JP2003056621A - Shock absorbing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorbing device capable of providing a damping according to the shape of the valve element and the diameter of a communication hole of a damping valve. SOLUTION: In this shock absorbing device, two chambers 9 and 10 are separated from each other through a piston P assembled in a cylinder tube 1. The piston P comprises an assembly hole 26 allowing one chamber to communicate with the other chamber and the damping valve V assembled in the assembly hole 26. When the damping valve V is opened by the movement of the piston P, a damping force can be developed according o the opening of a restrictor. The piston P comprises recessed parts 29 and 30 allowing the assembly hole 26 to open to the outer periphery thereof and an axial hole 27 communicating with the recessed parts 29 and 30 and formed in axial direction. When the damping valve V is opened, pressure oil in the high pressure side chamber is led to the low pressure chamber from the assembly hole 26 to the recessed parts 29 and 30 through the axial hole 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber for suppressing the shaking of a building caused by an earthquake or the like.

[0002]

2. Description of the Related Art A conventional shock absorber shown in FIG. 6 is provided with a first cylinder tube 1 and a second cylinder tube 2 positioned outside the first cylinder tube 1, and between these tubes 1 and 2. Further, a tank T is formed. The first cylinder tube 1 has a rod side closing member 3 fitted to one end 1a thereof and a valve block b to the other end 1b thereof.
The bottom-side closing member 4 is fitted through the.

A ring-shaped connecting member 5 is fixed to the rod-side closing member 3, and a second member is attached to the connecting member 5.
One end 2a of the cylinder tube 2 is fitted and fixed. Further, the other end 2b of the second cylinder tube 2 is directly fitted and fixed to the bottom side closing member 4. Inside the first cylinder tube 1, a piston 6 is slidably incorporated, and the piston 6 allows the first
Inside the cylinder tube 1, the rod side chamber 9 and the bottom side chamber 10
It is divided into and. Further, a piston rod 7 which moves integrally with the piston 6 is fixed to the piston 6. The piston rod 7 includes the rod-side closing member 3
Of the rod side blocking member 3
The rod hole 8 formed in the above is slidably supported via a bearing 15.

Assembling holes 16 and 16 are formed in the piston 6 in the axial direction, the first damping valve 11 is incorporated in one assembling hole 16, and the second damping valve 12 is incorporated in the other assembling hole 16. . The first damping valve 11 permits only the flow of oil from the rod side chamber 9 to the bottom side chamber 10, and the second damping valve 12 controls the bottom side chamber 10.
Only the flow of oil from the rod side chamber 9 to the rod side chamber 9 is allowed. Then, when the first and second damping valves 11 and 12 are opened and a flow is generated, a damping force corresponding to the opening is exerted. The detailed structure of the first and second damping valves 11 and 12 will be described later.

The piston 6 has two safety valves (not shown) incorporated therein. Of these safety valves,
One safety valve allows only the oil flow from the rod side chamber 9 to the bottom side chamber 10, and the other safety valve allows only the oil flow from the bottom side chamber 10 to the rod side chamber 9. Then, these safety valves open when a predetermined pressure is reached, and oil flows from the rod side chamber 9 to the bottom side chamber 10 or from the bottom side chamber 10 to the rod side chamber 9.

On the other hand, assembling holes 16 and 16 are formed in the valve block b, the third damping valve 13 is incorporated in the assembling hole 16 on the upper side of the drawing, and the assembling hole 16 on the lower side of the drawing.
The safety valve 14 is incorporated in the. These third damping valve 13
The safety valve 14 and the safety valve 14 allow only the flow of oil from the bottom chamber 10 to the tank T. The third damping valve 13 has the same specifications as the second damping valve 12, and the same damping force as the damping force of the second damping valve 12 is exerted by the third damping valve 13. The damping forces of the first to third damping valves 11 to 13 are proportional to the speed of the piston 6.

Since the structures of the first to third damping valves 11 to 13 are the same, the structure of the first pressure reducing valve 11 will be described here with reference to FIG. As shown in the drawing, a communication hole 17 is formed in the piston 6 and the communication hole 17 is communicated with the assembly hole 16. In addition, the above-mentioned mounting hole 1
The valve body 18 and the spring 19 are incorporated into the valve 6, and the spring force of the spring 19 is applied to the valve body 18 via the guide member 20. The communication between the rod-side chamber 9 and the assembly hole 16 is blocked in a state where the flange portion 18a of the valve body 18 is pressed against the seat portion 21.

Further, an adjusting bolt 22 is incorporated in the assembling hole 16, and the spring force of the spring 19 can be adjusted by the adjusting bolt 22. Further, the adjustment bolt 22 has a notch 25
And the assembly hole 16 is formed through the notch 25.
And the bottom side chamber 10 are always in communication with each other.

The valve element 18 has a convex portion 23 formed on the tip side thereof, and the convex portion 23 is slidably inserted into the communication hole 17. Further, a groove 24 is formed in this convex portion 23. The groove 24 has a curved bottom surface so that the flow passage area changes according to the lift amount of the valve body 18.

In the first damping valve 11 as described above, when the valve body 18 moves to the right against the spring 19 due to the pressure increase in the rod side chamber 9, for example, the convex portion 23 provided on the valve body 18 is released. It starts to move in the direction of exiting from the communication hole 17. By the movement of the valve body 18, the flange portion 18
When a is separated from the seat portion 21, the rod-side chamber 9 and the mounting hole 16 communicate with each other via the groove 24. Therefore, the hydraulic oil in the rod side chamber 9 is discharged to the bottom side chamber 10 through the groove 24, the assembling hole 16 and the notch 25. Then, at this time, a predetermined damping force is exerted by the flow resistance generated according to the opening area of the groove 24.

A check valve C is provided in the valve block b. The check valve C compensates for a shortage of the flow rate generated in the bottom side chamber 10 when the piston 6 moves in the rod side chamber 9 direction. That is, the rod side chamber 9
Since there is a piston rod 7 in the chamber, the volume is smaller than that in the bottom chamber 10. Therefore, when the piston 6 is moved in the direction of the rod side chamber 9, the flow rate supplied from the rod side chamber 9 to the bottom side chamber 10 via the first damping valve 11 is insufficient by the volume of the piston rod 7. This shortage is supplemented by being sucked from the tank T via the check valve C.

In the conventional device as described above, the piston rod 7 side and the bottom closing member 4 side are fixed to the pillars of the building, respectively. In this state, when the building shakes due to an earthquake or the like, the piston 6 moves. However, the movement of the piston 6 is
It is damped by the damping valves 11-13. For example, when the piston 6 moves toward the rod side chamber 9, the first damping valve 11
When the piston 6 moves toward the bottom side chamber 10 due to the damping of the movement thereof, the movement is damped by the second damping valve 12 and the third damping valve. Damping the movement of the piston 6 in this way suppresses the shaking and vibration of the building.

[0013]

In the above-mentioned conventional example, the first
~ When the third damping valves 11 to 13 are opened, the pressure oil in the high pressure side chamber is discharged to the low pressure side chamber through the communication hole 17 → the groove 24 → the assembly hole 16 → the cutout portion 25. However, since the flow resistance on the downstream side of the groove 24 is large, there is a problem that a predetermined damping characteristic cannot be obtained. That is, in the assembly hole 16, the spring 16 acts as a resistance to impair the flow of pressure oil. Further, also in the cutout portion 25, the flow passage of the pressure oil is deteriorated because the flow passage area is small. Therefore, when the first to third damping valves 11 to 13 are opened, a large flow resistance is generated on the downstream side of the groove 24, and the groove 2
The attenuation characteristic of the diaphragm formed by 4 changes. That is, even if the damping characteristic is set according to the shape of the valve body 18 and the diameter of the communication hole 17, there is a problem that the predetermined damping characteristic cannot be obtained. An object of the present invention is to provide a damping device that can obtain a damping force according to the shape of the valve body of the damping valve and the diameter of the communication hole.

[0014]

A first aspect of the present invention is to form a cylinder tube, a piston incorporated in the cylinder tube, two chambers defined by the piston, a piston, and one chamber and the other chamber. A damping device that has an assembly hole that communicates with the chamber and a damping valve that is installed in this assembly hole, and that when the damping valve is opened by the movement of the piston, a damping force is exhibited according to the throttle opening degree. In the above piston, the piston is provided with a recess for opening the assembly hole to the outer periphery and an axial hole formed in the axial direction while communicating with the recess, and when the damping valve is opened, the high pressure side chamber It is characterized in that the pressure oil is guided from the assembling hole to the chamber on the low pressure side through the recess and the axial hole.

The second invention is the same as the first invention,
It is characterized in that a recess communicating with the assembly hole is formed in an annular shape on the outer circumference of the piston.

A third aspect of the present invention is the valve block according to the first or second aspect, wherein the valve block is incorporated into one of the chambers of the cylinder tube, and the valve block is formed in the valve block, and the one chamber and the tank are provided. It is characterized in that it is provided with an assembling hole communicating with each other and a damping valve incorporated in the assembling hole, and that the valve block is provided with a lateral hole for communicating the assembling hole with the tank.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The first embodiment shown in FIGS. 1 to 4 is characterized by the structure of a piston P and a valve block B, and other parts are the same as those of the conventional example.
Therefore, in the following, the piston P and the valve block B will be described.
The configuration will be mainly described, and the same components as those of the related art will be denoted by the same reference numerals and detailed description thereof will be omitted. Figure 1
It is a partial cross-sectional view of the first cylinder tube 1. As shown in the figure, a piston P is slidably incorporated in the first cylinder tube 1, and the rod side chamber 9 and the bottom side chamber 10 are partitioned by this piston P.

An assembly hole 26 and an axial hole 27 are formed in the piston P. These assembling holes 26
The axial holes 27 are alternately formed in the circumferential direction, as shown in FIG. Further, as shown in FIG. 2, the assembling hole 26 and the axial hole 27 are communicated with each other through a communicating hole 28. A damping valve V is incorporated in each of the assembly holes 26. Among these pressure reducing valves V, those provided near the rod-side chamber 9 allow only the flow of oil from the bottom-side chamber 10 to the rod-side chamber 9, and those provided near the bottom-side chamber 10 are those that are provided near the rod-side chamber 9. To allow only the oil flow from the bottom chamber 10 to the bottom chamber 10. In addition,
The detailed structure of these damping valves V will be described later.

A first annular recess 29 and a second annular recess 30 are formed on the outer circumference of the piston P, and the first and second annular recesses 29, 30 surround the assembly hole 26 and the axial hole 27. It communicates in the direction (see FIG. 3). The first and second annular recesses 29, 30 are formed with radial holes 31 in which the inner walls are made substantially vertical while the inner walls of the first and second annular recesses 29, 30 are inclined. Then, only the bottoms of the first and second annular recesses 29, 30 in which the radial holes 31 are formed are partially deepened. The reason for doing this will be described later. A seal member 32 is provided between the first annular recess 29 and the second annular recess 30.
The rod side chamber 9 is installed by the seal member 32.
And the bottom side chamber 10 is disconnected.

On the other hand, as shown in FIG. 1, the mounting hole 2 is also formed in the valve block B assembled in the bottom chamber 10.
Two 6 are formed, and the damping valve V is incorporated in each assembly hole 26. These damping valves V are provided in the bottom chamber 10
To allow only the flow of pressure oil from the tank chamber t to the tank chamber t, and has the same structure as the damping valve V incorporated in the piston P. As shown in FIG. 4, lateral holes 34, 34 are communicated with the valve block B incorporating the damping valve V in this manner, and the assembly hole 26 and the tank chamber t are communicated with each other through these lateral holes 34, 34. . Further, one end of the assembly hole 26 is communicated with the bottom side chamber 10 via the communication hole 28.

A plurality of suction holes 52 are formed in the valve block B as shown in FIG. 4, and the suction holes 52 are closed by a check valve C. This check valve C, like the above-mentioned conventional example, compensates for the insufficient flow rate that occurs in the bottom side chamber 10 when the piston P moves in the direction of the rod side chamber 9. Further, reference numeral 33 in the drawing denotes an air vent passage, through which the air accumulated in the cylinder is discharged to the outside.

Next, the specific structure of the damping valve V will be described with reference to FIG. The damping valve V includes a casing 35 and a valve body 36 incorporated in the casing 35.
A guide member 37 for guiding the valve body 36, a spring 38 for pressing the valve body 36 against the seat portion 36a,
Adjustment bolt 39 for adjusting the spring force of this spring 38
It consists of and. A distribution hole 40 and a plurality of discharge holes 41 are formed in the casing 35. The flow hole 40 allows the convex portion 42 provided at the tip of the valve body 36 to be inserted therein and is made to coincide with the communication hole 28.

The valve body 36 has a guide hole 43 and a shaft hole 4 therein.
4 is formed, and the guide hole 43 and the communication hole 28 are communicated with each other through the shaft hole 44. Further, a guide member 37 is slidably inserted into the guide hole 43, and the pressure of the rod side chamber 9 is applied to the tip of the guide member 37. The reason for doing this is to improve the workability in assembling. That is, the pressure generated in the rod side chamber 9 acts on the valve body 36, but the pressure generated in the rod side chamber 9 is very large. In order to obtain a predetermined damping characteristic for such a large pressure, the valve body 36 must be pressed against the seat portion 36a by using a spring having a strong spring force. However, when a spring having a strong spring force is used, there arises a problem that it becomes difficult to incorporate the spring into the casing 35 or the spring cannot be incorporated.

Therefore, in this embodiment, the guide hole 43 and the shaft hole 44 are formed in the valve body 36 as described above, and the pressure generated in the rod side chamber 9 is guided to the guide hole 43. With this configuration, the pressure receiving area of the valve body 36 is reduced by the area of the tip of the guide member 37, and thus the thrust force generated in the valve body 36 when the high pressure of the rod side chamber 9 is applied is also reduced. If the thrust force generated in the valve body 36 becomes small, a spring having a small spring force can be used, which makes it difficult to assemble the spring.
It is possible to prevent the inconvenience that the spring cannot be incorporated.

Further, the groove 4 is formed in the convex portion 42 of the valve body 36.
5 is formed. The groove 45 allows the communication hole 28 and the inside of the casing 35 to communicate with each other when the valve body 36 separates from the seat portion 37. Then, the opening area of the groove 45 is determined by the lift amount of the valve body 36, and the opening portion of the groove 45 constitutes a diaphragm.

The damping valve V as described above can be assembled in advance. That is, when the valve body 36, the guide member 37, and the spring 38 are incorporated in the casing 35 and one end of the casing 35 is closed by the adjusting bolt 39, the damping valve V can be handled as one component. Therefore, the damping characteristic of the damping valve V can be tested before being incorporated into the piston P or the valve block B. Further, since the damping characteristics can be known before the piston P and the like are assembled, the adjustment work can be easily performed.

The damping valve V as described above is connected to the piston P.
After inserting the valve block B into the assembly 26 of the valve block B, the retaining member 46 is tightened. When the retaining member 46 is tightened, the front end portion and the rear end portion of the damping valve V in the insertion direction are
It is firmly held by the mounting hole 26. The tip end portion of the damping valve V in the insertion direction is held by the slanted inner wall portion of the annular recess 30.
If the inner wall of the valve is vertical, the mounting hole 26 must be formed a little deeper in order to hold the front end portion of the damping valve V in the insertion direction. In order to form the mounting hole 26 deep, the axial length of the piston P must be increased. That is, when the inner wall of the annular recess 30 is made vertical, the axial length of the piston P becomes long.
On the other hand, in this embodiment, since the inner wall of the annular recess 30 is inclined, such an inconvenience does not occur.

When the damping valve V is installed in the mounting hole 26,
A gap 47 is formed between the casing 35 and the bottom of the radial hole 31.
Is formed. If there is such a gap 47, even if the discharge port 41 of the casing 35 is located at the bottom, the inside of the casing 35 and the annular recessed portion 3 are disposed via the discharge port 41 located at the bottom.
It is possible to communicate with 0. That is, casing 3
The area of the flow path that connects the inside of 5 with the annular recesses 29, 30 is made large. A cutout portion 56 is formed in the adjustment bolt 39 of the damping valve V, and the assembly hole 26 is communicated with the chamber 9 or the chamber 10 through the cutout portion 56.

Next, the operation of the first embodiment will be described. For example, when the piston P moves to the left in FIG. 1 and the pressure in the rod side chamber 9 rises, this high pressure acts on the valve body 36 of the damping valve V provided near the bottom side chamber 10 of the piston P. When the valve element 36 moves to the right against the spring 38, the convex portion 42 provided on the valve element 36.
However, the communication hole 28 and the inside of the casing 35 communicate with each other through the groove 45 by moving in the direction of coming out of the communication hole 28.

Therefore, the hydraulic oil in the rod-side chamber 9 is axially bored 27 (provided near the rod-side chamber 9) → communication hole 28 → groove 45 → casing 35 → discharge port 41 → radial hole 31 → annular recess. 30 → axial hole 27 (bottom side chamber 1
It is guided to the bottom side chamber 10 via the one provided near 0). If the hydraulic oil that has passed through the groove 45 is guided to the bottom side chamber 10 through such a route, the flow resistance on the downstream side of the groove 45 can be suppressed to be small. Therefore, the valve body 36 of the damping valve V
It is possible to obtain the damping characteristic set according to the shape of and the diameter of the communication hole 28.

Contrary to the above, if the piston P moves leftward in the figure and the pressure in the bottom chamber 10 rises,
The damping valve V provided near the rod side chamber 9 of the piston P opens. Therefore, the hydraulic oil in the bottom side chamber 10 has an axial hole 27 (provided near the bottom side chamber 10) → communication hole 28.
→ groove 45 → inside casing 35 → exhaust port 41 → radial hole 3
1 → annular recess 29 → guided to the rod side chamber 9 through the axial hole 27 (provided near the rod side chamber 9). Therefore, also in this case, the flow resistance on the downstream side of the groove 45 can be suppressed to be small, and the damping characteristic set by the shape of the valve body 36 of the damping valve V and the diameter of the communication hole 28 can be obtained.

Further, the damping valve V incorporated in the valve block B is also opened by increasing the pressure of the bottom side chamber 10. When the damping valve V is opened, the hydraulic oil in the bottom side chamber 10 is guided to the tank chamber t through the communication hole 28 → groove 45 → inside the casing 35 → discharge port 41 → lateral hole 34. If the hydraulic oil that has passed through the groove 45 along such a route is introduced into the tank chamber t, the groove 4
The flow resistance on the downstream side of 5 can be suppressed small. Therefore, also in this case, the damping characteristic set by the shape of the valve body 36 of the damping valve V and the diameter of the communication hole 28 can be obtained. Since the hydraulic oil in the casing 35 of the damping valve V is guided to the chamber 9 or the chamber 10 via the notch 56 formed in the adjusting bolt 39, the flow on the downstream side of the groove 45 is also caused by this flow path. The resistance can be kept small.

In the first embodiment described above, the structure on both sides of the piston P is the same with the seal member 32 as a boundary, so that the damping characteristics when the piston P moves to the right,
The damping characteristics when the piston P moves to the left are made equal. On the other hand, the second embodiment shown in FIG.
The configuration is such that a predetermined damping force is obtained only when the piston P moves to the left in the drawing. That is, in the second embodiment, when the piston P moves to the right in the drawing, the hydraulic oil in the bottom side chamber 10 changes to the check valve 50.
The damping force is not exerted by being guided to the rod side chamber 9 via the.

More specifically, an annular recess 51 is formed in the piston P, and the assembly hole 26 formed from the bottom chamber 10 side of the piston P is communicated with the annular recess 51. Further, a communication hole 55 is formed in the piston P, and the assembly hole 26 and the rod side chamber 9 are communicated with each other through the communication hole 55. And the assembling hole 2 thus configured
6, a damping valve V is incorporated. In addition, this damping valve V
A radial hole 31 is formed in the portion in which is embedded as in the first embodiment.

Further, an axial hole 27 is formed in the piston P from the bottom side chamber 10 side, and this axial hole 27 is communicated with the annular recess 51. Further, the piston P is
The assembly hole 53 is formed and the assembly hole 5 is formed.
3 is communicated with the axial hole 27 through the communication hole 54. Then, the check valve 50 is incorporated in the assembly hole 53.

In the second embodiment as described above, when the piston P moves to the left in the figure and the pressure in the rod side chamber 9 rises, the working oil in the rod side chamber 9 is changed from the communication hole 55 to the groove 45.
→ Inside the casing 35 → exhaust port 41 → radial hole 31 → annular recess 51 → guided to the bottom side chamber 10 via the axial hole 27. If the hydraulic oil that has passed through the groove 45 of the damping valve V is guided to the bottom side chamber 10 through such a route, the flow resistance on the downstream side of the groove 45 can be suppressed to be small. Therefore, the damping characteristic set by the shape of the valve body 36 of the damping valve V and the diameter of the communication hole 28 can be obtained.

On the other hand, when the piston P moves rightward, the check valve 50 opens due to the high pressure in the bottom chamber 10. Therefore, the pressure oil in the bottom side chamber 10 is
It is guided to the rod side chamber 9 through the axial hole 27, the communication hole 54, and the check valve 50. And, in this case, the damping force is not exerted.

In the first and second embodiments described above, the assembly hole 26 in which the damping valve V is incorporated is provided with the annular recesses 29 and 3.
Although it is communicated with the axial hole 27 through 0, 51,
The assembly hole 26 and the axial hole 27 may be communicated with each other by a partially provided recess. However, as in the above-described embodiment, forming the recessed portion in an annular shape simplifies the processing and reduces the flow resistance.

In the first and second embodiments described above, the damping valve V previously assembled using the casing 35 is incorporated in the assembly hole 26.
5 may be omitted, and the valve body 36, the spring 38, and the like may be directly incorporated into the assembly hole 26. Further, in the first and second embodiments, the adjustment bolt 39 of the damping valve V is used.
A notch 56 is formed in the notch 5
6 is not an essential component.

[0040]

According to the first aspect of the present invention, when the damping valve is opened, the pressure oil in the chamber on the high pressure side is passed from the assembly hole incorporating the pressure reducing valve through the recess and the axial hole to the low pressure side. It is possible to suppress the flow resistance on the downstream side of the damping valve. Therefore, it is possible to obtain a damping force according to the shape of the valve body of the damping valve and the diameter of the communication hole.

According to the second aspect of the invention, the recess communicating with the assembling hole is formed annularly on the outer circumference of the piston, so that the machining can be simplified. Further, since the flow passage area is increased by forming the annular recess, the flow resistance can be further reduced.

According to the third invention, since the assembly hole of the valve block incorporating the damping valve is communicated with the tank through the lateral hole, the pressure oil in the high pressure side chamber is opened when the damping valve is opened. It can be discharged to the tank side through the lateral hole.
Therefore, the flow resistance on the downstream side of the damping valve can be suppressed to be small, and a damping force can be obtained according to the shape of the valve body of the damping valve and the diameter of the communication hole.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a first embodiment.

FIG. 2 is an enlarged sectional view of FIG.

3 is a sectional view taken along line III-III in FIG.

4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a partial cross-sectional view of the second embodiment.

FIG. 6 is a sectional view of a conventional example.

FIG. 7 is an enlarged cross-sectional view of a conventional example.

[Explanation of symbols]

B valve block P piston V damping valve 1 cylinder tube 9 Rod side chamber 10 Bottom side chamber 26 Assembly hole 27 Axial hole 29 First annular recess 30 Second annular recess 34 Horizontal hole 51 annular recess

Claims (3)

[Claims] 1. A cylinder tube, a piston incorporated in the cylinder tube, two chambers defined by the piston, an assembly hole formed in the piston and communicating one chamber with the other chamber, A damping device having a damping valve incorporated in this mounting hole, wherein when the damping valve is opened by the movement of the piston, a damping force corresponding to the throttle opening is exerted. And an axial hole formed in the axial direction that communicates with the concave portion and that is open to the outer periphery.When the damping valve is opened, the pressure oil in the high pressure side chamber is discharged from the assembly hole into the concave portion and the axial line. A shock absorber characterized by being configured to be guided to a low-pressure side chamber via a direction hole. 2. The shock absorber according to claim 1, wherein a recess communicating with the mounting hole is formed in an annular shape on the outer circumference of the piston. 3. A valve block incorporated in one chamber side of a cylinder tube, an assembly hole formed in this valve block and communicating any one chamber with a tank, and a damping valve incorporated in this assembly hole. The shock absorber according to claim 1 or 2, further comprising: a horizontal hole that connects the assembly hole and the tank to each other in the valve block.