JPH01242856A - Brake device for automatic transmission - Google Patents

Abstract

PURPOSE:To reduce the speed change shock by forming the first oil chamber for pressing a piston and the second oil chamber which communicates to the first oil chamber through a valve mechanism and making each pressure receiving area of the piston in the feed of the hydraulic pressure into the first oil chamber and the feed of the hydraulic pressure into the both oil chambers nearly equal. CONSTITUTION:In the state where the second hydraulic chamber 4 is pressure discharged, if a line hydraulic pressure is supplied into the first hydraulic chamber 43 by selecting a selector valve 49, a brake band 22 is tightened by the advance of a piston 33, and if a drum 20 revolves in the deenergizing direction, a hydraulic servocylinder 32 retreats together with an anchor rod 25, and a valve mechanism 41 is opened to discharge oil pressure, and a brake device is not operated. While, brake is applied in the revolution in the energizing direction. When a hydraulic pressure is supplied also into the second hydraulic chamber 44, the retreat of the hydraulic servocylinder 32 is suppressed, and the valve mechanism 41 is not opened, and the unidirectional characteristic is eliminated, and the engine brake can act effectively. Since, in this case, the pressure receiving area of the piston 33 does not increase, no speed change shock is generated, and the timing in supplying a hydraulic pressure into the second oil chamber 44 is not restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a brake that prevents rotation of a planetary gear element such as a sun gear in a 51!2 star gear mechanism in order to set a predetermined gear in an automatic transmission for a vehicle. The present invention relates to a device, and in particular to a band brake device.

As is well known in the art, automatic transmissions for automobiles use two or three sets of planetary gear mechanisms or differential VJ gear mechanisms, and the three elements (i.e., planetary gear mechanism) that make up these gear engagements. By fixing either element (the sun gear, the carrier, the ring gear, or the ring gear and a pair of side gears meshing with it in the case of a first gear mechanism), and using the other two main gears as the input member and the output member, It is configured to obtain a gear ratio of .

By the way, in the battle for automatic transmission, it is important to achieve smooth gear shifts without so-called shift shocks, and for this purpose, one-way clutches have traditionally been incorporated into gear transmissions, and timing valves and accumulators have often been used in hydraulic control circuits. This is aimed at optimizing the timing of clutch and brake engagement. However, frequent use of one-way clutches, timing valves, etc. increases the number of components of the automatic transmission, leading to increased weight and higher prices.

Therefore, the present applicant has already proposed a brake device that can effectively eliminate the shift stain without complicating the overall mechanism (Japanese Patent Application No. 62-306951). A schematic diagram of this brake device is shown in FIG. 5. When hydraulic pressure is sent to the inside of the servo cylinder 100, that is, the first oil chamber 101, the piston 102 moves forward, causing the push rod 103 to move along with the armature rod 104 to the brake band 105. Tighten to perform braking. In that case,
Assuming that the brake drum 106 is rotating in the deenergization direction indicated by the symbol B in FIG. 5, the servo cylinder 10
The valve body 107 moves integrally with the anchor rod 104 to the left in FIG. Since it is opened, pressure is exhausted from the first oil chamber 101, and as a result,
Since there is no force to press the push rod 103, no braking is performed. On the other hand, if the brake drum 106 is rotating in the energy direction shown by the symbol @ in FIG.
Since the brake drum 106 wraps around the brake band 105 and the valve body 107 cannot be opened, braking can be performed. In addition, the first oil chamber 101 and the second oil chamber
By supplying hydraulic pressure to both oil chambers 108, the piston 1 is prevented from moving backwards of the servo cylinder 100.
02 will be pressurized, so the brake drum 106
Prevents rotation in any direction.

Therefore, in the above-mentioned brake device proposed by the present applicant, a one-way characteristic occurs depending on the way the hydraulic pressure is supplied, and the brake can be released by rotation of the brake drum, so a complicated mechanism such as a timing valve is used. Shift shock can be reduced without any problems.

Problems to be Solved by the Invention However, in the above-mentioned brake device already proposed by the present applicant, if hydraulic pressure is supplied to the first oil chamber 101 and pressure is discharged from the second oil chamber 108, braking can be performed in the de-energization direction. However, for example, line hydraulic pressure is supplied to the first oil chamber 101 and the second oil chamber 108 is communicated with a drain to brake the brake drum 1.
06 is prevented from rotating in the energy direction and a predetermined gear stage is set, if engine braking continues in that state, a torque in the energy direction is applied to the brake drum 106, so the servo cylinder 100 moves backward as described above. The valve body 107 operates as a valve, and as a result,
Not only does the brake drum 106 rotate and braking is not effective, but the line oil pressure is too low in the first oil chamber 101 and the second oil chamber 108.
Pressure is exhausted through the Therefore, in the case of a gear stage that prevents rotation of the brake drum 706 in the energy direction when hydraulic pressure exhibiting a unidirectional characteristic is supplied, hydraulic pressure is supplied to the second oil chamber 108 after the shift is completed to maintain the unidirectional characteristic. It is necessary to resolve it.

It is desirable to supply hydraulic pressure to the second oil chamber 108 in order to eliminate the one-way characteristic after the completion of the shift in which the rotation of the brake drum 106 is almost completely blocked. The completion of the shift is determined by detecting the rotational speed of a rotating member such as a gear, or by detecting the oil pressure in a predetermined oil passage, and based on the result, operates a solenoid valve or the like to reach the second oil chamber 108. Although it is possible to configure the oil passage to be open, such a configuration increases the number of components such as detectors and solenoid valves, so it is difficult to simplify the configuration by adding one-way characteristics to the brake device. This would go against the current trend and overturn it.

On the other hand, the switching valve is configured to open the oil passage that supplies line oil pressure to the second oil chamber 108 as the oil pressure in the first oil chamber 101 increases, and supplies oil pressure to the first oil chamber 101. By doing so, when braking is almost completed, the second oil chamber 108
It may be possible to eliminate the one-way characteristic by supplying hydraulic pressure to the However, in that case, if a cylindrical part 109 that serves as a guide is formed on the living surface of the piston 102 so as to protrude into the second oil chamber 108, it is possible to supply hydraulic pressure to the first oil chamber 101 and to the second oil chamber 108. Since the force that presses the push rod 103 is greatly different when hydraulic pressure is supplied,
It is necessary to prevent the occurrence of shift shock associated with this.

That is, the piston pressing force when hydraulic pressure Pb is supplied to the first oil chamber 101 is (π/4) x (Dp 2 - Dr 2 ) x Pb
-FDp: Diameter of the piston D ": Diameter of the cylindrical portion F: The elastic force of the return spring 110. On the other hand, the piston pressing force when hydraulic pressure Pb is supplied to the second oil chamber 108 is (π/4) xDp 2 xPb -F, which is very different. Therefore, ah to the second oil chamber 108
If the pressure is supplied, for example, during the inertia phase of a shift transient state, the shift shock will increase due to a sudden increase in brake torque. This situation is shown in FIG. 6. During the inertia phase in which the accumulator is acting and the oil pressure Ps1 in the first oil chamber 101 rises slowly and the brake is slipping, the oil pressure in the second oil chamber 108 is increased. is supplied and the pressure ps2 increases, the brake torque rapidly increases due to the large pressure receiving area. As a result, the output shaft torque suddenly increases as shown by the chain line in FIG. 6, resulting in a shift shock.

Furthermore, when the oil pressure in the first oil chamber 101 rises to the specified line pressure, sufficient braking force can be generated, but if line pressure is also applied to the second oil chamber 108, the brake band 105 Since the fastening force of the brake band 105 further increases, excessive tension acts on the brake band 105, resulting in a problem that the durability of the brake band 105 is reduced.

This invention was made against the background of the above-mentioned circumstances, and is capable of providing one-way characteristics, easily reducing shift shock, and furthermore preventing deterioration in the durability of the brake band. The object of the present invention is to provide a brake device for automatic gear shifting.

Means for Solving the Problems In order to achieve the above object, the present invention improves the above-mentioned brake device proposed by the present applicant, and provides a case in which hydraulic pressure is supplied to the first oil chamber and a case in which hydraulic pressure is supplied to the first oil chamber. The present invention is characterized in that the pressing force applied to the piston is approximately equal when hydraulic pressure is supplied to both the first oil chamber and the second oil chamber.

More specifically, the present invention places a brake band on the outer peripheral side of a rotating body placed in a case, and tightens the brake band by bringing both ends of the brake band close to each other using an anchor rod and a push rod. In a brake device for braking a rotating body, a hydraulic cylinder that moves back and forth in a tangential direction of the rotating body is arranged in a position facing the anchor rod in the case, and the push rod is attached to the piston of the hydraulic cylinder. The hydraulic cylinder and the anchor rod are connected to move together, and a first oil chamber is formed on the side of the hydraulic cylinder opposite to the push rod across the piston, and the fluid forming a second oil chamber on a side opposite to the push rod with respect to the pressure cylinder;
Furthermore, a valve n@ is provided that opens to communicate each oil chamber when the fluid pressure cylinder retreats to the second oil chamber side, and
The area where the piston receives hydraulic pressure when hydraulic pressure is supplied only to the oil chamber is approximately equal to the area where the piston receives hydraulic pressure when hydraulic pressure is supplied to both the first oil chamber and the second oil chamber. It is characterized by the presence of

Operation In the brake device of the present invention, when line hydraulic pressure is supplied to the first oil chamber with the second oil chamber communicating with the exhaust pressure oil passage,
The brake band is tightened by the advance of the piston, but in that case, if the brake drum is rotating in the deenergization direction, the hydraulic servo cylinder is moved backward together with the anchor rod, so the valve mechanism opens and the first oil Pressure is evacuated from the chamber, and as a result, no braking force is generated for the brake band, so no braking is performed. On the contrary, if the brake drum is rotating in the energy direction, the brake drum will wrap around the brake band, so braking will be performed and the pressure will not be exhausted from the first oil chamber. In other words, if hydraulic pressure is supplied only to the first oil chamber, it exhibits one-way characteristics, but if hydraulic pressure is also supplied to the second oil chamber, the retreat of the hydraulic servo cylinder is prevented and the valve mechanism does not open. Therefore, the one-way characteristic is eliminated, and therefore, for example, engine braking can be applied. When oil pressure is supplied to the second oil chamber while oil pressure is being supplied to the first oil chamber, the pressure receiving area of the piston does not increase due to the supply of oil pressure to the second oil chamber, so the brake torque does not particularly increase. Therefore, the shift shock is not worsened by the supply of hydraulic pressure to the second oil chamber, so there are no particular restrictions on the timing of supply of hydraulic pressure to the second oil chamber, and as a result, the hydraulic control device and brakes can be easily controlled. Become something.

Example Next, embodiments of the invention will be described with reference to the drawings.

Figure 1 shows that braking is performed in reverse rotation (rotation in the opposite direction to the rotational direction of the engine, the same applies hereinafter) in the second forward speed, and in the fourth
1 is a sectional view showing an example in which the present invention is applied to a brake that performs braking in a forward rotation (rotation in the same direction as the engine rotation direction, the same applies hereinafter) at a high speed, and shows a brake drum 2 which is a rotating body.
0 also serves as a clutch drum, and this brake drum 20 is housed inside a transmission case 21, and a brake band 22 is arranged on the outer circumferential side of the brake drum 20. Both ends of this brake band 22 are arranged to be close to each other and face each other, and one end, that is, the first anchor portion 2
3, a spherical or arcuate support is supported by pressing the tip of an anchor rod 25 against a cap 24 having a surface. The anchor rod 25 is housed in a hollow portion formed in the transmission case 21 in the tangential direction of the brake drum 20 so as to move backward lFf in the axial direction, that is, in the tangential direction of the brake drum 20, and its rearward end (as shown in FIG. The rightward movement (vJ end) is defined by an adjustment bolt 26, and the outer circumferential side is sealed by an O-ring 27. A radially protruding flange portion 28 is formed at the tip of the anchor rod 25, and a connecting rod 29 passes through and is fixed to the flange portion 28, and the tip of the connecting rod 29 is attached to the transmission case. 21 is slidably fitted into a hole 30 formed in parallel with the anchor rod 25, so that the tips of the two connecting rods serve as guide pins.

The other end of the brake band 22 , that is, the second anchor part 31 has a push rod 34 attached to a piston 33 of a hydraulic servo cylinder 32 provided in the transmission case 21 at a position substantially facing the anchor rod 25 . It is held by pressing.

The hydraulic servo cylinder 32 is movably housed inside a hollow portion 35 formed in the transmission case 21 41! An annular stopper 36 that is in close contact with the inner peripheral surface is disposed at the rear end (the end in the opposite direction from the push rod 34 with the piston 33 in between). On the side, a valve sleeve 37 that protrudes on both front and rear sides in the axial direction is arranged so as to be movable back and forth.
Further, a cylindrical portion 33a on the rear end side of the piston 33 is in sliding contact with the inner circumferential surface of the valve sleeve 37 while maintaining liquid tightness.

As shown enlarged in FIG. 2, a slight gap is formed between the outer circumferential surface of the valve sleeve 37 and the inner circumferential surface of the stopper 36, forming an oil passage 38. Of these, the front from the stopper 36 (see Figs. 1 and 2)
The portion protruding rightward in the figure extends outward in the radial direction, and among the extending portions 39, the stopper 3
The surface facing the front of 6 closes the oil passage 38 between the stopper 36 and the inner circumferential surface of the stopper 36 . Therefore, here is the valve sleeve 3.
A valve structure 41 is constructed in which 7 is a valve body and the front side of the stopper 36 is a valve seat 40.

Hollow part 3 containing the above-mentioned hydraulic servo cylinder 32
The rear end (left end in FIG. 1) of 5 is sealed by a case cover 42, and therefore, inside the hollow part 35, there is a first oil chamber 4 between the piston 33 and the stopper 36.
3 and a second oil chamber 44 between the stopper 36 and the case cover 42 are formed. The cylindrical portion 33a penetrates through the case cover 42 while maintaining liquid tightness, and as a result, the case cover 42 also serves as a guide for guiding the piston 33 in the front-rear direction.

Therefore, in the above configuration, the cylindrical portion 33a is the first oil ¥4
3 and the second oil chamber 44, the first
The pressure receiving area of the piston 33 under which pressure is applied by the hydraulic pressure supplied to the oil chamber 43 is approximately equal to the pressure receiving area of the piston 33 when hydraulic pressure is supplied to both the first oil chamber 43 and the second oil chamber 44, and that value is ff/4) X (Dp2-Dr2)
Dp: Piston diameter Dr expressed as the diameter of the inner cylindrical portion.

The length of the valve sleeve 37 protruding toward the second oil chamber 44 is set to such a length that the valve sleeve 37 comes into contact with the case cover 42 within the movable range of the hydraulic servo cylinder 32. Therefore, the valve mechanism 41 is a hydraulic servo cylinder. The valve is configured to be opened by the backward movement of 32.

The hydraulic servo cylinder 32 also includes the connecting rod 29.
Since one end of the connecting rod 29 is attached and the other end of the connecting rod 29 is fixed to the anchor rod 25 as described above, the hydraulic servo cylinder 32 and the anchor rod 25 are connected to each other.
The brake drum 20 moves back and forth in the tangential direction of the brake drum 20 as a unit.

Further, in the hydraulic servo cylinder 32, in front of the piston 33, a return spring 45 is arranged to push the piston 33 back toward the left in FIG.

The first oil chamber 43 includes a line hydraulic oil passage 46 that supplies line hydraulic pressure when setting the second forward speed and the fourth forward speed.
is connected. As this line hydraulic oil passage 46,
For example, an oil path that is connected to a 1-2 shift valve and a 3-4 shift valve (not shown in the figures) and that branches off from an oil path that is supplied with line hydraulic pressure when setting the second forward speed and when setting the fourth forward speed. can do. An orifice 47 and an accumulator 48 are interposed in this line hydraulic oil passage 46 . On the other hand, the second oil chamber 44 is
It is connected to a portion of the line hydraulic oil passage 46 closer to the first oil chamber 43 than the accumulator 48 via a switching valve (brake servo sequence valve) 49 . This switching valve 49
By moving the spool 50 having two lands, the first boat 51 with which the second oil chamber 44 is connected can be connected to either the second boat 52 or the drain boat 53 with which the line hydraulic oil passage 46 is connected. A spring 54 that presses the spool 50 is disposed at one end of the spool 50, and this spring 54
A first control pressure boat 55 is formed at a location where the line hydraulic oil passage 46 is branched and connected thereto. Further, a control hydraulic oil line 57 is connected to the second control pressure boat 56 on the opposite side of the spring 54 for applying a shift signal hydraulic pressure generated in the second and third forward speeds to the second control pressure boat 56. has been done.

Note that an annular groove 62 is formed in the transmission case 21 corresponding to a small hole 61 formed in the hydraulic servo cylinder 32 to supply and discharge hydraulic pressure to and from the first oil chamber 43, and the line hydraulic oil is inserted into the annular groove 62. Although the small hole 61 and the annular groove 62 have a width that does not match when the hydraulic servo cylinder 32 moves backward, the first oil chamber 43 and the line hydraulic oil path 46 are cut off. It is set to do so.

Next, the operation □ of the brake device configured as described above will be explained.

The above-mentioned brake device engages in 2nd forward speed and 4th forward speed to set the respective gears, so when shifting up to these gears and downshifting from these gears, Explain the action. The presence or absence of a shift signal hydraulic pressure for the second control pressure boat 56 for each shift pattern, the boat with which the first boat 51 communicates with the switching valve 49, and the presence or absence of braking are shown in Table 1.

(This page, the following is a margin) Table 1 When shifting up from 1st speed to 2nd speed, the shift signal oil pressure is generated in the control oil pressure oil name 57, so the second
The shift signal hydraulic pressure acts on the control pressure boat 56, and as a result,
The spool 50 moves to the left side in FIG. 1 (the position shown at the bottom in FIG. 1), and the first boat 51 moves to the drain boat 53.
It will be communicated to.

That is, the pressure is exhausted from the second oil chamber 44. At the same time, line oil pressure for setting the second speed is generated in the line oil pressure oil name 46 by, for example, switching the 1-2 shift valve (not shown), so line oil pressure is applied to the first oil chamber 43. Supplied. As a result, hydraulic servo cylinder 3
2, the piston 33 moves to the right side in FIG. 1 and starts tightening the brake band 22 via the push rod 34. In that case, the brake drum 20 is rotating (reversely rotating) in the direction indicated by the symbol A, but this rotation direction is the so-called energy direction that coincides with the direction of tightening by the push rod 34, and the brake drum 20 and the brake The frictional force generated between the hydraulic servo cylinder 32 and the band 22 causes the hydraulic servo cylinder 32 to move to the right in FIG. Therefore, the tightening by the push rod 34 not only increases the force but also causes the so-called winding force of the brake drum 20 to tighten the brake band 2.
2 wraps tightly around the brake drum to perform braking. In that case, the accumulator 4 is connected to the first oil chamber 43.
Since the line oil pressure is supplied via 8, the oil pressure increases slowly depending on the characteristics of the accumulator 48. Further, the hydraulic pressure supplied to the first oil chamber 43 gradually increases,
When the pressing force caused by the hydraulic pressure applied to the first control pressure boat 55 and the spring 54 exceeds the pressing force caused by the shift signal hydraulic pressure applied to the second control pressure boat 56, the spool 50 moves to the right side in Fig. 1 (upper side in Fig. 1). As a result, the second oil chamber 44 communicates with the line hydraulic oil passage 46,
Line oil pressure is also supplied to the second oil chamber 44 . Therefore, after the shift is completed, the backward movement of the hydraulic servo cylinder 32 is blocked by the hydraulic pressure applied to the second oil chamber 44, so that, for example, the engine is in a braking state and the brake drum 20 is moved in the direction indicated by the symbol B in FIG. Even if the hydraulic servo cylinder 32 attempts to rotate forward (forward rotation), the hydraulic servo cylinder 32 does not move backward and maintains the braking state of the brake drum 20.

The oil pressure psi of each oil chamber 43, 44 during the above shifting process
, ps2, brake torque, and output shaft torque are shown in Fig. 3. That is, the first oil chamber 43
When the oil pressure ps1 starts to rise, the brake torque also rises, but after the accumulator 48 starts to act, the rise in the oil pressure in the first oil chamber 43 becomes slow, so the rise in the brake torque also becomes slow. , no large change occurs in the output shaft torque. As the oil pressure Ps1 for the first oil chamber 43 increases, that is, the oil pressure at the first control pressure boat 55 in the switching valve 49 increases, the switching valve 49 performs a switching operation during the gear shift, and the oil pressure also increases in the second oil chamber 44. However, as mentioned above, since the cylindrical portion 33a protruding from the piston 33 passes through each oil chamber 43, 44, the second
Even when oil pressure starts to be supplied to the oil chamber 44, the pressure receiving area of the piston 33 that receives the oil pressure does not particularly increase, so the brake torque does not change greatly and increases slowly. That is, since oil pressure starts to be supplied to the second oil chamber 44, the output shaft torque does not fluctuate, so that the shift shock is improved.

On the contrary, when downshifting from 2nd speed to 1st speed, the shift signal oil pressure is discharged from the control oil pressure oil passage 57, and the line oil pressure oil passage 46 receives, for example, 1-2 shift pulp switching. The action exhausts the line hydraulic pressure. Since the spool 50 of the switching valve 49 was pressed to the right side in FIG. 1 in the second speed state, the second control pressure boat 5
The gear shift signal oil pressure that had been acting on the gear shift signal hydraulic pressure no longer acts on the gear shift signal oil pressure 6 and does not operate in particular, so the second oil chamber 44 communicates with the line hydraulic oil passage 46 via the first boat 51 and the second boat 52. It will remain as it is. Therefore, the hydraulic pressure in each oil chamber 43, 44 in the hydraulic servo cylinder 32 is discharged through the line hydraulic oil passage 46, and accordingly, the pressing force of the push rod 34, that is, the tightening force of the brake band 22 is lost, so that the brake The braking of the drum 20 is released, the brake drum 20 begins to rotate in reverse, and the first speed is set. In that case, since the accumulator 48 acts, the oil pressure in each oil chamber 43, 44 slowly decreases according to the characteristics of the accumulator 48, and as a result, the brake drum 20 is slowly released from the brake drum 20, so that the shift from the second gear to the first gear is performed. Shift shock associated with downshifting is reduced.

In the second speed state, as described above, the second control pressure boat 56
Although the shift signal oil pressure is acting on the line oil pressure for setting the second speed, the spool 50 has moved to the right side in FIG. 1 because the line oil pressure for setting the second speed is acting on the first control pressure boat 55. Reverse rotation of the brake drum 20 is prevented. When shifting to the third forward speed in this state, for example 2-3, the shift signal oil pressure is applied to the second control pressure boat 56.
As the shift pulp (not shown) operates, pressure is discharged from the line hydraulic oil passage 46, so the oil pressure in each oil chamber 43, 44 slowly decreases according to the characteristics of the accumulator 48. When the pressure in the first control pressure boat 55 of the switching valve 49 decreases due to a decrease in the oil pressure in the line hydraulic oil passage 46, the spool 50 is moved to the left side in FIG. As a result, the pressure is rapidly exhausted from the second oil chamber 44 via the first boat 51 and the drain boat 53. In this state, the first
The brake band 22 contacts the brake drum 20 by pressing the push rod 34 only with the oil pressure in the oil chamber 43, and when the clutch torque for setting the third gear reaches the turbine torque, the brake drum 20
begins to rotate forward (rotation in the deenergization direction) in the direction indicated by symbol B in FIG.
2, the pressure is discharged from the second oil chamber 44, so that the first
It is moved backwards to the left in the figure. When the hydraulic servo cylinder 32 retreats to a certain extent, the pulp sleeve 37 comes into contact with the case cover 42 and its extended portion 39 separates from the valve seat 40 of the stopper 36 as shown in FIG. 62 and the first oil chamber 43 is cut off from the line hydraulic oil passage 46.
The hydraulic pressure is rapidly discharged through the oil passage 38 and the second oil chamber 44, and as a result, the pressing force of the push rod 34 is eliminated, so that the braking of the brake drum 20 is released. In other words, when shifting up from 2nd gear to 3rd gear, the brake drum 20 starts rotating and releases the brake.In other words, it acts as a one-way clutch, so the engagement of the clutch and the brake The timing perfectly matches the release of the gearbox, and the shift shock is greatly improved.

When shifting from 3rd forward speed to 2nd speed,
The shift signal hydraulic pressure remains supplied to the second control pressure boat 56. Further, line hydraulic pressure is supplied to the line hydraulic oil passage 46 by operating a 2-3 shift valve, for example. Line hydraulic fluid line 46 for downshifting to 2nd gear
Line hydraulic pressure begins to be supplied to the line, and the first oil ￥4
3 begins to rise according to the characteristics of the accumulator 48, the brake drum 20 continues to rotate in the forward direction until the clutch is sufficiently released, but in this state, the brake is stopped due to the increase in the oil pressure in the first oil chamber 43. When a frictional force is generated between the band 22 and the brake drum 20, the hydraulic servo cylinder 32 is moved backward by the rotational force of the brake drum 20, and as a result, the valve sleeve 37 comes into contact with the case cover 42 and the oil passage 38 open. Therefore, at this point, even if oil pressure is supplied to the first oil chamber 43,
Based on this, the brake band 22 is connected to the brake drum 2.
0, the pressure is discharged from the first oil chamber 43 as described above, and as a result, the brake band 22 repeatedly contacts and separates from the brake drum 20, but does not brake the brake drum 20. When the clutch is gradually released and its clutch torque decreases, the brake drum 20 begins to rotate in the opposite direction (rotation in the energy direction) as described above, and at this time, the brake band 22 is in contact with the brake drum 20, so that the hydraulic pressure is increased. Move the servo cylinder 32 to the right in FIG. Therefore, since the oil passage 38 from the first oil chamber 43 to the second oil chamber 44 is closed, the oil pressure in the first oil chamber 43 rapidly increases, tightening the brake band 22 and braking the brake drum 20. As the oil pressure in the first oil chamber 43 increases, the switching valve 49
When the oil pressure of the first control pressure boat 55 becomes high to a certain extent, the spool 50 is moved to the right side in FIG. supply. That is, since the backward movement of the hydraulic servo cylinder 32 is prevented, the forward rotation of the brake drum 32 is also prevented, and as a result, the engine brake can be applied in the second speed.

That is, in the case of upshifting from 2nd speed to 3rd speed, braking is automatically released as the brake drum 20 starts to rotate forward, and in the case of downshifting from 3rd speed to 2nd speed, braking is automatically released. Since the brake drum 20 is automatically braked when the brake drum 20 tries to rotate in the opposite direction, it functions as a one-way clutch (one-way brake), so shifting shock can be reliably and easily reduced. can. After downshifting to the second speed, hydraulic pressure is supplied to the second oil chamber 44 to cancel the one-way characteristic.

Next, the case of upshifting to 4th speed will be explained. In this case, the shift signal hydraulic pressure stops acting on the second control pressure boat 56 when the shift is determined, and the line hydraulic oil path 46 has an electromagnetic Line hydraulic pressure is supplied by operating a valve (not shown). Therefore, the switching valve 49
Since the spool 50 is located on the right side as shown in the upper side of FIG. 1, hydraulic pressure is slowly supplied to each oil chamber 43, 44 according to the characteristics of the accumulator 48. In this case, the rotation of the brake drum 20 is in the de-energy direction, but the second oil chamber 44 is also supplied with hydraulic pressure and the backward movement of the hydraulic servo cylinder 32 is prevented, so the brake band 22 is slowly tightened. As a result, forward rotation of the brake drum 20 is gradually prevented.

Also, when downshifting from 4th gear to 3rd gear, the 2nd
The shift signal oil pressure acts on the control pressure boat 56, but since the line oil pressure acts on the first control pressure boat 55 of the switching valve 49, the spool 50 is pushed to the right position in FIG. It remains as it was. Therefore 6 oil y43.
44 is slowly discharged via a line hydraulic oil passage 46.

Further, when the hydraulic pressure of the first control pressure boat 55 in the switching valve 49 decreases to a certain extent due to a decrease in the hydraulic pressure in the line hydraulic oil passage 46, the spool 50 moves to the second control pressure boat 55.
The first port 51 is moved to the left in FIG. 1 by the shift signal oil pressure acting on the drain boat 53.
Since the second oil chamber 44 is in communication with the second oil chamber 44, the pressure is rapidly evacuated from the second oil chamber 44.

In this state, a load is applied to the hydraulic servo cylinder 32 from the brake drum 20 in a direction that causes it to move backward, so the hydraulic servo cylinder 32 moves backward as pressure is discharged from the second oil chamber 44, and as described above. As in the case of upshifting to third gear, the valve sleeve 37 is pushed relatively and the first oil chamber 43 communicates with the second oil chamber 44, and as a result, the first oil chamber 43 is also rapidly drained. The pressure is applied to release the brake on the brake drum 20, and the brake drum 20 begins to rotate forward. In other words, the third speed is set.

Therefore, the above brake device can function as both a brake with unidirectional characteristics and a brake without unidirectional characteristics depending on the hydraulic pressure supply state, and as a result, the ff1lJ In addition, it can be used to effectively prevent shift shock by optimizing the timing of braking and braking release. Furthermore, when line oil pressure is supplied to the second oil chamber 44 in order to eliminate the one-way characteristic, the pressure-receiving area of the piston 33 does not particularly increase compared to the case where oil pressure is supplied to the first oil chamber 43. The tightening force of the band 22 does not suddenly increase, so even if hydraulic pressure is supplied to the second oil chamber 44 during the shift (inner sill phase), shift shock will not worsen. That is, in the above configuration, there is no particular restriction on the timing of supplying hydraulic pressure to the second oil chamber 44, and the timing control of the hydraulic illumination device and the supply of hydraulic pressure becomes simple. Furthermore, even if hydraulic pressure is supplied to the second oil chamber 44, the tension applied to the brake band 22 does not become particularly large, so that its durability can be maintained satisfactorily. Furthermore, in the configuration shown in FIG. 1, since the cylindrical portion 33a protruding from the piston 33 is long,
The sliding pitch of the valve sleeve 37 is widened, so that the movement of the valve sleeve 37 becomes smooth.

Note that the shift shock is a sensory thing, and even if the output shaft torque fluctuates to a certain extent, it may not be felt as a shift shock.Therefore, the output shaft torque does not always flow linearly, as shown in Figure 3. It's not something that has to change.

In other words, if the sudden increase in braking force is small, the sudden increase in brake torque and output shaft torque will be small, so it may not be felt as a shift shock, and the sudden increase in braking force within that range will be small. Increase is acceptable. FIG. 4 is a sectional view showing another embodiment of the present invention constructed based on this idea. In the embodiment shown here, the diameter of the cylindrical portion 33a protruding from the piston 33 is reduced. 1st
When hydraulic pressure is applied to the oil chamber 43 and when hydraulic pressure is applied to both the first oil chamber 43 and the second oil chamber 44, the piston 3
The structure is such that the pressure receiving area in No. 3 does not change significantly. That is, in the brake device shown in Fig. 4,
The diameter d of the cylindrical portion 33a with respect to the diameter Op of the piston 33
is set to be significantly smaller, and the length of the cylindrical portion 33a is set to extend only through the first oil chamber 43.

Therefore, in the configuration shown in FIG. 4, when hydraulic pressure is supplied only to the first oil chamber 43, the pressure receiving area of the piston 33 becomes π(Do 2 - dr 2)/4, whereas the first oil chamber Chamber 43 and second oil chamber 44
The pressure-receiving area of the piston 33 when hydraulic pressure is supplied to both is π·[)p 2/4. However, since the diameter dr of the cylindrical portion 33a is set to a small value as described above, there is no significant difference in the actual pressure receiving area in each of the above cases, and the difference in the pressure receiving area is due to the output shaft torque. However, considering that the timing at which hydraulic pressure starts to be supplied to the second oil chamber 44 is immediately before the completion of the shift, a temporary increase in the output shaft torque is felt as a shift shock. It doesn't get as big as it should.

Therefore, even with the configuration shown in FIG. 4, the second oil chamber 44
Since the supply of hydraulic pressure to the hydraulic pressure does not cause a shift shock, there is no particular restriction on the supply timing, and the control device and control method are simplified. It is also possible to prevent the durability of the brake band 22 from decreasing.

Effects of the Invention As is clear from the above description, the brake device of the present invention includes a first oil chamber that presses a piston to which a push rod is attached, and a second oil chamber that communicates with this first oil chamber via a valve basin.
The pressure-receiving area of the piston when hydraulic pressure is supplied to the first oil chamber is approximately equal to the pressure-receiving area of the piston when hydraulic pressure is supplied to both oil chambers. There is no big difference between the braking force when hydraulic pressure is supplied only to the first oil chamber to give the characteristic, and the braking force when hydraulic pressure is supplied to both oil chambers to cancel the one-way characteristic. Therefore, even if hydraulic pressure is supplied to the second oil chamber to cancel the one-way characteristic during a gear shift during braking by supplying hydraulic pressure to the first oil chamber, there will be no sudden or significant change in the output shaft torque. As a result, the brake device of the present invention can be used in either a brake device with one-way characteristics or a normal brake device without one-way characteristics, and can effectively improve shift shock. There is no particular restriction on the timing of supplying hydraulic pressure to the hydraulic pressure, which has the effect of simplifying control of the hydraulic pressure. Furthermore, since no large tension is applied to the brake band, its durability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a partially enlarged sectional view showing the valve R@, and FIG. A diagram showing temporal changes in chamber pressure, brake torque, and output shaft torque, FIG. 4 is a sectional view showing another embodiment of the present invention, and FIG. 5 shows a brake device already proposed by the applicant. FIG. 6, which is a schematic diagram illustrating the principle, is a diagram showing temporal changes in the pressure in each oil chamber, brake torque, and output shaft torque in a situation where shift shock occurs due to inappropriate oil pressure supply timing. 20... Brake drum, 21... Transmission case, 22... Brake band, 23.
... Part of the first anchor, 25 ... Anchor rod, 2
9... Connecting rod, 31... Part of second anchor, 3
2... Hydraulic servo cylinder, 33... Piston,
34...Push rod, 37...Pulp sleeve, 38...Oil passage, 40...Valve seat, 41...
11 valves, 43...first oil chamber, 44...second oil chamber. Applicant Toyota Motor Corporation Agent Patent Attorney Agriculture 1) Takehisa (and 1 other person) Cause 1 Figure 2 Figure 5 Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] A brake band is arranged on the outer circumferential side of a rotating body arranged in a case, and both ends of the brake band are brought close to each other by an anchor rod and a push rod to tighten the brake band and brake the rotating body. In the brake device, a fluid pressure cylinder that moves back and forth in a tangential direction of the rotating body is arranged in a position facing the anchor rod in the case, the push rod is attached to the piston of the fluid pressure cylinder, and the fluid pressure is The cylinder and the anchor rod are connected so as to move together, and a first oil chamber is formed on the opposite side of the hydraulic cylinder from the push rod across the piston, and and a second one on the opposite side of the push rod.
An oil chamber is formed, and a valve mechanism is provided that opens the oil chambers to communicate with each other when the fluid pressure cylinder retreats to the second oil chamber side, and when hydraulic pressure is supplied only to the first oil chamber, the piston A brake for an automatic transmission, characterized in that the area where the piston receives hydraulic pressure is approximately equal to the area where the piston receives hydraulic pressure when hydraulic pressure is supplied to both the first oil chamber and the second oil chamber. Device.