JP2738031B2 - Engine brake device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an engine brake device suitable for use in a commercial vehicle such as a truck.

(Prior Art) In a commercial vehicle which travels a long distance by loading a large amount of cargo such as a truck, the load of a service brake device is extremely large, and there is a risk that fading often occurs due to overheating, especially when the vehicle descends on a long slope. There is. Therefore, various engine brake devices have been proposed and put to practical use in order to supplement the service brake device, and as one type, the exhaust valve of each cylinder of the engine is forcibly forced near the compression top dead center. 2. Description of the Related Art A so-called power tard device is known in which an effective engine braking effect is generated by releasing a compressed air supply in a cylinder to an outside, for example, an exhaust pipe.

U.S. Pat.
No. 392 and Japanese Patent Publication No. 61-14335 disclose Jacob-type engine braking devices. The Jacob-type engine brake device is provided with at least one exhaust valve provided in each cylinder of the engine, a rocker arm that opens the exhaust valve of each cylinder in a normal exhaust stroke, and a cylinder which is provided with the same cylinder during engine braking operation. A slave piston forcibly opening the exhaust valve near the top dead center of the pressure contact, and a working fluid pressure is supplied to the slave piston by being driven by a rocker arm of another cylinder having a specific crank angle relationship with respect to the cylinder having the slave piston. A master piston, a fluid circuit device that forms a closed circuit during engine braking operation, interlocks the slave piston with the master piston, and is released to the atmosphere during normal operation of the engine to eliminate the interlocking relationship between the slave piston and the master piston; And the fluid circuit device is open to the atmosphere. And which comprises a leaf spring arrangement to dismiss the rest position not in contact with the rocker arm which cooperates with the master piston when being, the plate spring device is constituted by a conventional all single leaf spring.

(Problems to be Solved by the Invention) In the Jacob-type engine brake device described above, the leaf spring device for retreating the master piston, which is a fluid pressure supply source, to the rest position during normal operation of the engine has severe space restrictions. Although it has the advantage that it can be easily housed in the engine head and that the required spring force can be easily secured, the conventional single leaf spring breaks near the fixed end due to long-term use. If the master piston is damaged, the master piston will always contact the cooperating rocker arm and repeat unnecessary reciprocating operation.Therefore, there is a risk of damaging the rocker arm and the valve train parts such as the push rod. high.

SUMMARY OF THE INVENTION An object of the present invention is to provide an engine brake device capable of extremely effectively preventing breakage of a leaf spring device in the above-described engine brake device and preventing damage to valve train components. Is what you do.

(Means for Solving the Problems) In order to achieve the above object, an engine brake device according to the present invention provides at least one exhaust valve provided for each cylinder of an engine and a normal exhaust valve for each cylinder. A rocker arm that opens in the stroke, a slave piston that is arranged in one or more cylinders and that forcibly opens the exhaust valve of the cylinder near the compression top dead center during engine brake operation, a specific crank for the cylinder with the slave piston A master piston that is driven by the rocker arm of another cylinder in an angular relationship and supplies working fluid pressure to the slave piston, forms a closed circuit during engine brake operation, and interlocks the slave piston with the master piston during normal operation of the engine. Open to the atmosphere, the slave piston and the master piston A fluid circuit device for canceling the interlocking relationship, and a leaf spring device for retreating the master piston to a stationary position where the master piston does not abut a cooperating rocker arm when the fluid circuit device is open to the atmosphere. , Wherein the leaf spring device comprises a plurality of leaf spring members.

(Operation) According to the present invention, the leaf spring device for retreating the master piston to the rest position during normal operation of the engine includes a plurality of, for example, two leaf spring members. Since there is almost no possibility that the two leaf spring members are broken at the same time, unnecessary contact between the master piston and the rocker arm can be reliably avoided.

(Examples) Examples of the present invention will be specifically described below with reference to the accompanying drawings.

In the figure, reference numeral 10 denotes a cylinder head of a diesel engine for vehicles such as trucks, and the cylinder head 10 includes:
Each of the plurality of cylinders is provided with at least one appropriate number of exhaust valves 12a and 12b in the illustrated case. The exhaust valves 12a and 12b are controlled to be opened and closed by a rocker arm 18 via a crosshead 16 mounted so as to freely slide up and down along a guide pin 14 implanted on the cylinder head 10.

In spite of the production errors and assembly errors of the exhaust valves 12a and 12b, inevitably occurring in the production technology, the crosshead 16, etc.,
To allow the exhaust valves 12a and 12b to be opened and closed substantially simultaneously, an adjusting screw 22 is slidably fitted to a valve stem 20 of one of the exhaust valves 12a, and the adjusting screw 22 is attached to the crosshead 16 above. , And fixed at an appropriate position adjusted by the lock nut 24.

A housing 26 is provided above the cylinder head 10,
A slave cylinder 30 slidably housing a slave piston 28 and a master cylinder 34 slidably housing a master piston 32 are provided in the housing 26, and the master cylinder 34 and the slave cylinder 30 are mutually connected by a passage 36. Are in communication. An operating rod 38 extending downward from the slave piston 28 is connected to the valve stem 20 of the one exhaust valve 12a.
The slave piston 28 is always urged upward by a return spring 40. Further, an adjusting screw 42 is provided on the upper part of the slave piston 28.
Are screwed together, and the slave piston 28 is
The rest position, i.e., the position at which the fluid pressure (usually hydraulic pressure) is not supplied to the slave cylinder 30 and the slave piston 28 is pushed up by the return spring 40 and abuts against the lower end of the adjusting screw 42 to stop, is limited. , A required gap C ₁ (see FIG. 3) is set between the lower end surface of the operating rod 38 and the top surface of the valve stem 20 of the exhaust valve 12a.

The lower extension 44 of the master piston 32 is located above an adjusting screw 46 of a rocker arm 18 'which controls the opening and closing of a similar exhaust valve of a cylinder separate from the cylinder having the illustrated exhaust valves 12a and 12b. ing. Rocker arm above
The separate cylinder with 18 'is such that the rocker arm 18' is pushed up by the push rod 19 during the exhaust stroke when the piston in the cylinder with the exhaust valves 12a and 12b has just reached compression top dead center. It is preferable that the cylinder is a cylinder related to the crank angle. In this sense, the rocker arm is shown in FIG.
8 'is used.

When no fluid pressure is supplied into the master cylinder 34, two leaf spring members 48a each having one end fixed to the lower surface of the housing 26 to push up the master piston 32 upward and retreat to the rest position. Leaf spring device consisting of and 48b
A free end of each of the leaf spring members 48a and 48b is in contact with a vicinity of a lower end of the master piston 32.

A control valve 52 constantly urged downward by a spring 50 is slidably stored in the housing 26.
52 has an internal passage 56 which is opened and closed by a spring-loaded ball check valve 54. The control valve 52 allows the passage 58 communicating with the slave cylinder 30 to communicate with the outlet passage 62 of the electromagnetic three-way valve 60 in the raised position shown in FIG. The passage 58 communicates with a return passage 64, and the return passage 64 communicates with a working fluid tank 66 that is open to the atmosphere, such as an oil pan of an engine.

The solenoid three-way valve 60 includes a solenoid 68 and a valve spool 70.
The valve spool 70 has a vertical displacement that causes the outlet passage 62 to communicate with the inlet passage 74 communicating with the discharge side of the fluid pump 72 or a return passage communicating with the working fluid tank 66.
Selectively communicate with any of 76. Above solenoid 68
The manual switch 78 that is closed when the driver wants the braking effect of the power tard device, the clutch switch 80 that is closed when the clutch of the vehicle is engaged, and the driver's depression amount of the accelerator pedal In-vehicle power supply via accelerator switch 82, which is closed when it is virtually zeroed
Connected to 84. Of course, the accelerator switch 82 can be equally replaced by a fuel supply control member of the fuel pump, for example, a fuel pump switch that is closed when the control rack of the row fuel injection pump is in the idle position.

In the above configuration, at the time of normal operation of the engine, even if the driver closes the manual switch 78 for the braking effect of the power tard device, at least one of the clutch switch 80 and the accelerator switch 82 is open. , Solenoid 68 is deenergized. When the solenoid 68 is deenergized, the valve spool 70 is at the illustrated position, and the inlet passage 74 and the outlet passage
The fluid pump 72 is shut off by the land.
Is discharged from the relief valve (not shown) to the working fluid tank 66. On the other hand, the control valve 52
Since the slave cylinder 30, the passage 36, and the master cylinder 34 are pushed down to the rest position below the illustrated position by 50, the slave cylinder 30, the passage 36, and the master cylinder 34 Open to the public.

Since the slave cylinder 30 and the master cylinder 34 are in communication with the atmosphere, the slave piston 28 is pushed up to the illustrated rest position by the return spring 40, and the master piston 32 is also pushed to the illustrated rest position by the leaf spring device 48. Has been raised. Thus, between the lower end surface of the slave piston 28 integral with the actuating rod 38 and the valve stem upper end surface of the exhaust valves 12a, pre Chojo been clearance C ₁ is formed, whereas the lower extension 44 of the master piston 32 clearance C ₂ is also set in advance between the lower end surface and the upper end surface of the adjustment screw 46 of the rocker arm 18 'of are formed. Therefore, the engine has the master piston 32
Normal operation can be performed independently of the slave piston 28.

Next, when the vehicle enters the engine brake running state, the clutch switch 80 and the accelerator switch 82 are both closed, and when the manual switch 78 is closed, the solenoid 68 is energized. Since the valve spool 70 compresses the return spring and descends by the bias of the solenoid 68,
The inlet passage 74 and the outlet passage 62 of the electromagnetic three-way valve 60 communicate with each other, and the working fluid pressure acts on the lower surface of the control valve 52 so that the control valve compresses the spring 50 and rises. Since the ball check valve 54 is opened by the working fluid pressure, the working fluid is
Is supplied to the slave cylinder 30 via the passage 58, and further supplied from the passage 36 into the master cylinder 34.

When the fluid pressure is supplied into the master cylinder 34, the master piston 32 is pushed down against the leaf spring device 48 and abuts the adjusting screw 46 of the rocker arm 18 ', while the slave piston
28 also compresses the return spring 40 and descends, and the operating rod 38
Is in contact with the top surface of the valve stem of the exhaust valve 12a. However, at this time, the pressing force acting on the valve stem 20 of the operating rod 38 is smaller than the closing force of the valve spring of the exhaust valve 12a, so that the exhaust valve 12a
Is not forcibly opened by the slave piston 28 except during the normal exhaust stroke, and the rocker arm 18 swings through the cross head 16 through the exhaust valve 12b during the exhaust stroke.
Will be released with When the cylinder provided with the exhaust valves 12a and 12b reaches the vicinity of the compression top dead center, the rocker arm 18 'of the other cylinder, which has just reached the exhaust stroke, pushes the push rod 19'.
And the master piston 32 is pushed up via the adjusting screw 46 of the rocker arm 18 '. Since the ball check valve 54 closes when the master piston 32 rises, the fluid circuit composed of the master cylinder 34, the slave cylinder 30, and the passages 36 and 58 forms a closed circuit. Descend. The operating rod 38 moves down together with the slave piston 28 to forcibly push down the valve stem 20 to open the exhaust valve 12a. Accordingly, the compressed supply air in the cylinder is discharged into the exhaust pipe through the exhaust valve 12a and does not perform a positive work in the subsequent expansion stroke, so that the engine temporarily operates as an air compressor, and the Consumption consumes an effective engine braking effect.

During the operation of the engine brake, the master piston 32 reciprocates repeatedly by the rocker arm 18 ', so that the leaf spring members 48a and 48b of the leaf spring device 48 swing about the fixed end. Since the two leaf spring members 48a and 48b are used, the surging stress is reduced and each leaf spring member is effectively prevented from being damaged, and even if any one of the leaf spring members 48a and 48b is operated for a long period of time. However, it is unlikely that the two leaf spring members will be broken at the same time even if they are broken due to fatigue. Accordingly, the master piston 32 falls due to the breakage of the leaf spring device 48, and is constantly brought into contact with the adjusting screw 46 of the rocker arm 18 'even during normal operation of the engine, so that the master piston 32 is reciprocally driven unnecessarily. There is an advantage that the damage caused by the increase is reliably avoided.

In the above embodiment, the leaf spring device 48 has two leaf spring members 48.
a and 48b, but three or more leaf spring members can be used. Further, in the above embodiment, two exhaust valves 12a and 12b are provided in one cylinder. However, the present invention can be applied to an engine having one exhaust valve in one cylinder.
The crosshead 16 is forcibly driven by 28 and has two exhaust valves.
12a and 12b can be changed to open simultaneously near the compression top dead center. Further, the fluid exhaust valve opening device including the master piston 32 and the slave piston 28 does not necessarily need to be provided in all cylinders of the engine, and even if provided in some cylinders, a certain engine braking effect can be produced. It is self-evident.

(Effect of the Invention) As described above, the engine brake device according to the present invention provides at least one exhaust valve provided in each cylinder of an engine, and a rocker arm that opens the exhaust valve of each cylinder in a normal exhaust stroke. A slave piston disposed in one or more cylinders and forcibly opening an exhaust valve of the same cylinder near a compression top dead center at the time of engine braking operation;
A main piston which is driven by a rocker arm of another cylinder having a specific crank angle relationship with respect to a cylinder having a slave piston and supplies working fluid pressure to the slave piston, forms a closed circuit during engine braking to form the slave piston. A fluid circuit device linked to the main piston and released to the atmosphere during normal operation of the engine to eliminate the interlocking relationship between the slave piston and the main piston, and the main piston when the fluid circuit device is opened to the atmosphere. A leaf spring device for retreating to a rest position not in contact with a cooperating rocker arm, wherein the leaf spring device is constituted by a plurality of leaf spring members. This effectively prevents damage to the various components of the valve train, resulting in durability. Since the engine braking device finely reliability is excellent can be provided at low cost, it is advantageous industrially.

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing one embodiment of the present invention, FIG. 2 is an enlarged sectional side view of a portion II surrounded by a chain line in FIG. 1, and FIG. 3 is a portion III surrounded by a chain line in FIG. FIG. 10 ... Cylinder head, 12a and 12b ... Exhaust valve, 16 ...
Crosshead, 18 and 18 ': Rocker arm, 19: Push rod, 26: Housing, 28: Slave piston, 30: Slave cylinder, 32: Master piston, 34: Master cylinder, 48: Plate Spring device, 52 ……
Control valve, 60 ... three-way solenoid valve.

Claims (1)

(57) [Claims] At least one exhaust valve provided in each cylinder of the engine, a rocker arm for opening the exhaust valve of each silling in a normal exhaust stroke, and one or more cylinders are provided at the same time during engine braking operation. The slave piston forcibly opens the exhaust valve of the cylinder near the compression top dead center, is driven by the rocker arm of another cylinder having a specific crank angle relationship with the cylinder having the slave piston, and the working fluid pressure is applied to the slave piston. The master piston to be supplied, a fluid circuit that forms a closed circuit during engine brake operation and interlocks the slave piston with the master piston and is released to the atmosphere during normal operation of the engine to eliminate the interlocking relationship between the slave piston and master piston. Device and the fluid circuit device is open to the atmosphere An engine having a leaf spring device for retreating the master piston to a rest position where the master piston does not abut a cooperating rocker arm, wherein the leaf spring device comprises a plurality of leaf spring members. Brake device.