JPH11101138A - Engine braking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve engine braking performance in a medium speed area by providing a pressure reducing means at an intermediate part of a hydraulic path leading to a piston from an oil pressure generating means for generating an oil pressure corresponding to the engine speed in a device for pressing a piston against an energizing means by the oil pressure to lift an exhaust valve. SOLUTION: An operation switching valve 2 and a brake unit constituting an engine braking device are connected by a hydraulic piping, and the operation switching valve 2 is connected to an oil pressure generating means (oil pump). The brake unit is so constituted that an exhaust valve is moved downward against energizing means by the downward motion of a release piston by an oil pressure so as to be slightly lifted from a valve seat. The operation switching valve 2 consists of a pressure reducing part 80 for reducing the high oil pressure from the oil pump, and a switching part 81 for selectively supplying the reduced oil pressure to the brake unit. The pressure reducing part 80 is provided with a spool valve element 85 enlarging a pressure reducing rate in proportion to the increase of the engine speed or a generated oil pressure value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine brake device for releasing a compression pressure in a cylinder of an engine to increase an engine braking force.

[0002]

2. Description of the Related Art Recently, various engine brake devices have been proposed which increase an engine braking force by lifting an exhaust valve or a dedicated valve when an engine brake is used and releasing a compression pressure in a cylinder of the engine. ing. Of these, the normally open type engine brake device keeps the valve in a slightly lifted position when the braking force needs to be increased so that the compression pressure is released from the cylinder over the entire cycle. .

[0003]

By the way, the present applicant has previously proposed a variable lift normally-open type engine brake device capable of changing the valve lift according to the engine speed (Japanese Patent Application No. 9-12928). issue). According to this, the valve lift amount can be optimized in accordance with the engine speed, and the braking force can be increased in all rotation ranges.

In this device, the oil pressure generated by an oil pump of an engine is directly supplied to a release piston, and the release piston pushes a valve to lift the valve. Since the oil pump generates a high oil pressure as the engine speed increases, the valve lift also increases as the engine speed increases. The release piston is given a reverse biasing force by a return spring (biasing means),
The stroke of the release piston is determined by the balance between the urging force and the hydraulic pressure, and the valve lift is also defined.

On the other hand, in this device, the high oil pressure generated by the oil pump is directly supplied to the release piston. Therefore, in order to obtain an appropriate valve lift and piston stroke in accordance with the engine speed, a relatively long and powerful stroke is required. A return spring must be used. However, in this device, a brake unit having a release piston and a return spring is mounted on the upper part of the exhaust valve, and the mounting position is a limited space of a valve operating chamber of the engine. If there is a restriction on the layout, such as when the height of the chamber (the total height of the engine) cannot be increased, the return spring may not be manufactured as a result.

The oil pump is usually provided with a relief valve for restricting the discharge pressure. However, the above device directly picks up the operating point of the relief valve and stabilizes the optimum lift amount for each engine rotation. However, there is a disadvantage that a sufficient engine braking force cannot be obtained particularly in a medium speed range.

[0007]

According to the present invention, there is provided an urging means for urging the piston by hydraulic pressure to lift the exhaust valve and for urging the piston in the opposite direction to regulate the lift amount. In the engine brake device, a hydraulic pressure generating means for generating a hydraulic pressure according to the engine speed is provided, and a pressure reducing means for reducing the hydraulic pressure generated by the hydraulic pressure generating means is provided in a hydraulic path from the hydraulic pressure generating means to the piston. It is provided.

According to this, since the oil pressure supplied to the release piston is reduced by the pressure reducing means, the pushing force of the release piston is weakened, and a weak urging means can be used.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The engine brake device according to the present invention comprises a brake unit 1 shown in FIGS. 1 and 2 and a brake unit 1 shown in FIGS.
And an operation switching valve 2 shown in FIG. The brake unit 1 and the operation switching valve 2 are connected by hydraulic piping, and the operation switching valve 2 is connected to hydraulic pressure generating means (not shown). 1 and 3 show a state during operation when engine braking is requested, and FIGS. 2 and 4 show a state during normal non-operation. The brake unit 1 is provided one by one for each cylinder of the engine, in particular, in the valve operating chamber of the engine. The operation switching valve 2 is connected to these brake units 1
Supply hydraulic pressure collectively.

Here, as the oil pressure generating means, an oil pump usually provided in the engine is used, which is driven in conjunction with the engine to generate an oil pressure of a value corresponding to the engine speed and to compare the oil pressure. The high-pressure lubricating engine oil is supplied to the operation switching valve 2 in addition to the sliding portions of the engine. That is, the oil pump generates a high oil pressure as the engine speed increases.

As shown in FIG. 1, the brake unit 1 has a release piston 3 (piston). Referring also to FIG. 5, the push rod 4 and the exhaust valve 5 of the engine are coaxially arranged below the release piston 3. When the release piston 3 is pressed downward by receiving the hydraulic pressure, the exhaust valve 5 is moved downward via the push rod 4 and slightly lifted with respect to the valve seat 6.
Conversely, if the release piston 3 rises due to the stop of the hydraulic pressure supply,
The exhaust valve 5 is pushed up by the valve spring 7 and sits on the valve seat 6 as shown by the imaginary line in FIG. 5 to close the exhaust port.

As described above, the exhaust valve 5 is interlocked with the release piston 3. On the other hand, since the exhaust valve 5 needs to be opened and closed at regular valve timing, the following structure is employed. That is, the push rod 4 is slidably inserted into the sleeve 8, and the sleeve 8 is screwed into the valve bridge 9 and then the nut 1
It is fixed at 0. Since the valve bridge 9 is driven by the cam via the rocker arm, the sleeve 8 pushes the umbrella portion 11 at the lower end of the push rod 4 only when the sleeve 8 is lowered, so that the exhaust valve 5 is lowered. In this case, the descending amount or the lift amount is considerably larger than that by the release piston 3, so that the exhaust valve 5 is preferentially lowered by the cam, and is lifted by a regular amount irrespective of the operation of the release piston 3. . At this time, the release piston 3 and the push rod 4 are separated. Only when the valve bridge 9 is in the raised position, a minute lift of the exhaust valve 5 based on the lowering of the release piston 3 becomes possible.

As shown in FIG. 1, a cylinder hole 13 is formed in the housing 12 of the brake unit 1 along the vertical direction for slidably housing the release piston 3. A return spring 14 as an urging means for urging the release piston 3 upward (toward the hydraulic chamber 19) is inserted into the cylinder hole 13. The return spring 14 is made of a coil spring, and its spring constant is set smaller than that of the conventional one (Japanese Patent Application No. 9-12928).

A bottomed cylindrical spring receiver 15 is screwed into a lower end of the cylinder hole 13, and a lock nut 16 is provided.
It is fixed at. The reaction force of the return spring 14 is received by the spring receiver 15. The release piston 3 is formed to have a substantially T-shaped cross section, and is configured such that a small-diameter shaft-like portion 18 is integrally extended downward from a large-diameter sliding portion 17. In particular, the shaft portion 18 is formed in the center hole 1 of the spring receiver 15.
The push rod 4 is inserted into the push rod 4 with a gap, and is pressed against the upper end surface of the push rod 4.

The release piston 3 has a hydraulic chamber 1 above it.
A leak hole 20 (leak passage) for allowing oil to leak from 9 is provided. The leak hole 20 is continuous with a vertical hole 21 extending along the axis of the release piston 3 and a horizontal hole 22 extending radially outward from the lower end of the vertical hole 21.
The upper end of the vertical hole 21 opens into the hydraulic chamber 19, and the left and right ends of the horizontal hole 22 communicate with the outside (inside the cylinder head) on the leak side through a gap with the center hole 15a.

The upper end wall 2 which defines the upper end of the cylinder hole 13
3 is provided with a through hole 24 having a female screw, a stopper bolt 25 is screwed to a predetermined position, and a nut 26
The position is fixed by. The stopper bolt 25 has a hole 27 at the upper end for inserting a tool, and a hollow hole 28 is formed from a lower end to a predetermined distance above. A return spring 29 is inserted into the hollow hole 28 from above.
(Spring) and a check pin 30 (closing member) are provided, and the check pin 30 is urged by the return spring 29 and pushed downward. A stop ring 31 (a regulating member) is provided on the inner side wall of the hollow hole 28.
And the stop ring 31 is
It restricts the downward movement of zero. Check pin 30 here
Is a small-diameter fitting portion 32 for fitting the return spring 29, a flange portion 33 that forms a seating surface for the return spring 29 and also serves as a contact portion with the stop ring 31, and a lower portion from the flange portion 33. It extends and comes into contact with or is pressed against the upper end surface of the release piston 3, and is formed integrally with a large-diameter plug portion 34 capable of closing the leak hole 20.

Since there is a radial gap between the check pin 30 and the stop ring 31, the inside of the hollow hole 28 and the inside of the cylinder hole 13 communicate with each other. A hydraulic chamber 19 is defined by the wall 23, the inner wall of the cylinder hole 13, and the inner wall of the hollow hole 28, and the hydraulic pressure sent from the operation switching valve 2 is introduced into the hydraulic chamber 19. A control hole 35 communicates with the upper end of the cylinder hole 13 from the side, and the supply and discharge of hydraulic pressure is controlled by a hydraulic supply control mechanism provided in the control hole 35.

The control hole 35 extends laterally from the cylinder hole 13 and has a terminal open to the outside. And control hole 35
The diameter of the control sleeve 3 is reduced stepwise toward the cylinder hole 13 side.
6, a spacer 37 and a lock screw 38 are provided. The control sleeve 36 and the spacer 37 are fixed by being pressed against the cylinder hole 13 by tightening the lock screw 38.

In the control sleeve 36, a ball 40, a ball spring 41, and a ball retainer 42 constituting the check valve 39 are arranged at one end on the cylinder hole 13 side. The ball 40 is used to open and close the orifice hole 43 formed in the control sleeve 36 from the cylinder hole 13 side. The ball spring 41 urges the ball 40 toward the orifice hole 43, and the ball retainer 42 is locked by the control sleeve 36 and functions as a receiving member for the ball spring 41. The ball retainer 42 allows oil to pass through a slit (not shown).

A control piston 44 is slidably mounted on the other end side of the control sleeve 36. The control piston 44 uses a pin portion 45 at its tip to insert the ball 40 into the orifice hole 43.
, The check valve 39 can be opened (see FIG. 2). The control piston 44 has a spring 47 in a sliding portion 46 at the base end thereof, and the spring 47 urges the control piston 44 toward the ball 40, that is, in the valve opening direction. Air holes 4 are formed in the spacer 37 and the lock screw 38.
8, 49 are provided, and the inflow and outflow of air accompanying the movement of the control piston 44 are allowed.

The control sleeve 36 is provided inside the control room 5.
A plurality of communication ports 36a are provided at predetermined intervals in the circumferential direction in order to introduce oil into the control hole 35.
A peripheral groove 51 that communicates all of the grooves 6a is provided. Further, a hydraulic passage 52 having one end communicating with the circumferential groove 51 is provided inside the housing 12, and the other end of the hydraulic passage 52 communicates with an internal passage 54 of the pipe joint member 53. The pipe joint member 53 is composed of an eye 53a and an eye bolt 53b.
a is connected to one end of a hydraulic pipe 55 (see FIG. 3), and is connected to the operation switching valve 2 via the hydraulic pipe 55. That is, the pipe joint member 53 forms an inlet / outlet for hydraulic pressure in the brake unit 1.

As shown in FIG. 3, in the operation switching valve 2, one pipe joint member (outlet side pipe joint member) 56a is connected to a hydraulic pipe 55 leading to the brake unit 1, and the other pipe joint member (inlet port). The side joint member 56b is connected to a hydraulic pipe 57 leading to an oil pump. These pipe joint members 56a and 56b are attached to the valve body 58 from above and below respectively. These pipe joint members 56
Similarly, a and 56b are composed of an eye and an eyebolt.

Here, the operation switching valve 2 comprises a pressure reducing section 80 and a switching section 81. The pressure reducing unit 80 reduces the high oil pressure generated by the oil pump, and the switching unit 81 selectively supplies the reduced oil pressure to the brake unit 1.

The pressure reducing section 80 is configured as follows. A fitting hole 82 is provided in the valve body 58, and a sleeve body 83 is tightly fitted in the fitting hole 82. Sleeve body 8
Reference numeral 3 denotes a stop ring 84 for restricting the movement in the axial direction. A spool valve body 85 is provided inside the sleeve body 83 so as to be slidable in the axial direction. A passage hole 7 communicating with the internal passage 71 of the inlet-side pipe joint member 56b is formed in the valve body 58.
The outlet of the passage hole 73 is communicated with the inlet port 86 of the sleeve body 83. The inlet port 86 introduces the hydraulic pressure sent from the oil pump into the hydraulic working chamber 87 inside the sleeve body 83. In the hydraulic working chamber 87, the introduced hydraulic pressure acts on the pair of piston portions 88 a and 88 b of the spool valve body 85, causing the spool valve body 85 to move in the axial direction. Usually, the spool valve element 85
It is urged by a return spring 89 to the right in the figure.

In particular, one of the pair of piston portions 88a, 88b shown on the right side is inserted into the outlet hole 90 of the sleeve body 83 with a slight gap. Accordingly, this gap becomes the throttle outlet 91, and the hydraulic pressure introduced into the hydraulic working chamber 87 is reduced and discharged. The discharged oil is supplied to the communication hole 9 in the valve body 58.
2 to the switching unit 81. The other piston portion 88a slides in close contact with the inner surface of the sleeve 83 as in a normal piston.

The operation of the pressure reducing section 80 is as shown in FIG. In the lower part of the figure, the generated oil pressure in the oil pump is shown in relation to the engine speed. In this case, the generated oil pressure is increased in proportion to the engine speed, which has a stepped characteristic as shown in FIG. This will be described later. As can be seen from the figure, the spool valve element 85 is moved to the left as the engine speed increases. This is because the pressure receiving surface of the left piston portion 88b is larger than the pressure receiving surface of the right piston portion 88a. As the engine speed increases, the axial length L of the throttle outlet 91 increases and the passage resistance increases. this is,
The higher the engine speed or the higher the generated oil pressure value, the greater the pressure reduction ratio in the pressure reduction unit 80. That is, the pressure reducing unit 80 performs a small pressure reduction when the generated oil pressure value is small, and performs a large pressure reduction when the generated oil pressure value is large.

Next, the configuration of the switching unit 81 will be described. As shown in FIG. 3, a mounting hole 60 for mounting a control unit 59 is provided in the valve body 58, and the mounting hole 60 has a female thread portion 60a at the right end thereof.
Are screwed together and mounted. The housing 61 is provided with a control hole 62 on the left side.
The solenoid 63 is housed in the exposed portion on the right side. A spool 64 is slidably mounted in the control sleeve portion 62, and the spool 64 is urged toward the solenoid 63 by a spring 65. Spool 64
On the side of the solenoid 63, a rod 66 surrounded by the solenoid 63 is disposed. When the solenoid 63 is excited, the rod 66 moves to the left as shown in FIG.

At this time, the spool 64 compresses the spring 65 and stops, so that the hydraulic pressure inlet 68 and the hydraulic pressure outlet 69 of the control sleeve portion 62 communicate with each other on the outer peripheral side of the reduced diameter portion 70. In this case, as shown in FIG.
The passage hole 74 communicating with the internal passage 72 of 6 b communicates with the passage hole 74, whereby the hydraulic pressure sent from the pressure reducing unit 80 is sent to the brake unit 1.

The spool 64 is provided with a small-diameter throttle hole 93. The throttle hole 93 communicates with the passage hole 74 through the oil discharge port 94 of the control sleeve portion 62 in the above state. Therefore, a part of the oil leaks through the throttle hole 93 and the hydraulic pressure reduced by the pressure reducing unit 80 is applied to the brake unit 1.
The pressure is further reduced before being sent to. However, the degree of pressure reduction at this time is smaller than that in the pressure reduction unit 80. As a result, as shown in the upper part of FIG. 6, the hydraulic pressure value supplied to the brake unit 1 is significantly lower than the generated hydraulic pressure value of the oil pump, and the rising gradient with respect to the engine speed is also extremely small. As described above, here, the pressure reducing section 80 and the throttle hole 93 constitute the pressure reducing means of the present invention for performing the pressure reduction or pressure regulation as described above.

The oil leaked from the throttle hole 93 passes through the spool 64 and the internal space of the control sleeve portion 62, and is then discharged from a leak hole 75 formed in the end wall 67 of the control sleeve portion 62, and a leak oil reservoir 95. Is returned to an oil tank (not shown) through a pipe nipple 96.
Here, the oil leaking into the leak oil sump 95 is
7. The oil is supplied to the spring chamber 99 of the pressure reducing section 80 through the oil supply port 98, and is used for lubrication as appropriate. The oil discharge port 94 and the hydraulic outlet 69 of the control sleeve 62 are communicated with each other by a circumferential groove formed on the outer periphery of the control sleeve 62.

On the other hand, as shown in FIG.
Is stopped, the pressing force of the rod 66 is lost, so that the spool 64 is pushed by the spring 65 and moves to the right. In this case, the outer peripheral side of the reduced diameter portion 70 communicates only with the hydraulic pressure inlet 68 and is cut off from the hydraulic pressure outlet 69.
On the other hand, when the spool 64 is disengaged to the right, the oil discharge port 94 and the leak hole 75 communicate with each other. Therefore, when the excitation of the solenoid 63 is stopped, the oil flows backward from the brake unit 1 side as shown by the arrow and returns to the oil tank along the same route as before. At this time, oil pressure is supplied from the oil pump,
Since this stops at the outer peripheral side of the reduced diameter portion 70 of the spool 64, the substantial supply of hydraulic pressure is completely stopped.

Incidentally, in the above configuration, the solenoid 63 is electrically connected to a controller (for example, an ECU) not shown. The controller always receives various signals indicating the engine operating state, such as the engine speed, the TDC signal of each cylinder, the clutch engagement / disconnection signal, and the coolant temperature. Further, the controller activates the engine brake device based on a signal of a manual switch provided in the vehicle interior. Specifically, when the manual switch is turned ON, the controller outputs the excitation electromotive force to the solenoid 63 at a predetermined timing.

The operation of the engine brake device according to the above configuration is as follows. First, when a manual switch is turned ON to start the apparatus, the reduced or regulated hydraulic pressure is supplied to the brake unit 1 through the operation switching valve 2. As shown in FIG. 1, the supplied hydraulic pressure reaches the inside of the control chamber 50 and moves the control piston 44 backward (moves to the right) until the control piston 44 hits the spacer 37. At the same time, the ball 40 moves forward (left side) against the ball spring 41. To).
Thus, the check valve 39 is opened, and the oil flows into the hydraulic chamber 19 through the orifice hole 43. When this happens, the oil pressure in the hydraulic chamber 19 increases, and the release piston 3 descends during opening of the exhaust valve 5 at the regular valve timing, so that the exhaust valve 5 is lifted immediately before sitting.

In particular, the lift amount at this time depends on the hydraulic chamber 19.
And the urging force of the return spring 14. That is, the lift amount (stroke in the descending direction) of the release piston 3 and the exhaust valve 5 changes according to the oil pressure value in the oil pressure chamber 19, and the compression amount of the return spring 14 increases as the engine speed increases and the oil pressure value increases. The lift amount of the release piston 3 and the exhaust valve 5 increases.

In the prior art (Japanese Patent Application No. 9-12928), the return spring has a large spring constant and can be compressed only at a high oil pressure corresponding to the gallery pressure. The constant is small, and the lift or lift amount can be controlled with the small hydraulic pressure as described above. This is a remarkable difference from the related art.

Now, with the supply of hydraulic pressure, the check pin 3
0 is also pushed downward by the hydraulic pressure and the return spring 29, so that the check pin 30 closes the leak hole 20,
It follows the release piston 3 and descends. Then, when the release piston 3 stops at a predetermined lift amount according to the oil pressure value, the check pin 30 holds the leak hole 20 in a closed state, and at the same time, holds the release piston 3 at the lift position.

On the other hand, when a high oil pressure is supplied and the lift amount of the release piston 3 is increased to some extent, the lower portion of the check pin 30 causes the flange portion 33 to come into contact with the stop ring 31 soon. In this case, the lowering of the check pin 30 is restricted, and the check pin 30 cannot follow the release piston 3 and cannot be lowered. Therefore, even if the release piston 3 is further lowered by hydraulic pressure, a gap is formed between the release piston 3 and the check pin 30 and oil leaks from the clearance through the leak hole 20. 3 is stopped or limited. After all, the release piston 3
As shown in FIG. 1, the check pin 30 is lowered only to the position where it comes into contact with the stop ring 31, whereby the maximum lowering amount of the release piston 3 and the maximum lift amount of the exhaust valve 5 are limited to a certain amount.

Since the oil pressure in the hydraulic chamber 19 acts on the ball 40 to close the orifice hole 43, backflow of the oil is prevented, and the pressure in the hydraulic chamber 19 is reliably maintained.

On the other hand, the manual switch is turned off to stop the device.
F, the operation switching valve 2 is controlled by the controller as shown in FIG.
It can be switched like In this case, the oil is leaked from the operation switching valve 2, so that the oil flows backward, that is, is discharged from the brake unit 1.

At this time, as shown in FIG. 2, first, the pressure in the control chamber 50 decreases, so that the control piston 44 is pushed forward by the spring 47 and eventually pushes the ball 40 to open the orifice hole 43. become. When this happens, oil is discharged from the hydraulic chamber 19 to the control chamber 50, whereby the release piston 3 rises until it hits the stopper bolt 25. Also at this time, the check pin 30 rises following the release piston 3 while closing the leak hole 20. As a result, the release piston 3 separates from the push rod 4 and does not transmit the descending force to the exhaust valve 5, so that the exhaust valve 5
Ends the minute lift for increasing the engine braking force and is lifted at the regular valve timing.

In the above configuration, while the oil pump generates a hydraulic pressure according to the engine speed,
The hydraulic pressure is reduced at a predetermined rate, and the lift amounts of the release piston 3 and the exhaust valve 5 are changed based on the reduced hydraulic pressure value. Although the point that the engine braking force can be optimized for each engine speed by the variable lift of the exhaust valve 5 has been described above, here, in particular, the oil pressure generated by the oil pump is reduced and supplied to the release piston 3. ,
A weak return spring 14 can be used. As a result, the conventional problem can be solved, the return spring 14 can be manufactured, and the overall height of the device (brake unit 1) is reduced, so that the device can be mounted in a limited narrow space.

FIG. 7 shows the control hydraulic pressure characteristics of the present apparatus, that is, the oil pressure generated by the oil pump P _P (dashed line) with respect to the engine speed, and the supply oil pressure to the release piston 3, ie, the control oil pressure P.
_C (solid line) is shown. As can be seen, the hydraulic pressure generated P _P As increase in the engine speed increases, also increases the control pressure P _C and following this. The smaller vacuum percentage is larger the higher the engine speed, increase gradient of the control pressure P _C is the hydraulic pressure generated P _P ones. Here the engine speed N _E0 is in relief operation point of the oil pump, the rising slope of the time the hydraulic pressure generated P _P changes abruptly. In a conventional device for the hydraulic pressure generated P _P and the control oil pressure, but optimization of the valve lift amount is not Hakare well picking up an abrupt change of the rising slope directly obtained substantially linear characteristic is alleviated sudden change in this system As a result, the valve lift can be further optimized.

The variable lift characteristics, i.e., the lift amount L _P and lift L _V of the exhaust valve 5 for releasing the piston 3 to the engine rotational speed is shown in FIG. Incidentally lift L _V of the exhaust valve 5, the lift amount L _P release piston 3, which is a value obtained by subtracting the gap between the release piston 3 and the push rod 4. As can be seen, each lift as the increase in the engine speed L _P, L _V has risen. Here, there is a stepped characteristic in each of the lift amounts L _P and L _V near the engine speed N _E0 , which is due to the lift amount L in the first place.
_Since the absolute values of _P and L _V are small values, there is no practical problem.

FIG. 9 shows a compression brake cycle curve.
That is, the present invention (solid line) and the conventional one (Japanese Patent Application No. 9-12928, broken line) when the engine speed is constant (here, 2000 rpm).
(So-called PV diagram) between the in-cylinder pressure and the stroke volume. According to the present invention, since the lift amount of the exhaust valve 5 is optimized, a choke is more easily generated in the gap (valve gap) between the exhaust valve 5 and the valve seat 6 than in the related art. As a result, the in-cylinder pressure increases and the diagram area also increases, so that a large compression braking force can be obtained.

FIG. 10 shows the compression brake performance characteristics, that is, the present invention (solid line) and the prior art (Japanese Patent Application No.
No. 12928, broken line) and the engine braking force according to the present invention (dashed line). Note that the friction average effective pressure is with respect to the flywheel axis. As can be seen from the above, in the present invention, the friction average effective pressure is higher in the whole rotation range than in the past, and a remarkable improvement is seen particularly in the low and middle rotation ranges, and the practicality is improved. In general, the exhaust braking force is reduced in the low-to-medium rotation range, and this device can sufficiently compensate for this. In the high speed range, the braking force can be easily obtained due to an increase in mechanical loss and the like (see FIG. 10). Is not necessarily.

FIG. 11 shows the compression brake horsepower characteristics, that is, the flywheel friction horsepower of the present invention (solid line) and the conventional (dashed line) for each engine speed. The engine braking force according to the present invention (dashed line) is also shown. As can be seen, the brake horsepower has been improved, especially in the low to medium speed range.

In this apparatus, the lift amount of the release piston 3 and the exhaust valve 5 can be limited to a predetermined amount by opening the leak hole 20 of the release piston 3 with the check pin 30. For this reason, when the engine overruns, the release piston 3 jumps or bounces.
Of the exhaust valve 5 and the piston can be prevented from colliding with each other. Conversely, the maximum lift amount of the exhaust valve 5 can be set freely within a range where such a collision does not occur.

Further, in the present apparatus, even when air enters the hydraulic path and reaches the hydraulic chamber 19, the check pin 30 opens the leak hole 20 so that the check pin 30 opens the leak hole 20.
The mixed air can be discharged together with the oil. Accordingly, air entrapment can be prevented, and when the apparatus is stopped, that is, when it is not operating, it is not necessary to perform low-pressure oil pressure feeding for preventing air entrapment.

In particular, since the control hydraulic pressure and the supply hydraulic pressure are reduced in the present apparatus, the amount of oil leaking when the apparatus is stopped can be reduced, and the oil consumption can be suppressed. In addition, the leak oil amount can be reduced even when the above-described leak hole 20 is opened, and the valve opening function can be stably performed.

Although the embodiment according to the present invention has been described above, the present invention can adopt various other embodiments, and the dimensions, arrangement, positional relationship, and the like of each component can be appropriately changed. . Further, in the above-described embodiment, the configuration for driving the exhaust valve of the engine has been described. However, this may be a device for driving another exhaust valve provided exclusively (so-called dedicated valve or third valve). The invention includes this.

[0052]

In summary, the present invention exhibits the following excellent effects.

(1) The urging means can be manufactured, and the device can be mounted in a limited narrow space.

(2) The braking performance in the low to medium speed range is improved.

(3) Oil consumption can be suppressed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a brake unit of an engine brake device according to the present invention and showing a state at the time of operation.

FIG. 2 is a longitudinal sectional view showing a state where the brake unit is not operated.

FIG. 3 is a longitudinal sectional view showing a state when the operation switching valve is operated.

FIG. 4 is a longitudinal sectional view showing a state when the operation switching valve is not operated.

FIG. 5 is a longitudinal sectional view showing a structure around an exhaust valve.

FIG. 6 is a diagram for explaining the operation of the pressure reducing unit.

FIG. 7 is a graph showing control hydraulic pressure characteristics.

FIG. 8 is a graph showing a variable lift characteristic.

FIG. 9 is a graph showing a compression brake cycle curve.

FIG. 10 is a graph showing compression brake performance characteristics.

FIG. 11 is a graph showing compression brake horsepower characteristics.

[Explanation of symbols]

3 release piston 5 exhaust valve 14 return spring 80 vacuum unit 93 throttle hole P _C control pressure P _P generated hydraulic

Claims (1)

[Claims] 1. An engine brake device having an urging means for urging a piston by hydraulic pressure to lift an exhaust valve and urging the piston in a reverse direction to regulate the lift amount. An engine provided with a hydraulic pressure generating means for generating a hydraulic pressure corresponding to the pressure, and a pressure reducing means for reducing the hydraulic pressure generated by the hydraulic pressure generating means in a hydraulic path from the hydraulic pressure generating means to the piston. Brake device.