JPH054543B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to an engine brake control device for an automatic transmission. (Prior Art) Automatic transmissions are generally configured to automatically change gears by switching power transmission paths through selective hydraulic actuation of various friction elements. A one-way clutch is provided as a reaction force element for the rotating member, and the above-mentioned power transmission is made possible by receiving the reaction force from the rotating member by operating the one-way clutch. Therefore, when a reverse drive torque is applied to the rotating member, the one-way clutch cuts off the reverse drive torque by releasing the one-way clutch.
Although the one-way clutch can prevent the occurrence of shock, rattling noise, and jerking vibrations, the one-way clutch does not provide engine braking. Therefore, in a typical automatic transmission, an engine braking friction element is provided in parallel with the one-way clutch, and this friction element is operated as appropriate to apply engine braking. By the way, when this engine braking friction element is used for engine braking at multiple gears, the required capacity is, for example, at the highest speed among the gears, as seen in the THM-700 type transmission manufactured by General Motors Corporation in the United States. The engine braking in one gear is considerably smaller than the engine braking in other gears. Conventionally, in order to match the capacity of the friction element for engine braking to the required capacity for each gear, the line pressure of the automatic transmission that controls the operation of the element is kept at normal during engine braking at the highest gear. , it has been customary to increase the engine braking level higher than normal when applying engine braking at the other gears. (Problem to be Solved by the Invention) However, the line pressure is also used to operate the transmission friction element, and the normal value cannot be set below a predetermined value commensurate with the required capacity. Therefore, during engine braking at the highest speed in which the engine braking friction element is actuated by the normal line pressure, there is a problem in that the capacity of the friction element becomes excessive, resulting in a large engine braking shock. From this point of view, the present invention basically controls the capacity of the engine braking friction element not by controlling the line pressure as in the past, but by controlling the hydraulic pressure of the element for each gear. In other words, when the engine is braking at the highest gear, the line pressure is reduced and used as the working oil pressure, and when the engine is braking at other gears, the line pressure is directly used as the working oil pressure, thereby reducing engine braking friction. The purpose of this is to make it possible to match the engagement capacity of the element with the required capacity at any gear stage, thereby solving the above-mentioned problem. By the way, the technology for directly controlling the hydraulic pressure of the friction element for engine braking was previously disclosed in Japanese Patent Application Laid-Open No. 1986-
This is proposed by Publication No. 137752. This conventional technology is based on a type of automatic transmission in which the low reverse brake, which serves as a friction element for engine braking, also serves as a friction element for reverse selection, and the required capacity of the brake is low during engine braking (1st gear engine braking). ), the line pressure is reduced by the 1st speed pressure reducing valve and used as the working hydraulic pressure of the brake, and when the required capacity of the brake is large, the line pressure is directly passed through the shuttle valve so as to bypass the pressure reducing valve. This is supplied to the low reverse brake as its operating hydraulic pressure. However, this conventional technique requires an extra bypass circuit and a shuttle valve, making the shift control hydraulic circuit complicated and expensive. The present invention constructs an engine brake control device that can control the hydraulic pressure of the engine brake friction element to a value commensurate with the required capacity for each gear without adding any extra circuits or valves. The purpose is to (Means for Solving the Problems) For this purpose, the engine brake control device of the present invention is capable of selecting a plurality of gears in which power is transmitted via one one-way clutch in a manual valve automatic shift range. and, in a state where the highest speed among the plurality of speeds is selected, obtain engine braking at the highest speed by hydraulically operating an engine brake friction element arranged in parallel with the one-way clutch. In the low gear engine brake range, a low gear other than the highest gear from among the plurality of gears is selected by hydraulic pressure output from the low gear engine brake range port of the manual valve, and the engine brake friction Engine braking can be obtained in the low speed gear by hydraulic actuation of the element, and the required capacity of the friction element for engine braking is smaller than that during engine braking in the highest speed gear and engine braking in the low speed gear. In the transmission, a pressure reducing valve that partially removes the working hydraulic pressure to reduce the pressure is inserted into the working hydraulic circuit of the engine brake friction element, and the pressure reducing valve is provided with a pressure reducing limiting chamber that limits the pressure reducing action, and the manual It is characterized by a configuration in which the low speed engine brake range port of the valve is connected to the pressure reduction restriction chamber. (Operation) In the manual valve automatic shift range, the automatic transmission can select a plurality of gears that transmit power through one one-way clutch. If the engine braking friction element is hydraulically actuated with the highest gear selected among these multiple gears, the one-way clutch becomes impossible to release, and engine braking is achieved at the highest gear. be able to. By the way, at this time, the working oil pressure of the friction element for the engine brake is reduced and regulated by the pressure reducing valve, so the capacity of the element does not become more than necessary, and the line pressure, which is the source pressure of the working oil pressure, is Even if the height is increased to match the required capacity of the friction element, it will not cause engine braking shock. On the other hand, when the manual valve is set to the low speed engine brake range, the automatic transmission is put into a low speed speed other than the highest speed by the hydraulic pressure output from the low speed engine brake range port of the manual valve. At the same time, the hydraulic pressure output from the low speed engine brake range port of the manual valve reaches the pressure reduction limiting chamber of the pressure reducing valve and limits the pressure reducing action. Therefore, in the low gear engine brake range,
To enable engine braking at a low speed stage by operating a friction element for engine braking at a higher pressure than during engine braking at the highest speed stage. Therefore, even during engine braking at low speeds where the required capacity of the engine braking friction element is large, the element is prevented from slipping, and reliable engine braking can be achieved. By the way, in order to match the working oil pressure of the friction element for engine braking to the required capacity for each gear, we did not adjust the line pressure, which is the source pressure, but the working oil pressure itself. Even if the line pressure is determined to be high according to the required capacity of the element, the capacity will not become excessive during engine braking at the highest gear, where the capacity of the friction element for engine braking may be small. It is possible to reliably match the capacity of the friction element to the required value for each gear. In addition, in order to achieve such effects, a pressure reduction restriction chamber is provided in the pressure reducing valve and this is connected to the low speed engine brake range port of the manual valve, so a circuit that bypasses the pressure reducing valve, or these pressure reducing valves or bypasses are required. The above effects can be achieved without adding any kind of shuttle valve or the like for distributing hydraulic pressure to the circuit, that is, while keeping the configuration simple and inexpensive. (Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. The drawing shows an example in which the engine brake control device of the present invention is applied to a 4-speed automatic transmission, in which the hydraulic operation of the 4th speed selection friction element 1 works in conjunction with the hydraulic operation of other transmission friction elements. 4th speed (overdrive) is selected, and while friction element 1 is not operating, other gear shifting friction elements are selectively activated to transmit power through a one-way clutch (not shown). After selecting the speed, the engine braking at the first to third speeds is achieved by disabling the one-way clutch from idling by hydraulically operating the engine braking friction element 2 arranged in parallel with the one-way clutch. . In addition, the required capacity of the engine braking friction element 2 is smaller when the engine brakes at the highest gear (third gear) than when the engine brakes at other gears (first gear, second gear). do. In the figure, 3 indicates a manual valve, and when the driver desires to park, the spool 3a is set to the P position, and when the driver desires to reverse, the spool 3a is set to the R position.
range, when you want to stop, put the spool 3a in the N range, and when you want forward automatic shifting, put the spool 3a in the N range.
When 2nd gear engine braking is desired, the spool 3a is set to II range (low gear engine braking range), and when 1st gear engine braking is desired, the spool 3a is set to I range.
range (low speed engine brake range), and output ports 3R and 3 in each range.
It is assumed that D, 3II (low speed engine brake range port) and 3I (low speed engine brake range port) output the line pressure P _L from the line pressure circuit 4 as shown in the following table.

[Table] In this table, ○ marks indicate ports that output line pressure, and unmarked ports indicate ports that are opened to the atmosphere. Reference numeral 5 designates a speed change valve, which is constructed by elastically supporting a spool 5a to the downshift position shown in the right half by a spring 5b, and in this spool position, the port 5c is connected to the drain port 5d, and the speed change pressure P _S in the chamber 5e It is assumed that when the spool 5a is placed in the upshift position shown in the left half, the port 5c communicates with the port 5f. 6 indicates an engine brake control valve;
The spool 6a is resiliently supported at the left half position in the figure by a spring 6b. And at this spool position,
The port 6c communicates with the port 6d, the port 6e communicates with the port 6f, and when the spool 6a is placed in the right half position in the figure due to the pressure of the chamber 6g, the port 6c communicates with the drain port 6h, and the port 6e communicates with the drain port 6i. shall be taken as a thing. Reference numeral 7 designates a pressure reducing valve, which is constructed by elastically supporting a spool 7a at the left half position in the figure by a spring 7b. The spool 7a is moved from this position to the pressure regulating position shown in the right half by the pressure applied to the chamber 7c, and the pressure reducing valve 7 is provided with a port 7d and a drain port 7e which are both closed in this pressure regulating position. Ports 7d, 7e
A port 7f is provided in between. In addition, the lower end of the spool 7a facing the chamber 7c in the figure is made larger in diameter, and a pressure receiving surface 7g is set at the stepped portion, which is connected to the depressurization control chamber 7h.
Let's face it. Hydraulic circuits 8 and 9 for the engine brake friction element 2 are connected to the ports 7d and 7f, respectively, and a check valve 10 is provided to short-circuit the circuits 8 and 9. The working hydraulic circuit 9 on the engine brake friction element 2 side is connected to the chamber 7c via an orifice 11, and the other working hydraulic circuit 8 is connected to the port 6e. Then, the chamber 7h is connected to the port 3II of the manual valve 3 by the circuit 12, and the port 6e is connected to the port 3II of the manual valve 3 by the circuit 12.
3, it is connected to the fourth speed selection friction element 1. Among the other ports 6d and 6i of the engine brake control valve 6, the port 6d is connected to the port 3D of the manual valve 3 by the circuit 15, and the port 6i
are connected to ports 5c of the speed change valve 5 through circuits 16, respectively. A circuit 17 branched from the circuit 15 is connected to the port 5f of the speed change valve 5 on one side, and connected to the chamber 6g of the engine brake control valve 6 on the other side. An orifice 18 is inserted in the middle of the circuit 17, and a solenoid 19 is provided downstream thereof. The solenoid 19 is configured by elastically supporting a plunger 19b at the left half position in the figure by a spring 19a, and connects the circuit 17 to the drain port 19 at this plunger position.
However, when the plunger 19b is moved to the right half position in the figure by the energization of the coil 19d, the above-mentioned interruption is released. Turn on coil 19d,
The OFF state is controlled by the engine brake switch 20, and therefore the coil 19d is connected to the power source 21 via the engine brake switch 20. The engine brake switch 20 is a switch that is manually closed when the driver desires engine braking, but it is assumed that the engine brake switch 20 is also closed even if the driver responds by setting the manual valve 3 to the II or I range. The operation of the above embodiment will be explained next. While the driver desires forward automatic gear shifting and sets the manual valve 3 to the D range as shown in the figure, but does not desire engine braking and opens the engine brake switch 20, the circuits 15 and 17 are connected from port 3D. The output line pressure reaches the chamber 6g because the solenoid 19 is in the left half state in the figure and cuts off the circuit 17 from the drain port 19c, thereby keeping the engine brake control valve 6 in the right half state in the figure. Therefore, through circuit 15, port 6
The line pressure that has reached d reaches a dead end here, and since the circuit 8 is connected to the drain port 6h, hydraulic pressure is not supplied to the engine brake friction element 2.
Keep this inactive. On the other hand, the line pressure output to the circuit 17 also reaches the port 5f of the speed change valve 5. Here, room 5e
If the shift pressure P _S is low and the spool 5a of the shift valve 5 is in the downshift position shown in the right half, circuit 1
6 leads to drain port 5d, and ports 6i, 6e
The circuit 13, which leads to the circuit 16 via the circuit 16, and thus the fourth speed selection friction element 1 is brought to a pressure-free state and is deactivated. At this time, the automatic transmission selects and operates other gear shifting friction elements by line pressure outputted from the manual valve port 3D via a circuit network (not shown), so that the automatic transmission can be shifted to first, second, or third gear. can be selected. When the shift pressure P _S to the chamber 5e increases and the spool 5a of the shift valve 5 is placed in the upshift position shown in the left half, the shift valve 5 reduces the line pressure that has reached the circuit 17 by opening the ports 5f and 5c. circuit 16,
13, it is supplied to the fourth speed selection friction element 1, and it is activated. At this time, the automatic transmission is operated by the fourth friction element 1 and the other gear shifting friction elements.
Select speed (overdrive). When the driver desires engine braking and closes the engine brake switch 20, the coil 19d
Due to the energization, the solenoid 19 is placed in the right half state in the figure, and the circuit 17 is connected to the drain port 19c.
The chamber 6g is made unpressurized, and the engine brake control valve 6 is switched to the left half state in the figure, while the circuit 13 is connected to the drain port 6f to deactivate the fourth speed selection friction element 1. , shifts the automatic transmission from 4th gear to 3rd gear, while circuit 8
is communicated through ports 6c and 6d to circuit 15, and the line pressure that has reached circuit 15 is supplied to engine brake friction element 2 as its working oil pressure through circuits 8 and 9 to operate it. Therefore, the automatic transmission can obtain engine braking in the third gear as specified. By the way, since the manual valve 3 is currently in the D range, the port 3II is used as a drain port, as is clear from Table 1 above, and no pressure is applied to the chamber 7h of the pressure reducing valve 7, and therefore to the spool pressure receiving surface 7g. Therefore, the pressure reducing valve 7 reduces the operating pressure of the engine brake friction element 2 without making it the line pressure itself, by the following action. That is, since the pressure reducing valve 7 is initially in the left half state in the figure, the line pressure reaching the circuit 8 from the circuit 15 is guided to the circuit 9 to increase the working oil pressure of the engine brake friction element 2. This hydraulic pressure is fed back to the chamber 7c via the orifice 11,
The spool 7a is raised against the spring force of the spring 7b as shown in the figure. When the working oil pressure reaches a value corresponding to the spring force of the spring 7b, the spool 7a reaches the pressure regulating position shown in the right half of the diagram, and if the working oil pressure increases further, the spool 7a exceeds this pressure regulating position. When rising, the working oil pressure of the circuit 9 is partially removed from the drain port 7e and decreases. Therefore, the hydraulic pressure of the engine braking friction element 2 is reduced to a value corresponding to the spring force of the spring 7b, and the capacity of the friction element 2 is matched to the small required capacity required during engine braking in the third speed. This can prevent engine brake shock from occurring. If the driver desires engine braking in 2nd or 1st gear, use the manual valve spool 3a.
Set to II range or I range. In these ranges, the engine brake switch 20 is closed as described above, the fourth speed selection friction element 1 is deactivated, and the engine brake friction element 2 is activated in the same manner as described above. On the other hand, as is clear from Table 1 above, in the II range of manual valve 3, line pressure is also output from port 3II, and in the I range, line pressure is also output from port 3I, and the line pressure is output from port 3II as well. The line pressure is output to a circuit network (not shown) to set the automatic transmission to the second gear selection state, and the line pressure from port 3I is output to a circuit network (not shown) to set the automatic transmission to the first gear selection state. . Therefore, in the II range, engine braking can be obtained in the second gear, and in the I range, the engine braking can be obtained in the first gear. By the way, in these II range and I range, the line pressure output from the manual valve port 3II passes through the circuit 12 and reaches the chamber 7h, and acts on the pressure receiving surface 7g to move the pressure reducing valve 7 (spool 7a) to the left half state in the figure. to hold. Therefore, the pressure reducing valve 7 is connected to the port 7f.
The above depressurizing action is stopped (restricted) by not allowing the water to flow through the drain port 7e but through the port 7d.
do. Therefore, the working oil pressure of the friction element 2 for engine braking is the same value as the line pressure, and its capacity is the same as that in 3rd gear (highest gear) during engine braking in 1st and 2nd gears (lower gears). This can be made larger than during engine braking to match the required capacity, and the element 2 can be prevented from slipping. In the above example, the pressure reducing valve spool 7a is held in the left half position in the figure in the II range and the I range, and the engine brake friction element 2 is held in the left half position in the figure.
The working pressure of the pressure-reducing valve spool 7a is set to be the same as the line pressure in the range, but if the capacity of the element 2 is too large for the required capacity, the area of the pressure-receiving surface 7g is reduced and the pressure-reducing valve spool 7a is The pressure reducing valve 7 is designed to prevent the line pressure from the port 3II from being held in the left half position in the figure, and the pressure reducing valve 7 controls the working pressure of the engine brake friction element 2 by the spring force of the spring 7d and the pressure receiving surface 7g. By making the value correspond to the sum of the force due to the line pressure acting on the friction element 2, the capacity of the friction element 2 can be matched to the required capacity. In addition, if you return the manual valve 3 to the D range,
When the engine brake switch 20 is opened in the D range, the solenoid 19 is in the left half state in the figure, the engine brake control valve 6 is in the right half state in the figure, and the engine brake friction element 2 is connected to the drain port 6h. The engine brake can be deactivated and the engine brake can be released, but at this time, the hydraulic pressure of the engine brake friction element 2 is quickly released through the check valve 10 even in the presence of the pressure reducing valve 7.
There is no delay in releasing the engine brake due to a delay in releasing the hydraulic pressure. (Effects of the Invention) Thus, as described above, the engine brake control device of the present invention adjusts the line pressure P _L , which is the source pressure, in order to match the hydraulic pressure of the engine brake friction element 2 to the required capacity for each gear. When braking the engine at the highest gear (third gear in the illustrated example), the hydraulic pressure itself is reduced to a predetermined value by the pressure reducing valve 7, and the required capacity of the friction element for engine braking is reduced to a predetermined value. When the engine brakes at other low gears (in the illustrated example, 2nd and 1st gears), the pressure reduction is limited so that the hydraulic pressure of the element is made higher than when the engine brakes at the highest gear. Therefore, even if the line pressure is high enough to meet the required capacity of the gear shifting friction elements (shifting friction elements including the 4th gear selection friction element 1), the friction element during engine braking at the highest gear. The capacity of the friction element 2 can be made appropriate to prevent engine brake shock from occurring, and the capacity of the friction element 2 can be appropriately increased to prevent it from slipping during engine braking at a low gear. In addition, in order to achieve such effects, the pressure reducing valve 7 is provided with a pressure reduction limiting chamber 7h, which is connected to the low speed engine brake range port 3 of the manual valve 3.
Since it is connected to II, there is no need to add a circuit to bypass the pressure reducing valve 7 or a shuttle valve to distribute hydraulic pressure to these pressure reducing valves or bypass circuits.
The above effects can be achieved while keeping the configuration simple and inexpensive.

[Brief explanation of the drawing]

The drawing is a system diagram showing one embodiment of the engine brake control device of the present invention. 1...Friction element for fourth speed selection, 2...Friction element for engine brake, 3...Manual valve, 3II
...Low speed engine brake range port, 4...
... Line pressure circuit, 5 ... Speed change valve, 6 ... Engine brake control valve, 7 ... Pressure reducing valve, 7h ...
...Decompression restriction chamber, 8, 9...Operating hydraulic circuit for engine brake friction element, 10...Check valve, 11, 18...Orifice, 19...Solenoid, 20...Engine brake switch, 21
……power supply.

Claims (1)

[Claims] 1. In the automatic shift range of the manual valve, it is possible to select a plurality of gears in which power is transmitted via one one-way clutch, and the highest gear of these multiple gears is selected. In this state, engine braking at the highest gear can be obtained by hydraulically operating an engine braking friction element arranged in parallel with the one-way clutch, and in the low gear engine braking, the manual valve is operated at the lower gear. It is possible to select a lower speed gear other than the highest speed gear among the plurality of gears by using the hydraulic pressure output from the engine brake range port, and to obtain engine braking at the low speed gear by hydraulically operating the engine brake friction element. In an automatic transmission in which the required capacity of the engine braking friction element is smaller during engine braking at the highest gear than when engine braking at the lower gear, in the operating hydraulic circuit of the engine braking friction element. , inserting a pressure reducing valve that partially removes the working hydraulic pressure to reduce the pressure, providing this pressure reducing valve with a pressure reducing limiting chamber that limits the pressure reducing action, and connecting a low speed engine brake range port of the manual valve to the pressure reducing limiting chamber. An engine brake control device for an automatic transmission, characterized by comprising: