 43 of the blade 40 is closer to the second end 42 than the formation range of the first groove 51 of the second side surface 44 of the blade 40. In other words, the range of formation of the first groove 51 on the second side surface 44 of the blade 40 is closer to the first end 41 than the range of formation of the first groove 51 on the first side surface 43 of the blade 40.

More specifically, the distance between the first groove 51 formed on the side closest to the second end 42 in the first side surface 43 of the blade 40 and the second end 42 is shorter than the distance between the first groove 51 formed on the side closest to the second end 42 in the second side surface 44 of the blade 40 and the second end 42. Further, the distance between the first groove 51 formed on the first end 41 side of the first side surface 43 of the blade 40 and the first end 41 is longer than the distance between the first groove 51 formed on the first end 41 side of the second side surface 44 of the blade 40 and the first end 41.

By configuring the vane 40 in this manner, the first groove 51 can be disposed at a position where the clearance is reduced when the vane 40 slides in the vane groove 27. As a result, contact between the vane 40 and the vane groove 27 can be further suppressed, and the frictional force between the vane 40 and the vane groove 27 can be further reduced.

In the end of embodiment 2, an example of a preferable formation range of the first groove 51 on the first side surface 43 of the blade 40 and an example of a preferable formation range of the first groove 51 on the second side surface 44 of the blade 40 are described with reference to fig. 9 and 10 and fig. 11 described later.

As described above, when the vane 40 slides in the vane groove 27, the first side surface 43 of the vane 40 most easily comes into contact with the end 28a of the first wall surface 28 of the vane groove 27 on the spring accommodating chamber 33 side. Therefore, it is preferable that the first groove 51 is formed in the first side surface 43 of the blade 40 in a range facing the end 28a when the blade 40 slides in the blade groove 27. Further, when the vane 40 slides in the vane groove 27, the second side surface 44 of the vane 40 most easily comes into contact with the end 29a on the cylinder chamber 22 side in the second wall surface 29 of the vane groove 27. Therefore, it is preferable that the second side surface 44 of the blade 40 is formed with a first groove 51 in a range facing the end 29a when the blade 40 slides in the blade groove 27.

Specifically, as shown in fig. 11, when the blade 40 is viewed in plan in a state where the blade 40 is retracted to the rearmost position, a direction passing through the first end 41 and the second end 42 of the blade 40 is defined as an X direction. As shown in fig. 7, the length of the blade 40 protruding from the blade groove 27 in the X direction in the state where the blade 40 has advanced to the forefront is defined as a stroke amount Xst. As shown in fig. 7 and 8, the length of the vane groove 27 in the X direction is a vane groove length lvgd. The formation range of the first groove 51 on the first side surface 43 of the blade 40 is lgd. A point closest to the first end 41 in the forming range lgd of the first groove 51 on the first side surface 43 of the blade 40 is set as a starting point lgd1. A point closest to the second end 42 in the formation range lgd of the first groove 51 on the first side surface 43 of the blade 40 is an end point lgd2. Lgs is a range in which the first groove 51 is formed in the second side surface 44 of the blade 40. A point closest to the first end 41 in the formation range lgs of the first groove 51 on the second side surface 44 of the blade 40 is set as a starting point lgs1. A point closest to the second end 42 in the range lgs of formation of the first groove 51 in the second side surface 44 of the blade 40 is an end point lgs2.

As shown in fig. 8, in the state where the blade 40 is retracted to the rearmost position, the first side surface 43 of the blade 40 faces the end 28a of the blade groove 27 at a position advanced from the first end 41 to the second end 42 along the X direction by the blade groove length lvgd. Therefore, it is preferable that the starting point lgd1 of the formation range lgd of the first groove 51 on the first side surface 43 of the blade 40 is set to a position advanced from the first end portion 41 to the second end portion 42 along the X direction by the blade groove length lvgd. As shown in fig. 7, in the state where the blade 40 has advanced to the forefront, the blade 40 is inclined with respect to the blade groove 27, but the first side surface 43 of the blade 40 is opposed to the end 28a of the blade groove 27 at a position substantially advanced by the stroke amount Xst from the starting point lgd1 toward the second end 42 in the X direction. Therefore, it is preferable that the end lgd2 of the formation range lgd of the first groove 51 on the first side surface 43 of the blade 40 is set to a position advanced by the stroke amount Xst from the start lgd1 to the second end 42 in the X direction. By forming the first groove 51 in the formation range lgd of the first side surface 43 of the blade 40, the end 28a most likely to come into contact with the first side surface 43 of the blade 40 when the blade 40 slides can be further suppressed from coming into contact with the first side surface 43 of the blade 40. Therefore, the frictional force between the vane 40 and the vane groove 27 can be further reduced.

As shown in fig. 8, in the state where the vane 40 has retreated to the rearmost position, the second side surface 44 of the vane 40 faces the end 29a of the vane groove 27 at the position of the first end 41. Therefore, it is preferable that the starting point lgs1 of the formation range lgs of the first groove 51 on the second side surface 44 of the blade 40 be the position of the first end 41. As shown in fig. 7, in the state where the blade 40 has advanced to the forefront, the blade 40 is inclined with respect to the blade groove 27, but the second side surface 44 of the blade 40 is opposed to the end 29a of the blade groove 27 substantially at a position advanced from the starting point lgs1 toward the second end 42 by the stroke amount Xst in the X direction. Therefore, it is preferable that the end lgs2 of the formation range lgs of the first groove 51 on the second side surface 44 of the blade 40 is set to a position advanced from the start lgs1 toward the second end 42 by the stroke amount Xst in the X direction. By forming the first groove 51 in such a formation range lgs of the second side surface 44 of the blade 40, the end portion 29a which is most likely to contact the second side surface 44 of the blade 40 when the blade 40 slides can be further suppressed from contacting the second side surface 44 of the blade 40. Therefore, the frictional force between the vane 40 and the vane groove 27 can be further reduced.

As described in embodiment 1, the first groove 51 and the second groove 52 may be formed in the first wall surface 28 and the second wall surface 29 which are the surfaces of the vane groove 27 facing the vane 40. At this time, when the first groove 51 is disposed at a position where the clearance is reduced when the vane 40 slides in the vane groove 27, the first groove 51 is formed at the following position. Specifically, the distance between the first groove 51 formed on the first wall surface 28 closest to the second end 42 and the second end 42 is shorter than the distance between the first groove 51 formed on the second wall surface 29 closest to the second end 42 and the second end 42. Further, the distance between the first groove 51 formed on the first wall surface 28 closest to the first end 41 and the first end 41 is longer than the distance between the first groove 51 formed on the second wall surface 29 closest to the first end 41 and the first end 41.

Embodiment 3.

By setting the depth of the second groove 52 to be as in embodiment 3, the metal powder and the products that have entered between the blade 40 and the blade groove 27 can be more easily discharged, and the blade separation can be more suppressed for a longer period of time. Note that in embodiment 3, items not described in particular are the same as those in embodiment 1 or embodiment 2, and the same functions and configurations as those in embodiment 1 or embodiment 2 will be described using the same reference numerals as those in embodiment 1 or embodiment 2.

Fig. 12 is a view of the vane of the rotary compressor according to embodiment 3 as viewed from the first side. Fig. 13 is a sectional view B-B of fig. 12.

As shown in fig. 12 and 13, in embodiment 3, the depth of the second groove 52 is deeper than the depth of the first groove 51.

In the case of considering the shear flow of the fluid between two planes, the average flow velocity of the fluid is 1/2 of the slip velocity. Thus, the flow rate of the fluid flowing between the two planes is the product of the average flow velocity and the cross-sectional area. That is, by increasing the depth of the second groove 52, the flow rate of the refrigerating machine oil in the second groove 52 increases. Further, as the flow rate of the refrigerating machine oil in the second groove 52 increases, the inflow amount of the refrigerating machine oil from the first groove 51 to the second groove 52 also increases when the vane 40 moves backward, and the flow velocity of the refrigerating machine oil in the first groove 51 also increases. Therefore, by increasing the depth of the second groove 52, the metal powder and the products that have entered between the blade 40 and the blade groove 27 can be more easily discharged.

In embodiment 3, the depth of the first groove 51 and the depth of the second groove 52 are set as follows. The designed clearance between the vane 40 and the vane groove 27 is set to a nominal clearance. The depth of the first groove 51 is 0.01 times or more the nominal clearance and 10 times or less the nominal clearance. The depth of the second groove 52 is larger than the depth of the first groove 51. Here, in embodiment 3, the second groove 52 of the first side surface 43 and the second groove 52 of the second side surface 44 are formed at opposing positions. Therefore, in embodiment 3, the depth of the second groove 52 is less than half the thickness of the blade 40. The thickness of the blade 40 is a dimension in a direction in which the first side surface 43 and the second side surface 44 face each other.

Embodiment 4.

In embodiments 1 to 3, the convex portion 51a of the first groove 51 has a shape in which two linear grooves communicate with each other at the apex portion 51 b. However, the shape of the convex portion 51a is merely an example. The convex portion 51a may have any shape as long as the refrigerator oil flows toward the top portion 51b when the vane 40 moves forward. In embodiment 4, several examples of the shape of the convex portion 51a will be described. The shape of the second groove 52 shown in embodiments 1 to 3 is merely an example. The second groove 52 may have various shapes as long as it communicates with the first groove 51 and the spring housing chamber 33. In embodiment 4, several examples of the shape of the second groove 52 will be described. Note that, in embodiment 4, items not described in particular are the same as those in any of embodiments 1 to 3, and the same functions and configurations as those in any of embodiments 1 to 3 are described using the same reference numerals as those in any of embodiments 1 to 3.

Fig. 14 is a view of an example of the vane of the rotary compressor according to embodiment 4 as viewed from the first side.

As shown in fig. 14, at least a part of the convex portion 51a of the first groove 51 may be a curved groove. Fig. 14 shows an example in which the convex portion 51a of the first groove 51 is formed entirely of a curved groove.

In fig. 14, the curved groove of the convex portion 51a constituting the first groove 51 is a groove projecting from the first end 41 toward the second end 42. As shown in fig. 15, at least a part of the convex portion 51a of the first groove 51 may be a curved groove protruding from the second end 42 toward the first end 41. Fig. 15 shows an example in which the convex portion 51a of the first groove 51 is formed entirely of a curved groove having a convex shape from the second end 42 toward the first end 41.

A direction perpendicular to the sliding direction of the blade 40 when the blade 40 is viewed from the side is defined as the width direction of the blade 40. In the case of fig. 16, the vertical direction on the paper surface is the width direction of the blade 40. The convex portion 51a of the blade 40 is symmetrical with respect to an imaginary line passing through the center in the width direction of the blade 40 and parallel to the sliding direction of the blade 40. The shape of the convex portion 51a of the blade 40 is not limited to this, and may be asymmetrical with respect to an imaginary line passing through the center in the width direction of the blade 40 and parallel to the sliding direction of the blade 40, as shown in fig. 16.

The blade 40 includes one convex portion 51a. The blade 40 may include a plurality of convex portions 51a as shown in fig. 17. Fig. 17 shows an example in which two convex portions 51a are arranged in the width direction of the blade 40.

The convex portion 51a of the blade 40 may be a combination of the above structures.

Fig. 18 and 19 are views of an example of the vane of the rotary compressor according to embodiment 4 as viewed from the first side.

As shown in fig. 18 and 19, an axis parallel to the sliding direction of the blade 40 when the blade 40 is viewed from the side is defined as a Y axis. When the Y axis is defined as described above, the second groove 52 is parallel to the Y axis when the blade 40 is viewed from the side. The present invention is not limited to this, and as shown in fig. 18 and 19, the second groove 52 may be inclined with respect to the Y axis when the blade 40 is viewed from the side. In addition, from the viewpoint of facilitating discharge of the metal powder and the product, it is preferable that the inclination of the second groove 52 with respect to the Y axis is small. For example, the angle θ, which is an angle extending toward the second end 42, of the angles formed by the Y-axis and the second groove 52 is preferably smaller than 45 °.

It is needless to say that at least a part of the second groove 52 may be a curved groove.

Embodiment 5.

In embodiments 1 to 4, the width and depth of the first groove 51 are constant at all positions. The first groove 51 is not limited to this, and at least one of the width and the depth may be different depending on the position. In embodiment 5, an example of such a first groove 51 will be described. In embodiments 1 to 4, the width and depth of the second groove 52 are constant at all positions. The second groove 52 is not limited to this, and at least one of the width and the depth may be different depending on the position. In embodiment 5, an example of such a second groove 52 will be described. Note that, in embodiment 5, items not described in particular are the same as those in any of embodiments 1 to 4, and the same functions and configurations as those in any of embodiments 1 to 4 are described using the same reference numerals as those in any of embodiments 1 to 4.

Fig. 20 is a view of the vane of the rotary compressor according to embodiment 5 as viewed from the first side. Fig. 21 is a cross-sectional view C-C of fig. 20.

As shown in fig. 20 and 21, the depth of the convex portion 51a of the first groove 51 of embodiment 5 decreases from the end 51c toward the apex 51 b. As described above, when the vane 40 moves forward, the refrigerating machine oil flows from the end 51c toward the top 51b in the convex portion 51a, and the pressure at the position of the top 51b increases, whereby the frictional force between the vane 40 and the vane groove 27 can be reduced. In this case, when the cross-sectional area of the groove is reduced with respect to the flow direction of the refrigerating machine oil, the refrigerating machine oil is incompressible, and therefore, a higher pressure is generated. Therefore, by configuring the convex portion 51a of the first groove 51 so that the depth decreases from the end portion 51c toward the apex portion 51b, the pressure at the position of the apex portion 51b can be further increased when the blade 40 moves forward, as compared with the case where the depth of the convex portion 51a is constant. Therefore, by configuring the convex portion 51a of the first groove 51 such that the depth decreases from the end portion 51c toward the apex portion 51b, the frictional force between the blade 40 and the blade groove 27 can be further reduced as compared with the case where the depth of the convex portion 51a is constant.

Based on the same idea, in the second groove 52, when the sectional area increases with respect to the flow direction of the refrigerating machine oil, the refrigerating machine oil flows easily without receiving pressure resistance. Thus, the second groove 52 may increase in depth from the first end 41 toward the second end 42. Accordingly, as compared with the case where the depth of the second groove 52 is constant, the metal powder and the product that have entered between the vane 40 and the vane groove 27 can be further discharged, and the vane separation can be suppressed for a longer period of time.

Fig. 20 and 21 show an example in which the depth of the groove constituting the convex portion 51a changes linearly. However, the depth of the groove constituting the convex portion 51a may vary in a curved shape or may vary in a stepwise shape. The depth of the second groove 52 varies in the same manner.

By changing the width of the groove, the cross-sectional area of the groove can also be changed. Therefore, as shown in fig. 22, the width of the convex portion 51a of the first groove 51 may be reduced from the end 51c toward the top 51 b. Even if the convex portion 51a of the first groove 51 is configured in this manner, the cross-sectional area of the convex portion 51a can be reduced from the end portion 51c toward the top portion 51 b. Therefore, even if the convex portion 51a of the first groove 51 is configured as described above, the pressure at the position of the apex portion 51b can be further increased when the blade 40 moves forward, as compared with the case where the width of the convex portion 51a is constant. Therefore, even if the convex portion 51a of the first groove 51 is configured in this way, the frictional force between the blade 40 and the blade groove 27 can be further reduced as compared with the case where the width of the convex portion 51a is constant. Here, the convex portion 51a may have both a width and a depth decreasing from the end 51c toward the top 51 b. That is, the convex portion 51a can further reduce the frictional force between the blade 40 and the blade groove 27 by reducing at least one of the width and the depth from the end portion 51c toward the apex portion 51 b.

Likewise, second slot 52 may increase in width from first end 41 toward second end 42. Accordingly, as compared with the case where the width of the second groove 52 is constant, the metal powder and the products that have entered between the blade 40 and the blade groove 27 can be further discharged, and the blade separation can be suppressed for a longer period of time. Here, the second groove 52 may increase in both width and depth from the first end 41 toward the second end 42. That is, the second groove 52 can suppress the blade separation for a longer period of time by reducing at least one of the width and the depth from the first end 41 toward the second end 42.

Fig. 22 shows an example in which the width of the groove constituting the convex portion 51a linearly changes. However, the width of the groove constituting the convex portion 51a may vary in a curved shape or may vary in a stepwise shape. The width of the second groove 52 varies in the same manner.

Description of the reference numerals

1 closed container, 2 suction pipe, 3 discharge pipe, 10 motor, 11 stator, 12 rotor, 20 compression mechanism, 21 cylinder, 22 cylinder chamber, 23 suction chamber, 24 compression chamber, 25 suction port, 26 discharge port, 27 vane groove, 28 first wall surface, 28a end, 29 second wall surface, 29a end, 30 rotary piston, 31 upper bearing portion, 32 lower bearing portion, 33 spring housing chamber, 34 spring, 40 vane, 41 first end, 42 second end, 43 first side surface, 44 second side surface, 51 first groove, 51a convex portion, 51b top portion, 51c end portion, 52 second groove, 52a end portion, 52b end portion, 53 flat portion, 60 drive shaft, 61 main shaft portion, 62 eccentric portion, 100 rotary compressor, 101 suction muffler.

Claims

1. A rotary compressor is provided with:

a cylinder block formed with a cylinder chamber;

a rotary piston that is housed in the cylinder chamber and performs eccentric rotary motion in the cylinder chamber;

a vane having a first end portion contacting an outer circumferential surface of the rotary piston, the vane dividing the cylinder chamber into a suction chamber and a compression chamber; and

a spring that is housed in a spring housing chamber and that urges a second end portion that is an end portion of the vane on a side opposite to the first end portion toward the rotary piston,

a vane groove is formed in the cylinder body, one end of the vane groove communicates with the cylinder chamber, and the other end communicates with the spring housing chamber,

the blade is slidably held in the blade groove, wherein,

at least one first groove in which the internal pressure increases when the vane advances to protrude into the cylinder chamber is formed in at least one of the vane surface facing the vane groove and the vane surface facing the vane, and at least one second groove in which one end communicates with the first groove and the other end communicates with the spring accommodating chamber is formed.

2. The rotary compressor of claim 1,

the first groove and the second groove are formed on the surface of the blade facing the blade groove,

the first groove includes a convex portion protruding from the first end toward the second end.

3. The rotary compressor of claim 2,

in a case where an opposing surface of the vane that opposes the vane groove on the compression chamber side is a first side surface and an opposing surface of the vane that opposes the vane groove on the suction chamber side is a second side surface,

a distance between the first groove formed in the first side surface at a position closest to the second end portion side and the second end portion is shorter than a distance between the first groove formed in the second side surface at a position closest to the second end portion side and the second end portion,

the distance between the first groove formed in the first side surface at a position closest to the first end portion side and the first end portion is longer than the distance between the first groove formed in the second side surface at a position closest to the first end portion side and the first end portion.

4. The rotary compressor of claim 1,

the first groove and the second groove are formed on the surface of the vane groove facing the vane,

the first groove includes a convex portion protruding from the second end toward the first end.

5. The rotary compressor of claim 4,

in a case where a surface of the vane groove facing the vane on the compression chamber side is a first wall surface and a surface of the vane groove facing the vane on the intake chamber side is a second wall surface,

a distance between the first groove formed in the first wall surface at a position closest to the second end and the second end is shorter than a distance between the first groove formed in the second wall surface at a position closest to the second end and the second end,

the distance between the first groove formed in the first wall surface at the position closest to the first end and the first end is longer than the distance between the first groove formed in the second wall surface at the position closest to the first end and the first end.

6. The rotary compressor according to any one of claims 2 to 5,

the convex portion of the first groove decreases in at least one of width and depth from an end portion toward a top portion.

7. The rotary compressor according to any one of claims 1 to 6,

the second groove has a depth deeper than a depth of the first groove.

8. The rotary compressor according to any one of claims 1 to 7,

the second groove increases at least one of a width and a depth from the first end toward the second end.