JPH03229065A - Hydraulic machine type transmission - Google Patents

Abstract

PURPOSE:To reduce each size of a filter and a pipeline, etc., in the midway in a passage as well as to miniaturize an auxiliary pump by feeding an excess flow being produced by a priority valve, installed at the discharge port side of this auxiliary pump, back to the suction side via an injector. CONSTITUTION:If rotational frequency in a prime mover 13 goes up and discharge quantity increases more than the necessary, an excess flow (q) is cut by a priority valve 31, so that a proper quantity of flow is always transferrable to a target circuit connected to the downstream. Accordingly, an upper limit of the flow is determined, and such a fact that a filter 21 and a pipeline, etc., are made smaller in size as little as possible in accord with the flow quantity in advance becomes facilitated. Since the excess flow (q) cut is fed back to the side of a pump inlet port 20b via an injector, the inlet bore is allowed smaller as compared with the case that all the excess flow is dropped in a tank, leading to load reduction in the prime mover 13 too. As suction performance is also improved by an injection effect, and pump operating efficiency is well improved, thus miniaturization of an auxiliary pump 20 is made possible as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydromechanical transmission widely used in automobiles, general industrial vehicles, various hydraulic machines, and the like.

[Prior Art] For example, a hydromechanical continuously variable transmission (HMT) shown in FIG. 4 is an example of a hydromechanical transmission. This transmission is proposed in Japanese Patent Application No. 62'-335655, and includes a sun gear 1, a planetary gear 2, a ring gear 3, and a planetary gear mechanism 5 in which an input shaft 4 is connected to the planetary gear 2. 5 as the main component, a low-speed mechanical transmission system a formed in the direction from the planetary gear 2 to the sun gear 1, and a high-speed mechanical transmission system formed in the direction from the planetary gear 2 to the ring gear 3, these machines Low speed transmission end a for formula transmission systems a and b. One variable displacement fluid pump/motor 7 is placed near the
Connect the input/output shaft 7a of the high-speed side transmission end. By connecting the input/output shaft 8a of the other variable displacement fluid pump/motor 8 in the vicinity of the hydraulic drive system, variable speed fluid transmission systems A and B are formed in parallel to the mechanical transmission systems a and b. circuit 9 and the low speed transmission end a. The low-speed side clutch 11 connects and disconnects the output shaft 10 to the high-speed side transmission end. and a high-speed side clutch 12 that connects and disconnects the output shaft 10 to and from the output shaft 10.

An engine 1 serving as a prime mover is connected to the input shaft 4 of this transmission.
3, the wheels 15 are mounted on the output shaft 10 via the differential gear 14, and the wheels 15 are selectively set in the low speed mode or the high speed mode by performing contradictory switching operations for both clutches 11 and 12. It becomes possible to drive. That is, by engaging the clutch 11 and disengaging the clutch 12 at low speeds, the engine power is divided in parallel at the time of input, and a portion is transmitted to the output shaft 10 through the mechanical transmission system a on the low speed side. The rest will be transmitted to the output shaft 10 through the fluid transmission system A, and conversely, at high speeds, the clutch 12 will be engaged and the clutch 11 will be disengaged.
Part of the engine power is transmitted to the output shaft 10 through the high-speed mechanical transmission system, and the rest is transmitted to the output shaft 10 through the hydraulic transmission system B.

By the way, since drain (leakage) always occurs in the pump/motor 7.8 mentioned above, in order to properly operate the hydraulic drive circuit 9, an auxiliary pump 20 is attached as shown in the figure.
From this auxiliary pump 20 to the filter 21 and the relief valve 22
A boost flow rate must be intermittently supplied to the hydraulic drive circuit 9 via the hydraulic drive circuit 9 or the like. It is advisable to use a fixed capacity type for this auxiliary pump 20, which is advantageous in terms of cost, weight, etc., and to connect it to the input shaft 4 of the engine 13 to utilize its power. In addition, the clutches 11 in the mechanical transmission systems a and b
．． 12 is a hydraulic control circuit 23 equipped with an actuator and the like.
In most cases, the hydraulic pressure control circuits 23 and 24 are driven by the auxiliary pump 20, and the control flow rate required for control by these hydraulic pressure control circuits 23 and 24 is preferably covered by the auxiliary pump 20, if possible, for reasons such as cost and weight.

[Problems to be Solved by the Invention] By the way, the upper limit QB of the required boost flow rate QB is automatically determined once the maximum system pressure PMAX of the hydraulic pressure drive circuit is determined. Control flow rate Q of .24. Even when covering the above, it is determined depending on the diameter and cylinder speed of the cylinder provided in the hydraulic control circuits 23 and 24. Therefore, the capacity of the auxiliary pump D
B is the minimum driving rotation speed N, AIN, D, ≧ (Q BMAX + Q c ) / N MI
It is necessary to set it to N. However, when the capacity of the auxiliary pump 20 is fixed in this way, when the auxiliary pump 20 is driven by the engine 13, the discharge flow rate Q increases as the engine speed N increases. increases in proportion to the rotational speed. Therefore, even at a rotational speed of N (>NMIN), the total pressure of the liquid Q from the auxiliary pump 20 is maintained. In order to smoothly discharge the water without causing pressure loss, the filter 21 connected to the discharge port 2Oa side of the auxiliary pump 20 must have a large capacity, and the piping 23 leading to the relief valve 22 must also be thick. This may cause inconveniences such as having to do so. Further, if the excess pressure liquid discharged from the auxiliary pump 20 is simply dropped into the tank through the relief valve 22, there is a lot of energy waste.

The present invention has been made with attention to such problems, and an object of the present invention is to effectively solve these problems.

Means for Solving the Three Problems] In order to achieve the above object, the present invention employs the following configuration.

That is, the hydromechanical transmission of the present invention is equipped with a fixed displacement auxiliary pump driven by a prime mover, and includes a priority control valve that preferentially ensures a constant flow rate on the discharge port side of the auxiliary pump. The present invention is characterized in that the surplus flow rate generated by the priority valve is returned to the suction port side of the auxiliary pump via the ejector.

Further, the hydromechanical transmission includes a fixed displacement auxiliary pump driven by the prime mover, a hydraulic drive circuit to which the auxiliary pump provides a boost flow rate, and a hydraulic control circuit to which the auxiliary pump provides a controlled flow rate. In this case, a first priority valve that preferentially secures a constant flow rate is provided on the discharge port side of the auxiliary pump, and the excess flow rate generated by this priority valve is sucked into the auxiliary pump via an ejector. At the same time, a second priority valve is provided downstream of the first priority valve, and the flow rate secured preferentially by this priority valve is sent to the hydraulic pressure control circuit to eliminate the surplus generated by the priority valve. Preferably, the flow is delivered to a hydraulic drive circuit.

[Function] According to the structure of claim 1, even if the rotational speed of the prime mover increases and the discharge amount increases more than necessary, the priority valve cuts off the surplus flow, so that the target circuit connected downstream is always supplied with excess flow. A sufficient flow rate can be transferred. Therefore, the upper limit of the flow rate is determined, and it becomes easy to make the filters, piping, etc. as small as possible in advance according to the flow rate. Moreover, since the cut surplus flow is returned to the pump suction port via the ejector, the suction port diameter can be smaller than when all the surplus flow is dropped into the tank and the required flow is newly supplied from the suction port. In addition to reducing the load on the prime mover, the ejector effect also improves suction performance, improving pump operating efficiency and making it possible to downsize the auxiliary pump.

Further, according to the structure of claim 2, the required flow rate (boost flow element controlled flow rate) is obtained from the first priority valve by the operation based on the above-mentioned claim 1, and this is obtained from the second priority valve.
The water will flow into the priority valve, and from this point on, the following effects will be obtained. That is, considering the case where the configuration of the present invention is not adopted, when only the minimum required flow rate is taken out from the first priority valve, if the boost flow rate becomes larger than the expected flow rate, , the control flow rate supplied to the hydraulic control circuit will decrease.

The hydraulic pressure control circuit is a part that is involved in important functions such as clutch drive and speed change drive, and if this circuit ceases to function due to insufficient flow, the vehicle etc. will be in an extremely dangerous situation. On the other hand, if the control flow rate is given priority over the boost flow rate as in the present invention, even if the boost flow rate decreases temporarily, it will not suddenly cause a malfunction in the hydraulic drive circuit. Appropriate control can be ensured to keep the system on the fail-safe side.

[Example 1] An example of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows the hydromechanical continuously variable transmission for vehicles according to this embodiment, and the basic configuration and speed change function are explained in the fourth section.
It is similar to that shown in the figure. And auxiliary pump 20
A first priority valve 31 that preferentially secures a constant flow rate QA is provided on the discharge port 2Oa side of the ejector circuit 3.
2 to the suction port 2Ob side of the auxiliary pump 20.

To explain specifically, the priority valve 31
As shown in the figure, a sleeve 31b is inserted into the housing 31a.
A cylindrical spool 31c with a bottom is slidably fitted into the sleeve 31b. An orifice 31d is provided at the bottom of the spool 31c.
The inlet chamber 31e and the outlet chamber 31f communicate with each other via d. A spool 31c and a housing 31 are installed in the outlet chamber 31f.
A spring 31g is installed between the entrance chamber 3
The hydraulic pressure P2 of the outlet chamber 31f and the biasing force of the spring 31g compete with the hydraulic pressure P1 of the outlet chamber 31f to act on the spool 31c. In addition, the housing 31a is provided with a vent 31h at a position where it can communicate with the inlet chamber 31e when the spool 31c moves to the right. Such a structure has the effect of always keeping the pressure before and after the orifice 31d constant, and the flow rate Q flowing into the artificial chamber 31e. The function is to allow a constant flow of itQ A to pass through the outlet chamber 31f regardless of the size of the outlet chamber 31f. q (-Q.-QA) is taken out from the vent 31h.

Then, as shown in FIG. 3, this priority valve 31 is screwed into the discharge port 2Oa of the auxiliary pump 20, and an ejector 32a is provided in the pump suction port 2Ob. 3
The surplus flow rate q flowing out from the first vent 31h is guided through the vent circuit 31 so that it can be ejected into the inside of the pump.

If such a priority valve 31 is provided,
The rotational speed N of the engine 13 increases and the discharge amount Q of the auxiliary pump 20 increases. Even if q increases more than necessary, the priority valve 31 cuts off the surplus flow q, so that the total flow QA required for the target circuit 9, 23, and 24 connected downstream is not exceeded or deficient. It can be transported without any problems. Therefore, it is possible to eliminate the possibility that a flow rate higher than expected will flow, and it becomes easy to make the filter 21, piping of each part, etc. as small as possible in advance according to the flow rate QA.

Moreover, the cut surplus flow q is the pump suction port 2Ob.
Since the flow is returned to the side via the ejector 32a, compared to the case where all the excess flow is dropped into the tank and the necessary flow is newly sucked, the newly sucked flow is only QA q, and as a result, the flow rate of the suction port 20b is The diameter can be made smaller, which leads to a reduction in the load on the engine 13, and the ejector effect improves suction performance, which also improves pump operating efficiency, making it possible to reduce the capacity of the auxiliary pump 20 to its limit. becomes.

Further, in this embodiment, a second priority valve 33 having a similar structure is further provided downstream of the first priority valve 31, and this priority valve 3
The control flow rate Qc that is preferentially ensured in step 3 is sent to the hydraulic pressure control circuit 23.24 of the clutch 11.12 shown in FIG. is supplied to the hydraulic drive circuit 9.

If such a priority valve 33 is provided,
Flow fk flowing in from the first priority valve 31
Even if the required boost flow rate QB temporarily exceeds expectations while Q A is being suppressed to the necessary minimum, the control flow rate Q for the hydraulic pressure control circuits 23 and 24 will be prioritized. As a result, the system can be maintained on the fail-safe side without causing a dangerous situation such as the clutches 11, 12 becoming uncontrollable.

Note that when the present invention is applied to a transmission that supplies fluid discharged from the auxiliary pump 20 only to the hydraulic drive circuit 9, the effects described for the first priority valve 31 can be obtained. . In addition, the configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] According to the fluid mechanical transmission according to claim 1, the flow rate transferred from the priority valve to the target circuit can be suppressed to the necessary minimum, so filters, piping, etc. interposed in the flow path can be reduced. Can be made smaller. Furthermore, since the surplus flow is returned to the pump suction port side together with the ejector effect, the load on the prime mover is reduced and the self-sufficiency of the pump is improved, making it possible to downsize the auxiliary pump. On the other hand, according to the hydromechanical transmission according to claim 2, when the boost flow rate and the control flow rate are covered by the auxiliary pump, the control flow rate is always prioritized and maintained at an appropriate amount, so that it is possible to improve the reliability of control. can.

[Brief explanation of drawings]

1 to 3 show one embodiment of the present invention, FIG. 1 is a schematic partial circuit diagram of a hydromechanical transmission, FIG. 2 is a sectional view of a priority valve, and FIG. 3 is an auxiliary pump. FIG. FIG. 4 is an overall circuit diagram corresponding to FIG. 1 showing a conventional example. 9... Hydraulic pressure drive circuit 13... Prime mover (engine) 20... Auxiliary pump 20a... Discharge port 20b... Suction port 23.24... Hydraulic pressure control circuit 31... First Priority 32a...Ejector 33...Second priority QB...Boost flow rate Qc...Control flow rate

Claims (2)

[Claims] (1) In a hydromechanical transmission equipped with a fixed displacement auxiliary pump driven by a prime mover, a priority valve is provided on the discharge port side of the auxiliary pump to preferentially ensure a constant flow rate, and A fluid mechanical transmission characterized in that surplus flow is returned to the suction port side of the auxiliary pump via an ejector. (2) A fluid machine equipped with a fixed displacement auxiliary pump driven by a prime mover, a hydraulic drive circuit to which the auxiliary pump provides a boost flow rate, and a hydraulic control circuit to which the auxiliary pump provides a controlled flow rate. In the transmission, a first priority valve that preferentially secures a constant flow rate is provided on the discharge port side of the auxiliary pump, and the surplus flow rate generated by this priority valve is returned to the suction port side of the auxiliary pump via an ejector. At the same time, a second priority valve is provided downstream of the first priority valve, and the flow rate secured preferentially by this priority valve is sent to the hydraulic pressure control circuit, and the excess flow rate generated by the priority valve is controlled by the hydraulic pressure. A hydromechanical transmission characterized in that the transmission is configured to feed a drive circuit.