JPH0350295Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a negative brake device that applies braking force to the cylinder body of a hydraulic motor.

BACKGROUND ART A conventional negative brake device includes, for example, a brake plate attached to the inner periphery of a case of a hydraulic motor and the outer periphery of a rotating cylinder body.
A spring that presses these brake plates into contact with each other via a piston and applies a braking force to the cylinder body, and a passage that selects high-pressure liquid in the drive line and guides it to the piston and retracts the piston from the brake plate against the spring. It is known that it has the following.
Incidentally, in recent years, in order to improve the performance of hydraulic motors, the hydraulic pressure supplied to the cylinder body has been increased, and the component parts of the motor have been made thinner and smaller. For this reason, there is a problem that, for example, the piston is distorted by the high-pressure liquid supplied from the passage, reducing smoothness of movement. Furthermore, the sealing performance of the O-ring attached to the outer periphery of the piston deteriorates as the hydraulic pressure increases and the piston deforms, so there is a problem in that an expensive back-up spring must be used.

Problems to be solved by the invention This invention solves the conventional problems that the piston does not move smoothly and the device is expensive.

Means to solve the problem This kind of problem can be solved by intervening in the middle of the passage,
A pressure reducing valve that shuts off the passage when the internal pressure of the passage reaches a predetermined pressure, and a pressure reducing valve that is interposed in parallel with the pressure reducing valve in the middle of the passage, and goes from the passage on the piston side of the pressure reducing valve to the passage on the drive line side of the pressure reducing valve. A check valve that allows only the flow of liquid, and a relief valve that is interposed in the passage between the pressure reducing valve and the piston and that operates when the internal pressure of the passage reaches a constant pressure that exceeds the predetermined pressure, This problem can be solved by housing the check valve and the relief valve facing each other in the spool of the pressure reducing valve.

Function First, when the hydraulic motor is operated, high-pressure liquid in the drive line is caused to flow into the cylinder body to rotate the cylinder body, and this rotational force is taken out to the outside. High pressure fluid in the drive line is then directed through selected back passages to the piston, retracting the piston from the brake plate against the spring. The pressure of the liquid guided to the piston at this time is controlled by a pressure reducing valve inserted in the middle of the passage.
When the internal pressure of the passage reaches a predetermined pressure, the passage is shut off, thereby limiting the pressure to a predetermined pressure, and as a result, distortion of the piston can be reduced as much as possible. Note that when a hydraulic motor is operated for a long time, the hydraulic pressure acting on the piston gradually increases due to leakage in the pressure reducing valve, but when that pressure reaches a constant pressure, the relief valve discharges the hydraulic pressure in the passage. , the passage is returned to the predetermined pressure again. Then, when the hydraulic motor is deactivated, the pressure in the drive line decreases, which also reduces the pressure acting on the piston. As a result, the piston presses the brake plates into contact with each other due to the biasing force of the spring, and applies a braking force to the cylinder body. At this time, the check valve opens and the liquid pushed out by the piston is quickly released. Here, since the check valve and the relief valve are housed in the spool of the pressure reducing valve facing each other as described above, they can be placed in separate locations, for example, the relief valve in the spool and the check valve in the casing of the pressure reducing valve. These check valves can be made smaller compared to the case where they are stored, and
The passage for the relief valve can also be shortened and easily formed.

Embodiment Hereinafter, an embodiment of this invention will be described based on the drawings.

In FIG. 1, reference numeral 1 denotes a swash plate type axial piston type hydraulic motor as a hydraulic motor, and this hydraulic motor 1 is used, for example, as a traveling drive source for a crawler vehicle. In this hydraulic motor 1, an output shaft 4 and a cylinder body 5 are supported by a fixed case 2 via bearings 3 so as to rotate together, and a plurality of cylinder chambers 6 of the cylinder body 5 are provided with reciprocating motion in the axial direction. A piston 7 is inserted.
The tips of these pistons 7 are in sliding contact with a swash plate 9 supported by the case 2 via a shoe 8. A timing plate 10 controls the timing of supply of pressure oil to the cylinder chamber 6, and a pair of supply/discharge ports 11 and 12 are connected to the timing plate 10. A control valve 13 is connected to a high pressure oil source and a low pressure source (not shown), and the control valve 13 and the supply/discharge ports 11, 12 are connected by a pair of supply/discharge passages 14, 15. , among these supply and discharge passages 14 and 15,
The side through which high-pressure oil flows is the drive line. A brake plate 2 movable in the axial direction is provided on the inner periphery of the case 2.
1 is spline-coupled, and a brake plate 22 movable in the axial direction is also spline-coupled to the outer periphery of the cylinder body 5. And these brake plates 2
1 and 22 overlap each other and can contact each other. A piston 23 is housed in a cylinder chamber 24 formed between the case 2 and the cylinder body 5 so as to be movable in the axial direction. A spring 25 transmits its biasing force to the brake plates 21 and 22 via the piston 23 and presses the brake plates 21 and 22 into contact with each other. The above-mentioned brake plates 21, 2
2, the piston 23 and the spring 25 collectively constitute a parking brake 26 as a negative brake. Check valves 32 and 33 are interposed at both ends of the selection path 31 that connects the supply and discharge passages 14 and 15, allowing flow only toward the center. High pressure oil in the drive line is supplied after selection. The central part of the selection path 31 and the cylinder chamber 2
4 is connected by a passage 34, and when high pressure oil is supplied to the cylinder chamber 24 through this passage 34,
The piston 23 is retracted from the brake plates 21 and 22 against the spring 25. A pressure reducing valve 35 that operates at a predetermined pressure is interposed in the middle of the passage 34, and this pressure reducing valve 35 is connected to the casing 3 as shown in FIG.
The spool 38 is housed in a spool chamber 37 of No. 6, and the spool 38 is biased toward one end by a setting spring 40 seated on a spring receiver 39. And this spool 38 is
When the internal pressure of the passage 34 reaches a predetermined pressure, the predetermined pressure acts on the step 41 and the setting spring 40
As a result, the lands 42 and 43 overlap each other, and the first port 44 as a part of the passage 34 communicating with the selection passage 31 and the passage communicating with the cylinder chamber 24 The second port 45 as part of the cylinder chamber 34 is shut off to prevent the pressure in the cylinder chamber 24 from exceeding a predetermined pressure. Inside the spool 38 are the first and second ports 4.
A bypass passage 46 communicating between 4 and 45 is a pressure reducing valve 35.
In the middle of this bypass passage 46, there is a passage 34 on the piston 23 side of the pressure reducing valve 35, that is, the second port 45, and a passage 34 on the drive line side of the pressure reducing valve 35, that is, the first port. A check valve 47 that only allows pressure oil to flow toward 44.
is interposed. A drain passage 48 communicating with the second port 45 is formed in the spool 38, and a part of the drain passage 48 is operated at a constant pressure that is lower than the pressure of the high-pressure oil in the drive line and exceeds the predetermined pressure. A relief valve 49 is interposed between the ball 50 and the adjusting screw 5.
and a setting spring 52 seated at 1. The check valve 47 and the relief valve 49 are housed in the spool 38 facing each other. Further, the pressure oil discharged from the relief valve 49 is returned to the tank 55 through the third port 53 and the return path 54.

Next, the operation of one embodiment of this invention will be explained.

When the hydraulic motor 1 rotates normally, for example, the supply/discharge passage 1
4 forms a drive line, and at this time, the high-pressure oil flows into the cylinder chamber 6 through the timing plate 10 and rotates the cylinder body 5 and output shaft 4 in the forward direction as a unit, while the low-pressure oil The return oil returns to the low pressure source through the supply/discharge passage 15. At this time, the high pressure oil in the supply/discharge passage 14 is checked by the check valve 32.
is pushed open and flows into the passage 34. However, since the pressure of the high-pressure oil flowing into this passage 34 is higher than the predetermined pressure at which the pressure reducing valve 35 operates, when the pressure of the high-pressure oil acts on the step 41, the spool 38 is moved at the other end against the setting spring 40. The first port 44 and the second port 45 are blocked. As a result, the pressure within the passage 34 from the pressure reducing valve 35 to the cylinder chamber 24 is maintained at a predetermined pressure considerably lower than the pressure of the high pressure oil. At this time, the piston 23 receives the predetermined pressure, moves in the axial direction against the spring 25, and retreats from the brake plates 21, 22. As a result, the brake plates 21 and 22 do not come into contact with each other, and no braking force is applied to the cylinder body 5. When such a state continues for a long time, the pressure in the passage 34 gradually increases due to leakage between the lands 42 and 43 of the pressure reducing valve 35. When the pressure in the passage 34 reaches a certain level, the ball 50 of the relief valve 49 is pushed open against the setting spring 52, and the pressure in the passage 34 between the pressure reducing valve 35 and the cylinder chamber 24 is is discharged to the tank 55 via the third port 53 and the return path 54, and the pressure within the passage 34 is returned to the predetermined pressure. Note that when the hydraulic motor 1 is reversed, high pressure oil flows into the supply/discharge passage 15 and becomes the drive line, but the high pressure oil at this time pushes open the check valve 33 and flows into the passage 34, reducing the high pressure of the drive line. will always be selected and supplied to the passage 34.

Next, when the supply of high pressure oil to the hydraulic motor 1 is stopped, the rotation of the cylinder body 5 and the output shaft 4 is stopped. At this time, the pressure oil in the cylinder chamber 24 is returned to the low pressure source through the passage 34 and the bypass passage 46 as the piston 23 is urged by the spring 25 and moves toward the brake plates 21 and 22. At this time, since the check valve 47 is opened, the return speed of the pressure oil is increased. Further, the piston 23 transfers the urging force of the spring 25 to the brake plate 2.
1 and 22, the brake plates 21 and 22 are brought into pressure contact with each other, and a braking force is applied to the cylinder body 5.

Effects of the invention As explained above, according to this invention, the piston can be moved smoothly and the entire device can be made inexpensive. Moreover, the entire device can be made smaller, the passages for the check valve and relief valve can be shortened, and their shapes can also be made simple.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a part of an embodiment of this invention with circuit symbols, and FIG. 2 is a sectional view showing a specific example of section A in FIG. 1. 1... Hydraulic motor (hydraulic motor), 2... Case, 5... Cylinder body, 21, 22... Brake plate,
23...Piston, 25...Spring, 34...
... passage, 35 ... pressure reducing valve, 49 ... relief valve.

Claims (1)

[Scope of utility model registration request] A brake plate is attached to the inner circumference of the case of the hydraulic motor and the outer circumference of the rotating cylinder body, a spring that presses the brake plates into contact with each other via a piston to apply braking force to the cylinder body, and a high-pressure liquid in the drive line. A negative brake device comprising a passageway for selectively guiding the piston and retracting the piston from the brake plate against a spring, wherein the passageway is interposed in the middle of the passageway and when the internal pressure of the passageway reaches a predetermined pressure. a pressure reducing valve that shuts off the flow, and a pressure reducing valve interposed in parallel with the pressure reducing valve in the middle of the passage,
A check valve is provided in the passage between the pressure reducing valve and the piston, and a check valve that allows liquid to flow only from the passage on the piston side of the pressure reducing valve to the passage on the drive line side of the pressure reducing valve, and the check valve is interposed in the passage between the pressure reducing valve and the piston, and the internal pressure of the passage is maintained at the predetermined level. 1. A negative brake device, comprising: a relief valve that operates when a constant pressure exceeds the pressure, and a check valve and a relief valve are housed in a spool of the pressure reducing valve so as to face each other.