JPS6363775B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a creep prevention device for a vehicle with an automatic transmission.

If a vehicle equipped with an automatic transmission is set to the drive position (forward position) while the vehicle is stopped, the drag torque of the torque converter will cause
This indicates a so-called creep phenomenon in which the vehicle tries to move forward against the driver's will. This creep force attempts to apply a braking force to the engine during idling, so in order to keep the engine speed at the reference value during idling, the throttle opening during idling must be adjusted to compensate for this braking force. This naturally increases fuel consumption, which is one of the main reasons for the poor fuel efficiency of vehicles with automatic transmissions.

Therefore, the present applicant detected when the vehicle was idling and diverted the pressure of the starting clutch to the oil tank to cut off the power transmission between the engine and the wheels, thereby reducing the load on the engine to the same level as that of vehicles with manual transmissions. We first proposed an improvement plan that would make this possible. However, in an automatic transmission in which a gear train (for example, a low gear gear train) during idling operation is also used during engine braking, the following inconvenience may occur. In other words, there is no problem when all systems are operating normally, but if the system is held in a creep prevention state due to some kind of failure, the engine brake in the low-speed gear train will hardly be effective. Vehicles that have shift positions so that engine braking is effective in this low-speed gear train rely only on the foot brake, so some kind of countermeasure was desired. Here, examples of possible failures such as those described above include cases where the sensor system malfunctions and the vehicle is mistakenly judged to be idling even though the vehicle is in motion, or there is a malfunction in the actuator even though the sensor system and judgment system are normal. There are cases where the creep prevention state is maintained due to In particular, it is conceivable that the hydraulic switching valve, which is the final actuator, may not operate smoothly due to dirt in the oil or the like, and may not be able to return to the inoperative position because the spring force of the return spring is weak.

Note that this type of problem does not occur in vehicles that do not have a shift position that allows engine braking to be applied in the low-speed gear train. However, with models that apply engine braking using a medium-speed gear train, it is not possible to freely reduce the gear ratio of the medium-speed gear train in order to secure necessary and sufficient braking performance. The restrictions above were significant.

The present invention has been made in view of these problems, and provides an automatic transmission in which the creep phenomenon in the gear train for starting is prevented and engine braking is possible in the gear train. An object of the present invention is to provide a creep prevention device for a vehicle with an automatic transmission, which enables engine braking to be effective even if the creep prevention mechanism fails in its operating position.

To achieve such an object, the device of the present invention includes a starting oil passage that communicates with a hydraulic pressure source when the manual switching valve is set to the starting position and is provided with a throttle in the middle for throttling the working pressure from the hydraulic source; an engine brake oil passage that leads to a hydraulic pressure source when the valve is in the engine brake position; and a switching operation of the manual switching valve, which is interposed between the starting oil passage, the engine brake oil passage, and the hydraulic oil passage. an oil passage switching control valve that communicates the starting oil passage with the hydraulic oil passage when starting, and communicates the engine brake oil passage with the hydraulic oil passage during engine braking in conjunction with the engine braking.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. First, in FIG. 1, which shows an outline of an automatic transmission for an automobile with three forward speeds and one reverse speed, the output of the engine E is transferred from its crankshaft 1 to the torque converter. T, auxiliary transmission M, and differential gear Df, the signal is transmitted to the drive wheels W and W' in order to drive them.

The torque converter T includes a pump impeller 2 connected to a crankshaft 1, a turbine impeller 3 connected to an input shaft 5 of an auxiliary transmission M, and a stator shaft 4a supported on the input shaft 5 so as to be relatively rotatable. It is composed of a stator wheel 4 connected via a one-way clutch 7. The torque transmitted from the crankshaft 1 to the pump impeller 2 is hydrodynamically transmitted to the turbine impeller 3, and during this time, when the torque is amplified,
As is known, the stator wheel 4 bears the reaction force.

A pump drive gear 8 for driving the hydraulic pump P shown in FIG. 2 is provided at the right end of the pump impeller 2, and a stator arm 4b for controlling the regulator valve Vr shown in FIG. 2 is fixed at the right end of the stator shaft 4a. will be established.

The input and output shafts 5 of the auxiliary transmission M are parallel to each other.
Between 6 and 6 are a low speed gear train G ₁ for starting and engine braking, a medium speed gear train G ₂ , a high speed gear train G ₃ ,
and a reverse gear train Gr are provided in parallel. The low speed gear train _G1 has a low speed clutch on the input shaft 5 as a frictional engagement element for starting and engine braking.
A driving gear 17 connected via C ₁ and a driven gear 1 fixed to the output shaft 6 and meshing with the gear 17.
8, and the medium speed gear train _G2 includes a drive gear 19 connected to the input shaft 5 via a medium speed clutch _C2 , and a drive gear 19 connected to the output shaft 6 via a switching clutch Cs. The high-speed gear train _G3 is composed of a gear 19 and a driven gear 20 meshing with each other.
The reverse gear train Gr is composed of a driving gear 21 fixed to the input shaft 5 and a driven gear 22 connected to the output shaft ₆ via a high speed gear clutch _C3 . A drive gear 23 integrally formed with the drive gear 19 and the switching clutch on the output shaft 6
It is composed of a driven gear 24 connected via Cs, and an idle gear 25 meshing with both the gears 23 and 24 mentioned above. The switching clutch Cs is provided between the driven gears 20 and 24, and the switching clutch Cs is provided between the driven gears 20 and 24.
The driven gears 20, 24 can be selectively coupled to the output shaft 6 by shifting the Cs selector sleeve 26 to the forward position on the left or the reverse position on the right in the figure.

Thus, when the selector sleeve 26 is held in the forward position as shown, the low gear clutch is
If only C ₁ is connected, the drive gear 17 will be connected to the input shaft 5.
A low speed gear train G ₁ is established, and torque is transmitted from the input shaft 5 to the output shaft 6 via this gear train G ₁ . Next, if the middle gear clutch _C2 is connected while the low gear clutch _C1 remains in the disconnected state,
The drive gear 19 is connected to the input shaft 5 to establish a medium speed gear train _G2 , and the input shaft 5 is connected to the input shaft ₅ through this gear train G2.
Torque is transmitted from the output shaft 6 to the output shaft 6. Furthermore, if the low speed gear clutch C ₁ and the middle speed gear clutch C ₂ are disconnected and the high speed gear clutch C ₃ is connected, the driven gear 22 is connected to the output shaft 6 and the high speed gear train is connected.
_G3 is established, and torque is transmitted from the input shaft 5 to the output shaft 6 via this gear train _G3 . Next, by switching the selector sleeve 26 to the right reverse position and connecting only the middle gear clutch _C2 , the drive gear 23
is connected to the input shaft 5, and the driven gear 24 is connected to the output shaft 6 to establish a reverse gear train Gr, and torque is transmitted from the input shaft 5 to the output shaft 6 via this gear train Gr.

The torque transmitted to the output shaft 6 is transmitted from the output gear 27 provided at the end of the shaft 6 to the large diameter gear 28 of the differential device Df.

In Fig. 2, a hydraulic pump P as a hydraulic source
sucks up oil from the oil tank R and connects it to the hydraulic oil passage 29.
to be pumped to. After this pressure oil is regulated to a predetermined pressure by a regulator valve Vr, it is sent to a manual valve Vm as a manual switching valve. This oil pressure is called line pressure Pl.

The regulator valve Vr has a pressure regulating spring 30 and a spring receiver 31 that supports the outer end of the spring receiver 31, and the spring receiver 31 can be moved left and right to adjust the set load of the pressure regulating spring 30. . This spring receiver 3
The stator arm 4b is in contact with the outer surface of the stator wheel 4 so as to apply a reaction force acting on the stator wheel 4, that is, a stator reaction force, and the spring receiver 31 is provided with a stator arm 4b for supporting the stator reaction force. Spring 3
2 is connected. Therefore, if the stator reaction force increases, the stator spring 32 will be compressed, and accordingly the spring receiver 31 will move to the left, increasing the set load of the pressure regulating spring 30, and as a result, the hydraulic oil passage 29 will be compressed. Line pressure Pl is increased.

A part of the pressure oil whose pressure is regulated by the regulator valve Vr is guided into the torque converter T through an inlet oil passage 34 having a throttle 33, and pressurizes the inside of the torque converter T to prevent cavitation, but this internal pressure is It is determined by the size of the throttle 33 and the strength of the spring 37 of the check valve 36 provided in the outlet oil passage 35 of the torque converter T.

The oil that has passed through the check valve 36 is sent to the oil cooler 5.
6 and return to oil tank R.

The surplus of pressure oil discharged from the hydraulic pump P is guided to the lubricating oil path 38 from the regulator valve Vr and sent to each lubricating part, but in order to ensure the minimum necessary oil pressure at this time, the pressure regulating valve 39 is installed. It is connected to the lubricating oil path 38.

Pressure oil sent to the spool valve body 130 of the manual valve Vm is sent to any of the clutches C ₁ , C ₂ , C ₃ and other various hydraulic operating parts when the valve Vm is in the neutral position shown. There is no. Therefore, all three clutches C ₁ , C ₂ , C ₃ are disengaged, and the torque of the engine E is applied to the wheels W,
Not transmitted to W′.

When the manual valve Vm is moved one step to the left from the illustrated position and shifted to the drive position D, the hydraulic oil passage 29 from the hydraulic pump P communicates with the oil passages 43 and 118, and the starting oil passage 111 communicates with the oil passage 118. low gear clutch
Hydraulic oil passage 41 leading to hydraulic cylinder 40a of _C1
Connects to a. Also, the oil passage 112 is connected to the middle gear clutch.
Hydraulic oil passage 41 leading to hydraulic cylinder 40b of _C2
b, and the oil passage 113a is also connected to the discharge port 114.
be cut off from. Oil passage 115 continues to communicate with discharge port 116. The hydraulic oil passage 43 communicates with a spring chamber 42 of a hydraulic servo motor Sm for shifting the selector sleeve 26, so that the piston 44 of the servo motor Sm remains in the leftward movement position shown in the figure and moves the shift fork 45. The selector sleeve 26 is held in the forward position shown in FIG. Therefore, the reverse gear train Gr is placed in an inactive state.

An input oil passage 46 that connects to the input port of the governor valve Vg branches from the hydraulic oil passage 29, and a first signal oil passage 47 extends from the output port of the valve Vg.

The governor valve Vg is a known one, and is rotated around its own rotation axis 49 by a gear 48 meshing with the large-diameter gear 28 of the differential device Df. Therefore, since its rotational speed is proportional to the vehicle speed, the governor valve Vg transmits the hydraulic pressure proportional to the vehicle speed, that is, the governor pressure Pg, to the first signal oil path by the action of the centrifugal force acting on the weight 51 of the spool valve body 50. 47.

Further, an oil passage 53 branches from the hydraulic oil passage 43, and this oil passage 53 is connected to the first throttle valve Vt ₁ via a modulator valve 54. The modulator valve 54 is a pressure reducing valve that is biased toward the closing side by a spring force and opened by the modulator pressure of the output port 54a, and defines the upper limit value of the inlet pressure of the first throttle valve _Vt1 .

The first throttle valve Vt ₁ is of a known type, and includes a spool valve body 55, a control spring 58 that presses the valve body 55 to the left, and a return spring 5 that presses the valve body 55 to the right.
7. Control piston 59 that supports the outer end of control spring 58, control cam 60 that rotates in conjunction with the increase in opening of the throttle valve of engine E and moves control piston 59 to the left, and adjusts the set load of return spring 57. It has an adjustment bolt 61 etc. that can be adjusted. When the control piston 59 moves to the left, the displacement is transferred to the spool valve body 55 via the control spring 58 and pushes it to the left, but the hydraulic pressure output to the second signal oil path 52 due to this left movement is applied to the spool valve body 55. Since the left shoulder portion 55a of the spool valve body 55 acts to push the body 55 back to the right, the first
The throttle valve Vt ₁ outputs a hydraulic pressure proportional to the opening degree of the throttle valve of the engine E, that is, a throttle pressure Pt, to the second signal oil path 52 . In addition, the control cam 60
The rotation in the counterclockwise direction continuously restricts the communication between the oil passage 117 and the oil tank R.

The first and second signal oil passages 47, 52 are pilot hydraulic chambers 62a, 62b, 63a, 63 at both ends of the low-medium speed shift valve _V1 and the medium-high speed shift valve _V2 , respectively.
b, respectively. As a result, the spool valves 64 and 65 of the shift valves V ₁ and V ₂ receive the governor pressure Pg and throttle pressure Pt on both end faces and are operated as follows.

That is, the spool valve body 6 of the low-medium speed shift valve _V1
4 is initially held at the rightward movement position shown in the figure by the force of the spring 66, and therefore the oil passage 118 is closed to the one-way throttle 7.
Hydraulic oil passage 4 via starting oil passage 111 provided with 5
1a, and the low gear clutch _C1 is engaged under pressure. Next, the vehicle speed increases and the governor pressure Pg increases, and when the left power of the spool valve element 64 due to the governor pressure Pg overcomes the right power of the valve element 64 due to the throttle pressure Pt and the spring 66, the force of the valve element 64 increases. A click ball 68 that moves together with the valve body 64 in a click motion mechanism 67 provided at the right end crosses over a fixed positioning protrusion 69 and moves the valve body 64.
quickly switches to the left moving position. Thereby, the starting oil passage 111 communicates with the drain oil passage 119, and the oil passage 118 communicates with the oil passage 70. Further, the oil passage 70 is blocked from the drain oil passage 120. In this state...
If high-speed shift valve V ₂ is in the position shown, oil line 7
0 communicates with an oil passage 113 equipped with a one-way throttle 121, and further communicates with a hydraulic oil passage 4 via a manual valve Vm.
1b. Therefore, the hydraulic cylinder 40b
Hydraulic oil is supplied to C2, and the middle speed clutch _C2 is engaged under pressure. As a result, the middle speed gear train _G2 is established.

As the vehicle speed increases further, the medium-high speed shift valve
A similar effect occurs in valve V ₂ , and the spool valve body 65 of the valve V ₂ moves to the left due to the increasing governor pressure Pg.
The oil passage 113 is communicated with the drain oil passage 122, the oil passage 70 is communicated with the hydraulic oil passage 41c leading to the hydraulic cylinder 40c of the high speed clutch _C3 , and the hydraulic oil passage 41c is isolated from the drain oil passage 123. Accordingly, the middle gear clutch _C2 is released from its engagement state, and the high gear clutch _C3 is pressurized into engagement to establish the gear train _G3 of the high gear gear.

In order to relieve the shock during gear shifting, accumulators 72, 73, 74 are hydraulically connected in parallel to each clutch C ₁ , C ₂ , C ₃ . Further, the drain oil passage 119 is provided with a 1-2 orifice control valve 124, and the drain oil passage 122 is provided with a 2-3 orifice control valve 125.

Back pressure chamber 7 of each accumulator 72, 73, 74
The control hydraulic pressure Pc from the second throttle valve Vt ₂ is guided to 7, 78, and 79 via the oil passage 106. This second throttle valve Vt ₂ is inserted between an oil passage 105 branched from the oil passage 53 and the oil passage 106, and includes a spool valve body 107 and a control spring that presses the valve body 107 to the left. 108, a control piston 109 that supports the outer end of the control spring 108, and a control cam 110 that rotates in conjunction with an increase in the throttle opening of the engine E and moves the control piston 109 to the left. When the control piston 109 moves to the left, the displacement is transferred to the spool valve body 10 via the control spring 108.
7, and the spool valve body 107 moves to the left. The hydraulic pressure output to the oil passage 106 in conjunction with this leftward movement acts on the left shoulder portion 107a of the spool valve body 107 so as to push the spool valve body 107 back to the right. Due to this operation, the second throttle valve _Vt2 maintains a control oil pressure Pc proportional to the throttle opening of the engine E.
are connected to each accumulator 72 through the oil passage 106.
This will be applied to the back pressure chambers 77 to 79 of 74. Note that the counterclockwise rotation of the control cam 110 continuously restricts the communication between the drain oil passage 120 and the oil tank R.

During deceleration, the valve body 65 of medium-high speed shift valve _V2
first moves to the right and changes from the speed ratio of the high speed gear to the speed ratio of the medium speed, and when the speed further decreases, the valve body 64 of the low-medium speed shift valve _V1 moves to the right and changes to the speed ratio of the low speed. It is important that at such a speed ratio of the low gear at drive position D, the hydraulic oil supplied to the low gear clutch _C1 passes through the one-way throttle 75.

For engine braking, which communicates with the hydraulic pump P via the oil passage 43 and the hydraulic oil passage 29 when the starting oil passage 111 equipped with the one-way throttle 75 and the manual valve Vm are in the engine braking position, that is, the first gear holding position I. An oil passage switching control valve Vo interlocked with the manual valve Vm is interposed between the oil passage 126 and the hydraulic oil passage 41a communicating with the hydraulic cylinder 40a. This switching control valve Vo is a manual valve.
It has a spool valve body 130 common to the manual valve Vm, and when the manual valve Vm is at the starting position, that is, the drive position D, the spool valve body 130
When the manual valve Vm is in the engine brake position, that is, the first gear holding position I, the engine brake oil passage 126 is connected to the hydraulic oil passage 41a by the spool valve body 130. communicate.

An intermediate portion of the hydraulic oil passage 41a is connected to the accumulator 72, and an oil passage 84 short-circuited to the oil tank R is connected to an intermediate portion of the hydraulic oil passage 41a. A pilot type creep prevention valve Vc is inserted in the middle of this oil passage 84 as a creep prevention means.

The creep prevention valve Vc has a spool valve body 85, and the spool valve body 85 has a cylindrical shape formed in the middle part so as to divide the oil passage 84 into an upstream part 84a and a downstream part 84b. valve chamber 8
6, thereby defining oil chambers 87 and 88 at the upper and lower portions of the valve body 85. A return spring 89 that urges the spool valve body 85 downward is housed in the upper oil chamber 87 . The spool valve body 85 is
A pair of upper and lower lands 90 and 91, an annular groove 92 sandwiched between them, and this groove 92 connected to the upper oil chamber 87.
and an orifice 9 communicating with the lower oil chamber 88
3,94. The annular groove 92 is located at the upstream portion 84a.
The upper land 90 opens and closes the opening port 95 to the valve chamber 86 in the downstream portion 84b by its vertical movement. The port 95 is preferably formed to have a circular cross-sectional shape so that its effective opening area gradually increases as the upper land 90 moves upward. An end wall member 97 having an orifice 96 is provided at the upper end of the valve chamber 86, and an electromagnetic valve 99 having a pilot needle valve 98 for opening and closing the orifice 96 is disposed above the end wall member 97. This needle valve 98 closes the orifice 96 by the spring force of the spring 100, and opens the orifice 96 when the solenoid 101 is energized. Further, the orifice 96 is configured to communicate with a bypass oil passage 102 branched from the downstream portion 84b of the oil passage 84 when the orifice 96 is opened.

Solenoid 101 is energized and orifice 96
When the upper oil chamber 87 is opened, the upper oil chamber 87 communicates with the oil tank R via the orifice 96 and the bypass oil passage 102, so the oil pressure in the upper oil chamber 87 decreases, and the spool valve body 85 faces the lower oil chamber 88. It moves upward by the force acting on the lower end surface and opens the oil passage 84. At this time, the hydraulic oil passage 41a, in other words, the pressure of the low gear clutch _C1 is the pressure of the return spring 89 and the spool valve body 85.
The creep phenomenon can be prevented by setting the pressure below the engagement pressure of the low gear clutch _C1 . Note that when the valve body 64 of the low-to-medium speed shift valve V ₁ or the valve body 65 of the medium-to-high speed shift valve V ₂ moves to the left to establish the speed ratio of the medium or high speed gear, the hydraulic oil path Since the oil pressure of 41a is zero, the spool valve body 85 does not move upward, and the creep prevention valve Vc does not operate.

The solenoid 101 of the electromagnetic valve 99 is grounded via a transistor 140, and the base of this transistor 140 is connected via a resistor 146 to an AND terminal.
The output of gate 141 is provided. At the input end of the AND gate 141, there is a shift position sensor 142 that outputs a high-level signal when the shift lever is shifted to drive position D, and a shift position sensor 142 that detects the rotational speed of the engine E and detects the rotational speed of the engine E and detects the rotational speed of the engine E when the rotational speed is below a reference value. An engine speed sensor 143 that outputs a high level signal, and a braking sensor 144 that outputs a high level signal when the brake pedal is depressed.
and a throttle sensor 14 that outputs a high level signal when the accelerator pedal is in the idle position.
5 is connected. Therefore, when the vehicle is stopped by placing the foot on the brake pedal at an intersection or the like, the outputs of the sensors 142 to 145 all become high level, the solenoid 101 is energized, and the creep prevention valve Vc is opened. Creep phenomenon is prevented from occurring.

In order to prevent such creep, the throttle 75 provided in the middle of the starting oil passage 111 plays an important role. Here, the diameter of the throttle 75 is d, and the diameter of the downstream portion 84b of the oil passage 84 in the creep prevention valve Vc is
Di, the discharge pressure of the hydraulic pump P is Pl, and the hydraulic pressure of the hydraulic oil passage 41a is p, the following equation holds true.

πd ² /4√−=πDi ² /4√ Here, Pl=8.5Kg/cm ² , p=1.0Kg/cm ² , d=1.7
If mm, Di=2.8mm. Actually, Di is set to 5 to 6 mmφ because other elements are involved, but Di does not have such a large value. Further, the anti-creep valve Vc is arranged as close as possible to the low gear clutch _C1 in order to improve responsiveness at the time of starting.

In FIG. 3, when the manual valve Vm is shifted to a shift position other than the drive position D, for example, to the first gear engine brake position, that is, the first gear holding position, the hydraulic oil passage 41a is shifted to the starting position in accordance with the movement of the valve body 80. The starting oil passage 111. is cut off from the oil passage 111. Engine brake oil passage 1 parallel to
It communicates with the oil passage 43 via 26, and further communicates with the hydraulic oil passage 29 connected to the hydraulic pump P. Therefore, the hydraulic pump P and the hydraulic cylinder 40a of the low gear clutch _C1 are in direct communication without going through the one-way throttle 75 in the starting oil passage 111, and by the engagement of the low gear clutch _C1 , The low speed gear train _G1 is established and engine braking is applied.

Next, when the manual valve Vm is shifted to the middle gear holding position or the reverse drive position Re, only the middle gear clutch _C2 is engaged, and the middle gear train _G2 or the reverse gear train Gr is established. Especially when shifting to reverse position Re, piston 4 of servo motor Sm
4 receives pressure oil on its left end surface, and the spring chamber 42 is connected to the oil tank R, so the piston 44 moves to the right and the reverse gear train Gr is established. Note that among the shift positions of the manual valve Vm, Pk indicates the parking position.

Next, to explain the operation of this embodiment, when the manual valve Vm is shifted to the drive position D and the vehicle speed is decelerated and the vehicle is tried to stop while driving,
Medium-high speed shift valve V ₂ and low-speed shift valve V ₁
The valve bodies 65 and 64 move to the right, and the oil passage 118 communicates with the starting oil passage 111, and a hydraulic pressure of, for example, about 1 kg/cm ² is supplied to the hydraulic oil passage 41a by the throttle effect of the throttle 75. , the low gear clutch _C1 is engaged.
When the vehicle stops at an intersection, etc., the anti-creep valve
Vc opens, the oil pressure of the hydraulic cylinder 40a drops below the engagement pressure, and the engagement state of the low gear clutch _C1 is released, thus making it possible to prevent the creep phenomenon from occurring.

Here, the creep prevention valve Vc opens due to internal firing of the transistor 140 or due to the creep prevention valve Vc being inoperable due to dirt in the oil or the like and the spring force of the return spring 89 being weak. Let's assume that you want to apply engine braking when the vehicle is stuck in the same state. When applying this engine brake, the manual valve Vm is shifted to the engine brake position, that is, the first gear holding position, which causes the starting oil passage 111 to become the hydraulic oil passage 41a, as explained in FIG. 3 above. The engine brake oil passage 126, which is blocked and communicated with the hydraulic pump P, is communicated with the hydraulic oil passage 41a.
Therefore, for example, 8.5 kg/
A high pump discharge pressure of about cm ² is directly introduced, and even if the creep prevention valve Vc remains open, the hydraulic cylinder 40a has the pressure necessary to engage the low gear clutch _C1 . Engagement pressure is introduced. Therefore, the low speed gear train _G1 is established and engine braking can be applied even though the anti-creep valve Vc remains open.

The engagement pressure of the low speed clutch C ₁ at this time depends on the gear ratio of the low speed gear train G ₁ , but it does not need to be so large.
This can be easily understood by noting that 8.5 kg/cm ² is the necessary and sufficient pressure to transmit the maximum torque of the engine E, and that the engine brake is an internal friction torque that merely causes the engine E to idle.

As described above, according to the present invention, when the manual switching valve is in the starting position, the starting oil passage having a throttle and leading to the hydraulic pressure source is communicated with the hydraulic oil passage leading to the frictional engagement element, and during engine braking, Since the engine brake oil passage leading to the oil pressure source is communicated with the hydraulic oil passage, the oil pressure throttled at the time of starting is reduced to a certain value or less by opening the creep prevention valve, thereby achieving a creep prevention state. Even if the creep prevention valve malfunctions in the creep prevention state during engine braking, the oil pressure that is not throttled by the throttle is supplied from the engine brake oil passage to the hydraulic oil passage, so the creep prevention valve Even if the friction engagement element remains open, it is possible to supply hydraulic pressure above a certain value necessary for the friction engagement element to operate, and therefore, even in the unlikely event of a failure, the engine brake can be applied reliably. becomes possible.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic diagram of an automatic transmission with three forward speeds and one reverse speed to which the present invention is applied, and FIG. 2 is a hydraulic circuit diagram thereof.
FIG. 3 is a diagram showing the connection state of the oil passages when the manual valve is in the engine braking position. C ₁ ...Low gear clutch as a frictional engagement element,
G ₁ ...Low speed gear train for starting and engine braking, M...Auxiliary transmission, T...Torque converter,
P...Hydraulic pump as a hydraulic power source, R...Oil tank,
Vc...creep prevention valve, Vm...manual valve as manual switching valve, Vo...oil path switching control valve, 41a
... Hydraulic oil path, 75... Throttle, 111... Starting oil path,
126...Engine brake oil path.

Claims (1)

[Claims] 1 A hydraulic torque converter T; connected to the torque converter T with a frictional engagement element _C1 for establishing a gear train _G1 for starting and engine braking in response to the action of a hydraulic pressure higher than a certain hydraulic pressure; an auxiliary transmission M; a hydraulic oil passage 41a communicating with the frictional engagement element _C1 at the switching position for starting and the switching position for engine braking in order to establish the starting and engine braking gear train _G1 ; A manual switching valve Vm capable of communicating the oil pressure with a hydraulic pressure source P; and a creep prevention valve Vc which is interposed in the middle of the hydraulic oil passage 41a and between the oil tank R and opens when the vehicle is idling. In a creep prevention device for a motorized vehicle, a starting oil passage 111 that communicates with a hydraulic pressure source P when the manual switching valve Vm is set to the starting position and includes a throttle 75 in the middle for throttling the working hydraulic pressure from the hydraulic source P; an engine brake oil passage 126 that leads to the hydraulic pressure source P when the manual switching valve Vm is set to the engine brake position; the starting oil passage 111 and the engine brake oil passage 12;
6, and is interposed between the hydraulic oil passage 41a,
In conjunction with the switching operation of the manual switching valve Vm, when starting, the starting oil passage 111 is switched to the hydraulic oil passage 41a.
and an oil passage switching control valve Vo that communicates the engine brake oil passage 126 with the hydraulic oil passage 41a during engine braking.